RU2785302C1 - Ultrasonic method for assessing defects in the rail head and determining the profile of the tread surface - Google Patents

Abstract

FIELD: rail head defects evaluating.

SUBSTANCE: invention is intended for evaluating defects in the rail head and determining the profile of the tread surface. The substance of the invention lies in the fact that in the vicinity of the alleged defect, pairs of mutually directed electroacoustic transducers are installed on the tread surface and on both head surfaces of the rail head, they are moved along the indicated surfaces along the rail head, the rail head is probed, for which ultrasonic signals are emitted by transducers from both head surfaces and they are received by transducers on the tread surface, the boundaries of the defect are fixed by the shadow method, they are jointly analyzed and the dimensions and orientation of the defect are determined, while the excitation and reception of ultrasonic vibrations is carried out by lines of piezoplates placed across the rail head in roller transducers with an elastic shell, the number of piezoplates in the lines is chosen based on the required resolution, the assessment of the internal defect and the calculation of the profile of the rail tread surface is carried out taking into account the signals received by all receiving transducers.

EFFECT: improving the accuracy and productivity of defect assessment in the rail head and determination of the profile of the rail tread surface.

2 cl, 2 dwg

Description

The invention relates to an acoustic type of non-destructive testing and can be used in the control of local sections of railway rails according to the readings of mobile and removable flaw detection tools, during periodic inspection of rail tracks, as well as when planning work to restore the profile of the rail head.

During the operation of the rail track, the rail head undergoes significant loads. It is here that up to 70% of all detected surface and internal defects develop. Microcracks and irregularities can form on the head tread surface, which are sources of dangerous longitudinal and transverse cracks. The current regulatory documentation [1, 2] classifies transverse cracks (codes 21, 24, 26, etc.) in the head as the most dangerous defects that can lead to a sudden brittle fracture of a rail under a moving rolling stock. At the same time, longitudinal cracks at a depth of up to 8 mm from the tread surface, as a rule, develop for a long period and can be eliminated in a planned manner. Therefore, non-destructive assessment of the configuration and parameters of internal defects in the rail head is an urgent task.

During the operation of the rail track, the wear of the tread surface of the rail head can reach up to 10 mm with a violation of the original profile. In order to timely exclude (remove) surface microcracks - the source of many internal defects, as well as to restore the original profile, periodic grinding of the rail head on the way is carried out using rail grinding trains. Obtaining information about the profile of the rail head requires the use of methods and devices based on mechanical, eddy current and optoelectronic principles [3-7].

Given the relevance of the issues of assessing defects and the profile of the rail head, several technical solutions based on the use of ultrasonic (US) vibrations have been proposed. The disadvantages of the known technical solutions [8-12] are the low accuracy and complexity of the measurement procedure. This is mainly due to the use of the rail tread surface as the input plane for ultrasonic vibrations. In this case, the echo signals from many cracks located near the rail head rolling surface fall into the insensitivity zone (“dead zone”) of the ultrasonic control.

Possible input surfaces for ultrasonic vibrations could be the head surfaces of the rail head, which are not exposed to the wheels of the rolling stock and retain their original profile during the operation of the rails in transit. However, the roughness (non-smoothness) of these surfaces prevents stable input of ultrasonic vibrations during scanning (moving by sliding over the surface) with electroacoustic transducers (EAC). Thus, the main reason for ignoring the stable (non-wearing) head faces of the rail head for input/reception of ultrasonic vibrations in order to detect internal defects by known technical solutions [9, 13, 14] is the difficulty of ensuring stable acoustic contact during movement (scanning) by sliding the EAP over these surfaces.

The closest technical solution adopted for the prototype is an ultrasonic method for assessing the wear of the rail head and the depth of the defect [15], which consists in installing radiating EAPs on the head faces of the rail head, and receiving transducers on the tread surface, probing the rail head, moving transducer pairs along the specified surfaces along the rails, detection of the defect boundary line by the shadow method, their joint analysis and determination of the size and location of the defect, as well as in measuring the propagation time of the ultrasonic signal and calculating the height of the rail head along the probing line. When a defect is detected, it is provided to receive a signal reflected from the defect, measure the propagation time of the ultrasonic signal and calculate the depth of the defect in the probing plane.

The disadvantages of the known technical solution are the low accuracy and performance of control, as well as a limited scope.

The task to be solved by the claimed invention is to create a method for estimating the configuration and dimensions of internal defects of the rail head and simultaneously measuring the profile parameters of the rail head by ultrasonic method.

The technical result of the invention is to increase the accuracy and productivity of measuring the parameters of defects, and to expand the scope of the method for monitoring the rail head.

