This paper reports in detail a fundamental concept of a P/V difference method which is one of rainflow algorithms. The method is one of cycle count procedures which are useful for analyzing a complex strain time history.
A strain time history should be analyzed keeping in mind the stress-strain behaviour in the background. Based on this concept, the rainflow algorithm subtracts from a strain time history the parts which correspond to closed hysteresis loops in the stress-strain relation. The subtracted parts and the residual parts are successively processed for fatigue damage evaluation.
The algorithm given in this paper is simpler than the ones already presented, by the use of successive absolute differences between neighbouring peaks and valleys called P/V differences.
The simplicity enabled us to make a real-time on-site fatigue damage indicator.
