外文翻譯--影響工件表面質(zhì)量的因素

1、<p><b>　　英文原文</b></p><p>　　Influence factors on the quality of the workpiece surface</p><p>　　Processing process on the surface quality of the influence</p><p>　　Th

2、e vibration of the process system of the influence on the quality of the surface</p><p>　　In mechanical processing process technology system sometimes occur vibration, that is, in the cutting edge tool and w

3、orkpiece is cutting surface except on the name between cutting motion, but also can appear a cyclical relative motion.</p><p>　　Vibration that process system by forming movement of the interference and damag

4、e, make processing surface appear chatter marks, increases the surface roughness value, worsening processing surface quality.</p><p>　　Cutter geometrical parameters, materials and cutting quality to the surf

5、ace quality of the influence</p><p>　　The cutting tool geometric parameters on the surface roughness of the biggest influence is vice PianJiao, the main point PianJiao, arc radius. Under certain conditions,

6、reduce PianJiao, Lord, vice PianJiao point arc radius can reduce surface roughness. Under the same conditions, carbide cutting tools process of surface roughness value less than high speed steel paper cutting knife, and

7、diamond and CBN) tools and better than hard alloy, but because the diamond and iron family affinity materials, </p><p>　　Cutting fluid to the influence on the quality of the surface</p><p>　　Cut

8、ting fluid cooling and lubrication effect can reduce the cutting process of interface friction, reduce the temperature of cutting zone, the cutting metal surface layer of plastic deformation degree down, restrain the dev

9、elop the thorn and scales produced in the production of different materials for reasonable choice of cutting fluids can reduce the surface roughness.</p><p>　　The workpiece material on the surface quality of

10、 the influence</p><p>　　The workpiece material nature; Processing plastic materials, the cutting tools for metal extrusion produced plastic deformation, and the cutting tool and workpiece forced separation o

11、f the torn scraps effect, make the surface roughness value increase. The workpiece material tenacity the better, metal, plastic deformation, the bigger the processing surface is the more the rough. Processing brittle mat

12、erial in the chip broken granular, due to the collapse in broken and endows the machined surface </p><p>　　General toughness large plastic materials, processing after large surface roughness, and toughness o

13、f smaller plastic materials, processing to get smaller after the surface roughness. For the same kind of material, the greater the grain size of the organization, the larger the surface roughness. Therefore, in order to

14、reduce the surface roughness, often in cutting processing of material before quenching and tempering or is the fire of treatment to obtain homogeneous fine grain organization and h</p><p>　　Cutting condition

15、 the influence on the quality of the surface</p><p>　　And cutting condition of the relevant process factors, including cutting dosages, cooling lubrication. In low speed processing plastic materials,, easy t

16、o produce the devolop and scales thorn, so, improve the cutting speed, can reduce the devolop and scales thorn, decreasing part already the surface roughness value; For brittle material, general won't form the devolo

17、p and scales thorn, so, cutting speed on the surface roughness basically no influence. The increase speed, plastic deformation also</p><p>　　Cutting speed on the surface roughness influence</p><p&

18、gt;　　General at the early choose low speed cutting and finishing choose high speed cutting can reduce the surface roughness. In the medium speed cutting plastic materials, due to easy to produce the devolop, and plastic

19、deformation is bigger, so after processing parts surface roughness is bigger. Usually by low or high speed cutting plastic material, can effectively avoid the devolop of generation, this to reduce table and roughness hav

20、e positive role.</p><p>　　On the surface quality of the grinding effects</p><p>　　The influence of the grinding wheel grinding wheel granularity the thinner, per unit area grain number grinding,

21、 the more of the grinding surface in fine scratches the surface roughness is small; But if too fine granularity, processing to jam wheel it will increase the surface roughness, also easy to produce the ripple and cause b

22、urns. The hardness of the grinding wheel should be the right size, its half the longer the better passivation period; The hardness of the grinding wheel is too high, gr</p><p>　　The influence of the grinding

23、 wheel speed increase dosage, unit time through the processing of grinding surface grain number increase, each star grits is ground to reduce thickness of the metal, the surface area of the residual reduced; And at the s

