外文翻譯----機(jī)械加工表面質(zhì)量

1、<p>　　附錄1 外文翻譯（英文原文）</p><p>　　The Surface Quantity While Machine Processes</p><p>　　Abstract:The breakage of the machine spare parts, generally always from the surface layer beginning of.Th

2、e function of the product, particularly its credibility and durable, be decided by the quantity of the spare parts surface layer to a large extent.Purpose that studies the machine to process the surface quantity be for c

3、ontrol the machine process medium various craft factor to process the surface quantity influence of regulation, in order to make use of these regulations to control to process</p><p>　　Key word:The machine p

4、rocess the tired strength surface quantity remaining dint</p><p><b>　　Text:</b></p><p>　　A.the machine processes the surface quantity to use the influence of the function

5、to the machine</p><p>　　(A)The surface quantity to bear to whet the sexual influence</p><p>　　1. Rough degree of surface to bear to whet the sexual influence</p><p>　　A just process

6、 vice- of two contact surfaces of good friction, the first stage is rough only in the surface of of the peak department contact, the actual contact area is far small get in touch with the area in the theories, at mutuall

7、y get in touch with of department of peak have very big unit should dint, make actual contact area creation the mold transform, the flexibility transforms to shear to slice the breakage with of the department of peak , c

8、ause seriously wear away. </p><p>　　The spare parts wear away and can is divided into three stages generally, wearing away the stage, wearing away the stage normally in the early years and violent wear away

9、the stage. </p><p>　　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

10、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 ha

11、ve a the best value, it is worth to have something to do with the work circumstance of the spa</p><p>　　2. The surface is cold to make to harden to bear to whet the sexual influence</p><p>　　Pro

12、cess 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 col

13、d 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 surfac

14、e layer metals peeling off, make bear to whet sex to desc</p><p>　　(B)The surface influence of the quantity upon the tired strength</p><p>　　The tired breakage that metals produce after be subj

15、ected 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 s

16、trength very greatly. </p><p>　　1. The surface influence of the rough degree upon the tired strength</p><p>　　At hand over to change to carry the lotus function under, the surface part of the

17、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

18、 anti- tired breakage bottom ability is more bad. </p><p>　　2. Remaining dint, cold make to harden to the influence of the tired strength</p><p>　　Remaining dint is very big to the spare parts

19、 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

20、expand, defer tired breakage of creation. </p><p>　　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 a

21、lready has the crack to expand, to raise the tired strength beneficial. </p><p>　　(C) the surface quantity to bear the eclipse influence</p><p>　　The spare parts bears the eclipse to be decided

22、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. </p><p>　　Remaining of t

23、he 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 dec

24、ay open the rift . </p><p>　　(D)The surface quantity to match with the influence of the quantity</p><p>　　A size for be worth of surface will affect the match quantity of the match surface.Match

25、 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 p

26、ush even, actual lead the amount of over let up, lowering the match the conjunction strength of the a. </p><p>　　B. the influence surface factor of the rough degree</p><p>　　( A)Slice to pare t

27、o process to affect the surface factor of the rough degree</p><p>　　1. The knife has several shapes to reply to reflect</p><p>　　The knife have opposite make in to give exercise in the work pie

28、ce, at processed the surface to leave to slice to pare the layer to remain the area, its shape hour the knife has several the shape replies to reflect.Let up in to be partial to Cape for quantity, lord, vice- be partial

29、to the Cape and enlarge the point of a knife arc radius, all can let up the height of remain the area. </p><p>　　In addition, the mold that the ex- Cape that appropriate aggrandizement knife have slices by l

30、et up to pare transforms the degree, the reasonable choice lubricate the liquid and the exaltation knifes to have the mold that the blade whets the quantity to slice by let up to pare to transform and repress the knife l

31、ump, scale to stab born, also is let up a value of valid measure. </p><p>　　2. The property of a material of work</p><p>　　While processing the material of mold , have from the knife to produced

