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Fatigue crack growth-based damage modeling approaches have received great interest due to its critical importance in the industry. However, a substantial deficiency of an explicit fatigue damage model to quantify the accurate fatigue crack growth behavior remains due to the complex fatigue crack growth behavior in different length scales. This complexity arises from the fact that fatigue crack growth (FCG) in different length scales depends on many damage controlling parameters. Machine learning-based fatigue damage modeling approaches have received noticeable attention for fatigue crack growth analysis due to their abilities to account for numerous damage parameters simultaneously. In the presented paper, a radial basis function artificial neural network (RBF-ANN) model has been developed to predict the FCG behavior, including the short and long crack regimes. The presented RBF-ANN model has been trained and verified by experimental data sets of Ti-6Al-4V titanium alloy, 2024-T3 and 7075-T6 aluminium alloys. The predictions showed that the RBF-ANN model has a good interpolation capability to predict the nonlinearity of both short and long crack growth behavior. However, the model shows poor extrapolation capability for accurate short crack growth predictions for cases that there are limited data sets in hand. The model effectiveness greatly depends on sufficient available input data.

Objective This study focussed on the mutual role of emotion covariation and psychological flexibility in understanding the reciprocal effects of chronic pain and psychological distress. Design A longitudinal design was applied with a sample of 177 adults (mean age = 58.3, 57.1% women) suffering from chronic back/neck pain. Main outcome measures Assessments were conducted at three timepoints: pain and psychological distress upon referral to a pain clinic (T1); emotion covariation (the correlation between daily reports of positive and negative emotions) and psychological flexibility (self-reported ability to withstand unpleasant experiences while acting upon personal values) during the weeks before undergoing an intrusive procedure (T2); pain and psychological distress one day prior to the procedure (T3). Results T2 psychological flexibility and emotion covariation mediated the effect of T1 pain on T3 psychological distress. However, T2 psychological flexibility and emotion covariation did not mediate the effect of T1 psychological distress on T3 pain. Conclusion The findings highlight two complimentary mechanisms - emotion covariation and psychological flexibility - that mediate the relationship between pain and psychological distress for people with chronic back/neck pain. The findings inform future research on the effects of intervening on these mechanisms, which may lead to clinical interventions aimed at improving coping with pain.