Trailing pulses self-focusing for ultrasonic-based damage detection in thick plates

Ultrasonic detection is one of the most commonly used methods in nondestructive testing. Trailing pulses that can be observed in plates and cylindrical rods are a list of longitudinal ultrasonic waves. However, the complexity of trailing pulses brings challenges for ultrasonic–based nondestructive testing. In this paper, a trailing pulses self-focusing method for damage detection in thick plates is proposed by utilizing physical characters of trailing pulses. Firstly, the characteristics of trailing pulses are analyzed by theoretical derivation. Then, three steps of trailing pulses self-focusing method including correlation filtering, energy envelope screening and defect matching are introduced. After that, the trailing pulses of single defect can be focused and the accurate positions of defects can be obtained as well. Finally, a prospective application of trailing pulses, which uses ultrasound phased array (UPA) for nondestructive testing, is discussed. The experiment is carried out on an aluminum plate with a remarkable thickness, which illustrates the effectiveness of the method.