Ultrasonic Evaluation of Planar Defects Using Infinite Elements

Time-of-Flight Diffraction (TOFD) technique is a well-known inspection method used in ultrasonic nondestructive evaluation. This inspection technique is based on the time of arrival of the diffracted echoes from the tips of planar discontinuity. This is in contrast with the conventional ultrasonics, which relies on the amplitude of specular reflections received from discontinuities. Like any other technique, ToFD has its limitations. In this paper, the finite element method is employed to evaluate the planar defects using ultrasonic time-of-flight diffraction method. The commercially available software ABAQUS/Explicit is used to simulate the ultrasonic wave behavior in the wedge transducers, specimen and wave interaction with the embedded planar defect. The CPE4R plane strain element is employed for discretization of the steel specimen and wedge transducers. The CINPE4 infinite element is also used on the wedge side walls for reducing unwanted echoes and noise reduction inside the ultrasonic wedge. The wave attenuation of the Plexi-glass wedge is simulated as the mass and stiffness proportional damping model. Evaluation and sizing of various defects shows that, the accuracy of the proposed method is within acceptable range comparing to the conventional ToFD method.