- 作者: Shiuh-Kuang Yang
- 中文摘要: The objective of this research was to establish a laser-ultrasound system for NDT (nondestructive testing) evaluation of adhesive bonded joints. In this study, the surface waves were launched thermoelastically to the samples using a Q-switched Nd:YAG pulsed laser. The samples were also tested using surface waves launched by a PZT (piezoelectric) transducer. The experimental data from both tests were then compared to evaluate the benefits or drawbacks of using laser ultrasound. It was found that the laser-induced ultrasound was free of couplant and had good reproducibility and no transmission loss. However, the ultrasound generated by the laser in the thermoelastic regime had low propagating energy and SNR (signal to noise ratio), thus increasing the difficulty of measurement. Several solutions were used in this study to overcome the above-mentioned drawbacks. First, the rise time of the signal was shortened by reducing the radiated spot area of the incident laser beam. Second, an optical slot was added to the original laser system to adjust the geometry of the radiated area of the incident laser beam. The theoretical directivity patterns of the related dimensions of the slots were calculated and compared with the experimental results. The results indicated that we could adjust the directivity patterns by means of the slot. It is concluded that laser-induced ultrasound with good propagation energy and SNR can be generated and used in NDT applications. Furthermore, adhesive bonded joints indeed can be evaluated using laser-induced ultrasound.
- 英文摘要: --
- 中文關鍵字: laser-ultrasound, adhesive joint, surface wave, directivity pattern
- 英文關鍵字: --