Effect of driving frequency on non-linear coupling between ultrasound transducer and target under inspection in Sonic Infrared Imaging

• The nonlinear effect of driving frequency on the Sonic IR imaging system is investigated.
• The 20 kHz transducer are the best among the three individuals: 20 kHz, 30 kHz, 40 kHz.
• The non-linear coupling effect between ultrasound transducer and target is observed.
• The duct tape coupling material is better than leather as coupling material.

Sonic Infrared (IR) Imaging, also referred as vibrothermography, is a novel Nondestructive Evaluation (NDE) technology to find cracks through infrared imaging of vibration-induced crack heating. The vibration source plays an important role in the detection of cracks. In this paper, the effect of driving frequency on the ultrasound vibration to the thermal imaging is presented. The research is organized by using different frequency system and coupling materials on the same aluminum bar sample. The analysis is conducted by combination of the vibration waveforms with the IR images and signals. Correlation analysis between the acoustic energy and the thermal energy in the crack is discussed as well.