RU152257U1 - ULTRASONIC DEFECTOSCOPE FOR CONTROL BY THE SHADOW DIAGRAM WITH DIFFERENT COMPENSATION OF THE INFLUENCE OF INTERFERRING FACTORS WHEN SCANNING - Google Patents

Abstract

1. An ultrasonic flaw detector containing pairs of a generator - receiver for emitting and receiving ultrasound according to a mirror-shadow control scheme, as well as a data processing device connected by its inputs to the outputs of ultrasound receivers, characterized in that the generators and receivers of ultrasound are located on one line in row, and the data processing device is configured to receive a differential signal from the outputs of the measuring channels and compare the level of the specified differential signal with the rejection level. 2. The flaw detector according to claim 1, containing pairs of the generator - receiver with the same characteristics of the electron-acoustic tract. 3. A flaw detector according to claim 2, characterized in that the offset between the receivers is equal to the offset between the generators. 4. A flaw detector according to claim 1, containing generator-receiver pairs located with mutual overlap. 5. A flaw detector according to claim 1, characterized in that the displacement between the generators is from 3 to 900 mm. A flaw detector according to claim 1, characterized in that all the generators and receivers are assembled into groups of homogeneous elements. A flaw detector according to claim 1, characterized in that N> 2, where N is the number of generator-receiver pairs, which is even, and the data processing device is configured to receive differential signals from the outputs of alternating measuring channels. The flaw detector according to claim 7, containing the generator-receiver pairs displaced uniformly, while the data processing device is capable of averaging the measurement result. The flaw detector according to claim 7, containing the generator-receiver pairs displaced unevenly, and the data processing device is made�

Description

Ultrasonic flaw detector with differential compensation of interfering factors

The utility model relates to means for ultrasonic (US) control of extended objects, including products of sheet, long and shaped steel. The device can be used for high-speed operational control of a rail track.

Currently, the mirror-shadow method of ultrasonic testing, based on recording the decrease in the amplitude of the transmitted ultrasonic wave under the influence of a defect, is relevant.

A flaw detector is known from patent document SU 1497561 A1, which is a device for implementing the method of mirror-shadow ultrasonic testing of products of equal cross section, including railway rails. Known flaw detector contains one pair of generator-receiver for radiation and reception of ultrasound according to the mirror-shadow control scheme. In this case, the presence of a defect is determined by the magnitude of the measured slope of the change in the amplitude envelope of the received oscillations, which allows to increase the reliability and accuracy of control at significant scanning speeds due to the fact that in case of disturbance of the acoustic contact due to bouncing of the transducers on irregularities of the path, the specified slope is less than the same value when defect.

The closest analogue of the utility model is an ultrasonic flaw detector according to RU 2137120 C1, containing pairs of a generator-receiver for radiation and reception of ultrasonic radiation according to a mirror-shadow control scheme, as well as a data processing device connected by its inputs to the outputs of ultrasonic receivers. In the known flaw detector, sensitivity is adjusted at each step of the signal processing in accordance with the level of acoustic contact: if the acoustic contact signals are less than the norm, for example, by 4 dB, then all other signal amplitudes are increased by 4 dB. On each millimeter of the path, N measurement cycles take place, each of which consists of K clock cycles, with the last two clock cycles associated with the acoustic contact signal. All this limits the maximum possible speed of the known flaw detector to a value of not more than 1 m / min, which narrows the scope of its use due to the low control performance.

However, the practical implementation of the mirror-shadow method is also difficult due to possible false positives caused by a drop in the level of the useful signal for reasons other than those specified in SU 1497561 A1 and RU 2137120 C1, which makes the known technical solutions not effective enough. Since the shape of the working face in the rail section differs from the nominal one due to wear, the measurement signal from the electro-acoustic transducer is attenuated due to the scattering of part of the energy of the ultrasonic waves in different directions or due to a change in the propagation path of ultrasonic waves relative to the receivers. The presence of corrosion on the reflecting surface of the rail head also causes partial scattering of ultrasonic waves and, as a result, attenuation of the recorded signal for transducers of any type. Pollution on the reflecting surface of the rail head leads to the absorption of ultrasonic waves and the weakening of the useful signal. In addition, the attenuation of ultrasonic waves differs in rails of different manufacturers, which means that the amplitudes of the received signals differ from the same defects if such rails are laid in the same way. In each of these cases, at some point, the level of the useful signal in the receiver will drop so much that it will become lower than the rejection level and the flaw detector will be triggered spontaneously, caused not by the presence of a defect, but by too much scattering or absorption of the ultrasonic beam. For this reason, the mirror-shadow method of ultrasonic testing has found insufficient distribution in high-speed flaw detection of such an important object as a rail track.

