A one phase thermomechanical model for the numerical simulation of semi-solid material behavior. Application to thixoforming

作者：Koeune R; Ponthot J P^*

来源：International Journal of Plasticity, 2014, 58: 120-153.

DOI：10.1016/j.ijplas.2014.01.004

• Continuous fluid-solid transition
• Thermo-mechanical coupling
• Thermo-elasto-viscoplastic constitutive modeling
• Thixoforming
• Semi-solid material behavior

This work deals with the development of an appropriate constitutive model for semi-solid thixoforming processes of metallic alloys. These processes rely on a very specific material behavior called thixotropy that can be displayed by some metallic alloys heated up to their semi-solid state. It is a particular evolutionary behavior which is characterized by a solid-like behavior at rest and a liquid flow during shearing, thus by a decrease of the viscosity and of the resistance to deformation while sheared. %26lt;br%26gt;An original one-phase thermo-elasto-viscoplastic constitutive model has been developed. The basic idea is to extend the classical isotropic hardening and viscosity models beyond the solid state by considering two more non-dimensional internal scalar parameters. The semi-solid state is treated as a particular case, and one of the main features of the proposed constitutive model is that it remains valid over a wide range of temperatures, starting from room temperature to above the liquidus in a continuous manner, thus allowing a continuous transition between classical solid and fluid behavior. %26lt;br%26gt;Another feature is that, after the forming step, it is possible to simulate the cooling down of the component back to room temperature using the elastic-viscoplastic model. So it is possible to estimate residual stresses, something that is definitely impossible while using a fluid-like model or a rigid viscoplastic approach. %26lt;br%26gt;The presented model is illustrated and validated by means of representative numerical applications, as two different extrusion tests are carried out and the computed predictions are compared to experimental results.

• 出版日期2014-7