24、ame time, improve the grinding wheel speed can also reduce the workpiece material of plastic deformation, these can make processing surface roughness value reduced. Reduce the speed, unit time through the processing of g

25、rinding surface grain number in</p><p>　　The workpiece material the workpiece material of hardness, plastic and thermal conductivity on the surface roughness of big effect. Large plastic soft material easy j

26、am grinding wheel, thermal conductivity poor heat resistant alloy easy for the abrasive early caving, will lead to increased grinding surface roughness.</p><p>　　In addition, because grinding to the high tem

27、perature, reasonable use cutting fluids can reduce the grinding of temperature, reduce burns, can also rushed to fall off the grits and scraps, avoid scratch workpiece, so as to reduce the surface roughness.</p>&

28、lt;p>　　Affect the surface of physical and mechanical properties of factors</p><p>　　Surface layer cold hardening. The cutting edges obtuse radius increased, and the surface of metal the extrusion of enhan

29、ced, plastic deformation intensifies, cold hard to strengthen. After cutting tool knife surface wear increases, the knife surface and after processed surface friction intensified, plastic deformation increase, cold hard

30、to strengthen. Cutting speed increase, cutting tool and workpiece role time is shortened, make plastic deformation expand the depth decreases, and cold hard lay</p><p>　　Surface layer material metallographic

31、 composition change. When cutting the heat was processing surface temperature of phase change after more than temperature, the surface of the metal microstructure will change. Grinding burns when a surface temperature of

32、 phase change to millers temperature above, metal surface microstructure occurred change, make the surface of the metal strength and hardness of the lower, and with residual stress produce appear even microscopic cracks,

33、 this phenomenon is cal</p><p>　　Surface layer residual stress. Produce residual stress of reason: cutting in processing the metal layer and the surface when there were plastic deformation occurs, the surfac

34、e of the metal to hematocrit increase; Cutting processing, cutting area will have a lot of heat cutting produce; Different analysis of metallographic organization has different density, also have different olume is neces

35、sarily affected by the change of connected the matrix of the metal bar, hence residual stress produce. The</p><p>　　Grinding surface layer analysis of metallographic organization changes and grinding burns&l

36、t;/p><p>　　Mechanical processing produces in the process of heat cutting processing surface of workpiece will make the rise of temperature of the violently, when the temperature more than the workpiece material

37、 metallographic organization changes of the critical temperature, metallographic organization change will occur. In grinding processing, because most grits before cutting Angle is negative, grinding temperature is high,

38、the quantity of heat of generation is much higher than cutting calories at, and g</p><p>　　Grinding hardened steel, workpiece surface layer due to the role of the instantaneous heat, it may produce the follo

39、wing three metallographic organization changes:</p><p>　　If grinding surface layer temperature not over phase transition temperature, but more than martensite transition temperature, then martensite will cha

40、nge to become low hardness of tempering methods, and meanwhile body or body, this call tempering burns.</p><p>　　If grinding surface layer temperature more than phase transition temperatures, the martensite

41、transformation for austenitic, at this time without cutting fluids, the grinding surface hardness fell sharply, surface was annealing, this phenomenon is called annealing burns. When dry grinding is easy to produce this

42、kind of phenomenon.</p><p>　　If grinding surface layer temperature more than phase transition temperature, but have the full cutting fluid on the cooling, the grinding surface layer will be urgent cold formi

43、ng secondary hardened martensitic, hardness than tempering martensite high, but the surface layer is very thin, and only a few microns thick, under which the low hardness for tempering saxhlet body and saxhlet body, make

44、 the surface layer general hardness still reduce, called quenching burns.</p><p>　　Grinding burns improvement measure</p><p>　　Influence factors of grinding burns is grinding dosage, grinding wh

45、eel, the workpiece material and cooling conditions. Because grinding heat caused by grinding burns is the root cause of, because this wants to avoid grinding burns, should as far as possible to reduce the heat generated

46、when grinding and decrease as far as possible to the quantity of heat of workpiece. Specific can adopt the following measures:</p><p>　　Choosing grinding reasonable dosage cannot use the too big grinding dep

47、th, because when grinding depth increases, the plastic deformation is increased, the surface layer and the temperature will increase, burns will also increase; The speed increase, a surface temperature will increase grin

