Study on movement measurement for internal defects in concrete structures by noncontact acoustic inspection method using correlation processing

Abstract

The noncontact acoustic inspection method using acoustic irradiation induced vibration and a scanning laser Doppler vibrometer can detect internal defects in the surface layer of concrete structures, etc., over long distances and without contact. Since this method uses flexural vibration in principle, it can be used as an alternative method to tapping inspection. Therefore, there has been an increase in requests for realizing movement measurement. Thus, an experiment was conducted to verify whether movement measurement was possible by mounting multiple LDVs and sound sources that did not have scanning mechanisms on a moving trolley. The experimental results revealed that by using cross-correlation processing between the transmitted and received waveforms, it is possible to perform movement measurements at low speeds of about 2 km/h.