A simplified approach to crack growth prediction in a cranckshaft

Fracture mechanics analyses are carried out on a cracked machine element of complex geometry to predict its fatigue behaviour. Usually, in order to obtain reliable values of stress intensity factors, it is necessary to realize three-dimensional meshes or to utilize the energy approach. An alternative, simplified and approximate approach is proposed here. It is based on the construction of simple two-dimensional models to obtain accurate values of the geometry factors of the component at the deepest point of the crack. Experimental tests show that the relation between the depth and the length of the crack on the free surface is linear. Hence it is possible to reduce the problem to two dimensions with a consequent saving of calculation time. A comparison with experimental data indicates that a satisfactory prediction is obtained by the proposed method.