Effect of temperature on the sliding wear performance of Al alloys and Al matrix composites
哈工大版机电工程专业英语翻译分解
单词复习：Shaft Coupling Clutches SpringRigid couplingFlexible couplingHydraulic齿轮机床曲柄振动上一课回顾Lesson 2 Lubrication润滑重点词汇：gaseous/gas/liquid/solidinterpose/pavementportion,sophisticated,interrelate,available,proportional, combat, assist, twofoldParagraph 1Although one of the main purposes of lubrication is to reduce friction, any substance –liquid, solid, or gaseous—capable of controlling friction and wear between sliding surfaces(滑动表面) can be classed as (定义为)a lubricant.尽管润滑的主要目的之一是为了减少摩擦力，任何可以控制两滑动表面之间的摩擦和磨损(wear) 的物质——不管是液体、固体或者气体，都可以归类为(be classed as)润滑剂。
Varieties of lubricationParagraph 2:Unlubricated(无润滑) sliding.Metals that have been carefully treated to remove all foreign materials(异物) seize and weld to one another when slid together.经过精心处理去除了所有杂质(foreign material)的金属在相互滑动时，会粘附(seize)或熔接(weld)到一起.adsorb mit absorb (吸收)In the absence of(如果没有) such a high degree of cleanliness, adsorbed(吸附的) gases, water vapor, oxides(氧化物), and contaminants (杂质)reduce friction and the tendency to seize but usually result in severe wear, this is called “unlubricated”or dry sliding (干滑动).当达不到高的清洁度(cleanliness)时，吸附在表面的气体、水蒸汽、氧化物(oxide)和污染物会降低摩擦力并减少黏附的趋势，但通常会产生严重的磨损，这种现象被称为“无润滑”摩擦或干摩擦(dry sliding)。
Effect of Si content on the dry sliding wear properties of spray-deposited Al–Si alloy
Technical reportEffect of Si content on the dry sliding wear propertiesof spray-deposited Al–Si alloyFeng Wanga,*,Huimin Liu b ,Yajun Ma a ,Yuansheng JinaaState Key Laboratory of Tribology,Tsinghua University,Beijing 100084,ChinabState Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing,Beijing 100083,ChinaReceived 31March 2003;accepted 11August 2003AbstractIn the present investigation,Al–12Si,Al–20Si and Al–25Si (wt%)alloys were synthesized by spray atomization and deposition technique.The wear resistance of the alloys was studied using a pin-on-disc machine under four loads,namely 8.9,17.8,26.7and 35.6N.The microstructures,worn surfaces and the debris were analyzed in a scanning electron microscope.It has been found that the effect of Si content on dry sliding wear of spray-deposited Al–Si alloy was associated with applied loads.At lower load (8.9N),with increasing Si content,the wear rate of the alloy was decreased.At higher load (35.6N),spray-deposited Al–20Si alloy exhibited superior wear resistance to the Al–12Si and Al–25Si alloys.Ó2003Elsevier Ltd.All rights reserved.Keywords:Dry sliding wear;Spray deposition;Al–Si alloy1.IntroductionAl–Si base alloys have been investigated for auto-motive applications because of attractive combinations of low coefficient of thermal expansion,high elastic modulus,excellent wear resistance and good thermal stability [1,2].However,the conventional ingot metal-lurgy leads to coarse primary Si phase which limits the further improvement of the properties of hypereutectic Al–Si alloy.One approach that has been utilized to suppress the formation of the coarse,brittle,primary Si phase and eutectic phases is rapid solidification [3].Spray deposition process has an obvious modification in size,morphology and distribution of the primary Si phase in matrix as well as reduce of segregation.In this process,droplets are first atomized from a molten metal stream,quickly cooled by an inert gas,then deposited on a substrate,and finally built up to form a deposit with a required shape [4].The spray-deposited Al–Si alloys have been considered as potential application inthe tribological field,and are becoming a favorite ma-terial as rotor brake,bearing sleeve,cylinder liner and compressor scroll.Wear properties of these alloys have been studied mainly under dry sliding conditions against a steel counterface.The present work is aimed at un-derstanding the effect of Si content on dry sliding wear property of spray-deposited Al–Si alloy.With observa-tion and analyses of worn surfaces and wear debris,the wear mechanism of the alloys has been discussed.2.Experimental proceduresThe spray deposition experiments were conducted in an environmental chamber (manufactured by Osprey company,Swansea,UK).During spray-deposited pro-cess,the melting metal was atomized by N 2and the atomizing temperature is 1073K,the distance of at-omizing deposition was kept constant at 400mm.Wear test was carried out using a FALEX-6type pin-on-disc machine (Falex corporation,Sugar Grove,Illi-nois,USA).The wear specimens were machined in the form of cylinders with 4.8mm diameter and 12.7mm length.The counterpart discs were made of aquenchedMaterials and Design 25(2004)163–166/locate/matdesMaterials &Design*Corresponding author.Tel.:+86-10-62783968;fax:+86-10-6278-1379.E-mail address:wfbs@ (F.Wang).0261-3069/$-see front matter Ó2003Elsevier Ltd.All rights reserved.doi:10.1016/j.matdes.2003.08.005and tempered T8tool steel with a nominal chemical composition (mass percent):Fe–0.8%C–0.35%Mn–0.3%Si,surface hardness of 64HRC and surface rough-ness of Ra ¼1l m.The applied load was varied from 8.9to 35.6N (8.9,17.8,26.7and 35.6N).Sliding speed and distance were kept constant at 0.48m/s and 1.7km.The weight loss during wear test was measured using a photoelectric balance with the resolution of Æ0.1mg.Three pins were used during each test.The specimens were thoroughly cleaned with acetone in ultrasonic cleaner before and after the wear test.Wear rate was calculated by dividing weight loss by sliding distance.Microstructure,worn surface and debris were charac-terized using a CSM-950type scanning electron micro-scope (SEM)(Opton corporation,Germany)attached with energy dispersive X-ray analyses (EDX).The mi-crostructures of the alloys were revealed by etching with Keller Õs reagent.3.Results3.1.MicrostructureFig.1show the typical SEM microstructures of the spray-deposited Al–Si alloys,which is composed of the Al matrix and the Si phase with a particle shape.The presence of eutectic Al–Si alloy phase and coarse,block primary Si phase in the conventionally processed ingot metallurgy counterpart was suppressed.The presence of particulate-like Si dispersoids was attributed to the high cooling rate,associated with the rapid solidification processes [5].Meanwhile,it can be seen that the volumefraction of primary Si phase was increased with in-creasing of Si content.3.2.Wear3.2.1.Wear testFig.2shows the wear test results,which represent the wear rate as a function of the applied load.Obvi-ously,the wear rate of the alloys increases with in-creasing load.It may also be noted that the tendency of the wear rate variation with the applied load is not consistent for three materials.At low load of 8.9N,the wear resistance of spray-deposited Al–25Si alloy was superior to the Al–12Si and Al–20Si alloys.With an increase in load of up to approximately 18N,the wear rates of the three materials are comparable.Beyond 20Nomenclature Ra Surface roughnessSEM Scanning electron microscope EDXEnergy dispersive X-ray analyseswt%Weight percentT8tool steelFe–0.8%C–0.35%Mn–0.3%SiFig.1.Microstructures of spray-deposited Al–Si alloys:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.Fig.2.Variations in the wear rates of spray-deposited Al–Si alloys with load.164 F.Wang et al./Materials and Design 25(2004)163–166N,the spray-deposited Al–20Si alloy exhibited best wear resistance.3.2.2.Worn surfaces and wear debrisIn order to investigate the wear mechanism,the surfaces of the worn samples were examined under SEM.Figs.3and4show typical worn surfaces of the three materials at the applied load of8.9,35.6N,re-spectively.At low load of8.9N,large dimples are easily found on the worn surface of spray-deposited Al–12Si alloy,it indicates that hard primary Si phases have stronger abrasive wear to the soft Al matrix during wear test.Some small dimples are also seen in the surfaces of spray-deposited Al–20Si,Al–25Si alloys. At high load of35.6N,the worn surfaces of the alloys have a rather smooth appearance as a result of ho-mogeneous wear,it indicates that wear process mainly took place by plastic deformation,as can be seen in Fig.4.Fig.5shows SEM micrographs of the wear debris generated at load of35.6N.For spray-deposited Al–12Si alloy,the wear debris is in form of irregular shaped platelets.The wear debris of spray-deposited Al–20Si, Al–25Si alloys is composed offine powders and irregu-lar shaped platelets orflakes.4.DiscussionOne of the important parameters which greatly affects the wear property of the Al–Si alloys is the primary Si phases in the matrix[6].However,the primary Si phases play an important role in the wear process.At low load of8.9N,the good wear resistance of spray-deposited Al–25Si alloy can be attributed to the presence of high volume fraction of the primary Si phases that act as load-supporting elements.In order to remain as effective load-bearing elements,the particle-like Si phases should maintain their structural integrity during wear.In this case,the local stresses generated beneath the slider are lower than the fracture strength of the Si particles,the primary Si particles without fracture on the worn sur-face can scratch the counterpart surface and act as load-supporting elements.The initial surface topographies of spray-deposited Al–Si alloys are suitable to facilitate the transfer of the applied load onto the primary Si parti-cles.The primary Si particles stand proud of the pol-ished contact surfaces,this is considered to be useful to prevent the softer Al matrix becoming directly involved in the wear process.During this process,the wear pro-ceeds mainly by the formation of oxidation layer in the worn surface and its spalling[7].EDX was used tocheck Fig.3.SEM morphologies of worn surfaces of spray-deposited alloys at the load of8.9N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.Fig.4.SEM morphologies of worn surfaces of spray-deposited alloys at the load of35.6N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.F.Wang et al./Materials and