Abstract
Warm U-draw bending tests were performed on a 5182 aluminum alloy under isothermal and non-isothermal conditions, and the amounts of springback under the corresponding conditions were measured. Finite element method analyses were then conducted to calculate the tangential stress distribution on the cross-section of the sheet during the warm forming process. It was found that the experimentally measured springback values were proportionally related to the differences in the amounts of tangential stresses at the top and bottom layers of the sheet section. A functional model that can account for the correlation between the amount of springback and the difference in tangential stresses at the top and bottom layers of the sheet section was derived based on an Euler beam and a nonlinear flow stress model with temperature and strain rate dependencies. The developed model, which can predict springback behavior using only results of forming analyses of warm formed aluminum alloy sheets, is anticipated to provide for advancements in the understanding of springback behavior at warm temperatures and improve the efficiency of design and analysis processes used to fabricate parts with complicated shapes by saving considerable time and costs for the analysis of springback.
Highlights
The application of aluminum alloys to automobile structural and body parts has been attractive from the viewpoint of improving vehicle fuel efficiency [1]
Aluminum alloys have low formability compared to steels at room temperatures and large springback at room temperature, which limit the widespread use of aluminum alloys in the automotive industry and have seen limited use for the production of parts with high shape complexity
We examine whether such results can be rationalized and present a springback prediction model that can utilize the tangential stress data obtained from the FEM forming analysis
Summary
The application of aluminum alloys to automobile structural and body parts has been attractive from the viewpoint of improving vehicle fuel efficiency [1]. Hot forming and warm forming methods have been studied and applied to improve the formability of aluminum alloys. Ismail and Mohamed [2] reviewed various forming techniques applicable to aluminum alloy sheets. Naka et al [3] experimentally investigated the effects of temperature and forming speed on the forming limit of 5083 aluminum alloy sheets with fine grains. Rashid et al [5] proposed the quick plastic forming, which is a method of stretching magnesium-containing aluminum alloy sheets into intricate shapes as required for automotive body panels. Hot forming has an advantage when fabricating aluminum alloys into complicated shapes with sharp corners and small radii. Unlike hot forming, warm forming does not provide high ductility to the materials because its working temperature range (200 to 400 ◦ C)
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