Fig. 8 Examples of the assessment of the present simulation for the number of existing cracks plotted against cracked area due to the application of CAL having different stress amplitudes utilizing specimens with different surface configurations.
In Fig. 8, Z is plotted against \(A_{C}\) for different applied stresses. With a decrease in the applied stress and for the same\(\text{\ A}_{C}\), there is an increase in Z and, hence, an increase in the number of advancing tips. The implication, here, is that for the same \(A_{C}\) the average length of the existing surface cracks,\(\text{\ l}_{\text{av}},\) decreases as the applied stress decreases. Figure 9 exhibits the variation of \(\text{\ l}_{\text{av}}\)with the cycle ratio for different applied stresses as given by the present simulation. Both \(\text{\ l}_{\text{av}}\) and\(\text{\ A}_{C}\) behave similarly. Figure 9 supports the experimentally observed \(\sum\frac{N}{N_{f}\ }\) in the case of TSL tests with L-H and H-L sequences.