Diagnostic System of Fatigue Damage under Random Loading with Statistical F test

摘要

In general, fatigue damage is calculated from S-N curve for materials or structures. However this method contains unreliability for stresses and cycles which are measured or estimated. Even if on-line monitoring system is used to obtain stresses and cycles under operation, S-N curve itself contains much scatter. In addition, on-line monitoring is usually monitored each sensor independently, which is easily affected by the change of circumstances. Therefore the estimated residual life still contains unreliability. Whilst, this novel statistical diagnostic method described in this paper is a low cost simple system. The method employs system identification using a response surface with several measured points and damage is automatically diagnosed by testing the change of the identified system by statistical F test. Therefore S-N curve is not needed to estimate the damage. In this paper, an experiment was carried out to confirm whether this novel method is effective to estimate the fatigue damage of a welded structure under random loading condition. It was found that the method is useful to estimate the fatigue damage effectively even under random loading condition.