Numerical simulation for twisting cold bending process and spring-back of boiler pipe

A FEM simulation model for twisting cold bend forming of boiler pipe was established. The three processes of pipe bend forming were simulated by the numbers in the round, including prepressing for deformation compensantion, twisting bending and deformation spring-back of pipe after releasing mould. Many significant aspects for boiler pipe bending were analyzed, comprising the distributing characteristics of stress and plastic strain of pipe after bending; the effects of different forming parameters such as boost force and prepressing value on the cross-section ellipticity and the ratio of wall-thickness reduction of pipe after forming; the bending results comprising of several load-cases in which the relative wall-thickness of pipe model were different and the spring-back law of pipe bending. It showes that: the bending stress of pipe mainly concentrated on initial portion of bending before spring-back; there was an optimum value of the boost force that makes the bending quality of pipe optimal; the bigger the value of the relative wall-thickness of pipe was, the better the bending forming of the pipe was; the spring-back angle of pipe bending approximated 0.05rad, which was independent of the relative wall-thickness of pipe.