The objective is to reduce the number of false positives in the process of ultrasonic testing at speed, while maintaining the high sensitivity of the flaw detector.

The technical result provided by this useful model is to increase the selectivity of the mirror-shadow ultrasonic flaw detector to the controlled defects of the test object during high-speed scanning.

This technical result is achieved due to the fact that in an ultrasonic flaw detector containing pairs of generator-receiver for radiation and reception of ultrasound according to the mirror-shadow control scheme, as well as a data processing device connected by its inputs to the outputs of ultrasonic receivers, the generators and receivers of ultrasound are located at one line in a row, and the data processing device is configured to receive a differential signal from the outputs of the measuring channels and compare the level of the specified differential signal with the rejection level.

In a particular case, the flaw detector contains pairs of the generator-receiver with the same characteristics of the electro-acoustic path.

Also in the particular case, the offset between the receivers is equal to the offset between the generators.

In another particular case, the flaw detector contains a pair of generator-receiver located with mutual overlap.

In another particular case, the displacement between the generators is from 3 to 900 mm.

Also in the particular case, all the generators and receivers are assembled into groups of homogeneous elements.

In another particular case, N> 2, where N is the number of generator-receiver pairs, which is even, and the data processing device is configured to receive differential signals from the outputs of alternating measuring channels.

In a particular case, the flaw detector contains a pair of generator-receiver, offset uniformly. In this case, the data processing device is configured to averag the measurement result.

In another particular case, the flaw detector contains pairs of generator-receiver, shifted unevenly, and the data processing device is configured to give the difference signals weighting coefficients during averaging.

The utility model is illustrated by the following illustrations.

FIG. 1-2: mirror-shadow scheme of ultrasonic inspection of a railway rail in the absence of defects, top view, and waveform at the output of the measuring channel.

FIG. 3-4: mirror-shadow rail monitoring scheme when a defect appears near the working edge of the rail head and the shape of the corresponding output signal.

FIG. 5-6: mirror-shadow scheme of rail monitoring in the presence of a defect in the central part of the head and the signal shape at the output.

FIG. 7-8: mirror-shadow diagram of the control rail with a defect near the outer part of the head and the shape of the measuring signal.

FIG. 9-10: shows the increase in the width of the dip of the measuring signal when a longer defect is detected.

FIG. 11: Ultrasound control circuit of rails with two pairs of converters, top view.

FIG. 12: monoblock arrangement of ultrasonic converters on the rail head with an internal defect, view from the end of the rail.

FIG. 13: arrangement of a two-channel monoblock of ultrasonic converters on the rail head, side view.

FIG. 14: simplified circuit diagram of an ultrasonic flaw detector with differential compensation of interfering factors.

FIG. 15-16: waveform at the output of the first measuring channel for a short-term separation of the monoblock from the rail head and in the absence of separation, respectively.

FIG. 17-18: waveform at the output of the second measuring channel for a short-term separation of the monoblock from the rail head and in the absence of separation.

FIG. 19-20: the form of the difference signal when the monoblock is torn off the rail surface and in the absence of separation.

FIG. 21: four-channel monoblock with uniform channel offset.

FIG. 22: four-channel monoblock with uneven channel offset.

The implementation of this utility model is shown on the example of the design of the ultrasonic flaw detector, preferred for operational control of the rail track.