Design25(2004)163–166165the composition of worn surfaces of the pins,it showed that worn surfaces contain a certain amount of Fe and O,which indicates a typical oxidative wear [8].With in-creasing load,the primary Si particles fracture above a certain load,and the fragmented Si particles lose their ability to support the load.In this case,the Al matrix be-comes in direct contact with the counterfaces.At high load of 35.6N,concurrent with the primary Si particle fracture,large strain were generated within the Al matrix adjacent to contact surfaces.This led to the subsurface crack growth and delamination.The broken,hard Si particles entrapped between the counterface and the alloys may act as third-body abraders and be responsible for the pro-duction longitudinal grooves on the worn surfaces,as can be seen in Fig.4.The fractured primary Si particles pro-mote the worn surface damage and act as third-body abrasives,thus,the spray-deposited Al–20Si alloy pro-vided better wear resistance than Al–25Si alloy.The SEM photographs indicate that the wear debris contain a lot of shiny metallic flakes,together with some small powder.This is an indication of delamination [9].It is also possible that the hard dispersoid particles or fractured pieces thereof are mechanically dislodged during wear.The de-lamination and third-body abrasion are identified as the two major mechanisms at high load of 35.6N.5.ConclusionIn a range of applied load of 8.9–35.6N,the dry sliding wear behaviors of spray-deposited Al–Si alloys have been studied.The effect of Si content on the dry sliding wear of spray-deposited Al–Si alloy was associ-ated with applied loads.(1)At low load (8.9N),the wear rate of spray-de-posited Al–Si alloy was decreased with increasing Si content,the dominant wear mechanism was oxidative mechanism.(2)At high load (35.6N),spray-deposited Al–20Si alloy displayed superior wear resistance to the Al–12Si and Al–25Si alloys,the dominant wear mechanism was delamination and third-body abrasion.References[1]Anand S,Srivatsan TS,Wu Y,Lavernia EJ.Processing,microstructure and fracture behaviour of a spray atomized and deposited aluminum–silicon alloy.J Mater Sci 1997;32:2835–48.[2]Zhou J,Duszczyk J,Korevaar BM.As-spray-deposited structure of an Al–20Si–5Fe Osprey perform and its development during subsequent processing.J Mater Sci 1991;26:5275–91.[3]Lim SC,Gupta M,Leng YF,Lavernia EJ.Wear of a spray-deposited aluminum–silicon alloy.J Mater Process Technol 1997;63:865–70.[4]Lavernia EJ,Wu Y.Spray atomization and deposition.England Wiley press;1996.pp.487–9.[5]Zhou J,Duszczyk J,Korevaar BM.Structural development during the extrusion of rapidly solidified Al–20Si–5Fe–3Cu–1Mg alloy.J Mater Sci 1991;26:824–34.[6]Prased BK,Venkateswarlu K,Modi OP,Jha AK,Das S,Dasgupta R,Yegneswaran AH.Sliding wear behavior of some Al–Si alloys:role of shape and size of Si particles and test conditions.Metall Mater Trans A 1998;29A:2747–52.[7]Saheb N,Laoui T,Daud AR,Harun M,Radiman S,Yahaya R.Influence of Ti addition on wear properties of Al–Si eutectic alloys.Wear 2001;249:656–62.[8]Gui M,Kang SB,Lee JM.Wear of spray deposited Al–6Cu–Mn alloy under dry sliding conditions.Wear 2000;240:186–98.[9]Sahoo KL,Krishnan CSS,Chakrabarti AK.Studies on wear characteristics of Al–Fe–V–Si alloys.Wear2000;239:211–8.Fig.5.SEM micrographs showing wear debris generated at the load of 35.6N:(a)Al–12Si;(b)Al–20Si;(c)Al–25Si.166 F.Wang et al./Materials and Design 25(2004)163–166。
机械专业毕业论文中英文翻译--在全接触条件下,盘式制动器摩擦激发瞬态热弹性不稳定的研究
Frictionally excited thermoelastic instability in disc brakes—Transientproblem in the full contact regimeAbstractExceeding the critical sliding velocity in disc brakes can cause unwanted forming of hot spots, non-uniform distribution of contact pressure, vibration, and also, in many cases, permanent damage of the disc. Consequently, in the last decade, a great deal of consideration has been given to modeling methods of thermo elastic instability (TEI), which leads to these effects. Models based on the finite element method are also being developed in addition to the analytical approach. The analytical model of TEI development described in the paper by Lee and Barber [Frictionally excited thermo elastic instability in automotive disk brakes. ASME Journal of Tribology 1993;115:607–14] has been expanded in the presented work. Specific attention was given to the modification of their model, to catch the fact that the arc length of pads is less than the circumference of the disc, and to the development of temperature perturbation amplitude in the early stage of breaking, when pads are in the full contact with the disc. A way is proposed how to take into account both of the initial non-flatness of the disc friction surface and change of the perturbation shape inside the disc in the course of braking.Keywords: Thermo elastic instability; TEI; Disc brake; Hot spots1. IntroductionFormation of hot spots as well as non-uniform distribution of the contact pressure is an unwanted effect emerging in disc brakes in the course of braking or during engagement of a transmission clutch. If the sliding velocity is high enough, this effect can become unstable and can result in disc material damage, frictional vibration, wear, etc. Therefore, a lot of experimental effort is being spent to understand better this effect (cf. Refs.) or to model it in the most feasible fashion. Barber described the thermo elastic instability (TEI)as the cause of the phenomenon. Later Dow and Burton and Burton et al.introduced a mathematical model to establish critical sliding velocity for instability, where two thermo elastic half-planes are considered in contact along their common interface. It is in a work by Lee and Barber that the effect of the thickness was considered and that a model applicable for disc brakes was proposed. Lee and Barber’s model is made up with a metallic layer sliding between twohalf-planes of frictional material. Only recently a parametric analysis of TEI in disc brakes was made or TEI in multi-disc clutches and brakes was modeled. The evolution of hot spots amplitudes has been addressed in Refs. Using analytical approach or the effect of intermittent contact was considered. Finally, the finite element method was also applied to render the onset of TEI (see Ref.).The analysis of nonlinear transient behavior in the mode, when separated contact regions occur, is even accomplished in Ref. As in the case of other engineering problems of instability, it turns out that a more accurate prediction by mathematical modeling is often questionable. This is mainly imparted by neglecting various imperfections and random fluctuations or by the impossibility to describe all possible influences appropriately. Therefore, some effort aroused to interpret results of certain experiments in addition to classical TEI (see, e.g.Ref).This paper is related to the work by Lee and Barber [7].Using an analytical approach, it treats the inception of TEI and the development of hot spots during the full contact regime in the disc brakes. The model proposed in Section 2 enables to cover finite thickness of both friction pads and the ribbed portion of the disc. Section 3 is devoted to the problems of modeling of partial disc surface contact with the pads. Section 4 introduces the term of ‘‘thermal capacity of perturbation’’ emphasizing its association with the value of growth rate, or the sliding velocity magnitude. An analysis of the disc friction surfaces non-flatness and its influence on initial amplitude of perturbations is put forward in the Section 5. Finally, the Section 6 offers a model of temperature perturbation development initiated by the mentioned initial discnon-flatness in the course of braking. The model being in use here comes from a differential equation that covers the variation of the‘‘thermal capacity’’ during the full contact regime of the braking.2. Elaboration of Lee and Barber modelThe brake disc is represented by three layers. The middle one of thickness 2a3 stands for the ribbed portion of the disc with full sidewalls of thickness a2 connected to it. The pads are represented by layers of thickness a1, which are immovable and pressed to each other by a uniform pressure p. The brake disc slips in between these pads at a constant velocity V.We will investigate the conditions under which a spatially sinusoidal perturbation in the temperature and stress fields can grow exponentially with respect to the time in a similar manner to that adopted by Lee and Barber. It is evidenced in their work [7] that it is sufficient to handle only the antisymmetric problem. The perturbations that are symmetric with respect to the midplane of the disc can grow at a velocity well above the sliding velocity V thus being made uninteresting.Let us introduce a coordinate system （x1; y1）fixed to one of the pads (see Fig. 1) thepoints of contact surface between the pad and disc having y1 = 0. Furthermore, let acoordinate system （x2; y2）be fixed to the disc with y2=0 for the points of the midplane. We suppose the perturbation to have a relative velocity ci with respect to the layer i, and the coordinate system （x; y）to move together with the perturbated field. Then we can writeV = c1 -c2; c2 = c3; x = x1 -c1t = x2 -c2t,x2 = x3; y = y2 =y3 =y1 + a2 + a3.We will search the perturbation of the uniform temperature field in the formand the perturbation of the contact pressure in the formwhere t is the time, b denotes a growth rate, subscript I refers to a layer in the model, and j =-1½is the imaginary unit. The parameter m=m（n）=2pin/cir =2pi/L, where n is the number of hot spots on the circumference of the disc cir and L is wavelength of perturbations. The symbols T0m and p0m in the above formulae denote the amplitudes of initial non-uniformities (e.g. fluctuations). Both perturbations (2) and (3) will be searched as complex functions their real part describing the actual perturbation of temperature or pressure