机械毕业设计英文外文翻译300拉臂式垃圾车设计
机械专业毕业设计外文原文
This item was submitted to Loughborough’s Institutional Repository (https:///) by the author and is made available under the following Creative Commons Licence conditions.For the full text of this licence, please go to:/licenses/by-nc-nd/2.5/R A Harris*,R J M Hague and P M DickensRapid Manufacturing Research Group,Loughborough University,Loughborough,UKAbstract:The use of moulds produced by stereolithography(SL)for injection moulding provides a quick route to manufacturing a low volume of parts without expensive hard tooling.However,these parts have been shown to exhibit different material property characteristics than those produced from metal tooling.The aim of the present work is to research methods that would allow SL moulds to produce parts of similar material property characteristics to those from conventional metal tools.This work has identi ed that the different part characteristics are due to differing levels of crystallinity developed in the parts from the comparative mould varieties(SL and metal).These crystallinity differences have been associated with the cooling rates imparted owing to the thermal properties of the mould material.The latter part of this work concerns controlling and manipulating this degree of crystallinity.After a discussion of possible methods,two approaches are taken to modifying the crystalline content of parts produced by SL moulds.One of the approaches is material based,the other concerns the injection moulding process.Differential scanning calorimetry(DSC)is used to quantify the resulting levels of crystallinity in the parts.The results show that by process modi cation it is possible to produce parts by SL moulding that possess a similar crystalline content to those moulded from metal tooling.The use of modi ed materials allows parts created in SL and metal tools to be of a consistent crystalline content.The work concludes that not only are SL moulds capable of producing parts that are more like those from metal moulds but also present some unique opportunities that have been demonstrated to be unachievable in metal moulds.Keywords:stereolithography,rapid tooling,plastic injection moulding,crystallinity,differential scanning calorimetry1BACKGROUND1.1Rapid prototyping and stereolithography Stereolithography(SL)is a rapid prototyping(RP)process. RP processes directly produce a physical geometry from data derived from a three-dimensional representation[i.e. three-dimensional computer aided design(CAD)],and they are characterized by generating the geometry using an additive,layer-by-layer manufacturing sequence,which when initiated runs unattended.SL is the most mature commercial RP process,with its development beginning in the mid-1980s.SL represents one of the most geometrically accurate commercial RP processes,with a minimum feature size of approximately0.1mm possible.SL generates a solid object by selectively curing a photosensitive liquid resin by exposure to UV light provided by laser.The part is generated section by section on a platform that is contained within the bath of the liquid resin.The materials that can be used in the process are restricted to acrylic and epoxy resins. Resins of very different characteristics are available,but they are all essentially variants of epoxy and acrylic(in this work epoxy is used).1.2Plastic injection mouldingPlastic injection moulding is a manufacturing process that broadly consists of forcing a molten polymer into an enclosed shaped cavity to reproduce a de nite form. When the form cools and hardens,it is ejected and the cycle is repeated to produce multiple pieces.1.3Stereolithography tooling for injection moulding The introduction of RP has allowed engineers and designers to generate physical models of required parts very early in the design and development phase.However,the requirements of such prototypes has now progressed beyond the validation ofThe MS was received on13March2003and was accepted after revision forpublication on18July2003.*Corresponding author:Rapid Manufacturing Research Group,WolfsonSchool of Mechanical and Manufacturing Engineering,LoughboroughUniversity,Loughborough,Leicestershire LE113TU,UK.269geometries and on to the physical testing and proving of the parts.For such tests to be conducted,the part must be produced in the material and by the process intended for the production intent part.For injection moulded parts this situation highlights the requirement of a rapid mould making system that can deliver these parts within the time and cost boundaries.Stereolithography allows for rapid,direct generation of tooling inserts that can be used in injection moulding.The accuracy of the SL RP process results in inserts that require few further operations prior to their use in injection mould-ing.Thus,the process provides a quick route to tooling that, depending on geometric complexity and the moulding polymer,can produce550parts[1].The supposed great advantage of the process is that it provides a low volume of parts that are identical to parts that would be produced by conventional hard tooling in a fraction of the time and cost. The key to successful SL tooling is to understand the demands of the mould design and injection moulding parameters,which are very different from those for metal moulds.It has also been demonstrated that appropriate choices in mould design and process variables can reduce the risk of failure in SL tooling[2–4].Various polymers have been successfully moulded by SL injection moulding.These include polyester (PE),polypropylene(PP),polystyrene(PS),polyamide (PA),polycarbonate(PC),polyetheretherketone(PEEK), acrylonitrile–styrene acrylate(ASA)and acrylonitrile–butadiene–styrene(ABS)[5–9].1.4Moulded part characteristicsSL produces parts that consist of epoxy.Thus,the tooling inserts are plastic and possess very different material characteristics compared with their traditional metal counterparts.The present work was initiated by the nding that crystal-line polymer parts produced from SL moulds possess different material properties and characteristics compared with those from a metal tool.The different properties observed in parts produced from SL moulds include:(a)greater strength and stiffness[6,10–12],(b)lower impact strength[6,11,12],(c)greater shrinkage[13].Amorphous polymers exhibited no such differences in physical properties,irrespective of the mould variety.2HYPOTHESISThe exhibition of different moulded part properties negates the greatest advantages of the SL injection moulding tooling process;the moulded parts do not replicate parts that would be produced by conventional hard tooling.The hypothesis of the present work was to acquire an understanding of the mechanisms in SL tooling that induce these different part properties and to develop a modi cation of the process that could change these,allowing the moulded parts to demon-strate characteristics like those produced by conventional means.Should this be possible,SL tooling would be able to provide a truly comparative rapid tooling alternative for low volumes of injection moulded parts.The work is detailed in this paper in two parts.Section3covers the identi cation of the cause of part anomalies,and section4describes the approaches taken for crystallinity control.3IDENTIFICATION OF THE CAUSE OFP ART ANOMALIES3.1IntroductionThe differing part properties that have previously been observed in SL tools are heavily dependent on the amount of crystallinity developed in the part during processing[14]. The amount of crystallinity developed is in uenced by the rate of cooling of the polymer from its molten state[15–18]. It was suspected that part anomalies were due to differing degrees of crystallinity developed in the parts owing to their thermal history during moulding.SL and metal possess very different heat transfer characteristics and when used as mould tool materials this would result in very different rates of part cooling in the injection moulding process. These theories were examined by quantifying the crystal-linity of PA66parts produced in aluminium(AL)and SL moulds and by evaluating the thermal histories experienced by the parts during moulding.3.2Research methodology3.2.1Tool designThe tooling materials to be compared were SL epoxy and aluminium.Aluminium(grade LM24)was chosen as a metal tooling material for comparison as it represents a common tool material choice when a low volume of parts is required on account of the high machining rates possible. The SL moulds were manufactured by a3D Systems SLA350machine,using Vantico5190resin.The moulded specimen consisted of a bar shape with dimensions of 12.7mm by127mm,with a wall thickness of3.2mm. The tooling cavity was gated at one end,measuring 6.4mm in width and3.2mm in depth.No ejection system was utilized in the mould as the parts were simple and easily removed by hand.Illustrations of these moulding cavities are shown in Fig. 1.The mould cavity inserts were contained within a steel bolster which provided alignment of the mould halves,provided material entry into the mould via a tapered sprue bush and protected the inserts from any excessive application of pressure.270R A HARRIS,R J M HAGUE AND P M DICKENS3.2.2Injection moulding parametersPolyamide 66(PA66)was chosen to represent a crystalline polymer in the experiments.This nylon is a widely used polymer in many plastic products.It was important to ensure that the same injection moulding process para-meters were used for both mould types.These parameters were largely dictated by the lower-strength SL mould.The important injection moulding parameters were as follows:1.The injection speed used was 100mm/s.2.The injection pressure was 150bar.3.Upon mould lling,a follow-up pressure of 150bar was held for 1.5s.T wenty mouldings were produced from each mould type.The PA66used was Bergamid A70NAT produced by Poly-One.The injection moulding machine used was a Battenfeld 600/125CDC model with a Unilog 4000control unit.3.2.3Thermal history pro lesThe heat transfer rate imposed by each mould type was established by real-time data acquisition during the mould-ing cycle.Three k-type thermocouples were inserted evenly along the length of the mould cavity .The probe tips were situated 0.5mm below the cavity surface.The tting of these thermocouples is illustrated in Fig.2.The signals were read and interpreted by a instruNet data acquisition system,then analysed and recorded with a HP VEE software program.Prior to polymer injection,each mould was at its ambient temperature of 23¯C.The temperature pro le was plotted over a period of 10min.3.2.4Crystallinity analysisDifferential scanning calorimetry (DSC)was used to measure the degree of crystallinity,(w ),in the samples.DSC is a thermal analysis technique used for direct measurement of the temperatures and heat ow to asample during heating in a controlled atmosphere over a period of time.This technique provides quantitative and qualitative information about physical changes by monitor-ing endothermic or exothermic processes that represent material transitions.The degree of crystallinity is deter-mined by measuring the energy consumed by the melting of the crystalline areas;this is the heat of fusion.A sample heat of fusion is proportional to w [19].The w of the sample can be determined by knowing the heat of fusion for the speci c sample and ratioing this against the heat of fusion required to melt a completely (100per cent)crystallized sample of the material [20].Such a value for PA66is 200J/g [21].Fig.1Illustrations of the different mould cavities employedFig.2Cross-sectional illustration of thermocouple insertionCR YSTALLINITY CONTROL IN P ARTS PRODUCED FROM STEREOLITHOGRAPHY INJECTION MOULD TOOLING 271With both these values it is possible to determine w by the equation [22]w ˆD H D H 100%wherew ˆdegree of crystallinity (%)D H ˆheat of fusionD H 100%ˆheat of fusion for 100per cent crystallization The sample taken from each of the mouldings for DSC analysis was of an average weight of ¹17mg.The test samples were taken from a central region of each moulding,as shown in Fig.3.A sample was taken from each of four different mouldings for each test specimen variety to be examined by DSC,and one scan was run on each.The scan could not be repeated on each sample as the thermal history was erased by the analysis through the heating involved.The samples were extracted from the mouldings by cutting with hand clippers/cutters.By using this method,samples were not subjected to heat from mechanical cutting or sawing.The mouldings selected for analysis represented an even distribu-tion of the mouldings that were produced in sequence from each experimental variety.The mouldings examined were numbers 4,8,12and 16from the set of 20mouldings produced.The apparatus used was a modulated DSC machine produced by TA Instruments,model 2920.The cell atmo-sphere was provided by a refrigerated nitrogen cooling system produced by TA Instruments.The temperature range of the DSC analysis used was 100–320¯C.This operating range was derived by observing the temperatures at which transitions occurred during an analysis in a wider temperature range.This temperature range displayed all transitions of interest while consuming a shorter period of time for each analysis when using a heating rate of 10K/min.3.3Results and discussion 3.3.1Thermal history pro lesThe average temperature pro les experienced in the moulds are shown in Fig. 4.The pro les illustrate the vastly different temperature conditions experienced in the SL and AL moulds.The temperature activity in the AL moulds occurred in a very short period of time owing to the material’s high thermal conductivity .The temperature pro le in the SL mould was more extreme and protracted.Without external assistance (i.e.cooling by compressed air),the SL mould would take 15min to return to its ambient temperature.3.3.2Crystallinity analysisThe DSC results (Table 1,listed as ‘Initial’)have shown that there was more crystallinity developed in the PA66parts produced in SL moulds than in those produced from AL moulds.The DSC results also showed a slight difference in the curve characteristics displayed by the AL and SL mouldings.The AL samples demonstrated an exotherm prior to the heat of fusion (endotherm),while none of the SL samples showed this in the DSC tests.This exothermFig.3DSC sample locationTable 1Per cent of w resultsSample Initial Nuc.agent Temp.mod.AL 120.7524.9921.56AL 221.8424.2921.05AL 321.7424.821.65AL 422.0323.7321.34SL 128.4224.9722.14SL 227.8624.2322.32SL 327.3924.5822.45SL 428.1524.3122.31Fig.4Mould temperature pro les272R A HARRIS,R J M HAGUE AND P M DICKENSwas due to the development of further crystallinity (recrystallization)during heating in the DSC tests.This is illustrated in the examples shown in Figs 5and 6.The absence of any recrystallization activity in the samples from the SL mould indicates that the level of w in the sample was already at its maximum as a result of its prior conditioning.The only injection moulding process variable in the experiments was the different cooling rate of the partFig.5Example of the initial DSC curve from an AL mouldFig.6Example of the initial DSC curve from an SL mouldCR YSTALLINITY CONTROL IN P ARTS PRODUCED FROM STEREOLITHOGRAPHY INJECTION MOULD TOOLING 273which was imposed by the heat transfer properties of the mould,as illustrated by the thermal history pro les. It can be deduced that the difference in w of the parts was due to these different cooling rates.4APPROACHES TAKEN FOR CRYSTALLINITY CONTROL4.1IntroductionSince it has been identi ed that the crystallinity differences in the parts were due to the cooling rate imposed by the inherent heat transfer properties of the mould material,it seems logical that,in order to achieve equal crystallinity,an attempt should be made to make these heat transfer char-acteristics more like those of metal moulds.However, being able to increase the heat transfer properties a thousand times so that they are like those of their aluminium counterpart(thermal conductivity:SLˆ0.2W/m-K, ALˆ200W/m-K)is improbable.The limited possible success for tool-based modi cations led to a completely different approach that would allow the crystallinity of SL moulded parts to resemble those from metal moulds.This work focuses on another aspect of injection moulding—the moulding process rather than the tooling aspect.Two such approaches have been taken in this work.This realm of investigation was inspired by the previous DSC analysis which identi ed the periods of crystal formation and aided an understanding of the morphological activities that occurred during this period.4.2Methodology4.2.1Material-based approachThe rst approach concerns the addition of a nucleating agent to the polymer.The development of crystalline struc-tures is related to the speed at which the polymer is cooled from melt.Faster cooling results in a shorter period of time that the polymer spends in the transitional phase of optimum crystal development.This transitional phase is called crys-tallization.During this phase the polymer ceases to be amorphous(molten)and regains its crystalline structure. Crystal growth depends upon the emergence of a central nucleus to begin the growth pattern of a crystal structure.It is possible to seed the base polymer with foreign particles that provide preformed nuclei prior to the crystallization period by the addition of an additive to the polymer compound known as a nucleating agent.The preformed nuclei that are provided by the addition of a nucleating agent are independent of the base polymer crystallization and are present prior