基于趋肤效应测量金属表面损伤的实验研究

Experimental study of metal surface damage measurement based on skin effect

金属疲劳和损伤早期多发生在金属表面,受趋肤效应的影响,高频交流电激励待测金属时电流主要流经金属表面.本文对圆柱形金属表面损伤模型的分析结果表明这些损伤阻碍电流在表面附近的通过,导致高频电阻升高明显.实验采用锁相放大器,测量了铜、铁表面在不同损伤程度、不同频率交流电激励下测试点两端的电压,计算并对比其电阻随频率的变化,结果表明相同规格、不同损伤程度的样品电阻在低频激励时差别较小,高频激励时差别显著.本研究通过实验证明基于趋肤效应测量金属高频交流电阻可以更加灵敏的表征金属表面损伤程度,趋肤效应下表面存在损伤的金属样品高频电阻发生明显变化.基于趋肤效应测量金属表面损伤的方法可以从整体上反应金属样品的损伤程度,不需要逐点寻找缺陷位置,大大节约了测量成本.

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.