Application of stress intensity factor superposition in residual stress fields considering crack closure

On the prediction of fatigue crack growth based on weight functions in residual stress fields induced by laser shock peening and laser heating

“…As the consequence, due to the irregularities in FCG behavior, that is, a complex and deflected crack path as well as crack branching as it was observed for specimens 1-C-25 and 1-Cs-25-55, the approach for computing the stress intensity factor would need to consider the changed crack geometry and contact in crack closure. 27 The obtained residual stress field, depicted in Figure 5C,D, shows similarities with the residual stress field of an Eshelby inclusion. 56 However, it is important to note that the process of circular LH is not symmetric and a spiral shaped stress field is indicated, see, for example, Figure 5D.…”

“…26 Furthermore, Keller and Klusemann showed that the consideration of a changed crack geometry allows the application of the superposition principle. 27 Redistribution of residual stresses during FCG can be influenced by the presence of crack closure. This effect and the possible changed crack geometry are not considered by applying weight functions in the described methodology.…”

“…The quite good agreement between the experimentally obtained and predicted results in the current study suggest to conclude that the crack is opened completely at the maximum values of the applied load, allowing the calculation of the stress intensity factor from applied load (Equation 10) and the stress intensity factor due to the presence of residual stresses (Equations 1 and 3) as well as the superposition of the stress intensity factors, see also the study of Keller and Klusemann. 27 Furthermore, the assumption of K tot,min = 0 MPa  √m for the case of crack closure is reasonable, as the crack front is assumed to be completely closed at the minimum values of the applied load. The assumption is supported by the presence of compressive residual stresses through the specimen thickness (Figure 4), as reported in the study of Kashaev et al 11 Therefore, for that kind of LSP treatment, the methodology used in this study is suitable for quite accurate prediction of FCG.…”

“…26 Moreover, the applicability of the stress intensity factor superposition considering crack closure in compressive residual stress field was investigated on a numerical way by Keller and Klusemann. 27 It was found, that crack closure can be interpreted as a change of the crack geometry, where the partition of the total stress intensity factor changes as well. The discrepancy in the determination of the K tot by the superposition principle without the consideration of crack closure can therefore result in an error in FCG rate calculated by an empirical FCG law based on K tot .…”

Effect of Residual Stresses on Fatigue Crack Growth: A Numerical Study Based on Cumulative Plastic Strain at the Crack Tip

“…Note that these thermal residual stresses are elastic and that the maximum compressive stress (200 MPa) is 69% of material’s yield stress (288.96 MPa). Keller et al [ 44 ] considered residual stresses, representing 0.85 of yield stress in 2024 aluminum alloy. Hu et al [ 45 ] also used a temperature increase to generate residual stresses.…”