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.

The development of aero-space, automobile, and high-technology industries requires the development of advanced plastic processing technologies in order to manufacture parts with light weight, high strength, high precision, high efficiency and at low cost, with a short period and a friendly environment, and with intellectualization and digitization. There are key problems urgently to be solved in the research and development of advanced plastic processing technologies, and FEM numerical simulation in combination with physical modeling and theoretical analysis has been playing a more and more important role in this field. This paper reports the state-of-the-art of some advanced plastic processing technologies and their numerical simulation in the authors'laboratory, including the unequal deforming and in-plane bending process of strip metal, free deformation under dieless constraint and axial compressive precision forming process of tube, wrinkling and spring-back prediction and the NC bending precision forming process of thin-walled tubes, and precision forming laws and a complicated massive forming process such as blade forging with a damper platform.

Research on precision forming laws of complicated blade has been a challenging issue on international frontiers of plastic forming areas. The precision forging laws of the blade with a damper platform have been obtained by using 3D FE simulation and physical modeling. The laws involve in the deforming characteristics of the tenon, damper platform, middle blade body, and tip blade body, such as the unevenness of deformation and material flow, the branch-flow of material, material flow characteristic of the blade body and rotation forming characteristic of the damper platform. The research may serve as a guide to the optimization design of relevant process and dies.

In this paper, based on the establishment of a reasonable mechanics model for a typical draw-spinning, research on the first pass of the spinning process is carried out with an elasto-plastic FEM method. The distributions of the stress and strain are obtained under three types of roller-trace curves: straight lines. involute curves and quadratic curves. The distribution laws of the radial and tangential stress that are obtained can serve as a significant guide to determining the forming limits in multi-pass conventional spinning under different roller-traces. Comparison of the distributions of strain and stress of three roller-traces could provide a theoretical basis for selecting a reasonable roller-trace in multi-pass conventional spinning.

Blade precision forging is a high temperature and large plastic deformation process. Interaction of deformation and heat conduction results in producing large temperature unevenness inside the billet. The unevenness has a great effect on the mechanical property and microstructure of the forged blade. However. internal quality of the blade is decided by its microstructure, it iS necessary to conduct a research on the microstructure of the blade forging process. Taking a blade with a tenon as an object, its precision forging process is simulated and analyzed using a 3D coupled thermo-mechanical FEM code. And based on the prediction modeI of Ti-6AI-4V presented by the predecessor. a study of the evolution of grain size in the forging process is made. The distribution characteristics of grain size in typical sections are obtained under various deformation degrees. This study may provide a base for designing the blade forging process and working out its parameters.