PSI - Issue 68

Erik Calvo-García et al. / Procedia Structural Integrity 68 (2025) 809–814 Erik Calvo-García et al. / Structural Integrity Procedia 00 (2025) 000–000

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This fact can be explained since the compressive residual stresses achieved by shot peening treatments only affect a shallow layer of the material, much lower than the overall specimen thickness of the specimens used in this study. A similar explanation can be given for the fracture toughness results. Since grain refinement can be beneficial for fracture toughness, shot peening treatments were expected to increase to some extent the resistance to crack propagation. Nevertheless, this effect was not observed to be significant in the present research work, probably due to the low depth of material affected by shot peening treatments.

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Fig. 4. Crack propagation results: (a) crack extension versus number of loading cycles and (b) crack growth rates versus stress intensity ranges.

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Fig. 5. Fracture toughness measurements: (a) J-R curve of the non-treated specimen and (b) J Ic values for different surface treatments.

In order to better analyse the effect of shot peening on the crack propagation behaviour of aluminium alloys, thinner specimens should be tested. The ASTM E647 standard allow to analyse the crack propagation behaviour of thin specimens as long as they remain predominantly elastic, and buckling is precluded. However, thinner specimens may not be suitable for fracture toughness testing according to ASTM E1820 constraints.