to the phase transition when the base polymer is in its amorphous state(molten).The existence of such independent nuclei allows crystal growth prior to the forma-tion of natural nuclei by homogeneous nucleation.Growth of crystals on such foreign nuclei is known as heterogeneous nucleation.The presence of heterogeneous nuclei facilitates crystal growth which occurs sooner in the cooling period of the polymer than by homogeneous nucleation.The nylon used in the previous experiments was available from the same manufacturer with the addition of a nucleating agent and was used in the work described in this section.The material is Bergamid A65S Natural SO manufactured by PolyOne.The DSC procedure for calculation of w was the same as that used in the previous investigations.4.2.2Process-based approachThe second approach to crystallinity control concerned an investigation of altering the injection process parameters. The initial DSC scans identi ed and quanti ed the tempera-ture regions in which the development of crystalline content was optimum during cooling of the polymer.This was the temperature range in which the heat of fusion occurred,as shown in Fig.7.During heating of the polymer this temperature range also represents the melting phase of the crystalline materials.The transformations that occur during the melting phase involve the breakdown of the bonds between the polymer molecules that form crystalline struc-tures until the polymer is in an amorphous state.This transition is the opposite to that occurring during cooling where the polymer regains its structured crystalline arrange-ment.Thus,the heat of fusion also represents the tempera-ture range of melting.The melt temperature setting of the injection moulding machine used in the initial experiments was270¯C.The DSC work demonstrated that the possible temperature range that could be used was¹235–280¯C(as shown in Fig.7).This is the critical period where w was determined during cooling.The greater crystallinity in the parts from SL moulds was due to a longer duration spent inFig.7Heat of fusion temperature range274R A HARRIS,R J M HAGUE AND P M DICKENSthis period of crystal development owing to the much slower cooling compared with parts from AL moulds.The impetus of this section of the work was to determine if setting a lower melt temperature could effect the w in the part by reducing the amount of time spent in the critical zone of crystal development and thereby reducing the in uence of the cooling rate imposed by the mould.Any attempts to in uence w of a part must be effective during the critical temperature range of crystal development.The range was non-linear and demonstrated a temperature of optimum crystal development (see Fig.7).This is the heat of fusion peak shown in the DSC scan.The peak melt temperature in the previous scans occurred at an average temperature of ¹266¯C.This indicated that the peak period of crystal development occurred ¹4¯C below the polymer melt temperature set by the process in the previous experiments.In an attempt to continue a theme that may provide some correlation with previous tests,the melt temperature in these tests was set 4¯C below the average peak temperature to 262¯C.This is illustrated in Fig.8.The material was Bergamid A70NAT manufactured by PolyOne,the same nylon used in the previous experiments in the earlier work.The procedure for moulding the specimens and morpholo-gical analysis was the same as in the previous experiments.4.3Results and Discussion 4.3.1Material-based approachThe w results of the polymer with the addition of a nucleat-ing agent can be seen in Table 1.The results showed that similar values of crystallinity were developed in parts moulded from SL and AL moulds with the addition of a nucleating agent to the PA66.None of the DSC traces showed recrystallization activity .This indicates that the maximum permissible level of crystallinity existed in allthe samples moulded,regardless of whether they were produced in SL or AL moulds.Another characteristic exposed by the DSC scans was the temperature at which peak crystallinity activity occurred.A comparison of these results with those from the initial experiments showed that the temperature of peak crystallinity activity was higher.The previous work indicated that maximum crystallization activ-ity temperatures occurred within a range of approximately 264–269¯C.The results of the PA66with nucleating agent demonstrated that the same peak period occurs consistently at approximately 274¯C.This indicates that crystallization activity occurred earlier during the cooling phase compared with PA66without the addition of a nucleating agent.4.3.2Process-based approachThe results from the melt temperature modi cation can be seen in Table 1.Although not exactly alike,the results showed that,by lowering the melt temperature setting,it was possible to produce parts from the SL moulds that were much more similar in percentage crystallinity to those from the AL moulds compared with the initial results.The results indicated that the percentage crystallinity of the parts from AL moulds was unaffected by melt temperature setting variation.This may indicate that a minimum level of permissible percentage crystallinity was present in the PA66owing to the extreme rate of rapid cooling in the AL mould.The specimens from both mould types exhibited recrystallization activity prior to the heat of fusion,showing the parts to be of a relative low crystalline content with the development of further crystallinity possible.5CONCLUSIONSThe experimental work details methods for examination and control of morphology relating to the cooling conditions.The results are applicable not only to SL moulds but also to other plastic tooling that has poor thermal conductivity.The techniques described in this work could also be applied to cast epoxy tooling.This work has shown how DSC can be a valuable tool for establishing and quantifying the effects of process variation in injection moulding on the morphology of a part,which is critically in uential on resultant part properties.The level of crystallinity of a part dictates many of the resultant part properties.By demonstrating possible control of part crystallinity ,this work has demonstrated a possible ‘tailoring’of part properties.The process modi cations in this work allow different morphology to be realized without changes to the machine,tool or moulded material (i.e.external cooling control,different polymer,etc).A range of achievable crystallinity would allow certain desirable part properties to be speci ed.It has been demonstrated that it is possible to achieve the upper and lower limits of possible crystallinity in a part by applying differing rates of cooling.Such boundaries indicateFig.8Shift in melt temperature settingsCR YSTALLINITY CONTROL IN P ARTS PRODUCED FROM STEREOLITHOGRAPHY INJECTION MOULD TOOLING 275the possible envelope in which the crystallinity may be varied. The differing extremes of part cooling were caused by the inherent heat transfer properties of the mould materials,AL giving very fast cooling,and SL producing very slow cooling. The use of a nucleating agent provides parts that are of consistent crystallinity irrespective of the cooling rate. However,the morphology of the parts does not necessarily replicate that produced from a metal tool without a nucleating agent,and likewise is not the same as that produced from plastic tools without a nucleating agent.The consistent levels of crystallinity are in-between those previously experienced in P A66without a nucleating agent from SL and AL moulds. Morphology control by melt temperature alteration was indicated by the DSC results which showed the possible range of melt temperature that could be used.As this melting range is the reverse to crystal structure formation, a lowering of the melt temperature allowed a reduction in crystal formation,which resulted in lower crystallinity in the parts from SL moulds.The parts from the AL mould were unaffected by melt temperature variation.The results from the melt temperature modi cation,in combination with the initial results,indicate that a state of minimum permissible crystallinity was induced by the rapid cooling experienced in the AL mould.Parts from the AL moulds demonstrate low crystallinity as the zone in which crystallinity can be in uenced is passed too quickly as a result of the rapid cooling,and the parts obtained achieve the same levels of crystallinity inspite of melt temperature changes.Thus,in these experiments,this crystallinity control technique has shown itself to be inapplicable to aluminium tooling.This demonstrates a case where the thermal properties of plastic tooling are advantageous.The slow cooling of the part that results from the low thermal conductivity of plastic tooling presents a unique opportunity for morphology tailoring which was unattainable in metal tooling. REFERENCES1Hilton,P.D.and Jacobs,P.F.Rapid Tooling:Technologiesand Industrial Applications,2000(Marcel Dekker,New Y ork).2Harris,R.,Hopkinson,N.,Newlyn,H.,Hague,R.and Dickens,yer thickness and draft angle selection for stereolithography injection mould tooling.Int.J.Prod.Res., 2002,40(3),719–729.3Palmer,A.and Colton,J.Design rules for stereolithography injection moulding Inserts.In Proceedings of Society of Plastics Engineers(SPE)Annual Technical Conference (ANTEC),New Y ork,USA,1999,pp.4002–4006.4McDonald,J.A.,Ryall,C.J.and Wimpenny,D.I.Rapid Prototyping Casebook,2001(Professional Engineering Publishing,London).5Luck,T.,Baumann,F.and Baraldi,parison of down-stream techniques for functionaland technical prototypes—fast tooling with RP.In Proceedings of4th European RP Confer-ence,Belgriate,Italy,13–15June1995,pp247–260.6Eschl,J.Experiences with photopolymer inserts for injection moulding.European Stereolithography Users Group Meeting, Florence,Italy,2–5November1997.7Harris,R.A.,Newlyn,H.A.and Dickens,P.M.The selection of mould design variables in direct stereolithography injection mould tooling.Proc.Instn Mech.Engrs,Part B:J.Engineering Manufacture,2002,216(B4),pp.499–505.8Harris,R.A.The injection moulding of PEEK using stereo-lithographymoulds.RAPTIA Newsletter7,April2002,pp.6–7 (Gra sk Pro l,Denmark).9Schulthess,A.,Steinmann,B.and Hofmann,M.Cibatool TM SL epoxy resins and some new applications.In Proceedings of North American Stereolithography Users Group Meeting,San Diego,California,10–14March1996.10Jayanthi,S.,Hokuf,B.,McConnell,R.,Speer,R.J.and Fussell,P.S.Stereolithography injection moulds for direct tooling.Solid Freeform Fabrication Symposium,Austin,Texas, 11–13August1997,pp.275–286.11Dusel,K.-H.Materials for rapid tooling technologies.Society of Manufacturing Engineers Rapid Prototyping and Manufacturing Conference,Dearborn,Michigan,22–24 April1997.12Dawson,K.The effect of rapid tooling on nal product proper-ties.Proceedings of North American Stereolithography Users Group Meeting,San Antonio,Texas,1–5March1998.13Damle,M.,Mehta,S.,Malloy,R.and McCarthy,S.Effect of bre orientation on the mechanical properties of an injection molded part and a stereolithography-insert molded part.Proceedings of Society of Plastics Engineers(SPE)Annual Technical Conference(ANTEC),Atlanta,Georgia,1998,pp.584–588.14Birley,A.W.,Haworth,B.and Batchelor,J.Physics of Plastics:Processing,Properties and Materials Engineering, 1991(Carl Hanser Verlag,Munich).15Turi,E.A.Thermal Characteri z ation of Polymeric Materials, 2nd edition,1997(Academic Press,San Diego).16Brydson,J.A.Plastics Materials,7th edition,1999(Butter-worth-Heinemann,Oxford).17Birley,A.W.,Heath,R.J.and Scott,M.J.Plastics Materials: Properties and Applications,2nd edition,1988(Blackie and Son Limited,New Y ork).18Michaeli,W.Plastics Processing,1995(Carl Hanser Verlag, Munich).19Woodward,A.E.Understanding Polymer Morphology,1995 (Carl Hanser Verlag,Munich).20Hohne,G.,Hemminger,W.and Flammersheim,H.-J.Differ-ential Scanning Calorimetry—An Introduction for Practi-tioners,1996(Springer-V erlag,Berlin).21Thermoplastics Collected Applications Thermal Analysis,1998 (Mettler Toledo GmbH,Switzerland).22Potsch,G.and Michaeli,W.Injection Moulding:An Introduc-tion,1995(Carl Hanser V erlag,Munich).276R A HARRIS,R J M HAGUE AND P M DICKENS。
机械设计外文文献翻译、中英文翻译
机械设计外文文献翻译、中英文翻译unavailable。
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机械设计专业的毕业设计(英文版)
Mechanical EngineeringIntroduction to Mechanical EngineeringMechanical engineering is the branch of engineering that deals with machines and the production of power. It is particularly concerned with forces and motion.History of Mechanical EngineeringThe invention of the steam engine in the latter part of the 18th century, providing a key source of power for the Industrial Revolution, gave an enormous impetus to the development of machinery of all types. As a result a new major classification of engineering, separate from civil engineering and dealing with tools and machines, developed, receiving formal recognition in 1847 in the founding of the Institution of Mechanical Engineers in Birmingham, England.Mechanical engineering has evolved from the practice by the mechanic of an art based largely on trial and error to the application by the professional engineer of the scientific method in research, design, and production.The demand for increased efficiency, in the widest sense, is continually raising the quality of work expected from a mechanical engineer and requiring of him a higher degree of education and training. Not only must machines run more economically but capital Costs also must be minimized.Fields of Mechanical EngineeringDevelopment of machines for the production of goods the high material standard of living in the developed countries owes much to the machinery made possible by mechanical engineering. The mechanical engineer continually invents machines to produce goods and develops machine tools of increasing accuracy and complexity to build the machines.The principal lines of development of machinery have been an increase in the speed of operation to obtain high rates of production, improvement in accuracy to obtain quality and economy in the product, and minimization of operating costs. These three requirements have led to the evolution of complex control systems.The most successful production machinery is that in which the mechanical design of the machine is closely integrated with the control system, whether the latter is mechanical orelectrical in nature. A modern transfer line (conveyor) for the manufacture of automobile engines is a good example of the mechanization of a complex series of manufacturing processes. Developments are in hand to automate production machinery further, using computers to store and process the vast amount of data required for manufacturing a variety of components with a small number of versatile machine tools. One aim is a completely automated machine shop for batch production, operating on a three shift basis but attended by a staff for only one shift per day.Development of machines for the production of power Production machinery presuppose an ample supply of power. The steam engine provided the first practical means of generating power from heat to augment the old sources of power from muscle, wind, and water One of the first challenges to the new profession of mechanical engineering was to increase thermal efficiencies and power; this was done principally by the development of the steam turbine and associated large steam boilers. The 20th century has witnessed a continued rapid growth in the power output of turbines for driving electric generators, together with a steady increase in thermal efficiency and reduction in capital cost per kilowatt of large power stations. Finally, mechanical engineers acquired the resource of nuclear energy, whose application has demanded an exceptional standard of reliability and safety involving the solution of entirely new problems- The control systems of large power plank and complete nuclear power stations have become highly sophisticated networks of electronic, fluidic. Electric, hydraulic, and mechanical components, ail of these involving me province of the mechanical engineer.The mechanical engineer is also responsible for the much smaller internal combustion engines, both reciprocating (gasoline and diesel) and rotary (gas-turbine and Wankel) engines, with their widespread transport applications- In the transportation field generally, in air and space as well as on land and sea. the mechanical engineer has created the equipment and the power plant, collaborating increasingly with the electrical engineer, especially in the development of suitable control systems.Development of military weapons The skills applied to war by the mechanical engineer are similar to those required in civilian applications, though the purpose is to enhance destructive power rather than to raise creative efficiency. The demands of war have channeled huge resources into technical fields, however, and led to developments that have profound benefits in peace. Jet aircraft and nuclear reactors are notable examples.Biaengineering Bioengineering is a relatively new and distinct field of mechanical engineering that includes the provision of machines to replace or augment the functions of the human body and of equipment for use in medical treatment. Artificial limbs have been developed incorporating such lifelike functions as powered motion and touch feedback. Development is rapid in the direction of artificial spare-part surgery. Sophisticated heart-lung machines and similar equipment permit operations of increasing complexity and permit the vital functions in seriously injured