32、 the mold to transform to the squeeze of metals, the knife that add has to force to slice the tear to pieces of scraps and the work piece separate function, making a value of surface enlargement.A material of work tenaci

33、ty is more good, the mold of the metals transform more big, process the surface more rough. </p><p>　　While processing the brittleness material, it slices the scraps to present the broken pieces form, becaus

34、e of slicing the scraps to collapse ground but at process the surface to leave many points to order, make surface rough. </p><p>　　3. Slice to pare the dosage</p><p>　　(B)Whet to pare to process

35、 to affect the surface factor of the rough degree</p><p>　　Just be like to slice to pare to process the surface formation process of the rough degree, formation that whets to pare to process the rough degr

36、ee of surface also hour from several why plain transform with the mold of the surface metals to decide of. </p><p>　　The influence whets to pare the rough main factor of surface to have: The degree of hardne

37、ss, 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 sp

38、eed and stalks to enter to the quantity and cool off the lubrication liquid.</p><p>　　C. affect the factor of process the surface layer physics machine function</p><p>　　In slice pare process,

39、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 v

40、ariety 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 mo

41、ld produce transforms and slices to p</p><p>　　(A)The surface layer is cold to make the hardening</p><p>　　1. Cold make to harden and it assesses the parameter</p><p>　　The machine

42、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

43、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 enha

44、nce)The result that the surface layer metals enh</p><p>　　Drive cold make the unsteady appearance that the metals of the hardening is placed in the high ability, only have a probably, the unsteady appearance

45、 of the metals will convert toward more stable appearance, this kind of phenomenon is called to weaken.The size that weakens the function is decided by the temperature high and low, the temperature keeps on the length of

46、 time and enhances the size of the degree.Because the metals is in the function that the machine processes to be subjected to the d</p><p>　　Assess cold make the hardening of index sign have three, namely th

47、e show minute details of the surface layer metals degree of hardness HV, harden the layer depth h and harden the degree N. </p><p>　　2. Affect cold main factor that make to harden</p><p>　　Slice

48、 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 f

49、aces 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. </p><p>　　Slice to p

50、are 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 aggrandi

51、zement, 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

52、 layer the mold of the metals transforms to turn w</p><p>　　The mold of a material of work is more big, the cold and hard phenomenon is more serious. </p><p>　　(B)The surface layer material gol

53、d organizes the variety mutually</p><p>　　After slicing to pare the heat to make to be process the temperature of the surface exceeds to change the temperature mutually, the gold of the surface layer metals

54、organizes mutually and will take place the variety. </p><p>　　1. Whet to pare the burn</p><p>　　When were attained to change the temperature mutually by a surface of grinder layer temperature a

55、bove, the variety that the surface layer metals occurrence gold mutually organize, make the surface layer metals strength and degree of hardnesses lower, and the companion contain Residual stress should the dint produc

56、e, even appearing the tiny view crack, this kind of phenomenon is called to whet to pare the burn.While whetting to pare the quench steel, possible creation following three kinds of </p><p>　　2.Return to fir

57、e burn</p><p>　　If whet the temperature of pare the area and did not exceed the quench steel to change the temperature mutually, but have already exceeded MA3 ZHI TI3's change temperature, a surface laye

58、r of work metals returns to the fire MA3 ZHI TI3's organization and will change the degree of hardness return to the fire organization(Sorbite and Child's body) lowerly, this kind of burn is called to return to f

59、ire burn. </p><p>　　3.The quench burn</p><p>　　If whetted to pare the area temperature to exceed to change the temperature mutually, and cool off the nasty and cold function of the liquid, the s

60、urface layer metals take place fire of quench two times, make the surface layer metals appear two times quench Martensite organization, its degree of hardness compare originally return to fire Martensite of high, at it

61、s bottom layer, but the gooseflesh compare slowly, appeared the degree of hardness to compare to return to fire at first, Martensite </p><p>　　4.Back the fire burn</p><p>　　If whetted to pare th

