表面质量外文文献翻译、中英文翻译

1、英文原文Surface qualitySurface quality is anther aspect of machining accuracy.it consists of the surface finish and the physico-mechanical state of the surface layer. It affects the proper functing and serveice life of the psrts.1. Surface finishMachining accuracy is expressed quantitatively in machinin

2、g error. Surface finish is expressed quantitatively in surface roughness. The surface roughness on a machined workpiece surface is caused primarily by the geometrical factors(cutting tool geometry and cutting feed),the plastic deformation of surface material, as the vibration of the MFTW system duri

3、ng machining.The surface roughness of a workpiece after machining depends upon many technological factors, such as the workpiece material,tool material, tool geometry, cutting condition (cutting speed and feed ), rigidity of the MFTW system, cooling conditonsin machining process, and so on. The surf

4、ace roghness is a kind of microgemetrical deviation or micro-irregularity of workpiece surface. It appears on all machined workpiece surface no matter how smooth they look to the eye.In regard to the criteria for eveluating surface roghness, refer to other textbooks, ISO, and other standards and ref

5、erences.The surface roghness of machined parts influences their performance to a great extent. In order to ensure product quality,to improve its service life, and to reduce its production cost, the surface roghness of machine parts has to be specified accurately in design and carefully controlled in

6、 manufacturing. 2.Physico-Mechanical Stae of Surface LayerIn machining process, the metal nearest the workpiece surface deforms plastically. This is due to the intrusion of the cutting tool rake to the workpiece surface material, the friction between the tool relife and the machined surface, and the

7、 effect of the tool nose radius. This results in the surface layer on the workpiece in quite a different way from the internal material of the workpiece after machining .until now, the evaluation of the physico-mechanical state of the surface layer is still in the experimental investigation stage. C

8、omplete standards for the evaluation do not exist .however, it is known that the variation of the material on the surface layer from the original metal are caused by cold hardening ,metallographical change, and residual stress.The cold hardening of the surface layer material is caused by plastic def

9、ormation of the material, resulting in the increase of its microhardness. The parameters which characterize the cold hardening are shown below:The hardened depth h , which is the depth of the surface layer, deformed plastically in the machining process.The microhardness H. The degree of cold hardeni

10、ng N , which is the ratio of the microhardness , increases the surface layer to the microhardness of the original metal, i.e, where stands for the microhardness of the original metal.A large part of the energy consumed in machining is transfomed into heat, which results in the inctease of the temper

11、ature in the cutting or grinding area, especially on the workpiece surface being machined. In general cutting processes, most of the hear generated is carried away by the temperature of the workpiece surface is not very high. However, in the machining processes consuming a very large amount of energ

12、y, for instance as in grinding , the temperature of the workpiece surface may reach or exceed the critical point or phase change of workpiece material. This codition causes the metallographical variation of the surface material.The residual stress is generated in the surface layer after machining. T

13、he causes of the generation of the residual stress are: (i) The material of the workpiece surface expands while it is heated by the cutting or grinding heat, and it contracts when it is cooled. The expansion and contraction are resisted by the internal material of the workpiece which results in the

14、residual tensilsstress in the surface layer after machining; (ii) The surface material plastically deforms under the extrusion and friction of the tool, while the internal material close to the surface layer elastically defoms. After machining, the recovery of the elastic deformation of the internal

15、 material is restricted by the surface material which has deformed plastically. This results in the residual stress, udually compressive residual stress, in the surface layer;(iii) The metallographical variation of the surface layer leads to its volume change, either expansion or contraction, which

16、is restricted by the internal material and result in the residual stress(compressive or tensile)in the surface layer.3.Infuluence of Surface Puality on the Performance of Machined PartsA field surface of a machined part caused by its wear, fatigue or corrosion, etc. ,starts from the part surface in

17、most case. The surface quality of a machine part greatly influences its performance, such as the fitting between parts, wear resistance, corrosion resistance, and fatigue strenght.4. Influence on Fitting between Parts The surface roghness influences directly the fitting condition between parts. For

