Skip to main content
Article thumbnail
Location of Repository

Ultrasonic air-coupled capacitive arrays

By Adrian Neild

Abstract

A model is developed which is capable of predicting the pressure field of a rectangular source, as measured by a finite-sized receiver. This novel method treats the problem in a new way, which allows an integration to be performed over the area of the receiver. Previously it has only been possible to model two circular transducers coaxially aligned. The model is used to identify a receiver, which can be used to measure the highly focussed pressure field from a phased array, with only a negligible effect due to the receiver size. Productions from the model are compared to experimental data, and show a good correlation.\ud \ud A parabolic mirror used to focus the field from a circular device in air has been studied, and a model developed to predict the pressure field produced by this device. This is done by an approximation of the mirror surface to a grid of finely spaced points. The model correlates well with measured results. In addition, an image of a defect in a solid sample was produced.\ud \ud Arrays are then used to image solid samples in air. This is done using three techniques. The first is a combined phased source and receiver, which is shown to locate a wire accurately and to measure a step in the surface of a sample. A 2-D array is shown to image a defect in a composite plate, and the potential for a fast through-transmission air-coupled system is indicated. In addition, two post-processing techniques are used on data recorded using an array receiver, to locate an object in air. Of these two techniques, ellipse crossing is shown to have better results for large signal to noise ratios, and SAFT for lower ratios.\ud \ud The combination of theoretical modelling and experimental observations has indicated that the transducers and arrays constructed for use in air are well-understood, and that their characteristics can be predicted

Topics: TA, QC
OAI identifier: oai:wrap.warwick.ac.uk:2663

Suggested articles

Citations

  1. 64 Elements two-dimensional piezoelectric array for 3-D imaging, " doi
  2. 7: Imaging with ultrasonic capacitive arrays [4] doi
  3. A New System for RealTime Synthetic Aperture Ultrasonic Imaging, " doi
  4. (1992). Application of SAFT on Composites, "
  5. Experiences with synthetic aperture focussing techniques in the field, " doi
  6. (2002). Impact damage growth in composites under fatigue conditions monitored by acoustography, " doi
  7. Improvement of ultrasonic testing of concrete by combining signal conditioning, scanning laser vibrometer and space averaging techniques, " doi
  8. In situ monitoring in real tiem of fatigue-induced damage growth in composite materials by acoustography, " doi
  9. Performance of laserultrasonic F-SAFT imaging, " doi
  10. (2001). Radiated fields of rectangular air-coupled micromachined transducers, " presented at the doi
  11. SAFT- the evolution of a signal processing technology for ultrasonic testing, " doi
  12. The Effects of Surface Mapping Corrections with Synthetic-Aperture Focussing Techniques on Ultrasonic Imaging, " doi
  13. (2002). Theoretical modelling of a planar piston field focussed by reflection, " presented at the doi

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.