ANISOTROPIC SPRING-BACK IN VARIOUS ALUMINUM-LITHIUM SHEET ALLOYS

Background/aim: Bending of sheets is a typical forming process and dis tortion of final shapes can occur because of release of elastic stress es which is called spring-back. Spring-back complicates tool design be cause the die must be designed to compensate for it. The aim is to pro pose a model to quantatively predict the magnitude of anisotropic spri ng-back due to texture effects and to apply the model to recrystallise d and unrecrystallised Al-Li sheets. Methods: A rubber pad-forming tec hnique was employed for the bending. Average crystallographic texture was measured by neutron diffraction and the orientation-dependent func tion (ODF) was used to develop a theoretical expression for spring-bac k. Results and conclusions: The calculated spring-back curves were in fair agreement with measurements. The anisotropic spring-back depends on the testing direction due to texture. Gags texture had maximum effe ct on that. A slight stretch of the AI-LI sheets enhanced the spring-b ack due to strain hardening but not the degree of anisotropy. The spri ng-back increased as the die radius and material strength increased, a nd the material thickness decreased, but these factors did not influen ce the anisotropy of spring-back.