or diseased patients to be maintained.Environmental control Some of the earliest efforts of mechanical engineers were aimed at controlling man's environment by pumping water to drain or irrigate land and by ventilating mines. The ubiquitous refrigerating and air-conditioning plants of the modem age are based on a reversed heat engine, where the supply of power "pumps" heat from the cold region to the warmer exterior.Many of the products of mechanical engineering, together with technological developments in other fields, have side effects on the environment and give rise to noise, the pollution of water and air, and the dereliction of land and scenery. The rate of production, both of goods and power, is rising so rapidly that regeneration by natural forces can no longer keep pace. A rapidly growing field for mechanical engineers and others is environmental control, comprising the development of machines and processes that will produce fewer pollutants and of new equipment and techniques that can reduce or remove the pollution already generated.Functions of Mechanical EngineeringFour functions of the mechanical engineering, common to all the fields mentioned, are cited. The first is the understanding of and dealing with the bases of mechanical science. These include dynamics, concerning the relation between forces and motion, such as in vibration; automatic control; thermodynamics, dealing with the relations among the various forms of heat, energy, and power; fluid flow; heat transfer; lubrication; and properties of materials.Second is the sequence of research, design, and development. This function attempts to bring about the changes necessary to meet present and future needs. Such work requires not only a dear understanding of mechanical science and an ability to analyze a complex system into its basic factors, but also the originality to synthesize and invent.Third is production of products and power, which embraces planning, operation, and maintenance. The goal is to produce the maximum value with the minimum investment and cost while maintaining or enhancing longer term viability and reputation of the enterprise or the institution.Fourth is the coordinating functioning of the mechanical engineering, including management, consulting, and, in some cases, marketing.In all of these functions there is a long continuing trend toward the use of scientific instead of traditional or intuitive methods, an aspect of the ever-growing professionalism of mechanical engineering. Operations research, value engineering, and PABLA (problem analysis by logical approach) are typical titles of such new rationalized approaches. Creativity, however, cannot be rationalized. The ability to take the important and unexpected step that opens up new solutions remains in mechanical engineering, as elsewhere, largely a personal and spontaneous characteristic.The Future of Mechanical EngineeringThe number of mechanical engineers continues to grow as rapidly as ever, while the duration and quality of their training increases. There is a growing: awareness, however, among engineers and in the community at large that the exponential increase in populationand living standards is raising formidable problems in pollution of the environment andthe exhaustion of natural resources; this clearly heightens the need for all of the technical professions to consider the long-term social effects of discoveries and developments. -There will be an increasing demand for mechanical engineering skills to provide for man's needs while reducing to a minimum the consumption of scarce raw materials and maintaining a satisfactory environment.Introduction to DesignThe Meaning of DesignTo design is to formulate a plan for the satisfaction of a human need. The particular need to be satisfied may be quite well defined from the beginning. Here are two examples in which needs are well defined:1. How can we obtain large quantities of power cleanly, safely, and economical/ without using fossil fuels and without damaging the surface of the earth?2. This gear shaft is giving trouble; there have been eight failures in the last six weeks. Do something about it.On the other hand, the statement of a particular need to be satisfied may be so nebulous and ill defined that a considerable amount of thought and effort is necessary in ( order to state it dearly as a problem requiring a solution. Here are two examples.-1. Lots of people are killed in airplane accidents.2. In big cities there are too many automobiles on the streets and highways.This second type of design situation is characterized by the fact that neither the need nor the problem to be solved has been identified. Note, too, that the situation may contain not one problem but many.We can classify design, too. For instance, we speak of:1. Clothing design 7. Bridge design2. Interior design 8. Computer-aided design3. Highway design 9. Heating system design.4. Landscape design 10. Machine design5. Building design 11. Engineering design6. Ship design 12. Process designIn fact, there are an endless number, since we can classify design according to the particular article or product or according to the professional field,In contrast to scientific or mathematical problems, design problems have no unique answers; it is absurd, for example, to request the "correct answer" to a design problem, because there is none. In fact, a "good" answer today may well turn out to be a "poor" answer tomorrow, if there is a growth of knowledge during the period or if there are other structural or societal changes.Almost everyone is Involved with design in one way or another, even in dally living, because problems are posed and situations arise which must be solved. A design problem is not a hypothetical problem at all. Design has an authentic purpose—the creation of an end result by taking definite action, or the creation of something having physical reality. In engineering, the word design conveys different meanings to different persons. Some think of a designer as one who employs the drawing board to draft the details of a gear, clutch, or other machine member. Others think of design as the creation of a complex system, such as a communications network. In some areas of engineering the word design has been replaced by other terms such as systems engineering or applied decision theory. But no matter what words are used to describe the design function, in engineering it is still the process in which scientific principles and the tools of engineering—mathematics, computers, graphics, and English—are used to produce a plan which, when carried out, will satisfy a human need.Mechanical Engineering DesignMechanical design means die design of things and systems of a mechanical nature machines, products, structures, devices, and instruments. For the most part, mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences.Mechanical engineering design includes all mechanical design, but it is a broader study, because it includes all the disciplines of mechanical engineering, such as the thermal and fluids sciences, too. Aside from the fundamental sciences that are required, the first studies in mechanical engineering design are in mechanical design.The Phases of DesignThe complete process, from start to finish. The process W begins with a recognition of a need and a decision to do something about it. After much iteration, the process ends with the presentation of the plans for satisfying the need.Design ConsiderationsSometimes the strength required of an element in a system is an important factor in the determination of the geometry and the dimensions of the element. In such a situation we say that strength is an important design consideration. When we use the expression design consideration, we are referring to some characteristic which influences the design of the element or, perhaps, the entire system. Usually quite a number of such characteristics must be considered in a given design situation. Many of the important ones are as follows:1. Strength2. Reliability3. Thermal properties4. Corrosion5. Wear6. Friction7. Processing8. Utility9. Cost10. Safety11. Weight12. Life13. Noise14. Styling15. Shape16. Size17. Flexibility18. Control19. Stiffness20. Surface finish21. Lubrication22. Maintenance23. Volume24. LiabilitySome of these have to do directly with the dimensions, the material, the processing, and the joining of the elements of the system. Other considerations affect the configuration of the total system.To keep the correct perspective, however, it should be observed that in many design situations the important design considerations are such that no calculations or experiments are necessary in order to define an element or system. Students, especially, are often confounded when they run into situations in which it is virtually impossible to make a single calculation and yet an important design decision must be made. These are not extraordinary occurrences at all; they happen every day. Suppose that it is desirable from a sales standpoint—for example, in medical laboratory machinery—to create an impression of great strength and durability. Thicker parts assembled with larger-than-usual oversize bolts can be used to create a rugged-looking machine. Sometimes machines and their parts are designed purely from the standpoint of styling and nothing else. These points are made here so that you will not be misled into believing that there is a rational mathematical approach to every design decision.ManufacturingManufacturing is that enterprise concerned with converting raw material into finished products. There are three distinct phases in manufacturing. These phases are as follows: input, processing, and output.The first phase includes all of the elements necessary to create a marketable product. First, there must be a demand or need for the product. The necessary materials must be (available. Also needed are such resources as energy, time, human knowledge, and human skills. Finally, it takes capital to obtain all of the other resources.Input resources are channeled through the various processes in Phase Two. These are the processes used to convert raw materials into finished products. A design is developed. Based on the design, various types of planning are accomplished. Plans are put into action through various production processes. The various resources and processes are managed to ensure efficiency and productivity. For example, capital resources must be carefully managed to ensure they are used prudently. Finally, the product in question is marketed.The final phase is the output or finished product. Once the finished product has been purchased it must be transported to users. Depending on the nature of the product, installation and ongoing field support may be required. In addition, with some products, particularly those of a highly complex nature, training is necessary.Materials and Processes in ManufacturingEngineering materials covered herein are divided into two broad categories: metals and nonmetals. Metals are subdivided into ferrous metals, nonferrous metals, high-performance alloys, and powdered metals. Nonmetals are subdivided into plastics, elastomers, composites, and ceramics. Production processes covered herein are divided into several broad categories including forming, forging,casting/molding, .heat treatment^ .fastening joining metrology/quality control, and material removal. Each of these is subdivided into several other processes.Stages in the Development of ManufacturingOver the years, manufacturing processes have- gone through four distinct,-although overlapping, stages of development. These stages are as follows: Stage 1 ManualStage 2 MechanizedStage 3 AutomatedStage 4 IntegratedWhen people first began converting raw materials into finished products, they used manual processes. Everything was accomplished using human hands and manually operated tools. This was a very rudimentary form of fully integrated manufacturing. A person identified the need, collected materials, designed a product to meet the need, produced the product, and used it. Everything from start to finish was integrated within the mind of the person who did all the work.Then during the industrial revolution mechanized processes were introduced and humans began using machines to accomplish work previously accomplished manually. This led to work specialization which, in turn, eliminated the integrated aspect of manufacturing. In this stage of development, manufacturing workers might see only that part of an overall manufacturing operation represented by that specific piece on which they worked. There was no way to tell how their efforts fit into the larger picture or their workpiece into the finished product.The next stage in the development of manufacturing processes involved the automation of selected processes. This amounted to computer control of machines and processes. During this phase, islands of automation began to spring up on the shop floor. Each island represented a distinct process or group of processes used in the production of a product. Although these islands of automation did tend to enhance the productivity of the individual processes within the islands, overall productivity often was unchanged. This was because the islands were sandwiched in among other processes that were not automated and were not synchronized with them.The net result was that workpieces would move quickly and efficiently through the automated processes only to back up at manual stations and create bottlenecks. To understand this problem, think of yourself driving from stoplight to stoplight in rush hour traffic Occasionally you find an opening and an: able to rush ahead of the other cars that are creeping along, only to find yourself backed up at the next light. The net effect of your brief moment of speeding ahead is canceled out by the bottleneck at the next stoplight. Better progress would be made if you and the other drivers could synchronize your speed to the changing of the stoplights. Then all cars would move steadily and consistently along and everyone would make better progress in the long run.This need for steady, consistent flow on the shop floor led to the development of integrated manufacturing, a process that is still emerging. In fully integrated settings, machines and processes are computer controlled and integration is accomplished through computers. In the analogy used in the previous paragraph, computers would synchronize the rate of movement of all cars with the changing of the stoplights so that everyone moved steadily and consistently along.The Science of MechanicsThat branch of scientific analysis which deals with motions, time, and forces is called mechanics and is made up of two parts, static’s and dynamics. Static’s deals with the analysis of stationary systems, i. e., those in which time is not a factor, and dynamics deals with systems which change with time.Dynamics is also made up. of tyro major disciplines, first recognized as separate entities by Euler in 1775.The investigation of the motion of a rigid body may be conveniently separated into two parts, the one geometrical, the other mechanical. In the first part, the transference of the body from a given position to any other position must be investigated without respect to the cause of the motion, and must be represented by analytical formulae, which will define the position of each point of the body. This investigation will therefore be referable solely to geometry, or rather to stereotomy.It is clear that by the separation of this part of the question from the other, which belongs properly to Mechanics, the determination of the motion from dynamical principles will be made much easier than if the two parts were undertaken conjointly.These two aspects of dynamics were later recognized as the distinct sciences of kinematics and kinetics, and deal with motion and the forces producing it respectively.The initial problem in the design of a mechanical system therefore understands its kinematics. Kinematics is the study of motion, quite apart from the forces whichproduce that motion. More particularly, kinematics is the study of position, displacement rotation, speed, velocity, and acceleration. The study, say of planetary or orbital motion is also a problem in kinematics.It should be carefully noted in the above quotation that Euler based his separation of dynamics into kinematics and kinetics on the assumption that they should deal with rigid bodies. It is this very important assumption that allows the two to be treated separately. For flexible bodies, the shapes of the bodies themselves, and therefore their motions, depend on the forces exerted on them. In this situation, the study of force and motion must take place simultaneously, thus significantly increasing the complexity of the analysis.Fortunately, although all real machine parts are flexible to some degree, machines are usually designed from relatively rigid materials, keeping part deflections to a minimum. Therefore, it is common practice to assume that deflections are negligible and parts are rigid when analyzing a machine's kinematics performance, and then, after the dynamic analysis when loads are known, to design the parts so that this assumption is justified.。
机械类毕业设计外文翻译范文
