A load history generation approach for full-scale accelerated fatigue tests

Abstract

This paper seeks to establish a load history generation approach for full-scale accelerated fatigue tests. Primary focus is placed on the load cycle identification such as to minimize experimental time while having no significant effects on the new generated load history. The load cycles extracted from an original load history are identified into three kinds of cycles namely main, secondary and carrier cycles. Then the principles are presented to generate the load spectrum for accelerated tests, or a large percentage of small amplitude carrier cycles are deleted, a certain number of secondary cycles are merged, and the main cycle and the sequence between main and secondary cycles are maintained. The core of the generation approach is that explicit criteria for load cycle identification are established and equivalent damage calculation formulae are presented. These quantify the damage for accelerated fatigue tests. Three validation examples of its application for the generation approach of accelerated load histories are given in the paper. Good agreement of experimental lives between the original and generated load histories is obtained. Finally, the generation approach of accelerated load histories is applied to the full-scale accelerated fatigue test of helicopter tail, demonstrating the practical and effective use of the proposed approach.