Effects of process parameters and material properties on deformation process in tube hydroforming

In this paper, factors affecting wall thickness distribution of the hydroformed tube are confirmed by FEM simulation and experimental work. The process model involves simple hydroforming of a square expanded product from a round tube using combined axial load and internal pressure. As factors, the stress ratio which is defined as nominal axial stress to nominal circumferential stress, coefficient of friction, n-value and anisotropic parameter r-value are considered. The results show that axial loading and better lubrication conditions improve the thickness distribution and r-value is one of the most important material parameters for tube hydroforming. It is found that fracture location of tube depends on process conditions and material properties and is not confined to a free bulged portion. Experimental results using an aluminum alloy tube (A6063) are in good agreement with FEM simulation results.