Dynamic Identification of Microdamage Evolution Using Ultrasonic-Guided Wave Monitoring Method

Large-scale damage often originates from minor deterioration, making the dynamic identification of the microdamage evolution trend critical. In this article, a composite feature extraction method (CFEM) of ultrasonic-guided wave (GUW) monitoring is proposed. First, the window transient energy (WTE) is extracted through a sliding window, followed by the steady energy index (SEI) matrix calculation. Then, by analyzing the characteristics of microdamage evolution processes, two special criteria are advanced, leading to the definition of steady energy growth index (SEGI) and steady energy ratio index (SERI). Finally, the composite damage index (CDI) and the dynamic damage index (DDI) are computed to analyze these microdamage evolution trends. A simulation model was established to analyze the physical basis of the method. This article primarily focuses on fatigue cracks, a typical example of microdamage, and conducts fatigue loading tests on switch rails, as these have a significant impact. A total of 253 000 fatigue loading cycles (LCs) were executed from the onset of the experiment until the fracture of the switch rail. It was determined that CFEM was able to identify microdamage earlier and more stably compared to the other two methods in relate works. The application of CFEM is not restricted to rails, and it also proves beneficial for other components, such as pipes, plates, and rods.