Evaluation of Pneumatic Bulge Test Experiments and Corresponding Numerical Forming Simulations
Jens Kappes and Mathias Liewald
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DOI:10.17265/2161-6221/2011.09.011
Institute for Metal Forming Technology (IFU), Holzgartenstr. 17, Stuttgart 70174, Germany
Superplastic forming of sheet metal exhibits numerous technical and economical advantages for manufacturing complex part geometries, which enables the potential of lightweight production (e.g., of vehicle bodies), especially for niche types. Within virtual engineering tasks, material parameters in combination with numerical sheet metal forming simulations are crucial. In such context, the selected testing procedure should be as similar as possible to the subsequent forming technique. For that reason the pneumatic bulge test represents an appropriate testing procedure for the most common superplastic sheet metal forming process, the blow-forming process [1-4]. This paper deals with pneumatic bulge test experiments at constant forming pressures using the aluminum alloy AA5083 (initial sheet thickness s0 = 1.5 mm). Due to in-situ measurement of strains in pneumatic bulging, material parameters can be determined. These material parameters can be used for an interpolation, in this case the power law, to determine material constant C, strain-hardening exponent n and strain-rate sensitivity index m using the least square error method. Furthermore, the superplastic forming process was simulated by FE modeling with material parameters exclusively determined from pneumatic bulging. The comparison of numerical and experimental results showed good correlation for the observed conditions.
Superplastic, pneumatic bulge test, in-situ strain measurement, numerical forming simulation.