Introduction. The work aim was to carry out experimental studies of dual-frequency method reliability for defect type determination at manual ultrasonic testing of railway rolling stock elements. Method. The method of discontinuity type determination includes: measuring amplitude characteristics of echo signals from the detected defect on the frequency of 2.5 and 5.0 MHz; calculation a defect form-factor; comparing the form-factor with the certain limit values, one of which corresponds to a planar defect and the other corresponds to a volume defect. The defect is considered planar/volume, if its form-factor differs from the appropriate limit value by no more than 30%. The method gives an opportunity to determine types for both point and extensive defects. For the experiment a sample was manufactured, in which various artificial reflectors of different types and dimensions were made. The type of each reflector was determined with dual-frequency method. The relative error and reliability of type determination were calculated. Results. Experimental studies have shown that reliability of defect type determination with dual-frequency method is quite high. The average accuracy of point defect determination has been 97,389%; extensive defect determination has been 93,588%.
UT, technical diagnostics, pulse echo techniques, flaw detection, dual-frequency method, form-factor, discontinuity limit value
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