field.Obviously, if the growth rate b<0, the initial fluctuations are damped. On the other hand, instability develops ifB〉0.2.1. Temperature field perturbationHeat flux in the direction of the x-axis is zero when the ribbed portion of the disc is considered. Next, let us denote ki = Ki/Qicpi coefficient of the layer i temperature diffusion. Parameters Ki, Qi, cpi are, respectively, the thermal conductivity, density and specific heat of the material for i =1,2. They have been re-calculated to the entire volume of the layer (i = 3) when the ribbed portion of the disc is considered. The perturbation of the temperature field is the solution of the equationsWith and it will meet the following conditions:1，The layers 1 and 2 will have the same temperature at the contact surface2，The layers 2 and 3 will reach the same temperature and the same heat flux in the direction y,3，Antisymmetric condition at the midplaneThe perturbations will be zero at the external surface of a friction pad(If, instead, zero heat flux through external surface has been specified, we obtain practically identical numerical solution for current pads).If we write the temperature development in individual layers in a suitable formwe obtainwhereand2.2. Thermo elastic stresses and displacementsFor the sake of simplicity, let us consider the ribbed portion of the disc to be isotropic environment with corrected modulus of elasticity though, actually, the stiffness of this layer in the direction x differs from that in the direction y. Such simplification is, however, admissible as the yielding central layer 3 practically does not take effect on the disc flexural rigidity unlike full sidewalls (layer 2). Given a thermal field perturbation, we can express the stress state and displacements caused by this perturbation for any layer. The thermo elastic problem can be solved by superimposing a particular solution on the general isothermal solution. We look for the particular solution of a layer in form of a strain potential. The general isothermal solution is given by means of the harmonic potentials after Green and Zerna (see Ref.[18]) and contains four coefficients A, B, C, D for every layer. The relateddisplacement and stress field components are written out in the Appendix A.在全接触条件下，盘式制动器摩擦激发瞬态热弹性不稳定的研究摘要超过临界滑动盘式制动器速度可能会导致形成局部过热，不统一的接触压力，振动分布，而且，在多数情况下，会造成盘式制动闸永久性损坏。
The Effect of Temperature on Reaction Rate
The Effect of Temperature on ReactionRate温度对反应速率的影响反应速率是化学反应过程中一个非常重要的参数，它可以代表反应中物质的消耗或产生速度。
温度是影响反应速率的重要因素之一。
本文将阐述在理论和实验研究中温度对反应速率的影响。
理论基础热力学和动力学是研究反应速率的两个重要分支。
热力学研究反应是否可以进行，而动力学则探讨反应的速度和速率方程。
根据热力学原理，反应过程中需要扰动原有平衡热力学状态，因此需要吸收或释放热量来实现反应。
当温度上升时，反应物分子的速度增加，反应过程中的活化能减少，反应速率随之增加。
反应速率与温度变化的关系在温度改变下，反应速率会发生变化。
一个典型的实例是火柴点燃的过程。
火柴头燃烧的量少，在室温下需要大约10秒才能点燃。
然而，在高温下，点燃时间会大大缩短。
这是因为温度上升导致火柴头表面和空气之间的分子碰撞更加频繁，火柴头内部的分子更有可能高速振动，进而导致温度升高得更快，并促进反应的进行。
另一个典型实例是化学反应速率随温度变化的图示。
在一定温度范围内，反应速率随温度升高而增加，符合阿累尼乌斯方程式。
该方程式表达了当温度上升时，反应速率指数呈指数增加，反应速率随着温度的上升而指数级增加。
实验研究实验研究可以量化温度对反应速率的影响。
一般来说，在实验中，可以将反应物放在容器中，用加热器加热直至反应开始，测量反应物的消耗或产物的生成速率来确定反应速率。
研究表明，温度升高每10℃，反应速率大约增加2倍。
这种反应速率与温度的关系称为“阿累尼乌斯方程式”，其中n称为反应速率指数，Ea称为反应过程的活化能。
结论温度是影响化学反应速率最为重要的因素之一。
当温度升高时，反应过程中的活化能会减少，反应速率随之增加。
实验研究也表明，温度升高每10℃，反应速率大约增加2倍。
理解反应速率与温度变化的关系对于化学反应和工艺控制有着重要的意义，这种理解具有重要的工程和科学应用。
The Effect of Temperature on Protein Conformation
The Effect of Temperature on ProteinConformationProteins are essential components of living organisms and are responsible for carrying out various cellular functions. They are composed of long chains of amino acids that are folded into intricate 3-dimensional structures. The specific shape of a protein, or its conformation, plays a critical role in its function. Temperature is one of the key factors that can influence protein conformation. In this article, we will explore the effect of temperature on protein conformation and how it impacts their function.Temperature-induced protein denaturationProtein denaturation is a process in which the protein loses its native conformation and unfolds into a linear or random coil structure. This process can be triggered by several factors, including pH, salts, mechanical stress, and temperature. Among these, temperature is the most commonly studied factor that can induce protein denaturation.When proteins are exposed to high temperatures, the thermal energy causes the bonds that hold the protein structure together to break. Hydrogen bonds, which are weaker than covalent bonds, are the first to be broken. As the temperature continues to rise, the more significant covalent bonds that hold the protein together begin to break, further destabilizing the structure. Ultimately, the protein loses its native conformation, and its function is impaired.The effect of temperature on protein stabilityThe stability of a protein refers to its ability to maintain its native conformation in the face of various environmental conditions, including temperature. The stability of a protein is influenced by several factors, including the amino acid sequence, solvent conditions, and the presence of ligands or cofactors. Temperature can disrupt the stability of a protein by altering its structure and causing it to denature.Proteins have a range of thermal stability that depends on their amino acid sequence and their specific structure. Generally, proteins that are stable at higher temperatures have a higher content of hydrophobic amino acids, which can help to stabilize the structure through hydrophobic interactions. In contrast, proteins that are stable at lower temperatures tend to have more polar amino acids and a lower content of hydrophobic amino acids.The temperature at which a protein denatures is known as its melting temperature or Tm. The Tm of a protein is influenced by its intrinsic stability as well as the specific conditions under which it is studied. For example, the pH, salt concentration, and presence of other molecules can all affect the Tm of a protein.The effect of temperature on protein functionThe specific conformation of a protein plays a critical role in its function. Therefore, changes in protein conformation due to temperature can have a significant impact on their function. The effect of temperature on protein function can vary depending on the specific protein and the conditions under which it is studied.Some proteins are more sensitive to changes in temperature than others. For example, enzymes, which catalyze chemical reactions in the cell, have a specific optimal temperature range at which they function best. Outside of this range, the reaction rate can slow down or even stop altogether due to changes in protein conformation.Other proteins, such as transporters and receptors, are also sensitive to changes in temperature. Changes in protein conformation due to temperature can affect the ability of these proteins to bind to their ligands and carry out their function.ConclusionIn conclusion, temperature has a significant impact on protein conformation. High temperatures can cause proteins to denature, while changes in temperature can alter their stability and affect their function. Understanding the effect of temperature on protein conformation and function is essential for designing experiments and developing new drugs and therapies that target specific proteins.。
Effect of tool temperature on the reduction of the
Short communicationEffect of tool temperature on the reduction of thespringback of aluminum sheetsY .H.Moon *,S.S.Kang,J.R.Cho,T.G.KimDepartment of Mechanical Engineering,Pusan National University,Pusan 609-735,South Korea Received 19September 2001;received in revised form 20March 2002;accepted 9September 2002AbstractThe effect of tool temperature on the reduction of springback amount of aluminum 1050sheet has been investigated in this study.As the springback phenomenon is caused by elastic recovery of deformed sheet,the control of elastic recovery is important in decreasing the amount of springback.Therefore,any combination of tool temperature that can reduce elastic recovery can be effective in reducing the amount of springback.The experimental verification of U-bent aluminum 1050sheet shows that the combination of hot die and cold punch can reduce the amount of springback up to 20%when compared to conventional room temperature bending test.#2002Elsevier Science B.V .All rights reserved.Keywords:U-bending;Springback;Al-1050sheet;Tool temperature control1.IntroductionSheet metal bending is one of the most widely applied sheet metal forming operations.In the fabrication of sheet metals,the elastic recoveries after unload causes the spring-back phenomenon in which the radius of curvature in bending increases after the bending moment is removed.Therefore,the precise prediction of springback is a key to assessing the accuracy of part geometry.Springback is influenced by several factors,such as sheet thickness,elastic modulus,yield stress,work hardening exponent,etc.;the inaccurate definition of the dependence of springback on the above parameters can cause products loss due to scrapping or reworking.Therefore,sound operation is strongly related to the capabilities of adapting the operational conditions to reflect variations in raw material properties.In bending systems,this means that close tolerances can be obtained by compensating for springback using the actual mechanical and geometrical properties of materials under deformation.The design and control of a bending process depends not only on the workpiece material,but also on the condition at the tool–workpiece interface,the mechanics of plastic defor-mation and the equipment used.Numerous fundamental studies have been conducted over the years in an attempt to obtain a basic understanding of springback behavior.These research activities have been extended from elasticity to plasticity,from small curvaturebending to large curvature bending,from pure bending to stretch bending [1–6].The stress distribution in a sheet metal bending part before unloading decides