Influence of acoustic transparency of surface contact layer on flaw detectability in ultrasonic testing

On the basis of extensive experiments, conducted on a representative sample of specimens with different kinds of autocorrelated function of surface profile, the following dependencies were obtained: correlative links between parameters of regular and stochastic unevenness and absorption coefficient in the coupling layer for several ultrasonic transducers produced by firms such as Krautkramer; Sonatest, Tokimek, Volna and others; correlative links between height parameters of unevenness and the amplitude of an auxiliary signal from the SRC-probe; correlative links between absorption coefficient in coupling layer for ultrasonic transducers (normal transducers and angle transducers) and the amplitude of an auxiliary signal from the SRC-probe. On this scientific basis, the following nomograms were plotted and generalised: mathematical dependence of absorption coefficient in the coupling layer of an ultrasonic transducer on the geometrical size of its working surface, angle of ultrasound incidence, frequency, surface unevenness expressed in parameter Rz and amplitude of special signal from SRC-probe. This allowed us to develop a fundamentally new method (technology) of ultrasonic testing named the SRC-technique (Surface-Roughness-Correction technique).