62、e area temperature to exceed to change the temperature mutually, but whet to pare the district and did not cool off the liquid into, the surface layer metals will produce to back the fire organization, the surface degree

63、 of hardness descend nasty play, this kind of burn is called to back the fire burn. </p><p>　　2. The improvement whets the path of pare the burn</p><p>　　Whet to pare hot is a source that result

64、s in whet to pare the burn, the past improvement whets to pare the burn from two paths:While reducing to whet to pare the hot real estate to living possibly;Two is an improvement to cool off the condition, make produce t

65、he amount of subterranean heat as far as possible little stream into the work piece. </p><p>　　(C)The surface layer remaining should dint</p><p>　　1. Produce remaining of should the reason of th

66、e dint</p><p>　　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

67、 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 me

68、tals of arrestment, so produced in the surface metals layer Remaining dint, but produce t</p><p>　　b. Slice to pare to process medium, slice and pare the area and there will be to slice to pare the hot creat

69、ion in great quantities.</p><p>　　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 th

70、at 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 Rema

71、ining dint creation. </p><p>　　2. The end work preface of main work surface of spare parts processes the choice of method</p><p>　　The end work preface of main work surface of spare parts proces

72、ses 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. </p><p>　

73、　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. </p>

74、;<p>　　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 exten

75、sion, 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 sur

76、face should the dint process the method.</p><p><b>　　外文翻譯（譯文）</b></p><p><b>　　機(jī)械加工表面質(zhì)量</b></p><p>　　摘要：機(jī)械零件的破壞，一般總是從表面層開始的。產(chǎn)品的性能，尤其是它的可靠性和耐久性，在很大程度上取決于零件表面層的

77、質(zhì)量。研究機(jī)械加工表面質(zhì)量的目的就是為了掌握機(jī)械加工中各種工藝因素對(duì)加工表面質(zhì)量影響的規(guī)律，以便運(yùn)用這些規(guī)律來控制加工過程，最終達(dá)到改善表面質(zhì)量、提高產(chǎn)品使用性能的目的。 </p><p>　　關(guān)鍵字：機(jī)械加工 疲勞強(qiáng)度 表面質(zhì)量 殘余應(yīng)力</p><p><b>　　正文：</b></p><p>　　一、機(jī)械加工表面質(zhì)量對(duì)機(jī)器使用性能

78、的影響 </p><p>　?。ㄒ唬┍砻尜|(zhì)量對(duì)耐磨性的影響 </p><p>　　1. 表面粗糙度對(duì)耐磨性的影響 </p><p>　　一個(gè)剛加工好的摩擦副的兩個(gè)接觸表面之間，最初階段只在表面粗糙的的峰部接觸，實(shí)際接觸面積遠(yuǎn)小于理論接觸面積，在相互接觸的峰部有非常大的單位應(yīng)力，使實(shí)際接觸面積處產(chǎn)生塑性變形、彈性變形和峰部之間的剪切破壞，引起嚴(yán)重磨損。 </p&

79、gt;<p>　　零件磨損一般可分為三個(gè)階段，初期磨損階段、正常磨損階段和劇烈磨損階段。 </p><p>　　表面粗糙度對(duì)零件表面磨損的影響很大。一般說表面粗糙度值愈小，其磨損性愈好。但表面粗糙度值太小，潤滑油不易儲(chǔ)存，接觸面之間容易發(fā)生分子粘接，磨損反而增加。因此，接觸面的粗糙度有一個(gè)最佳值，其值與零件的工作情況有關(guān)，工作載荷加大時(shí)，初期磨損量增大，表面粗糙度最佳值也加大。 </p>

