On the Study of the Sheet Bendability in AA5754-O Temper Alloy
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INTRODUCTION
BENDING is an important forming property in a range of application and extensively used in the auto industry. For a monolithic sheet under bending, Datsko and Yang[1] have shown that the area reduction (or macroscopic fracture strain) and bendability are related, with the assumption that failure occurs in the outer surface of a material being bent when the true strain occured equals the true strain at the instant of fracture. Since bending occurs in plane strain, the correlation should be with the plane strain fracture strain but a relationship can be made with the tensile fracture strain. For monolithic automotive aluminum alloys, bendability has been shown by some experiments, such as the cantilever bend test and the wrap bend test, to be strongly correlated with the material microstructures.[2,3] Davidkov et al.[4] used the digital image correlation system to measure strain localization and studied the damage development during bending of Al-Mg alloy sheets. The strain concentration inside intensive shear bands formed during bending was found to be considerably larger than the macrostrains typically suggested by the forming limit diagrams for aluminum sheet materials. Besides experimental work, numerical studies on bending behavior have been carried out. Effects of typical textures on shear band formation in plane strain tension/compression and bending were studied by Kuroda and Tvergaard.[5] Besides the study of texture and material properties on the bending performance, Dao and Li[6] investigated the influence of second-phase particle position and distribution on pure bending. Shingo et al.[7] investigated the effects of crystal Y. SHI, Researcher, and P.D. WU, Professor, are with the Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada. Contact e-mails: [email protected], [email protected] H. JIN, Research Scientist, is with CRanmetMATERIALS, Natural Resources Canada, 183 Longwood Road South, Hamilton, ON, L8P 0A5, Canada. D.J. LLOYD, Consultant, is with Aluminum Materials Consultants, 106 Nicholsons Point Road, Bath, ON, K0H 1G0, Canada. Manuscript submitted December 10, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS A
orientation on the bendability of aluminum alloy sheets by experiments using single-crystal specimens and the finite element analysis using a crystal plasticity model. In the experimental investigation, single-crystal specimens having {001}h100i Cube and {011}h100i Goss orientations were made from a coarse-grained Al-Si-Mg alloy sheet. Their finite element analysis results are remarkably consistent with the experimental results. AA5754 Al-Mg sheet products supplied in the fully annealed condition (O temper) have been widely used as automotive inner and structural panels. The bendability is extremely important because these panels are usually formed by bending. To investigate the possibility of improving the bendability in AA5754 by modification of crystallographic texture, two AA5754 sheets with very different volume fractions
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