| Finite element method is widely used to simulate bulk metal forming processes in recent years. Though finite element method is maturing in the simulation of metal forming processes, it has been a difficulty to deal with frictional conditions at the tool-workpiece interface. The frictional condition is usually simplified according to reality. Friction models normally applied in finite element analyses for bulk metal forming are the constant friction model and arctangent friction model. However frictional conditions are often variational in realistic metal forming processes. Tribology is an important factor that affects accuracy of finite element analyses.Tribological specialties and major influencing factors of bulk metal forming is discussed in the present research. A friction model of bulk metal forming including the influence of temperature, normal pressure and strain on the tool-workpiece interface is developed on the basis of friction model developed by Chen and Kobayashi. And the friction model is coupled to a finite element code named MSC.SuperForm so that the finite element code can consider the influence of velocity, temperature, normal stress and strain on the boundary conditions.Thermodynamic couple numerical simulation of ring compression of pure aluminum and tube extrusion of superalloy GH4169 is done by adopting the constant friction model and the present friction model in the paper. Numerical results are compared with experimental investigations to validate the correction and nicety of the present friction model of bulk metal forming processes. The accuracy of the finite element simulation of bulk forming processes can be improved by adopting the present friction model.The present friction model is used for simulating isothermal forming process of the disk of superalloy GH4169 subsequently. The metal flowing rule during forming process of the disk and the distributed rules of the effective strain inside of forging are revealed.
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