Application of chaotic information entropy for ultrasonic guided wave detection in pipe

In this paper, a quantitative detection method of the weak ultrasonic guided wave (UGW) signal based on information entropy of the Duffing chaotic system is proposed. It can simultaneously identify the location and size of small defects in pipelines. First, by adjusting the driving force amplitude of the Duffing system, the system is in a critical state from period to chaos. When the weak UGW is added on the driving force, the state of the Duffing system will change. It can be used to detect weak signal. To realize the quantitative detection of UGW, a method based on information entropy is presented in this paper. By analyzing the influence of UGW on the driving force amplitude of the Duffing equation, a sensitive damage index is constructed to indicate the signal strength. Furthermore, a time-moving window function is introduced. By scanning the recording signal, the defect location can be identified using the damage index. The experimental studies show that the proposed method is validity for detecting small defects in pipeline, and simultaneously identify the size and location of the defects. This method has a strong noise immunity and significantly improves the sensitivity of small defects detection in pipelines.