80、<p>　　2. 表面冷作硬化對(duì)耐磨性的影響 </p><p>　　加工表面的冷作硬化使摩擦副表面層金屬的顯微硬度提高，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，這是因?yàn)檫^分的冷作硬化將引起金屬組織過度疏松，甚至出現(xiàn)裂紋和表層金屬的剝落，使耐磨性下降。 </p><p>　?。ǘ┍砻尜|(zhì)量對(duì)疲勞強(qiáng)度的影響 </p><p>　　金屬

81、受交變載荷作用后產(chǎn)生的疲勞破壞往往發(fā)生在零件表面和表面冷硬層下面，因此零件的表面質(zhì)量對(duì)疲勞強(qiáng)度影響很大。 </p><p>　　1. 表面粗糙度對(duì)疲勞強(qiáng)度的影響 </p><p>　　在交變載荷作用下，表面粗糙度的凹谷部位容易引起應(yīng)力集中，產(chǎn)生疲勞裂紋。表面粗糙度值愈大，表面的紋痕愈深，紋底半徑愈小，抗疲勞破壞底能力就愈差。 </p><p>　　2. 殘余應(yīng)力、冷

82、作硬化對(duì)疲勞強(qiáng)度的影響 </p><p>　　余應(yīng)力對(duì)零件疲勞強(qiáng)度的影響很大。表面層殘余拉應(yīng)力將使疲勞裂紋擴(kuò)大，加速疲勞破壞；而表面層殘余應(yīng)力能夠阻止疲勞裂紋的擴(kuò)展，延緩疲勞破壞的產(chǎn)生。 </p><p>　　表面冷硬一般伴有殘余應(yīng)力的產(chǎn)生，可以防止裂紋產(chǎn)生并阻止已有裂紋的擴(kuò)展，對(duì)提高疲勞強(qiáng)度有利。 </p><p>　?。ㄈ?表面質(zhì)量對(duì)耐蝕性的影響 </p&

83、gt;<p>　　零件的耐蝕性在很大程度上取決于表面粗糙度。表面粗糙度值愈大，則凹谷中聚積腐蝕性物質(zhì)就愈多。抗蝕性就愈差。 </p><p>　　表面層的殘余拉應(yīng)力會(huì)產(chǎn)生應(yīng)力腐蝕開裂，降低零件的耐磨性，而殘余壓應(yīng)力則能防止應(yīng)力腐蝕開裂。 </p><p>　　（四）表面質(zhì)量對(duì)配合質(zhì)量的影響 </p><p>　　表面粗糙度值的大小將影響配合表面的配合質(zhì)

84、量。對(duì)于間隙配合，粗糙度值大會(huì)使磨損加大，間隙增大，破壞了要求的配合性質(zhì)。對(duì)于過盈配合，裝配過程中一部分表面凸峰被擠平，實(shí)際過盈量減小，降低了配合件間的連接強(qiáng)度。 </p><p>　　二、影響表面粗糙度的因素 </p><p>　　（一）切削加工影響表面粗糙度的因素 </p><p>　　1. 刀具幾何形狀的復(fù)映 </p><p>　　刀具

85、相對(duì)于工件作進(jìn)給運(yùn)動(dòng)時(shí)，在加工表面留下了切削層殘留面積，其形狀時(shí)刀具幾何形狀的復(fù)映。減小進(jìn)給量、主偏角、副偏角以及增大刀尖圓弧半徑，均可減小殘留面積的高度。 </p><p>　　此外，適當(dāng)增大刀具的前角以減小切削時(shí)的塑性變形程度，合理選擇潤滑液和提高刀具刃磨質(zhì)量以減小切削時(shí)的塑性變形和抑制刀瘤、鱗刺的生成，也是減小表面粗糙度值的有效措施。 </p><p>　　2. 工件材料的性質(zhì) &l

