Abstract:

In this article, an alternative equivalent explanation for rain-flow counting in fatigue analysis is introduced, based on which a recursive rain-flow counting algorithm is proposed. The algorithm separates any load time history with more than one peak into three sub-segments by two valleys; and every sub-segment with more than one peak is again separated into three shorter sub-segments recursively, till every sub-segment contains only one single or no peak. A sub-segment that contains a single peak corresponds to a load cycle whose minimum and maximum values are calculated simultaneously by the recursive procedure. The algorithm need not rearrange load time history after eliminating the peak and valley values of extracted local cycles as is the case with some other rain-flow counting algorithms. It keeps the load cycle sequence information, and the first cycle extracted by the algorithm may be the one with the maximum range. The disadvantages of the algorithm are that it is not suitable for real time application and that it requires the computer to assign a large amount of memory to stack in its implementation.

Key words: fatigue, recursive algorithms, rain-flow method, load histories, cycle counting