Simplified three-dimensional simulation of rotary piercing of seamless pipe by rigid–plastic finite-element method

A method for simulating three-dimensional deformation in rotary piercing of pipes from round bars with skewed rolls in a realistic computing time is proposed on the basis of the rigid–plastic finite-element method using generalised plane-strain modelling. In this method, the rotary piercing is approximated as a roll forging process, and the elongation of the workpiece in the rolling direction is kept uniform in the cross-section. The effect of the twisting shear deformation is included in the generalised plane-strain modelling to improve the accuracy of the calculated results. The calculated shapes of the deformed workpiece are in good agreement with the experimental ones for plasticine workpieces. In addition, the occurrence of a central crack in the rotary piercing is predicted from the calculated history of the hydrostatic stress and equivalent strain by means of the criterion of ductile fracture.