48、ding zone, but due to the hot action time reduced, so can reduce the burn.</p><p>　　The workpiece material the workpiece material grinding zone of the influence of the temperature of depends primarily on its

49、 hardness and strength, toughness and thermal conductivity. The workpiece material hardness, the higher the strength, toughness, the bigger the grinding work when the more consumption, the quantity of heat that produced

50、the more, the easy generation burns; Thermal conductivity of poor material, also easy to appear in the grinding burns.</p><p>　　The choice of high hardness of the grinding wheel grinding wheel, passivated gr

51、its is not easy to fall off, easy to produce burns, so with soft grinding wheel is better; Choose coarse granularity grinding wheel grinding, not easily by grinding wheel grinding jams, can reduce burned; Combine agent o

52、f grinding burns also has a great influence, resin combination agent than ceramic combination agent easy to produce burns, rubber binder than resin binder are more likely to have burned.</p><p>　　Cooling con

53、ditions for reduction in grinding of temperature, widely used in this cutting liquid cooling. In order to make cutting fluids can injection to the surface, usually the cutting fluid flow increase.</p><p><

54、;b>　　中文譯文</b></p><p>　　影響工件表面質(zhì)量的因素</p><p>　　加工過程對表面質(zhì)量的影響</p><p>　　工藝系統(tǒng)的振動對工件表面質(zhì)量的影響</p><p>　　在機(jī)械加工過程中工藝系統(tǒng)有時會發(fā)生振動，即在刀具的切削刃與工件上正在切削的表面之間除了名義上的切削運(yùn)動之外，還會出現(xiàn)一種周期性的相對

55、運(yùn)動。</p><p>　　振動使工藝系統(tǒng)的各種成形運(yùn)動受到干擾和破壞，使加工表面出現(xiàn)振紋，增大表面粗糙度值，惡化加工表面質(zhì)量。</p><p>　　刀具幾何參數(shù)、材料和刃磨質(zhì)量對表面質(zhì)量的影響</p><p>　　刀具的幾何參數(shù)中對表面粗糙度影響最大主要是副偏角、主偏角、刀尖圓弧半徑。在一定的條件下，減小副偏角、主偏角、刀尖圓弧半徑都可以降低表面粗糙度。在同樣條件

56、下，硬質(zhì)合金刀具加工的表面粗糙度值低于高速鋼刀具，而金剛石、立方氮化硼刀具又優(yōu)于硬質(zhì)合金，但由于金剛石與鐵族材料親和力大，故不宜用來加工鐵族材料。另外，刀具的前、后刀面、切削刃本身的粗糙度直接影響加工表面的粗糙度，因此，提高刀具的刃磨質(zhì)量，使刀具前后刀面、切削刃的粗糙度值應(yīng)低于工件的粗糙度值的1~2級。 </p><p>　　切削液對表面質(zhì)量的影響</p><p>　　切削液的冷

57、卻和潤滑作用能減小切削過程中的界面摩擦，降低切削區(qū)溫度，使切削層金屬表面的塑性變形程度下降，抑制積屑瘤和鱗刺的產(chǎn)生，在生產(chǎn)中對于不同材料合理選用切削液可大大減小工件表面粗糙度。</p><p>　　工件材料對表面質(zhì)量的影響</p><p>　　工件材料的性質(zhì)；加工塑性材料時，由刀具對金屬的擠壓產(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。工件材料韌性越好，金屬的

58、塑性變形越大，加工表面就愈越粗糙。加工脆性材料時其切屑呈碎粒狀，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>　　一般韌性較大的塑性材料，加工后表面粗糙度較大，而韌性較小的塑性材料，加工后易得到較小的表面粗糙度。對于同種材料，其晶粒組織越大，加工表面粗糙度越大。因此，為了減小加工表面粗糙度，常在切削加工前對材料進(jìn)行調(diào)質(zhì)或正火處理，以獲得均勻細(xì)密的晶粒組織和較高的硬度。 </p

