Inelastic Response and Stability of Titanium Alloy Tubes under Cyclic Bending

Abstract

The response and stability of titanium alloy tubes subjected to cyclic bending are presented in this paper. The curvature-ovalization measurement apparatus, designed by Pan et al., is used for conducting the present curvature-controlled experiments. It is observed from the moment-curvature curve that the titanium alloy tube is cyclically harden and becomes steady after a few cycles for symmetric curvature-controlled bending. However, from the ovalization-curvature curve, the ovalization of the tube cross-section increases in a ratchetting manner with the number of cycles. Owing to the progressive accumulation of the ovalization of the tube cross-section during the cyclic bending, the titanium alloy tubes buckle eventually. Theoretical formulation, proposed by Kyriakides and Shaw, is used for investigating the relationship between the magnitude of the controlled curvature range and the number of cycles to produce buckling. Good agreement between the experimental and theoretical results is achieved. Furthermore, experimental data of the titanium alloy tubes from present study are compared with the experimental results of 6061-T6 aluminum and 1018 steel tubes tested by Kyriakides and Shaw. It is shown that for similar outer diameter/wall thickness ratio, the stronger metal tube exhibits a shorter number of cycles to produce buckling.