PSI - Issue 38

Adrian Loghin et al. / Procedia Structural Integrity 38 (2022) 331–341 A. Loghin et al. / Structural Integrity Procedia 00 (2021) 000–000

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Fig. 6: Verification plots for surrogate model components for (a) mode I SIF at maximum loading and (b) crack tip X location.

The solutions of the constructed surrogate model for crack propagation were verified against ten 3D FEA based crack propagation simulations described above. Figure 7 compares the surrogate model and FE results for di ff erent quantities: loading cycles, K Imax and non-planar crack path. The surrogate model solutions are plotted by solid lines and the FE solutions are given by solid symbols. These plots indicate that the surrogate model is adequately capturing the crack propagation behavior of the 3D FE model within the solution space and therefore reaching verification requirements. Note that only five of the ten verification data sets were included in these plots for clarity. The model performance on the remaining cases were similar. Note also that all of the observed variances of the solutions so far are solely due to the variance of the initial crack position Y 1 . No material variation is added at this point. It is observed that even though the estimated crack paths and the K I values had some reasonable variance, the remaining useful life assessment did not have a variation of practical significance. In the next step, the constructed surrogate model for crack propagation was verified with di ff erent material fatigue crack growth rate properties. FE based deterministic solutions were collected from five additional simulations, this time with varying C and n fatigue crack growth parameters in addition to the varying geometric parameter Y 1 . Figure 8 shows the comparison between the surrogate and FE model assessments. As before, the surrogate model solutions are given by solid lines and the FE solutions are plotted by solid symbols. It is observed that one of the solutions terminate at the crack length of about 15 mm. This was because the crack for this particular case merged into the hole, similar to one of the cases shown in Figure 7c. Figure 8 demonstrates that the surrogate model sensitivity to material variation is consistent with the deterministic FE model.