機(jī)械專業(yè)畢業(yè)設(shè)計外文翻譯--極限與誤差

1、<p><b>　　英文資料</b></p><p>　　Limits and Tolerances</p><p>　　The breakage of the machine spare parts ,generally always from the surface layer beginning of .The function of the prod

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

3、s medium various craft factor to process the surface quantity influence of regulation, in order to make use of these regulations to control to process the proces</p><p>　　The machine processes the surface qu

4、antity to use the influence of the function to the machine</p><p>　　(A) The surface quantity to bear to whet the sexual influence </p><p>　　1.Rough degree of surface to bea

5、r to whet the sexual influence</p><p>　　A just process vice-of two contact surfaces of good friction, the first stage is rough only in the surface of the peak department contact ,the actual contact area is m

6、uch smaller than theoretical contact area, in contact with each other the peak of the units have very great stress, to produce actual contact with the surface area of plastic deformation, deformation and peak between the

7、 Department of shear failure, causing serious wear.</p><p>　　Parts wear may generally be divided into three stages, the initial stage of wear and tear, normal wear and tear all of a sudden intense phase of s

8、tage wear.</p><p>　　Parts of the surface roughness of the surface wear big impact. In general the smaller the value of surface roughness, wear better. However, surface roughness value is too small, lubricant

9、s difficult to store, contact between the adhesive-prone elements, wear it to increase. Therefore, the surface roughness of a best value, the value and parts of the work related to increased work load, the initial wear i

10、ncreased, the best rough surface is also increased.</p><p>　　2.Cold Working hardening the surface of the wear resistance </p><p>　　Processing the Cold Work hardening the surface of the friction

11、surface layer of metal microhardness increase, it will generally improve the wear resistance. Cold Working but not a higher degree of hardening, wear resistance for the better, because too much will lead to hardening of

12、the Cold Working excessive loose organization of metal, even a crack and peeling off the surface of the metal, declined to wear resistance.</p><p>　　(B)The surface quality of the impact of fatigue strength&l

13、t;/p><p>　　Metal hand alternating loads of fatigue after the damage occurred in parts often Chilled layer below the surface and, therefore parts of the surface quality of fatigue very influential.</p>&l

14、t;p>　　Surface roughness on the impact of fatigue strength</p><p>　　In alternating load, the surface roughness of the Au-site easily lead to stress concentration, a fatigue crack, the higher the value of s

15、urface roughness, surface traces of Yu Shen Wen, Wen at the end of the radius smaller, anti-fatigue damage at the end of the more capacity Worse.</p><p>　　Residual stress, fatigue Cold Work hardening of the

16、impact </p><p>　　Residual stress on the impact of large parts fatigue. Surface layer of residual stress fatigue crack will expand and accelerate the fatigue damage the surface layer and the residual stress c

17、an prevent fatigue crack growth, delaying the formation of fatigue damage.</p><p>　　(C)The surface quality of the corrosion resistance of the impact</p><p>　　Parts of the corrosion resistance to

18、 a large extent depends on the surface roughness. The higher the value of surface roughness, Au Valley accumulate on the more corrosive substances. Corrosion resistance of the more worse.</p><p>　　Surface la

19、yer of residual stress will produce stress corrosion cracking, lower parts of the wear-resistance, and the residual stress is to prevent stress corrosion cracking.</p><p>　　(D) The surface quality with quali

20、ty</p><p>　　Rough surface will affect the value of the size of the co-ordination with the surface quality. The gap with rough value will increase wear and tear, increased space, with the requirements of the

21、destruction of nature. For Fit, the assembly part of the process of convex surface-crowded peak times, the actual reduction of the surplus and reduce the support of the connection between the strength.</p><p&g

22、t;　　Dimensioning</p><p>　　The design of a machine includes many factors other than those of determining the loads and stresses and selecting the proper materials. Before construction or manufacture can begin

23、, it is necessary to have complete assembly and detail drawings to convey all necessary information to the shop men. The designer frequently is called upon to check the drawings before they are sent to the shop. Much exp

24、erience and familiarity with manufacturing processes are needed before one can become conversant wi</p><p>　　Drawings should be carefully checked to see that the dimensioning is done in a manner that will be

25、 most convenient and understandable to the production departments. It is obvious that a drawing should be made in such a way that it has one and only one interpretation. In particular, shop personnel should not be requir

26、ed to make trigonometric or other involved calculations before the production machines can be set up.</p><p>　　Dimensioning is an involved subject and long experience is required for its mastery.</p>

27、<p>　　Tolerances must be placed on the dimensions of a drawing to limit the permissible variations in size because it is impossible to manufacture a part exactly to a given dimension. Although small tolerances give

