APPLICATION OF LASER-BASED ULTRASOUND TO THE INSPECTION OF CONTOURED PARTS

To realize the full high speed scanning potential of a same side laser-idlaser-out inspection system it is necessary to angularly deflect the generation and detection laser beams across the part surface. We have investigated the variations in the detected ultrasonic signal amplitude in reinforced polymer composite (RPC) materials resulting from varying the angle of incidence of the laser beams from 0 to 45". These studies have been made on a variety of RPC materials having various surface textures and coatings. The results show that several commonly used paints significantly enhance the diffuse component of the reflected light thus increasing the signal amplitude obtained for large angles of incidence. Even for uncoated specimens the decrease in signal amplitude at large angles is within the dynamic range of a suitably designed laserbased ultrasound system.