Crack Detection in Concrete Parts Using Vibrothermography

This study investigates the use of vibrothermography to detect cracks in concrete parts, developing acoustic excitation devices (sonic and ultrasonic and low- and high-power excitation devices) and examining the influences of excitation frequency, power, and pressure on the ability to detect cracks. Experimental results demonstrate that this inspection technique can suitably detect concrete cracks: Ultrasound at frequencies from 20 to 100 kHz could be used to excite concrete cracks with notable temperature rise; coarse aggregates in concrete do not interfere with the ability to detect cracks; high-power ultrasound enhances crack detection though intense scattering of attenuation that could be induced by coarse aggregates. Moreover, the stimulus horn designed as part of this study can input ultrasound at high power into concrete parts without damaging the contact surface, while the custom-made pressure loading sleeve can steadily exert force on the transducer during excitation; the optimal force exerted on KMD ultrasonic transducers with a rated power of 50 W is ~ 1500 N, which can make the transducer output enough power to detect cracks.