Research On The Forming Limit Of Conditions For One-step Stamping For Conical Parts

Conical part is one of the typical parts of axisymmetric curved parts. The conical wall forming combines by deep drawing and bulging. The study of the forming limit of one-step stamping for conical parts is the foundation of the axisymmetric curved parts. The two major problems of one-step stamping for conical parts are wall wrinkling and the fracture at the bottom of punch. Researches on the judge standards of one-step stamping for conical parts with no wall wrinkling and fracture, and the analyses of the influence factors of forming limit are of great important. They enrich stamping basic theory and guide the engineering practice productions.According to the material properties and geometric relations of conical parts, the two displacement conditions of one-step stamping for conical parts without wall wrinkling are established. According to the mechanics relationship of conical wall, two conditions of one-step stamping for conical parts without fracture are established. The applicability of the displacement conditions are discussed through finite element simulations(FEM) and the conditions are amended by experiments to obtain more accurate judgment conditions.Researches on the change law of the displacement in longitude direction and the average extensional strain in longitude direction of the key point K in conical forming with the relative diameter of top are conducted. It is shown from the experimental and simulation results that the maximum value of the average extensional strain in longitude direction at the K point is less than 12%.The forming regions in the two-dimensional coordinate system under d1/d2-h/d2 were given and the forming conditions that may occur in different areas were discussed. It is shown that the simulation result and the experimental results were consistent. According the die parameter d1/d2 and forming height we can determine whether conical parts can form in one-step and estimation defect mode of conical parts.The effects of hardening exponent n on one-step stamping for conical parts are discussed. The drawing parts with larger limiting forming heights and displacements in longitude direction can be obtained by using materials with larger values of n. Meanwhile, the homogeneity of bulging and the forming limit can be improved.