2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
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1、<p><b>  英文資料</b></p><p>  Methods to study stamping forming</p><p>  The objective of the stamping forming research is to realize and apply the principles to solve various engi

2、neering problems through study on the stamping forming procedure. Recently, the research on stamping has been carried out in wide range with various methods. The research can be summed up substantially into following typ

3、es.</p><p>  The double line arrows in the picture denote the procedure of formal theoretical research. In such research, the actions of the equipment and die are decomposed into micro-ingredients of the for

4、ce and applied on the microstructure of the metal according to the multi-crystal microstructure of the deformation metal, the deformation of the metal microstructure is then investigated and the deformation of the micros

5、tructure to macro-deformation of the sheet metal is summed up. This scientific method </p><p>  Since the formal theoretical research method encounters formidable difficulty, a kind of simplified theoretical

6、 method appears in the research field of the stamping forming. The characteristic of this kind of research method is denoted by continuous line in the picture, which is the main trend of the recent research. This researc

7、h assumes metal as the ideal homogeneous solid and simplifies the property parameters, the boundary conditions and the blank geometrical parameters of the metal, the sta</p><p>  The third method to study st

8、amping forming is shown by dashed dotted line in the picture. The characteristic of this method is that ignoring the deformation process of the blank under the action of the load during stamping forming conditions (inclu

9、ding the structure of the die, the geometrical parameters of the die working portion and the properties of the stamping equipment) with the final results of the stamping forming. It is a rational empirical method, and wi

10、dely used in stamping technology</p><p>  The fourth method to study stamping forming is denoted by dashed line in the picture. Based on the fundamental knowledge of the mechanics and metallurgy, the essenti

11、al characteristics and principle of the stamping forming are investigated to solve the practical problems in stamping process. In comparison with other plastic processes, the characteristics of the stamping forming, the

12、principles of the sheet metal deformation are unique. So this method has definitely aim and the analysis results ca</p><p>  (1)The sequence of the stamping process can be decided by the trend rule of the st

13、amping deformation.</p><p>  (2)According to the rule of uniform velocity distribution in the outer flange of the deformation zone during multi-pass deep drawing for the box parts, the shape and dimension of

14、 the blank during process sequence can be calculated. Therefore the calculation the for deep box parts of the multi-pass deep drawing technology is based on scientific foundation to improve the technique level of stampin

15、g forming.</p><p>  (3)According to the research on the wrinkle during the sheet metal forming caused by non-uniform tensile and shearing force, a new research field is developed beyond the traditional compr

16、essive instability theory. The results obtained offer an effective measure to cope directly with wrinkle during stamping forming.</p><p>  (4)The theory of sorting stamping forming based on the characteristi

17、cs of the stamping deformation and mechanics and mechanics is an easy approach to systematize of the stamping forming, and can be used to deepen the investigation on stamping forming limit, to point out a clear and defin

18、ite direction for improve the stamping forming limit.</p><p>  Above examples indicate that this method is closely relevant to the real stamping forming process. It can be used to analyze and solve the stamp

19、ing forming problems effectively. Although this method is in the junior stage, mainly focusing on the qualitative analysis for stamping forming now . With the constant progress of this method and combined with modern me

20、chanics, the breakthrough of this method is expected to further enhance stamping forming technology. </p><p>  Structural design of blanking die</p><p>  l. Principle and general procedure of

21、die designing</p><p>  The steps of die designing include collecting necessary data, determining the structure scheme based on sufficient analysis and investigation, drawing the working principle diagram, t

22、he final assembly diagram, and then drawing the part diagram of the die according to the final assembly diagram.</p><p>  The necessary data to be collected include: the parts drawing of the product, the pro

23、ductive batch of the product, the process chart, the process specification and the die design program. The manufacture datum of each operation, the types of the die structural (simple die, progressive die or compound

24、die) , the capacity of the press, the quality of the blanking work piece and other necessary items should be record in the process chart and the process specification.</p><p>  The detailed structure and dim

25、ension of the die are determined according to the production batch and work piece demand, etc. For the small batch production, the structure of die should be simple, the manufacture period should be short, and the cost s