The technical result is ensured by the fact that in the ultrasonic method for assessing a defect in the rail head and determining the profile of the tread surface, which consists in the fact that in the vicinity of the alleged defect, pairs of mutually directed electroacoustic transducers are installed on the tread surface and on both head surfaces of the rail head, and they are moved along the indicated surfaces along the rail head, the rail head is probed, for which ultrasonic signals are emitted by transducers from both head surfaces and received by transducers on the tread surface, the defect boundaries are fixed by the shadow method, they are jointly analyzed and the size and orientation of the defect are determined, and the excitation and reception of ultrasonic vibrations is carried out with rulers piezoelectric plates placed across the rail head in roller transducers with an elastic shell, the number of piezoelectric plates in the lines is selected based on the required resolution, an assessment of the internal defect and the calculation The study of the profile of the rail rolling surface is carried out taking into account the signals received by all receiving transducers.

Additionally, the propagation time of ultrasonic vibrations in the transition layers between the emitters/receivers of ultrasonic vibrations and the surfaces of the rail head is determined on a rail head with known dimensions, and the obtained time values are used to calculate the rail tread surface profile and defect parameters.

Significant differences between the proposed method are:

1. Implementation of the introduction of ultrasonic vibrations with the help of lines of piezoplates placed in roller transducers provides a more reliable and stable acoustic contact, especially along the subhead surface. In the prototype, the issues of providing acoustic contact on uneven surfaces are not considered. Scanning using transducer sliding systems (in the prototype [15]) over uneven, rough surfaces inevitably leads to noticeable fluctuations of both through signals on defect-free sections of the rail head and the amplitudes of echo signals from possible defects. When sounding with the proposed rolling systems (rollers), stable and high-quality acoustic contact is ensured even on uneven surfaces.

2. Simultaneous scoring of the rail head section in several probing planes due to the use of piezoplate rulers installed on the head surfaces and the rail tread surface makes it possible to more reliably and quickly assess internal defects and measure the rail head profile. The prototype provides for the sounding of certain sections by single pairs of piezoelectric plates from each surface only along the probing line, which does not provide the necessary information content and reliability of control. In the prototype, the possible scanning across the section of the rail head by discrete displacement of pairs of EAP, sharply reduces the performance of the control and limits the scope, because does not allow obtaining correct information about the parameters (profile) of the rail head tread surface and the dimensions of internal defects.

3. The propagation time of ultrasonic signals is measured taking into account the delays in the transition layers (in the acoustic fluid inside the roller, in the thickness of the roller shell and in the contact lubricant layer) between the emitters / receivers of ultrasonic vibrations and the surfaces of the rail head, which makes it possible to obtain more accurate values of the measured parameters tread surface and defect depth. In the prototype, the issues of accounting for the delay times of ultrasonic vibrations in the transition layers are not considered.

4. The use of roller converters, as practice shows, requires 30-50% less contact lubrication than when using sliding systems. This factor is especially important when monitoring local sections of the rail track according to the indications of mobile and removable flaw detection tools, because they are checked mainly by hand and the required amount of lubricant is included in the portable flaw detector kit.

The implementation of the proposed method is illustrated by the following figures:

Fig. 1 - Placement of roller transducers on the controlled rail,

where:

1 - head of the controlled rail;

2 and 3 - subhead surfaces and the rolling surface of the rail head, respectively;

4 _L and 4 _R - carriages with roller converters on the right (Right) and left (Left) head surfaces of the rail head;

5 - carriage with roller transducers on the tread surface of the rail head;

6 - piezoplates inside roller transducers.

Fig. 2 - Schemes of control of the rail head when scoring rail sections with longitudinal and transverse internal cracks (defects), where:

A, B and C and co-directed C', B' and A' rollers with transducers on the respective surfaces of the rail head 1 (shown in one longitudinal section of the rail head);

Angles α ₁ and α ₂ - angles of entry of ultrasonic vibrations in the plane of sounding;

D _L and D _T - longitudinal or transverse crack inside the rail head.

The proposed method is implemented as follows. In the zone of the alleged internal defect on the tread surface 3 and on the head surfaces 2 of the head 1 of the rail, carriages 4 _L , 4 _R and 5 with roller converters are installed.

Roller transducers are known from the prior art [16-20] and are rollers rotating on an axis (small wheels), having a shell in the form of an elastic membrane and filled with a sound-conducting liquid. Inside the roller, on the axis of its rotation, electroacoustic transducers are fixed (in this case, a line of piezoplates 6) for input/reception of ultrasonic vibrations into the rail (and from the rail) through the contact patch of the elastic membrane of the roller with the rail surface.

