Abstract
In order to develop a reliable constitutive model for predicting formability and springback of sheet metals during superplastic forming (SPF) and quick plastic forming (QPF), characterization of elastic-plastic behavior, as well as formability of the material is essential. In the present study, the module of elasticity, uniaxial flow behavior and anisotropy, as well as the forming limit curve (FLC) of one of an SPF/QPF grade AA5083 was investigated. The variation of Young’s modulus with temperature was measured from the uniaxial tensile tests for four temperatures ranging from 25 to 500 °C. The impact of temperature and strain rate on the flow behavior of the material was investigated via uniaxial tensile tests for three temperatures (420, 450, and 480 °C) and at three strain rates (0.001, 0.01, and 0.1 s−1). The dependency of the flow stress on the material orientation with respect to the rolling direction (0, 45, and 90°) was assessed using uniaxial tensile tests at a constant temperature. In addition, the evolution of plastic anisotropy with plastic strain and strain rate was assessed by measuring the Lankford coefficient (r-value). Finally, the FLC of the material at 450 °C was characterized according to Nakazima tests procedure for three strain paths (i.e. uniaxial tension, plane strain, and biaxial tension).
Highlights
It has been reported that aluminum alloys with fine grains (~ 10 μm), at elevated temperatures and low strain rates show superior ductility, known as superplasticity [1,2,3]
Superplastic forming (SPF)/High-Speed Blow Forming (HSBF) processes are very sensitive to the applied strain rate and temperature [2]
Similar result could be seen for AA5083 in Ref. [10]
Summary
It has been reported that aluminum alloys with fine grains (~ 10 μm), at elevated temperatures (over 0.5 of melting point) and low strain rates (less than 0.01 s-1) show superior ductility, known as superplasticity [1,2,3]. The forming limit The authors recently reported the dependency of the strain rate sensitivity index (m-value) on the applied testing method [5]. For assessing elastic modulus, isotropic hardening behavior, Lankford coefficient (r-value), and forming limit curve (FLC), several tests at different temperatures, strain rates, and materials orientations were carried out. The forming limit curve (FLC) of the studied material was measured using Nakazima punch test for three strain paths (i.e. near biaxial, near plane strain and near uniaxial). For this purpose, an inhouse test set-up was used. In order to minimize the effects of friction between the sheet sample and the tools, a graphite powder was applied on the surface of specimens before running each test
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