Investigation into Dual-Probe Laser Ultrasonic-Based Heavy-Duty Gas Turbine Blade Microcrack Detection

In environments with high temperatures and pressures, heavy-duty gas turbine blades run over extended periods of time. The long-term action of complex mechanical loads and thermal stresses, which can change material properties and cause fatigue fractures in components, directly affects the service life and safety of gas turbines. Turbine blade failure may result from these fissures. Laser ultrasonic has shown particularly encouraging results in high-temperature and in-service detection of fatigue microcracks in heavy-duty gas turbine blades. The ultrasonic signal utilized in laser ultrasonic testing links the material’s microstructure qualities with microcrack defects due to the uneven microstructure of turbine blades, which results in insufficient detection accuracy. This paper proposes a dual-probe laser ultrasonic testing method. Both the direct ultrasonic signals and the ultrasonic signals passing through the crack within the micro-area range are simultaneously detected by the two probes. The ratio of the two describes the characteristics of the ultrasonic signals. Numerical analysis was used for theoretical verification. A hardware and software framework was developed for the detection of dual-probe laser ultrasonic turbine blades. Simulated blade microcracks were studied experimentally. The findings demonstrate that the dual-probe strategy can greatly increase the detection accuracy and decrease the relative error of micro-crack detection on the turbine blade surface from 18.0 to 14.2% when compared to the traditional method. Give an example for applications in laser ultrasonic engineering.