Shear lips on fatigue fracture surfaces of aluminum alloys

ABSTRACT A fatigue crack normally grows in so‐called mode I, with a flat fracture surface perpendicular to the loading direction. Sometimes the crack front becomes slanted, at about 45° with the loading direction. In that case it is possible that the original crack growth direction is maintained, but also a deviated growth direction can be found. The paper describes various effects related to the occurrence of slant growth due to shear lips on fatigue fracture surfaces in (thin) sheets. After a general introduction the attention is focused on the relations between shear lips and fatigue crack growth. Questions about why shear lips develop and about other aspects of shear lip behaviour will be answered.