Development of quantitative low frequency ultrasonic testing and its application to nondestructive evaluation of concrete structures

点击翻译按钮获取中文摘要

The objective of this research is the development of quantitative low frequency ultrasonic testing in the range of several 10kHz to 100kHz, in which major topics are 1. fundamental properties of low frequency ultrasonic method, 2. numerical method for low frequency ultrasonic wave method and 3. application to concrete structures.1. Fundamental properties of low frequency ultrasonic method :Our review of papers related to ultrasonic transducers showed that there are few works on transducers producing low frequency ultrasonic waves. It was also found that commercial transducers for ultrasonic nondestructive testing of concrete are not designed under the optimum condition based on the wave theory. Applicability of laser vibrometer to nondestructive testing for concrete was investigated.2. Numerical method for low frequency ultrasonic testing:A low frequency ultrasonic wave method is applied to large-scale infrastructures. In numerical simulation of the ultrasonic testing, therefore, large-scale calculation is required. To this end, we developed a 2.5-D boundary element method and a fast multipole boundary element method, both of which are effective for large-scale wave analyzes.3. Application to concrete structures :Low frequency ultrasonic testing was applied to the evaluation of debonding on material interface and the evaluation of PC grouting. In the evaluation of interface debonding, an L-scan method with use of leaky surface waves was demonstrated as a better method than a conventional C-scan method. In the PC grout evaluation, the wavelet transform was used for the wave analysis obtained by impact-echo method and comparison between theory and experiment was carried out.