Cold and Warm Hydroforming of AA754-O Sheet: FE Simulations and Experiments

Abstract

The sheet hydroforming with punch (SHF‐P) process offers great potential for low and medium volume production, especially for forming: (1) lightweight sheet materials such as aluminum (Al) and magnesium (Mg) alloys and (2) thin gage high strength steels (HSS). Mg and Al alloys are being increasingly considered for automotive applications, primarily due to their lightweight and high strength‐to‐weight ratios. However, there is limited experience‐based knowledge of process parameter selection and tool design for SHF‐P of these materials. Thus, there is a need for a fundamental understanding of the influence of process parameters on part quality. This paper summarizes analyses of the SHF‐P process of AA5754‐O sheet using finite element (FE) simulations. FE simulations and preliminary experiments of SHF‐P were conducted to determine the process parameters (blank holder force versus punch stroke and pot pressure versus stroke) to form a challenging shape (a cylindrical cup with a reverse bulge) successfully at room and elevated temperature (∼150 °C). The material properties of the sheet material were obtained from tensile tests at room temperature up to 260 °C as presented by [1]. The FE model was established using PAMSTAMP 2G, Version 2009. SHF‐P experiments were conducted in order to (i) evaluate the formability of the part at room and elevated temperatures and (ii) validate FE simulation results. This study shows that the SHF‐P at elevated temperature can form a cup with larger cup height and better reverse bulge profile than SHF‐P at room temperature. Moreover, the FE predictions of part profiles and thinning distributions matched reasonably well with the experimental results.