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给出了一种基于混频效应的非线性超声微裂纹检测方法。首先,对结构损伤混频检测机理及信号特征提取方法进行了理论分析,之后,根据试件中差频分量及和频分量幅值分布随激励信号频率变化关系,优化确定出混频检测参数。最后,进行了异侧混频激励下无损检测试验研究,并分析了激励信号频率变化对混频检测效果的影响。结果表明,异侧激励混频检测模式不仅可以实现结构中疲劳微裂纹检测,而且可以实现缺陷的定位。且检测信号频率选择对混频检测信噪比有一定的影响。当检测信号中的混频分量幅值最大时,混频检测效果最佳。因此,在优化检测参数基础上,异侧混频激励检测模式可以很好实现结构微裂纹的检测与定位。
A nonlinear ultrasonic crack detection method based on mixing effect is given. First of all, the mechanism of structural damage detection and signal feature extraction are theoretically analyzed. After that, the parameters of the mixing detection are optimized based on the relationship between the difference frequency components and the amplitude distribution of the sum frequency components with the excitation signal frequency. Finally, a non-destructive testing experiment is carried out under the excitatory mixing excitation, and the influence of the variation of the excitation signal frequency on the mixing detection effect is analyzed. The results show that the heterogenous excitation mixing detection mode can not only detect the fatigue microcracks in the structure but also locate the defects. The frequency of the detection signal has some influence on the signal-to-noise ratio of the mixer. Mixing detection works best when the amplitude of the mixing component in the detection signal is maximum. Therefore, on the basis of optimizing the detection parameters, the detection mode and the location of the structure microcracks can be well achieved with the detection mode of the out-of-plane mixing excitation.