COUPLED THERMOMECHANICAL SIMULATION OF SOLIDIFICATION AND COOLING PHASES IN CASTING PROCESSES

摘要

This paper presents an up-to-date finite element numerical tool for the simulation of aluminium foundry processes. A fully coupled thermo-mechanical formulation including phase change phenomena is considered. The mathematical framework to account for both thermal and mechanical constitutive and boundary assumptions is introduced. The proposed constitutive model is consistently derived from a thermo-elasto-viscoplastic free energy function. Mechanical and thermal material properties are assumed to be temperature-dependent. A continuum transition from the initial fluid-like to the finial solid-like behavior of the part is modeled considering a temperature dependent viscoplastic-surface evolution. Phase-change contribution is taken into account assuming both latent-heat release and shrinkage effects. An accurate definition of the interfacial heat transfer between the solidifying casting and the mold is introduced as an essential ingredient to produce a reliable casting model. In fact, both the solidification process and the temperature evolution strongly depend on the heat exchange at the contact interface. This exchange is affected by the insulating effects of the air-gap due to the thermal shrinkage of the casting part during the solidification and cooling phases. The need for a so closely coupled formulation is the reason why the finite element code VULCAN, developed by the authors, is presented as an accurate, efficient and robust numerical tool, allowing the numerical simulation of solidification and cooling processes for the casting industry.