Crack Opening/Sliding Morphology and Stress Intensity Factor of Slant Fatigue Crack

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 under the stress ratio of R= –1 and 0, stress intensity factors (KI)est and (KII)est were evaluated from the measured crack opening and sliding displacements. As a result, the stress intensity factor (KII)est for the crack made under the stress ratio of R= –1 with the slant angle of 45 deg. was decreased owing to the crack surface contact, while (KI)est showed relatively large values in spite of compressive residual stress.