59、><p>　　切削條件對工件表面質(zhì)量的影響</p><p>　　與切削條件有關(guān)的工藝因素，包括切削用量、冷卻潤滑情況。中、低速加工塑性材料時，容易產(chǎn)生積屑瘤和鱗刺，所以，提高切削速度，可以減少積屑瘤和鱗刺，減小零件已加工表面粗糙度值；對于脆性材料，一般不會形成積屑瘤和鱗刺，所以，切削速度對表面粗糙度基本上無影響。進(jìn)給速度增大，塑性變形也增大，表面粗糙度值增大，所以，減小進(jìn)給速度可以減小表面粗糙

60、度值，但是，進(jìn)給量減小到一定值時，粗糙度值不會明顯下降。正常切削條件下，切削深度對表面粗糙度影響不大，因此，機(jī)械加工時不能選用過小的切削深度。</p><p>　　切削速度對表面粗糙度的影響</p><p>　　一般在粗加工選用低速車削，精加工選用高速車削可以減小表面粗糙度。在中速切削塑性材料時，由于容易產(chǎn)生積屑瘤，且塑性變形較大，因此加工后零件表面粗糙度較大。通常采用低速或高速切削塑性材

61、料，可有效地避免積屑瘤的產(chǎn)生，這對減小表而粗糙度有積極作用。 </p><p>　　磨削加工對表面質(zhì)量的影響</p><p>　　砂輪的影響 砂輪的粒度越細(xì)，單位面積上的磨粒數(shù)越多，在磨削表面的刻痕越細(xì)，表面粗糙度越??；但若粒度太細(xì)，加工時砂輪易被堵塞反而會使表面粗糙度增大，還容易產(chǎn)生波紋和引起燒傷。砂輪的硬度應(yīng)大小合適，其半鈍化期愈長愈好；砂輪的硬度太高，磨削時磨粒不易脫落，

62、使加工表面受到的摩擦、擠壓作用加劇，從而增加了塑性變形，使得表面粗糙度增大，還易引起燒傷；但砂輪太軟，磨粒太易脫落，會使磨削作用減弱，導(dǎo)致表面粗糙度增加，所以要選擇合適的砂輪硬度。砂輪的修整質(zhì)量越高，砂輪表面的切削微刃數(shù)越多、各切削微刃的等高性越好，磨削表面的粗糙度越小。</p><p>　　磨削用量的影響 增大砂輪速度，單位時間內(nèi)通過加工表面的磨粒數(shù)增多，每顆磨粒磨去的金屬厚度減少，工件表面的殘留面積減少；同

63、時提高砂輪速度還能減少工件材料的塑性變形，這些都可使加工表面的表面粗糙度值降低。降低工件速度，單位時間內(nèi)通過加工表面的磨粒數(shù)增多，表面粗糙度值減??；但工件速度太低，工件與砂輪的接觸時間長，傳到工件上的熱量增多，反面會增大粗糙度，還可能增加表面燒傷。增大磨削深度和縱向進(jìn)給量，工件的塑性變形增大，會導(dǎo)致表面粗糙度值增大。徑向進(jìn)給量增加，磨削過程中磨削力和磨削溫度都會增加，磨削表面塑性變形程度增大，從而會增大表面粗糙度值。為在保證加工質(zhì)量的前

64、提下提高磨削效率，可將要求較高的表面的粗磨和精磨分開進(jìn)行，粗磨時采用較大的徑向進(jìn)給量，精磨時采用較小的徑向進(jìn)給量，最后進(jìn)行無進(jìn)給磨削，以獲得表面粗糙度值很小的表面。</p><p>　　工件材料 工件材料的硬度、塑性、導(dǎo)熱性等對表面粗糙度的影響較大。塑性大的軟材料容易堵塞砂輪，導(dǎo)熱性差的耐熱合金容易使磨料早期崩落，都會導(dǎo)致磨削表面粗糙度增大。</p><p>　　另外，由于磨削溫度高，合

65、理使用切削液既可以降低磨削區(qū)的溫度，減少燒傷，還可以沖去脫落的磨粒和切屑，避免劃傷工件，從而降低表面粗糙度值。</p><p>　　影響工件表面物理機(jī)械性能的因素</p><p>　　表面層冷作硬化。切削刃鈍圓半徑增大,對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)。切削速度增大,刀具與工件的作用時間縮短,

