Determination of tubular material parameters in bulging test with three-dimensional digital image correlation method

Tubular material parameters play a major role in part manufactory process planning and reliable finite element simulations. The hydraulic bulging test is one of the most credible ways to determinate tubular material properties, especially flow stress. In this paper, an on-line measurement method based on three-dimensional (3D) digital image correlation method (DIC) is applied to determinate material parameters of tube using Swift law. Both a practical bulging machine and a self-developed measurement system are introduced. The free-bulging test is performed for AlMg2.5 aluminum alloy tube. The axial curvature radius is calculated by extracting the bulging profile based on the cosine model and the axial strain is computed accurately by tracking a series of points around the pole dome. Finite element simulations on tube are conducted to validate the method. The results indicate that the material parameters obtained from the present method are reliable to define the flow stress in the tube hydroforming process.