The path of a growing crack - A simulation of the fracture process

The growth of a crack subjected to corrosion fatigue is studied using adaptive finite elements. The crack is the image of a deep corrosion pit, and the growth is the result of a repeated cycle of dissolution of the material, formation of a protective oxide film and break-down of the oxide film. The break-down of the film is governed by the strain at the surface and the dissolution rate is assumed to be proportional to this stretching. A threshold strain is assumed to exist below which the oxide film remains intact. With this model, no criterion is needed, neither for crack growth, nor for prediction of the growth direction. The reason is that both are immediate results of the evolution of the body shape. The growth of a semi-infinite crack lying in an infinite strip subjected to different degrees of mixed-mode loading is studied and the results are compared to crack path criteria for sharp cracks. Additionally, the path of a corrosion fatigue crack starting at the surface of an elastic layer attached to a stiff substrate is simulated. The result showed some agreement with experimental results found in the literature