the magnitude and direction of springback of the part after unloading.If this part is to be further formed at subsequent operation,this residual stress distribution left by a previous operation will affect the stress distribution of the part in the subsequent operation,and hence the springback of the part after the last operation.The behavior of metal sheets in press forming dies often appears to be affected by temperature [7–12].The actual temperature is largely determined by the press speed,the metal thickness,temperature of the tooling components and the lubrication.The strength of metals decreases when it is heated.This well-known effect has been used to advantage in many metal forming operations,but it has been generally ignored in sheet metal forming.However,the decrease in strength is substantial at even the small temperature increases encountered in aluminum sheet metal forming [7–9].Therefore,the effect of tool temperature on the reduction of springback amount of aluminum 1050sheet has been investigated in this study.Emphases are placed on the reduction of springback amount in terms of combination of die and punch temperature.2.Experimental procedureCommercially available Al-1050aluminum sheets with thickness of 0.8mm are used for test materials.ThespecimenJournal of Materials Processing Technology 132(2003)365–368*Corresponding author.0924-0136/02/$–see front matter #2002Elsevier Science B.V .All rights reserved.PII:S 0924-0136(02)00925-1dimensions were 140mm length and 100mm width with the length direction in the rolling direction.The punch and die used for the tests are schematically shown in Fig.1.To reduce the punch temperature to À10to À158C special air cooling device is used.The punch has been bored out and a baf fle is inserted to increase the cooling ef ficiency of frigid air.In addition,electric-cartridge type heaters are attached to the die to raise the temperature.For the uni-formity of temperature,test blank has been held for one minute before the test start.Proper tool steel with appropriate mechanical properties and hardening treatment was used for the materials of the punches and dies.The tools were ground to an appropriate surface finish and a final hardness of 64HRC.The width of the punch was 100mm having a corner radius of 6mm.The die walls were parallel.In parallel-wall dies,the die-entrance radii R were 6mm.Tests were carried out by a 10t hydraulic sheet forming test machine with a device to control and display punch load and punch stroke.In this machine,the punch is mounted on the upper shoe and the die on the lower shoe of the machine.The range of crosshead speed was 1–10mm/s.On the U-bent test sheet,the experimental data were taken at two locations —the base width,A ,taken at 1mm above the channel bottom and the other,opening distance,B ,at the top of the channel.Springback,in terms of angle,was computer by y ¼tanÀ1B ÀA 2W(1)where W is the side wall length of the channel as shown in Fig.2.To examine the temperature dependency of Al-1050,high temperature tension tests by using radiant heating system and low temperature tension tests by using liquid nitrogen are also performed.Fig.3shows the variation of yield stress with temperature.An operational sequence is arranged for the tests and the amount of springback is measured as function of test vari-ables.Experimental variables in this study are described in Table 1.As the die and punch temperatures,described in Table 1,are set-up temperatures,some discrepancies may exist between set-up temperature and actual sheet temperature.In case of normal punch without frigid air,the initial set-up temperature is 258C.But punch may be heated up by heat of sheet during the bending process.Therefore actual tem-perature of punch may depend on the temperature of deforming sheet.In case of cold punch,the initial set-up temperature is À108C.As the frigid air consistently flows from inlet to outlet of punch,contact temperature of À108C is maintained even in the heated sheet.Various punch speeds are applied to investigate the deformation rate effect on the springbackreduction.Fig.1.Schematic drawing of the bending testequipment.Fig.2.Schematic drawing of specimen after bending.Table 1Experimental conditionsSheet dimension (mm)thickness,width,length 0.8,100,140Clearance (%)20Punch temperature (8C)À10,25Die temperature (8C)25,100,200Ram speed (mm/s)1,2,4,6,8,10366Y.H.Moon et al./Journal of Materials Processing Technology 132(2003)365–368Experiments were carried out at various combinations of tool temperatures progressively until the optimum process condition that can minimize the amount of springback was obtained.3.Results and discussionAn operational sequence was arranged for the test and preliminary test,and average values were obtained at given test conditions.Fig.4shows the measured springback amounts at various combinations of tool temperatures.As shown in the figure,the springback amounts are signi ficantly in fluenced by tool temperature.The springback amount is increased with ram speed and its sensitivity on the ram speed is increased in the order of die temperature of 25,100and 2008C.With increasing die temperature,the overall amount of springback is decreased due to the lowered flow stress at elevated temperatures.And,the sensitivity of springback amount on the ram speed is increased with die temperatures.The strain rate sensitivity [13]of metal is quite low at room temperature but it increases with temperature.Therefore,higher die temperature with lower ram speed is a favorable condition for the reduced springback amount.In case of punch temperature,the effect of hot punch is not experimentally implemented in this study because the trend is similar with that of heated die,but the combination of hot die and cold punch,which simultaneously induce high temperature at die part (lower side of bending sheet)and low temperature at punch part (upper side of bending sheet),is experimentally investigated.The stress distribution in a sheet metal bending part before unloading decides themagnitude and direction of springback of the part after unloading.The combination of hot die with cold punch changes the stress distribution in thickness direction,and the reduction of elastic recovery after unloading due to the temperature differences between both side of the sheet is responsible for the decrease in springback.Fig.4(a)shows the effect of punch temperatures on the springback amounts at the condition of non-heated die.As shown in the figure,the springback amount is reduced when using cold punch (À108C).Fig.4(b)shows the effect of punch temperatures on the springback amounts at the die temperature of 1008C.As shown in the figure,the spring-back amount is reduced when using cold punch (À108C)at the ram speed range of below 6mm/s.Fig.4(c)shows the effect of punch temperatures on the springback amounts at the die temperature of 2008C.In this case,the springback amount is reduced when using cold punch (À108C)at the ram speed range of above 4mm/s.The effect of cold punch on the reduction of springback amount shown in Fig.4clearly shows that a proper ram speed is important for the reduced springback.In case of Fig.4(a),the less reductions at higher ram speeds are probably due to the insuf ficient cooling at higher ram speeds.But,the effect of cold punch is more compli-cated at heated dies:excessive ram speeds can cause insuf-ficient cooling and/or heating effect on the surface of sheets:whilst insuf ficient speeds reduce the temperature difference between upper and lower surface of sheets.The experimental results shows that tool temperature control is very effective way in reducing the amount of springback,and any combination of tool temperature can reduce springback amount when it has potential to reduce elastic recovery afterunloading.Fig.3.Variation of yield stress with temperature.Y.H.Moon et al./Journal of Materials Processing Technology 132(2003)365–3683674.Conclusion(1)The effectiveness of tool temperature control methodhas been experimentally confirmed by actual measure-ment of springback amount of U-bent aluminum 1050.(2)Hot die is very effective in reducing springback amountand the combination of hot die and cold punch can reduce the amount of springback up to 20%when compared to conventional room temperature bending test.(3)In case of tool temperature control,proper ram speed isimportant for the reduced springback because the effectiveness of the tool temperature control depends on how well the metal can be heated or cooled.(4)The change in stress distribution through the tooltemperature control decides the magnitude and direc-tion of springback of the part after unloading.AcknowledgementsThis work has been supported by the Research Grant which is financed by Department of Mechanical Engineer-ing in Pusan National University.References[1] F.Pourboghrat,E.Chu,Springback in plane strain stretch/draw sheetforming,Int.J.Mech.Sci.36(1995)327–341.[2] F.Paulsen,T.Welo,Application of numerical simulation in thebending of aluminum-alloy profiles,J.Mater.Process.Technol.58(1996)274–285.[3]T.X.Yu,W.Johnson,Influence of axial force on the elastic –plasticbending and springback of a beam,J.Mech.Work.Technol.6(1982)5–21.[4]T.X.Yu,W.Johnson,The large elastic –plastic deflection withspringback of a circular plate subjected to circumferential moments,ASME J.Appl.Mech.49(1982)507–515.[5]J.C.Gerdeen,J.L.Duncann,Springback in sheet metal forming,AISIReport No.1201-465,1986.[6]M.Huang,J.C.Gerdeen,Springback of doubly curved developable sheetmetal surface —an overview,SAE Technical Paper No.940938,1994.[7]S.Novotiny,M.Geiger,Process design for hydroforming oflightweight metal sheets at elevated temperatures,in:Proceedings of the Ninth International Manufacturing Conference in China,Hong Kong,2000,pp.289–290.[8]S.Novotiny,M.Celeghini,M.Geiger,Measurement of materialproperties of aluminum sheet alloys at elevated temperature,in:Proceedings of the Eighth SheMet ’00,Birmingham,2000,pp.363–370.[9]S.Novotiny,P.Hein,Hydroforming of sheet metal pairs fromaluminum alloys,in:Proceedings of the Seventh SheMet ’99,Bamberg,1999,pp.591–598.[10]P.A.Friedman,A.K.Ghosh,Microstructural evolution and super-plastic deformation behavior of fine grain 5083Al,Metall.Mater.Trans.A 27(12)(1996)3827–3839.[11] D.H.Bae,A.K.Ghosh,The effect of grain size on superplastic behaviorof 5083Al,in:Proceedings of the TMS Annual Meeting on Super-plasticity and Superplastic Forming,San Antonio,1998,pp.145–154.[12]Y .H.Moon,Y .K.Kang,J.W.Park,S.R.Gong,Tool temperaturecontrol to increase the deep drawability of aluminum 1050sheet,Int.J.Mach.Tool.Manuf.41(2001)1283–1294.[13]G.E.Dieter,Mechanical Metallurgy,3rd ed.,McGraw-Hill,NewYork,1986,pp.297,307–309.Fig.4.Effect of tool temperatures on the variation of springback amount at various die temperatures:(a)258C;(b)1008C;(c)2008C.368Y.H.Moon et al./Journal of Materials Processing Technology 132(2003)365–368。
