Issue 35

C. Gandiolle et alii, Frattura ed Integrità Strutturale, 35 (2016) 232-241; DOI: 10.3221/IGF-ESIS.35.27 239 Fig. 9a plots potential evolution of the mixed load test and Fig. 9b plots the crack propagation calculated with the calibration curve. It shows that a crack is generated at the first block and propagates throughout the first and second bloc. The crack stops propagating when the loading changes for the third block. Bloc σ F,moy /σ y-flat σ F,alt /σ y,flat Q*/P N (cycles) 1 0.78 0.85 0.3 70000 2 0.78 1 0.3 670000 3 0.78 0.85 0.15 1000000 Table 2 : Fretting fatigue loadings and durations of the mixed load test blocks. Figure 8 : Sketch of loading blocks. (a) (b) Figure 9 : (a) Potential evolution during mixed load test, (b) Crack propagation rate established with the calibration curve. In order to explain this behavior, the mixed load test was simulated. Blocks were applied one after the other on the FE model as in the experimental test. Loading history, that is the residual stress from each loading block, is thus taken into account by the next block.