Abstract: The basic theory of hot forging forming process of thermodynamic couple numerical simulation in rigid-viscoplastic finite element method is presented. A thermodynamic couple equation with basic unknown quantity which is the nodal velocity and the time derivative of the nodal temperature is obtained. Using developed program system, simulate the temperature field of hot upsetting forming process of 20 steel, obtain the deformation diagram of the computational mesh which reflects hot upsetting forming flow rules and the temperature distibution diagram which reflects the temperature field's change. Comparing the upsetting load-stroke curve obtained by thermodynamic couple with the curve obtained by experiment, the two results are principally correspondent.

Key words: Finite element method, Hot forging forming, Numerical simulation, Rigid-viscoplastic, Thermodynamic couple