Impact of temperature on chemical reactions
Impact of temperature on chemicalreactions随着气候变化的加剧，温度变化对化学反应的影响日益突显。
在这篇文章中，将探讨温度变化对化学反应的影响、温度与化学反应动力学参数之间的关系以及有关温度的实验设计和数据分析方法。
最后，将讨论如何利用这些信息来实现更有效的化学反应过程和更可持续的生产方式。
1. 温度对化学反应的影响温度是化学反应速率的最重要的因素之一。
热力学上，温度的提高会使反应物的反应自由能降低。
这意味着可以在更低的反应物浓度下实现更高的反应速率和更高的反应产率。
在实际应用中，这意味着可以使用更小的催化剂剂量、更低的反应温度和更短的反应时间来实现更高的化学反应效率。
2. 温度与化学反应动力学参数之间的关系根据阿累尼乌斯方程，反应速率常数k与温度T之间呈指数关系。
因此，反应速率常数随温度的升高而迅速增加。
然而，这并不意味着温度越高，反应速率越大。
随着温度继续上升，分子之间的碰撞会变得越来越频繁，而且分子的热能越来越高，从而导致分子分解并丢失它们可能已经获得的活性。
这种反应损失称为热分解。
因此，存在一个适当的反应温度，可以在其中实现最大的反应速率和最大的反应产率。
3. 有关温度的实验设计和数据分析方法在研究温度对化学反应的影响时，需要设计实验来控制反应温度，并记录反应速率和反应产物的浓度。
为了确定最佳的反应温度，可以使用Arrhenius方程来计算反应速率常数，并绘制不同温度下的反应速率常数随温度变化的图表。
这些数据可以用来计算反应的激活能，并使用线性回归分析来确定此数据的拟合度和预测温度下的反应速率常数。
4. 应用温度控制化学反应化学反应的有效控制和优化对于实现可持续生产和生产高质量产品至关重要。
利用温度控制策略可以有效地提高生产效率和减少有毒废物的产生。
例如，在制备液体燃料时，低温下的加热时间缩短，可以有效减少产生有害物质的可能性。
在制备医药品时，通过调整反应温度和时间，可以确保产品的纯度和质量符合标准。
埃克森美孚全面润滑解决方案应对非道路移动机械国四标准
ʌ３ɔＸＩＡＮＧＪ，ＺＨＡＮＧＺ．Ｓｌｉｄｉｎｇｗｅａｒｏｆｐｏｌｙｅｔｈｅｒｉｍｉｄｅｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｗｅａｒ，２００５，２５８（５／６）：７８３－７８８．ʌ４ɔＣＨＥＮＢＢ，ＷＡＮＧＪＺ，ＹＡＮＦＹ．ＣｏｍｐａｒａｔｉｖｅｉｎｖｅｓｔｉｇａｔｉｏｎｏｎｔｈｅｔｒｉｂｏｌｏｇｉｃａｌｂｅｈａｖｉｏｒｓｏｆＣＦ／ＰＥＥＫｃｏｍｐｏｓｉｔｅｓｕｎｄｅｒｓｅａｗａｔｅｒｌｕｂｒｉｃａｔｉｏｎ［Ｊ］．ＴｒｉｂｏｌｏｇｙＩｎｔｅｒｎａｔｉｏｎａｌ，２０１２，５２：１７０－１７７．ʌ５ɔ朱艳吉，陈晶，姜丽丽，等．组装改性碳纤维增强聚醚醚酮复合材料的摩擦学性能［Ｊ］．润滑与密封，２０１５，４０（８）：６１－６５．ＺＨＵＹＪ，ＣＨＥＮＪ，ＪＩＡＮＧＬＬ，ｅｔａｌ．ＴｈｅｔｒｉｂｏｌｏｇｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆＰＥＥＫｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙａｓｓｅｍｂｌｅｄｍｏｄｉｆｉｃａｔｉｏｎｏｆｃａｒｂｏｎｆｉｂｅｒ［Ｊ］．ＬｕｂｒｉｃａｔｉｏｎＥｎｇｉｎｅｅｒｉｎｇ，２０１５，４０（８）：６１－６５．ʌ６ɔ张志毅，章明秋，曾汉民．ＣＦ／ＰＥＥＫ复合材料的摩擦磨损行为研究［Ｊ］．中山大学学报（自然科学版），１９９６，３５（６）：１５－１８．ＺＨＡＮＧＺＹ，ＺＨＡＮＧＭＱ，ＺＥＮＧＨＭ．ＴｈｅｆｒｉｃｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆＰＥＥＫｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙｃａｒｂｏｎｆｉｂｅｒ［Ｊ］．ＡＣＴＡＳｃｉｅｎｔｉａｒｕｍＮａｔｕｒａｌｉｕｍＵｎｉｖｅｒｓｉｔａｔｉｓＳｕｎｙａｔｓｅｎｉ，１９９６，３５（６）：１５－１８．ʌ７ɔＦＲＩＥＤＲＩＣＨＫ，ＺＨＡＮＧＺ，ＳＣＨＬＡＲＢＡＫ．Ｅｆｆｅｃｔｓｏｆｖａｒｉｏｕｓｆｉｌｌｅｒｓｏｎｔｈｅｓｌｉｄｉｎｇｗｅａｒｏｆｐｏｌｙｍｅｒｃｏｍｐｏｓｉｔｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，２００５，６５（１５／１６）：２３２９－２３４３．ʌ８ɔＣＨＡＮＧＬ，ＦＲＩＥＤＲＩＣＨＫ．Ｅｎｈａｎｃｅｍｅｎｔｅｆｆｅｃｔｏｆｎａｎｏｐａｒｔｉｃｌｅｓｏｎｔｈｅｓｌｉｄｉｎｇｗｅａｒｏｆｓｈｏｒｔｆｉｂｅｒ⁃ｒｅｉｎｆｏｒｃｅｄｐｏｌｙｍｅｒｃｏｍｐｏｓ⁃ｉｔｅｓ：ａｃｒｉｔｉｃａｌｄｉｓｃｕｓｓｉｏｎｏｆｗｅａｒｍｅｃｈａｎｉｓｍｓ［Ｊ］．ＴｒｉｂｏｌｏｇｙＩｎ⁃ｔｅｒｎａｔｉｏｎａｌ，２０１０，４３（１２）：２３５５－２３６４．ʌ９ɔＪＩＡＮＧＺＹ，ＧＹＵＲＯＶＡＬＡ，ＳＣＨＬＡＲＢＡＫ，ｅｔａｌ．Ｓｔｕｄｙｏｎｆｒｉｃｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆｐｏｌｙｐｈｅｎｙｌｅｎｅｓｕｌｆｉｄｅｃｏｍｐｏｓｉｔｅｓｒｅｉｎｆｏｒｃｅｄｂｙｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒｓａｎｄｓｕｂ⁃ｍｉｃｒｏＴｉＯ２ｐａｒｔｉｃｌｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙ，２００８，６８（３／４）：７３４－７４２．ʌ１０ɔＬＩＮＧＭ，ＸＩＥＧＹ，ＳＵＩＧＸ，ｅｔａｌ．Ｈｙｂｒｉｄｅｆｆｅｃｔｏｆｎａｎｏｐａｒｔｉ⁃ｃｌｅｓｗｉｔｈｃａｒｂｏｎｆｉｂｅｒｓｏｎｔｈｅｍｅｃｈａｎｉｃａｌａｎｄｗｅａｒｐｒｏｐｅｒｔｉｅｓｏｆｐｏｌｙｍｅｒｃｏｍｐｏｓｉｔｅｓ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＰａｒｔＢ：Ｅｎｇｉｎｅｅｒｉｎｇ，２０１２，４３（１）：４４－４９．ʌ１１ɔＭＡＮ，ＬＩＮＧＭ，ＸＩＥＧＹ，ｅｔａｌ．Ｔｒｉｂｏｌｏｇｉｃａｌｂｅｈａｖｉｏｒｏｆｐｏｌｙ⁃ｅｔｈｅｒｅｔｈｅｒｋｅｔｏｎｅｃｏｍｐｏｓｉｔｅｓｃｏｎｔａｉｎｉｎｇｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒｓａｎｄｐｏｔａｓｓｉｕｍｔｉｔａｎａｔｅｗｈｉｓｋｅｒｓｉｎｄｒｙｓｌｉｄｉｎｇａｇａｉｎｓｔｓｔｅｅｌ［Ｊ］．ＪｏｕｒｎａｌｏｆＡｐｐｌｉｅｄＰｏｌｙｍｅｒＳｃｉｅｎｃｅ，２０１２，１２３（２）：７４０－７４８．ʌ１２ɔＧＵＯＱＢ，ＲＯＮＧＭＺ，ＪＩＡＧＬ，ｅｔａｌ．Ｓｌｉｄｉｎｇｗｅａｒｐｅｒｆｏｒｍａｎｃｅｏｆｎａｎｏ⁃ＳｉＯ２／ｓｈｏｒｔｃａｒｂｏｎｆｉｂｅｒ／ｅｐｏｘｙｈｙｂｒｉｄｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｗｅａｒ，２００９，２６６（７／８）：６５８－６６５．ʌ１３ɔＷＡＮＧＱＨ，ＺＨＡＮＧＸＲ，ＰＥＩＸＱ．Ｓｔｕｄｙｏｎｔｈｅｓｙｎｅｒｇｉｓｔｉｃｅｆｆｅｃｔｏｆｃａｒｂｏｎｆｉｂｅｒａｎｄｇｒａｐｈｉｔｅａｎｄｎａｎｏｐａｒｔｉｃｌｅｏｎｔｈｅｆｒｉｃ⁃ｔｉｏｎａｎｄｗｅａｒｂｅｈａｖｉｏｒｏｆｐｏｌｙｉｍｉｄｅｃｏｍｐｏｓｉｔｅｓ［Ｊ］．Ｍａｔｅｒｉａｌｓ＆Ｄｅｓｉｇｎ，２０１０，３１（８）：３７６１－３７６８．ʌ１４ɔＣＨＥＮＢＢ，ＬＩＸＦ，ＹＡＮＧＪ，ｅｔａｌ．Ｅｎｈａｎｃｅｍｅｎｔｏｆｔｈｅｔｒｉｂｏ⁃ｌｏｇｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｃａｒｂｏｎｆｉｂｅｒ／ｅｐｏｘｙｃｏｍｐｏｓｉｔｅｂｙｇｒａｆｔｉｎｇｃａｒｂｏｎｎａｎｏｔｕｂｅｓｏｎｔｏｆｉｂｅｒｓ［Ｊ］．ＲＳＣＡｄｖａｎｃｅｓ，２０１６，６（５５）：４９３８７－４９３９４．ʌ１５ɔＣＨＥＮＢＢ，ＬＩＸ，ＪＩＡＹＨ，ｅｔａｌ．ＭｏＳ２ｎａｎｏｓｈｅｅｔｓ⁃ｄｅｃｏｒａｔｅｄｃａｒｂｏｎｆｉｂｅｒｈｙｂｒｉｄｆｏｒｉｍｐｒｏｖｉｎｇｔｈｅｆｒｉｃｔｉｏｎａｎｄｗｅａｒｐｒｏｐｅｒ⁃ｔｉｅｓｏｆｐｏｌｙｉｍｉｄｅｃｏｍｐｏｓｉｔｅ［Ｊ］．ＣｏｍｐｏｓｉｔｅｓＰａｒｔＡ：ＡｐｐｌｉｅｄＳｃｉｅｎｃｅａｎｄＭａｎｕｆａｃｔｕｒｉｎｇ，２０１８，１０９：２３２－２３８．埃克森美孚全面润滑解决方案应对非道路移动机械国四标准由中国工程机械工业协会举办的 非道路移动机械四阶段排放标准（工程机械行业）交流研讨会 在无锡圆满举行㊂埃克森美孚作为协办单位，在研讨会上发表主旨演讲，解读国四排放标准对柴油发动机的影响，面对中国机械行业高质量发展的新时代新挑战，埃克森美孚的全面润滑解决方案将积极助力设备制造商及终端用户平稳度过国标更新的缓冲期，进一步实现节能减排，绿色发展㊂应国家生态环境部发布的‘＜非道路柴油移动机械污染物排放控制技术要求＞标准“要求，国四标准将于２０２２年１２月１日（５６０ｋＷ以下的发动机）正式开始实施㊂新国标的出台标志着行业对环保要求进一步收紧，节能减排在长远发展中的战略地位愈加重要㊂相比国三标准，国四标准最大的不同是３７ ５６０ｋＷ功率范围内的发动机都必须加装废气后处理设备㊂而润滑油中的硫㊁磷及硫酸盐灰分等成分会通过不同机制影响后处理系统的运作，影响排放㊂因此，行业需要更高标准的润滑油以提升和颗粒捕集器及催化剂的相容性㊂低ＳＡＰＳ（低硫㊁低磷㊁低灰分）将成为新标准颁布后非道路机械重要的选油标准㊂凭借１５０多年的专业积淀和行业洞察，埃克森美孚已率先推出了多款ＣＫ－４级别产品，构建出完善的产品线，为升级后的发动机及其尾气后处理系统提供更为优越的保护和杰出的性能，践行品牌对深耕中国市场的承诺㊂卓越的低温流动性㊁抗磨损及杰出的氧化稳定性能都帮助油品在多重严苛的工况下发挥出色，有效保护发动机的后处理系统，实现更长的换油周期㊂美孚黑霸王傲超５Ｗ－３０先进全合成润滑油在实际工况的节能测试中被证明相较原用油可节省油耗高达３ ０８％，同时可减少３ ０８％污染物排放量；美孚黑霸王合成级１０Ｗ－４０可在长达１０万公里的换油周期内提供卓越保护；美孚黑霸王超高级１５Ｗ－４０做到了抗磨性能的提升，其抗磨损保护性能比ＣＫ－４ＡＰＩ发动机测试要求高５０％㊂除了高质量的发动机润滑油，埃克森美孚也通过美孚优释达系列服务，为用户提供包括油品分析㊁换油服务等等的专业技术支持，帮助提升设备管理水平㊂同时，埃克森美孚还在液压油㊁润滑脂等领域为设备制造商及终端用户提供全方位润滑解决方案，为生产力添翼㊂９９２０２１年第４期㊀曹凤香等：纳米颗粒ＴｉＯ２和ＳｉＯ２对碳纤维／超高分子量聚乙烯复合材料力学和摩擦学性能的影响。
反应温度英语
反应温度英语Temperature is a fundamental physical property that describes the degree of heat or coldness in an environment or object. It is a measure of the average kinetic energy of the particles in a system and is central to the laws of thermodynamics. The concept of temperature is vital in various fields, including physics, chemistry, biology, and engineering, as it influences the rate of chemical reactions, the expansion and contraction of materials, and the behavior of living organisms.In the realm of physics, temperature plays a pivotal role in phase transitions, such as the melting of ice into water or the boiling of water into steam. These transitions occur at specific temperatures that are characteristic of the substances involved. For instance, water freezes at 0 degrees Celsius and boils at 100 degrees Celsius at standard atmospheric pressure. However, these values can change with variations in pressure, demonstrating the interplay between temperature and pressure.Chemistry is another domain where temperature is crucial. The rate of chemical reactions generally increases with temperature due to the increased energy that particles possess. This heightened energy results in more frequent and forceful collisions among molecules, thus increasing the likelihood of reactions. The relationship between temperature and reaction rates is quantified by the Arrhenius equation, which shows that a higher temperature typically leads to a higher reaction rate.Biological systems are also sensitive to temperature changes. Enzymes, which are proteins that catalyze biochemical reactions, have optimal temperature ranges in which they function most efficiently. Deviations from these ranges can lead to decreased enzyme activity and can affect metabolic processes. In humans and other warm-blooded animals, maintaining a stable internal temperature is essential for survival, as many physiological processes depend on a relatively constant temperature.Engineering applications often require precise temperature control. For example, in the manufacturing of electronic components, specific temperatures are necessary toensure proper function and reliability. Similarly, in the food industry, temperature control is critical for food preservation and safety, as it prevents the growth of harmful bacteria.The measurement of temperature is typically conducted using thermometers, which come in various types, including mercury, alcohol, digital, and infrared. Each type has its own range of accuracy and suitability for different environments. Temperature scales commonly used include Celsius, Fahrenheit, and Kelvin. The Kelvin scale is particularly significant in scientific contexts because it is an absolute temperature scale, starting at absolute zero, where all thermal motion ceases.In conclusion, temperature is an essential parameter that influences a wide array of natural and artificial processes. Understanding and controlling temperature is key to advancements in science and technology, as well as to the maintenance of life and health. Whether it's the vastness of space or the intricacies of the human body, temperature remains a constant factor in the equations that describe our universe.This article has explored the significance of temperature across various disciplines, emphasizing its impact and the necessity for accurate measurement and control. The interconnectivity of temperature with other physical properties and its universal presence in our daily lives underscores its importance as a fundamental concept in science. 。
负折射率隐身衣英文版
Ran Duan,1 Elena Semouchkina,2,* and Ravi Pandey1
1Leabharlann Abstract: The geometric optics principles are used to develop a unidirectional transmission cloak for hiding objects with dimensions substantially exceeding the incident radiation wavelengths. Invisibility of both the object and the cloak is achieved without metamaterials, so that significant widths of the cloaking bands are provided. For the preservation of wave phases, the λ-multiple delays of waves passing through the cloak are realized. Suppression of reflection losses is achieved by using half-λ multiple thicknesses of optical elements. Due to periodicity of phase delay and reflection suppression conditions, the cloak demonstrates efficient multiband performance confirmed by full-wave simulations.
