Residual Stresses in Bending of Bi-layer Al-Cu sheets

Bi-layer sheets are using widely in different industries. Good mechanical and physical properties are available simultaneously in these sheets. In this article, the residual stress profile has been measured experimentally at bending process of a bi-layer sheet. The bi-layer sheets are produced usually by manufacturing processes such as explosive welding. The secondary forming processes such as bending can induce extra residual stresses in addition of residual stresses induced by initial manufacturing process. An annealed Al-Cu sheet has been formed to specified curvature radius by three roll bending process. The induced residual stress is measured by creating a narrow slit in the sample. The released strain is measured by attaching a strain gauge at back surface. The residual stress profile is calculated according to Legendre polynomial basis function. The sheets thickness is equals to 4.8 mm and the slit depth in each step is 0.1 mm. The slit is created in 44 steps and experimental measurement shows maximum residual stress is equals to 30 MPa along thickness.