A simple and efficient method has been proposed in order to determine the dynamic speed boundary condition caused by the guide rolls for developing the 3D-FE model of cold ring rolling process rapidly. The concept of the motion track of guide rolls has been put forward firstly and an optimal motion track and track type are given by simulation. Meanwhile, an effect of the guide rolls on the ring tilting and ring circularity was simulated and analyzed. The result shows that the simulation results are in good agreement with experiment results from the literature.

Based on the rigid-plastic finite element method (FEM) principle, a three-dimensional (3D) rigid-plastic FE simulation system named TB S-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 difierent 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.

A blade with a damper platform, with excellent anti-vibration characteristics and high efficiency, has become one of the most important new types of blade being developed in the aeronautical engine. However, the blade is complicated in shape, and the material used for its manufacture is difficult to deform. Therefore, it is important to undertake research on the blade-oriented precision forging process using threedimensional finite element method (3D FEM) method numerical simulation for the practice and the development of the process. However, up to now, literature on such research has been scant. In this paper, based on the rigid–viscoplastic principle, three-dimensional finite element simulation is reported for the isothermal precision forging of the blade using the penalty function, and eight-node hexahedral isoparameteric elements for discretizing the deforming workpiece and triangular elements for discretizing the die cavity. The method of contracting from the boundary to the interior, proposed by the authors, is used for remeshing a distorted mesh system, and the method of modifying the position of nodes touching the die according to its original normal, also proposed by the authors, is used to avoid the "dead lock" problem due to the normal uncontinuity of scatted die meshes, to enable the simulation to be successful. Friction is considered for the die-workpiece interface boundary condition, and an arc is considered for the tenon-body joint, and a damper platform-body joint on the blade die cavity, respectively, which make it possible for the simulation to approach the practical forging process of a blade with a damper platform. 3D FEM simulation results have been obtained for the initial and deformed configurations, the deformed meshes of typical cross-sections, the distribution of effective strain at the final stage, load–displacement curves, in this way the deformation law of the forging of a blade with a damper platform being revealed. The achievements of this research serve as a significant guide to the optimization of design for the relevant process and dies. The method used is also of general significance to the forging processes of other type of blades and other complicated massive deformation processes.© 2002 Elsevier Science B.V. All rights reserved.

The in-plane bending of a strip metal workpiece under unequal compression can be developed into an advanced precision forming process with high quality, high ef

A definition of forming limit is given with minimum centerline radius min R before wrinkling for NC bending process of thin-walled tube. Based on the developed FEM wrinkling prediction system TBWS-3D, an effective searching algorithm of wrinkling limit is proposed and forming limit can be obtained conveniently. Thus influence laws of main forming parameters on wrinkling limit are investigated and revealed. Measures to improve forming limit is put forward consequently. The achievements may help to both practice of thin-walled precise tube bending and research of plastic wrinkling.