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1、w 畢業(yè)設(shè)計 外文文獻翻譯題 目（中文） 沖壓成型 （英文） Stamping becomes typ學(xué)生姓名 完成日期： 2011 年 03 月 12 日 w 目錄1.沖壓成型 作者: STEPHENS2.材料特性 作者：MARK JAFE w Stamping becomes typ The confidence level in successfully forming a sheetmetal stamping increases as thesimplicity of the part’s topography increases. The goal of forming with

2、stamping technologiesis to produce stampings with complex geometric surfaces that are dimensionally accurate andrepeatable with a certain strain distribution yet free from wrinkles and splits. Stampings haveone or more forming modes that create the desired geometries. These modes are bendingstretch

3、forming and drawing. Stretching the sheetmetal forms depressions or embossments.Drawing compresses material circumferentially to create stampings such as beer cans.As thesurfaces of the stamping become more complex more than one mode of forming will berequired. In fact many stampings have bend stret

4、ch and draw features produced in the formdie. The common types of dies that shape material are solid form stretch form and draw.Solid Form The most basic type of die used to shape material is the solid form die. This tool simplydisplaces material via a solid punch “crashing” the material into a soli

5、d die steel on the pressdownstroke. The result is a stamping with uncontrolled material flow in terms of straindistribution. Since “l(fā)oose metal” is present on the stamping caused by uncontrolled materialflow the part tends to be dimensionally and structurally unstable.Stretch Form Forming operations

6、 that provide for material flow control do so with a blankholder. Theblankholder is a pressurized device that is guided and retained within the die set. Stampingsformed with a blankholder may be described as having three parts shown in Fig. 1. They arethe product surfaceshown in red blankholder surf

7、ace flat area shown in blue and a wallthat bridges the two together. The theoretical corner on the wall at the punch is called thepunch break. The punch opening is the theoretical intersection at the bottom of the draw wallwith the blankholder. The male punch is housed inside the punch opening where

8、as theblankholder is located around the punch outside the punch opening. These tools have aone-piece upper member that contacts both the blankholder and punch surfaces. A blank orstrip of material is fed onto the blankholder and into location gauges. On the press downstrokethe upper die member conta

9、cts the sheet and forms a lock step or bead around the outside wperimeter of the punch opening on the blankholder surface to prevent material flow off theblankholder into the punch. The blankholder then begins to collapse and material stretchesand compresses until it takes the shape of the lower pun

10、ch. The die actions reverse on thepress upstroke and the formed stamping is removed from the die.Draw The draw die has earned its name not from the mode of deformation but from the factthat the material runs in or draws off the blankholder surface and into the punch. Although thedraw mode of deforma

11、tion is present in draw dies some degree of the stretch forming andbending modes generally also are present. The architecture and operational sequence for drawdies is the same as stretch-form dies with one exception. Material flow off the blankholder indraw dies needs to be restrained more in some a

12、reas than others to prevent wrinkling. This isachieved by forming halfmoon-shaped beads instead of lock steps or beads found instretch-form dies. The first stage of drawing sheetmetal after the blank or strip stock has beenloaded into the die is initial contact of the die steel with the blank and bl

13、ankholder. The blankround for cylindrical shells to allow for a circumferential reduction in diameter is firmlygripped all around its perimeter prior to any material flow. As the press ram continuesdownward the sheetmetal bends over the die radius and around the punch radius. Thesheetmetal begins to

14、 conform to the geometry of the punch.Very little movement orcompression at the blank edge has occurred to this point in the drawing operation. Air trappedin the pockets on the die steel is released on the press downstroke through air vents.The die radius should be between four and 10 times sheet th

15、ickness to prevent wrinkles andsplits. Straightening of sheetmetal occurs next as the die continues to close. Material that wasbent over the die radius is straightened to form the draw wall. Material on the blankholdernow is fed into the cavity and bent over the die radius to allow for straightening

