Influence of T-stress on fatigue crack propagation

Mechanical components of aircraft may suffer from shocks and scratches during their and assembly. Under service, these structures are subjected to fatigue loading. This might lead to the initiation of micro-cracks, which will propagate, and in the worst cases, the fracture of the component might occur. Quantifying the total fatigue lifetime requires a good knowledge of mechanisms and kinetics of propagation throughout the evolution of the crack. In the case of a crack, subjected to mode I, in the Fracture Mechanics framework, According to Irwin's plastic zone theory, the size of plastic zone at the crack tip will change with the presence of a not null T-stress. Especially a negative T-stress will increase this size. So, considering that crack propagation is governed by confined plasticity at the crack tip, as proposed by Laird and Pelloux, it may affect fatigue crack growth. In the case of mechanically short cracks, this effect will be enhanced. Therefore, loading a long crack w...