On efficiency evaluation of the ultrasonic amplitude control of large-grain materials

The scattering of ultrasound is experimentally studied in echo-defectoscopy of pipes of diameter 560 x 32 mm made of type Kh18N9T steel. A priori probabilities have been analysed of erroneous estimates of the equivalent sizes of the defects for the generalized Rayleigh law. The possibilities have been considered for increasing the reliability of detecting the defects nd estimating their sizes on the basis of statistical treatment of signals. In the presence of correlated (in particular, structural) noises, the method of averaging the signal amplitudes, appears to be quite promising. The calculated average value of the amplitude < A > according to the general set of random signals yields a monotonically varying displaced and overstated estimate of the equivalent area S of the defect (with an accuracy to 10%, < A > = 0.35< A1 > + S, where A1 is the average value of the noise amplitude). The dependences of the average values of the first and second orders of the amplitudes of asymmetrically fluctuating signals on the equivalent area of the defect have been plotted