ON THE USE OF CONSTITUTIVE INTERNAL VARIABLE EQUATIONS FOR THERMAL STRESS PREDICTIONS IN ALUMINUM CASTING

Abstract

The report discusses the use of constitutive equations with internal variables in mathematical calculations of the thermally induced strains and stresses that arise during casting of aluminum. Application of the so-called MATMOD (MATerials MODel) constitutive relations for the viscoplastic deformation of the material is first discussed in relation to the specific characteristics of the casting process. Some numerical time integrations of the one-dimensional version of the MATMOD equations that are relevant for aluminum casting are then presented. The evolution of temperature and total strain are here chosen to be close to values experienced in the direct chill (D.C.) casting process, and values for thermally induced strains and stresses are calculated. The results are compared with predictions based on the traditional approach, in which a set of representative stress-strain curves at different constant temperatures and strain rates constitute the complete description of the viscoplastic deformation.