16、 withoutfracture. The die radius should be between four and 10 times sheet thickness to preventwrinkles and splits. The compressive feeding or pulling of the blank circumferentially towardthe punch and die cavity is called drawing. The draw action involves friction compressionand tension. Enough for

17、ce must be present in drawing to overcome the static friction betweenthe blank and blankholder surfaces. Additional force is necessary during the drawing stage to wovercome sliding or dynamic friction and to bend and unbend the sheet from the blankholdersurface to the draw wall. As the blank is draw

18、n into the punch the sheetmetal bends aroundthe die radius and straightens at the draw wall. To allow for the flow of material the blank is compressed. Compressionincreases away from the die radius in the direction of material flow because there is moresurface area of sheetmetal to be squeezed. Cons

19、equently the material on the blankholdersurface becomes thicker.The tension causes the draw wall to become thinner. In some casesthe tension causes the draw wall to curl or bow outward. The thinnest area of the sheet is atthe punch radius and gradually tapers thicker from the shock line to the die r

20、adius. This is aprobable failure site because the material on the punch has been work-hardened the leastmaking it weaker than the strain hardened material. The drawing stage continues until thepress is at bottom dead center. With the operation now complete the die opens and theblankholder travels up

21、ward to strip the drawn stamping off of the punch. Air vents providedin flat or female cavities of the punch allow air to travel under the material as it is lifted by theblankholder. The stamping will have a tendency to turn inside out due to vacuum in theabsenceof air vents. 沖壓成型譯文： 板料沖壓成形成功機率著沖壓件形

22、狀的復(fù)雜程度減少而增加沖壓成形的目的是生產(chǎn)具有一定尺寸形狀并有穩(wěn)定一致應(yīng)力狀態(tài)甚至無起皺無裂紋的沖壓件.沖壓有一種至多種成形方式用來成型所需形狀它們是彎曲局部成形拉深局部成形用來成形凹陷形狀或凸包拉深用來成形啤酒罐之類的沖壓件隨著沖壓件的形狀越來越復(fù)雜多種成形方法將會被用到同一零件的成型中事實上有很多沖壓件上同時有彎曲局部成型拉深模具成型的特征通常有三種形式的模具它們是自由成型局部成形以及拉深形式.一 自由成形 自由成形是用的最基本的一種成形材料的成形模具這類模具只是簡單地通過一個沖頭在壓力機下行過程中把材料“撞擊”進入凹模中成形材料。得到的是由無控制材料 w流動導(dǎo)致的應(yīng)罰狀態(tài)的沖壓件，由無約

23、束材料流動產(chǎn)生的“松弛金屬區(qū)”的出現(xiàn)，?逖辜嘰綰托巫瓷锨饔誆晃榷?。?局部成形 成形工序中用一壓邊圈來控制材料流動壓邊圈是置于模具上的一個多壓裝置，由帶壓邊圈模具成形的沖壓件可分為三部分，如圖一，它們分別是產(chǎn)品表面（圖中紅色表示部分），壓邊圈（圖中藍色表示部分）以及連接這兩部分的壁，在凸模一端壁與壁之間的角稱作凸模過渡區(qū)。 凸模模穴理論上是在壁與壓邊圈面的交叉處，凸模被置于凸模穴之中，而壓邊圈被放在凸模穴外凸模的周圍，這種模具還有上面的裝置將壓邊圈與凸模聯(lián)接起來，片料或工序件放到指定位置后壓力機下行，上模開始接觸片料，壓邊圈在凸模周圍的材料上壓出一些鎖緊臺階或筋，從防止成形過程中材料從壓邊圈

24、流向凸模部分隨壓邊圈不再發(fā)生作用，材料不斷地變形直到成形為凸模下部成形部分形狀，在壓力機回程時，模具做與下行時相反的動作，最后已經(jīng)成形的沖壓件被從模具上移走，就完成了一沖局部成形。三 拉深 拉深的得名并不是因為材料在成形中變形情況得來，而是因為在拉深過程中材料進入拉離壓邊圈表面，直入凸模下面盡管拉深變形產(chǎn)生在拉深模中，但很多局部成形，彎曲模在工作過程中也對板料進行不同程度的拉深變形。 拉深模的工作機制，與局部成形模具非常類似，不同的是，在拉深模中，壓邊圈部分有特定的地方必須更加嚴(yán)格地控制材料流入凹模量，以防止起皺，拉深模中，控制材料流入是通過成形半月型的拉深筋來代替局部成形中的鎖緊臺階，一般在

