Modeling of AlMg sheet forming at elevated temperatures

摘要

The process limits of aluminum sheet forming processes can be improved by controlling local flow behavior by means of elevated temperatures and temperature gradients. In order to accurately model the deep drawing or stretching of aluminum sheet at elevated temperatures, a model is required that incorporates the temperature and strain-rate dependency of the material. In this paper two models are compared: a phenomenological material model in which the parameters of a Ludwik-Nadai hardening curve and a power law strain-rate influence are made temperature dependent and a physically-based model according to Bergstrom. The model incorporates the influence of the temperature on the flow stress and on the hardening rate and includes dynamic recovery aspects. Although both models can befitted quite well to monotonic tensile tests of an AA 5754-O alloy, large differences appear if strain rate jumps are applied. Subsequent simulation of cylindrical cup deep drawing shows a large influence of friction and the shape of the yield surface.