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...
Principles and results of application of specially designed ultrasonic flaw detector for detection and evaluation of parameters of transverse cracks, including under surface damages of rail head, are considered. Using a fairly simple method of multichannel shadow method of ultrasonic inspection and special algorithms for digital signal processing, a flaw detector scanner was developed and introduced, which allows layer-by-layer scanning of a defective section of the rail to visualize a defect in three orthogonal planes. Multiple comparisons of the obtained flaw detection images with the results of forced dolomes show that the measurement errors of the proposed method do not exceed 15%, which is a very high indicator for practice. Proven principles are recommended for use in other industries.
This article shows the possibility of detecting defects in the rail base blades by the method of magnetic flux leakage. Theoretical studies were carried out by modeling and the results were verified experimentally on defect models. As a result, a prototype of a magnetic flaw detector was obtained.
The article is devoted to the question of rail ultrasonic testing confidence. At present there is a range of flaw orientation angles in within which the testing is absent and, therefore such flaws can be lost. To except this drawback the current sound testing scheme in flaw detector railcars is to be supplemented with inclined probes exciting longitudinal wave. Experimental checks using echomethod showed the good results on an October railway section with flaw models and on a loaded Zabaycalskaya railway section. The next step was idea of mirror-shadow method using as well as echomethod by turning of probes towards each other. Envelope analysis of bottom signals allows receiving additional information about flaws: location depth of its center and form. But using of pair of probes was not enough for unambiguous definition of other geometric flaws characteristics. That is why the bottom signal envelope of straight probe was to be analyzed additionally. A mobile (as well removable) searching system of rail checking means has such probe as a rule. In the process of writing the article previously obtained formulas to calculate depth, inclination angle and plane size of revealed flaw were modified. Values changing during testing process are absent now. Algorithm of flaws identification on the basis of bottom signals envelope is given. The approach is confirmed by mathematical modeling in CIVA-UT.
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