25、直邊部分設(shè)一至三條，以控制這部分的材料流入而在復(fù)雜邊部分少設(shè)或不設(shè)拉深筋，當(dāng)板料工序件放到模具相應(yīng)位置后，拉深的第一個階段是模具是板料以及壓邊圈的接觸. 毛坯上為考慮到拉深過程中毛坯圓周沿走私方向減少留有的法蘭邊是所有材料中流動最儔的地方隨著壓力機滑塊繼續(xù)下行材料變形流過凹模圓角半徑.板料開始形成與凸模一致的形狀，在拉深的工序中，這部分很少發(fā)生變形。被除數(shù)壓在凹模腔中的空氣由于凸模以及制件的下降而從氣孔中排出。四 凸模、凹模的圓角半徑應(yīng)為 4-6 倍料厚以防止裂紋及起皺。 隨著模具繼續(xù)閉合，校形開始發(fā)生，彎過凹模圓角材料，變形成鈑金件的直壁部分，壓邊圈下邊 的材料被拉入凹模并彎過凹模圓部分，考

26、慮到防止材料被拉裂，凹模圓角半徑應(yīng)為 4-10 個料厚。毛坯變形情況為周向壓縮么向拉伸，這樣被拉入凹模圓腔中的 w工序稱為拉深，拉深過程有：摩擦壓縮、拉伸。因此，拉深過程中，壓力機必須提供足夠大的壓力，以克服拉深過程中的各種抗變形力，如：壓邊圈與毛坯間的靜摩擦力，額外的力也是必須的，用來克服拉深過程中滑支摩擦力?？朔蓧哼吶澾^凹模圓角在后面行程中校直成直壁材料的變形力。在毛坯被拉入凹模沉著凹模半徑變彎，在接下來變形中校直的同時，壓邊圈部分毛坯被沿周向壓縮。而且沿著圓周半徑方向上壓縮量隨著半徑增大而增大——半徑越大的地方，需壓縮的面積也大，這樣的結(jié)果是壓邊圈部分的材料變厚，而凸模部分的材料因為

27、被拉深變薄。在有些拉深中，拉深變形使拉深壁變形成卷曲形或弓形。最薄的區(qū)域是沖壓件直壁與圓角過渡部分，因為這部分在拉深過程中拉伸變形最久，受力最大，這里往往也是最容易拉裂的地方，因為這部分的加工硬化少于其它地方。 拉深工序到壓力機行程下死點結(jié)束，拉深工序結(jié)束后，壓力機滑塊上行，模具打開，奢力圈在彈性元件作用下，從凸模上卸下包附在凸模上的沖壓件，沖頭下面沒有通氣孔，當(dāng)沖壓件被壓邊圈推起時，空氣可進入。沖壓件離開凸模產(chǎn)生的真空部分如果不設(shè)通氣孔，沖壓件將很難脫出。Material Behavior AutoForge allows the material to be represented as

28、either an elastic-plastic material or asa rigid-plastic material. The material is assumed to be isotropic hence for the elastic-plasticmodel a minimum of three material data points are required the Young’s modulus E thePoisson’s ratio S and the initial yield stress y. For a rigid-plastic material on

29、ly the yieldstress is required. These data must be obtained from experiments or a material handbook.These values may vary with temperature in a coupled analysis. This is prescribed using theTABLES option. The flow stress of the material changes with deformation so called strainhardening or workharde

30、ning behavior and may be influenced by the rate of deformation.These behavior are also entered via the TABLES option. The linear elastic model is the model most commonly used to represent engineering wmaterials. This model which has a linear relationship between stresses and strains isrepresented by