同温层效应作文素材
同温层效应作文素材英文回答：The phenomenon of the temperature inversion, also known as the temperature inversion effect, is a meteorological phenomenon in which the temperature of the atmosphere increases with altitude in contrast to the normal decrease in temperature with altitude. This can lead to a variety of effects on the environment and weather patterns.One of the most well-known effects of the temperature inversion is the trapping of pollutants and smog near the surface of the Earth. When the air near the ground is cooler than the air above it, pollutants and particulate matter are unable to rise and disperse, leading to poor air quality and health issues for those living in affected areas.Another effect of the temperature inversion is its impact on weather patterns. In some cases, it can lead tothe formation of fog and low-lying clouds, as the coolerair near the ground becomes saturated with moisture. This can have implications for transportation and aviation, as visibility is reduced and travel becomes more hazardous.Additionally, the temperature inversion can also affect the dispersion of pesticides and other chemicals used in agriculture. When the inversion occurs, these chemicals can become trapped near the surface, leading to potential harm to both the environment and human health.Overall, the temperature inversion effect has significant implications for both the environment and human health, and it is important for meteorologists and environmental scientists to study and understand this phenomenon in order to mitigate its negative impacts.中文回答：同温层效应，也被称为温度逆转效应，是一种气象现象，指的是大气温度随着海拔的升高而增加，与正常情况下随着海拔升高而降低的温度相对立。
The Effect of Temperature on Protein Folding
The Effect of Temperature on ProteinFoldingProtein folding is a complex process critical to the function of every living organism. It is the process by which a linear sequence of amino acids is converted into a three-dimensional structure. The correct folding of a protein is necessary for it to perform its biological function, while misfolded proteins can lead to a variety of diseases. Temperature, as a physical parameter, affects the folding process of proteins in both trivial and fundamental ways.At the most superficial level, temperature can affect the overall stability of proteins. At low temperatures, proteins may become less stable, which could cause unfolding. On the other hand, at high temperatures, the molecular motion of proteins may increase and lead to denaturation - the permanent and irreversible unfolding of protein structures. Therefore, protein stability becomes fundamentally dependent on temperature.One way to measure the effects of temperature on protein folding is using a technique called differential scanning calorimetry (DSC). DSC is a widely used method to study protein folding and stability. Essentially, the technique measures the amount of heat a sample protein absorbs or loses during heating or cooling. The amount of energy absorbed or released by a protein during folding or unfolding is related to the stability of its structure. The temperature range over which the protein undergoes unfolding can help to determine the stability of the folded protein.Interestingly, some proteins are observed to undergo a sharp transition in their folding behavior as the temperature is increased. This phenomenon is known as a temperature-induced unfolding transition. The transition is likely the result of changes in the entropy of the protein's structure as the temperature increases. That is, as the temperature rises, the increasing thermal motion will cause the protein to become more disordered and transition from its structured state to the disordered state. This process can be mathematically described by the second law of thermodynamics.Despite the apparent advantages of performing experiments at high temperatures, these experiments are often challenging due to the difficulties in controlling the sample's thermal fluctuations. There are ways to mitigate these difficulties. For example, one can use modified experimental setups to increase the thermal stability of the sample, such as using high-pressure cells. An alternative approach is to use single-molecule techniques. These methods, such as single-molecule fluorescence, can provide a means to observe protein folding dynamics at practically any temperature.One can also look at temperature effects on protein folding from a comparative evolutionary perspective. The theoretical framework of evolutionary trade-offs suggests that genetic mutations that increase protein stability at one temperature will often cause protein destabilization at another. This assertion is supported by the observation that many thermophilic proteins (adapted to survive in high-temperature environments) have an overall less stable structure than mesophilic (adapted to moderate temperature) or psychrophilic (adapted to low-temperature) proteins. Similarly, some studies have suggested that proteins from insects, which have to survive significant temperature fluctuations, tend to be less stable than proteins from more stable environments.Overall, the effects of temperature on protein folding are complex and multifaceted. Given the significance of protein folding in biological systems, it is essential to continue to study the effects of temperature on this process to better understand the fundamental principles of protein folding and how they relate to disease, evolution, and other areas of biochemistry.。
The impact of temperature on chemical reactions
The impact of temperature on chemicalreactions温度对化学反应的影响化学反应是化学过程中最重要的一环，化学反应的发生往往需要一定的条件。
其中，最重要的条件之一是温度。
温度作为化学反应的重要参数之一，可以影响化学反应的速度、化学平衡等多种化学性质。
本文将从不同角度探讨温度对于化学反应的影响。
一、温度对化学反应速率的影响化学反应速率是指单位时间内反应物浓度的变化量。
在化学反应中，温度的改变对反应速率有着明显的影响。
一般而言，随着温度升高，反应速率也会随之增大。
这是因为温度升高会增加反应物分子的运动速度和撞击能量，从而使反应物分子之间发生碰撞的概率增加，化学反应的速率也就更高。
但是，当温度增加到一定程度时，反应速率将会开始减慢，这是因为高温下化学反应的物质分子速度过快，容易导致反应物分子的部分碎裂和析合，反应物降解导致反应消耗。
同时，高温下产生的自由基等反应物质越来越多，与其它反应物相互作用产生消耗。
因此，化学反应速率并非随着温度的增加而无限增加。
而是在增加至一定温度之后，开始减小。
二、温度对化学平衡的影响化学平衡是指化学反应向前和向后反应速率相等的状态。
在化学平衡下，反应物和生成物的浓度保持不变。
温度对于化学平衡的影响同样显著。
温度对酸碱反应、氧化还原反应、配位反应等各种反应类型中的平衡有着不同的影响。
以氢氧化钾的电离反应为例：KOH（aq）↔K+（aq）+OH-（aq）。
该反应的反应物中含有强碱和强酸，热力学上，其指向产物方向，即生成氢氧根离子和对应的金属离子（例如钾离子）。
在反应中添加温度，将会加快氢氧化钾的电离过程（强酸强碱易溶于热水），使九价钨酸根根离子逐渐变成威廉酸、孪晶钨酸铯等氢氧根离子、金属阳离子和水分子。
总的来说，温度对反应物的离解反应有推动效应，会促进反应物的转化为产物，使反应前进行。
在生物化学反应过程中，温度对大分子的改变，容易断裂形成小分子，此时的化学反应会增大。
Microstructure evolution and mechanical properties of
Microstructure evolution and mechanical properties of1 000 MPa cold rolled dual-phase steelZHAO Zheng-zhi(赵征志), JIN Guang-can(金光灿), NIU Feng(牛枫), TANG Di(唐荻), ZHAO Ai-min(赵爱民) Engineering Research Institute, University of Science and Technology Beijing, Beijing 100083, ChinaReceived 10 August 2009; accepted 15 September 2009Abstract: The microstructure evolution of 1 000 MPa cold rolled dual-phase (DP) steel at the initial heating stages of the continuous annealing process was analyzed. The effects of different overaging temperatures on the microstructures and mechanical properties of 1 000 MPa cold rolled DP steel were investigated using a Gleeble−3500 thermal/mechanical simulator. The experimental results show that ferrite recovery and recrystallization, pearlite dissolution and austenite nucleation and growth take place in the annealing process of ultra-high strength cold rolled DP steel. When being annealed at 800 ℃ for 80 s, the tensile strength and total elongation of DP steel can reach 1 150 MPa and 13%, respectively. The microstructure of DP steel mainly consists of a mixture of ferrite and martensite. The steel exhibits low yield strength and continuous yielding which is commonly attributed to mobile dislocations introduced during cooling process from the intercritical annealing temperature.Key words: cold rolled dual-phase steel; microstructure evolution; recrystallization; mechanical property; overaging temperature1 IntroductionAdvanced high-strength steels (AHSS) have been used in the automotive industry as a solution for the weight reduction, safety performance improvement and cost saving. Among them, the dual-phase (DP) steels, whose microstructure mainly consists of ferrite and martensite, are an excellent choice for applications where low yield strength, high tensile strength, continuous yielding, and good uniform elongation are required [1−4].The continuous annealing process to produce cold rolled DP steels typically has the following stages: heating to the intercritical temperature region, soaking in order to allow the nucleation and growth of austenite, slow cooling to the quench temperature, rapid cooling to transform the austenite into martensite, overaging, and air cooling. The amount and morphology of the constituents formed depend on such annealing parameters. The effects of the retained austenite, ferrite, and martensite morphologies on the mechanical behavior of DP steels have been intensively investigated[5−9]. As we all known, overaging treatment is an important process during the production of dual-phase steel. It can reduce the hardness of martensite and improve the comprehensive mechanical properties of DP steel [10−14].The purpose of the present research was to study the microstructure evolution of cold rolled DP steel at the initial heating stages of the continuous annealing process using a Gleeble simulator. At the same time, the effects of overaging temperature on the mechanical properties of DP steel were also studied. The microstructures of specimens simulated on a Gleeble simulator, were analyzed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).2 ExperimentalThe chemical compositions of the experimental steel (mass fraction, %) were: 0.14−0.17C, 0.40−0.60Si, 1.70−1.90Mn, 0.02−0.04Nb, 0.40−0.60Cr, ≤0.010P, ≤0.010S, 0.02−0.06Al and balance Fe. Firstly, experimental steels were smelted in a 50 kg vacuum induction furnace. After smelting, experimental steels were forged into 35 mm×100 mm×100 mm cubic samples. The forged slabs were reheated to 1 200 ℃and soaked for 1 h. The hot rolled thickness was 3.5 mm after 6 passes rolling. The finish rolling temperature was about 880 ℃. The coiling temperature was 620 ℃. After being pickled in hydrochloric acid, the hot rolledFoundation item: Project(2006BAE03A06) supported by the National Key Technology R&D Program during the 11th Five-Year Plan Period Corresponding author: ZHAO Zheng-zhi; Tel: +86-10-62332617; E-mail: zhaozhzhi@ZHAO Zheng-zhi, et al/Trans. Nonferrous Met. Soc. China 19(2009) s563−s568 s564bands were cold rolled to the final thickness of 1.0 mm, and the reduction was about 70%. Finally, the cold rolled sheets were cut into the samples for the simulation of continuous annealing experiment.The microstructure evolution at the initial steps of the continuous annealing process was studied using a Gleeble 1500 simulator. The steel was heated at 10 ℃/sto the different heating temperatures (550, 630, 670, 710, 730, 750 and 780 ℃) and held for 20 s followed by water-quenching. The effects of different overaging temperatures on the microstructures and mechanical properties of DP steel were investigated using a Gleeble 3500 simulator. The processing schedules and parameters used are shown in Fig.1. The soaking temperature of intercritical region was set at 800 ℃, soaking time is 80 s; after a slow cooling, the samples were rapidly cooled to 240, 280, 320 and 360 ℃, respectively and soaked for 300 s; at last, the samples were air cooled to the room temperature.Fig.1 Continuous annealing process of DP steelAfter heat treatment, the steel sheet would be cut into standard tensile specimens (length 200 mm, gauge length 50 mm). The tensile test was performed with CMT4105-type tensile test machine to test mechanical properties. The longitudinal cold rolling plane sections of samples after annealing were prepared and etched with 4% natal. The microstructure was analyzed by scanning electron microscopy (SEM). Some samples were analyzed using transmission electron microscopy (TEM).3 Results and discussion3.1 Mechanical properties and microstructures ofsamples after hot-rolling and continuousannealingTable 1 shows the tensile test data for the two samples after hot-rolling and continuous annealing in terms of yield strength, ultimate tensile strength and total elongation. When the annealing temperature is 800 ℃and soaking time is 60 s, the tensile strength reaches 1 110 MPa and the total elongation reaches 12%. Compared with the hot-rolled samples, the yield strength and total elongation of sample after annealing are similar, but the tensile strength increases by about 450 MPa. The yield ratio decreases obviously. The engineering uniaxial tensile stress—strain curve of the sample after continuous annealing is characterized by very uniform plastic flow until necking. There is no physical yield point and yield point extension, that is, the steel exhibits continuous yielding which is commonly