Statistical distribution functions and fatigue of structures

Three statistical distribution functions are compared. The log(N) normal distribution, the 3-parameter Weibull distribution and the 3-parameter log(N−N0) normal distribution. The latter function is relatively new. Attention is paid to very low probabilities of failure. Various sources of scatter of fatigue test data and fatigue of structures in service are recapitulated. Different practical problems for which statistics are important are defined. Limitations of statistical predictions are briefly discussed. The significance of fatigue acceptance tests and realistic full scale service-simulation tests are emphasized.