机械对外 的设计王猛2 (2)

Pingdingshan Industrial College Of TechnologyBTEC HND in Materials engineering (Mechanical engineering)AssignmentName of Student Wang MengUnit Title Unit7 Materials EngineeringAssignment Title Process and behavior of materials & failure Assignment No Assignment 2Name of Tutor Bai XiaoName of Internal Verifier WangleSubmission Deadline June 26, 2010.Outcomes and Assessment CriteriaOutcome OutcomesAssessment criteriafor passTo achieve eachoutcome a learnermust demonstratethe ability to: Feedback Tutor’sdecisionInternalVerificationIdentify relationships between manufacturing Processes and materials’behaviour(7.2) identify and discuss arange of manufacturingprocesses appropriateto the programme ofstudy2arecognise the influenceof composition andstructureon the processing ofmaterials2brecognisestructure/propertyrelationships, includingtheir influence onprocessing and usage2cDiagnose causes of failure of materials (7.4) identify potentialcauses of failure inservice4aidentify factorsaffecting service life4bidentify service failures 4c carry out estimationsof service life4dsuggest ways ofimproving service life4eMerit Grade CriteriaMerit Descriptors IndicativeCharacteristicsFeedback Tutor’sdecisionInternalVerificationM1.identify and apply strategies to find appropriate solutions effective judgments havebeen madeM1M2.select/design and apply appropriate methods techniques a range of methods andtechniques have beenappliedM2M3. present and communicate appropriate findings a range of methods ofpresentation have been usedandtechnical language has beenaccurately usedM3Distinction Grade CriteriaDistinction Descriptors IndicativeCharacteristicsFeedback Tutor’sdecisionInternalVerificatione critical reflection to evaluate own work and justify valid conclusions conclusions have beenarrived at through synthesisof ideasand have been justifiedD1D2.take responsibility for managing and organizing activities the importance ofinterdependence has beenrecognised andachievedD2D3 .demonstrate convergent/lateral/ creative thinking effective thinking hastaken place in unfamiliarcontextsD3Professor’s additional feedbac k and commentsInternal verification of assignment brief (final agreed version)IV name DateI conform that this is all my own work Student signatureScenarioPart 1The failure of engineering materials is almost always an undesirable event for several reasons; these include human lives that are put in jeopardy,economic losses, and the interference with the availability of products and services. Even though the causes of failure and the behavior of materials may be known, prevention of failures is difficult to guarantee. The usual causes are improper materials selection and processing and inadequate design of the component or its misuse. It is the responsibility of the engineer to anticipate and plan for possible failure and, in the event that failure does occur, to assess its cause and then take appropriate preventive measures against future incidents.RequiredTask 4，5 make up part 1. For task 4 and task 5, You should give your answers using a total formal report, including all the points covering the issues described. You have to cover the following tasks in the assignment: Tasks 1:Identify definition of kinds of heat treatment ，referring to the assignment1（task4）describe appropriate heat treatment processes to the spring. (2a,M1,M2)Spring points thermal forming spring and cold molding spring, after forming in need heat treatmentHot forming spring heat treatment process method :(1) annealing and are spring treatment: ball annealing and softening annealing processing (2) the quenching and tempering treatment: quenching process of the heating temperatureHeat treatment to influence on the performance of the spring :In order to get high elastic limit, spring heat treatment is used mostly quenching and tempering in temperature, get difference of body tissue, quenching can improve the grains will be refined spring impact value, the grains will be refined and can improve the intensity, and can improve the toughness and the plastic, improve yield degrees.Task 2:In the real world, generally can not be pure metal, we can often see a lot of alloy, can you briefly describe a few examples of the composition of the alloy is how it affects their performance？( 2b,D1)(1)The mechanical properties of the alloy decided in ferritic to carbon austenitic steel cementite relative quantity and their relative distribution. When carbon quality score less than 0.9%, with the increase of quality scoreof carbide, strength of carbon steel, hardness greatly increase, plasticity and toughness decline. The reason is steel organization cementite relative increases amount, the ferrite relative decline; When carbon quality score > 0.9% Wc, and carbon of quality score of increasing, hardness is still increase, began to reduce, strength, plastic, toughness continue to decline(2)Steel cementite along the grain boundary, and has formed a complete network separation. The increase in steel brittle. Ensure that the steel have enough strength and certain plasticity and toughness, steel the mechanical engineering use carbon quality score in general not more than 1.4%. Wc > 2.11% of white cast iron, because