外文翻译=机械加工表面质量=3500字文献翻译-毕业论文.doc

The Surface Quantity While Machine Processes

A.the machine processes the surface quantity to use the influence of the function to the machine
(A)The surface quantity to bear to whet the sexual influence
1. Rough degree of surface to bear to whet the sexual influence
The rough degree of surface is very big to the influence that the spare parts surface wear away.Say a value of surface generally more small, it wears away sex more good.But rough degree of surface the value is too small, lubricant not easy storage, contact of the noodles easy occurrence the member glues to connect, wearing away to increase on the contrary.Therefore, the rough degree that contact face have a the best value, it is worth to have something to do with the work circumstance of the spare parts, working to carry the lotus enlargement, wore away the quantity aggrandizement in the early years, rough degree of surface the best value also enlargement.
2. The surface is cold to make to harden to bear to whet the sexual influence
Process the surface cold to make to harden to make rub the vice- surface layer the metals of show minute details the degree of hardness exaltation, past can make bear to whet the sex exaltation generally.But is also not cold to make to harden the degree more high, bear to whet sex more high, this is because excessively cold make to harden and will cause the excesssive loose of the metals organization loose, even appear the crack and surface layer metals peeling off, make bear to whet sex to descend.
(B)The surface influence of the quantity upon the tired strength
The tired breakage that metals produce after be subjected to hand over to change to carry the lotus function usually takes place under the cold and hard layer of the spare parts surface and surfaces, therefore the surface quantity of the spare parts affects to the tired strength very greatly.
1. The surface influence of the rough degree upon the tired strength
At hand over to change to carry the lotus function under, the surface part of the cave valley of the rough degree causes easily should the dint concentration, produce the tired crack.A value of surface is more big, the crackle of the surface is more deep, the crackle bottom radius is more small, the anti- tired breakage bottom ability is more bad.
2. Remaining dint, cold make to harden to the influence of the tired strength
Remaining dint is very big to the spare parts influence of the tired strength.The surface layer remaining pull should the dint will make tired crack extend, accelerating the tired breakage;But the surface layer remaining should the dint can keep tired crack from expand, defer tired breakage of creation.
Surface the cold and hard general companion contain remaining of should the creation of the dint, can keep the crack creation from combine the arrestment already has the crack to expand, to raise the tired strength beneficial.
(C) the surface quantity to bear the eclipse influence
The spare parts bears the eclipse to be decided by the rough degree of surface to a large extent.A value of surface is more big, accumulating the causticity material in the then cave valley more many.The anti- eclipse is more bad.
Remaining of the surface layer pull should the dint will produce should the dint decay to open the rift , lower the spare parts to bear to whet sex, but Residual stress press should the dint then can prevent°from should dint decay open the rift .
(D)The surface quantity to match with the influence of the quantity
A size for be worth of surface will affect the match quantity of the match surface.Match with for the cleft, a value conference make wear away the enlargement, the cleft enlarge, the match property that break the request.For lead the over match, assemble process in a the convex peak of part of surfaces is push even, actual lead the amount of over let up, lowering the match the conjunction strength of the a.
B. the influence surface factor of the rough degree
(A)Slice to pare to process to affect the surface factor of the rough degree
1. The knife has several shapes to reply to reflect
2. The property of a material of work
3. Slice to pare the dosage
(B)Whet to pare to process to affect the surface factor of the rough degree
The influence whets to pare the rough main factor of surface to have: The degree of hardness, emery wheel of a degree, emery wheel of the emery wheel fix whole, whet to pare the speed and whet to pare the path to enter to whet number of times, the work a circumference for quantity and light to enter to the speed and stalks to enter to the quantity and cool off the lubrication liquid.
C. affect the factor of process the surface layer physics machine function
