Interaction analysis of different defects with laser ultrasonic sound waves and defect characterization

Abstract

The paper presented a novel approach for characterization of defects based on laser ultrasonic nondestructive testing. Both flat materials and curved materials are used as experimental samples, and crack-type defects and circular defects with different depths are applied as experimental objects. Through analyzing the interaction between different defects and acoustic waves, a novel characterization algorithm is proposed based on the energy loss theory to realize the characterization of defects. In more specific details, the defects are firstly scanned by laser ultrasonic test platform to obtain the wave field diagram. Then, the interaction between defects and the sound waves is analyzed, and the type of defects is determined based on the shape of the reflected waves. Finally, the interaction analysis and quantitative characterization are carried out through the reflection energy coefficient, and compared with other characterization methods. It was found that for circular defects in materials with different shapes, the reflection energy coefficient increases with the increases of defect depth. But for crack-type defects, when the depth is greater than 0.5 mm, the reflection energy coefficient increases first and then reaches a stable value. Through the study, not only the interaction between defects and sound waves is analyzed and verified, but also the proposed approach can be adopted for qualitative and quantitative characterization of defects.