Estimation of the η Factors for Mixed-Mode Cracks in Compact Tension Specimens

Abstract

The η factors for mixed-mode cracks in compact tension specimens are investigated for estimation of the J -resistance curve under mixed-mode loading conditions. The derivation of the η factor is first generalized for mixed-mode cracks. Based on a lower-bound approach for rigid-perfectly plastic materials, the η factors are then derived under mixed-mode I and III and mixed-mode I and II loading conditions. The results indicate that the η factor is only a function of the normalized crack length under mixed-mode I and III loading conditions. However, under mixed-mode I and II loading conditions, the η factor is not only a function of the normalized crack length, but also influenced by the fixture design due to the moment induced by the mode II load.