Comparitive Evaluation between Ultrasonic Phased Array and Synthetic Aperture Focusing Techniques

Abstract

Single‐element scanning techniques are widely used in the NDT industry and have seen a number of successful applications. They require moving the sensor in time‐consuming raster scan to create two‐dimensional scan patterns and several transducers are required to focus at different levels in the inspected material. However, phased array technology is an emerging NDI technology which offers means to focus the ultrasonic beam at different locations and steer it to reach defects at hidden parts in complex structures, hence, substantially reducing the scanning time and simplifying the scanning pattern by scanning electronically in milliseconds instead of scanning mechanically in a few seconds. The motivation of this work is to investigate and compare electronic and SAFT (synthetic focusing) of the ultrasonic waves using linear phased array transducers. Experimental tests were done on an aluminum block with side‐drilled holes to simulate defects. Reduction of calculation time for the SAFT algorithm was achieved using beam width limitation. Experimental SAFT results and results from phased array system were compared. Practical SAFT advantages and limitations are then highlighted and requirements for better performance are discussed.