Optical Measurement of Forming Limit and Formability of Cu/Al Clad Metals

A digital image deformation measurement and analysis control system (XJTUDIC 8.0) was employed to measure the forming limit strain for Cu/Al clad metals produced via explosive welding technique. A contrast test between the digital image correlation (DIC) method and the conventional grid method was also implemented using the SPCC sheet metal forming limit test. The effect of heat treatment and contact status on forming limit was discussed based on the forming limit strain of Cu/Al clad metals. The interfacial and fracture structures were analyzed using scanning electron microscopy. The fracture site was predicted by finite element method. Results demonstrate that the forming limit curve of Cu/Al clad metals through DIC is more likely to reflect the formability of SPCC accurately. The forming limit of the clad with Al in the inner layer is higher than that of the clad with Cu in the inner layer. The formability of the annealed clads is superior to that of the non-annealed clads. The local interface failure induces the microcracks in Cu/Al clad metals during the forming process, which could be the main failure mode. With the finite element method, the fracture location of Cu/Al clad metals caused by uniaxial tensile during the forming limit test using DIC method is predicted accurately.