A study on a 3D FE simulation method of the NC bending process of thin-walled tube

Abstract

Based on the rigid–plastic finite element method (FEM) principle, a three-dimensional (3D) rigid–plastic FE simulation system named TBS-3D (tube bending simulation by 3D FEM) for the NC bending process of thin-walled tube has been developed, and a reasonable FEM model has been established. By the use of this FE simulation system, an NC bending process of thin-walled tube has been simulated, and deformed meshes under different bending stages, the stress distribution along the bending direction, and the relationship between the maximal wall thickness changing ratio and the bending angle have been obtained. Some forming laws of NC tube bending obtained are as follows: (1) the NC bending process make tube elongate to some extent; (2) the characteristic of the stress distribution is that the outer area is undergoing tensile stress, the inner area is undergoing compression stress, and the stress neutral layer moves close to the inner area, which is in good accordance with practice; (3) the maximal wall thinning ratio in the outer tensile area changes only a little with increase of the bending angle, and the maximal wall thickening ratio in the inner compression area increases linearly with bending angle. The above results show that 3D FE simulation is an important and valid tool for analyzing the NC bending process of tube, this research being beneficial for the practical tube bending process, and may serve as a significant guide to the practice of the relevant processes.