On suppression of plastic buckling in hydroforming processes

Critical lateral fluid pressure for suppression of plastic buckling of annular plates during deep drawing by hydroforming process is examined. The theoretical prediction, utilizing the energy method, is accompanied by experiments. The outcome enables to program a fluid pressure path (with respect to the punch travel) which may prevent, to some extent, premature buckling at the flange area of the product. The governing geometrical and material parameters (as plate thickness, drawing ratio, strain hardening exponent, buckling modulus, flange-cup transition curvature, etc.) are all viewed through their effects on the critical fluid pressure at buckling. Hydroforming experiments with blanks made of copper, aluminum, steel and stainless steel with various geometries validate the analysis and demonstrate the technological usefulness of the results.