匹配层厚度对弛豫单晶换能器性能的影响

Effect of Matching Layer Thickness on Performance of Relaxed Single Crystal Transducer

针对改进匹配层厚度以提高弛豫单晶换能器性能的问题,文中通过理论和试验研究了匹配层厚度对弛豫单晶性能的影响。根据声波的反射和折射规律,分析了匹配层声阻抗和厚度变化和声强透射率的关系。建立导波检测试验系统,以不同厚度的刚玉作为匹配层进行试验,刚玉通过环氧树脂胶水粘贴在驰豫单晶负极,并使用502胶水与管道连接,采用压电陶瓷片激励超声导波,驰豫单晶接收回波信号。理论分析表明,声强透射率随匹配层声阻抗的增大而增大,随匹配层厚度增大而呈周期性变化。在匹配层厚度较小(<1 mm),声阻抗>5×106Pa·s/m时,匹配层材料和厚度对声强透射率的影响较小。试验结果表明,在低频区,匹配层厚度的增加有益于回波系数的提高;在高频区,回波系数随匹配层的增大而先增大后减小。

In order to improve the performance of the matched layer transducer to improve the performance of the relaxor single crystal transducer, the effect of the thickness of the matching layer on the properties of the relaxor single crystal was studied by theoretical analysis and experiment. According to the reflection and refraction law of acoustic wave, the relationship between acoustic impedance and thickness variation and sound transmittance of the matching layer was analyzed.The test system of pipeline guided wave detection was established,and the test was carried out with different thickness of corundum as the matching layer. The corundum was adhered to the anode of the relaxation single crystal through the epoxy resin glue, and 502 glue was connected with the pipeline. The piezoelectric ceramic was used to stimulate the ultrasonic guided wave , Relaxation of single crystal to receive echo signals. Theoretical analysis showed that the sound intensity increases with the increase of acoustic impedance of the matched layer, and varies periodically with the increase of the thickness of the matched layer. When the thickness of the matching layer is small （〈1 mm） and the acoustic impedance is more than 5×10^6 Pa·s/m, the material and thickness of the matching layer have little influence on the sound transmission. The experimental results show that in low frequency region, the increase of the thickness of the matching layer is beneficial to the improvement of the echo coefficient. In the high frequency region, the echo coefficient increases first and then decreases with the increase of the matching layer.