66、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,切削熱在工件表面層上的作用時間也縮短了,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)。工件材料的塑性愈大,冷硬現(xiàn)象就愈嚴(yán)重。 　　表面層材料金相組織變化。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發(fā)生變化。磨削燒傷當(dāng)被磨工件表面層溫度達(dá)到相變溫度以上時,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)

67、生甚至出現(xiàn)微觀裂紋,這種現(xiàn)象稱為磨削燒傷。改善磨削燒傷的途徑磨削熱是造成磨削燒傷的根源,故改善磨削燒傷由兩個途徑:一是盡可能地減少磨削熱的產(chǎn)生;二是改善冷卻條件,盡量使產(chǎn)生的熱量少傳入工件。正確選擇砂輪合理選擇切削用量改善冷卻條件。 　　表面層殘余應(yīng)力。產(chǎn)生殘余應(yīng)力的原因:切削時在加工表面金屬層內(nèi)有塑性變形發(fā)生,使表面金屬的比容加大;切削加工中,切</p><p>　　磨削表面層金相組織變化與磨削燒傷</

68、p><p>　　機(jī)械加工過程中產(chǎn)生的切削熱會使得工件的加工表面產(chǎn)生劇烈的溫升，當(dāng)溫度超過工件材料金相組織變化的臨界溫度時，將發(fā)生金相組織轉(zhuǎn)變。在磨削加工中，由于多數(shù)磨粒為負(fù)前角切削，磨削溫度很高，產(chǎn)生的熱量遠(yuǎn)遠(yuǎn)高于切削時的熱量，而且磨削熱有60~80%傳給工件，所以極容易出現(xiàn)金相組織的轉(zhuǎn)變，使得表面層金屬的硬度和強(qiáng)度下降，產(chǎn)生殘余應(yīng)力甚至引起顯微裂紋，這種現(xiàn)象稱為磨削燒傷。產(chǎn)生磨削燒傷時，加工表面常會出現(xiàn)黃、褐、紫、

69、青等燒傷色，這是磨削表面在瞬時高溫下的氧化下膜顏色。不同的燒傷色，表明工件表面受到的燒傷程度不同。</p><p>　　磨削淬火鋼時，工件表面層由于受到瞬時高溫的作用，將可能產(chǎn)生以下三種金相組織變化：</p><p>　　如果磨削表面層溫度未超過相變溫度，但超過了馬氏體的轉(zhuǎn)變溫度，這時馬氏體將轉(zhuǎn)變成為硬度較低的回火索氏體或索氏體，這叫回火燒傷。</p><p>　　

70、如果磨削表面層溫度超過相變溫度，則馬氏體轉(zhuǎn)變?yōu)閵W氏體，這時若無切削液，則磨削表面硬度急劇下降，表層被退火，這種現(xiàn)象稱為退火燒傷。干磨時很容易產(chǎn)生這種現(xiàn)象。</p><p>　　如果磨削表面層溫度超過相變溫度，但有充分的切削液對其進(jìn)行冷卻，則磨削表面層將急冷形成二次淬火馬氏體，硬度比回火馬氏體高，不過該表面層很薄，只有幾微米厚，其下為硬度較低的回火索氏體和索氏體，使表面層總的硬度仍然降低，稱為淬火燒傷。</p

71、><p><b>　　磨削燒傷的改善措施</b></p><p>　　影響磨削燒傷的因素主要是磨削用量、砂輪、工件材料和冷卻條件。由于磨削熱是造成磨削燒傷的根本原因，因此要避免磨削燒傷，就應(yīng)盡可能減少磨削時產(chǎn)生的熱量及盡量減少傳入工件的熱量。具體可采用下列措施：</p><p>　　合理選擇磨削用量 不能采用太大的磨削深度，因為當(dāng)磨削深度增加時，

