An investigation on wedge waves and the interaction with a defect using a quantitative laser ultrasound visualization system

Wedge waves (WW) are guided acoustic waves propagating along wedge tips with their energy tightly confined near the wedge tip. Antisymmetric flexural (ASF) modes are WWs with their particle motion antisymmetric about the mid-plane bi-sectioning the apex angle. Machine tool blades exhibit typical wedge-shaped tips where defects are very likely to exist and call for nondestructive characterization. Due to the exhibited wedge shape, ASF modes are good candidate for probing the defects along the wedge tip. A quantitative laser ultrasound visualization system (QLUVS) is employed to investigate the interaction behaviors of ASF mode propagating along a damaged wedge tip. The QLUVS uses a pulsed laser generate acoustic waves which are then detected with a piezoelectric transducer. By scanning the generating laser together with the aid of reciprocal theorem, dynamic behaviors of ASF modes encountering the defect can be reconstructed.