In slice pare process, the work piece because of being subjected to slice to pare the dint and slice the function of pare the heat, make the physics machine the function creation of the surface layer metals change, the variety of the most is variety and Residual stress s that the variety, gold that the surface layer metals shows minute details the degree of hardness organizes mutually should the creation of the dint.Because whetting to pare to process the mold produce transforms and slices to pare the hot ratio knife blade to slice to pare serious, as a result whet to pare to process to process behind the surface layer variety of above-mentioned three physicses machine function and would be very big.
(A)The surface layer is cold to make the hardening
1. Cold make to harden
The machine processes the process in because of slicing to pare the output mold of the dint function to transform, make the Crystal grain space distort, mutation, a creation shears to slice to slip to move, grain of Crystal grain drive make longer to turn with fiber, even broken up, these would make the surface layer metals of degree of hardnesses and strength raise, this kind of phenomenon be called cold make the hardening.( or be called to enhance)The result that the surface layer metals enhance, will enlarge the resistance that metals transform, let up the mold of the metals, the physical property of the metals also will take place the variety.
2. Affect cold main factor that make to harden
Slice to pare a radius of the blade bluntness to enlarge, to the squeeze of the surface layer metals function to build up, the mold transforms to turn worse, causing the cold and hard to build up.After knife have the knife faces to wear away the aggrandizement, empress the knife face with is process surface of friction turn worse, the mold transform the aggrandizement, causing the cold and hard to build up.
Slice to pare the speed aggrandizement, the knife has to shorten with function time of the work piece, making mold transform expand the depth to let up, the cold and hard layer depth let up.After slicing to pare the speed aggrandizement, slice to pare the heat on a surface of work layer of function time also shorten the joy, will make the cold and hard degree increment.Enter to enlarge for quantity, slice to pare the dint to also enlarge, surface layer the mold of the metals transforms to turn worse, the cold and hard function strengthen.
The mold of a material of work is more big, the cold and hard phenomenon is more serious.
(B)The surface layer remaining should dint
1. Produce remaining of should the reason of the dint
a. Slice to pare have the mold to transform the occurrence in process the surface metals layer, make the metal ratio of surface permit the enlargement.Because the mold transform only creation in the surface layer metals, but the ratio of the surface layer metals permits the aggrandizement, the physical volume inflation, the mile layer that want to be subjected to connect with each other with it inevitably metals of arrestment, so produced in the surface metals layer Remaining dint, but produce the remaining to pull in in the layer metals should dint.
b. Slice to pare to process medium, slice and pare the area and there will be to slice to pare the hot creation in great quantities.
c. The different gold organizes the density of have the dissimilarity mutually, also having the different ratio to permit.If the surface layer metals produced the variety that gold mutually organize, the variety that the surface layer metals compares to permit want to be subjected to by all means with its the bar of the base body metals for connect with each other, as a result there is Remaining dint creation.
2. The end work preface of main work surface of spare parts processes the choice of method
The end work preface of main work surface of spare parts processes the method to choose to the pass importance, because the end work preface is should work remaining of surface leave should the dint will affect the usage function of the machine parts directly.
Choose the main end work preface of surface of work of spare parts processes the method, must consider the concrete work condition and possible breakage forms of the surface of main work of that spare partses.
At hand over to change to carry the lotus function under, superficially partial tiny view crack of machine parts, meeting because of pull should the function of the dint make living at first the crack extension, causing spare parts split finally.The spare parts resists from the exaltation tired breakage of angle consider, the end work preface of that surface shoulds choose and can produce the remaining to press in that surface should the dint process the method.

