The effect of distortion models on characterisation of real defects using ultrasonic arrays

Characterisation of real defects is one of the main challenges in ultrasonic non-destructive testing (NDT), especially for small defects having irregular shapes. Traditional methods such as ultrasonic array imaging are limited by the image resolution, and in this paper, we consider using the scattering matrix which is extractable from the full matrix of transmit–receive array data. We describe a procedure in which the experimental measurements are used to perform characterisation and reveal the associated uncertainties. Moreover, we explore the performance of this characterisation procedure and propose a robust defect characterisation approach. The performance of the proposed approach is studied experimentally, and the sizing errors are small (within 0.09λ or 0.23mm for fatigue cracks at 2.5 MHz, and within 0.38λ or 0.24mm for volumetric defects in an additive manufactured specimen at 10 MHz). In addition, reliable estimation of defect angle/width is achieved.