The influence of in-plane constraints on fatigue crack growth rate

The geometry of the structural members can influence the growth rate of fatigue cracks. Influence can be taken into account by incorporating dimensions into the formulas. However, such an approach is ineffective as the dependence of the crack growth rate is hard to predict and the formulas depend on the shape of the element. For each shape, a new formula is required. However, it is possible to use another approach that can be called a local approach in which the stress field parameters can be used in the neighborhood of the tip of the crack. It can be considered as an extension of Paris' approach to the growth of fatigue cracks. In the paper, the T-stress (the second term of Williams' solution) depending on the geometry of the element is used to quantify the effect of geometry on the growth rate of the fatigue crack. A series of fatigue in three-point bending specimens with different initial crack lengths. As a result, the dependence of the crack growth rate on the T-stress value was obtained.