Aluminium sheet forming at elevated temperatures

The formability of aluminum sheet depends on the temperature of the material and the strain rate. E.g. the limiting drawing ratio can be improved by increasing the temperature uniformly, but even more by heating the flange and cooling the punch. To accurately simulate the deep drawing or stretching of aluminum sheet at elevated temperatures, a material model is required that incorporates the temperature and strain-rate dependency. In this paper simulations are presented of the deep drawing of a cylindrical cup, using axi-symmetric elements. Two material models are compared. First a phenomenological material model is used, in which the parameters of a Ludwik–Nadai hardening curve are made temperature and strain-rate dependent. Then a physically-based model, according to Bergstr¨om is used. The model incorporates the influence of the temperature on the flow stress and on the hardening rate and includes dynamic recovery aspect