PSI - Issue 38

Paul Catalin Ilie et al. / Procedia Structural Integrity 38 (2022) 271–282 P.C. Ilie et al./ Structural Integrity Procedia 00 (2021) 000 – 000

277

7

Fig. 4. Geometry of the model with three crack configurations used in the analytical model implemented in MATLAB.

Table 2. Plate specimen FEA model parameters

Parameter

Value

Uniform Tensile Load

200 MPa

Material Model

Isotropic Linear Elastic

Mesh Element Type Crack Propagation

Solid 186, Solid 187, Solid 185 Planar growth Mode I based

Similar to the analytical-based modeling cases, the 3D FEA based semi-elliptical surface crack configuration was tested considering seven different stress ranges from 50 to 200MPa and an initial crack geometry of 2 mm (along minor ellipse axis) and 3 mm (half of crack length along major axis). For all three geometries, a comparison between the 3D FEA based explicit crack propagation simulation and the analytical model implemented in MATLAB is provided in Figs. 5-7. The analytical model for the semi-elliptical surface crack is in good agreement with the 3D FEA based results for all seven different stress levels in Fig. 5. The embedded elliptical and corner quarter-elliptical cases analysed with the FE method produced very similar results to the analytical model. Measurements of crack length plotted as a function of cycles are shown in Fig. 6. The FE model results (for all stress levels) showed good correlation to the analytical solutions and it can be concluded that verification requirements are satisfied. Crack growth patterns and fatigue lives are similar for all three models as presented in Figs. 5, 6 and 7. The slight discrepancies between crack front shape, numbers of cycles and crack length predictions can be attributed to the crack front shape constraint in the analytical formulation. The analytical method enforced elliptical crack front increments based on two crack front points whereas the 3D FE based technique does not used any crack front shape constraint.

Fig. 5. Semi-elliptical surface crack results. Comparison between the two modeling approaches.