Through-the-thickness fatigue crack closure behavior in an aluminum alloy

The variation in fatigue crack closure behavior across the thickness of aluminum alloy specimens was investigated. The specimen geometries examined were the middle crack tension M(T) and compact tension C(T). The fatigue crack closure behavior was determined using remote displacement and strain gages, near tip strain gages, and fatigue striations. A hybrid experimental/numerical method was also used to infer the crack opening loads. The results indicate a variation in crack opening load, of 0.2 in the specimen interior to 0.4 to 0.5 at the surface.