28、higher quality work and a better operating mechanism, the cost of manufacture increases rapidly as the tolerances are reduced, as indicated by the typical curve of Fig 14.1. It is therefore important that the tolerances

29、be specified at the largest values that the operating or functional con</p><p>　　Tolerances may be either unilateral or bilateral. In unilateral dimensioning, one tolerance is zero, and all the variations ar

30、e given by the other tolerance. In bilateral dimensioning, a mean dimension is used which extends to the midpoint of the tolerance zone with equal plus and minus variations extending each way from this dimension.</p&g

31、t;<p>　　The development of production processes for large-volume manufacture at low cost has been largely dependent upon interchangeability of component parts. Thus the designer must determine both the proper tole

32、rances for the individual parts, The manner of placing tolerances on drawings depends somewhat on the kind of product or type of manufacturing process. If the tolerance on a dimension is not specifically stated, the draw

33、ing should contain a blanket note which gives the value of the tolerance fo</p><p>　　Dimension and Tolerance</p><p>　　In dimensioning a drawing, the numbers placed in the dimension lines represe

34、nt dimension that are only approximate and do not represent any degree of accuracy unless so stated by the designer. </p><p>　　To specify a degree of accuracy, it is necessary to add tolerance figures to the

35、 dimension. Tolerance is the amount of variation permitted in the part or the total variation allowed in a given dimension. A shaft might have a nominal size of 2.5 in. (63.5mm), but for practical reasons this figure cou

36、ld not be maintained in manufacturing without great cost. Hence, a certain tolerance would be added and , if a variation of ±0.003 in.(±0.08mm) could be permitted, the dimension would be stated 2.500±</

37、p><p>　　Dimensions given close tolerances mean that the part must fit properly with some other part. Both must be given tolerances in keeping with the allowance desired, the manufacturing processes available, a

38、nd the minimum cost of production and assembly that will maximize profit. Generally speaking, the cost of a part goes up as the tolerance is decreased. If a part has several or more surfaces to be machined, the cost can

39、be excessive when little deviation is allowed from the nominal size.</p><p>　　Allowance, which is sometimes confused with tolerance, has an altogether different meaning.</p><p>　　It is the minim

40、um clearance space intended between mating parts and represents the condition of tightest permissible fit. If a shaft, size 1.498, is to fit a hole of size 1.500, the minimum size hole is 1.500 and the maximum size shaft

41、 is 1.498. Thus the allowance is 0.002 and the maximum clearance is 0.008 as based on the minimum shaft size and maximum hole dimension.</p><p>　　Tolerances may be either unilateral or bilateral. Unilateral

42、tolerance means that any variation is made in only one direction from the nominal or basic dimension. Referring to the previous example, the hole is dimensioned 1.500, which represents a unilateral tolerance. If the dime

43、nsions were given as 1.500±0.003, the tolerance would be bilateral; that is , it would vary both over and under the nominal dimension. The unilateral system permits changing the tolerance while still retaining the s

44、ame </p><p>　　Tolerances Limits and Fits</p><p>　　The drawing must be a true and complete statement of the designer’s expressed in such a way that the part is convenient to manufacture. Every di

45、mension necessary to define the product must be stated once and repeated in different views. Dimensions relating to one particular feature, such as the position and size of hole, where possible, appear on the same view.&

46、lt;/p><p>　　There should be no more dimensions than are absolutely necessary, and no feature should be located by more than one dimension in any direction. It may be necessary occasionally to give an auxiliary

47、dimension for reference, possibly for inspection. When this is so, the dimension should be enclosed in a bracket and marked for reference. Such dimensions are not governed by general tolerances.</p><p>　　Dim

48、ensions that affect the function of the part should always be specified and not left as the sum or other dimensions. If this is not done, the total permissible variation on that dimension will form the sum or difference

49、of the other dimensions and their tolerance, and this with result in these tolerances having to be made unnecessarily tight. The overall dimension should always appear.</p><p>　　All dimensions must be govern

50、ed by the general tolerance on the drawing unless otherwise stated. Usually, such a tolerance will be governed by the magnitude of the dimension. Specific tolerances must always be stated on dimensions affecting or inter

51、changeability. </p><p>　　A system of tolerances is necessary to allow for the variations in accuracy that are bound to occur during manufacture, and still provide for interchangeability and correct function

52、of the part.</p><p>　　A tolerance is the difference in a dimension in order to allow for unavoidable imperfections in workmanship. The tolerance range will depend on the accuracy of the manufacturing organiz

53、ation, the machining process and the magnitude of the dimension. The greater the tolerance range is disposed on both sides of the nominal dimension. A unilateral tolerance is one where the tolerance zone is on one side o

