Viscoplastic collapse of titanium alloy tubes under cyclic bending

This paper presents the experimetal result on the viscoplastic response and collapse of the<br />titanium alloy tubes subjected to cyclic bending. Based on the capacity of the bending machine, three<br />different curvature-rates were used to highlight the viscoplastic behavior of the titanium alloy tubes. The<br />Curvature-controlled experiments were conducted by the curvature-ovalization measurement apparatus which<br />was designed by Pan et al. (1998). It can be observed from experimental data that the higher the applied<br />curvature-rate, the greater is the degree of hardening of titanium alloy tube. However, the higher the<br />applied curvature-rate, the greater is the degree of ovalization of tube cross-section. Furthermore, due to<br />the greater degree of the ovalization of tube cross-section for higher curvature-rates under cyclic bending,<br />the number of cycles to produce buckling is correspondingly reduced. Finally, the theoretical formulation,<br />proposed by Pan and Her (1998), was modified so that it can be used for simulating the relationship<br />between the controlled curvature and the number of cycles to produce buckling for titanium alloy tubes<br />under cyclic bending with different curvature-rates. The theoretical simulation was compared with the<br />experimental test data. Good agreement between the experimental and theoretical results has been achieved.