72、工件的塑性變形會隨之增加，工件表面及里層的溫度都將升高，燒傷亦會增加；工件速度增加，磨削區(qū)表面溫度會增高，但由于熱作用時間減少，因而可減輕燒傷。</p><p>　　工件材料 工件材料對磨削區(qū)溫度的影響主要取決于它的硬度、強(qiáng)度、韌性和熱導(dǎo)率。工件材料硬度、強(qiáng)度越高，韌性越大，磨削時耗功越多，產(chǎn)生的熱量越多，越易產(chǎn)生燒傷；導(dǎo)熱性較差的材料，在磨削時也容易出現(xiàn)燒傷。</p><p>　　砂輪

73、的選擇 硬度太高的砂輪，鈍化后的磨粒不易脫落，容易產(chǎn)生燒傷，因此用軟砂輪較好；選用粗粒度砂輪磨削，砂輪不易被磨削堵塞，可減少燒傷；結(jié)合劑對磨削燒傷也有很大影響，樹脂結(jié)合劑比陶瓷結(jié)合劑容易產(chǎn)生燒傷，橡膠結(jié)合劑比樹脂結(jié)合劑更易產(chǎn)生燒傷。</p><p>　　冷卻條件為降低磨削區(qū)的溫度，在磨削時廣泛采用切削液冷卻。為了使切削液能噴注到工件表面上，通常增加切削液的流量和壓力并采用特殊噴嘴，并在砂輪上安裝帶有空氣擋板的切

74、削液噴嘴，這樣既可加強(qiáng)冷卻作用，又能減輕高速旋轉(zhuǎn)砂輪表面的高壓附著作用，使切削液順利地噴注到磨削區(qū)。此外，還可采用多孔砂輪、內(nèi)冷卻砂輪和浸油砂輪，切削液被引入砂輪的中心腔內(nèi)，由于離心力的作用，切削液再經(jīng)過砂輪內(nèi)部的孔隙從砂輪四周的邊緣甩出，這樣切削液即可直接進(jìn)入磨削區(qū)，發(fā)揮有效的冷卻作用。</p><p>　　使用過程中影響表面質(zhì)量的因素</p><p>　　耐磨性對表面質(zhì)量的影響<

75、/p><p>　　每個剛加工好的摩檫副的兩個接觸表面之間,最初階段在表面粗糙的峰部觸,實(shí)際接觸面積遠(yuǎn)小于理論接觸面積,在相互接觸的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><p>　　疲勞強(qiáng)度對表面質(zhì)量的影響</p><p>　　在交變載荷作用,表面粗糙度的凹谷部位容易引起應(yīng)力集中產(chǎn)生疲勞紋。表面粗糙度值

76、愈大,表面的紋痕愈深,紋底半徑愈小,抗疲勞破壞的能力就愈差。 </p><p>　　耐蝕性對表面質(zhì)量的影響</p><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?？刮g性就愈差。表面層的殘余拉應(yīng)力會產(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>　　機(jī)械加工表面質(zhì)量對零件使

77、用性能的影響</p><p>　　在機(jī)械加工中，零件的加工表面產(chǎn)生微觀不平、殘余應(yīng)力等各種缺陷，雖然僅存于零件極薄的表面層中，卻嚴(yán)重影響著機(jī)械零件的精度、耐磨性、配合性、抗腐蝕性和疲勞強(qiáng)度等，從而進(jìn)一步影響機(jī)械的使用性能和使用壽命。</p><p>　　表面質(zhì)量對零件耐磨性的影響</p><p>　　零件的耐磨性是零件的一項重要性能指標(biāo)，當(dāng)摩擦副的材料、潤滑條件和加

78、工精度確定之后，零件的表面質(zhì)量對耐磨性將起著關(guān)鍵性的作用。由于零件表面存在著表面粗糙度，當(dāng)兩個零件的表面開始接觸時，接觸部分集中在其波峰的頂部，因此實(shí)際接觸面積遠(yuǎn)遠(yuǎn)小于名義接觸面積，并且表面粗糙度越大，實(shí)際接觸面積越小。在外力作用下，波峰接觸部分將產(chǎn)生很大的壓應(yīng)力。當(dāng)兩個零件作相對運(yùn)動時，開始階段由于接觸面積小、壓應(yīng)力大，在接觸處的波峰會產(chǎn)生較大的彈性變形、塑性變形及剪切變形，波峰很快被磨平，即使有潤滑油存在，也會因為接觸點(diǎn)處壓應(yīng)力過大

