Tube bulging test: Theoretical analysis and numerical validation

To perform pertinent numerical simulations of tube hydroforming process, it has been demonstrated that material data obtained from tube bulging test were more suitable than the classical tensile test. Theoretical developments based on a novel geometrical modeling have led to an analytical evaluation of the strain and stress states all over the bulged part of the tube. Errors due to imprecision of the measure location and geometrical imperfection of tube can be linked to errors on stress and strain evaluation by a differential analysis of the analytical model. At last, to validate the model, numerical results obtained from FE simulation of tube bulging test have been used as experimental data. In that way, it is shown that: - hardening curves can be obtained through the measurement of internal pressure and bulge height; - thickness variation along the bulged part of the tube can be calculated; - scattering on the hardening curve can be evaluated by using inaccuracy of the measurement point location during experiments and manufacturing tolerances on tube thickness.