IMPACT OF ELEMENTS SENSITIVITY AND PULSE EXCITATION ON PHASED ARRAY
IMAGING
Marc-Antoine BLANCHET and Kevin COTTON
SONATEST ADVANCED PRODUCTS
Québec, Canada
blanchetm@sonatest.com cottonk@sonatest.com
Abstract
Ultrasonic inspection using phased-array technology is reaching a stage of maturity in many
countries. Although most concepts used in conventional NDT still apply, phased-array has its own
specificities that change the way we need to think about them. This paper presents the impact of the
element sensitivity variation on the echo-transmittance curve pattern. It can be demonstrated that
variations in elements sensitivity significantly impact the usual echo-transmittance patterns found in
conventional UT. Experimental results present typical curves for linear array and demonstrate how
both angular corrected gain and time corrected gain features can compensate for these variations.
The second part of this paper revisits the way an array transducer can be excited. With the
advances in transducer array manufacturing and material properties, NDT equipment manufacturers
now have access to high quality, large bandwidth transducers. Experimental results using negative
square pulsing, bi-polar pulsing and spike pulsing are presented, with their impact on pulse
duration, echo amplitude and overall signal quality.
Part 1 – Echo-Transmission - Introduction1
The basic physics principles of beam divergence, near field and far field sound pressure are still
fully valid when performing phased array ultrasonic inspection. It is important to have a deep
understanding of these concepts to avoid erroneous measurements. As phased array transducers are
composed of multiple elements, typically ranging from 16 up to 128 elements, the echotransmission
at the wedge/part interface is significantly affected by the elements sensitivity
uniformity. This first part of the paper presents the preliminary results obtained when measuring
echo-transmittance.
1 Please take note that at the time of publishing this paper, data analysis was still being completed.
Consequently, only preliminary results are presented. Exhaustive analysis will be presented at
conference time. |