An inverse energy approach to determine the flow stress of tubular materials for hydroforming applications

The accuracy of finite element method simulations of tube hydroforming (THF) is strongly dependent on the parameters of the flow stress law used to describe the plasticity of the tubular materials used. The hydraulic bulge test has been previously proposed as a quality control tool on incoming tubular materials, as well as a simple and effective way to obtain hardening and formability data directly from the tubes, rather than from the sheets used to roll-form the tubes. The present study describes an inverse approach for the determination of the flow stress of tubular materials from the bulge test, based on an energy balance. The proposed technique is very simple and therefore suitable to be used on any hydroforming press, as well as in simple bulging tooling.