A hybrid model to calculate an ultrasonic field and a received signal by the angle beam technique is presented. In this model, the field in a test object transmitted by an angle beam transducer is calculated using the Rayleigh integral with the geometrical optics approximation, and the field scattered by a flaw is calculated by the finite-difference time domain (FDTD) method. The signal received by the transducer is obtained by calculating the inner product of the transmitted field and the scattered field at each grid point used in the FDTD method, and then these products are integrated over a predetermined calculation area. Since the calculation area in the FDTD method can be limited to around the flaw, the calculation time and computer memory required can be reduced. In the angle beam technique, the transmission coefficient from a couplant to a test object becomes complex when the angle of incidence exceeds the critical angle. In order to calculate the transmitted field in this case, an analytic signal is introduced to deal with the complex transmission coefficient. The validity of the model is demonstrated by experiments using an angle beam transducer and a steel block with a side-drilled hole.

An electro-magnetic field resulting from the application of a magnetic or electrical field to a metallic specimen is distorted due to the existence of a crack. The distribution of the magnetic field is changed by this distortion of the electro-magnetic field, and this change in the distribution can be visualized by the magneto-optical (MO) film in the magneto-optical nondestructive testing (NDT) method. The plane of a polarized light beam rotates when the beam is transmitted through an MO film because of the Faraday effect, a kind of magneto-optical effect. In this paper, an NDT simulation technique, which uses not only the Faraday effect, but also the change in the magnetic domains caused by an external magnetic field, the saturated magnetization effect, the effect of the magnetizer, the bias of the magnetic field and the temperature properties, is discussed. The simulation results are verified by comparing them to experiment results.

The potential drop techniques based on electromagnetic induction are classified into induced current focused potential drop (ICFPD) technique and remotely induced current potential drop (RICPD) technique. The possibility of numerical simulation of the techniques is investigated and the applicability of these techniques to the measurement of defects in conductive materials is presented. Finite element analysis (FEA) for the RICPD measurements on the plate specimen containing back wall slits is performed and calculated results by FEA show good agreement with experimental results. Detection limit of the RICPD technique in depth of back wall slits can also be estimated by FEA. Detection and sizing of artificial defects in parent and welded materials are successfully performed by the ICFPD technique. Applicability of these techniques to detection of cracks in field components is investigated, and most of the cracks in the components investigated are successfully detected by the ICFPD and RICPD techniques.