Design of a gas forming technology using the material constants obtained by tensile and free bulging testing

Uniaxial tensile testing is a most common way of obtaining the information about the constitutive behavior of a material during gas forming. At the same time for industrial applications it is important to know the material behavior in a biaxial tension mode, which is much closer to the one realized in a shell during forming process. The paper focused on the investigation of the differences between the gas forming technologies designed in FEM based CAE system using the material parameters obtained in conditions of uniaxial and biaxial tension. The rheological characteristics of AMg6 aluminum alloy obtained by tensile and free bulging testing are analyzed and compared. The comparison shows that the constitutive data obtained by these methods are different. The effect which these differences could provide to the design of a gas forming technology was studied. A pressure regime for an aircraft part forming which maintains the maximum strain rate at constant level was calculated using finite element simulation for the both sets of constitutive constants. The calculated pressure regimes were then realized experimentally and the differences between the deformed specimens were analyzed.

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