Experimental investigation of punch curvature influence in Nakazima test and numerical FLD prediction of AA5086

Abstract

In this article, the influence of punch curvature on the forming limit curve (FLC) of AA5086 aluminum alloy sheet was studied by Nakazima test. Based on the digital image correlation (DIC) and the position-dependent method, the FLC of AA5086 aluminum alloy sheet was built, and the strain paths evolution during Nakazima test was analyzed. It was found that both the determined FLCs presented a phenomenon of shifting to the right side, and the FLCs with Φ44.45 mm punch was generally higher than that with Φ100 mm punch. The strain paths analyses show that the geometrical shape of the hemispherical punch leads to a biaxial pre-strain tension at the initial stage of the deformation. Furthermore, numerical simulation of Nakazima model was carried out to predict the FLC. For FE Nakazima model, the friction coefficient was calibrated according to strain path evolution. With a proper friction coefficient, the FE model presents a good FLC prediction compared to experimental results.

Keywords:

• Forming limit curve
• AA5086
• punch curvature
• Nakazima test
• strain paths

Additional information

Funding

This work was supported by the [Natural Science Foundation of Shandong Province] under grant [number ZR2019MEE008], [National Natural Science Foundation of China] under grant [number 51405266] and [Young Scholars Program of Shandong University, Weihai] under grant [YSPSDUWH].