Experimental and Finite Element Analysis on Rounded Corners Square Shape Tube Hydroforming Process

Abstract

Tube hydroforming is a forming process where an inner pressure combined with axial feeding deforms the tube to the shape of a die cavity, i.e. the process state where the hardening of the material is unable to resist the increase in inner pressure and wall thickness reduction. In the current work the tube with circular cross section is deformed to square cross section using hydraulic pressure. The die of the square edges is designed and manufacturing to change the tube with circular cross section to square cross section. The die and tools were designed and manufactured in order to satisfy the experimental work.The hydraulic system manufactured is capable to give several values of internal pressure. Initially circular tubes are inflated against a square die while simultaneously they are axially compressed in order to delay wall thinning and burst and achieve an accept tube wall thickness distribution. The dimension of tube used in the experimental work of copper is (L=110 mm, do=9.4 mm , to=1.5mm) to obtain forming limit diagram and mechanical properties of tube and value of the bursting pressure and final thickness for copper tube (170MPa ) and 1.18 mm. A squared grid has been printed by screen method with dimensions (5x5mm) the strain measurement accomplished by measuring the dimensions of the grid printed before and after deformation. The finite element method was applied via ANSYS11software package in order to determine the tube thickness, stress and strain behavior and the internal pressure required to form the square shape tube and the radius of curvature of the tube.It was found that the generated strain during the tube hydroforming process in the square cross – sectional die was less than that in ANSYS software within 20%. The results showed good agreement.