FINITE-ELEMENT MODELING OF METALWORKING PROCESSES FOR THERMO-VISCOPLASTIC ANALYSIS.

摘要

In this investigation a coupled analysis of viscoplastic deformation and heat transfer is made. The objective is the application to metal forming processes in the warm and hot range.;A finite element scheme is developed implementing the above theory. An implict scheme is used for the time integration of heat transfer equations, which is coupled to the plasticity equations.;The formulation is tested with the simulation of cylinder and ring compressions, both at room and high temperatures. The calculated results agree very well with the experimental evidence available and establish the applicability of the method to hot forging. Strain-rate effects are investigated in the punch stretching of sheet metals.;Finally, pancake forgings of the titanium alloy Ti 6242 (0.1Si), both single (alpha) + (beta) phase and dual phase ((alpha) + (beta)/(beta)) are simulated. The results obtained are used to correlate macroscopic variables with observations on the microstructures. This sets the finite element calculations as a tool to select forging conditions, and to obtain desired mechanical properties.;Strain rate effects are incorporated in the infinitesimal theory of rigid plastic materials, based on experimental evidence. A theory of dissipative materials based in rational thermodynamics is adapted to rigid-thermoviscoplastic analysis of metal forming problems. Internal structure changes due to plastic deformation are described by means of internal parameters.