26、hould be as low as possible. For the large batch, the perfect structure, high productivity and long working life should be pursued.</p><p>  Furthermore, the structure measures to adjust, utilize, maintain,

27、transport and deposit the dies should be taken into account.</p><p>  2. Determination of the pressure center of die</p><p>  The acting point of the resultant force in blanking is called the pr

28、essure center of die. In order to guarantee the die to work smoothly, the pressure center of die should align with the axes of shank and the center line of the slide block of press, to prevent the deflection of die durin

29、g working, which would result in non-uniform clearance and wearing. Usually, the pressure center of die is laid on its symmetrical center point. The determination of the pressure center of die is mainly for the </p&g

30、t;<p>  For the work piece with complex shape, it can be divided into straight-line section (the pressure center of die is situated at the middle of the straight) and arc section, and then to calculate its pressur

31、e center.</p><p>  The method to find the resultant force of the parallel force system is usually adopted to obtain the pressure center of die. The procedure to obtain the pressure center of die for multi-pu

32、nch blanking by analytic method is showns chematically in Fig.3.23. </p><p>  (1) Draw the outline of the working portion of punch proportionally.</p><p>  (2) Select the co-ordinate X-Y. The

33、 selection of the co-ordinate should simplify the calculation.</p><p>  (3)calculate the perimeter of each graphic outline (or linear section)L1,L2,L3,L4,..., Ln(representing the blanking force), and the dis

34、tance of gravity center in each graphic outline to the coordinate axes x1, x2, x3, x4, ...,xn and y1,y2,y3,y4,...,yn.</p><p>  (4) According to the mechanic principle that "the moment of the resultant f

35、orce to a certain axis is equal to the sum of the moment of each component to the same axis", the calculation equation of the distance from the die pressure center to the axes of X and Y can be obtained:</p>

36、<p>  x0= (3-20)</p><p>  y0= (3-21)</p><p>  The determination of the pressure center of die can also be obtained graphically by t

37、he linear polygon method.</p><p>  3. Determination of the shut height of die</p><p>  The outline dimension of die should fit with the selected press.For example,the lower die of the blanking s

38、hould be able to install in the working table of the press,the dimension of the shank should be consistent with that of the hole in the slide block,the ejecting pin of the ejecting device in the lower die should be able

39、to penetrate through the bolster hole of press. The shut height of die should be consistent with that of the press.</p><p>  The shut height of die refers to the distance H between the top surface of the upp

40、er bolster and bottom surface of the lower bolster when the die is in the lowest working position. The shut height of press refers to the distance between the lower surface of the slide block and the upper surface of the

41、 bolster installed in the working bable when the slide block is in the lower dead point. The height when the length of the connecting rod is adjusted to the shortest, is called the maximum shut hei</p><p> 

42、 If the shut height of die is larger than the maximum height of press, the die cannot be used in this press; oppositely, if the shut height of die is less than the minimum height, the die can be used by adding a bolster.

43、</p><p><b>  中文翻譯</b></p><p><b>  沖壓成形的研究方法</b></p><p>  沖壓成形的研究工作,就是在正確而深入地了解沖壓成形過程的基礎上,認識沖壓成形過程中的各種規(guī)律性的內(nèi)容,并把它運用于解決沖壓生產(chǎn)中出現(xiàn)的各種實際問題。目前在沖壓成形方面開展的研究工作領域十分廣泛,而采用

44、的研究方法也各有特點,但工作概括成以下幾種類型。</p><p>  圖中中間雙線箭頭表示正規(guī)的規(guī)范化類型的理論研究工作,在這種理論研究工作中,把設備與模具的作用,根據(jù)變形金屬多晶體微觀結構的實際情況,分解成作用力的微觀成分,使其作用在金屬的微觀結構上,研究金屬微觀結構的變形行為,最終將這些微觀的變形結果匯總成為板材毛坯的宏觀變形。當然,這種理論研究方法是十分科學的,無可挑剔的。但是,由于當前的金屬學與力學的發(fā)展

