초음파 결함신호 영상화를 이용한 레이저 용접부 비파괴 평가

This paper aims to study that the defect exploration method to specimen's thickness, using an characteristic of an ultrasonic wave generating in ablation area and thermo elasticity area, has been applied to using a way of receiving it by Air-Coupled Transducer and transmitting it by an ultrasonic wave and a way of noncontact receiving and transmitting ultrasonic wave using a laser. The longitudinal, transverse waves have been used in 60㎜ thickness specimen and Lamb wave in 3㎜ to run artificial defect detection test. In this way, the usefulness of noncontact laser ultrasonic wave has been verified. To confirm the possibility of implementation on natural defect existing at real welding part, thickness in 3㎜ SM45C and STS304 artificial defect specimen has been made and defect detection test using Lamb wave has been executed. Detected signal by signal treatment has been expressed in visual not RF signal. By doing so the convenience of defect detection has been attempted and the effectiveness of defect signal visualization using Lamb wave has been confirmed compare with defect image through SAT.