Data Treatment and Generation of Fatigue Load Spectrum
Novel convergence-divergence counting procedure is presented to extract all load cycles from a load history of divergence-convergence waves. The lowest number of load history sampling is established based on the damage-based prediction criterion. A parameter estimation formula is proposed for hypothesis testing of the load distribution. An original load history generation approach is established 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.
KeywordsLoad Cycle Stress Cycle Load History Load Spectrum Total Test Time
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