Stress and strain gradients in high-pressure tube twisting

The strain gradient within the wall of a tube deformed to very large strains by a recently proposed high-pressure tube twisting technique was examined experimentally and by modeling in IF steel. The obtained strain gradient is negative; the shear decreases with the radius within the tube wall. It is shown that only the applied torque contributes to the plastic yield criterion; the axial compression creates only a hydrostatic stress state.