FLD(forming limit diagram) was influenced by the material properties as well as forming process, such as strain path and heat-treatment states, etc. Some experimental FLDs were constructed for 2D12 aluminum alloy in the annealed, pre-strained and various aging time conditions after solution heat-treatment by rigid punch bulging. Based on the experimental results, the FLSD (forming limit stress diagram) was determined. By comparing and analyzing the FLD and FLSD, it is indicated that the FLD of annealed condition is higher than the FLD after heat-treatment and the aging hardening lowers the FLD. The results mainly dependon the metallurgical structure transformation during solution heat treatment and the decrease of hardening value n with aging. Furthermore, aging hardening lowers the FLSD mostly because it lowers the FLD. The result may be available for the sheet forming process design and numerical simulation.
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