Определение координат отражателей в плоскости, перпендикулярной сварному соединению по эхосигналам, измеренным преобразователями по схеме TOFD

Abstract

The TOFD method, which is widely used in ultrasonic flaw detection, makes it possible to distinguish a crack from a volume reflector by the phase of the echo signals and to determine its height with high accuracy. However, the TOFD method without scanning the piezoelectric transducers across the weld joint does not allow to determine the displacement of the reflector from the center of the welded joint, which is very important when evaluating the results of the control. The scanning devices used for this purpose have a complex design, their price is higher than that of one-dimensional scanning devices, and, most importantly, the control time increases significantly. If the echo signals reflected from the bottom of the object of control are used, taking into account the change in the wave type, then a combined image of the reflector can be obtained from a set of partial images recovered by the digital focusing antenna (DFA) method. If we use the echo signals measured in the combined mode for each piezoelectric converter, we can estimate the displacement of the reflector across the welded joint with an accuracy of ±1.5 mm. Numerical and model experiments have confirmed the efficiency of the proposed approach.