Double Curvature Springback in Stretch Formed 2024-T3 Aluminium

A test rig was developed to investigate springback in stretch draw forming processes, which are considered to be nominally uniaxial. An interchangeable tool allows the examination of both single and double curvature surfaces. Two double curvature tools with the following radii were used in the experiments, (A) 200mm by 450mm and (B) 450mm by 200mm. The first radius in each case corresponds to the direction of stretch. Obviously the smaller radius results in a larger moment, which creates a negative springback in the orthogonal direction. This effect is more pronounced in tool (A) due to the higher tensile strain levels in the direction of stretch directly affecting the strains in the orthogonal direction. By considering the resultant moment in each axis of the sheet independently, an analytical method was devised to give an approximation of the springback profile. Overall the analytical data, correlates well with both experimental and Finite Element (FE) results.