Further investigation of the hydrostatic bulge test in a plasticity laboratory

In plasticity theory, the effective stress-strain curve of a metal is independent of the loading path. The simplest loading path to obtain the effective stress-strain curve is a uniaxial tensile test. In order to demonstrate in a plasticity laboratory that the stress-strain curve is independent of the loading path, the hydrostatic bulge test has been used to provide a balanced biaxial tensile stress state. In our plasticity laboratory we compared several different theories for the hydrostatic bulge test for the determination of the effective stress-strain curve for two representative metals, brass and aluminium alloy. Finite element analysis (FEA) was performed based on the uniaxial tension test data. It was shown that the effective stress-strain curve obtained from the biaxial tensile test (hydrostatic bulge test) had a good correlation with that obtained in the uniaxial tensile test and agreed well with the analytical and FEA results. This paper may be used to support an experimental and numerical laboratory in teaching the concepts of effective stress and strain in plasticity theory.