attributed to mobile dislocations introduced during cooling from the intercritical annealing temperature. Many dislocation sources come into action at low strain and plastic flow begins simultaneously through the specimen, thereby suppressing discontinuous yielding[15].Table 1 Mechanical properties of samples after hot rolling and annealingConditionYieldstrength/MPaTensilestrength/MPaYieldratio*Totalelongation/% Hot rolling555 665 0.83 16 Annealing540 1110 0.49 12* Yield ratio is defined as the ratio of yield strength to tensile strength.The microstructures of the hot-rolled and cold-rolled samples are shown in Fig.2. It can be observed that hot rolled steel features a band microstructure, i.e. pearlite band in a ferrite grain matrix. The ferrite grain size is measured to be 5.0−9.0 µm. After cold rolling, the microstructure consists of elongated grains of ferrite and deformed colonies of pearlite (Fig.2(b)). After cold-rolling, there is an increase in the stored energy of the steel due to the high dislocation density and this provides the driving pressure for the ferrite recrystallization during annealing process. The total ferrite grain boundary area increases and the cementite laminar structure in pearlite is broken down. The latter has been shown to promote spheroidization of cementite during subsequent annealing process.The SEM micrograph of the sample after annealing is given in Fig.3(a). The microstructure of DP steel consists of a mixture of ferrite, martensite, martensite/austenite constituent. There is also some bainite in the microstructure. The martensite islands are homogeneously distributed in ferrite matrix. The DP steel has finer grain size and the size of ferrite grain and martensite island are about 1.0−2.0 µm. Some martensite islands have a bright white circle around the edge, and the center of martensite is of irregular black structure.ZHAO Zheng-zhi, et al/Trans. Nonferrous Met. Soc. China 19(2009) s563−s568 s565Fig.2 Microstructures of steel after hot rolling (a) and cold rolling (b)Fig.3 SEM images (a) and TEM micrograph (b) of steel after continuous annealingThe main reason is the manganese partitioning will occur during the continuous annealing process. During the heating process, a high-Mn side lap forms around austenite, which makes the hardenability of austenite island edge higher than that of the center. So, it makes high-Mn side lap form around martensite in the cooling process. The volume fraction of martensite is about 40%, which is the main reason for DP steel with a higher strength. After the continuous annealing process, band structure is significantly improved, which plays an important role in improving the performance of DP steel.The fine structures of martensite and ferrite are shown in Fig.3(b) by the TEM observation. The lath martensite is fine, and is relatively clean; at the same time, a very high density of dislocations can be observed in the ferrite grain adjacent to martensite. These dislocations are generated in order to accommodate transformation induced strain built between martensite transformed by quenching and retained ferrite. In addition, they are known to be mobile and play an important role on rapid, extensive strain hardening of DP steel from the onset of its plastic deformation.3.2 Microstructure evolution at initial steps ofcontinuous annealing processThe microstructure evolution at the initial stages of the continuous annealing process is very important for producing the ultra-high strength DP steel. During the annealing process of high strength DP steel, ferrite recovery and recrystallization, pearlite dissolution and austenite nucleation and growth will occur. When the sample is heated to 550 , the℃microstructure has no visible change as compared with the cold rolled sample. The ferrite grain is stretched along the rolling direction significantly; lamellar pearlite is stretched along the rolling direction too. At the same time, there are some carbide particles in the ferrite matrix, as shown in Fig.4(a). At this temperature, the recrystallization nucleus was not found in the structure. So, at this stage the sample is still at the recovery stage. When the heating temperature is 630 , the℃recrystallization nucleus begins to appear in the microstructure. The nucleus of crystal appears mainly nearby the large deformation ferrite (Fig.4(b)). The recrystallization nucleus is fine and equiaxed. Large deformation storage power is present in the large deformation region. So, recrystallization nucleus forms in this region firstly. With the heating temperature increasing, the recrystallization nucleus begins to grow. Therefore, the size of recrystallization is uneven at this stage, as shown in Fig.4(c). When the heating temperature is 670 ℃, the deformation structure still exists in the microstructure. With the temperature increasing, the deformed ferrite grains are replaced by recrystallization ferrite grains. When the heating temperature is 710 , the d℃eformation structure has already vanished, which is replaced by theZHAO Zheng-zhi, et al/Trans. Nonferrous Met. Soc. China 19(2009) s563−s568 s566equiaxed recrystallization grain. So, the process of recrystallization completes basically. In the ferrite recrystallization process, the pearlite transforms to granular from lamellar gradually.When the heating temperature is 730 ,℃it begins to enter the two-phase region; and the ferrite and spheroidised carbides begin to transform to austenite. A small amount of austenite nucleates in the original pearlite region, as shown in Fig.4(e). Austenite nucleates mainly in the ferrite and pearlite grain boundary; and a part of austenite also nucleates in the carbide particles of ferrite. After austenite nucleation, it begins to grow rapidly. At this stage, the pearlite dissolves rapidly. When the temperature reaches 750 , the austenite℃transformation occurs obviously. The bright white particle which distributes in the ferrite matrix is the martensite island. The martensite transforms from austenite during the rapid cooling process. At the same time, a small amount of martensite particles can also be observed in ferrite; and there are still some non-dissolved carbide particles in the ferrite matrix. The initial austenite growing-up is mainly controlled by the carbon Fig.4Microstructure evolutions duringcontinuous heating process: (a) 550 ℃; (b)630 ℃; (c) 670 ℃; (d) 710 ℃; (e) 730 ℃; (f)750 ℃; (g) 780 ℃ZHAO Zheng-zhi, et al/Trans. Nonferrous Met. Soc. China 19(2009) s563−s568 s567diffusion in the austenite, and the diffusion path is along the pearlite/austenite interface. When the annealing temperature is 780 , the austenite volume increase℃s, and the number of carbide particles is reduced gradually. There is only a very small amount of carbide particles distributing in ferrite matrix.3.3 Effect of overaging temperature onmicrostructure and mechanical properties ofDP steelThe overaging is a temper treatment to harden martensite in the dual-phase steel, reduce the hardness of martensite and improve the comprehensive mechanical properties[16]. Fig.5 shows the effect of overaging temperature on the mechanical properties of dual-phase steel. All the samples are intercritically annealed at 800℃ with different overaging temperatures. As can be seen from Fig.5, the highest tensile strength is achieved in the sample overaged at 280 ℃. The yield strength is 560 MPa, the tensile strength is 1 150 MPa, and the total elongation reaches 13%. The good combination of high strength and toughness properties is obtained. And then, with the increase of overaging temperature, the yield strength and tensile strength of samples decrease, while the total elongation increases. When the overaging temperature reaches 360 ℃, the tensile strength decreases, the yield strength does not change significantly. The mechanical properties of sample cannot meet the necessary requirements of CR980DP. At the same time, the stress—strain curve of the steel shows discontinuous yielding behaviour and develops yield plateaus.Fig.6 shows the SEM microstructures with different overaging temperatures. It can be seen that the microstructure mainly consists of dark grey ferrite grains and white martensite. When the overaging temperature is 360 ℃, the martensite boundary is fuzzier than that of sample overaged at 320 ℃, and there are more carbides, which is due to the effects of tempering on the martensite, such as the volume contraction of martensite during the tempering, the changes of the martensite strength and additional carbon clustering or precipitation near the ferrite and martensite interfaces.Fig.5 Effects of different overaging temperatures on mechanical propertiesFig.6 SEM images of microstructures of DP steel overaged at different temperatures: (a) 240 ℃; (b) 280 ℃; (c) 320 ℃; (d) 360 ℃ZHAO Zheng-zhi, et al/Trans. Nonferrous Met. Soc. China 19(2009) s563−s568 s5684 Conclusions1) When the DP steel is annealed at 800 ℃ for 80 s and overaged at 280 ℃, the tensile strength and total elongation of ultra-high strength dual-phase steel can reach 1 150 MPa and 13%, respectively.2) The microstructure of DP steel consists of a mixture of ferrite, martensite, martensite/austenite constituent. There are also some bainites in the microstructure. The martensite islands are homogeneously distributed in ferrite matrix. The ferrite and martensite island grain size are about 1.0−2.0 µm. When the overaging temperature reaches 360 ℃, the tensile strength decreases, the yield strength does not change significantly. The mechanical properties of sample cannot meet the necessary requirements of CR980DP. At the same time, the steel shows discontinuous yielding behaviour and develops yield plateaus.References[1]KANG Yong-lin. Quality control and formability of the mordernMotor plate [M]. Beijing: Metallurgical Industry Press, 1999.[2]LIU Peng, JIN Xian-zhe. The development and research ofautomobile steel plate [J]. Shanxi Metallurgy, 1997(2): 32−33.[3]MA Ming-tu, WU Bao-rong. Dual-phase steel-the physical andmechanical metallurgy [M]. Beijing: Metallurgical Industry Press,1988.[4]LLEWELLYN D T，HILLS D J. Dual phase steels [J]. Ironmakingand Steelmaking, 1996(6): 471−478.[5]SARKAR P P. Microstructural influence on the electrochemicalcorrosion behaviour of dual phase steels in 3.5% NaCl solution [J].Materials Letters, 2005(59): 2488−2491. [6]ROCHA R O, MELO T M F, PERELOMA E V, SANTOS D B.Microstructural evolution at the initial stages of continuous annealingof cold rolled dual-phase steel [J]. Materials Science and EngineeringA, 2005, 391: 296−304.[7]MA C, CHEN D L, BHOLE S D, BOUDREAU G, LEE A, BIRO E.Microstructure and fracture characteristics of spot-welded DP600 steel [J]. Materials Science and Engineering A, 2008, 485: 334−346.[8]SUN Shou-jin, Martin P. Manganese partitioning in dual-phase steelduring annealing [J]. Materials Science and Engineering A, 2000, 276: 167−174.[9]ZHU Xiao-dong, WANG Li. Effect of the continuous annealingparameters on the mechanical properties of cold rolled Si-Mn dualphase steel [C]//CSM 2003 Annual Meeting Proceedings, 2003: 684−688.[10]MOHAMMAD R A, EKRAMI A. Effect of ferrite volume fractionon work hardening behavior of high bainite dual phase (DP) steels [J].Materials Science and Engineering A, 2008, 477: 306−310.[11]HA VV A K Z, CEYLAN K, HUSEYIN A. Investigation of dual phasetransformation of commercial low alloy steels: Effect of holding timeat low inter-critical annealing temperatures [J]. Materials Letters, 2008, 62: 2651−2653.[12]DOU Ting-ting, KANG Yong-lin, YU Hao, KUANG Shuang, LIURen-dong, YAN Ling. Microstructural evolution of cold rolled dualphase steel during initial stages of continuous annealing [J]. Heat Treatment of Metal, 2008, 33(3): 31−35.[13]CHEN Hui-feng, ZHANG Qing-fen, AN Jia-shen. Recrystallizationcharacteristic of IF steel during rapid heating [J]. Journal of East China University of Metallurgy, 1999, 16(1): 21−23.[14]YANG D Z, BROWNEL E L, MATLOCK D K, et al. Ferriterecrystallization and austenite formation in cold rolled intercriticallyannealed steel [J]. Metallurgical Transactions A, 1985, 16A: 1385−391.[15]SULEYMAN G. Static strain ageing behaviour of dual phase steels[J]. Materials Science and Engineering A, 2008, 486: 63−71.[16]KUANG Shuang, KANG Yong-lin, YU Hao, LIU Ren-dong, YANLing. Experimental study on microstructure evolution in continuousannealing of cold-rolled dual phase steels [J]. Iron and Steel, 2007,42(11): 65−73.(Edited by CHEN Ai-hua)。
The effect of temperature on reaction rate
