Metallic cylinders are widely used in various fields of industrial production, and the automatic detection of surface microcracks is of great significance to the subsequent grinding process. In this paper, laser-excited surface acoustic waves (SAW) are used to detect surface microcracks. Due to the dispersion of SAWs on the cylinder surface, the SAWs exhibit different polarities at different positions. In order to improve the consistency of signals and the accuracy of the modeling, the angle at which the polarity is completely reversed is selected as the detection point. A laser ultrasonic automatic detection system is established to obtain signals, and the B-scan image is drawn to determine the location of the microcrack. By comparing the time–frequency diagrams of the reflected SAWs and transmitted SAWs, the transmitted wave is chosen to establish the microcrack depth prediction model. In addition, according to the trajectory of the grinding wheel, a prediction model based on the absolute depth of the microcracks is established, and the influence of the orientation of the microcracks on the signal energy is considered. The method proposed in this paper can provide a reference for the rapid grinding of microcracks on the surface of metallic cylinders; it has the characteristics of visualization and high efficiency, and overcomes the shortcomings of the currently used eddy current testing that provides information on the depth of microcracks with difficulty.

Decoupling macroscopic phase transformations from microstructural evolution during TC4 heat treatment is challenging. This study proposes an in-situ monitoring system using laser ultrasonic. Longitudinal wave velocity tracks the β phase volume fraction, while a novel Energy-Weighted Instantaneous Frequency (EWIF) metric quantifies microstructural heterogeneity. Experiments identify a peak transformation temperature of 970°C. Crucially, EWIF exhibits a steep 27.6% decline during the transformation (950-970°C), coinciding with peak interfacial density and disorder—features undetectable by velocity alone. By constructing a CL - EWIF ultrasonic state trajectory, we establish a state-domain control standard independent of temperature and time, offering a robust method for industrial process monitoring.