86、t;/p><p>　　加工塑性材料時(shí)，由刀具對(duì)金屬的擠壓產(chǎn)生了塑性變形，加之刀具迫使切屑與工件分離的撕裂作用，使表面粗糙度值加大。工件材料韌性愈好，金屬的塑性變形愈大，加工表面就愈粗糙。 </p><p>　　加工脆性材料時(shí)，其切屑呈碎粒狀，由于切屑的崩碎而在加工表面留下許多麻點(diǎn)，使表面粗糙。 </p><p><b>　　3. 切削用量 </b>

87、</p><p>　?。ǘ┠ハ骷庸び绊懕砻娲植诙鹊囊蛩?</p><p>　　正像切削加工時(shí)表面粗糙度的形成過程一樣，磨削加工表面粗糙度的形成也時(shí)由幾何因素和表面金屬的塑性變形來決定的。 </p><p>　　影響磨削表面粗糙的主要因素有： 砂輪的粒度、砂輪的硬度、砂輪的修整 、磨削速度 、磨削徑向進(jìn)給量與光磨次數(shù) 、工件圓周進(jìn)給速度與軸向進(jìn)給量 、冷卻潤滑液 。

88、</p><p>　　三、影響加工表面層物理機(jī)械性能的因素 </p><p>　　在切削加工中，工件由于受到切削力和切削熱的作用，使表面層金屬的物理機(jī)械性能產(chǎn)生變化，最主要的變化是表面層金屬顯微硬度的變化、金相組織的變化和殘余應(yīng)力的產(chǎn)生。由于磨削加工時(shí)所產(chǎn)生的塑性變形和切削熱比刀刃切削時(shí)更嚴(yán)重，因而磨削加工后加工表面層上述三項(xiàng)物理機(jī)械性能的變化會(huì)很大。 </p><p&

89、gt;　　（一）表面層冷作硬化 </p><p>　　1. 冷作硬化及其評(píng)定參數(shù) </p><p>　　機(jī)械加工過程中因切削力作用產(chǎn)生的塑性變形，使晶格扭曲、畸變，晶粒間產(chǎn)生剪切滑移,晶粒被拉長和纖維化，甚至破碎，這些都會(huì)使表面層金屬的硬度和強(qiáng)度提高，這種現(xiàn)象稱為冷作硬化(或稱為強(qiáng)化)。表面層金屬強(qiáng)化的結(jié)果，會(huì)增大金屬變形的阻力，減小金屬的塑性，金屬的物理性質(zhì)也會(huì)發(fā)生變化。 </p&

90、gt;<p>　　被冷作硬化的金屬處于高能位的不穩(wěn)定狀態(tài)，只有一有可能，金屬的不穩(wěn)定狀態(tài)就要向比較穩(wěn)定的狀態(tài)轉(zhuǎn)化，這種現(xiàn)象稱為弱化。弱化作用的大小取決于溫度的高低、溫度持續(xù)時(shí)間的長短和強(qiáng)化程度的大小。由于金屬在機(jī)械加工過程中同時(shí)受到力和熱的作用，因此，加工后表層金屬的最后性質(zhì)取決于強(qiáng)化和弱化綜合作用的結(jié)果。 </p><p>　　評(píng)定冷作硬化的指標(biāo)有三項(xiàng)，即表層金屬的顯微硬度HV、硬化層深度h和硬化

91、程度N。 </p><p>　　2. 影響冷作硬化的主要因素 </p><p>　　切削刃鈍圓半徑增大，對(duì)表層金屬的擠壓作用增強(qiáng)，塑性變形加劇，導(dǎo)致冷硬增強(qiáng)。刀具后刀面磨損增大，后刀面與被加工表面的摩擦加劇，塑性變形增大，導(dǎo)致冷硬增強(qiáng)。 </p><p>　　切削速度增大，刀具與工件的作用時(shí)間縮短，使塑性變形擴(kuò)展深度減小，冷硬層深度減小。切削速度增大后，切削熱在工件

