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Defect characterization using ultrasonic arrays

There has been a massive increase in the use of ultrasonic arrays for non-destructive evaluation (NDE) in recent years. However, much of this technology is either based on medical ultrasound imaging or is designed simply to mimic traditional NDE inspections performed with monolithic transducers. This paper addresses the issue of array system design and data processing specifically for quantitative NDE. It is shown that arrays offer huge potential for defect characterization in NDE beyond that currently exploited and possible directions are discussed. In particular, it is shown that obtaining all the time-domain signals from every transmitter receiver combination combined with post-processing is the preferable strategy for NDE. Not only can information in the full data-set provide the highest possible resolution image, but that it can also be exploited to perform sub-wavelength reflector characterization by extracting portions of the reflector scattering matrix. Experimental results on artificial defects are used to illustrate this point.