一种可考虑弯曲效应的多步法及其在矩形管拉弯成形中的应用

多步法可以考虑变形历史，也顺应了多工步成形的需要，在板料成形的数值模拟中有着良好的应用前景。但传统的多步法主要是基于膜单元的，没有能够准确地考虑成形中的弯曲效应，不适合模拟弯曲变形占主导的成形过程，如型材的拉弯成形。为此，本文将无转动自由度的BST壳单元引入，通过单元片内四个相邻单元，方便地计算出相邻构型的曲率，并通过...

A new multi-step approach considering bending effects and its application in the stretch bending of rectangular tubes

Multi-step approach can take the deformation history into account, adapts to multi-stage forming and has a good application prospect in the simulation of sheet metal forming. But traditional multi-step approaches are mostly based on the membrane element without considering bending effects exactly, not suited to the bending-dominated process, such as the stretch bending of profiles etc. Therefore the rotation-free BST element is introduced here to describe deformation, in which the curvatures are computed by a patch of four adjacent elements. Then using the principle of extremum work and the BST element, a new multi-step formulation is presented, in which the penalty method is adopted to treat the contact between the workpiece and bending tools. Based on the formulation, a program has been developed and utilized to simulate the process for stretch bending of rectangular tubes within six large steps, including pre-stretch and bending, with special attentions paid on the cross sectional distortions and springback problems. The numerical results basically agree with those of incremental analysis and experiments.