Issue 33

F. Fremy et alii, Frattura ed Integrità Strutturale, 33 (2015) 397-403; DOI: 10.3221/IGF-ESIS.33.44 400  the contribution of mode III to mixed mode fatigue crack growth can be determined by comparing pairs of load cases, namely the two “proportional” load paths (Fig. 3C and Fig. 4B), the “square” and the “cube” load paths (Fig. 3A and Fig. 4A) and finally the “cross” and the “star” load paths (Fig. 3B and Fig. 4C). Figure 3 : Loading cases applied in mixed mode I+II conditions. A –« Square » load path, B – « Cross » load path C – « Proportional » load path, D – « Windmill » load path. Figure 4 : Loading cases applied in mixed mode I+II+III conditions. A – « Cube » load path, B – « Proportional » load path, C – « Star» load path. R ESULTS he results of the fatigue crack growth experiments conducted in mixed mode I+II conditions indicate that there is a significant load path effect in mixed mode fatigue crack growth (Fig 5a). First of all, the crack path is significantly different according to the load path selected. These observations show a significant tilt of the crack path (40°) for the “proportional” load path, after 1 mm of coplanar crack growth in mixed mode conditions. On the contrary, the tilt of the crack path is found to be moderate for the “square” load path (10°) and very small for the two other cases. T