A Quantitative Laser Ultrasound Visualization System for Investigating the Interaction of Wedge Waves with a Defect

Machine tool blades exhibit typical wedge-shaped tips where defects are very likely to exist and call for non-destructive characterization. In order to detect the defect on the wedge tip, the interaction of wedge wave with defect characteristic needs to be investigated. Antisymmetric flexural (ASF) modes are wedge waves (WW) with their particle motion antisymmetric about the mid-plane bisecting and energy tightly confined near the wedge tip. A quantitative laser ultrasound visualization (QLUV) system which employs a pulsed laser to scan over the interested area then detected with a piezoelectric transducer. With the aid of reciprocal theorem, dynamic behaviors of ASF modes encountering a defect can be reconstructed. In this research, the QLUV system is used to evaluate the characteristic of WWs and the phenomenon of defect effect including mode conversion and the scattering intensity. With the QLUVS behaviors of ASF modes interacting with a wedge-tip-crack are characterized in a quantitative way. More complex behaviors for higher-order ASF interacting with cracks are under investigation.