APPLICATION OF TWIN SHEAR STRESS YIELD CRITERION IN AXISYMMETRIC INDENTATION OF A SEMI-INFINITE MEDIUM

摘要

The deforming zone of axisymmetric indentation of a semi-infinite medium was divided into two parts: a solid plate and an annulus. Their kinematically admissible velocity fields with two undetermined parameters, α = R_0/h and β= R_f/R_0, were established respectively. Then, with the Twin Shear Stress Yield Criterion and Upper-bound Theorem, the total power of deformation was obtained and minimized. The minimal stress state factor was n_σ = p/2k = 2.71, and corresponding parameters were α = 1.20 and β = 1.64.