把手连接件级进模设计—外文翻译(适用于毕业论文外文翻译+中英文

w 毕业设计 外文文献翻译题 目（中文） 冲压成型 （英文） Stamping becomes typ学生姓名 完成日期： 2011 年 03 月 12 日 w 目录1.冲压成型 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 parts topography increases. The goal of forming with 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 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 stretch 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 solid die steel on the pressdownstroke. The result is a stamping with uncontrolled material flow in terms of straindistribution. Since “loose metal” is present on the stamping caused by uncontrolled materialflow the part tends to be dimensionally and structurally unstable.Stretch Form Forming operations 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 surface 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 whereas 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 contacts 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 punch. 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 deformation 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 areas 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 blankholder. 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 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 thickness 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 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 force 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 drawn 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. Consequently 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 radius. 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 upward 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. 冲压成型译文： 板料冲压成形成功机率着冲压件形状的复杂程度减少而增加冲压成形的目的是生产具有一定尺寸形状并有稳定一致应力状态甚至无起皱无裂纹的冲压件.冲压有一种至多种成形方式用来成型所需形状它们是弯曲局部成形拉深局部成形用来成形凹陷形状或凸包拉深用来成形啤酒罐之类的冲压件随着冲压件的形状越来越复杂多种成形方法将会被用到同一零件的成型中事实上有很多冲压件上同时有弯曲局部成型拉深模具成型的特征通常有三种形式的模具它们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种成形材料的成形模具这类模具只是简单地通过一个冲头在压力机下行过程中把材料“撞击”进入凹模中成形材料。得到的是由无控制材料 w流动导致的应罚状态的冲压件，由无约束材料流动产生的“松弛金属区”的出现，?逖辜叽绾托巫瓷锨饔诓晃榷?局部成形 成形工序中用一压边圈来控制材料流动压边圈是置于模具上的一个多压装置，由带压边圈模具成形的冲压件可分为三部分，如图一，它们分别是产品表面（图中红色表示部分），压边圈（图中蓝色表示部分）以及连接这两部分的壁，在凸模一端壁与壁之间的角称作凸模过渡区。 凸模模穴理论上是在壁与压边圈面的交叉处，凸模被置于凸模穴之中，而压边圈被放在凸模穴外凸模的周围，这种模具还有上面的装置将压边圈与凸模联接起来，片料或工序件放到指定位置后压力机下行，上模开始接触片料，压边圈在凸模周围的材料上压出一些锁紧台阶或筋，从防止成形过程中材料从压边圈流向凸模部分随压边圈不再发生作用，材料不断地变形直到成形为凸模下部成形部分形状，在压力机回程时，模具做与下行时相反的动作，最后已经成形的冲压件被从模具上移走，就完成了一冲局部成形。三 拉深 拉深的得名并不是因为材料在成形中变形情况得来，而是因为在拉深过程中材料进入拉离压边圈表面，直入凸模下面尽管拉深变形产生在拉深模中，但很多局部成形，弯曲模在工作过程中也对板料进行不同程度的拉深变形。 拉深模的工作机制，与局部成形模具非常类似，不同的是，在拉深模中，压边圈部分有特定的地方必须更加严格地控制材料流入凹模量，以防止起皱，拉深模中，控制材料流入是通过成形半月型的拉深筋来代替局部成形中的锁紧台阶，一般在直边部分设一至三条，以控制这部分的材料流入而在复杂边部分少设或不设拉深筋，当板料工序件放到模具相应位置后，拉深的第一个阶段是模具是板料以及压边圈的接触. 毛坯上为考虑到拉深过程中毛坯圆周沿走私方向减少留有的法兰边是所有材料中流动最俦的地方随着压力机滑块继续下行材料变形流过凹模圆角半径.板料开始形成与凸模一致的形状，在拉深的工序中，这部分很少发生变形。被除数压在凹模腔中的空气由于凸模以及制件的下降而从气孔中排出。四 凸模、凹模的圆角半径应为 4-6 倍料厚以防止裂纹及起皱。 随着模具继续闭合，校形开始发生，弯过凹模圆角材料，变形成钣金件的直壁部分，压边圈下边 的材料被拉入凹模并弯过凹模圆部分，考虑到防止材料被拉裂，凹模圆角半径应为 4-10 个料厚。毛坯变形情况为周向压缩么向拉伸，这样被拉入凹模圆腔中的 w工序称为拉深，拉深过程有：摩擦压缩、拉伸。因此，拉深过程中，压力机必须提供足够大的压力，以克服拉深过程中的各种抗变形力，如：压边圈与毛坯间的静摩擦力，额外的力也是必须的，用来克服拉深过程中滑支摩擦力。克服由压边圈弯过凹模圆角在后面行程中校直成直壁材料的变形力。在毛坯被拉入凹模沉着凹模半径变弯，在接下来变形中校直的同时，压边圈部分毛坯被沿周向压缩。而且沿着圆周半径方向上压缩量随着半径增大而增大半径越大的地方，需压缩的面积也大，这样的结果是压边圈部分的材料变厚，而凸模部分的材料因为被拉深变薄。在有些拉深中，拉深变形使拉深壁变形成卷曲形或弓形。最薄的区域是冲压件直壁与圆角过渡部分，因为这部分在拉深过程中拉伸变形最久，受力最大，这里往往也是最容易拉裂的地方，因为这部分的加工硬化少于其它地方。 拉深工序到压力机行程下死点结束，拉深工序结束后，压力机滑块上行，模具打开，奢力圈在弹性元件作用下，从凸模上卸下包附在凸模上的冲压件，冲头下面没有通气孔，当冲压件被压边圈推起时，空气可进入。冲压件离开凸模产生的真空部分如果不设通气孔，冲压件将很难脱出。Material Behavior AutoForge allows the material to be represented as 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 Youngs modulus E thePoissons ratio S and the initial yield stress y. For a rigid-plastic material only 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 workhardening 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 Hookes 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 Youngs modulus of the material. E modulus of elasticity axial stress/axial strain （D.1） Experiments show that axial elongation 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 Poissons ratio. Similarly the shear modulus modulus of rigidity isdefined as: G shear modulus shear stress/shear strain D.3 It can 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 . Time-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 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 Within 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 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 total 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 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 starts 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 stress 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 simplifications 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 workhardening slopes 5. Strain-softening material negative workhardening slope In addition to elastic material constants Youngs modulus and Poissons ratio it isessential to be concerned with yield stress and workhardening slopes in dealing with inelastic wplastic material behavior. These quantities 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 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 .