文献翻译-弯曲模设计

Bending Dies DesignBending is the uniform straining of material, usually flat sheet or strip metal, around a straight axis which lies in the neutral plane and normal to the lengthwise direction of the sheet or strip set after removal of the applied stress. The inner surface of a bend is in compression; the outer surface is in tension. A pure bending action doe not reproduce the exact shape of the punch and die in the metal ;such a reproduction is one of forming .The neutral axis is the plane area in bent metal where all strains are zero .Bend Radii. Minimum bendradii vary for different metals; generally, different annealed metals can be bent to a radius equal to the thickness of the metal without cracking or weakening.Bend Allowances. Since bent metal is longer after bending , its increased length , generally of concern to the product designer , may also have to be considered by the die designer if the length tolerance of the bent part is critical .The length of bent metal may be calculated from the equation:B=A 2 (Ri+Kt)/360Where Bbend allowance, in (mm) (along neutral axis);Abend angle, deg;R i inside radius of bend, in (mm);t metal thickness ,in (mm);K0.33 when Ri is less than 2t and is 0.5 when Ri is more than 2t.Bending Methods . Two bending methods are commonly made use of in press tools. Metal sheet or strip by a V block is forced by a wedge-shaped punch into the block .This method, termed V bending, produces a bend having an included angle which may beacute, obtuse, or90. Friction between a spring-loaded knurled pin in the vee of a die and the part will prevent or reduce side creep of the part during its bending.Edge bending is cantilever loading of a beam .The bending punch forces the metal against the supporting die .The bend axis is parallel to the edge of the die .The workpiece is clamped to the die block by a spring-loaded pad before the punch contacts the workpiece to prevent its movenment during downward travel of the punch .Bending Force. The force required for V bending is as follows:P=KLSt/WForce U bending (channel bending) pressures will be approximately twice those required for V bending; edge bending requires about one-half those needed for V bending .Springback . After bending pressure on metal is released , the elastic stress also are released , which causes metal movement resulting in a decrease in the bend angle ( as well as an increase in the included angle between the bent portions ) . Such a metal movement , termed springback , varies in steel from 0.5 to 5 ,depending upon its hardness ,phosphor bronze may springback , varies in steel from 10 to 15.V-bending dies customarily compensate for springback with V blocks and wedge-shaped punches having included angles somewhat less than that required in the part. The part is bent through a greater angle than that required but it springs back to the desired angle.Parts produced in other types of bending dies are also overbent though an angle equal to the springback angle with an undercut or relieved punch.Piercing Die DesignA complete press tool for cutting two holes in work material at one stroke of the press, classified and standardized by a large manufacturer as a single-station piercing die.Any complete press tool ,consisting of a pair( or a combination of pairs ) of mating members for producing pressworked ( stamped ) parts, including all supporting and actuating elements of the tool, is a die .Pressworking terminology commonly defines the female part of any complete press tool as a die.The guide pins, or posts,are mounted in the lower shoe .The upper shoe contains bushings which slide on the guide pins .The assembly of the lower and upper shoes with guide pins and bushings is a die set .Die sets in many sizes and designs are commercially.A punnch holder mounted to the upper shoe holds two round punches (male members of the die) which are guided by bushings inserted in the stripper.A sleeve, or quill, encloses one punch to prevent its buckling under pressure from the ram of the press .Afer penetration of the work material,the two punches enter the die bushing for a slight distance.The female member, or die, consists of two die bushings inswetwd in die block. Since this press tool punches holes to the diameters required, the diameters of the die bushings are larger than those of the punches by the amount of clearance.Since the work material stock or workpiece can cling to a punch on the upstroke, it may be necessary to strip the material from the punch .Spring-loaded strippers hold the work material against the die block until the punches are withdrawn from the punched holes .A workpiece to be pierced is commonly held and located in a nest composed of flat plates shaped to encircle the outside part contours. Stock is positioned in dies by pins, blocks, or other types of stops for locating before the downstroke of the ram. 中文翻译弯曲模设计弯曲是沿平板料或条料位于中性面内的中心线（通常为沿长度方向）发生的均匀变形。由于金属流动发生在金属的塑性变形范围内，因此当加载荷去除后将会保留一个永久性的弯曲变形，弯曲件内表面呈现压缩变形。普通弯曲变形不可能在被弯曲的金属材料上准确地再现凸、凹模形状再现是成性工序中的一种。中性层是在弯曲材料上变形为零的平面。弯曲半径。最小弯曲半径因材料而异，通常情况下，退火状态的金属材料能被弯曲与材料厚度相等的半径而不会发生弯裂现象。弯曲件的展开长度。由于弯曲后被弯金属会变长，一般产品设计者应考虑其增加的长度，如果弯曲件的长度公差非常关键，那么对于模具设计者也必须考虑其长度的变化。弯曲金属的长度可用如下公式计算：B=A2(R+Kt)/360式中 B弯曲沿中性轴展开长度 （mm） ；A-弯曲中心角 （） ；Ri弯曲件内表面半径 （mm） ；t材料厚度 （mm） ；K0.33 （R2t） 。弯曲方法。在弯曲模中通常采用两种弯曲方法。由 V 形块支承的金属条料或板料，在楔形凸模的作用下进入 V 形块内。这种弯曲方法称为 V 形弯曲，使弯曲件成形为锐角、钝角或直角。在 V 形模具内，弹性定料销和零件之间的摩擦将会阻碍或减少零件在弯曲过程中的边缘偏移。打弯是对横梁的悬臂部分的加载，弯曲凸模施加于金属，使之背靠凹模块。弯曲件的中心线平行与凹模边缘。在凸模接触坯料之前，坯料被弹性压料板压紧在凹模块上，以防止在凸模下行时金属的窜动。弯曲力。V 形弯曲力计算公式如下：P=KLSt/WU 形弯曲力大致是 V 形弯曲力的两倍；打弯力为 V 形弯曲的 1/2.回弹。当作用在金属材料上的弯曲力去除后，弹性应力也随即释放，这就引起金属的移动，从而导致弯曲中心角的减小（即弯曲部件间的包角增大） 。这种金属材料的移动称为回弹。钢材的回弹角在 0.55范围内变化，这主要取决于金属材料的硬度。磷青铜的回弹角可达到 1015。V 形弯曲模具