In the fatigue analysis of most medium speed diesel engine parts, it is customary to assume a constant amplitude load and, in principle, calculate for an infinite lifetime. Diesel engine components often have a complex geometry, and a multiaxial stress state will arise at many places in these parts. Because of the size of these engine parts, component testing of the fatigue limit is not possible, and it is necessary to rely on specimen testing. The correct tram formation of the test data to the corresponding component data will therefore be of utmost importance, i.e. the correct interpretation and evaluation of the statistical size factor become especially important. ABAQUS is used in the stress analysis, and to speed zip the fatigue analysis, an in-house program has been developed for the automatic multiaxial fatigue analysis according to the Findley criterion. The statistical size factor is calculated according to the theory of the weakest link, using the tested standard deviation of the fatigue limit and the calculated effective stress area. The effective stress area is also calculated with the theory of the weakest link utilizing the calculated surface stress distribution. The ratio of this stress area to the effective stress area of the reference specimen used in the testing of the fatigue limit will be the number of links to be used in the calculation of the statistical size factor.
