Deviation based fault detection method for shackles under variable loading

Shackles used in lifting work are mainly subjected to fatigue loading during operation. The failure of the shackles can lead to catastrophic accidents and economic loss because they serve as a connection between loads and lifting equipment. Thus, it is necessary to detect the faults of shackles in advance. In this study, weak points of a shackle were identified through the calculated stress distribution and were verified through fatigue tests. The representative features were extracted based on RMS and peak-to-peak values of dual strain data. Thresholds for fault detection were defined using the features and the weight functions considering the inverse proportion between strain values and lifetime of shackles. The performance of detectors was evaluated by comparing with cycles between the detected fault and the incipient crack. The selected detector without using complex formulas can carry out the fault detection of shackles effectively.