The so-calle4 hydroforming Swift criterion is available to predict necking of tubes under inner pressure. But a special attention has to be paid to plastic-buckling, even though it is often disregarded for hydroforming. The axial load is generally added in order to force the material into the die, as well as to increase the thickness and delay necking. However, if this axial load is applied while necking is still a long way off, there is a risk of buckling. As shown in this paper, the critical strains corresponding to buckling arc much smaller that the critical strains predicted by the necking criterion. The two failure modes are to be taken together, and a numerical simulation is a good tool to perform this. With the complete simulation of the process, it is possible to plot hydroforming limit curves taking into accounts bursting as well as buckling. An advantage of this method is that it also enables us to differentiate between buckling and necking instabilities. An experimental setup has been developed in order to verify these results. Most of the tests were performed twice. The experiments seem reproducible. The first obtained results (except the case 3) are in good agreement with the numerical simulation, as well as with the analytical analysis. We have good tools to perform now "hydroforming limit curves".
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