Abstract
In this paper, the springback behavior of high strength aluminum alloy 7075 is studied by experiments and finite element (FE) simulation. Firstly, an analytical model is established to predict the springback angles and analyze the springback trend. The springback experimental tests are conducted by using the V-shaped stamping dies. The influence of deformation temperature, punch radius, and blank holder force on the springback angles is studied. Finally, an FE simulation model is performed to investigate the deformation characteristics and springback process of the aluminum alloy sheet. The results show that the change of springback angles is direct proportional to the punch radius. The springback angles increase with the decreasing deformation temperature and the increasing blank holder force. The stress relaxation that occurs during the die holding stage is the primary reason of reducing the springback compared with cold stamping. Low blank holder force will cause side wall curl, which results in the deviation of forming size. The FE simulation model considering stress relaxation is capable of precisely predicting the change of springback angles, and the simulation results exhibit good consistency with the experimental results.
Highlights
The aluminum alloy 7075 as the lightweight material has been widely used in the automotive and aerospace industry [1, 2]
According to the analytical model, the change of springback angle is influenced by two types of stress, which are the tensile stress caused by external force and the stress caused by strain hardening
The effects of experimental parameters on springback were approximately analyzed by the analytical model, and the V-shaped stamping experiments were conducted
Summary
The aluminum alloy 7075 as the lightweight material has been widely used in the automotive and aerospace industry [1, 2]. Ma et al [14] studied the influence of a series of parameters on the V-shaped part springback in the hot stamping process. An analytical model considering the sheet thickness and the neutral layer transferring was proposed by Parsa et al [17] to predict the springback of the double curved parts. The Y-U model [23, 24] describing the Bauschinger effect and work hardening can accurately predict the springback in the cold stamping process, which is a reliable prediction model. The aluminum alloy sheets are adequately heated and soaked in hot stamping process, and the anisotropic behaviors of the materials can be difficultly observed, so the various phenomena caused by the anisotropy could be negligible when forming at elevated temperatures. The springback was predicted by FE simulation model considering the stress relaxation effect in the hot stamping process
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