54、nly of the nominal dimension, in which case the nominal dimension may from one of the limits.</p><p>　　Limits are the extreme dimensions of the tolerance zone. For example, nominal dimension</p><p

55、>　　30mm tolerance limits </p><p>　　Fits depend on the relationship between the tolerance zones of two mating parts, and may be broadly classified into a clearance fit with positive allowance, a transiti

56、on fit where the allowance may be either positive or negative (clearance or interference) , an interference fit where the allowance is always negative.</p><p>　　Type of Limits and Fits</p><p>　　

57、The ISO system of Limits and Fits, widely used in a number of leading metric countries, is considerably more complex than the ANSI system.</p><p>　　In this system, each part has a basic size. Each limit of p

58、art, high and sign being obtained by subtracting the basic size form the limit in question. The difference between the two limits of size of a part is called the tolerance, an absolute without sign.</p><p>　

59、　There are three classes of fits: 1) clearance fits, 2) transition fits ( the assembly may have either clearance or interference ), and 3) interference fits .</p><p>　　Either a shaft-basis system or a hole-b

60、asis system may be used. For any given basic size, a range of tolerance and deviations may be specified with respect to be line of zero deviation, called the zero line. The tolerance is a function of the basic size and i

61、s designated by a number symbol, called the grade-thus the tolerance grade. The position of the tolerance with respect to the zero line also a function of the basic size-is indicated by a letter symbol(or two letter), a

62、capital letter for ho</p><p>　　Twenty standard grades of tolerance are provided, called IT 01,IT 0 ,IT 1-18, providing numerical values for each nominal diameter, in arbitrary steps up to 500mm (for example

63、0-3,3-6,6-10…, 400-500mm). The value of the tolerance unit, I, for grades 5-16 is</p><p>　　Where i is in microns and D in millimeters.</p><p>　　Standard shaft and hole deviations similarly are p

64、rovided by sets of formulas, However, for practical, both tolerances and deviations are provided in three sets of rather complex tables. Additional tables gives the values for basic sizes above 500mm and for “Commonly Us

65、ed Shafts and Holes” in two categories ---“General Purpose” and “Fine Mecbanisms and Horology”.</p><p><b>　　中文翻譯</b></p><p><b>　　極限與誤差</b></p><p>　　機(jī)械零件的破壞，一

66、般總是從表層開始的。產(chǎn)品的性能，尤其式它的可靠性和耐久性，在很在程度上取決于零件表層的質(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加工表面質(zhì)量影響的規(guī)律，以便運用這些規(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>　　機(jī)械加工表面質(zhì)量對機(jī)器使用性能的影響</p><p>　?。ㄒ唬┍砻尜|(zhì)量對耐磨性的影響 </p>&

67、lt;p>　　1.表面粗糙度對耐磨性的影響</p><p>　　一個剛加工好的摩擦副的兩個接觸表面之間，最初階段只在表面粗糙度的峰部接觸，實際接觸面積遠(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，使實際接觸表面積處產(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>　　零件磨損一般可分為三個階段，初期磨損階段、正常磨損階段忽然劇烈磨損階段。</

68、p><p>　　表面粗糙度對零件表面磨損的影響很大。一般說表面粗糙度值越小，其磨損性越好。但表面粗糙度值太小，潤滑油不易儲存，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最佳值，其值與零件的工作情況有關(guān)，工作載荷加大時，初期磨損量增大，表面粗糙最佳也加大。</p><p>　　2.表面冷作硬化對耐磨性的影響</p><p>　　加工表面的冷作硬化

69、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，耐磨性久愈好，這是因為過分的冷作硬化將引起金屬組織過度疏松，甚至出現(xiàn)裂紋和表面金屬的剝落，使耐磨性下降。</p><p>　?。ǘ┍砻尜|(zhì)量對疲勞強(qiáng)度的影響</p><p>　　金屬手交變載荷作用后產(chǎn)生的疲勞破壞往往發(fā)生在零件表面和冷硬層下面，因此零件表面質(zhì)量對疲勞強(qiáng)度影響很大。</p><

70、;p>　　1.表面粗糙度對疲勞強(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、冷作硬化對疲勞強(qiáng)度的影響</p><p>　　殘余應(yīng)力對零件疲勞強(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

71、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>　?。ㄈ┍砻尜|(zhì)量對耐蝕性的影響</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。</p><p>　　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，而殘余應(yīng)力則能防止應(yīng)力腐蝕開裂。</p&g

