RU127703U1 - MAGNETIC DEFECTOSCOPE - SPEED METER - Google Patents

Abstract

The inventive magnetic flaw detector speed meter relates to a device for measuring the speed of moving objects by magnetic means and can be used in rail cars - flaw detectors.

A magnetic flaw detector-speed meter contains a reference speed meter mounted on a rail mobile vehicle, a path magnetization system, at least two magnetic field sensors installed at known distances from each other, and a processing unit whose outputs are the meter’s outputs and the inputs are connected to magnetic sensors field and a reference speed meter and differs in that the path magnetization system is made in the form of two magnets mounted on the axles of the wheelsets of the movable means. The magnetization system can be powered by both direct and alternating current.

The inventive magnetic flaw detector-speed meter, thanks to the proposed magnetization scheme, is able to detect with good quality both defects in the rail and the speed of the flaw detector.

Description

The inventive magnetic flaw detector - speed meter relates to a device for measuring the speed of moving objects using magnetic means and can be mainly used in rail cars - flaw detectors.

Various means are used for flaw detection of a rail track: magnetodynamic, eddy current, subsurface radar sounding, optical, etc. Magnetodynamic methods can work in all climatic zones under any weather conditions, and their control results do not depend on the contamination of the rails. These circumstances make such methods the only applicable in winter conditions. In addition, magnetodynamic methods have a high repeatability of signals, which makes it possible to observe (monitor) the development of individual defects.

Flaw detection tools are installed in various parts of flaw detectors. High quality of detection and assessment of defects can be achieved by jointly analyzing the results of all measuring channels [1], [2]. For such an analysis, it is required to know the relative position of the respective meters and the speed of their movement with high accuracy.

A variety of methods and means for measuring the speed of rail vehicles are known.

The global navigation satellite system allows you to determine the parameters of the movement of rail facilities with sufficient accuracy to solve logistics problems, but is not always accessible (tunnels) and not accurate enough for flaw detection.

Odometers (tachometers) operating “from the wheel”, due to slipping and wear of the wheels, also have a relatively high error.

Optical measuring instruments are exposed to environmental factors.

The accuracy of radar is affected by snow and ice.

Installation on rails or near them of reference elements (magnets), for example, [3], and reading them with sensors of the flaw detector car is associated with significant material costs.

Known magnetodynamic flaw detectors containing a path magnetization system and a magnetic field sensor. In a flaw detector [4], the magnetization system is made in the form of a magnet located on the axis of the wheel. In the flaw detection complex AVIKON-03 [5], two magnetization coils are located on the axles of the wheelsets. The result is a closed magnetic flux, figure 1, without air gaps and corresponding losses, allowing reliable detection of internal and surface defects in the rails. In addition, this also preserves the scattering field with the possibility of detecting structural elements of the rail track. Such a magnetization system makes it possible to obtain magnetic induction in the rail of at least 1 T at a consumed electric power of only about 2 kW.

In the considered sources, magnets are used only for solving flaw detection problems, and the problem of determining the speed is not considered.

Closest to the claimed one is a magnetic flaw detector-speed meter [6], comprising a reference speed meter mounted on a rail mobile vehicle, a path magnetization system, at least two magnetic field sensors installed at known distances from each other, and a processing unit whose outputs are outputs a meter, and the inputs are connected to magnetic field sensors and a reference speed meter.

The device [6] assumes the presence of two independent pairs: a magnetic field sensor coil installed at a known distance. The speed is determined by calculating the correlation between the signals received from the sensors. The maximum correlation occurs if the signals from the sensors relate to the same object. In addition, according to the authors, the analysis of signals from magnetic field sensors makes it possible to detect large defects in the rail, for example, kinks. Thus, the device [6] can also be used as a flaw detector.

The disadvantage of the device [6] is the low quality of the flaw detection associated with the proposed design of the magnetization system. This disadvantage is due to the fact that the device [6] was developed as a speed meter, and flaw detection properties were a by-product. In the claimed utility model, a full-fledged flaw detector is complemented by a speed measurement function.

The magnetic flux generated by the coil of the magnetization system is distributed over the scattering field, covering the entire space around the rail, including the structural elements of the rail fastening (covers, linings, switches, couplers, bolts, etc.) and to the field created in rail. The design of the magnetization system [6] implies the presence of coils, which, according to the requirements of operational safety, should be located at a distance from the rail. This approach causes the following problems [5]. The air gap significantly weakens the magnetic flux in the rail, which does not allow reliable detection of defects. With an increase in the speed of the movable means and (or) an increase in the power of the magnets, the eddy currents increase and make flaw detection even more difficult. In addition, the prototype uses a low-frequency alternating electromagnetic field, generating eddy currents in the rail. As a result, the device [6] is capable of detecting only rail breaks, but does not allow detecting defects at an early stage of development.

The problem solved by the claimed magnetic flaw detector-speed meter, is to ensure high quality, as a flaw detector, and autonomous speed measurement by cheap means.

A significant difference of the inventive magnetic flaw detector is a magnetization system made in the form of two magnets mounted on the axles of the wheelsets of the movable means. This method of implementation of the magnetization system allows to ensure good magnetization of the rail, and due to this, confidently detect defects in the depth of the rail. In this case, the scattering field is maintained, which ensures the detection of structural elements of the rail track. Structural elements of the path and defects make it possible to determine the speed of the flaw detector with good accuracy. These benefits are achieved with moderate energy costs.

In the prototype, the air gap between the magnetizing coils and the rail reduces the field intensity, the excitation by alternating current causes eddy currents, especially at high speeds, which reduces the possibility of flaw detection.

The inventive utility model is illustrated by the following graphic materials.

