A PROBABILISTIC APPROACH TO CUMULATIVE FATIGUE DAMAGE IN REDUNDANT STRUCTURES.
COLUMBIA UNIV NEW YORK INST FOR THE STUDY OF FATIGUE AND RELIABILITY
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Currently accepted methods of life estimation of multiple load path structures do not take into account some of the most significant physical and statistical variables of structure, material, and load. The Miner linear damage accumulation rule assumes damage progressing at a constant rate until the complete cross section of the structure has failed whereas it is well known that only a small part of the cross section becomes fatigued, while a much larger portion of it is fractured by the single application of a load too high to be carried by the remaining area. In the present approach, therefore, linear damage accumulation will be assumed until the reduced cross section becomes too small to carry the load while failure will in all cases be of the ultimate load type. In the analysis, the statistical distribution of the initial strength of elements will be utilized to determine the life of the weakest member as well as the successive failure times of consecutively failing elements. A model structure consisting of parallel geometrically identical load carrying members subjected to constant as well as variable amplitude fatigue loads will be considered. Author