Inverse determination and probability distribution of the mode III strain energy density control radius with an optimized V-notched specimen under torsional fatigue loading

The Strain Energy Density (SED) is a fatigue criterion based on a control volume. This parameter is required for a precise assessment of the fatigue strength of any, especially severely, notched component. A newly developed inverse determination procedure is presented here to precisely determine the mode III (or torsional) control radius. The procedure is then extended to the evaluation of the probability scatter of this length which is properly represented by a skew normal distribution. Experimental results of aluminum alloy 7075-T6 and steel 42CrMo4 + QT are presented, and comparisons are provided between mode I and mode III control radii.