Immersion echo-method of testing of products with untreated surface

Statistic characteristics of distribution of echo-signal amplitudes and the optimum testing frequency corresponding to its maximum sensitivity depending on the product surface roughness are theoretically investigated. To decrease echo-signal fluctuations it is necessary to use a transformer with possibly largest dimensions of piesoplates, and the testing operational frequency must not exceed the optimum frequency, i. e. the frequency corresponding to the testing sensitivity maximum for the given roughness degree