An anisotropic plane stress yield function that is described by 3 rd -degree spline curves has been proposed. To fix the parameters for the model, three types of mechanical tests are needed. In this study, only uniaxial tensile tests at several angles from the rolling direction have been carried out, because stress states of the target for comparison are uniaxial stress in this case. The characteristic of this model is that the calculated flow stresses and r values fit the experimental values

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... all directions. Also it has been expanded to represent the differential work hardening model and the thickness measured experimentally is compared with the thickness simulated by the hole expanding test. The results of the experiment are almost in accord with the result of the simulation by the proposed method. There is little difference between the results of the differential hardening model and conventional hardening model in this case. Key words: sheet metal forming, yield function, anisotropic material, differential work hardening, hole expanding test. JFE スチール(株) スチール研究所 〒260-0835 福山市鋼管町 1 番地