Since JIS Z 3110:2017 “Non-destructive testing of welded joints-Methods of radiographic testing for X- and gamma-ray techniques with digital detectors” was established and digital radiographic testing (RT) has been increasingly applied. When replacing conventional film RT with digital RT, it needs to be judged carefully to meet each standard requirement as each standard is different. When replacing film with an imaging plate using X-ray, ¹⁹²Ir, and ⁶⁰Co radiation sources, the conventional geometrical conditions of film RT must comply with JIS Z 3110:2017.

A post-processing array imaging method using full waveforms sampling and processing (FSAP) has been proposed in ultrasonic non-destructive testing. This makes use of scattered waves, measured by two-element combinations as a transmitter and a receiver, to synthesize high amplitude beams for any points in an inspection area. In this study, the FSAP method was applied to the inspection of asphalt pavement. Here, we considered the two-dimensional imaging using an ultrasonic array transducer with 75kHz center frequency, which was designed based on a simulation for the radiated wave field. Since the asphalt pavement has multi-layer structures, the FSAP algorithm needs to be modified to select an appropriate beam path due to the diffraction of the ultrasonic wave at the interface. We validated the performance of the proposed methods by measuring the longitudinal scattered waves in asphalt specimens. Artificial defects at the layer interface and the base material were clearly reconstructed in real-time using graphic processing unit computing.