Numerical modelling and formability of with and without heat-treated AA 6023-T6 alloy sheet with various necking/failure criteria

Abstract

Sheet metal forming is a process widely used in the manufacturing industry. There are numerous sheet metal forming processes to evaluate and understand the formability. Among all formability tests, the basic formability can be formulated through tensile tests and followed with specialized tests. In the present paper, the formability of AA 6023-T6 sheet of 2mm thickness by modelling for stretching test namely limit dome height (LDH) test was performed using PAM STAMP 2G a commercial finite element software. For the simulation, input mechanical properties like yield strength (c), material strength coefficient (K), strain hardening exponent (n), plastic strain ratio (R) etc., were considered from the existing literature. For the simulation, two different conditioned sheet such as at room temperature and annealed sheet at 400°C. For all the simulations, four strain paths 100 × 200mm, 125 × 200mm, 150 × 200mm, 175 × 200mm and 200 × 200 mm were taken. Results are drawn based on the three localized necking criteria namely the effective strain rate-based criterion (ESRC – R1), major strain rate-based criterion (MSRC –R2), thickness strain rate-based criterion (TSRC – R3). Form the obtained results, forming limit diagrams are developed for the both condition of sheet metal. It is observed that, formability of AA 6023-T6 sheet in-plane condition (i.e. 100x100 mm) annealed sheet at 400°C is shown better forming whereas in bi-axial condition (i.e. 200x200 mm) got reduced compared to room temperature sheet. The same phenomenon is noted in all the necking criteria too.