Abstract: Metal fatigue and damage mostly occur on the surface in early stages. When high-frequency alternating current excites the metal to be tested, the current mainly flows through metal surface due to skin effect. In this paper, the analysis of a model of cylindrical metal surface damage shows that these damages prevent the current from passing near the surface, and this result in a significant increase in highfrequency resistance. Phaselocked amplifiers are used to measure the voltage across copper and iron at different degrees of damage under different frequencies of AC excitation. The changes of resistance with frequency are calculated and compared. The results show that the resistance difference of samples with the same specification and different damage degrees is very small at low frequency and remarkable at high frequency. The experiment proves that skin effect can highlight the influence of metal surface damage on AC resistance of samples. The degree of surface damage of sample can be sensitively characterized by measuring the high-frequency skin resistance of metal. This nondestructive testing method is relatively sensitive. It can be used to detect the fatigue degree of metal samples as a whole, not as point by point. This method can save cost.

Key words: skin effect, high frequency resistance, surface damage, nondestructive testing