18、the clearance fit, the existence of the micro-irregularities on part surface leads to a rapid initial wear. Thus the clearance increases between the parts which cause the deterioration of the fitting condition.As to the interference fit, the strengh of fit depends upon the surface roughness of the p

19、arts. When one part is press-fitted into another, the ridges of the micro-irregularities are extruded: This reduces the actual interference and thus the strength of fit. The actual interference can be calculated by the following equation:Where eactual interference maximum height of irregularities of

20、 shaft, repectively, maximum height of irregularities of hole, repectively, dimeter of shaft, dimeter of holeThe surface roughness and surface hardening influence greatly the wear resistance of part surfaces. When dry friction exists between two fitting surface, only the ridges of the irregularities

21、 on both surface are in contact with each other at the initial stage. The pressure between the two mating parts is concentrated on these small areas.For example, the actual contacting area for turned or milled surfaces is only 1520% of the total area, and for the finely ground surfaces, 3050% . Due

22、to the high unit pressure, the irregularities on the part surfaces defrom elastically and plastically and portions are sheared because of the relative movement of the surfaces. These fallen particles are scattered which intensify the wear between the contacting surfaces.The situation of the wet fric

23、tion is more complicated. At the initial stage of the wet friction the lubricant films are pierced through by the ridges of the roughness to from a dry friction between two fitting surfaces. The intensive initial wear changes the proper fit of the mating parts. However ,as the wear gradually increas

24、es ,the until pressure between the surfaces reduces, and the wear slows down. When a certain point is reached,the wear is intensified again.A resuction of the surface roughness can increasa the wear resistance of part surface. Howere, the relationship between them is not linear. It has been proved b

25、y experiments that an optimal value for the surface roghness exists under a given condition with which the minimum wear can be expected. If the fitting surface are too smooth, they will be in close contact with each other which leads to a larger affinity between the molecules of the surface. This wi

26、ll result in an intensive wear of surface.The hardening of the surface layer can greatly increase the wear resistance of part surface. However, an excessive increase of the microhardness may cause the peeling of the hardened layer. Therefore , caution should be exercised when applying microhardening

27、.5.Influence on Corrosion ResistanceThe surface roghness greatly influences the corrosion resistance of a part surface. Usually the corrodion subtances are gathered at the valleys of the surface micro-irregularities which will attack the part surface. The deeper and sharply defined the valleys betwe

28、en the ridges of microrregularities, the more destructive the effect of corrosion directed into the depth of the metal.The hardening of the surface layer and the existence of the residual stress in the surface layer will reduce the corrision resistance of the part surface. This is because the struct

29、ure of the surface layer after plastic deformation is in a non-equilibrium state, possessing higher energy. It is more prone to corrosion.6.Influence on Fatigue StrenghThe destructive failure of metal parts under slternate loads starts from part surface or under a certain depth of the hardened sufac

30、e. Consequently the fatigue strengh of a part depends upon the surface quality of the part to a great extent. Subject to periodically alternate load, the valleys between the ridges of surface micro-irregularities may become the points of internal stress concentration which may result in the failure

31、of the part. The higher the type finish, the higher the fatigue strength of the part.Cold hardening of the surface layer pevents the extension of existing microcracks. The generation of new microcracks on a part surface reduces the harmful effct of the surface roghness and the external defects of th

32、e part. This helps the increase of the fatigue strength. Howere , the excessive cold hadening of the surfce layer may intensify the extension of the microcracks. Under alternate load or high temperature, this decreases certain limits.The influence of the residual stress in surface layer on the fatig

33、ue strength of a part depends on the direction and the magnitude of the residual stress. The compressive residual stress tends to colse the microcracks and thus its existence can greatly increase the fatigue strength of the part. On the other hand , the existence of the tensile residual stress will

34、decrease the fatigue strength. However since the generation of the tensile residual stress is always accompanied with the hardening of the surface layer, this harmful effect is reduced.It can be seen from the above that the hardening of the surface layer and the existence of the compressive residual

35、 stress are conductive to the increase of the fatigue strength of parts. Appropriate methods can be adopted to generate hardening and compressive residual stresses in the surface layer,such as the ball peening, the burnishing, ect. Some heat-treatment methods, such as carbonizing and nitriding, can