机械类毕业设计外文翻译、毕业设计（论文）外译文题目：轴承的摩擦与润滑10 月 15 日外文文献原文：Friction , Lubrication of BearingIn many of the problem thus far , the student has been asked to disregard or neglect friction . Actually , friction is present to some degree whenever two parts are in contact and move on each other. The term friction refers to the resistance of two or more parts to movement.Friction is harmful or valuable depending upon where it occurs. friction is necessary for fastening devices such as screws and rivets which depend upon friction to hold the fastener andthe parts together. Belt drivers, brakes, and tires are additional applications where friction is necessary.The friction of moving parts in a machine is harmful because it reduces the mechanical advantage of the device. The heat produced by friction is lost energy because no work takes place. Also , greater power is required to overcome the increased friction. Heat is destructive in that it causes expansion. Expansion may cause a bearing or sliding surface to fit tighter. If a great enough pressure builds up because made from low temperature materials may melt.There are three types of friction which must be overcome in moving parts: (1)starting, (2)sliding, and(3)rolling. Starting friction is the friction between two solids that tend to resist movement. When two parts are at a state of rest, the surface irregularities of both parts tend to interlock and form a wedging action. T o produce motion in these parts, the wedge-shaped peaks and valleys of the stationary surfaces must be made to slide out and over each other. The rougher the two surfaces, the greater is starting friction resulting from their movement .Since there is usually no fixed pattern between the peaks and valleys of two mating parts, the irregularities do not interlock once the parts are in motion but slide over each other. The friction of the two surfaces is known as sliding friction. As shown in figure ,starting friction is always greater than sliding friction .Rolling friction occurs when roller devces are subjected to tremendous stress which cause the parts to change shape or deform. Under these conditions, the material in front of a roller tends to pile up and forces the object to roll slightly uphill. This changing of shape , known as deformation, causes a movement of molecules. As a result ,heat is produced from the addedenergy required to keep the parts turning and overcome friction.The friction caused by the wedging action of surface irregularities can be overcome partly by the precision machining of the surfaces. However, even these smooth surfaces may require the use of a substance between them to reduce the friction still more. This substance is usually a lubricant which provides a fine, thin oil film. The film keeps the surfaces apart and prevents the cohesive forces of the surfaces from coming in close contact and producing heat .Another way to reduce friction is to use different materials for the bearing surfaces and rotating parts. This explains why bronze bearings, soft alloys, and copper and tin iolite bearings are used with both soft and hardened steel shaft. The iolite bearing is porous. Thus, when the bearing is dipped in oil, capillary action carries the oil through the spaces of the bearing. This type of bearing carries its own lubricant to the points where the pressures are the greatest.Moving parts are lubricated to reduce friction, wear, and heat. The most commonly used lubricants are oils, greases, and graphite compounds. Each lubricant serves a different purpose. The conditions under which two moving surfaces are to work determine the type of lubricant to be used and the system selected for distributing the lubricant.On slow moving parts with a minimum of pressure, an oil groove is usually sufficient to distribute the required quantity of lubricant to the surfaces moving on each other .A second common method of lubrication is the splash system in which parts moving in a reservoir of lubricant pick up sufficient oil which is then distributed to all moving parts during each cycle. This system is used in the crankcase of lawn-mower engines to lubricate the crankshaft, connecting rod ,and parts of the piston.A lubrication system commonly used in industrial plants is the pressure system. In this system, a pump on a machine carries the lubricant to all of the bearing surfaces at a constant rate and quantity.There are numerous other systems of lubrication and a considerable number of lubricants available for any given set of operating conditions. Modern industry pays greater attention to the use of the proper lubricants than at previous time because of the increased speeds, pressures, and operating demands placed on equipment and devices.Although one of the main purposes of lubrication is reduce friction, any substance-liquid , solid , or gaseous-capable of controlling friction and wear between sliding surfaces can be classed as a lubricant.V arieties of lubricationUnlubricated sliding. Metals that have been carefully treated to remove all foreign materials seize and weld to one another when slid together. In the absence of such a high degree of cleanliness, adsorbed gases, water vapor ,oxides, and contaminants reduce frictio9n and the tendency to seize but usually result in severe wear; this is called “unlubricated ”or dry sliding.Fluid-film lubrication. Interposing a fluid film that completely separates the sliding surfaces results in fluid-film lubrication. The fluid may be introduced intentionally as the oil in the main bearing of an automobile, or unintentionally, as in the case of water between a smooth tuber tire and a wet pavement. Although the fluid is usually a liquid such as oil, water, and a wide。
(完整版)机械毕业设计外文翻译7243268
Introduciton of MachiningHave a shape as a processing method, all machining process for the production of the most commonly used and most important method. Machining process is a process generated shape, in this process, Drivers device on the workpiece material to be in the form of chip removal. Although in some occasions, the workpiece under no circumstances, the use of mobile equipment to the processing, However, the majority of the machining is not only supporting the workpiece also supporting tools and equipment to complete.Machining know the process . For casting, forging and machining pressure, every production of a specific shape of the workpiece, even a spare parts, almost the shape of the structure, to a large extent, depend on effective in the form of raw materials. In general, through the use of expensive equipment and without special processing conditions, can be almost any type of raw materials, mechanical processing to convert the raw materials processed into the arbitrary shape of the structure, as long as the external dimensions large enough, it is possible. Because of a production of spare parts, even when the parts and structure of the production batch sizes are suitable for the original casting, Forging or pressure processing to produce, but usually prefer machining.Strict precision and good surface finish, Machining the second purpose is the establishment of the and surface finish possible on the basis of. Many parts, if any other means of production belonging to the large-scale production, Well Machining is a low-tolerance and can meet the requirements of small batch production. Besides, many parts on the production and processing of coarse process to improve its generalshape of the surface. It is only necessary precision and choose only the surface machining. For instance, thread, in addition to mechanical processing, almost no other processing method for processing. Another example is the blacksmith pieces keyhole processing, as well as training to be conducted immediately after the mechanical completion of the processing.Primary Cutting ParametersCutting the work piece and tool based on the basic relationship between the following four elements to fully describe : the tool geometry, cutting speed, feed rate, depth and penetration of a cutting tool.Cutting Tools must be of a suitable material to manufacture, it must be strong, tough, order to effectively processing, and cutting speed must adapt to the level of specific parts -- with knives. Generally, the more the work piece or tool for reciprocating movement and feed rate on each trip through the measurement of inches. Generally, in other conditions, feed rate and cutting speed is inversely proportional to。
机械类毕业设计英文翻译
机械类毕业设计英文翻译(共7页) -本页仅作为预览文档封面，使用时请删除本页-襄樊学院毕业设计(论文)英文翻译题目超声波简介及其应用专业机械设计制造及其自动化班级机制0712姓名刘康学号07116201指导教师职称李梅副教授2011年5月25日Introduction and application of ultrasonicUltrasonic is a mechanical waves which frequency above 20,000 Hz. Ultrasonic inspection commonly used in the frequency of 0. 5~5 MHz. The mechanical waves in the material spread in a certain speed and directions, acoustic impedance different heterogeneous interfaces such as defect is encountered or the bottom surface of the object being tested, will reflections. This reflection phenomenon can be used to ultrasonic testing , most common is pulse echo testing method testing , pulse oscillator issued of voltage plus in probe with pressure electric ceramic or quartz chip made of detection components , probe issued of ultrasonic pulse by sound coupled media such as oil or water , entered material and in which spread , encountered defects , part reflection energy along original way returns probe , probe will change it in electric pulse , by instrument zoom and display in oscilloscope tubes of screen . Depending on where the flaw echo on the screen and amplitude of reflection wave with artificial defects in a reference block rate compared to defect location and approximate dimensions. Apart from Echo method, and use another probe to the other side of the workpiece to accept signal penetration method. When use ultrasonic detection the physical properties of materials, also often take advantage of ultrasonic in sound velocity, attenuation and resonance characteristics of workpiece.Ultrasonic characteristics: 1, ultrasonic beam to focus on a specific direction, along the straight lines in the media, has a good point. 2, ultrasonic wave propagation in the media, attenuation and scattering occurs. 3, ultrasonic wave on the interface of heterogeneous media will make reflection, refraction and mode conversion. Using these features, you can get the defective interface from reflected reflection, so as to achieve the purpose of detecting defects. 4, ultrasonic energy is power than sonic. 5, the ultrasonic loss is very small in solid transmission , probe depth, as occurs in the hetero - interface by ultrasonic phenomena such as reflection, refraction, especially not by gas - solid interface. If the metal air holes, flaws and layer defects such as defects in a gas or a mixture, when defects at the interface of ultrasonic propagation to the metal and on all or part of the reflection. Reflected ultrasonic probe received, handled through circuits inside the instrument, on the screen of the instrument will show a different height and have a certain pitch on waveform characteristics of determine defect depth, location, and shape of the workpiece.Non - destructive testing is not damaged parts or raw materials subject to the status of the work, a means of detection of surfaceand internal quality checks, Nondestructive Testing abbreviationsshort for NDT. Ultrasonic testing is also called ultrasonic,ultrasonic flaw detector, is a type of non - destructive testing. UTis on industrial ultrasonic testing non - destructive testing methods. Ultrasonic enters objects when a defect is encountered, some sound waves produce reflection, transmit and receive an analysis of the reflected wave, exception can accurately gauge the flaws. And is able to display the location and size of internal defects, determinationof material thickness.Advantages of ultrasonic inspection is to detect thickness, high sensitivity, high speed, low cost, is harmless to human body, can be positioned and quantitative defects. Display of ultrasonic detection on defects are not intuitive, testing of technical difficulty, vulnerable to subjective and objective factors, and inspectionresults are not easy to hold, ultrasonic testing requirements on the work surface smooth, requiring experienced inspectors to identify defects types, suitable for the part of considerable thickness inspection, ultrasonic inspection has its limitations.Variety of ultrasonic flaw detector, but most widely applicationof pulse - echo ultrasonic flaw detector. In general, in uniform material, presence of defect will create material discontinuity,this often acoustic impedance of the discontinuity is inconsistent , bythe reflection theorem we know that, in two different acoustic impedance by ultrasonic reflection on the interface of media occurs. Size and interface on both sides of the reflected energy media differences in acoustic impedance and orientation, relative to thesize of the interface. Pulse - echo ultrasonic flaw detector is designed according to this principle. Most of pulse - echo ultrasonic flaw detector is a scan, the so-called A-scan display is the way the display of ultrasonic detection in materials is the horizontal coordinate of transmission time or distance, the ordinate is the amplitude of ultrasonic reflected wave. Such as , in a workpiece in the exists a defects , because defects of exists , between defectsand material formed a different media junction surface, interface of sound impedance different , when launch of ultrasonic encounteredthis interface will occurs reflection , reflection back of energy and probe received it, in monitor screen in the horizontal of must of location on will display out a reflection wave of waveform ,horizontal of this location is defects wave in was detection material in the of depth . The reflected wave height and shape of different because of different defects, reflecting the nature of the defect Now is usually on the measured object, human launch industrial materials such as ultrasound, and then use its reflection, Doppler effect, transmission to get the formation of internal information andprocessing of measured object image. Ultrasonic flaw detector which more general Doppler effect method is using ultrasonic in encountered movement of object Shi occurs of more general Doppler frequency moved effect to came the object of movement direction and speed , characteristics ; transmission rule is by analysis ultrasonic penetrating had was measuring object of changes and came object of internal characteristics of , its application currently also is development stage ; ultrasonic flaw detector here main describes ofis currently application up to of by reflection method to gets object internal characteristics information of method. Reflection method is based on ultrasonic in by different sound impedance organization interface will occurs strong reflection of principle work of , as we all know , When sonic from a media spread to another media in the interface will occurs reflection , and media of differences more large reflection will more large , so we can launch out penetrating force strong , and to line spread of ultrasonic to a object , and on reflection back of ultrasonic for received and under these reflection back of ultrasonic , and range , situation on can judgment out this organization in the contains of various media of size , and distribution situation and various media of comparison differences degree , information which reflection back of ultrasonic of has can reflect out reflection interface away from detection surface of distance , range can reflect out media of size , and comparison differences degree , characteristics , ultrasonic flaw detector to judgment out the was measuring object is has exception . In this process involves many aspects of content, including produce, receive, ultrasonic signal conversion and processing. One method is through the circuit of ultrasonic excitation signals to crystals such as quartz, lithium sulfate, with the piezoelectric effect, making it resulting in ultrasonic vibration ; receives the reflected ultrasonic waves when the piezoelectric crystals, there will be pressure from the reflected sound waves and electrical signals and transferred to the signal processing circuit for a series of processing, observation of ultrasonic flaw detector resulting images for people to judge.Types of image processing can be divided into A type display display, M and B type show, C-type display, such as F-type display. Which A type display is will received to of ultrasonic signal processing into waveform image , under waveform of shape can see was measuring object inside is has exception and defects in there , and has more large , ultrasonic flaw detector main for industrial detection ; M type display is will a section after fai of processing of detection information by time order expand formation a dimension of " space more points movement timing figure " , for observation internal is movement state of object , ultrasonic flaw detector asmovement of organ , and artery vascular; B type display is will side - by - side many section after fai of processing of detection information group synthesis of second dimension of , and reflect out was measuring object internal fault section of " Anatomy image " hospital in using of B Super is with this principle do out of , ultrasonic flaw detector for observation internal is static ofobject ; and c type display , and F type display now with was comparison less . Detection of ultrasonic flaw detector can be very accurate, and more convenient, fast compared to other testing methods, nor harmful to detect objects and actions, so welcomed by the people more and more popular, has a very broad prospects for development. With the further development of electronic technology and software technology, digital ultrasonic flaw detector there are broad development prospects. Believe in the near future, more advanced new generation of digital intelligent ultrasonic flaw detector will gradually replace traditional analog detector, mainly for imagedisplay detector will be widely used in industrial inspection.Ultrasonic characterization of defects is always a difficult problem, still mainly relies on experience and analysis of inspection personnel, and poor accuracy. Development of the modern discipline of artificial intelligence for the realization of instrument automatic defect characterization offers the potential. Application of pattern recognition technology and expert systems, various characteristics of a large number of known defects input sample library, to accept the equipment people experience, and after studying with automatic defect characterization capabilities.超声波简介及其应用超声波是频率高于20千赫的机械波。
