Determination of tube material hardening law using bulging tests

ABSTRACT: The paper is focused on the determination of mechanical characteristics for metallic materials shaped like tubes as used in tube hydroforming process. First, a procedure is described to carry out experimental tube bulging tests. It permits to identify a law linking the internal pressure to the bulge height. Second, based on this law and an original geometric modelling, strain and stress can be evaluated all over the free bulge zone of the tube. Third, numerical results obtained by finite element simulation are treated to validate the experimental behaviour law of the tube. It is shown that: measuring experimentally internal pressure and bulge height during tube bulging allows to determine tube hardening law and thickness distribution along the bulging area; a devia-tion of 2 % is noticed between numerical and experimental results