Subsurface Interfacial Defects of Metal Materials Testing Using Ultrasound Infrared Lock-in Thermography

A novel non-destructive ultrasound infrared lock-in thermography (ULT) testing method was presented in order to detect metal specimens with subsurface contacting interfacial defects. An experimental platform was built. Experiments had been carried out to Q235 plates with different testing parameters. The testing effect of amplitude and phase images was analyzed, and the relation between amplitude difference, phase difference, signal-to-noise ratio and modulation frequency was discussed. An adaptive neuro-fuzzy inference system model was built to forecast the depth of defects.