The effect of temperature on reaction rateDavid A-Level 2 Background informationWhen sodium thiosulphate reacts with hydrochloric acid, a precipitate of sculpture forms. The time taken for a certain amount if sculpture to form is used to measure the reaction rate. The sodium thiosulpahte solution can be heated to different temperatures before hydrochloric acid id added, so the effect of increasing temperature can be measured.The effect of temperature increase on this reaction can be predicted using the collision theory. This theory says that for a reaction to occur, particles must collide with a certain minimum energy called the activation energy, EA. When temperature is increased, particles have increased kinetic energy and move around faster. There is therefore an increase in the frequency of collisions.Procedure:1.Measure 10 cm*cm*cm of sodium thiosulphate solution and 40 cm*cm*cm of waterinto a conical flask.2.Measure 5 cm*cm*cm of dilute hydrochloric acid in a 10 cm*cm*cm measuringcylinder3.Warm the thiosulphate solution in the flask to the requires temperature4.Put the conical flask over a piece of paper with a cross drawn on it.5.Add the acid and start timing. Swirl the flask to mix the contents .Take the initialtemperature of the mixture and record it in a table like the one below.6.Repeat the experiment using different temperatures in the range 15℃ to 65℃.Remember that one of your experiments can be carried out at room temperature andAnalysis:The diagram increase higher because the temperature increases faster.ConclusionThe reaction rate increases when the temperature increases.。
退火温度对TiO_2薄膜光学性能的影响
ISSN 100020054CN 1122223 N 清华大学学报(自然科学版)J T singhua U niv (Sci &Tech ),2003年第43卷第11期2003,V o l .43,N o .111 36144121443退火温度对T i O 2薄膜光学性能的影响侯亚奇, 庄大明, 张 弓, 赵 明, 吴敏生(清华大学机械工程系,北京100084)收稿日期:2002212204基金项目:国家教育振兴计划资助项目作者简介:侯亚奇(19792),男(汉),陕西,博士研究生。
通讯联系人:庄大明,副教授,E 2m ail :dm zhuang @tsinghua .edu .cn摘 要:为确定合适的T i O 2薄膜退火工艺,研究了退火温度对采用中频交流反应磁控溅射技术制备的T i O 2薄膜光学性能的影响。
利用分光光度计测得石英玻璃基体T i O 2薄膜试样的透射谱和反射谱,用包络线法和经验公式法计算出薄膜的光学常数。
结果表明:T i O 2薄膜的折射率随退火温度的上升而增加,低温退火时薄膜消光系数略有减小,500℃退火时T i O 2薄膜具有最优的光学性能。
关键词:薄膜光学;T i O 2薄膜;中频交流磁控溅射;退火中图分类号:O 484.4+1文献标识码:A文章编号:100020054(2003)1121441203I nf luence of annea li ng tem pera ture onoptica l properties of titan iu mox ide th i n f il m sHOU Ya q i ,ZH UANG D am ing ,ZHANG Gong ,ZHAO M ing ,W U M insheng(D epart men t of M echan ical Eng i neer i ng ,Tsi nghua Un iversity ,Be ij i ng 100084,Chi na )Abstract :T heinfluence of annealingtemperature on op ticalp roperties of T i O 2th in fil m s p repared using the m id 2frequency A C m agnetron sputtering technique w as studied to design T i O 2thin fil m annealing p rocess .T he trans m ittance and reflectance spectra of T i O 2thin fil m s on fused silica substrate w ere m easured by a spectropho tom eter .T he reflective indices of the fil m s w erecalculated using the envelope m ethod and the extincti on coefficients w ere deter m ined using the emp irical fo rm ula m ethod .T he results show that the refractive index of the T i O 2th in fil m s increases w ith annealing temperature w hile the fil m extincti on coefficient decreases a little at low er annealing temperatures .T he T i O 2th in fil m annealed at 500℃has the best op tical p roperties .Key words :th infil mop tics;titaniumoxideth infil m;m id 2frequency A C m agnetron sputtering;annealing 对T i O 2薄膜的制备方法及性能已有深入研究[1,2]。
高温对药物有何影响呢英文
高温对药物有何影响呢英文The Effects of High Temperatures on MedicationsIntroduction: High temperatures can have significant effects on the stability and potency of medications. It is important to understand these effects in order to ensure the safety and efficacy of drugs. This document will discuss the impact of high temperatures on medications and provide recommendations for proper storage and handling under hot conditions.1. Degradation of Active Ingredients: High temperatures can lead to the degradation of active ingredients in medications. Many medications are sensitive to heat and can break down when exposed to elevated temperatures. This degradation can result in a loss of potency or even render the medication ineffective. It is crucial to store medications in a cool and dry place to prevent this degradation.2. Alteration of Physical Properties: In addition to the degradation of active ingredients, high temperatures can also alter the physical properties of medications. Heat can cause changes in the solubility, dissolution rate, and particle size of the drug, which can impact its absorption and bioavailability. This can lead to unpredictable drug responses and potentially compromise patient safety.3. Increased Risk of Contamination: Heat can increase the risk of contamination of medications. High temperatures can promote the growth of microorganisms, such as bacteria and fungi, in drug products. Contaminated medications can lead to serious infections and adverse reactions in patients. It is essential to store medications in a controlled environment to prevent microbial growth and maintain their sterility.4. Potential for Chemical Reactions: Certain medications are prone to undergo chemical reactions when exposed to high temperatures. For example, heat can cause the breakdown of certain drug molecules or facilitate the formation of new compounds, which may be toxic or have unpredictable effects on patients. Proper storage and handling of medications can help minimize the risk of these chemical reactions.5. Specific Medications and their Susceptibility to Heat: While all medications can be affected by high temperatures to some extent, certain drugs are more susceptible than others. For instance, insulin, certain antibiotics, and biologic medications are known to be highly sensitive to heat. It is vital to be aware of the specific storage requirements for each medication and follow the manufacturer's instructions accordingly.Recommendations: To ensure the efficacy and safety of medications, it is essential to follow proper storage and handling practices, especially under high-temperature conditions. Here are some recommendations:1. Store medications in a cool and dry place, away from direct sunlight and sources of heat.2. Avoid exposing medications to extreme temperatures, such as inside hot cars or near heating appliances.3. Check the storage instructions provided by the manufacturer for individual medications and adhere to them.4. If traveling with medications, use insulated containers or cool packs to maintain a constant temperature.5. Dispose of any medications that have been exposed to high temperatures, as their effectiveness may be compromised.Conclusion:High temperatures can cause numerous adverse effects on medications, including active ingredient degradation, alteration of physical properties, increased risk of contamination, and potential chemical reactions. Following proper storage and handling practices is essential to ensure the effectiveness and safety of medications, particularly in hot climates. It is crucial for healthcare professionals and patients to be aware of these effects and take necessary precautions to preserve the quality of medications.。
介绍冷凝现象英语作文
介绍冷凝现象英语作文English:The phenomenon of condensation occurs when a gas or vapor transforms into a liquid. This typically happens when the substance's temperature decreases to the point where it cannot support its gaseous form. The change occurs as the molecules of the substance lose kinetic energy and come closer together to form the liquid state. Condensation can be commonly observed in daily life, such as when the warm air from our breath meets the cold surface of a mirror, forming water droplets. It can also occur in natural phenomena like the formation of clouds, where water vapor in the air condenses to form droplets that eventually become rain. In industrial processes, condensation is often utilized as a method of purifying substances, separating mixtures, or recovering valuable products.Translated content:冷凝现象发生在气体或蒸气转化为液体的过程中。
高速滑坡动力学机理的研究1
同济大学博士后学位论文高速滑坡动力学机理的研究姓名：邢爱国申请学位级别：博士后专业：岩土工程指导教师：高广运20030601丹湃大学博士后研完工作报告高速滑坡动力学机理的研究邢ｔ因摘要高速滑坡是世界范围的问题。
高速滑坡能量人、速度快、滑程远，往往会给周同带来灾难性的斤果。
因此．高速滑坡形成机理及其动力学的研究成果无论是在基础研究方面，还娃在廊ｊ＿｝｛基础研究方面均属国内外滑坡研究的前沿课题。
本文基于流体动力学的观点，对高速滑坡的动力学机理进行了系统地研究．主要研究上作如Ｆ：１．按高速滑坡滑坡括动的时间和空间，划分为启程、近程和远程三个相互联系的活动阶段。
启程活动阶段滑坡体以高速滑动为主，近程话动阶段以凌空高速飞行为主，远穰活动阶段划以高速碎屑流运动为主。
因此，各个活动阶段都有各自不同的流体动力学现象。
２，系统地研究了不同试验条件下玄武岩表面摩擦系数的变化规律，探讨了玄武岩摩擦表面特性、滑动速度、法向压力等因素对摩擦系数的影响，取得了系统试验成果及不同情况卜＿相应的拟合方程式，为研究滑坡启程活动阶段剧滑高速机理提供了很有价值的依据。
３．详细地研究了高速滑坡启程活动阶段滑面瞬态温度场的变化规律，导出了滑面温度变化的方程式。
计算了头寨滑坡启程活动阶段由于强烈地高速摩擦产生热量的传导深度．进一步对头寨沟滑坡启程活动阶段滑带孔隙水汽化效应进行了研究。
４．首次采用理论分析和试验研究相结合的方法．系统地研究了高速滑坡近程活动阶段凌空Ｅ行的空气动力学效应。
在风洞模型试验研究的基础上。
提出了考虑地面效应时，高速滑体凌空ｂ行时间和飞行距离的计算公式。
５．研究发现远程活动阶高速滑坡的滑体都毫无例外的从有一定结构的岩体转变为流体化的湿碎屑流或干碎屑流。
湿碎屑流和干碎屑流都是二相流，而且是特殊的二相流。
高速运动的碎屑与空气二相混合体与周围空气之间产生复杂的空气动力学现象。
在滑体的前锋有高速运动的ｉ中击气浪，在碎屑流和地面之间有高速旋转向前的涡流作用，在高速运动的碎属颗粒之间还存在高速垂直向上流动的气流，使碎屑体的有效应力及其与地面之间的摩擦力显著降低。
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Abstract The effectof ceramicparticulateand graphiteadditionson the high temperaturedry slidingwearresistancenf two AI alloyswas studied. The experimentswereperformedusinga ring-on-flatslidingcontactconfigurationagainsthardenedSAE52100bearingsteelcounterfaceson an apparatusbuiltfor testingat controlledtemperatures.Conditionswereselectedsuchthatthe materialsin contactwerekept in an isothermal atmosphereand the generationof friedonalheat was minimisedby the use of a low load (11.55 N) and sliding speed (0.1 m s- i). For unreinforced6061 AI andA356A1alloysatransitionfrommildto severewearoccurredin the ranges175-190*(2and225-230 *(2respectively, With the additionof 20 vol.%A!203to 6061 AI, the mild to severeweartransitionwas raisedto a rangebetween310-350 °C. Likewise,an additionof 20 voi.% SiC to the A356AI increasedthis transitionto 441)-450°C. A hybridA356AI compositecontaining20 vol.%SiC and 10 vol.%graphiteremainedin a mild wearregimeat the highesttest temperatureof 460 °¢. All the reinforcedalloyswen: able to withstand considerablethermalsofteningeffectswhileremainingin a mildslidingweat regime.Thisis attributableto the formationof protectivetransfer layersof comminutedreinforcingparticulatesandtransferredsteeldebrisfromslidercounterfaces.Graphitein thehybridcompositeintroduced greatermild wearlossescomparedwiththe othercompositesdue to increasedfriabilityand contactsurfaceextrusioneffects.The absenceof severe wear phenomenain this compositecontributesto the inhibitionof comminutionand fracture by graphite entrainedin the surface tribulayer.
0043-1648196/$15.00 @ 1996 ElsevierScieaceS.A. All rightsieserved Pll S0043-1648 ( 96 ) 06923-2
higher speeds. Zhang and Alpas [3] observed a transition from mild to severe wear in AI2Osparticulate reinforced and unreinforced AI alloys when the friction induced heating of the sliding contact surfaces exceeded a critical temperature. The critical temperature for seizure was higher in the composite materials and occurred at greater loads than those for the unreinforced AI alloys. Martinez et al. [4] studied the wear properties of two A1--Sialloys ( AI-12% Si and AI-20% Si) and an AI-7% Si (A356 Al) alloy reinforced with 20 vol.% SiC particulates using an oscillating friction wear ~ester which had been equipped with a high temperature furnace. Ambient wear of these materials was characterised by the SiC reinforced alloy having the greatest wear resistance and showing no observable damage to the SiC reinforcing particulates. The two A1--Si alloys displayed comparatively lower wear resistances accompanied by transfer layer formarion of fragmented Si particles on their worn surfaces. The unreinforced A1-20% Si alloy and the SiC reinforced composite showed a transition from mild to severe wear at temperatures of IO0°C and 150"(2 respectively. Extensive
Keywords: SlБайду номын сангаасdingwear; Aluminiumcomposite;Graphite;Temperature
1, Introduction The developmentof AI alloys reinforced with discontinuous ceramic particulates and fibres has led to these materials finding application where features such as improved stiffhess/density ratios, strength/density ratios, thermal properties and wear resistance are of importance, particularly where energy consumptionis of primary concern. Examples involve high speed rotating or reciprocating mass items such as pistons, connecting rods, drive shafts, brake rotors and cylinder bores [ 1]. These components often operate at temperatures approaching 0.4Tin (where Tm is the.melting point of AI), where there is a danger of seizure during sliding contact should oil starvation or adverse operating conditions arise. The surface damage associated with frictional heating of steel sliding on copper, bismuth and tungsten surfaces at different speeds was examined by Bowden and Tabor [2]. Generally damage ranged between extensive abrasion and tearing at low sliding velocities (Cu), to large scale plasric flow (Cu), melting (Bi) or transfer and diffusion to the steel (W) at the
WEAR
ELSEVIER Wear 196 (1996) 270-278
Effect of temperature on the sliding wear performance of A1 alloys and A1 matrix composites
S. Wilson, A.T. Alpas
EngineeringMaterials Group, Departmentof Mechanicaland MaterialsEngineering, Universityof Windsor, Windsor, Ontario, Canada NgB EP4