Kinematics of Portevin-Le Chatelier bands in simple shear

The mechanical behavior of 5000 series aluminium alloy sheets has been investigated in simple shear, in order to highlight the influence of strain rate and temperature on the occurrence of plastic instabilities. Indeed, as in tension, Portevin-Le Chatelier effect is also observed in simple shear and the aim of this study is to investigate the characteristics and kinetics of the bands of localized deformation under such a strain/stress state. Jerky flow and localized deformation are observed from room temperature up to 100 degrees C but disappear at 150 degrees C or above. A critical shear strain for the occurrence of jerky flow is evidenced at 100 degrees C but it starts from the beginning of the test at room temperature. Concerning the bands, there are initially aligned with the applied load direction and rotate as the shear strain increases, similarly to the material frame. Finally, both McCormick and Johnson -Cook models were used to perform the numerical simulation of the shear tests, in order to compare the predicted load drops and kinetics of the bands with experiments. (C) 2014 Elsevier Ltd. All rights reserved.