Analysis of torsional deformation by rigid-plastic finite element method using recurrent boundary conditions

In metal forming, there are problems with recurrent geometric characteristics and without explicitly prescribed boundary conditions. In such problems, for effective saving in computational time, so-called recurrent boundary conditions must be introduced. The present study deals with rigid-plastic finite element analysis for torsions of circular, square and rectangular bar sections. The application of recurrent boundary condition to the torsion problems has been shown to be effective and valid. The torsional torques computed by the present method are compared with those by the analytical method. Both pure torsion and warping-restraint torsion are computed and compared between the two in torque and deformation pattern. It is proven that spring-back can be predicted reasonably by rigid-plastic loading and elastic unloading.