Forming limit analysis of AA5052 sheet under bilinear strain path by designing a novel large-scale gripping fixture

The combined strain paths have significant effects on the formability on the sheet metal. In this work, aiming at a widely-used AA5052-O sheet metal, the uniaxial tension and the Nakazima tests were conducted on the large-scale specimens subjected to the pre-tension deformation. First, a novel gripping fixture was designed and manufactured to achieve the uniform pre-strains of the large specimen. Then, two types of strain paths of the tension - tension and tension - bulging were implemented to reveal the evolutions of the mechanical properties and forming limit curves (FLCs), respectively. Moreover, the forming limit stress curves (FLSCs), which are more insensitive to the changes of strain paths, are calculated from the experimental FLCs to improve the prediction accuracy of finite element (FE) simulations. Compared to the conventional necking criterion of path transition and the FLC criterion, the FLSC criterion can effectively enhance the simulation precision in the biaxial tension region.