Abstract

The flexural ultrasonic transducer (FUT) consists of a piezoelectric ceramic bonded to an edge-clamped elastic plate, for both generation and detection of ultrasound waves. It is typically employed for proximity measurement, such as in automotive parking systems, and for flow measurement in gases and liquids. Conventional industrial applications have generally incorporated FUTs with resonance frequencies up to around 50 kHz. However, there have been recent advances in the understanding of the FUT, both in terms of fabrication and operation, enabling the potential for measurement in a wider range of applications, including those of elevated pressure, temperature, and requiring multiple operating frequencies. Ultrasound measurement with FUTs at frequencies greater than 50 kHz is desirable in a range of applications, including gas and water metering in petrochemical plants, district heating, and power industries. The major restricting limitation of designing transducers to operate at these higher frequencies has been a relatively poor understanding of these transducers work, including optimisation of design and performance, and the few reports into how different modes of a FUT can be utilised for practical and reliable measurement. In this study, the higher order modal dynamics of the FUT are investigated through measurement of high frequency ultrasound waves in air, for different fundamental operating modes. A combination of experimental techniques is applied, comprising electrical impedance analysis and laser Doppler vibrometry. The experimental research is supported by analytical solutions to reveal complex higher order modal dynamics of the FUT. This investigation represents further development in widening the industrial application potential of the FUT.

Highlights

  • The flexural ultrasonic transducer (FUT) has recently been investigated as an in-situ measurement device for applications such as flow measurement [1]

  • The principal contribution of this study is the demonstration of higher order modal dynamics of the FUT which can be encountered in operation, thereby enabling the future design of optimised configurations which can exploit such modes of vibration

  • Electrode connections are made on the piezoelectric ceramic disc, before the FUT is sealed at the rear, often with a compliant material such as silicone rubber

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Summary

Introduction

The flexural ultrasonic transducer (FUT) has recently been investigated as an in-situ measurement device for applications such as flow measurement [1]. One of the principal limitations of FUT-based measurement technology at present, is that commercially available devices are generally only designed for operation up to around 50 kHz [3], typically at the fundamental axisymmetric (0,0) and (1,0) modes.

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