79、，油膜被破壞而形成干摩擦，導(dǎo)致零件接觸表面的磨損加劇。當(dāng)然，并非表面粗糙度越小越好，如果表面粗糙度過小，接觸表面間儲存潤滑油的能力變差，接觸表面容易發(fā)生分子膠合、咬焊，同樣也會造成磨損加劇。</p><p>　　表面層的冷作硬化可使表面層的硬度提高，增強(qiáng)表面層的接觸剛度，從而降低接觸處的彈性、塑性變形，使耐磨性有所提高。但如果硬化程度過大，表面層金屬組織會變脆，出現(xiàn)微觀裂紋，甚至?xí)菇饘俦砻娼M織剝落而加劇零件的磨

80、損。</p><p>　　表面質(zhì)量對零件疲勞強(qiáng)度的影響</p><p>　　表面粗糙度對承受交變載荷的零件的疲勞強(qiáng)度影響很大。在交變載荷作用下，表面粗糙度波谷處容易引起應(yīng)力集中，產(chǎn)生疲勞裂紋。并且表面粗糙度越大，表面劃痕越深，其抗疲勞破壞能力越差。</p><p>　　表面層殘余壓應(yīng)力對零件的疲勞強(qiáng)度影響也很大。當(dāng)表面層存在殘余壓應(yīng)力時，能延緩疲勞裂紋的產(chǎn)生、擴(kuò)展，

81、提高零件的疲勞強(qiáng)度；當(dāng)表面層存在殘余拉應(yīng)力時，零件則容易引起晶間破壞，產(chǎn)生表面裂紋而降低其疲勞強(qiáng)度。</p><p>　　表面層的加工硬化對零件的疲勞強(qiáng)度也有影響。適度的加工硬化能阻止已有裂紋的擴(kuò)展和新裂紋的產(chǎn)生，提高零件的疲勞強(qiáng)度；但加工硬化過于嚴(yán)重會使零件表面組織變脆，容易出現(xiàn)裂紋，從而使疲勞強(qiáng)度降低。</p><p>　　表面質(zhì)量對零件耐腐蝕性能的影響</p><

82、p>　　表面粗糙度對零件耐腐蝕性能的影響很大。零件表面粗糙度越大，在波谷處越容易積聚腐蝕性介質(zhì)而使零件發(fā)生化學(xué)腐蝕和電化學(xué)腐蝕。</p><p>　　表面層殘余壓應(yīng)力對零件的耐腐蝕性能也有影響。殘余壓應(yīng)力使表面組織致密，腐蝕性介質(zhì)不易侵入，有助于提高表面的耐腐蝕能力；殘余拉應(yīng)力的對零件耐腐蝕性能的影響則相反。</p><p>　　表面質(zhì)量對零件間配合性質(zhì)的影響</p>

83、<p>　　相配零件間的配合性質(zhì)是由過盈量或間隙量來決定的。在間隙配合中，如果零件配合表面的粗糙度大，則由于磨損迅速使得配合間隙增大，從而降低了配合質(zhì)量，影響了配合的穩(wěn)定性；在過盈配合中，如果表面粗糙度大，則裝配時表面波峰被擠平，使得實(shí)際有效過盈量減少，降低了配合件的聯(lián)接強(qiáng)度，影響了配合的可靠性。因此，對有配合要求的表面應(yīng)規(guī)定較小的表面粗糙度值。</p><p>　　在過盈配合中，如果表面硬化嚴(yán)重，將可

84、能造成表面層金屬與內(nèi)部金屬脫落的現(xiàn)象，從而破壞配合性質(zhì)和配合精度。表面層殘余應(yīng)力會引起零件變形，使零件的形狀、尺寸發(fā)生改變，因此它也將影響配合性質(zhì)和配合精度。</p><p>　　表面質(zhì)量對零件其他性能的影響</p><p>　　如對間隙密封的液壓缸、滑閥來說，減小表面粗糙度Ra可以減少泄漏、提高密封性能；較小的表面粗糙度可使零件具有較高的接觸剛度；對于滑動零件，減小表面粗糙度Ra能使摩擦