机械类毕业设计外文翻译
本科毕业论文(设计)外文翻译学院：机电工程学院专业：机械工程及自动化姓名：高峰指导教师：李延胜2011年 05 月 10日教育部办公厅Failure Analysis，Dimensional Determination And Analysis，Applications Of Cams INTRODUCTIONIt is absolutely essential that a design engineer know how and why parts fail so that reliable machines that require minimum maintenance can be designed．Sometimes a failure can be serious，such as when a tire blows out on an automobile traveling at high speed．On the other hand，a failure may be no more than a nuisance．An example is the loosening of the radiator hose in an automobile cooling system．The consequence of this latter failure is usually the loss of some radiator coolant，a condition that is readily detected and corrected．The type of load a part absorbs is just as significant as the magnitude．Generally speaking，dynamic loads with direction reversals cause greater difficulty than static loads，and therefore，fatigue strength must be considered．Another concern is whether the material is ductile or brittle．For example，brittle materials are considered to be unacceptable where fatigue is involved．Many people mistakingly interpret the word failure to mean the actualbreakage of a part．However，a design engineer must consider a broader understanding of what appreciable deformation occurs．A ductile material，however will deform a large amount prior to rupture．Excessive deformation，without fracture，may cause a machine to fail because the deformed part interferes with a moving second part．Therefore，a part fails(even if it has not physically broken)whenever it no longer fulfills its required function．Sometimes failure may be due to abnormal friction or vibration between two mating parts．Failure also may be due to a phenomenon called creep，which is the plastic flow of a material under load at elevated temperatures．In addition，the actual shape of a part may be responsible for failure．For example，stress concentrations due to sudden changes in contour must be taken into account．Evaluation of stress considerations is especially important when there are dynamic loads with direction reversals and the material is not very ductile． In general，the design engineer must consider all possible modes of failure，which include the following．——Stress——Deformation——Wear——Corrosion——Vibration——Environmental damage——Loosening of fastening devicesThe part sizes and shapes selected also must take into account many dimensional factors that produce external load effects，such as geometric discontinuities，residual stresses due to forming of desired contours，and the application of interference fit joints．Cams are among the most versatile mechanisms available．A cam is a simple two-member device．The input member is the cam itself，while the output member is called the follower．Through the use of cams，a simple input motion can be modified into almost any conceivable output motion that is desired．Some of the common applications of cams are ——Camshaft and distributor shaft of automotive engine ——Production machine tools——Automatic record players——Printing machines——Automatic washing machines——Automatic dishwashersThe contour of high-speed cams (cam speed in excess of 1000 rpm) must be determined mathematically．However，the vast majority of cams operate at low speeds(less than 500 rpm) or medium-speed cams can be determined graphically using a large-scale layout．In general，the greater the cam speed and output load，the greater must be the precision with which the cam contour is machined．DESIGN PROPERTIES OF MATERIALSThe following design properties of materials are defined as they relate to the tensile test．FigureStatic Strength．The strength of a part is the maximum stress that the part can sustain without losing its ability to perform its required function．Thus the static strength may be considered to be approximately equal to the proportional limit，since no plastic deformation takes place and no damage theoretically is done to the material．Stiffness．Stiffness is the deformation-resisting property of a material．The slope of the modulus line and，hence，the modulus of elasticity are measures of the stiffness of a material．Resilience．Resilience is the property of a material that permits it to absorb energy without permanent deformation．The amount of energy absorbed is represented by the area underneath the stress-strain diagram within the elastic region．Toughness．Resilience and toughness are similar properties．However，toughness is the ability to absorb energy without rupture．Thus toughness is represented by the total area underneath the stress-strain diagram，as depicted in Figure 2．8b．Obviously，the toughness and resilience of brittle materials are very low and are approximately equal．Brittleness． A brittle material is one that ruptures before any appreciable plastic deformation takes place．Brittle materials are generally considered undesirable for machine components because they are unable to yield locally at locations of high stress because of geometric stress raisers such as shoulders，holes，notches，or keyways．Ductility． A ductility material exhibits a large amount of plastic deformation prior to rupture．Ductility is measured by the percent of areaand percent elongation of a part loaded to rupture．A 5%elongation at rupture is considered to be the dividing line between ductile and brittle materials．Malleability．M alleability is essentially a measure of the compressive ductility of a material and，as such，is an important characteristic of metals that are to be rolled into sheets．Hardness．The hardness of a material is its ability to resist indentation or scratching．Generally speaking，the harder a material，the more brittle it is and，hence，the less resilient．Also，the ultimate strength of a material is roughly proportional to its hardness．Machinability．Machinability is a measure of the relative ease with which a material can be machined．In general，the harder the material，the more difficult it is to machine．FigureCOMPRESSION AND SHEAR STATIC STRENGTHIn addition to the tensile tests，there are other types of static load testing that provide valuable information．Compression Testing．M ost ductile materials have approximately the same properties in compression as in tension．The ultimate strength，however，can not be evaluated for compression．As a ductile specimen flows plastically in compression，the material bulges out，but there is no physical rupture as is the case in tension．Therefore，a ductile material fails in compression as a result of deformation，not stress．Shear Testing．Shafts，bolts，rivets，and welds are located in such a way that shear stresses are produced．A plot of the tensile test．The ultimate shearing strength is defined as the stress at which failure occurs．The ultimate strength in shear，however，does not equal the ultimate strength in tension．For example，in the case of steel，the ultimate shear strength is approximately 75% of the ultimate strength in tension．This difference must be taken into account when shear stresses are encountered in machine components．DYNAMIC LOADSAn applied force that does not vary in any manner is called a static or steady load．It is also common practice to consider applied forces that seldom vary to be static loads．The force that is gradually applied during a tensile test is therefore a static load．On the other hand，forces that vary frequently in magnitude and direction are called dynamic loads．Dynamic loads can be subdivided to the following three categories．Varying Load．W ith varying loads，the magnitude changes，but the direction does not．For example，the load may produce high and low tensile stresses but no compressive stresses．Reversing Load．In this case，both the magnitude and direction change．These load reversals produce alternately varying tensile and compressive stresses that are commonly referred to as stress reversals．Shock Load．This type of load is due to impact．One example is an elevator dropping on a nest of springs at the bottom of a chute．The resulting maximum spring force can be many times greater than the weight of the elevator，The same type of shock load occurs in automobile springs when a tire hits a bump or hole in the road．FATIGUE FAILURE-THE ENDURANCE LIMIT DIAGRAMThe test specimen in Figure ．，after a given number of stress reversals will experience a crack at the outer surface where the stress is greatest．The initial crack starts where the stress exceeds the strength of the grain on which it acts．This is usually where there is a small surface defect，such as a material flaw or a tiny scratch．As the number of cycles increases，the initial crack begins to propagate into a continuous series of cracks all around the periphery of the shaft．The conception of the initial crack is itself a stress concentration that accelerates the crack propagation phenomenon．Once the entire periphery becomes cracked，the cracks start to move toward the center of the shaft．Finally，when the remaining solid inner area becomes small enough，the stress exceeds the ultimate strength and the shaft suddenly breaks．Inspection of the break reveals a very interesting pattern，as shown in Figure ．The outer annular area is relatively smooth because mating cracked surfaces had rubbed against each other．However，the center portion is rough，indicating a sudden rupture similar to that experienced with the fracture of brittle materials．This brings out an interesting fact．When actual machine parts fail as a result of static loads，they normally deform appreciably because of the ductility of the material．FigureThus many static failures can be avoided by making frequent visual observations and replacing all deformed parts．However，fatigue failures give to warning．Fatigue fail mated that over 90% of broken automobile parts have failed through fatigue．The fatigue strength of a material is its ability to resist the propagation of cracks under stress reversals．Endurance limit is a parameter used to measure the fatigue strength of a material．By definition，the endurance limit is the stress value below which an infinite number of cycles will not cause failure．Let us return our attention to the fatigue testing machine in Figure ．The test is run as follows：A small weight is inserted and the motor is turned on．At failure of the test specimen，the counter registers the number of cycles N，and the corresponding maximum bending stress is calculated from Equation ．The broken specimen is then replaced by an identical one，and an additional weight is inserted to increase the load．A new value of stress is calculated，and the procedure is repeated until failure requires only one complete cycle．A plot is then made of stress versus number of cycles to failure．Figure shows the plot，which is called the endurance limit or S-N curve．Since it would take forever to achieve an infinite number of cycles，1 million cycles is used as a reference．Hence the endurance limit can be found from Figure by noting that it is the stress level below which the material can sustain 1 million cycles without failure．The relationship depicted in Figure is typical for steel，because the curve becomes horizontal as N approaches a very large number．Thus the endurance limit equals the stress level where the curve approaches a horizontal tangent．Owing to the large number of cycles involved，N is usually plotted on a logarithmic scale，as shown in Figure ．When this is done，the endurance limit value can be readily detected by the horizontal straight line．For steel，the endurance limit equals approximately 50% of the ultimate strength．However，if the surface finish is not of polished equality，the value of the endurance limit will be lower．For example，for steel parts with a machined surface finish of 63 microinches ( μin．)，the percentage drops to about 40%．For rough surfaces (300μin．or greater)，the percentage may be as low as 25%．The most common type of fatigue is that due to bending．The next mostfrequent is torsion failure，whereas fatigue due to axial loads occurs very seldom．Spring materials are usually tested by applying variable shear stresses that alternate from zero to a maximum value，simulating the actual stress patterns．In the case of some nonferrous metals，the fatigue curve does not level off as the number of cycles becomes very large．This continuing toward zero stress means that a large number of stress reversals will cause failure regardless of how small the value of stress is．Such a material is said to have no endurance limit．For most nonferrous metals having an endurance limit，the value is about 25% of the ultimate strength．EFFECTS OF TEMPERATURE ON YIELD STRENGTH AND MODULUS OF ELASTICITY Generally speaking，when stating that a material possesses specified values of properties such as modulus of elasticity and yield strength，it is implied that these values exist at room temperature．At low or elevated temperatures，the properties of materials may be drastically different．For example，many metals are more brittle at low temperatures．In addition，the modulus of elasticity and yield strength deteriorate as the temperature increases．Figure shows that the yield strength for mild steel is reduced by about 70% in going from room temperature to 1000o F．Figure shows the reduction in the modulus of elasticity E for mild steel as the temperature increases．As can be seen from the graph，a 30% reduction in modulus of elasticity occurs in going from room temperature to 1000o F．In this figure，we also can see that a part loaded below the proportional limit at room temperature can be permanently deformed under the same load at elevated temperatures．FigureCREEP: A PLASTIC PHENOMENONTemperature effects bring us to a phenomenon called creep，which is the increasing plastic deformation of a part under constant load as a function of time．Creep also occurs at room temperature，but the process is so slow that it rarely becomes significant during the expected life of the temperature is raised to 300o C or more，the increasing plastic deformation can become significant within a relatively short period of time．The creep strength of a material is its ability to resist creep，and creep strength data can be obtained by conducting long-time creep tests simulating actual part operating conditions．During the test，theplastic strain is monitored for given material at specified temperatures．Since creep is a plastic deformation phenomenon，the dimensions of a part experiencing creep are permanently altered．Thus，if a part operates with tight clearances，the design engineer must accurately predict the amount of creep that will occur during the life of the machine．Otherwise，problems such binding or interference can occur．Creep also can be a problem in the case where bolts are used to clamp tow parts together at elevated temperatures．The bolts，under tension，will creep as a function of time．Since the deformation is plastic，loss of clamping force will result in an undesirable loosening of the bolted joint．The extent of this particular phenomenon，called relaxation，can be determined by running appropriate creep strength tests．Figure shows typical creep curves for three samples of a mild steel part under a constant tensile load．Notice that for the high-temperature case the creep tends to accelerate until the part fails．The time line in the graph (the x-axis) may represent a period of 10 years，the anticipated life of the product．FigureSUMMARYThe machine designer must understand the purpose of the static tensile strength test．This test determines a number of mechanical properties of metals that are used in design equations．Such terms as modulus of elasticity，proportional limit，yield strength，ultimate strength，resilience，and ductility define properties that can be determined from the tensile test．Dynamic loads are those which vary in magnitude and direction and may require an investigation of the machine part’s resistance to failure．Stress reversals may require that the allowable design stress be based on the endurance limit of the material rather than on the yield strength or ultimate strength．Stress concentration occurs at locations where a machine part changes size，such as a hole in a flat plate or a sudden change in width of a flat plate or a groove or fillet on a circular shaft．Note that for the case of a hole in a flat or bar，the value of the maximum stress becomes much larger in relation to the average stress as the size of the hole decreases．Methods of reducing the effect of stress concentration usuallyinvolve making the shape change more gradual．Machine parts are designed to operate at some allowable stress below the yield strength or ultimate strength．This approach is used to take care of such unknown factors as material property variations and residual stresses produced during manufacture and the fact that the equations used may be approximate rather that exact．The factor of safety is applied to the yield strength or the ultimate strength to determine the allowable stress．