A study of total focusing method for ultrasonic nondestructive testing

Commercial ultrasonic phased array (PA) systems can perform multiple inspections in real-time using array transducers. This approach involves firing array elements in a particular sequence to produce high-resolution images at a high frame rate with excellent signal-tonoise ratio (SNR). Unfortunately, PA systems are complex and expensive. This study proposes a simpler, cheaper, non-real-time ultrasonic array system incorporating the total focusing method (TFM), and the performance of the proposed system is compared with that of a commercial PA system. Studying results shows that both systems have similar apparent axial resolution, but the apparent lateral resolution of the proposed system is far better than the L-scan but falls short in S-scan of a commercial PA system under a quiet testing environment. Moreover, the array performance indicator (API) values of TFM are lower than those of S-scan and L-scan, and the TFM has the highest SNR than the other methods. These results show that the performance of TFM array system is better than the commercial PA system, except for time consumption when switching the channels. Automatically switching the source and receiver channels could further the development of inexpensive, high-performance TFM arrays for ultrasonic nondestructive testing (NDT). It is anticipated that rapid advancements in electronic components, computer science, and digital signal processing will lead to improvements in near-real-time TFM array systems. Copyright by ASTM Int'l (all rights reserved).