Figure 1 - design of a magnetization system.

Figure 2 is a structural diagram of a magnetic flaw detector-speed meter, where:

1. Rail.

2. Reference speed meter.

3. The magnetic field sensor.

4. Processing unit.

5. The outputs of the flaw detector D - speed meter V.

6. Wheel pairs.

7. Magnets.

8. Magnetic flux in the rail.

9. Rail weld

10. Rail linings.

11. Rail lining.

Figure 3 - signals from the magnetic field sensor, where:

12. - Signals from rail pads 10.

13. The signal from the beginning of the rail 11.

14. The signal from the weld ("defect").

15. The signal from the end of the rail 11.

Rail 1 is an object of measurement.

The reference speed meter 2 is intended for the approximate determination of the speed V _{o of the} flaw detector. As such a device, a conventional “off-wheel” odometer or global satellite navigation system can be used. A reference meter is especially needed at zero and close speeds.

Magnetic field sensor 3. In this case, the sensors are located on the rail near the wheels. As sensors can be used induction, magnetoresistive, flux-gate transducers or Hall sensors. The measurement accuracy of these transducers is different and depends on the speed, so a combination of transducers can be used, switched depending on the speed of the flaw detector [7].

Processing unit 4 is designed to detect defects in the rail 1 and calculate the speed of the flaw detector by comparing the signals received by the sensors 3. Processing unit 4 is a computer with analog-to-digital converters at the inputs from the sensors 3.

The outputs of the flaw detector - speed meter 5 contain information about the speed of the flaw detector V and the detected defects D.

Wheel pairs 5, as a rule, belong to one cart.

Magnets 7 are designed to create a magnetic flux 8 in the rail 1 and the surrounding space. Permanent magnets or coils excited by direct or alternating current can be used as magnets.

Rail 9 defect, in which case in this case a welded joint is considered.

Rail linings 10 and linings 11 are structural elements for fastening the rail and are well detected on magnetograms, Fig.3.

Consider the work of the inventive magnetic flaw detector - speed meter.

A magnetic flaw detector - a speed meter is mounted on rails 1. A magnetization system consisting of coils 7 mounted on wheelsets 6 creates a magnetic flux in rail 1 8. In this case, direct current excitation is considered. The flaw detector moves along the rail at a speed whose approximate value V _о is determined by the reference speed meter 2. Magnetic field sensors 3 receive signals from the rail and the surrounding space. The type of signals is shown in figure 3. Signals 12 are clearly visible on the graph — from rail linings 10, signal 13 — from the beginning of rail plate 11, signal 14 — from the weld (“defect”) 9, signal 15 — from the end of rail plate 11. These signals can be used to measure flaw detector speeds. The experiments showed that the signals from the two sensors 3 of the flaw detector are very similar, both in shape and in amplitude (signals A and B are shifted for clarity), Fig. 3, but are separated in time due to the distance L between the sensors. Good repeatability of the measurement results obtained in different sessions was also noticed. This allows you to save the measurement results obtained in one session and compare them with new results in another session. The signals from the magnetic field sensors 3 in the processing unit 4 are digitized by an analog-to-digital converter with a selected period T. This period can vary depending on the magnitude of the speed V _о received from the reference meter 2.

Consider methods for detecting defects D and calculating the speed V of the flaw detector in processing unit 4. Let S _i (iT) and S ₂ (iT) be signals from sensors 3.

For flaw detection tasks, a single signal S ₁ (iT) is sufficient. Detection of signals from defects D in processing unit 4 can be performed by known methods — by filtering, peak detection, comparing signals with a library of typical defects, etc.

. Сопоставив сигналы S₁(iT) и S₂(iT) на этих участках путем выделения максимальных амплитуд, или, проведя корреляционный анализ этих сигналов, можно определить реальное расстояние к между сигналами в отсчетах, а по нему определить реальную скорость дефектоскопаTo determine the speed of the flaw detector V, it is necessary to detect sections of the signals S ₁ (iT) and S ₂ (iT) related to the same object 12, 13, 14 or 15 - Figure 3, given that the approximate distance between the sensors 3, expressed in readings is:

. By comparing the signals S ₁ (iT) and S ₂ (iT) in these areas by highlighting the maximum amplitudes, or by performing a correlation analysis of these signals, we can determine the real distance to between the signals in the samples and determine the real speed of the flaw detector from it

.

.

In the correlation analysis, in order to determine the value of k in the above formula, it is necessary to find the value of m at which the maximum correlation coefficient K is achieved with the selected correlation window n = (- a , a ):

.

.

Denoting the found value m = m _max , we finally obtain

.

.

Thus, the inventive magnetic flaw detector-speed meter, thanks to the proposed magnetization scheme, is able to detect defects and the speed of the flaw detector with good quality.

Information sources:

1. Patent RU 2446971.

2. Patent RU 2227911.

3. Patent US 2010266005.

4. Lyusyuk B.C., Bugaenko V.M. Damage to rails and their diagnosis. M.: IKC "Akademkniga", 2006. 638 p. pg. 454-446.

5. Markov A.A., Antipov A.G. Magnetodynamic method of rail monitoring. // In the world of non-destructive testing. 2012, - No. 3 (57). S.66-71.

6. Patent US 5825177.

7. Patent RU 2310836.

Claims (1)

A magnetic flaw detector is a speed meter, which contains a reference speed meter installed on a rail mobile vehicle, a path magnetization system, at least two magnetic field sensors installed at known distances from each other, and a processing unit whose outputs are the meter’s outputs and the inputs are connected to magnetic sensors field and a reference speed meter, characterized in that the path magnetization system is made in the form of two magnets mounted on the axles of the wheelsets of the movable means.

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