Detecting asymmetry in rotating structures a combined actuation and signal processing approach

摘要

Rotating machines often produce synchronous vibrations at the frequency of rotation and its multiples. It is shown that asymmetric bodies cannot be easily distinguished from perfectly symmetric ones by analyzing the response signals. This fundamental fact explains why severe defects, such as cracks and mechanical damage can sometimes be undetected without complete dismantling of the machine. In this paper, an active non-synchronous external excitation is applied to the system in a manner that causes a parametric excitation. The measured response in this case will exhibit a response at a unique frequency with amplitude directly proportional to the level of asymmetry. A complete theoretical, numerical and experimental study demonstrated the utility and advantage of the proposed approach.