Fatigue design criteria for tanks for dangerous goods
Existing design rules for tank vehicles do not contain criteria for fatigue risk. A simple method for fatigue damage calculation has been developed based on the distinct acceleration of events during a vibration time history. It involves a calculated or empirical relationship between acceleration and stress, and standardized methods for fatigue design at variable amplitude. This paper reports the results of fatigue tests and detailed finite element analyses, and these analyses do not contradict the assumption that the stresses (or strains) are proportional to the acceleration. In the fatigue tests the load level needed to induce failure corresponds to strains about ten times higher than those measured in service. Failure occurred both in the weldments and in the base metal, with no significant difference in lifetimes between constant and variable amplitude. Scatter in the fatigue test data probably corresponds to the variation in weldment quality. The fatigue tests show no corrosion influence and no significant influence of irregular acceleration responses. The results suggest no modification of the proposed model.