3.2.1. Case I

The simulated crack growth for this specimen moved between the bottom and midhole and reached the mid-hole on the right side. It presented a significant increase in the KII component of the shear stress intensity factor across the cracks, which forced the stepsizes of the crack to be shortened. The findings of the crack trajectory during propagation were excellently consistent with the experimental results of the crack trajectory [32], the numerical results obtained by [33] using A polygonal extended finite element method (XFEM) with numerical integration for linear elastic fracture mechanics, the XFEM results using ABAQUS software obtained by obtained by [34], and with the numerical results using the coupled extended meshfree–smoothed meshfree method presented by [35], as shown in Figure 9a–e, respectively. The maximum principal stress distribution is shown in Figure 10.

**Figure 9.** Final crack growth path for case I: (**a**) present study, (**b**) experimental results [32], (**c**) [33] with permission of Elsevier 2019, (**d**) [34] with permission of Elsevier 2018, and (**e**) [35] with permission of Elsevier 2020.

**Figure 10.** Maximum principal stress distribution of case I for the PMMA specimen.

The results of this simulation were compared with those from XFEM using the smooth nodal stress technique by Peng et al. 2017, as shown in Figure 11, with good agreement. It was found that as the crack approached the hole, the SIFs appeared to change to a greater amplitude. The predicted fatigue life for this specimen was compared to the analytical results calculated by [36] using Paris and Walker models, as shown in Figure 12, with good agreement.
