Influence of the Interaction on Stress Intensity Factor of Semielliptical Surface Cracks

The interaction between multiple surface cracks is an important consideration in the cracking behavior due to thermal fatigue and stress corrosion cracking. However, it is difficult to evaluate the intensity of the interaction quantitatively because there are many factors, such as the relative position, size, and geometry of the cracks. Furthermore, the influence of the interaction differs with the crack tip position along the front. In this study, to investigate the intensity of interaction, the stress intensity factor (SIF) of interacting semielliptical surface cracks was evaluated by the finite element method and finite element alternating method. These methods enable us to evaluate the SIF of interacting cracks for various conditions. The analysis results reveal that the change in the averaged SIF along the crack front caused by coalescence of two cracks can be estimated from the change in the area size. The maximum interaction can be estimated by a simple addition of the area size of two cracks regardless of the loading condition and relative crack size. To exclude the conservativeness caused by the current combination rule, new criteria are shown.