In the claimed method, the lower head carriages 4 _L , 4 _R (for example, in the form of rectangular frames) contain at least three roller EAP (Fig. 2 rollers A, B and C). The width a of each roller is consistent with the straight section of the head surface (Fig. 1), and the diameter 2R is limited by the implemented sounding scheme and design considerations. Inside the roller, i piezoplates 6 are placed, which input ultrasonic vibrations perpendicular (normally) to the head surfaces relative to the cross section of the rail head. In the longitudinal section of the rail, one of the rollers (roller B in Fig. 2) emits ultrasonic vibrations in the perpendicular direction, the other rollers at opposite oblique angles +α and -α (rollers A and C in Fig. 2). In general, the values of these angles may differ from each other. The number i of piezoplates 6 in each roller is determined by the size of the head surface in cross section and the size (diameter) of the piezoplates selected from the required resolution when evaluating the defective section.

The upper carriage 5 with roller transducers C', B' and A' contains a ruler with piezoelectric plates 6 directed to the corresponding plates of the lower head rollers in the carriages 4 _L and 4 _R , and contains at least N>2i+1 piezoelectric plates. In addition to the piezoelectric plates n _I -n _i co-directional with the piezoelectric plates in the head rollers (Fig. 1). Additionally, in the rollers on the tread surface, central multidirectional piezoplates can be installed in the area of the longitudinal axis of the rail head. A possible variant of the orientation of the central plates along the longitudinal axis of the rail is shown in Fig. 1 and 2, where in the central roller B' (Fig. 2) there is a plate emitting / receiving in the vertical direction (down, or at an angle of 0 degrees), and along the edges of the carriage (in Fig. 2 rollers A' and C') - plates on the same axis, directed oppositely at angles α. With the help of these additional piezoelectric plates 6, due to multiple reflections in the surface layer (between the tread surface 3 and the longitudinal crack D _L ), it is possible to more clearly identify difficult-to-detect longitudinal cracks and delaminations of the rail head, which occur at shallow depths. In the presence of a deep-seated longitudinal crack, the depth of its occurrence can be determined from the time position of the echo signals from the crack plane.

Evaluation of an internal defect and determination of its image (longitudinal D _L or transverse crack D _T ) is as follows. The ultrasonic vibrations passed through the metal of the rail head 1 are received by co-directional piezoelectric plates in the corresponding rollers on the rail tread surface. In FIG. 2, roller A, placed on the head surface, emits ultrasonic vibrations through the rail head, and they arrive at roller A'. The ultrasonic vibrations emitted from roller B are transmitted to roller B', and from roller C to C'. In the process of scanning (along the rail) of the rail head 1, a system of three carriages 4 _R , 4 _L and 5 with roller transducers produces layer-by-layer (in vertically inclined probing planes) sounding of the rail head section. In this case, the controlled rail acts as a kind of guide for the carriages.

Pressing the rollers to the scanned surfaces and ensuring stable acoustic contact by supplying a contact lubricant (or gel for ultrasonic testing) to the scanned surfaces is carried out by a special device (not shown in the figure).

In the process of scanning the head, the roller systems in the carriages are rolled along the rail. An internal crack of any orientation (D _L or D _T ) will shield the ultrasonic rays emitted from the head rollers A, B and C. On the lines of the piezoelectric plates, the rollers C', B' and A' of the upper carriage 5 will gradually decrease (up to complete disappearance) level of received end-to-end signals. The coordinates of the attenuation of the through signals along the length of the rail are fixed by the processor of the ultrasonic flaw detector, taking into account the readings of the displacement sensor (not shown in the figure). Based on the parameters of these weakenings, based on acoustic and geometric constructions, by known methods [9 and 15], the profile of the internal defect of the rail head is calculated, which, with appropriate processing, can be represented as a 3D image on the monitor of a multichannel flaw detector with a displacement sensor.

To obtain a detailed image (outline) of an internal defect, sounding of the head 1 is performed in several mutually parallel longitudinally inclined planes using i piezoelectric plates installed in each roller (see Fig. 1). Due to the presence of many (N>2i+1) channels, one scan (synchronous rolling of the carriages along the rail) makes it possible to sound out most of the head section, which in practice is sufficient to form an unambiguous conclusion about the presence or absence of an internal defect exceeding the critical size. Compared with the prototype, this result does not depend on the degree of wear of the side surfaces of the head and has a greater (i times) performance.

Determination of the profile of the rail tread surface is carried out in front of or behind the defective section (on the defect-free section), and, if necessary, on any defect-free section of the rail track.

In the presence of end-to-end signals on all elements of the ruler of the roller B', measure their time positions t _{rms i} relative to the moments of radiation and, according to the expression

h _gi \u003d c [t _{well i} - (t _mon + t _pv )],

calculate the actual height h _gi of the head and the corresponding profile of the rolling surface of the rail head, taking into account the position of the signals on all piezoelectric plates 6 of the ruler in the roller, where:

t _mon and t _pv - the delay times of ultrasonic vibrations in the design of the rollers (total travel time through the acoustic fluid in the roller, the thickness of the roller shell) and in the contact lubricant;

c is the speed of ultrasonic vibrations in the metal of the rails (for longitudinal waves, about 5900 m/s).

