INVESTIGATION INTO NON-STEADY-STATE 3-DIMENSIONAL HELICAL EXTRUSION OF TWISTED SECTIONS BY THE RIGID-PLASTIC FINITE-ELEMENT METHOD

In metal forming, there are problems with recurrent geometric characte ristics 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 finit e element analysis for helical extrusion of twisted clover and trocoid al gear sections through a curved die. A boundary-directed remeshing s cheme based on the modular remeshing technique has been proposed to re duce the errors arising in mapping of variables between old and new me sh systems. The computed extrusion pressures in reaching the near stea dy-state loading stage are compared with the results of the experiment s as well as the steady-state analysis. The three-dimensional deformed pattern involving warping at the extruded end due to torsional deform ation mode is demonstrated. For twisted clover and trocoidal gear sect ions, 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 am ount of the deviation.