Issue 30

C.J.Su et alii, Frattura ed Integrità Strutturale, 30 (2014) 502-514; DOI: 10.3221/IGF-ESIS.30.61 503 Sutasn Thipprakmas [8] carried the simulation on V-ring blank holder with finite element and researched on the influence rule of material flow and stress distribution of the V-ring blank holder. Wen Limin et al. [9] established the model of fine blanking on blank holder with unilateral V-ring via the finite element, simulated the circular parts with the thickness of 2.9 mm under different tooth pitches, observed the stress distribution of material during the fine blanking process, and obtained the best relative clearance of blank. Lin Guozheng et al. [10] analyzed the 7 mm thickness of blank with finite element and found out the best blanking clearance and die entrance. From the above study, it is evident that V-ring can restrain the flow of materials in the shear zone and increases the hydrostatic pressure, and then gets a larger euphotic zone. The blank holder with unilateral V-ring has been widely applied in the plate cutting. However, there may be some problems, such as burr, low shape and dimension precision if the plate is too thick. To solve this problem, this thesis brings forward a new method that is holding the blank with bilateral V-ring. It can not only increase the hydrostatic pressure of shearing deformation zone and allow material give full play to its plasticity, but also enhance the cross section quality of shear plane. T HE MECHANISM AND THEORETICAL BASIS OF METAL PLATE FINE BLANKING The mechanism of metal plate fine blanking ine blanking is a non-chip machining technology. This is a kind of precision stamping method based on common stamping technology. When used in a stamping forming, it can get more precise size precision, more smooth cutting surface, smaller warping and higher quality stampings of interchangeability than ordinary blanking parts and improve the quality of the products under low cost. Fine blanking is a process of plastic shear, in the special three dynamic fine blanking press with special structure, under the action of the plate in the plastic shear. Before blanking punch contact sheet, a certain pressure makes the V – ring material pressing on the concave die, thus producing lateral pressure on the inner surface of V-shaped teeth and preventing the material tear and metal horizontal flow in shear. In the punch into the materials at the same time, the backpressure of ejector presses the material and in the pressed state, punch down for blanking operation. The material of shear zone in the three directions compresses the stress state, and then improves the material plasticity. The material will produce plastic separation along the punch and die cutting edge. The theoretical basis of metal plate fine blanking Before finite elements analysis, the fine blanking deformation zone should go first. The outside force and stress in fine blanking of the deformation areas of the material are shown in Fig. 1. (a) (b) Figure 1 : Force and stress of distribution in fine blanking. In the figure ： y F － stamping force for punch act on material, y 1 2 y y F F F   , where y 1 F 、 y 2 F is stamping force and jacking force, v F － force for the inner edges of V-ring act on the material, N － lateral force, x y , P P － friction force, F