Crack growth and closure behaviour of surface cracks under pure bending loading

Fatigue crack growth and closure behaviour of surface cracks as well as through-thickness cracks in aluminium alloy 7075-T651 are investigated under pure bending loading. We have placed a special focus on the comparison of the surface crack closure behaviour under two loading cases, axial and bending, and also with the through-thickness cracks. The ratio of crack opening in the crack length direction to that in the crack depth direction is close to 0.9 regardless of the applied loading types and the stress ratios. Growth rates of surface cracks can be successfully explained in terms of the effective stress intensity factor range, independently of the loading type, the crack shape and the stress ratio.