Notched Member Fatigue Life Predictions Combining Crack Initiation and Propagation

Fatigue lives of notched members are considered to be divided into crack initiation and propagation phases. Apparent size effects caused by crack propagation through the strain gradient of the notch are accounted for if initiation is defined as a crack size within the local notch field. The extent of this field may be estimated from fracture mechanics analysis, with its size being of the order of one tenth of the notch radius. Plasticity effects must be properly handled in predicting crack initiation, but linear elastic analysis is generally satisfactory for handling the propagation phase.