Published: Jul 1978
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The objective was to develop forming limit curve (FLCs),tensile(elastic and plastic) properties, and production stretch-form test data for two alloys.
A laboratory technique developed by Hecker and his associates at General Motors Research Laboratories was used to develop FLCs for 2024-T3 and 2219-T31 aluminum alloys. This laboratory technique involves biaxial punch-stretch testing of sheet metal specimens clamped securely between two die plates at the periphery. Using this technique, the influences of sheet thickness, lubrication, blank size, and blank orientation on forming limits were investigated.
The values of the strain-hardening exponent and plastic strain ratio calculated for 2024-T3 and 2219-T31 aluminum alloys are in good agreement with those for other aluminum alloys reported by Hecker. The strain-hardening exponent, n, was found to be higher for 2219-T31 than for 2024-T3. The average plastic strain ratios, r, for 2024-T3 were higher than for those for 2219-T31 in all three test directions.
All FLCs measured in the laboratory were found to be in good agreement with production stretch-form test data.
formability, stretch forming, aluminum alloys, anisotropy, strain hardening, plastic strain, tension tests
Senior manufacturing research and development engineer, West Palm Beach, Fla