Temperature can affect the mechanical properties of metals．Increases in temperature may cause a metal to expand and creep and may reduce its yield strength and its modulus of elasticity．If most metals are not allowed to expand or contract with a change in temperature，then stresses are set up that may be added to the stresses from the load．This phenomenon is useful in assembling parts by means of interference fits．A hub or ring has an inside diameter slightly smaller than the mating shaft or post．The hub is then heated so that it expands enough to slip over the shaft．When it cools，it exerts a pressure on the shaft resulting in a strong frictional force that prevents loosening．TYPES OF CAM CONFIGURATIONSPlate Cams．This type of cam is the most popular type because it is easy to design and manufacture．Figure 6．1 shows a plate cam．Notice that the follower moves perpendicular to the axis of rotation of the camshaft．All cams operate on the principle that no two objects can occupy the same space at the same time．Thus，as the cam rotates ( in this case，counterclockwise )，the follower must either move upward or bind inside the guide．We will focus our attention on the prevention of binding and attainment of the desired output follower motion．The spring is required to maintain contact between the roller of the follower and the cam contour when the follower is moving downward．The roller is used to reduce friction and hence wear at the contact surface．For each revolution of the cam，the follower moves through two strokes-bottom dead center to top dead center (BDC to TDC) and TDC to BDC．Figure illustrates a plate cam with a pointed follower．Complex motions can be produced with this type of follower because the point can follow precisely any sudden changes in cam contour．However，this design is limited to applications in which the loads are very light；otherwisethe contact point of both members will wear prematurely，with subsequent failure．Two additional variations of the plate cam are the pivoted follower and the offset sliding follower，which are illustrated in Figure ．A pivoted follower is used when rotary output motion is desired．Referring to the offset follower，note that the amount of offset used depends on such parameters as pressure angle and cam profile flatness，which will be covered later．A follower that has no offset is called an in-line follower．Figure 6..3Translation Cams．Figure depicts a translation cam．The follower slides up and down as the cam translates motion in the horizontal direction．Note that a pivoted follower can be used as well as a sliding-type follower．This type of action is used in certain production machines in which the pattern of the product is used as the cam．A variation on this design would be a three-dimensional cam that rotates as well as translates．For example，a hand-constructed rifle stock is placed in a special lathe．This stock is the pattern，and it performs the function of a cam．As it rotates and translates，the follower controls a tool bit that machines the production stock from a block of wood．FigurePositive-Motion Cams．In the foregoing cam designs，the contact between the cam and the follower is ensured by the action of the spring forces during the return stroke．However，in high-speed cams，the spring force required to maintain contact may become excessive when added to the dynamic forces generated as a result of accelerations．This situation can result in unacceptably large stress at the contact surface，which in turn can result in premature wear．Positive-motion cams require no spring because the follower is forced to contact the cam in two directions．Thereare four basic types of positive-motion cams: the cylindrical cam，the grooved-plate cam ( also called a face cam ) ，the matched-plate cam，and the scotch yoke cam．Cylindrical Cam．The cylindrical cam shown in Figure produces reciprocating follower motion，whereas the one shown in Figure illustrates the application of a pivoted follower．The cam groove can be designed such that several camshaft revolutions are required to produce one complete follower cycle．Grooved-plate Cam．In Figure we see a matched-plate cam with a pivoted follower，although the design also can be used with a translation follower．Cams E and F rotate together about the camshaft B．Cam E is always in contact with roller C，while cam F maintains contact with roller D．Rollers C and D are mounted on a bell-crank lever，which is the follower oscillating about point A．Cam E is designed to provide the desired motion of roller C，while cam F provides the desired motion of roller D．Scotch Yoke Cam．This type of cam，which is depicted in Figure ，consists of a circular cam mounted eccentrically on its camshaft．The stroke of the follower equals two times the eccentricity e of the cam．This cam produces simple harmonic motion with no dwell times．Refer to Section for further discussion．CAM TERMINOLOGYBefore we become involved with the design of cams，it is desirable to know the various terms used to identify important cam design parameters．The following terms refer to Figure ．The descriptions will be more understandable if you visualize the cam as stationary and the follower as moving around the cam．Trace Point．The end point of a knife-edge follower or the center of the roller of a roller-type follower．Cam Contour．The actual shape of the cam．Base Circle．The smallest circle that can be drawn tangent to the cam contour．Its center is also the center of the camshaft．The smallest radial size of the cam stars at the base circle．Pitch Curve．The path of the trace point，assuming the cam is stationary and the follower rotates about the cam．Prime Circle．The smallest circle that can be drawn tangent to the pitch curve．Its center is also the center of the camshaft．Pressure Angle．The angle between the direction of motion of the follower and the normal to the pitch curve at the point where the center of the roller lies．Cam Profile．Same as cam contour．BDC．Bottom Dead Center，the position of the follower at its closest point to the cam hub．Stroke．The displacement of the follower in its travel between BDC and TDC．Rise．The displacement of the follower as it travels from BDC to TDC．Return．The displacement of the follower as it travels from TDC or BDC．Ewell．The action of the follower when it remains at a constant distance from the cam hub while the cam turns．A clearer understanding of the significance of the pressure angle can be gained by referring to Figure ．Here FTis the total force acting on the roller．It must be normal to the surfaces at the contact point．Its direction is obviously not parallel to the direction of motion of the follower．Instead，it is indicated by the angle α，the pressure angle，measured from the line representing the direction of motion of thefollower．Therefore，the force FT has a horizontal component FHand avertical component FV．The vertical component is the one that drives thefollower upward and，therefore，neglecting guide friction，equals thefollower Fload．The horizontal component has no useful purpose but it is unavoidable．In fact，it attempts to bend the follower about its guide．This can damage the follower or cause it to bind inside its guide．Obviously，we want the pressure angle to be as possible to minimize the side thrustFH．A practical rule of thumb is to design the cam contour so that the pressure angle does not exceed 30o．The pressure angle，in general，depends on the following four parameters:——Size of base circle——Amount of offset of follower——Size of roller——Flatness of cam contour ( which depends on follower stroke and type of follower motion used )Some of the preceding parameters cannot be changed without altering the cam requirements，such as space limitations．After we have learned how to design a cam，we will discuss the various methods available to reducethe pressure angle．故障的分析、尺寸的决定以及凸轮的分析和应用前言介绍：作为一名设计工程师有必要知道零件如何发生和为什么会发生故障，以便通过进行最低限度的维修以保证机器的可靠性。
机械毕设外文翻译
Switched Reluctance Motors Drive for the Electrical Traction in Shearer Abstract—the paper presented the double Switched Reluctance motors parallel drive system for the electrical traction in shearer. The system components, such as the Switched Reluctance motor, the main circuit of the power converter and the controller, were described. The control strategies of the closed-loop rotor speed control with PI algorithm and balancing the distribution of the loads with fuzzy logic algorithm were given. The tests results were also presented. It is shown that the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 1 and in the Switched Reluctance motor 2 is within 10%.Keywords- switched reluctance; motor control; shearer; coalmine; electrical drive.I. INTRODUCTIONThe underground surroundings of the coal mines are very execrable. One side, it is the moist, high dust and inflammable surroundings. On the other side, the space of roadway is limited since it is necessary to save the investment of exploiting coal mines so that it is difficult to maintain the equipments. In the modern coal mines, the automatization equipments could be used widely. The faults of the automatization equipments could affect the production and the benefit of the coal mines. The shearer is the mining equipment that coal could be cut from the coal wall. The traditional shearer was driven by the hydrostatic transmission system. The fault ratio of the hydrostatic transmission system is high since the fluid in hydrostatic transmission system could be polluted easily. The faults of the hydrostatic transmission system could affect the production and the benefit of the coal mines directly. The fault ratio of the motor drive system is lower than that of the hydrostatic transmission system, but it is difficult to cool the motor drive system in coal mines since the motor drive system should be installed within the flameproof enclosure for safety protection. The motor drive system is also one of the pivotal parts in the automatization equipments. The development of the novel types of the motor drive system had been attached importance to by the coal mines. The Switched Reluctance motor drive could become the main equipments for adjustable speed electrical drive system in coal mines [1],because it has the high operational reliability and the fault tolerant ability [2]. The Switched Reluctance motor drive made up of the double-salient pole Switched Reluctance motor, the unipolar power converter and the controller is firm in the motor and in the power converter. There is no brush structure in the motor and no fault of am bipolar power converter in the power converter [3][4]. The Switched Reluctance motor drive could be operated at the condition of lacked phases fault depended on the independence of each phase in the motor and the power converter [5]. There is no winding in the rotor so that there is no copper loss in the loss and there is only little iron loss in the rotor. It is easy to cool the motor since it is not necessary to cool the rotor. The shearer driven by theSwitched Reluctance motor drive had been developed. The paper presented the developed prototype.II. SYSTEM COMPONENTSThe developed SwitchedReluctance motors drive for the electrical traction in shearer is a type of the double Switched Reluctance motors parallel drive system. The system is made up of two Switched Reluctance motors; a control box installed the power converter and the controller. The adopted two Switched Reluctance motors are all three-phase 12/8 structure Switched Reluctance motor, which were shown in Figure 1. Figure1. Photograph of the two three-phase .12/8 structure Switched Reluctance motorThe two Switched Reluctance motors were packing by the explosion-proof enclosure, respectively. The rated output power of one motor is 40 KW at the rotor speed 1155 r/min, and the adjustable speed range is from 100 r/min to 1500r/min.The power converter consists of two three-phase asymmetric bridge power converter in parallel. The IGBTs were used as the main switches. Three-phase 380V AC power source was certificated and supplied to the power converter. The maincircuit of the power converter was shown in Figure 2.In the controller, there were the rotor position detection circuit, the commutation circuit, the current and voltage protection circuit, the main switches’ gate driver circuit and the digital controller for rotor speed closed-loop and balancing the distribution of the loads.III. CONTROL STRATEGYThe two Switched Reluctance motor could all drive the shearer by the transmission outfit in the same traction guide way so that the rotor speed of the two Switched Reluctance motors could be synchronized.The closed-loop rotor speed control of the double Switched Reluctance motors parallel drive system could be implemented by PI algorithm. In the Switched Reluctance motor 1, the triggered signals of the main switches in the power converter are modulated by PWM signal, the comparison of the given rotor speed and the practical rotor speed are made and the duty ratio of PWM signal are regulated as follows,1()11()1(1)1()e=()g fk i k p k k k k k n n D k e K e e D D D ---∆=+-=+∆where, ng is the given rotor speed, nf is the practical rotorspeed, e is the difference of the rotor speed, 1()k D ∆is the increment of the dutyratio of PWM signal of the Switched Reluctance motor 1 at k time, Ki is the integral coefficient, Kp is the proportion coefficient, ek is the difference of the rotor speed at k time, ek-1 is the difference of the rotor speed at k-1 time, D1(k) is the duty ratio of PWM signal of the Switched Reluctance motor 1 at k time, and D1(k-1) is the duty ratio of PWM signal of the Switched Reluctance motor 1 at k-1 time.The output power of the Switched Reluctance motordrive system is approximately in proportion to theaverage DC supplied current of the power converter asfollows, 2in p I ∝ where, P2 is the output power of the Switched Reluctance motor drive system, Iin is the average DC supplied current of the power converter.In the Switched Reluctance motor 2, the triggered signals of the main switches in the power converter are also modulated by PWM signal. The balancing the distribution of the loads between the two Switched Reluctance motors could be implemented by fuzzy logic algorithm. In the fuzzy logic regulator, there are two input control parameters, one is the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, and the other is the variation of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors. The output control parameter is the increment of the duty ratio of the PWM signal of the Switched Reluctance motor 2. The block diagram of the double Switched Reluctance motors parallel drive system for the electrical traction in shearer was shown in Figure 3.The deviation of the average DC supplied current ofthe power converter between the two Switched Reluctance motors at the moment of ti is12i in in e I I =-:.1i i i e e e -=- where, ei-1 is the deviation of the average DC suppliedcurrent of the power converter between the two SwitchedReluctance motors at the moment of ti-1. The duty ratio of the PWM signal of the Switched Reluctance motor 2 at the moment of ti is2()2(1)2()i i i D D D -=+∆where, 2()i D ∆ is the increment of the duty ratio of the PWM signal of theSwitched Reluctance motor 2 at the moment of ti and D2(i-1) is the duty ratio of the PWM signal of the Switched Reluctance motor 2 at the moment of ti-1.The fuzzy logic algorithm could be expressed asfollows,if ~~if E i E = and ~~EC j E C = then U~ ~~U U U =i = 1,2,…, m, j = 1,2, …,nwhere, E~ is the fuzzy set of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, E~C is the fuzzy set of the variation of the deviation of the average DC supplied current of the power converter between the two Switched Reluctance motors, and U~ is the fuzzy set of the increment of the duty ratio of the PWM signal of the Switched Reluctance motor 2.The continuous deviation of the average DC supplied current of the powerconverter between the two Switched Reluctance motors could be changed into the discrete amount at the interval [-5, +5], based on the equations as follows,[]10220e i e e INT K e K ==The discrete increment of the duty ratio of PWM signal of the Switched Reluctance motor 2 at the interval [-5, +5] could be changed into the continuous amount at the interval [-1.0%, +1.0%], based on the equations as follows,12()[]100.02i D D D INT K D K -==There is a decision forms of the fuzzy logic algorithm based on the above principles, which was stored in the programme storage cell of the controller.While the difference of the distribution of the loads between the two Switched Reluctance motors could be got, the duty ratio of PWM signal of the Switched Reluctance motor 2 will be regulated based on the decision forms of the fuzzy logic algorithm and the distribution of the loads between the two Switched Reluctance motors could be balanced.IV. TESTED RESULTSThe developed double Switched Reluctance motors parallel drive system prototype had been tested experimentally. Table I gives the tests results, where 1σis the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 1, 2σis the relative deviation of the average DC supplied current of the power converter in the Switched Reluctance motor 2, and,1211122100%2in in in in in I I I I I σ+-=⨯+ 1222122100%2in in in in in I I I σ+-=⨯It is shown that the relative deviation of the average DC supplied current of the power converter in the SwitchedReluctance motor 1 and in the Switched Reluctance motor2 is within 10%V. CONCLUSIONThe paper presented the double Switched Reluctance motors parallel drive system for the electrical traction in shearer. The novel type of the shearer in coal mines driven by the Switched Reluctance motors drive system contributes to reduce the fault ratio of the shearer, enhance the operational reliability of the shearer and increase the benefit of the coal mines directly. The drive type of the double Switched Reluctance motors parallel drive system could also contribute to enhance the operational reliability compared with the drive type of the single Switched Reluctance motor drive system.中文翻译：关磁阻电动机驱动电牵引采煤机摘要-本文介绍了双开关磁阻电动机并联传动系统控制驱动电牵引采煤机。
