Viscoplastic collapse of titanium alloy tubes under cyclic bending

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