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首页> 外文期刊>Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions on >High-temperature (>500u000b0;c) wall thickness monitoring using dry-coupled ultrasonic waveguide transducers
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High-temperature (>500u000b0;c) wall thickness monitoring using dry-coupled ultrasonic waveguide transducers

机译：使用干耦合超声波导换能器监控高温（> 500u000b0; c）壁厚

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摘要

Conventional ultrasonic transducers cannot withstand high temperatures for two main reasons: the piezoelectric elements within them depolarize, and differential thermal expansion of the different materials within a transducer causes them to fail. In this paper, the design of a high-temperature ultrasonic thickness gauge that bypasses these problems is described. The system uses a waveguide to isolate the vulnerable transducer and piezoelectric elements from the high-temperature measurement zone. Use of thin and long waveguides of rectangular cross section allows large temperature gradients to be sustained over short distances without the need for additional cooling equipment. The main problems that had to be addressed were the transmission and reception of ultrasonic waves into and from the testpiece that the waveguides are coupled to, and optimization of the wave propagation along the waveguide itself. It was found that anti-plane shear loading performs best at transmitting and receiving from the surface of a component that is to be inspected. Therefore, a nondispersive guided wave mode in large-aspect-ratio rectangular strips was employed to transmit the anti-plane shear loading from the transducer to the measurement zone. Different joining methods to attach the waveguides to the component were investigated and experiments showed that clamping the waveguides to the component surface gave the best results. The thickness of different plate samples was consistently measured to within less than 0.1 mm. Performance at high temperatures was tested in a furnace at 730u000b0;C for 4 weeks without signal degradation. Thicknesses in the range of 3 to 25 mm could be monitored using Hanning windowed tonebursts with 2 MHz center frequency.
机译：传统的超声换能器不能承受高温，主要有两个原因：其中的压电元件会去极化，换能器内不同材料的差异热膨胀会导致它们失效。在本文中，将描述绕过这些问题的高温超声波测厚仪的设计。该系统使用波导将易损的换能器和压电元件与高温测量区域隔离。使用矩形横截面的细长波导可以在短距离内维持较大的温度梯度，而无需额外的冷却设备。必须解决的主要问题是与波导耦合的测试件进出超声波，以及优化沿波导本身的波传播。已经发现，抗平面剪切载荷在从要检查的组件表面进行发送和接收时表现最佳。因此，采用大纵横比矩形带中的非分散导波模式将反平面剪切载荷从换能器传递到测量区域。研究了将波导连接到组件的不同连接方法，实验表明，将波导夹在组件表面可获得最佳效果。一致地测量了不同板样品的厚度，使其小于0.1毫米。在730u000b0; C的熔炉中测试了高温下的性能4周，而没有信号衰减。可以使用中心频率为2 MHz的Hanning窗音突发来监视3到25 mm范围内的厚度。

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