Research on signal enhancement technology of ultrasonic guided wave detection of rail crack based on spread spectrum technology

Abstract During the propagation of guided waves in rail tracks, there are issues such as poor anti-interference ability and severe signal attenuation. This article proposes a signal enhancement technique for the processing of guided wave signals, aiming to improve the signal-to-noise ratio by enhancing the detection signals. Building upon traditional ultrasonic guided wave detection, this technique utilizes Barker codes as pseudo-random sequence codes and employs Binary Phase Shift Keying (BPSK) modulation to encode the original excitation signal, resulting in a new excitation signal. This achieves spread spectrum processing of the excitation signal and subsequent despreading of the received signals. An experimental platform for detecting subsoil cracks in rail tracks using ultrasonic guided waves was established. Comparative experiments were conducted on artificial cracks of different sizes at the bottom of rail tracks under both spread and non-spread conditions, calculating the attenuation coefficient of received guided wave signals. The results demonstrate that after applying this signal enhancement technique to guided wave signals, compared to unprocessed original guided wave signals, there is a significant reduction in attenuation coefficient when propagating over the same distance. As a result, ultrasonic guided wave signals can propagate over longer distances with increased sensitivity towards cracks of similar sizes at the bottom of rail tracks. These findings provide support for ultrasonic guided wave detection of subsoil cracks in rail tracks.