Effect of Initial Crack Size on Probability of Fracture Failure

Fatigue is one of the failure mechanisms of ship,offshore and bridge crane steel structures.The factors influencing the fatigue crack growth are of random nature.The Paris' law is used for the description of crack propagation.It is assumed that the fatigue crack initially has a semi-elliptical shape,and that the shape remains semi-elliptical as the crack propagates.The failure criterion is taken as exceedance of a critical crack size in a time period with N stress cycles.To simplify the problem the thickness of plate is chosen as the critical size.Then using the Paris' law in conjunction with an advanced Level II method,the reliability of fracture failure is examined.