T-Stress on a cruciform specimen: A preliminary study for a new crack propagation model

Mixed mode fatigue crack growth (FCG) can occur due to complex loading or specimen geometry. Fatigue crack paths can be determined using propagation criteria like the Maximum Tangential Stress (MTS) criterion, or the Maximum Shear Stress (MSS) criterion, for mode I and II dominated propagation respectively. These criteria only consider mode I and II Stress Intensity Factors (SIF), neglecting the T-Stress effects. In order to develop a new fatigue crack propagation model, that takes this fracture mechanics parameter into account, T-Stress values on a cruciform specimen were calculated for different loading conditions. Using a previously developed Finite Element Analysis (FEA) automatic propagation algorithm, cracks with two different initial orientations, were allowed to grow under different biaxial loading ratios and phases. Also, two holes were simulated on the specimen, in order to assess their influence on FCG. The resulting T-Stress values were determined as a function of the loading conditions and compared with the crack paths. It was possible to correlate the T-stress values with crack propagation direction stability and loading parameters, enabling the future development of a new crack propagation model, considering the influence of this fracture mechanics parameter. (C) 2020 The Authors. Published by Elsevier B.V.