Simulation of Forming Limit Diagrams for Multilayer AL ۷۰۷۵-T۶ and Copper Sheets Using the Johnson–Cook Failure Criterion

In this study, the formability of multilayer Al۷۰۷۵ T۶/Cu sheets with ۲-, ۴-, ۸-, and ۱۶-layer configurations was investigated under the Johnson–Cook failure criterion using forming limit diagram (FLD) tests and numerical simulations in Abaqus. The results indicated that with an increasing number of layers, the major strain (ε۱_max) decreased while the minor strain (ε۲_max) increased, reflecting a transition from uniaxial to biaxial stress states in thicker layers. The absorbed energy and overall strength of the specimens increased with the number of layers, but the overall ductility decreased. Stress analysis and interfacial parameter evaluation revealed improved stress distribution, although strain localization at the interfaces increased, raising the risk of interfacial delamination. Abaqus simulations using the Johnson–Cook model showed good agreement with experimental results and highlighted that controlling interfacial parameters and precise model calibration are crucial for predicting the behavior of multilayer sheets. The findings are valuable for the optimal design of robust laminated sheets and failure prediction in industrial applications such as aerospace and automotive engineering.

Keywords:

Forming limit diagram (FLD) , Al۷۰۷۵ T۶/Cu laminated sheets , Johnson–Cook damage model , multilayer metal sheet , finite element analysis (FEA) , formability