Using a mirror-shadow scheme of ultrasonic testing, the flaw detector contains a pair of acoustically-connected electro-acoustic transducers 1 and 2 (Fig. 1). Converter 1 performs the function of a generator of ultrasonic vibrations, and converter 2 serves as a receiver of reflected ultrasonic waves and generates a measuring electric signal at its output (Fig. 2). Both transducers are placed on the side of the working side surface of the rail 3. The mirror-shadow circuit of the ultrasonic inspection of the rail allows us to determine the depth of the internal defect 4 and its size from the waveform (Fig. 3-10).

As electro-acoustic transducers used electromagnetic-acoustic transducers (EMAT) 1, 2, 5 and 6. EMAT 1 and 2 form the first pair of acoustically coupled transducers. The second pair is formed by EMAT 5 and 6. EMAT 1 and 5 serve as generators of ultrasonic vibrations, and EMAT 2 and 6 serve as receivers of ultrasonic waves reflected from the opposite face of the rail head 3. Moreover, the centers of the acoustic axes of all EMATs are located in a single row and are on the same line l-l (Fig. 11-13), constructively forming a linear monoblock of 7 transducers on a common carrier platform. The working surfaces of EMAT 1, 2, 5 and 6 lie in the same plane and face the object of control. EMAP pairs are located with mutual overlap, because elements of the first pair of converters alternate with elements of the second pair. Due to the alternation of the elements of the pairs, the generators 1, 5 form in their arrangement the first homogeneous group, and the receivers 2, 6 form the second homogeneous group, distant from the first group.

The first pair of EMAT is part of the first measuring channel, and the second pair of EMAT is part of the second measuring channel. Both channels are located in the same sounding plane and are characterized by acoustic coupling, respectively, of generator 1 with receiver 2 and generator 5 with receiver 6 according to a mirror-shadow control scheme, for which generators 1, 5 provide an inclined input of the ultrasound beam into the object of control, and receivers 2 , 6 are shifted from them by a distance corresponding to the thickness of the rail head 3 and the angle of entry of the ultrasound beam. The offset d between the centers of the receivers is equal to the offset between the centers of the generators (Fig. 13) and is 100 mm for this example. Since EMAT 1, 2, 5, and 6 are of the same type, and the regularity of their location is the same, the characteristics of the electron acoustic paths are completely identical.

EMAP 1, 2, 5 and 6 are electrically connected by their inputs / outputs to a control device and a data processing device, structurally made as a single digital computing device 8 with an interface part and analog functional units. The difference amplifier (subtractor) 9 of the measuring signals is one of the indicated analog functional units (Fig. 14) or is implemented by computer means in the form of a digital functional unit.

The ultrasonic flaw detector is mounted on a railway carriage and the monoblock 7 is brought to the working side surface of the rail 3. The device is put into operation and they begin to move along the rail by scanning the head 3 of the ultrasonic rail with the beam in search of internal defects such as transverse cracks 4. In the figures, the direction of movement is arbitrary shown by arrow V, however, due to the uniformity of EMAT 1, 2, 5 and 6 and the symmetry of the sounding scheme, the device is also able to work when moving in the opposite direction.

The control device supplies electric pulses to the generators 1, 5 for the emission of ultrasonic vibrations at the same angle to the rail surface. In the absence of defect 4, receivers 2 and 6 constantly receive an acoustic through signal reflected from the opposite wall of the rail head 3. The appearance of defect 4 leads to a drop in the level of the useful signal. During scanning, two identical measuring channels are formed with as close as possible characteristics, the second channel being offset in space by a distance d relative to the first channel along the axis of movement coinciding with the longitudinal axis of the rail (Fig. 11).

The electrical signals from the outputs of the receivers 2 and 6 have the form shown in FIG. 15-18, where: A is a small defect; B is a medium-sized defect, accompanied by a separation of the monoblock of 7 converters from the surface of the rail head 3; C - rail joint; D is a significant defect. If necessary, the measuring signals are first pre-processed, in particular, filtered or pre-amplified, and then fed to the input of the differential amplifier 9. The received differential signal (Fig. 19 or 20) from the output of the amplifier 9 is transmitted to the input of a computing device 8 that compares the level of the received differential signal in its original form, or subjected to post-processing, with a set rejection level and implementing other algorithms for processing measurement results embedded in it. If the drop in the difference signal level exceeds a predetermined rejection level, then the ultrasonic flaw detector informs the operator about the presence of defect 4 in the rail head 3.