45、還不能滿足這樣的需要,所以這種規(guī)范性很強的理論研究工作還處于理想和期望的狀態(tài),在實踐中是不存在的。</p><p>  由于規(guī)范化的純理論研究方法遇到了不可克服的困難,于是在沖壓成形的研究理論領域里出現(xiàn)了經(jīng)過某種簡化了的理論研究工作。這種理論研究方法的特點在圖中用單實線箭頭表示,它是當前理論研究方法的主流。這種理論研究方法,首先把金屬材料簡化成為理想的均勻固體,再進一步簡化金屬材料性能參數(shù)、邊界條件。毛坯的幾何參

46、數(shù)的條件下,利用數(shù)學分析的方法研究沖壓成形過程,并用數(shù)學的方法描述沖壓成形的各種規(guī)律性的內(nèi)容。由于進行了前述的各種簡化,必然使數(shù)學運算和分析過程與真實的沖壓變形過程有某種程度的偏離,所以這種研究結果也必然是近似的,不能完全真實地反映沖壓變形過程,尤其是在較為復雜的沖壓成形時,這種理論研究方法就顯得不夠有力了。近年來,由于有限元方法與計算機技術的發(fā)展,使這種理論研究工作有了很大的進展,即使在復雜形狀沖壓件成形中也顯示出較好的應用前景,目前

47、這種理論研究方法多用于某些較為具體的沖壓成形的研究,可以期望這種研究方法在沖壓成形基本規(guī)律的研究方面取得更多的成就。另一方面,由于這種理論研究中存在簡化與假設,為了證明這種理論研究結果的可信程度,實驗驗證工作是必需的。</p><p>  第三種沖壓成形研究方法,如圖中點畫線箭頭所示。這種研究方法的特點是:無視沖壓成形時毛坯金屬在受力作用下產(chǎn)生變形的過程,而是僅僅把模具的結構與工作部分的幾何參數(shù)、沖壓設備的作用特

48、點等初始成形條件,與成形結果直接聯(lián)系起來,用以處理沖壓成形中的實際問題??梢哉f,這是一種比較合理的經(jīng)驗方法,也是目前在沖壓成形技術領域中應用較多的方法。雖然這種方法具有直觀、簡單實用、易為生產(chǎn)技術人員接受等優(yōu)點,但是,由于它具有很強的局限性,而且也不能深入揭露真是的沖壓變形過程,從而影響人們對沖壓成形的深入認識,所以它不是沖壓成形研究工作的根本方法,不宜用這種方法深入地探索沖壓成形中規(guī)律性的內(nèi)容。</p><p>

49、;  第四種沖壓成形的研究方法,如圖中虛線箭頭所示。它是利用力學與金屬學的基礎知識,對沖壓成形中的各種問題進行分析、加工與概括,明確沖壓成形的基本特點與規(guī)律,用以處理和解決沖壓生產(chǎn)中的實際問題。與其他的塑性加工方法相比,沖壓成形具有十分明顯的特點,板材的變形行為也具有其獨特的規(guī)律,所以這種研究方法具有十分明確的針對性與目的,而且研究結果可以直接應用于沖壓成形實際問題的分析與處理,也易于為生產(chǎn)技術人員接受和在工作中靈活地運用。這種研究工作

50、的特點與效果,可用以下幾方面的實際應用來說明。</p><p>  (1)利用沖壓變形趨向性規(guī)律可以作為沖壓工作過程設計中決定成形工藝順序的基本原則。</p><p>  (2)根據(jù)盒形件多次拉深過程中變形區(qū)外緣運動速度均勻分布的準則,確定工序間毛坯形狀與尺寸的計算法,使高盒形件多次拉深的工藝計算有了科學的依據(jù),使沖壓生產(chǎn)技術水平有所提高。</p><p>  (3

51、)根據(jù)板材成形特點開展的不均勻拉力作用下的起皺與剪力作用下的起皺方面的研究工作,在傳統(tǒng)的壓縮失穩(wěn)理論范疇之外,又開拓了新的研究領域,而已取得的研究成果又直接為克服沖壓成形中的起皺缺陷提供了針對性很強的所謂“對癥下藥”的對策。</p><p>  (4)根據(jù)沖壓成形與力學的特點進行的沖壓變形分類的理論,可使沖壓成形的研究工作走向體系化研究的捷徑,而且可以深化對沖壓成形極限的認識,為提高沖壓成形極限的技術工作提供清晰

