Applications of micromachined capacitance transducers in air-coupled ultrasonics and nondestructive evaluation

Schindel, D.W.; Hutchins, David A.

doi:10.1109/58.368313

Cited by 98 publications

(28 citation statements)

References 22 publications

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“…Electrostatic transducers, such as capacitative micromachined ultrasonic transducers (CMUTs) [11], [12], have been demonstrated to have excellent coupling to air, as well as an enhanced bandwidth. However, the requirements of a large bias voltage, as well as a thin flexible membrane as the radiating front face, can be problematic for some applications, including gas flow measurements, where intrinsic safety is highly critical.…”

Section: Introductionmentioning

confidence: 99%

Experimental and simulation characterisation of flexural vibration modes in unimorph ultrasound transducers

2016

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Abstract-Two unimorph flexural transducer designs are proposed and tested with regard to mode shapes and frequencies. The transducers consist of a passive metal cap structure, and a thin piezoelectric disc rigidly bonded to the inside. Extensive finite element modelling, and experimental 2D, time-resolved displacement measurements were done to characterise the transducers flexural properties, and to compare them to the analytical solutions of thin vibrating plates. Emphasis was put on characterising the passive layer of the unimorph structure, before bonding the piezoelectric element, to understand how the active element affects the behaviour of the flexing plate. A high power Nd:YAG laser was used to actuate the metal plate (non-contact), and the frequency content of the resulting displacement signal was analysed to identify the flexural modes. The non-axisymmetric modes, which are conventionally disregarded because of their unfavourable acoustic properties, were also taken into account. There was excellent agreement between the experimental results and the FE simulation data. There was good agreement with the analytical edge clamped plate model, but with some notable deviations, which have not previously been identified or commented upon. Specifically, the second axisymmetric mode is split into three separate modes, which is not explained by the traditional theory of plates. The analysis is similar to that of contemporary pMUT research, but with the proposed macroscopic dimensions and passive metal layer making the transducer industrially robust, cheap and easy to manufacture, and more suitable for a different range of applications where these aspects are of importance.

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Section: Introductionmentioning

confidence: 99%

Experimental and simulation characterisation of flexural vibration modes in unimorph ultrasound transducers

2016

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“…3,4) Recently, the capacitive transducer has been well refined to operate at wider frequency range with flat response due to micro-machined manufacturing. 5,6) The capacitance transducer is mainly consisted in just two parts. One is the front vibrating membrane with thinly coated electrode, and the other is solid conductive back-plate with micro-sized air pockets.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Investigations of Transmission Coefficients of Longitudinal Waves through Metal Plates Immersed in Air for Uses of Air Coupled Ultrasounds

et al. 2008

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Theoretical and experimental investigations of transmission coefficients of longitudinal waves through metal plates immersed in air have been carried out for noncontact and nondestructive testing (NDT) of metal plates. Transmission coefficients through metal plates in water and through polymer plates in air have also been shown for comparisons. Theoretical relations between the transmission coefficients and the Lamb wave dispersions were described. It was confirmed that the transmission coefficients took high values when the Lamb waves were generated without exception. Quantitative evaluations for the transmission coefficients were investigated for the use of the air-coupled ultrasounds. The experimental verifications were carried out using 1-, 3-, and 5-mm-thick aluminum plates. The experimental results of the transmission coefficients were in fairly good agreement with the theoretical predictions.

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“…However, the potential advantages and limitations of using air coupling in non-destructive material inspections have been studied in the literature. In particular, air coupling was found desirable in applications involving the inspection of materials that could not be immersed in water or that would be damaged by physical contact with an ultrasonic transducer [5]. Such materials include propellants, certain wood and paper products, foams, art objects, and many advanced composite materials used by the aerospace industry.…”

Section: Introductionmentioning

confidence: 98%

Lamb waves beam deviation due to small inclination of the test structure in air-coupled ultrasonic NDT

et al. 2006

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Applications of micromachined capacitance transducers in air-coupled ultrasonics and nondestructive evaluation

Cited by 98 publications

References 22 publications

Experimental and simulation characterisation of flexural vibration modes in unimorph ultrasound transducers

Experimental and simulation characterisation of flexural vibration modes in unimorph ultrasound transducers

Theoretical and Experimental Investigations of Transmission Coefficients of Longitudinal Waves through Metal Plates Immersed in Air for Uses of Air Coupled Ultrasounds

Lamb waves beam deviation due to small inclination of the test structure in air-coupled ultrasonic NDT

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