Induction thermography of steel coupons with cracks

The induction thermography technique was assessed experimentally and numerically on notched steel coupons using two coil configurations: straight line and loop conditions. The coupons had different lengths of fatigue crack varying from zero to 3 mm. The numerical predictions showed that the peak temperature was always located at the crack tip or the notch tip position. The loop coil resulted in higher temperatures than those of the straight line coil. Results showed that the numerical methods effectively supported the application assessment of this nondestructive evaluation (NDE) technique for the steel material, but crack geometry remains a challenge as the exact shape of a natural crack is typically unknown. It is shown that induction thermography can detect a crack as small as 1 mm in the notched steel coupons. Commentary on the application of the NDE technique with the numerical modeling support was provided.