52、而明確的方向。</p><p>  由上述的實際應用可以看出,這種研究工作方法與沖壓成形的實際情況的關系十分密切,所以對于沖壓成形出現(xiàn)的問題分析與處理是十分有效的。雖然由于這種研究工作的深度與廣度還很不夠,目前主要用于對沖壓成形中各種問題的定性分析,不過隨著這種研究方法的不斷發(fā)展,在與現(xiàn)代力學方法相結合的基礎上,可望有突破性的進展,從而促進沖壓成形技術的進步。</p><p><b&

53、gt;  沖裁模結構設計</b></p><p>  1.沖模設計的原則與一般程序</p><p>  進行模具設計時,設計者首先要收集必要的資料,經(jīng)過充分分析和研究確定模具結構方案后,便可著手繪制模具工作原理圖,然后繪制模具總裝圖,根據(jù)模具總裝圖再繪制模具各零件圖。</p><p>  收集的資料有:產(chǎn)品零件圖、產(chǎn)品生產(chǎn)批量、工藝線路單、工藝規(guī)程卡和模

54、具設計任務書。工藝線路單和工藝規(guī)程卡應記有各工序的加工基準、模具結構型式(單工序模、復合或連續(xù)模)、使用壓機的噸位、沖裁件質量及其他應注意的事項等。</p><p>  沖模的具體結構與尺寸由生產(chǎn)批量、工件要求等確定。對于小批量生產(chǎn),模具結構力求簡單,制造周期短,成本低。對于大批量生產(chǎn),模具結構力求完善,生產(chǎn)效率高,壽命長。</p><p>  此外,還要考慮到模具調整、使用、維修以及模具

55、搬運、存放和安全等方面結構措施。</p><p>  2.沖模壓力中心的確定</p><p>  沖裁力合力的作用點成為沖模壓力中心。為保證沖模平衡地工作,沖模的壓力中心必須通過模柄軸線,且和壓機滑塊的中心線相重合,以防模具工作時發(fā)生歪斜、間隙不均勻、導致磨損等。通常,模具布置時將壓力中心安防在凹模的對稱中心點上。確定壓力中心的工作,主要對復雜沖裁模、多凹模沖孔模及連續(xù)模才進行。</

56、p><p>  對于性狀復雜的工件可先將其分成直線段(壓力中心在直線重點)及圓弧段再求其壓力中心。</p><p>  壓力中心的求法,一般采用求平衡力系合力作用的方法。如圖3—23所示多凸模沖裁用解析法求壓力中心的計算程序如下:</p><p>  (1)按比例繪出凸模工作部分的外形;</p><p>  (2)任意選定坐標軸X、Y,坐標軸的選

57、定應使計算簡便。</p><p>  (3)計算個圖形輪廓周長(或線段)L1、L2、L3、L4....,Ln(代替沖裁力),以及各圖形中心到坐標軸的距離x1、x2、x3、x4,…和y1、y2、y3、y4…yn。</p><p>  (4)根據(jù)“合力對某軸之力矩等于各分力對同軸力矩之和”的力學原理,得到?jīng)_模壓力中心到X軸和Y軸距離的公式:</p><p>  (5)

58、x0= (3-20)</p><p>  y0= (3-21)</p><p>  壓力中心也可以用圖解法,采用索線多邊形法求得。</p><p>  3.沖模封閉高度的確定</p><p>  沖模結構的外形尺寸必須與所選的壓

59、機相適應,如:沖模下模外形平面尺寸應能安裝在壓機的工作臺面上,模柄尺寸與滑塊裝??壮叽鐟恢?,下模頂件裝置所用緩沖器的頂桿應能通過壓機墊板孔。模具的封閉高度與壓機的封閉高度相適應。</p><p>  沖模的封閉高度是指模具在最低工作位置時,上模座頂面與夏末做頂面間的距離H。壓機的封閉高度是指壓機的滑塊在下死點時,滑塊下表面至工作臺墊板上表面之間的距離。當連桿調至最短時,為壓機的最大封閉高度Hmax;當連桿調至最

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