72、t;<p><b>　　尺寸標(biāo)注</b></p><p>　　一個機(jī)構(gòu)的設(shè)計除了要考慮載荷硬力和選擇合適的條件外還包括許多因素。裝配或制造之前必須完成裝配圖和零件圖的繪制以便傳遞所有必要的信息給車間的工人。設(shè)計人員非常頻繁的被叫檢查圖紙在這些圖紙送到車間之前。要熟悉生產(chǎn)圖樣的所有情況，需要對制造過程非常熟悉并具有很多經(jīng)驗。</p><p>　　圖紙應(yīng)仔細(xì)

73、被檢查以便使尺寸標(biāo)注在生產(chǎn)車間最方便和理解的方式下標(biāo)注。非常明顯圖紙應(yīng)在有一種且只有一種解釋的方式下標(biāo)注。特別是，在生產(chǎn)用機(jī)械能被調(diào)整好之前，車間工作人員不需要進(jìn)行 三角學(xué)或其他復(fù)雜的計算。</p><p>　　尺寸標(biāo)注是一項復(fù)雜的工作，要熟悉它需要長期的實踐經(jīng)驗。</p><p>　　公差必須標(biāo)注在圖紙尺寸的后面以便限制在尺寸方面的變動偏差，因為不可能知道一個在尺寸方面非常精確的零件。雖

74、然小的公差產(chǎn)生高質(zhì)量的產(chǎn)品和機(jī)器，但是隨公差的減小制造成本快速增加，正如圖典型曲線所示，因此公差的確定在能保證產(chǎn)品質(zhì)量或功能下取最大值。</p><p>　　公差可能是單向的或雙向的。在單向尺寸標(biāo)注中一個公差是零，所有的偏差由另一個公差給出。在雙向尺寸標(biāo)注中，使用平均公差即上下偏差絕對值相等的公差帶。</p><p>　　工藝制造流程發(fā)展大批量制造低成本依靠零部件的互換性。因此設(shè)計者必須確

75、定包括單個零件的合適公差和確定裝配零件公差是間隙或過盈。生產(chǎn)者把公差標(biāo)注在圖紙上依靠產(chǎn)品類型和制造工藝類型給出注釋。如果尺寸公差沒有特別注明，圖樣必須要一個給出這些尺寸的公差值的綜合注釋。然而一些生產(chǎn)者并不用綜合注釋假定每個尺寸是單獨的被考慮的可能會規(guī)定出注釋中要求的更寬的公差。在任何情況下非常重要的是圖紙不能模棱兩可和只能有一種解釋。</p><p><b>　　尺寸和公差</b><

76、/p><p>　　在圖樣標(biāo)注時，除非設(shè)計者有意標(biāo)明，注在尺寸線上的數(shù)字表明的尺寸僅是近似的，并不代表任何精確的等級。為了明確尺寸等級，在尺寸后面加上公差等級是必須的。公差是在某一零件上被允許的變化量或在尺寸上總的變化量。一個軸可能有一個名義尺寸2.5英尺，但由于實際操作原因它不能實現(xiàn)在花費大量制造成本。因此一個確定的公差將被加上，如果±0.003英尺的變化被允許，尺寸將標(biāo)注為2.500±0.003

77、。</p><p>　　尺寸標(biāo)準(zhǔn)給定小的公差意味著相應(yīng)零件比其他零件更合適。配合的零件都必須保持渴望的允差值，制造過程有效，生產(chǎn)裝配中實現(xiàn)最小成本和最大利率。一般的說，如果公差減小生產(chǎn)成本上升。如果一個零件有幾個或多個面要生產(chǎn)，當(dāng)要求小的偏差生產(chǎn)成本將急劇上升。</p><p>　　允差有時會和公差混淆，它具有完全不同的意義。允差是設(shè)計最小的公差空間在配合零件和代表最緊的配合條件下。如果一

78、個軸尺寸為1.498,與它配合的孔的尺寸1.500,最小孔為1.500和最大軸的尺寸為1.498。因此最大允差為0.002和最大間隙為0.008，在最小軸和最大孔尺寸的基礎(chǔ)上。</p><p>　　公差可能是單邊的或雙邊的。單邊公差意味以前任何偏差只在名義尺寸的一個方向。如上面的例子，孔的尺寸標(biāo)注為1.500,表示單邊公差。如果尺寸標(biāo)注為1.500±0.003,公差表示為雙邊的。單邊系統(tǒng)允許公差值發(fā)生變