Based on the obtained heights of the rail head in each probing plane, the number of which is determined by the number of 2i co-directional pairs of piezoplates 6 on the head surfaces 2 and the tread surface 3, the actual profile of the rail head 1 is constructed.

The contact underhead surface of the widely used rails of the P65 type is about 20 mm. When using industrially produced piezoelectric plates with a diameter of 4 mm, in roller B (central in carriage 4r and, similarly, in carriage 4 _L ), i (up to 5 pcs.) adjacent plates 6 can be placed on the acoustic ruler (Fig. 2). To measure the actual profile of the rail head, it is sufficient to measure the time positions of the through pulses on the piezoelectric plates of the roller B' acoustic ruler, which receive ultrasonic vibrations from the piezoelectric plates of the rollers B from both subhead surfaces of the rail head (Fig. 1).

In this example, during the implementation of the method, it is possible to determine 5 points of the rail tread surface on both sides relative to the longitudinal vertical axis of the rail, along which (10 profile points in total) it is possible to build a line of the actual profile of the head tread surface, which is quite enough for the practice of periodic operational inspections of the condition rail track.

If it is necessary to evaluate the profile of the rail head outside the zone of local defects, measurements are made, as a rule (depending on the state of the head), no more than every 25-100 m.

With the help of the proposed technical solution, it is possible to measure the depth of local slippage on the rails (from the wheels of rolling stock) and collapses (code defects 46.3-4 according to [2]) in the zone of welded joints, which further expands the scope of the method.

Preliminary accounting of times t _mon and t _PV in transition layers is carried out on a fragment of a rail with known dimensions of the head (for example, determined using mechanical meters) or on a specially made sample. A possible change in the thickness of the elastic sound-conducting shell (membrane) of the rollers when they are pressed against the input surfaces of ultrasonic vibrations is also taken into account, which further increases the accuracy of measuring the desired parameters. Accounting for these parameters of the system of electroacoustic transducers allows you to determine the dimensions of the height of the head 1 of the rail in the measured sections with the required accuracy. The subsequent determination of the degree of wear of the head is carried out relative to the profile of the new rail.

Thus, the application of the proposed method makes it possible to increase the accuracy and reliability of measurements when assessing internal defects in the rail head and determining the profile of the rail tread surface. The method greatly increases the inspection performance and has an extended scope (evaluation of internal defects, determination of the actual profile of the tread surface and the degree of wear of the head, as well as determining the depth of crushing and slippage on the surface). Based on the information received, a reasonable decision can be made on the advisability of repairing rail sections or on periodic observation (monitoring) of the growth of defects until they reach critical sizes.

Sources of information

1. GOST R 51685-2013. Railway rails. General specifications.

2. Instruction "Defects of rails. Classification, catalog and parameters of defective and sharply defective rails". JSC "Russian Railways" No. 2499 r dated 10/23/2014.

3. RU 2162120.

4. RU 2204803.

5. RU 2513338.

6. RU 2489291.

7. RU 2708520.

8.JP 11337529.

9. RU 2340495.

10. RU 2613574.

11. RU 2545493.

12. RU 2060493.

13. US 2013/0152691.

14. EP 2277037.

15. RU 2466386.

16.RU 89235.

17. RU 2677124.

18. US 5419196.

19. RU 2611709.

20. RU 2504767.

Claims (2)

1. An ultrasonic method for assessing defects in the rail head and determining the profile of the tread surface, which consists in the fact that in the vicinity of the alleged defect, pairs of mutually directed electro-acoustic transducers are installed on the tread surface and on both subhead surfaces of the rail head, they are moved along the specified surfaces along the rail head, they are probed rail head, for which ultrasonic signals are emitted by transducers from both head surfaces and received by transducers on the tread surface, the defect boundaries are fixed by the shadow method, they are jointly analyzed and the size and orientation of the defect are determined, characterized in that the excitation and reception of ultrasonic vibrations is carried out by lines of piezoplates, placed across the rail head in roller transducers with an elastic shell, the number of piezoelectric plates in the lines is selected based on the required resolution, the assessment of the internal defect and the calculation of the surface profile of the rails are produced taking into account the signals received by all receiving transducers. 2. An ultrasonic method for assessing defects in the rail head and determining the profile of the tread surface according to claim 1, characterized in that the determination of the propagation time of ultrasonic vibrations in the transition layers between the emitters / receivers of ultrasonic vibrations and the surfaces of the rail head is carried out on a rail head with known dimensions and obtained the time values are used in calculating the rail tread surface profile and defect parameters.

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