Evaluation of Stress Distribution along the Crack and Stress Intensity Factor under Mixed-Mode Conditions

Abstract

For an actual crack growth in structures subjected to the applied stress from the various directions, it is important to study about the fatigue crack propagation behavior under mixed-mode condition. In particular under the condition, crack surfaces tend to contact when the load is applied because of the compressive residual stress distributed near the crack and the zigzag crack surface morphology. In this study, using slant cracks with compressive residual stress induced in mode I fatigue crack propagation, discontinuous displacements (Mode I : crack opening displacement, Mode II : crack sliding displacement) were measured along the slant crack. The stress distributions along the crack were calculated from the discontinuous displacements and the stress intensity factors (K_I)_est and (K_II)_est were estimated from the calculated stress distributions. As a result, the residual stress distribution along the crack was evaluated from the calculated stress distribution. Using the estimated stress intensity factors, (K_I)_est and (K_II)_est, an interaction between the compressive residual stress and the crack surface contact behavior was discussed.