贵金属超薄镀层厚度的超声显微测量

超声检测作为一种无损检测技术逐渐被应用到金属镀层厚度的测量中，但在纵波超声的盲区范围内，超薄镀层的超声信号往往会与界面波信号发生强耦合，使得超薄镀层厚度信息难以被直接提取。因此，以超声显微测量为依托，创新出一个超声特征参量—频谱样本熵；并基于软测量的思路，在频谱样本熵和超薄镀层厚度之间建立映射关系，实现对贵金属镀层厚度的准确表征与预测。利用镀层厚度为百微米级的纯银镀金试样进行验证实验，结果表明：基于频谱样本熵的预测模型平均精度可达94.7%，优于传统超声特征分析方法，验证了新型量化表征方法的有效性。

Ultrasonic microscopic measurement for ultra-thin coating thickness of precious metals

As a nondestructive testing technology, ultrasound is gradually applied to the thickness detection of metal coating. However, the echo generated by coating always overlaps with the interface echo in the ultrasonic blind zone, leading to the difficulty in extracting the information of ultra-thin coating thickness. Therefore, based on the ultrasonic microscopic measurement, an ultrasonic characteristic parameter, spectral sample entropy, was introduced in our measurement. According to the idea of soft-sensing, a mapping relationship was established between the spectral sample entropy and the ultra-thin coating thickness to achieve precise prediction for the coatings thickness of precious metals. Pure silver samples with hundred micron-sized gold coating were used to perform verification experiments. The results showed that the accuracy of the prediction model based on spectral sample entropy could reach 94.7%, better than the predicting outcomes of analysis using traditional ultrasonic feature, indicating this new quantitative characterization method is effective.