Phased array ultrasonics can be used as a rapid tool for imaging and sizing crack-like defects. This paper reports the simulation of phased array ultrasonic wave interaction with the defects using the finite-difference time domain (FDTD) method. Experiments were conducted to validate modeling results for pulse-echo simulations of the phased array transducer on a mild-steel (MS) pipe sample with circumferential internal surface notches of three different sizes. Experiments were carried out on the MS pipe specimen using a conventional ultrasonic technique with a 5 MHz transducer at 45° refracted angle within the specimen and the defects were imaged and sized using the relative arrival time technique (RATT). The experimental B-scans obtained using the conventional ultrasonic techniques were compared with the experimental B-scans obtained using the phased array instrument. Simulation studies were also carried out by steering the beam to the requisite angles by the phased array transducer to study the effect of various angles of incidence on the defect definition, i.e., with respect to imaging and sizing, using the RATT. © 2007 Elsevier Ltd. All rights reserved.