工业机器人毕业设计外文翻译
外文资料：INDUSTRIAL ROBOTSMechatronicsThe success of industries in manufacturing and selling goods in a world market increasingly depends upon an ability to integrate electronics and computing technologies into a wide range of primarily mechanical products and processes. The performance of many current products-cars, washing machines, robots or machine tools-and their manufacture depend on the capacity of industry to exploit developments in technology and to introduce them at the design stag into both products and manufacturing processes. The results so that the whole industrial system to produce a cheaper and easier than in the past, more reliable, more powerful manufacturing technology, this intense competition, leading to the original electronic engineering and mechanical engineering have been gradually difference among the various disciplines with engineering design replaced with the mutual penetration, resulting in a mechanical and electrical integration, or mechatronics.In this competitive environment, the success of products and technologies are those that effectively combine the electronic and mechanical products, but not the main reason is the absence of a successful application of electronic technology. General product innovation in machine-building industry, often starting from the mechanical hardware design, but in order to achieve vision, from the initial stages of the design process must take full account of electronic technology, control engineering and computer technology. Research from the machinery and electronics to engineering design, the key is through the mechanics and electronics hidden boundaries, put them together, it is understood today the key to this transformation took place.To be successful, early in the design of the study need to establish the concept of mechatronics, when the specific program has not yet formed, so there is choice. In this way, design engineers, especially mechanical design engineers will be able to make a decision too quickly to avoid falling into the stereotypes and reduce productivity.Fully study the market trend, we will find electromechanical integration with a design, will lead to a revival of the field, such as high-speed textile machines, measurement and measurement systems, and automatic test equipment, integrated circuits Xiang kind of special equipment. In many cases sub ah, the emerging field of production and recovery are often formed by the embedded microprocessor electronics and basic mechanical system caused by the integrated and enhanced processing capacity.Flexibility of the manufacturing process the request resulted in the production of flexible operating system concepts in this system, many components such as computer numerical control machine tools, robots and automatic guided vehicles, etc. associated with joint production, exchange of information between them through Local Area Network.The products so far, most do not realize the design of electromechanical integration of diversity for the engineering sudden opportunity. The final product sold to customers is the essence of our revenue sources, which may begin the application is the date the new mechatronic products and provide enhanced functionality important difference between traditional products.The following examples may illustrate that the traditional products: Automatic transmission control engine and automatic control of the development of engines and transmissions tend to reduce the radiation, save fuel and time by preventing excessive speed and the use of the fuel flow can be adjusted to avoid false-driven gear and so on.Power-driven tools of modern power-driven tools, such as drill bits you can provide a variety of functions, including speed and torque control, reverse action and acceleration control.The new examples of mechatronic products are as follows:Standard components assembled a traditional industrial robot because of structural problems often many restrictions. Using a number of structural parts and drive, coupled with the central processor can be made by the standard components to assemble the robot system, so users can assemble to meet their own needs various robots.Video and CD player, video and CD player laser head is equipped with sophisticated, you can read the digital information on the disk. Withmicroprocessor control system can provide multi-track selection, scan preview and many other features.The above examples show that the purpose of the use of machinery is the continuous improvement of electronic consumer goods, not to keep consumer prices lower. Machinery and electronics products provide solutions to specific problems of the ideal way to use a low-cost element or standards.The personal computer controller and programmable logic controllerEarly machine tools and robots in the controller's function is to store and perform some simple procedures for the implementation of the tool or device with a predetermined speed to generate the required movement. Since 1981, IBM's first since the emergence of personal computers, many manufacturers produce microprocessors based on its so-called. Through the main memory and secondary storage devices exchange data, which allows users to use than the system microprocessor to provide the actual storage space for more storage space programming. It is this processing power and storage efficiency had a dramatic impact, making more and more industrial sectors to PC, for data acquisition and control applications. In addition to handling capabilities, PC machine control applications as a key component of many other advantages. These advantages are:(1) choice of application software more than a dedicated controller.(2) Select the tools to improve application efficiency and room for more.(3) The PC is available in a variety of forms ranging from a single card, a portable,a desktop and ruggedized industrial version for use on the factory floor.(4) bus architecture with multiple expansion slots, digital and analog input / output cards can be produced by several manufacturers.(5) special machine or a small computer than a more flexible, depending on the application can be very convenient for a variety of configurationsPC, data acquisition and control device may be an additional external and interest rates through, or it may be a plug-in board. Typically add a separate external rack, the internal packaging has to provide power to the host through the serial or parallel data communications cable. A variety of standard format modules can be inserted in the rack as needed.PC, data acquisition There are basically two ways. The first use of analog /digital conversion card connected directly with the host backplane. Conversion cards generally do port address can be any support for input / output command driven programming language. Usually connected to the card, select the base address. This allows a different card or card number the same host in the same PC connection and operation. The second method is to use the interface circuit board with a digital voltage meter and frequency meter and other equipment to control the PC, to receive data. The Common Criteria is an international Association of Electrical and Electronics Engineers IEEE-488 standard parallel communication link. Comparison of fast, easy and economical is the first approach, using the input / output port address the card to the PC, the output of the measurement data or control signals received from the PC machine. These cards are versatile, easy to obtain, and has the following characteristics:(1) multi-channel digital input / Shucu interface with optical isolation and Darlington driver settings.(2) pulse timing and counting facilities.(3) multi-channel programmable A / D conversion.(4) D / A conversion.(5) thermocouple input.PC machine control applications including the latest developments in data acquisition and control software, can provide the user with a drop-down menus and mouse-driven windows environment.Before the invention of the computer control system main relay logic circuit with electrical or pneumatic logic circuits to automate. The late 20th century invention of 60 programmable logic controllers (PLC) directly instead of the relay controller. It should be noted, in the United States, also known as programmable logic controller PLC, abbreviated as PC. Do it with a personal computer PC or IBM-PC to be confused.Programmable logic controllers and micro-computer composed of the same, there are microprocessors, memory and input / output devices. Processor performs memory control process according to input instructions, defined by the logic control program to provide output. Every step during the implementation period, the program is quickly scanned to record all of the input state, then the program logic to determine output. Controller scan each of these steps are repeated.Some small, dedicated to the sequential control of the programmable logic controller usually has 12 input ports and eight output ports are extended to both pinch the 128 input / output circuit. Input interface connected to these lines, the process of receiving input signals from the control, and these signals into a form suitable for processing. Similarly, the programmable logic controller output interface with a variety of process hardware, such as lights, motors, relays and spiral coil.Using a handheld programming keyboard, or with the corresponding software development kit with a personal computer connected to the programmable controller command input random access memory, the random access memory with battery backup power supply generally. If the programmer to establish procedures for using the symbol key, and some programming console LCD display can also display some of the graphics, using ladder logic diagram shows the format process. After a debugging program, the control method through simulation testing, you can put code into erasable programmable read-only memory chips, mounted on the programmable logic controller.Many manufacturers are in the manufacture of programmable logic controller. Although some manufacturers use their own proprietary software language, but most are still using ladder logic diagrams. Invention of this language is intended to be more acceptable to some customers, these customers are interested in is how to shift from hard-line programmable logic controller, relay control. In addition to input / output devices, the programmable logic controller also includes timers, counters, and other special function devices.Communication with other control devices exchange the traditional programmable logic controller is not the strengths of the network. Many industrial controllers are equipped with RS232 serial port, and other digital control equipment systems to exchange information.The robotIndustrial robot is a tool to improve manufacturing productivity. He can assume that humans may have dangerous jobs. The first industrial robot in nuclear power plants had to be replaced and the fuel rods. Industrial robots can work on the assembly line, such as the installation of electronic components, printed circuitboard. In this way, people can escape the monotony of the work stand out. Robots can also remove the bomb, as the disabled person services for our community to do all kinds of work.Robot is a re-programming, multi-agency work can be pre-programmed positions in all moving parts, materials, tools or other special equipment, complete a variety of different jobs.The location is pre-programmed robot to complete the work must follow the path. In some pre-programmed location, the robot will stop some operations, such as installing parts, painting or welding. These pre-programmed location is stored in the robot's memory to recall at any time of continuous operation. If the job requirements changed, the location of these pre-programmed data, together with other programming can be changed. These characteristics make industrial robot programming and computer are very similar.Robot system can control the robot's work unit. Robot work cell robots perform tasks in the work environment. Unit of work, including the robot manipulator, controller, working platforms, safety equipment and gear. In addition, the robot should be able to communicate with the outside world signals.Robot manipulator to complete the specific work of the robot system, which consists of two parts: the mechanical parts and ancillary parts. Subsidiary part of the installed robot base. Several fixed on the floor at the job site. But sometimes the base is able to move, in this case, the base placed in orbit for the robot from one location to another location should be.Subsidiary part of the robot arm. It may be a straight arm can move, it may be a hinged arm, the robot work to provide multiple axes. Articulated arm that is connected to the relevant section of the arm. End of the arm with a wrist. Wrist mounted on another shaft and fitted with flange root. In the flange also can be connected to different tools to complete different tasks. Mechanical axis allows the robot hand in a specific area to work. This area is called the robot unit of work, it depends on the size of the robot. If the robot the size of the increase will increase the size of the unit of work.Manipulator movement control drive or drive system. They drive the state work unit in the rotation. Drive system can make the electrical, hydraulic, it can be pneumatic. Drive power generated by the various institutions converted intomechanical energy, all kinds of drive system is connected by mechanical transmission. Those from the chain, gears and ball screw driven mechanical transmission device composed of the axis of the robot.Used to control the robot to control its movement and the work unit of the external device. Handheld keyboard by hanging the movement of the robot controller program input. The data stored in the controller's memory for future calls.Controllers also work in the unit with an external device to communicate. For example, the controller has an input line. Completion of processing input lines connected, high-speed controller for robot pick in the specified location processed parts. Mechanical hand a new part into the machine, the controller send a signal to start processing.Some of the drum controller is composed by a mechanical operation, the internal implementation of the input sequence of events. The controller is generally used very simple robot system. Most of the robot controller in your system much more complex, reflecting the latest developments in electronic technology. They are controlled by the microprocessor, the operation more flexible.The controller can transmit signals in the communications line. This mechanical hand and two-way communication between the controllers continuously update the location and operation of the system. The controller also includes a computer with different devices to communicate. This communication link to the robot as part of computer-aided manufacturing systems. Microprocessor system uses solid-state storage devices. These storage devices may be magnetic guns, random access memory, floppy disks and tapes.Controller and the robot powered by a power source supply. Robotic systems typically use two kinds of power: a controller may provide alternating current; the other power source used to drive each axis manipulator. For example, if the robot is controlled by a hydraulic or pneumatic drive, these devices will receive the control signal, a robot in motion.The robot sensorAlthough the robot has great ability, but often than not with a little practice, but the workers. For example, workers can find parts that fell on the ground or no parts feeder. But not the sensor, the robot will not get this information. Even the mostsophisticated sensor system, the robot is smaller than an experienced worker. Therefore, a good robot system design requires many sensor and robot controller using the phase to make it operate as close as possible the perception of workers. The most frequently used robotics sensors into contact with the non-contact. Contact sensors can be further divided into tactile sensors, force and torque sensors. Tactile or contact sensors can be measured by the drive-side and the actual contact between other objects, micro-switch is a simple tactile sensor. When the robot by the drive-side contact with other objects, the robot stop motion sensors to avoid collisions between objects to tell the robot has reached the goal; or detection to measure the size of the object. Force and torque sensors in the robot's gripper and wrist joint between the last, or the load on the robot parts, measuring reaction force and torque. Force and torque sensors and piezoelectric sensors are mounted on flexible parts of the strain gauges.Non-contact sensors include proximity sensors, vision sensors, sound detectors, sensitive components and scope. Proximity sensors detect objects near the sensor and the label. For example, eddy current sensor can accurately maintain a fixed distance between the plates. Most cheap robot proximity sensors including a light-emitting diode and a photodiode receiver transmitter, receiver reflector closer to the