Simulation and experimental investigation of hot forming of aluminum alloy AA5182 with application towards warm forming

This study focuses on hot and warm forming properties of aluminum alloy AA5182 sheet, with attention toward warm forming, by using gas pressure to form sheet material. A temperature range of 300°C to 450°C and a pressure range of 690 kPa (100 psi) to 2410 kPa (350 psi) were used in a test matrix of twenty one different test conditions for gas-pressure forming of a sheet into hemispherical dome in a gas-pressure bulge test. Multiple sets of tensile data were used to develop a material model that predicts the dome height and shape of an axisymmetric bulge specimen at any given time during forming. In simulations of the forming process, 17 simulations of the total 21 experimental conditions showed good agreement with the experimentally measured dome heights throughout forming tests. The four cases that did not show good agreement between simulation and experiment are a result of strain-hardening in the material during forming. Strain hardening was not significant in tension testing of specimens and was not accounted for in the material model, which considered only strain rates slower than for these experimental bulge testing. This demonstrates an effect which must be considered in future simulations to predict forming approaching warm conditions. Two experimental bulge specimens were cross-sectioned post forming and grain sizes were measured to determine if grain growth occurred during the forming process. Experimental bulge specimens show no grain growth during the forming process. The tensile specimens from which the material model data were taken were measured to determine if plastic anisotropy was a possible issue. All specimens measured were proved to have deformed nearly isotropically. The results of this study show that predicting warm and hot forming of aluminum alloy AA5182 using gas pressure is possible, but that a more complex material model will be required for accurate predictions of warm forming. This is a very important step toward making hot and warm forming commercially viable mass production techniques.