Optimal Design Parameters for a Phased-Array-Based Ultrasonic Polar Scan

Abstract

In the context of a next-generation Ultrasonic Polar Scan (UPS) measurement system, this research aims to look at the possibility to use a set of cylindrically focused emitters in conjunction with a Circular Phased Array (C-PA) receiver in order to create a portable measurement system, while improving the data quality. To do so, an three-dimensional analytical model is presented to simulate UPS experiments with the proposed system. In addition, a post-processing procedure is worked out to treat the acquired raw data with the aim to reconstruct the angle dependent plane wave reflection coefficients of the sample under study. As this reconstruction will depend heavily on various design parameters, three parameter studies are performed to find the optimal design. First, it the radius of the C-PA and the used frequency are varied, and it is shown that given a particular frequency, the radius must be large enough to capture the full reflected field such that an accurate reconstruction of the plane wave characteristics can be performed. Second, the emitter and receiver widths are varied and it is shown that by increasing either of them, better results can be achieved. However, in order to get the best results, both widths should be considerably large. Third, the pitch and the angular range of the cylindrically focused emitters are varied, and it is shown that if the pitch is too large, aliasing effects will disturb the results. However, this effect can somewhat be mitigated by using multiple emitters with a restricted angular range. Using the knowledge of the previous parameter studies, a simulated UPS experiment using a good set of design paramters is performed for a cross-ply Carbon Epoxy laminate which shows an excellent agreement with the theoretical plane wave results.