PREDICTION AND MEASUREMENT OF RESIDUAL STRESSES/STRAINS IN A DIRECT CHILL CASTING MAGNESIUM ALLOY BILLET

摘要

In order to investigate defect formation such as hot tearing and cold cracking, a thermo-mechanical finite element (FE) model for analyzing the DC casting of an AZ31 magnesium billet has been developed. This numerical model simulates the evolution of temperatures, stresses and strains inside the billet. Thermal boundary conditions have been selected based on knowledge of the physical process and in reference to trends shown by the measured temperature data. The temperature predictions are in good agreement with the measurements for both transient and steady state conditions. Experimental investigations were performed with a Gleeble 3500 thermo-mechanical simulator on an AZ31 alloy to determine the material constitutive behaviour. Residual strain measurements were carried out at Atomic Energy Canada Ltd. (AECL) using Neutron Diffraction. Strain measurements in the radial, axial and hoop orientations were made at a variety of axial and radial locations in the billet. The measured strains were compared with the model predicted results and used to validate the thermo-mechanical model.