PSI - Issue 66

María Moreno-Rubio et al. / Procedia Structural Integrity 66 (2024) 362–369 Author name / Structural Integrity Procedia 00 (2025) 000 – 000

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other begins. The boundary between the two phases is determined during the process. This model has been successfully applied in previous studies, yielding highly satisfactory results, as demonstrated by Erena et al. (2022) and Vázquez et al. (2010), among others. The initiation phase analyzes the number of cycles required to generate a crack of length a i , producing an initiation life curve ( a i -N i ), while the propagation phase analyzes the number of cycles required to propagate a crack from the initial length until the failure of the component, resulting in a propagation life curve ( a i -N p ). Once the propagation curves ( a i -N p ) and initiation curves ( a i -N i ) are obtained, both curves are summed to produce the estimated total life curve as a function of the crack length taken as initiation, a i , where ( a i -N t ) = ( a i -N i ) + ( a i -N p ). Among all possible life values, the minimum value of the total life curve is considered the fatigue life, N t * , and the crack length corresponding to this minimum is taken as the initiation length, a i * , (see Fig. 3). Therefore, a i * is considered the point where the initiation phase ends and the propagation phase begins.

Fig. 3. Life prediction model

Fig. 4. Estimated life vs. experimental life

4. Results This section presents the life estimates at both room temperature (RT) and 650ºC (HT), as shown in Fig. 4, in comparison with the experimental fatigue life results. In both cases, the estimated life is plotted on the y-axis, and the experimental life on the x-axis. Therefore, if the estimated and experimental lives are identical, the values will