the organization carburizing density too much, performance of hardness and brittleness, difficult machining, mechanical engineering, rarely used directly(3) In the iron and steel materials, carbon content and the state of the properties of materials play a decisive role. Iron and steel is the distinction between the composition and points for carbon, high carbon is the iron, low for steel. According to the content of carbon steel in different and divided into high carbon steel, medium-carbon steel, low carbon steel and industrial pure ironTasks 3:How does the shape of graphite in cast iron affect its properties? (2c,D3)(1) Graphite is carbon, carbon mainly carbide (Fe3C) exists in the form YuGangZhong, is the main element to steel strength, when the carbon content in the steel up, its hardness and strength were increased, and the plastic, toughness and impact toughness is reduced, orientation and aging tendentiousness ductile-brittle has also been increased. With the rise of the carbon content in the steel, the welding performance significantly. Therefore, used for welding structure of low alloy steel, carbon content is more than 0.25%, general should be no more than 0.22%(2) Graphite formation and chemical composition and the cooling speed relevant.(3) Malleable iron tissue of graphite present contact group, the role of matrix separate than ash iron casting much smaller, toughness and strength is higher than the ash iron casting. Ductile iron organization graphite into the shape of a ball, can reduce stress concentration, and its intensity, tenacity is higherTasks 4:Each student is to obtain an object/structure/component that has failed. It may come from your home, an automobile repair shop, a machine shop,etc. Conduct an investigation to determine the cause and type of failure (i.e., simple fracture, fatigue, creep). In addition, propose measures that can be taken to prevent future incidents of this type of failure. (4a，4b，4e,M2) Tasks 5:According to the task 4 we would got some failure samples ，identify service failures from those and give some calculations or theory to carry out estimations of service life. (4c，4d,M3,D2)The rolling bearing crack phenomenon average performance is two kinds, one is bearing device to high temperature parts, the second is to run the bearing a vibration, the third rolling bearing damageHigh temperature of the measures : (1) the temperature too high to reduce bearing load (2) add lubricant (3) change bearing assembly too tight The measures of reducing the vibration :(1)The normal installation, reduce shaft bearing the bend (2)Use of lubrication oil (3)Bearing wear in time after the gaps between the repair partsBearing damage measures: (1) see bearings inside don't fall into the other objects (2) reduce bearingThe rolling bearing during the work may be due to a variety of causes damage, such as improper assembly, bad lubrication, water, corrosion and overload, etc may lead to premature failure bearing. Even in the installation, lubrication and use is normal maintenance, after a period of time running, bearing also can appear fatigue spalling and wear and can't work normally. In short, rolling bearing fault reason is very complicated. The main form of rolling bearing fault Reasons are as follows :1. Fatigue spalling 2friction 3. Plastic deformation 4. Corrosion 5. Crack 6. Axial gap between Bearings use according to the length of time it depends Computation formula is as followsL10 = C/P typeL10-bearing fatigue life of the basic ratedC-on the bearing for radial equivalent dynamic load （N），ε——Using the time T o ball bearingε=3For rolling bearing ε=10/3According to the calculation formula of the rolling bearing the use time of for thirty thousand hours to forty thousand hoursGeneral Notes to students:·Word process the report. Use 12 point Times New Roman script. The general expectation of layout is that each written assignments should be typed or computer-printed with A4 size sheets. Leave adequate space for 1.5 spaced and 3cm margins to allow space for marker's comments. Use a butterfly or treasury tag to keep the pages of your work together. Include Arabic page numbers.· A word count must be included in all assessed work, failure to do so will result in a penalty of 5% points. A penalty of 1% point will be applied for each 50 words above the specified limit. For example, if the limit is 1000 words, a penalty of 1% is applied for essay of length 1001-1050, 2% for an essay of length 1051-1100 and so on.·Complete the cover sheet and sign the statement of authenticity.·Use the Harvard referencing system. Take great care that if you use other p eople’s work or ideas in your assignment, you properly reference them in your text and any bibliography. (If you are caught plagiarizing, you could have your grade reduced to zero, or at worst, you could be excluded from the course)·Check carefully the submission date and the instructions given with the assignment. Late assignments will not be accepted. If you are unable to hand in your assignment on time and have valid reasons such as illness, you may apply (in writing) for an extension.Added Notes:·The deadline for submitting assignment is 26/06/2011, 4 PM at Teaching Office 301.。