Jia Jiuhong, Wang Qiyue, Liao Zuoyu, Tu Yun, Tu Shan-Tung
Key Laboratory of Pressure Systems and Safety, Ministry of Education, East China University of Science and Technology, Shanghai 200237, China.
Materials (Basel). 2017 Sep 4;10(9):1027. doi: 10.3390/ma10091027.
Guided wave technique could be a possible method for monitoring components working in high temperature above 350 °C. However, this would require the design of an appropriate waveguide bar to transmit the wave, so that its sensing part is not influenced by the high temperature. In the present study, the shape of waveguide bars is designed based on the analysis of wave source characteristics. The critical frequency-width and frequency-thickness products of waveguide bars are analyzed theoretically and numerically to transmit the zeroth shear horizontal wave SH0* in bars. The results show that waveguide bars can cut off all the other wave modes when their frequency-thickness products are smaller than the critical value , and frequency-width products are not smaller than the critical value . Six waveguide bars are designed and fabricated based on the design criteria, and an experiment system is set up to check their work performance. The testing results indicate that the wave signals of the SH0* mode propagate clearly in waveguide bars, and cut off all the other modes when the frequency-thickness products and frequency-width products of the bars meet the design criteria. It is also demonstrated that the dependency of the experimental group velocity of each waveguide bar on frequency is in good agreement with the numerical result. High-temperature experiments also validate the reliability of the designed waveguide bars. Therefore, the critical frequency-thickness product and frequency-width product can be the basis for the design of the waveguide bars.
导波技术可能是监测工作在350℃以上高温环境中部件的一种可行方法。然而，这需要设计合适的波导杆来传输波，以使其传感部分不受高温影响。在本研究中，基于对波源特性的分析设计了波导杆的形状。从理论和数值上分析了波导杆的临界频率-宽度和频率-厚度乘积，以在杆中传输零阶水平剪切波SH0*。结果表明，当波导杆的频率-厚度乘积小于临界值且频率-宽度乘积不小于临界值时，波导杆可以截止所有其他波模。基于设计准则设计并制作了六根波导杆，并搭建了实验系统来检验其工作性能。测试结果表明，SH0*模式的波信号在波导杆中清晰传播，当波导杆的频率-厚度乘积和频率-宽度乘积满足设计准则时，截止了所有其他模式。还表明，各波导杆的实验群速度与频率的依赖关系与数值结果吻合良好。高温实验也验证了所设计波导杆的可靠性。因此，临界频率-厚度乘积和频率-宽度乘积可作为波导杆设计的依据。
