Laser ultrasonic imaging of crack defects based on cross-correlation analysis

Focused on the crack defects commonly encountered during the manufacturing process of laser additive manufacturing (LAM), this paper introduces a laser ultrasonic imaging technique specifically tailored for these defects. This method relies on cross-correlation analysis for precise detection. Utilizing the selective laser melting (SLM) technology as a case study for printing AlSi10Mg alloy, the surface of the specimen was meticulously scanned using laser ultrasound, allowing us to capture the ultrasonic surface wave signal. Subsequently, the crack defect imaging is achieved through a cross-correlation analysis of adjacent surface waveforms. To address the challenges posed by background noise and sample surface roughness, an adaptive threshold method is introduced. This innovative approach effectively reduces noise in the defect imaging results, thereby significantly enhancing the imaging accuracy of crack defects. The findings reveal that the cross-correlation and adaptive threshold-based defect imaging method not only sharpens the boundary features of defects but also significantly diminishes the shadow area during crack defect detection. This offers a more efficient and convenient approach for defect detection and recognition, paving the way for improved quality control in LAM processes.