PSI - Issue 39

Aljaž Litrop et al. / Procedia Structural Integrity 39 (2022) 41–46 Author name / Structural Integrity Procedia 00 ( 2019) 000–000

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Fig. 2. A series of DIC images showing shear strain dependent on the number of cycles N

Fig. 3. Crack length a dependent on the number of cycles N

The special shape of notch geometry gives rise to stress near the narrow section. As no shear stress can be at equilibrium on the free surface, cracking starts due to high tensile stress on the edge that acts in the tangential direction on the notch surface. As the crack progresses, it enters into the predominately homogeneous shear stress region, as shown in Figure 4 (right), which shows FEM calculated principal stress vectors. The red arrow in Figure 4 shows a path of a growing crack. Most of the crack growth occurs in the shear stress region.