机械加工表面质量

A、机械加工表面质量对机器使用性能的影响
（A）表面质量对耐磨性的影响
1. 表面粗糙度对耐磨性的影响
表面粗糙度对零件表面磨损的影响很大。一般说表面粗糙度值愈小，其磨损性愈好。但表面粗糙度值太小，润滑油不易储存，接触面之间容易发生分子粘接，磨损反而增加。因此，接触面的粗糙度有一个最佳值，其值与零件的工作情况有关，工作载荷加大时，初期磨损量增大，表面粗糙度最佳值也加大。
2. 表面冷作硬化对耐磨性的影响
加工表面的冷作硬化使摩擦副表面层金属的显微硬度提高，故一般可使耐磨性提高。但也不是冷作硬化程度愈高，耐磨性就愈高，这是因为过分的冷作硬化将引起金属组织过度疏松，甚至出现裂纹和表层金属的剥落，使耐磨性下降。
（B）表面质量对疲劳强度的影响
金属受交变载荷作用后产生的疲劳破坏往往发生在零件表面和表面冷硬层下面，因此零件的表面质量对疲劳强度影响很大。
1. 表面粗糙度对疲劳强度的影响
在交变载荷作用下，表面粗糙度的凹谷部位容易引起应力集中，产生疲劳裂纹。表面粗糙度值愈大，表面的纹痕愈深，纹底半径愈小，抗疲劳破坏底能力就愈差。
2. 残余应力、冷作硬化对疲劳强度的影响
余应力对零件疲劳强度的影响很大。表面层残余拉应力将使疲劳裂纹扩大，加速疲劳破坏；而表面层残余应力能够阻止疲劳裂纹的扩展，延缓疲劳破坏的产生。
表面冷硬一般伴有残余应力的产生，可以防止裂纹产生并阻止已有裂纹的扩展，对提高疲劳强度有利
（C)表面质量对耐蚀性的影响
零件的耐蚀性在很大程度上取决于表面粗糙度。表面粗糙度值愈大，则凹谷中聚积腐蚀性物质就愈多。抗蚀性就愈差。
表面层的残余拉应力会产生应力腐蚀开裂，降低零件的耐磨性，而残余压应力则能防止应力腐蚀开裂。
（D）表面质量对配合质量的影响
表面粗糙度值的大小将影响配合表面的配合质量。对于间隙配合，粗糙度值大会使磨损加大，间隙增大，破坏了要求的配合性质。对于过盈配合，装配过程中一部分表面凸峰被挤平，实际过盈量减小，降低了配合件间的连接强度。
B、影响表面粗糙度的因素
（A）切削加工影响表面粗糙度的因素
1. 刀具几何形状的复映
2. 工件材料的性质
3. 切削用量
（B）磨削加工影响表面粗糙度的因素
影响磨削表面粗糙的主要因素有： 砂轮的粒度、砂轮的硬度、砂轮的修整 、磨削速度 、磨削径向进给量与光磨次数 、工件圆周进给速度与轴向进给量 、冷却润滑液 。
C、影响加工表面层物理机械性能的因素
在切削加工中，工件由于受到切削力和切削热的作用，使表面层金属的物理机械性能产生变化，最主要的变化是表面层金属显微硬度的变化、金相组织的变化和残余应力的产生。由于磨削加工时所产生的塑性变形和切削热比刀刃切削时更严重，因而磨削加工后加工表面层上述三项物理机械性能的变化会很大。
（A）表面层冷作硬化
1. 冷作硬化

机械加工过程中因切削力作用产生的塑性变形，使晶格扭曲、畸变，晶粒间产生剪切滑移,晶粒被拉长和纤维化，甚至破碎，这些都会使表面层金属的硬度和强度提高，这种现象称为冷作硬化(或称为强化)。表面层金属强化的结果，会增大金属变形的阻力，减小金属的塑性，金属的物理性质也会发生变化。
2. 影响冷作硬化的主要因素
切削刃钝圆半径增大，对表层金属的挤压作用增强，塑性变形加剧，导致冷硬增强。刀具后刀面磨损增大，后刀面与被加工表面的摩擦加剧，塑性变形增大，导致冷硬增强。
切削速度增大，刀具与工件的作用时间缩短，使塑性变形扩展深度减小，冷硬层深度减小。切削速度增大后，切削热在工件表面层上的作用时间也缩短乐，将使冷硬程度增加。进给量增大，切削力也增大，表层金属的塑性变形加剧，冷硬作用加强。
工件材料的塑性愈大，冷硬现象就愈严重。
（B）表面层残余应力
1. 产生残余应力的原因
a. 切削时在加工表面金属层内有塑性变形发生，使表面金属的比容加大。由于塑性变形只在表层金属中产生，而表层金属的比容增大，体积膨胀，不可避免地要受到与它相连的里层金属的阻止，因此就在表面金属层产生了残余应力，而在里层金属中产生残余拉应力。
b. 切削加工中，切削区会有大量的切削热产生 。
c. 不同金相组织具有不同的密度，亦具有不同的比容。如果表面层金属产生了金相组织的变化，表层金属比容的变化必然要受到与之相连的基体金属的阻碍，因而就有残余应力产生。
2. 零件主要工作表面最终工序加工方法的选择
零件主要工作表面最终工序加工方法的选择至关重要，因为最终工序在该工作表面留下的残余应力将直接影响机器零件的使用性能。
选择零件主要工作表面最终工序加工方法，须考虑该零件主要工作表面的具体工作条件和可能的破坏形式。
在交变载荷作用下，机器零件表面上的局部微观裂纹，会因拉应力的作用使原生裂纹扩大，最后导致零件断裂。从提高零件抵抗疲劳破坏的角度考虑，该表面最终工序应选择能在该表面产生残余压应力的加工方法。

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