Assessing the life of mechanical systems under time-variable load

The application is described of Wald's sequential analysis on fatigue failure for assessing the life of mechanical systems strained by a time-dependent load. Measurements of fatigue crack propagation in regular time intervals allows to make a decision whether fatigue failure has or has not reached the limit value of the crack size in the given number of cycles. The applicability of this method is discussed and cases are described of crack arrest. The possibility is discussed of converting the results of structure tests at trial temperature to their life at operating temperature. In two cases the calculation is made of input data and the procedure for testing the fatigue failure of a slab strained by cyclically altered bending. The possibilities are discussed of the practical application of the method of evaluating fatigue failure in the assessment of the life of structures or their critical points. The purpose of the study is to provide documentation for trials of prototypes of components of primary circuit pipes and fittings of WWER reactors in a scale of 1:1, strained with cyclically changing parameters