Evaluation of fatigue procedures for welds and rotating axes

The first part of this thesis evaluates the fatigue life prediction procedure in British standard 2571-2 appendix C against experimental high cycle fatigue data found in the literature. The safety margin to the actual endurance limit and the failure probability was calculated. The steel specimens used to generate the reported fatigue data had different geometries and material properties. The applied stress states were rotating bending, reversed torsion and a multiaxial stress state. The predicted failure probability was greater than proposed in the standard. The total failure probability for the collected data was 32%, not 10% as claimed in the standard. The second part deals with the determination of structural Hot spot stress in welded structures. The accuracy of two different methods was investigated using finite element analysis. The results obtained with a recently developed method, the Dong method and the Hot spot stress method suggested by the International Institute of Welding were compared. The selected comparison case was a round robin investigation found in the literature. The Hot spot method gave consistent results for different mesh densities and types of finite elements. The same robustness was not observed for the Dong method.Validerat; 20101217 (root