Crack front rotation and segmentation in mixed mode I + III or I + II + III. Part II: Comparison with experiments

Using the results presented in Part I, together with various criteria, we try to explain qualitatively and quantitatively crack front rotation and segmentation under mixed mode I + III or I + II + III conditions. We first give a qualitative explanation of segmentation in mode I + III, based on the energetic theory of fracture. However, a satisfactory quantitative interpretation would require knowledge of a parameter which theory is unable to predict and which is not provided in experimental reports. We then concentrate on crack front rotation. It is shown that a suitable energetic criterion is able to reproduce quantitatively crack front "rotation rates" observed in brittle fracture in mode I + III. In fatigue, a criterion considering the sole mode I stress intensity factor is found to be more appropriate. Finally, for fatigue in general mode I + II + III conditions, we show that the crack front rotation rate is again satisfactorily reproduced by the same criterion as before, and also that a suitable extension of the well-known principle of local symmetry allows satisfactory prediction of the mean kink angle.