沖壓模具設計外文資料翻譯(編輯修改稿)

　

【文章內容簡介】 n in the direction normal to the direction of elongation but a definite change in thickness, that is, thinning. Bending is the mode of deformation observed when the sheet material is made to go over a die or punch radius, thus suffering a change in orientation. The deformation is an example of plane strain elongation and contraction A plete press tool for cutting a hole or multiholes in sheet material at one stroke of the press as classified and standardized by a large manufacturer as a singlestation piercing die is shown in Figure3. Any plete press tool, consisting of a pair( or a bination of pars ) of mating member for producing pressworked (stmped） parts, including all supporting and actuating elements of the tool, is a die. Pressworking terminology monly defines the female part of any plete 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 mercially available. The guide pins are shown in Figure 3. Figure3 Typical singlestation die for piercing hole 1— Lower shoe 2,5— Guide bushings 3— Cavity plate 4— Guid pin 6— Springloaded stripper 7— Punch 8— Support plate 9— Punch bushing 10— Fanshaped block 11— Fixed plate 12— Punchholder plate 13— Backing plate 14— Spring 15— Stepping bolts 16— Upper shoe 17— Shank A punch 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. After peration of the work material, the two punches enter the die bushings for a slight distance. The female member, or die, consists of two die bushings inserted in the 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. Springloaded strippers hold the work material against the die block until the punches are withdrawn from the punched holes. A workpiece to be pierced is monly held and located in a nest (Figure 23) posed 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. Bending is one of the most mon forming operations. We merely have to look at the ponents in an automobile or an applianceor at a paper clip or a file cabito appreciate how many parts are shaped by bending. Bending is used not only to form flanges, seams, and corrugations but also to impart stiffness to the part ( by increasing its moment of inertia ). The terminology used in bending is shown in Figure 4. Note that, in bending, the outer fibers of the material are in tension, while the inner fibers are in pression. Because of the Poisson39。s ratio, the width of the part (bend length, L) in the outer region is smaller, and in the inner region is larger than the original width. This phenomenon may easily be observed by bending a rectangular rubber eraser. Minimum bend radii 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. As R/T decreases (the ratio of the bend radius to the thickness bees smaller), the tensile strain at the outer fiber in