determination of the critical area and reusability of compressed natural gas storage cylinder in collision

forming limit curve (flc) is an important tool for evaluation of formability of sheet metals subjected to different loading. free bulge of aluminume tubes has been investigated numerically to obtain flc. to verify the numerical results one experimental setup has been manufactured which has the ability of controlling the internal pressure and axial feed. in this study, time and zone of bursting in tube hydroforming is predicted using seven ductile fracture criteria. for calibration of these criteria, the uniaxial tension is simulated in abaqus/explicit. different loading curves are applied on tube to obtain the different points of flc. predicted flcs by ductile fracture criteria have been compared with experimental results. the flc which is predicted by ayada' s criterion has best match to experimental one. results show that prediction of all criteria are the same in strain position which is similar to uniaxial tension. based on the results, criteria which apply the effect of average stress in prediction of dutile fracture are more appropriate for tube hydroforming process.