79、化但依然能保持相同的允差或配合類型，對雙邊的公差系統(tǒng)，它是不可以的，如果配合零件中一個或兩個名義標(biāo)注尺寸發(fā)生變化。在大批量生產(chǎn)中配合必須滿足互換性，單邊公差是常用的。為了在配合零件有過盈或受力配合，公差必須產(chǎn)生一個零或負(fù)的允差。</p><p><b>　　公差極限和配合</b></p><p>　　圖紙必須真實和完整反映設(shè)計者的意圖在這樣方法下零件方便于制造。每一個

80、尺寸必須表達(dá)不同視圖里尺寸至少且只能為一次。對于有特殊要求的尺寸，如既有尺寸大小位置和要求，把尺寸和位置最好標(biāo)在同一視圖里。</p><p>　　除絕對需要的尺寸之外，不應(yīng)該再有更多的尺寸，而在任一方向上，只能在一個尺寸上注上特殊要求。在偶爾情況下給出一個輔助的尺寸作為參考，可能為檢驗時用。在這種情況下，尺寸應(yīng)該用括號括起來，以便參考。這樣的尺寸不標(biāo)公差。</p><p>　　影響零件功能

81、的尺寸必須總是明確的給出不能留下另外的尺寸。如果不直接標(biāo)注，在這種尺寸可能產(chǎn)生總的變化將要有以下構(gòu)成的，有其他尺寸和他們公差的和或差，而且這會導(dǎo)致這些不能不定得過緊。整體尺寸應(yīng)該能表現(xiàn)出現(xiàn)。</p><p>　　在圖紙上所有尺寸都有由一般公差來制定除非特別標(biāo)明。一般，如一個公差被標(biāo)注的尺寸數(shù)字的旁邊。專門公差標(biāo)注在影響尺寸功能或互換性必須專門標(biāo)注公差。</p><p>　　公差系統(tǒng)是必須允

82、許這樣一種變化在制造過程中必須出現(xiàn)的精度變化，仍然提供互換性和功能真確的零件。</p><p>　　公差在不同尺寸上不同的是為了允許在制造上不可避免的缺陷。公差變化依賴制造機(jī)器的精度，加工過程和尺寸大小。公差范圍越大，制造過程中成本越低。雙邊公差的公差帶會以名義尺寸上下移動，單邊公差的公差帶只能在名義尺寸的一邊變動，在這種情況下名義尺寸可能是一個極限尺寸。</p><p>　　極限是公差帶

83、最外邊尺寸。如名義尺寸30mm公差帶極限尺寸。</p><p>　　配合依賴于兩個配合零件公差帶關(guān)系，可以分成公差為正的間隙配合，過渡配合它的允差可能是正值或負(fù)值，過盈配合它的允差總是負(fù)值。</p><p><b>　　極限和配合的種類</b></p><p>　　世界標(biāo)準(zhǔn)組織的極限和配合，廣泛用在許多先進(jìn)米制國家，它比英制標(biāo)準(zhǔn)體系更相當(dāng)復(fù)雜。

84、</p><p>　　在世界標(biāo)準(zhǔn)公差系統(tǒng)，每個零件有一個基本尺寸。每個零件有一個極限尺寸，上下偏差從基本尺寸分開，大小和符號是極限尺寸減去基本獲得的。差值為零件的兩個極限尺寸之差稱為公差，它是沒有符號的絕對值。</p><p>　　這里有三種配合：1）間隙配合2）過渡配合（此配合可組成過渡或過盈）和3）過盈配合。</p><p>　　任何一個基軸制或基孔制都有使用。

85、任一給定基本尺寸，公差范圍和偏差被標(biāo)準(zhǔn)化根據(jù)零偏差，這個零偏差稱為零線。公差是體現(xiàn)基本尺寸的一個功能被一些數(shù)字符號設(shè)計，這些數(shù)字符號叫等級即公差等級。公差帶位置相對零線的位置也是基本尺寸一個功能—用字母符號來表示，用大寫字母表示孔和用小寫字母表示軸。對有基本尺寸為45mm孔和軸的配合就可以寫成45H8/g7。</p><p>　　規(guī)定了20種標(biāo)準(zhǔn)公差等級，即IT01，IT0，IT1-118，它們是在500mm 以

86、內(nèi)硬性劃分的每一段（例如0-3，3-6，6-10，… …,400-500mm）的基本尺寸都對應(yīng)有不同的標(biāo)準(zhǔn)公差數(shù)值。基本公差單元值為i，公差等級為5-16是i單位為nm和D單位為mm.</p><p>　　通過一系列公式軸和孔基本偏差標(biāo)準(zhǔn)化，但是在實際應(yīng)用下，公差和偏差被提供在三套復(fù)雜表格里。軸表給出基本尺寸在500mm以上和“通用的軸和孔”分成兩個表---“一般用途”和“精密機(jī)械和鐘表”。</p>