ENDOCHRONIC ANALYSIS FOR VISCOPLASTIC COLLAPSE OF A THIN-WALLED TUBE UNDER COMBINED BENDING AND EXTERNAL-PRESSURE

In this study, we employ the ordinary differential constitutive equati ons of endochronic theory to investigate the collapse of a thin-walled tube subjected to bending. A virtual work approach is used to formula te the problem, which results in a set of nonlinear algebraic equation s that are numerically solved. Experimental data on a 6061-T6 aluminum alloy under cyclic bending and 304 stainless steel under combined ben ding and external pressure found in previous literature are compared w ith the theoretical simulation. The experimental and theoretical resul ts are in good agreement. Finally, by using the rate-sensitivity funct ion of the intrinsic time measure in the theory, the theoretical analy sis is extended to investigate the viscoplastic collapse of a thin-wal led tube subjected to bending. Owing to the hardening of the metal tub e for a faster curvature rate, the magnitude of the limit moment, the ovalization of the tube cross section and the value of curvature at co llapse are theoretically demonstrated to have increased.