APPLICATION OF CORRECTION FACTORS TO THE AMPLITUDE OF SIGNALS REFLECTED FROM DEFECT SIMULATORS IN ULTRASONIC NON-DESTRUCTIVE TESTING REFERENCE BLOCKS

Abstract

Ultrasonic non-destructive testing (UT NDT) is widely used for assessing the technical condition of critical engineering structures, with the amplitude-based method remaining one of the principal approaches for defect sizing. However, a significant limitation of this method is the poor reproducibility of echo amplitudes obtained from nominally identical reflectors in calibration and reference blocks, which may lead to deviations of 4 – 10 dB and substantial errors in defect size estimation. This paper proposes an analytical approach for compensating such discrepancies by introducing a correction factor based on the comparison of signal amplitudes reflected from a flat-bottom hole and a quasi-infinite surface. The model is formulated on the basis of acoustic path equations for the far field, taking into account the geometric parameters of the transducer and reflector, ultrasonic frequency, and wave propagation velocity in the material. Measurement uncertainty was evaluated in accordance with the GUM approach. The results demonstrate that the proposed correction reduces amplitude dispersion to approximately 1 – 1,3 dB, significantly improving the reproducibility and reliability of inspection results. The proposed approach can be applied in calibration procedures, metrological certification, and digital ultrasonic testing systems.