1.12 - Material Properties for Numerical Calculations

Abstract

This article examines the accuracy of numerical simulations of metal forming processes and focuses on the interplay between material characterization and constitutive modeling on the accuracy of the numerical model. It also examines the response of light metals (aluminum and magnesium alloy sheets) to forming at elevated temperatures. Aluminum alloys exhibit strong rate sensitivity at temperatures in the warm forming regime (100–300°C), and proper constitutive characterization and numerical representation of rate sensitivity is shown to be important in deep drawing simulations. Magnesium alloys are strongly rate sensitive at both room and elevated temperatures. Anisotropy is shown to be important in modeling aluminum and magnesium alloys, and advanced yield criteria with fits to directional variation in both strength and r-value is necessary. Magnesium alloys also exhibit strong tension-compression asymmetry due to twinning under compression, mandating compressive characterization of sheet alloys, which can be difficult. Magnesium alloys also display significant yield surface evolution, which should be captured using advanced constitutive models. In contrast, the assumption of a constant yield surface shape is acceptable for many commercial aluminum sheet alloys.