31、 Hooke’s Law. Figure D-1 shows that stress is proportional to strain in auniaxial tension test. The ratio of stress to strain is the familiar definition of modulus ofelasticity Young’s modulus of the material. E modulus of elasticity axial stress/axial strain （D.1） Experiments show that axial elong

32、ation is always accompanied by lateral contraction ofthe bar. The ratio for a linear elastic material is: v lateral contraction/axial elongation D.2 This is known as Poisson’s ratio. Similarly the shear modulus modulus of rigidity isdefined as: G shear modulus shear stress/shear strain D.3 It can

33、be shown that for an isotropic material G E / 2 1n D.4 The stress-strain relationship for an isotropic linear elastic method is expressed as： Where is the Lame constant and G the shear modulus is expressed as： The material behavior can be completely defined by the two material constants E and . Tim

34、e-Independent Inelastic Behavior In uniaxial tension tests of most metals and many other materials the followingphenomena can be observed. If the stress in the specimen is below the yield stress of thematerial the material will behave elastically and the stress in the specimen will beproportional to

35、 the strain. If the stress in the specimen is greater than the yield stress thematerial will no longer exhibit elastic behavior and the stress-strain relationship will becomenonlinear. Figure D-2 shows a typical uniaxial stress-strain curve. Both the elastic andinelastic regions are indicated. w Wit

36、hin the elastic region the stress-strain relationship is unique. Therefore if the stressin the specimen is increased loading from zero point 0 to 1 point 1 and then decreasedunloading to zero the strain in the specimen is also increased from zero to 1 and thenreturned to zero. The elastic strain is

37、completely recovered upon the release of stress in thespecimen. Figure D-3 illustrates this relationship. The loading-unloading situation in the inelastic region is different from the elasticbehavior. If the specimen is loaded beyond yield to point 2 where the stress in the specimenis 2 and the tota

38、l strain is 2 upon release of the stress in the specimen the elastic strain iscompletely recovered. However the inelastic plastic strain remains in the specimen. FigureD-3 illustrates this relationship. Similarly if the specimen is loaded to point 3 and thenunloaded to zero stress state the plastic

39、strain remains in the specimen. It is obvious that isnot equal to. We can conclude that in the inelastic region Plastic strain permanently remains in the specimen upon removal of stress. The amount of plastic strain remaining in the specimen is dependent upon the stresslevel at which the unloading s

40、tarts path-dependent behavior. The uniaxial stress-strain curve is usually plotted for total quantities total stress versustotal strain. The total stress-strain curve shown in Figure D-2 can be replotted as a total stressversus plastic strain curve as shown in Figure D-4. The slope of the total stre

41、ss versus plasticstrain curve is defined as the workhardening slope H of the material. The workhardeningslope is a function of plastic strain. The stress-strain curve shown in Figure D-2 is directly plotted from experimental data. Itcan be simplified for the purpose of numerical modeling. A few simp

42、lifications are shown inFigure D-5 and are listed below: 1. Bilinear representation – constant workhardening slope 2. Elastic perfectly-plastic material – no workhardening 3. Perfectly-plastic material – no workhardening and no elastic response 4. Piecewise linear representation – multiple constant

43、workhardening slopes 5. Strain-softening material – negative workhardening slope In addition to elastic material constants Young’s modulus and Poisson’s ratio it isessential to be concerned with yield stress and workhardening slopes in dealing with inelastic wplastic material behavior. These quantit

44、ies vary with parameters such as temperature andstrain rate further complicating the analysis. Since the yield stress is generally measured fromuniaxial tests and the stresses in real structures are usually multiaxial the yield condition of amultiaxial stress state must be considered. The conditions

45、 of subsequent yield workhardeningrules must also be studied. Yield Conditions The yield stress of a material is a measured stress level that separates the elastic andinelastic behavior of the material. The magnitude of the yield stress is generally obtained froma uniaxial test. However the stresses in a structure are usually multiaxial. A measurement ofyielding for the multiaxial state of stress is called .