Pozniakova M. Ultrasonic method and means for detecting internal defects of railway axes

In the dissertation work, a relevant scientific and practical problem was solved - the development of a new method and means for providing ultrasonic immersion testing of railway axles with increased internal defects of a minimum size detection sensitivity through the use of pulse packets of given frequency and duration. An analytical review and analysis of modern means and methods of non-destructive testing and diagnostics of railway axles and their blanks has been carried out. A physical and mathematical model of testing has been developed and a theoretical calculation of the ultrasound path has been performed. An unambiguous relationship has been established between the size of the defect and the frequency of ultrasonic oscillations. It has been theoretically and experimentally proven that the sensitivity of ultrasonic immersion control of railway axles can be increased by feeding the piezoelectric transducer (probe) with packet current pulses of a given filling frequency and temporal duration. It was found that in order to ensure sufficient sensitivity of ultrasonic immersion testing of railway axles (detection of internal defects of effective size that corresponds to a 1 mm diameter flat-bottomed reflector), the ultrasonic testing frequency must be set in the interval 4.2 ... 4.5 MHz, and the pulse temporal duration to 6 ... 8 filling periods of the specified frequency. A method of ultrasonic immersion testing has been developed, which includes immersing a control sample with a model of a defect of a given size into immersion liquid, irradiating a defect in the sample using a singular probe and a singular ultrasonic pulse, which consists of several high-frequency periods, receiving a pulse reflected by the defect with a second probe, adjusting the frequency and duration of the irradiating ultrasonic pulse until obtaining the maximum amplitude of the pulse reflected by the defect, and conducting defectoscopy with the specified parameters of the irradiating pulse.