金属板结构疲劳损伤二倍频兰姆波检测方法研究

针对重大基础设施安全运行需要,本文进行了金属板结构疲劳损伤非线性兰姆波检测方法研究。基于兰姆波二次谐波产生条件,确定了产生二次谐波积累增长效应的两种兰姆波模态及对应的激励频率。通过有限元仿真,研究了材料性能改变对兰姆波非线性效应的影响,证明了二倍频兰姆波非线性系数对材料性能退化表征的有效性。在此基础上,开展了金属板结构疲劳损伤非线性兰姆波检测实验研究。将极性反转方法应用于疲劳试件检测实验中,有效提高了检测信号中二倍频兰姆波的幅值和信噪比。实验结果表明,两种兰姆波模态对的二次谐波非线性系数均随疲劳损伤增加呈线性增长趋势,但基频S(0,2)模态和二倍频S(0,4)模态对对疲劳损伤检测的灵敏度更高,更适合金属板结构疲劳损伤检测。

Fatigue damage detection in metal plates using second harmonic Lamb waves

For the safe operation of critical infrastructure,a nonlinear Lamb wave technique is proposed for fatigue damage detection in metal plates.Based on the second harmonic generation conditions of the Lamb wave,the two Lamb wave modes and corresponding excitation frequencies that can produce the second harmonic accumulation growth effect are determined.The effect of material properties change on the nonlinear effect is investigated by the finite element simulation,which proves the validity of the two harmonic nonlinear coefficients for the characterization of material properties degradation.The nonlinear Lamb wave experiments are conducted to detect fatigue damage in metal plates.The polarity inversion method is applied to the fatigue specimen detection experiments,which can effectively improve the amplitude and signal-to-noise ratio of the harmonic components in the detection signals.The experimental results show that the second harmonic nonlinear coefficients of both Lamb wave mode pairs increase linearly with the increase of fatigue damage,but the mode pair consisting of fundamental S(0,2)and harmonic S(0,4)is more sensitive for fatigue damage detection and is more suitable for fatigue damage detection f metal plates.