92、表面層上的作用時(shí)間也縮短樂，將使冷硬程度增加。進(jìn)給量增大，切削力也增大，表層金屬的塑性變形加劇，冷硬作用加強(qiáng)。 </p><p>　　工件材料的塑性愈大，冷硬現(xiàn)象就愈嚴(yán)重。 </p><p>　　（二）表面層材料金相組織變化 </p><p>　　當(dāng)切削熱使被加工表面的溫度超過相變溫度后，表層金屬的金相組織將會(huì)發(fā)生變化。 </p><p>&

93、lt;b>　　1. 磨削燒傷 </b></p><p>　　當(dāng)被磨工件表面層溫度達(dá)到相變溫度以上時(shí)，表層金屬發(fā)生金相組織的變化，使表層金屬強(qiáng)度和硬度降低，并伴有殘余應(yīng)力產(chǎn)生，甚至出現(xiàn)微觀裂紋，這種現(xiàn)象稱為磨削燒傷。在磨削淬火鋼時(shí)，可能產(chǎn)生以下三種燒傷： </p><p><b>　　2.回火燒傷 </b></p><p>　　

94、如果磨削區(qū)的溫度未超過淬火鋼的相變溫度，但已超過馬氏體的轉(zhuǎn)變溫度，工件表層金屬的回火馬氏體組織將轉(zhuǎn)變成硬度較低的回火組織(索氏體或托氏體)，這種燒傷稱為回火燒傷。 </p><p><b>　　3.淬火燒傷 </b></p><p>　　如果磨削區(qū)溫度超過了相變溫度，再加上冷卻液的急冷作用，表層金屬發(fā)生二次淬火，使表層金屬出現(xiàn)二次淬火馬氏體組織，其硬度比原來的回火馬氏

95、體的高，在它的下層，因冷卻較慢，出現(xiàn)了硬度比原先的回火馬氏體低的回火組織(索氏體或托氏體)，這種燒傷稱為淬火燒傷。 </p><p><b>　　4.退火燒傷 </b></p><p>　　如果磨削區(qū)溫度超過了相變溫度，而磨削區(qū)域又無冷卻液進(jìn)入，表層金屬將產(chǎn)生退火組織，表面硬度將急劇下降，這種燒傷稱為退火燒傷。 </p><p>　　2. 改善

96、磨削燒傷的途徑 </p><p>　　磨削熱是造成磨削燒傷的根源，故改善磨削燒傷由兩個(gè)途徑：一是盡可能地減少磨削熱地產(chǎn)生；二是改善冷卻條件，盡量使產(chǎn)生地?zé)崃可賯魅牍ぜ?</p><p>　　（三）表面層殘余應(yīng)力 </p><p>　　1. 產(chǎn)生殘余應(yīng)力的原因 </p><p>　　a. 切削時(shí)在加工表面金屬層內(nèi)有塑性變形發(fā)生，使表面金屬的比

97、容加大。由于塑性變形只在表層金屬中產(chǎn)生，而表層金屬的比容增大，體積膨脹，不可避免地要受到與它相連的里層金屬的阻止，因此就在表面金屬層產(chǎn)生了殘余應(yīng)力，而在里層金屬中產(chǎn)生殘余拉應(yīng)力。 </p><p>　　b. 切削加工中，切削區(qū)會(huì)有大量的切削熱產(chǎn)生 。</p><p>　　c. 不同金相組織具有不同的密度，亦具有不同的比容。如果表面層金屬產(chǎn)生了金相組織的變化，表層金屬比容的變化必然要受到與之

98、相連的基體金屬的阻礙，因而就有殘余應(yīng)力產(chǎn)生。 </p><p>　　2. 零件主要工作表面最終工序加工方法的選擇 </p><p>　　零件主要工作表面最終工序加工方法的選擇至關(guān)重要，因?yàn)樽罱K工序在該工作表面留下的殘余應(yīng)力將直接影響機(jī)器零件的使用性能。 </p><p>　　選擇零件主要工作表面最終工序加工方法，須考慮該零件主要工作表面的具體工作條件和可能的破壞形式