reflection of light. The main disadvantage of this sensor is closer to the object reflectance of light will affect the received signal. Other proximity sensors using capacitance and inductance associated with the principle.Visual sensing system is very complex, based on the TV camera or laser scanner works. Video signal by hardware pretreatment to 30-60 per second input into the computer. Computer analysis of the data and extract the required information, such as the existence of objects and object features, location, direction of operation, or assembly of components and product testing is complete.Sound sensitive devices used to sense and interpret sound waves. To detect sound waves from the basic continuous speech word for word recognition that people, all kinds of sound ranging from the complexity of sensitive components. In addition to human verbal communication, the robot can use voice control of sensitive components arc welding, I heard the voice of the collision or the collapse of the movement of the robot when the organization to predict the mechanical damage will occur and the detection of objects within the defects.There is also a non-contact systems for projector and imaging the surface of the object surface shape information or distance information.Static detection and closed-loop sensor probe used in two ways. When the detection and operation of the robot system moves alternately, it is usually necessary to use the sensor. That probe is a robot is not operating, the operation has nothing to do with the sensors, this method is called static detection. In this way, vision sensors are looking for is to capture the position and direction of the object, then the robot moves straight to the site.In contrast, closed-loop operation of motion detection robot, always under the control of the sensor. Most sensors are closed loop mode, they can always detect the actual location of the robot and the deviation between the ideal position, and drive the robot fix this error. In the closed-loop detection, even if the object in motion, for example, the conveyor belt, the robot can grasp it and sent it to the desired location.However, in the early 20th century, 80, a number of factors hindered the development of closed-loop detection. The most important reason is the image map for too long, almost equal to the robot move from one place to another time. For practical, for the robot arm motion, image analysis time by reducing down time should be able to accept and explain a few frames.In the use of force and tactile sensor control movement, reaction time to visual sensor that is no longer a problem, because very little information when the sensor transmission. In other words, we can placed on the wrist force and torque sensor 6, or place a finger on the low-resolution binary sensor array. Since the sensor more complex, we can expect delivery by the sensor data can be more of information.中文翻译：工业机器人机电一体化在国际市场中，制造业和工业产品德销售业绩取得的成绩，越来越依靠电子技术和计算机技术与传统机械制造和机械产品的广泛结合。
机械毕业设计外文翻译
A Comparison of Drive Starting Mechanisms forAggregate Belt ConveyorsAbstractThe purpose of this paper is to describe the torque/speed characteristics，during starting conditions，of the most common drives used on belt conveyors today. Requirements of a Belt Conveyor DriveA belt conveyor is considered to be a constant torque device. In other words，the required driving torque is approximately constant at varying speeds (see figure l).other applications，such as a pump drive，have variable torque requirements(see figure2).However，to increase the speed of a conveyor additional torque must be added untilthe desired speed is obtained. Newton’s Second Law of Motion governs this relationship.∑F m a=The most straightforward example would be a constant acceleration torque(see figure3).In reality the acceleration torque is rarely constant. However，static calculation models as outlined in the Conveyor Equipment Manufacturers Association handbook (CEMA) make this assumption. When using static models the average acceleration torque is estimated over the entire acceleration time and assumed to be linear. Dynamic models，which are beyond the scope of this paper，allow acceleration torque values to vary in magnitude during the acceleration(or deceleration)Period.It should be noted that，given a constant load，a larger acceleration torque results in a faster acceleration time and also higher Peak belt tensions. Conversely，a smaller acceleration torque results in a longer start time and smaller Peak belt tensions. Across-The-Line AC Motor StartTechnically this is the simplest type of drive used on a belt conveyor. In this drive type an AC squirrel cage induction motor is started by simply throwing the contactor and energizing the motor. The resulting output torque，assuming that rated voltage is maintained，is strictly a function of the motor design. NEMA has Provided design standards that define the output torque characteristics of the most commonly used 3 Phase motors up to approximately 250 hp(figure4).In sizes larger than 250 hp manufacturers generally use the NEMA design codes in a relative manner(i.e.，NEMA C has a greater locked rotor torque than a NEMA B motor).The most critical locations on the AC motor speed/torque curve have been named for definition purposes. These common names are provided in figure 5.The most rigorous method of determining average acceleration torque，for static calculations，is to break the curve into several vertical sections，then sum the individual areas under the curve and finally divide by the number of sections.The more common way is to apply the following simplified equation:These static approximation methods work for most belt conveyors but can get the designer into trouble from time to time，especially on long and/or steep and/or fastconveyors. One item that needs to be examined is breakaway torque. Just because the drive provides enough average torque to accelerate the load doesn’t mean that it provides enough torque to break it away from zero speed and get it moving.CEMA defines breakaway torque as twice the torque required to overcome the total friction plus the torque required to lift the load vertically. Locked rotor torque (LRT) needs to be greater than breakaway torque! A good static Program makes this check.In addition to examining the effect that average torque has on the conveyor components the belt designer needs to determine the effect of peak torque. It is not uncommon for the breakdown torque (BDT) of a NEMA C motor to be greater than2.5 times full load torque (FLT).Generally the belting and Pulley manufacturers allowa transient overload of 1.5 times full load operating load. An across-the-line start can easily cause tensions to exceed these maximums. These higher than normal loads can be designed into the conveyor if they are known up front.Considering only average starting torque can cause the conveyor designer to undersize the take-up weight. It is not uncommon for conveyors with across-the-line starters to experience intermittent drive slip. This generally happens when Peak torque (BDT) is input by the drive and the take-up has been sized for average torque but not peak torque. The result can be devastating. When the drive pulley slips during this condition，the tension on the Tl and T2 sides (high and low)of the drive Pulley tries to equalize. This can subject a low tension bend or take-up pulley，just behind the drive pulley，to tensions that approach Tl tension. These Pulleys are rarely，if ever，designed for this load condition and the result is low tension Pulley failure. This condition is easily demonstrated with dynamic analysis.Another common Problem with across-the-line starts is caused by voltage dips during starting. If the power distribution system is not stiff enough to handle the huge inrush currents of an across-the-1ine start，the starting torque of the motors can be reduced to a Point that the conveyor will not start. This is due to the fact that the output torque ofan AC squirrel cage induction motor is reduced by the square of the applied voltage. In other words，a voltage drop of 10%would equate to a torque reduction of 19%. Reduced Voltage StartingThe reduced voltage starting of an AC squirrel cage induction motor is done for two basic reasons:1 .To reduce the inrush current that naturally occurs when a motor is Startedacross-the-1ine. A typical current/speed graph is shown in figure 6.It is not uncommon for the inrush current to be 6 times or more than it is at full load torque. As stated above high inrush currents cause the voltage in a power distribution system to sag. The cost of electrical power distribution equipment can become very high if it needs to be designed to handle the high inrush currents.2 . To reduce Peak motor torque during starting conditions，which subsequentlyincreases acceleration time. By reducing the Peak torques the conveyor components can be designed for lower tension loads. This primarily includes belting，Pulleys and external support structure. This can result in significant cost savings.Two common types of reduced voltage starters are the Current Limiting and the Constant Torque devices.Graphs are included above(figures 7 through 8) that depict the same motor/conveyor application with an Across-The-Line，a limitd Curren, and a constant Torque start. After studying the graphs it becomes apparent that the best use of the limited torque start is to protect the power distribution system from high inrush currents. The constant torque start reduces the high torque Peaks and Protects the conveyor’s mechanical components. In both cases the Start time is increased because the over all magnitude of accelerating torque is reduced. However，neither method will make it easier to start a“hard-to-start conveyor.”Correcting a hard starting conveyor is not areason to use a reduced voltage starter!翻译带式输送机驱动方式比较摘要本文的目的是描述最常见的机用输送皮带起动时的扭矩/转速特性。
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附录AThe Design of Pull Arm Garbage Truck1The introduction of Pull Arm Garbage TruckPull arm garbage truck is equipped with two types of chassis that has a trunk load and unloading functions to pull arm device-specific vehicles. It can be achieved with car trunk the combination and separation, while the bulk of the trunk to achieve self-unloading cargo operations. The model has been widely used in foreign countries, often in the domestic industry as a sanitation refuse collection vehicles. 5 t pull arm garbage truck is one of the commonly used models, compared to 8 t Arm pull over large tonnage trucks, the pull-arm device structure is relatively simple and easy to domestic Manufacturers; And large tonnage often imported pull arm device. Domestic Manufacturers producing 5 t pull the car pulling the boom arm structure of the device, although about the same, but the important structural parameters of the selection and design of different structural arrangement, it will directly affect the car performance]20[.2 Pull the boom structure and principle of the device2.1 The structural characteristics of pull-arm device5 t pull arm garbage truck pulling device consists of pulling the boom arm and pull arm cylinder, the United Moving frame, trunk insurance hook and cylinder, and the frame. La Boom device structural arrangement shown in figure 2, pull telescopic arm is not used right-angle bend structure. the end of the cylinder and pull the piston rod side arm hinged on the hinge pivot B; Another linkage frame front end and hinged at the hinge pivot C, the formation of a rotary arm pullheart. Cylinder head cylinder arm pull side hinged front frame on the hinge pivot A; linkage frame hinged rear axle frame rear hinge pivot D, the formation of linkage rotary frame heart. Insurance linkage trunk rack hook set the hook cylinder and insurance cylinder.2.2 The working principle of the device arm pullPulling garbage truck arm by pulling the device to complete the function of two different dynamic, for boxes and dumping. When the pull device for boom box action, the first cylinder insurance hook action open the trunk insurance hook, trunk lift insurance. Pull lift arm cylinder piston rod elongation from the pull arm, pull arm to pivot around the hinge C clockwise rotation, the hook arm to pull back move. If the frame is equipped with a trunk, the trunk was pushed home ground. When put on the frame, so that the first hook retractor trunk rings, and contraction of the piston rod, pull arm to hinge pivot counter-clockwise rotation axis C, will put on the flat trunk, the insurance cylinder hook action, pull carriages insurance hook fixed to the frame to the trunk.When the pull-arm device dumping action, and action for different box, trunk insurance hook dump in the whole process to ensure that tension in the arm and trunk are not isolated, that is pull arm、the linkage through the trunk rack and trunk link between the insurance as one of the hook, by the deputy rear frame hinge pivot clockwise rotation axis D, lifting carriages lifted until the refuse rubbish. Trunk reset, as long as the retraction of cylinder piston rod pull arm, the pulling arm body still hinge pivot point D is the shaft counterclockwise rotation, until the trunk reset.3 La Boom Selection and design of device structure parameters3.1 Device to pull the boom pivot hinge arrangement and geometryof the main structureDetermined by the following three areas:a. Arm by pulling a dump truck performance, it is 5 t pull the best selection of cars from the arm unloading chassis, the chassis can be selected according to the length of pull arm device to determine frame the total length. To ensure the car to pull arm for changing trunk and dumping action by the force of the chassis reasonable and complete the dumping arm pull action pivot hinge rotation axis D of the location should be arranged in behind the rear spring plate from the chassis rear bearing axis, the spacing is about 0 ~ 100 mm.b. According to the first hinge pivot D arm pull for me the beginning of the selected pivot hinge rotation axis C. In the design and production of the actual process of pulling the car arm in arm had appeared during the pull action although the initial state, pull arm lift carriages, failed to pull arm pivot around the hinge C rotation, but with the linkage frame with the rotation around the hinge pivot point D, which can not get trunk open the beginning of fall; when lifting a certain height, the action of gravity in the trunk, the hinge will pivot C a sudden fall, so pull arm, the linkage frame and carriages suddenly drop, resulting in relatively large; in hit, resulting in extremely unsafe for me a smooth action. To resolve this problem, determine the hinge point C of the axis position is especially important. First the one hand, the horizontal axis of pivot C can not above the level layout of pivot D. In addition, by the hinge can pivot C stress analysis know, the hinge pivot axis of C must be below the level of tension hinge pivot arm cylinder head horizontal axis, while the hook arm pull-start action must be arranged in the vertical axis of the hinge pivot between C and the hinge pivot left foot.c. Important geometrical parameters arm pull a pull arm foot radiusof gyration for pull the oil boom turning radius of the cylinder piston rod end of radius of gyration of the angle between the two radius. From the above points analysis we know that, The smaller of radius. The greater the force needed to pull the smaller cylinder arm. Meet the requirements under the premise of arms-for-me pull-foot turning radius, the smaller the better, La boom cylinder rod side radius of gyration R. The bigger the better as far as possible, so that can pull compact boom, operating small space]21[.3.2 The selection of pull arm cylinder and cylinder installation angle y. The range ofDetermined by the following two aspects:a. By mapping method or analytical method to determine the location of the above the hinge pivot and Pull arm geometry and other components, may initially determine the pull-stroke arm cylinder and installation distance.b. Pull arm cylinder mounting angle of La Boom is the important structural parameters of devices. By the former knowledge, pull the boom box or device for carrying out the process of dumping action, pull the oil boom cylinders have to be overcome trunk (full load) resistance torque generated by gravity, and the lifting crane action start unloading boxes when the moment of resistance is the greatest moment of resistance to overcome, and in Boom began pulling action of the hinge pivot device static friction and inertia moment of resistance Maximum torque. So pull arm cylinder mounting angle y. From the previous analysis we know, when angle larger, the pull arm cylinder smaller maximum thrust required, select the pull arm cylinder bore can be smaller.By pulling in the boom cylinder is installed between the frame andtrunk floor, oil cylinder installation layout space is limited, so the pull arm cylinder mounting angle range is also very limited. Design principles to children as much as possible to install a large angle, choose the right drawing arm oil pulling arm cylinder bore to meet performance requirements for the use of vehicles, without increasing the cost and fuel tank weight, and easy layout. Analysis and comparison of some domestic manufacturers to produce 5 t pull arm ,the actual design and production of cars and trucks pulling arm experience, 5 t pull arm around the installation space vehicles between 250 ~ 300 mm, the general tension arm cylinder mounting angle should be Taken between 3°~5°.附录B拉臂式垃圾车设计1拉臂车概述拉臂式垃圾车是在二类汽车底盘上装有使车箱具有装载和卸载功能的拉臂架装置的专用汽车。