Investigation into non‐steady‐state three‐dimensional helical extrusion of twisted sections by the rigid‐plastic finite element method

In metal forming, there are problems with recurrent geometric characteristics and without explicitly prescribed boundary conditions. In such problems, so‐called recurrent boundary conditions must be introduced. The present study deals with non‐steady‐state three‐dimensional finite element analysis for helical extrusion of twisted clover and trocoidal gear sections through a curved die. A boundary‐directed remeshing scheme based on the modular remeshing technique has been proposed to reduce the errors arising in mapping of variables between old and new mesh systems. The computed extrusion pressures in reaching the near steady‐state loading stage are compared with the results of the experiments as well as the steady‐state analysis. The three‐dimensional deformed pattern involving warping at the extruded end due to torsional deformation mode is demonstrated. For twisted clover and trocoidal gear sections, the twisted angle of an extruded product is smaller than that of the die, and the simpler the shape of the sections, the larger the amount of the deviation.