Experimental and numerical study on effect of forming rate on AA5086 sheet formability

With increasing application of aluminum alloys in automotive or aeronautic industries, it is necessary to characterize their deformation behaviors at large strains, high strain rates and elevated temperatures, which is relatively lacking today. The aim of this paper is to experimentally and numerically investigate the influence of forming rate and temperature on formability of an AA5086 sheet. Firstly, tensile tests are carried out at different temperatures (20, 230, 290 and 350 °C) and at different forming rates (10, 750 and 1000 mm/s). A technique of digital image correlation (DIC) associated with a high-speed camera is applied to evaluate the surface strains and a complete procedure is built to detect the onset of localized necking during the experiments. The influences of initial testing temperature and forming rate on the sheet formability are analyzed. Then in order to numerically determine the formability of this sheet, a form of Voce's constitutive law taking into account the temperature and strain rate is proposed. An inverse analysis is carried out to identify the material parameters of the law for the tested aluminum alloy. Finally, with the above identified law, tensile tests are simulated. The experimental and numerical results show that the testing temperature and forming rate have a great influence on sheet formability. At high forming rates, the sheet formability of AA5086 is lowered up to a certain temperature, above this temperature, the formability is greatly enhanced. Furthermore, the agreement between experimental and numerical results indicates that the proposed constitutive law and the identified material parameters can be appropriate to model the sensitivity of AA5086 sheet towards strain rate and temperature.