Finite strain simulation of thin-walled tube under torsion using endochronic theory of plasticity

Endochronic constitutive equations are extended to describe deformations in finite strain range, using the concepts of corotational stress rate and additive decomposition of deformation rate. The general form of spin tensors, defining objective stress rates recently introduced to literature (Xiao et al., Int. J. Solids Struct. 35 (1998) 4001), is implemented to endochronic constitutive equations, which includes newly discovered logarithmic rate as a special case. The constitutive relations are specialized for a thin-walled tube under torsion. A procedure for solving the resulting ordinary differential equations for cases of simple and pure torsion are developed. Simulations of the axial effects for various materials subjected to simple and pure torsional loading cases are discussed and compared to experimental data.