Influence of the temperature on residual stresses and springback effect in an aluminium alloy

This study deals with the experimental and numerical investigation of springback in an aluminium alloy at different temperatures. An experimental split-ring test is performed on a AA5754-O alloy using a laboratory drawing device. The influence of temperature during forming over springback is measured from room temperature to 200 °C. The temperature is the same for all tools and is maintained constant during all the forming process. The experimental results are compared to numerical simulations performed with the finite element code Abaqus. Material parameters are identified using uniaxial tensile tests at different temperatures and several strain rates in order to take into account both temperature and viscous effects in a coupled thermomechanical constitutive law. The stress and strain states in the cup at the end of the drawing and after springback are analyzed as a function of temperature and a detailed study of stress distributions in the thickness of the blank is proposed. It is shown that the effect of temperature tends to decrease the stress gradient in the cup wall that is directly linked to the decrease of the springback opening of the ring. The distribution of the hoop stress in the cup wall is the main factor influencing the springback mechanism in warm forming condition.