36、also generate the compressive residual stress in the surface layer. In addition, some micro-finishing methods, such as polishing and vibrated finishing, ect. ,can be used to improve the surface finish, thus leading to the increase of the fatigue strength of parts.中文译文表面质量表面质量是机械加工精度的一方面，它包括表面粗糙度和表面层

37、物理机械状态。它影响了零件的使用性能和使用寿命。1、表面光洁度机械加工精度是用机械加工误差来定量表示的，表面光洁度是用表面粗糙度来定量表示的。一个已加工表面的表面粗糙度，主要由几何因素（刀具的几何形状和走刀量），材料表面的塑性变形，以及在机械加工过程中的MFTW系统的振动引起的。工件加工的表面粗糙度取决于许多技术因素，例如：工件的材料、刀具的材料、刀具的几何形状、切削条件（切削速度和走刀量）、MFTW系统的刚性、机械加工过程中的冷却条件，等等。表面粗糙度是工件表面的一种微观几何偏差或微观不规则性。不论用肉眼看起来是多么地光滑，它都会在已加工工件表面出现。参考其他课本，ISO标准和其他标准文献。

38、已加工零件的表面粗糙度在很大程度上影响它们的性能。为了确保零件质量，保证它服务寿命和降低零件成本，机器零件的表面粗糙度必须在设计过程中精确的规定和加工制造过程中仔细控制。2、表面层的物理机械状态在机械加工过程中，最靠近工件表面的金属产生塑性变形。这是由于刀具前刀面对工件表面材料的挤压。刀具后刀面与正加工表面之间的摩擦和刀尖半径的影响。这就导致机械加工后工件表面层与其心部材料处于完全不同的状态。直到现在，表层的物理机械状态评价仍然处于试验性的研究阶段。完整标准的评价是不存在的。然而，众所周知是从原始金属发生表面层材料冷作硬化、金相组织变化和残余应力引起的各种变化。表层材料的冷作硬化包括材料的塑性

39、变形，导致它的微观硬度的增加。表征冷作硬化的参数如下：硬化深度h ,它是表层材料在机械加工过程中塑性变形的深度。微观硬度H，冷作硬化程度N是指表层微观硬度的增量与原始金属微观硬度的比率，即：式中表示原始金属的微观硬度。机械加工过程中一部分的能量消耗用于热量转换，原因是切削或磨削区域的温度升高，尤其是正在加工的工件表面。一般在切削过程中产生的大部分热量被切屑带走，因此工件表面的温度不是很高。然而，在机械加工过程中也消耗了大量的能量，例如在磨削过程中，工件表面的温度可能达到甚至超过工件材料相变的临界点。这个因素导致了表面材料的金相组织变化。加工后的表面产生残余应力，其产生残余应力的原因是：1、在切

40、削或磨削时产生的热量使得工件表面材料膨胀，冷却时又会收缩。膨胀和收缩都会受到内部材料的限制，从而导致在机械加工后表面产生残余应力。2、材料的表面在刀具的挤压和摩擦下产生塑性变形，而紧挨着表面的内部材料发生弹性变形。加工后，内部材料的弹性变形的恢复又受到了已发生塑性变形的表面材料的限制。这就导致了表面的残余应力，通常产生的是表面层残余压应力。表面层的各种金相组织的变化导致了材料体积的改变，不论是延伸还是收缩都会受到内部材料的限制，并且导致了表面层残余应力（压和拉）的产生。3、表面质量对已加工零件性能的影响由于磨损、疲劳和腐蚀等原因引起的加工过的零件的现场失效，绝大多数情况都是从零件表面开始的。机器零件的表面质量极大地影响了它的性能，例如零件之间的配合、抗腐蚀性和疲劳强度。4、对零件之间配合的影响表面粗糙度直接地影响了零件的配合情况。对于间隙配合、零件表面上的微观不规则的存在导致了初期磨损的加速。从而使配对零件间的间隙增加同时引起了配合情况的恶化。对于过盈配合、配合强度、取决于零件的表面粗糙度。当一个零件被压进另一个零件时，微观不规则的波峰受到挤压；这就减小了实际过盈量，从而配合强度也会降低。实际