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The main factors that reduce the quality of non-destructive testing of rails during high-speed scanning are considered. The most significant factors are the quality and volume of obtaining primary information about the condition of the monitored rails. It is shown that, at high-speed (up to 120 km/h) control, the compression of the defect location zone is clearly manifested and the length of the areas with acoustic contact violations increases. Analysis of real flaw diagrams of diagnostic complexes shows that with an increase in the scanning speed, the length of the location zone even from such large reflectors in the rails, such as bolt holes, significantly decreases. The average length of the instability zone of the bottom signal over the welded joints of the rails also increases significantly. The compression of the location zones of the reflectors can be compensated by expanding the aperture of the ultrasonic transducers. Improving the quality of the acoustic contact requires further improvement of the design of the search system and the systems for supplying the contacting liquid to the transducers, depending on the scanning speed. The Magnetic Flux Leakage(MFL) method can effectively detect defects in the rail head up to 20 mm deep at high speeds. Mathematical modeling of the magnetic flux in the controlled rails is performed. This allows us to start creating a new rail magnetization system with an increased interpole distance for high speeds. The introduction of modern methods for processing a significant flow of flaw detection information using neural networks requires the formation of a large sample base of training signals from real defects in different sections of rails. This is a complex task in its own right. For the first time, the issues of checking the operability of flaw detection devices in real control conditions are raised. Testing of ultrasonic equipment at high speeds is proposed to be carried out with the help of special electronic-acoustic simulators of defects. They are installed on different surfaces of the rails on which the diagnostic complexes pass. Operational quality control of ultrasonic rail inspection can be evaluated by statistical analysis of signal parameters from structural elements (bolt holes). The choice between the monitoring performance and the required reliability of detecting rail defects must be made based on the results of real passes of diagnostic complexes at operating scanning speeds.

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Optimization of the parameters of schemes using multichannel ultrasonic flaw detectors for sonic testing of rails (sonic test schemes), as well as development of algorithms for processing test signals, are considered. The efficiency of the RAIL-3D computer code proposed for the 3D simulation of the propagation and formation of echo signals during ultrasonic testing is tested by comparing real signals and simulation results for a CB-2 calibration block. The comparison is performed for the complex conditions under which rails are tested. The code can also be used for simulating signals of ultrasonic nondestructive testing in other metal products. BACKGROUND INFORMATION: MAIN PROBLEMSSignificant changes have been observed recently in nondestructive testing of track rails in situ [1]. Flaw detecting railcars and motor-rail cars with on-board computers may concurrently conduct both ultrasonic and magnetic testing [2]. Detachable flaw-detection carts of a new generation that are equipped with builtin microprocessors provide continuous recording of signals for all test channels [3,4].To ensure reliable detection of flaws with different orientations in rails, ultrasonic vibrations are inputted from a railhead's roll surface at different angles. A set of angle and normal piezoelectric probes (PEPs) installed in the search system of a flaw-detection device creates a so-called sonic test scheme for rail cross sections. Up to ten different sonic test schemes are currently used in mobile and detachable devices for the detection of flaws in rails. These schemes, which differ in the number of used PEPs and the methods applied for ultrasonic testing, are characterized by different potential technological efficiencies [5].The most advanced sonic test schemes are based on original probes that apply the newly developed mirror through-transmission method to detect flaws in rails. The probes create a two-beam directivity characteristic [6,7]. As a result of implementation of the new methods, the number of fractures induced by flaws in rails has been decreased significantly.However, some problems in NDT of rails remain unresolved. In addition, some test parameters need to be detailed and adjusted. The following is a list of urgent tasks in NDT of rails:(1) Analysis of available schemes for sonic testing of rail cross sections in order to obtain information about potential capacities for detecting flaws and optimization of the parameters of the testing schemes' elements for the further increase of the efficiency of rail testing.(2) Development of concepts and algorithms for recognition of signals in the background of noise and reflexes from structural reflectors to automate the process of decoding test signals.Awareness of disadvantages of sonic test schemes (for example, their dead zones, i.e., areas in a rail that are fully or partly missed by a particular sonic test scheme) allows improvement of the situation in the future by amending the available schemes or developing new ones and, thus positively affecting the test efficiency and...