Due to the fact that the generators and receivers are located on the same line in a row, the second measuring channel is displaced in space relative to the first channel along the axis of motion in the implementation shown in FIG. 11 schemes. In this case, defect 4 first crosses the first ultrasound beam, and after a while the second beam. The delay between the drops of the signals from the outputs of the receivers 2 and 6 will be δt = d / υ, where: δt is the time delay between the signals; d is the offset between the channels; υ is the speed of the transducers relative to the control object. Due to the delay between the measuring signals, the total amplitude of the signal from defect 4 on the difference signal almost doubles. However, any interfering factor that reduces the level of the received signal (bouncing, scattering, corrosion, changing the shape of the profile, the difference between the properties of the real rail from the tuning rail, etc.) acts on the measuring channels simultaneously and equally. Accordingly, changes in the measuring signals caused by the interfering factor do not have a time delay, and therefore their difference will be close to zero, which allows you to filter out this interference signal in this way, rather than fighting the interfering factor by increasing the flaw detector gain, which can lead to the omission of a small or even medium defect.

As can be seen from FIG. 15 and 16, the type of signal at the output of the first measuring channel with a short-term separation of the monoblock 7 from the rail head 3 differs significantly from the signal in the absence of separation. A similar picture is observed for the second channel (Fig. 17, 18). However, the curve of the difference signal at separation (Fig. 19) is almost identical to the curve of the difference signal in the absence of separation (Fig. 20). Thus, the separation of the monoblock 7 from the rail head 3 did not affect the resulting signal difference, although for each channel individually this was significant.

As a result, the arrangement of ultrasonic generators and receivers on one line in a row and the implementation of a data processing device with the possibility of receiving a differential signal from the outputs of the measuring channels and comparing the level of the indicated differential signal with the rejection level increased the selectivity of the mirror-shadow ultrasonic flaw detector to the controlled defects of the inspection object in scanning process by compensating for the influence of all interfering factors, and not just one of them. Moreover, eliminating the need for clocking the flaw detector and highlighting individual clock cycles to adjust its sensitivity has reduced the number of false positives during high-speed ultrasonic testing at speeds up to 200 km / h while maintaining high sensitivity of the flaw detector.

During the scanning process, the selectivity of the ultrasonic flaw detector to the controlled defects of the test object will be the higher, the closer to each other the characteristics of the electron-acoustic path of the measuring channels, which is determined to a large extent by the accuracy of setting the equality of the offset between the receivers to the offset between the generators.

The distance d is chosen empirically depending on the requirements, in particular, on the speed of control and the size of the detected defects. In practice, increasing the selectivity of the ultrasonic flaw detector to the controlled defects of the test object during the scanning process is achieved if the value of d is in the range of 3 ÷ 900 mm.

The arrangement of generator-receiver pairs with mutual overlap, when all the generators and receivers are assembled in groups of homogeneous elements, is necessary if the value of d should not exceed the base distance between the converters in the pair.

In addition, it is possible to increase the selectivity of the ultrasonic flaw detector to the controlled defects of the test object during scanning when receiving measurement information from a larger number of channels. The number of generator-receiver pairs for this is chosen from the condition N> 2, where N is the number of channels, which is even. In this case, two options for the location of the pairs of the generator-receiver are possible: uniform and uneven. With a uniform mutual offset of the pairs of converters (Fig. 21), the measurement information signal is obtained as the average difference between the signals from the channels with even and odd numbers, which allows you to get rid of random noise. If the channels are shifted unevenly (Fig. 22, where S is a constant), then the difference signals are first weighted, thereby adjusting the result for more accurate selectivity, and then averaged.

Possible implementations of the present utility model are not limited to the presented example. The technical solution is also suitable for monitoring the track from the rolling surface to sound the entire rail and even from the side of the rail neck. It is also possible to improve the selectivity of ultrasonic flaw detectors operating, for example, on the basis of the shadow method or the multiple shadow method.

Claims (9)

1. An ultrasonic flaw detector containing pairs of a generator - receiver for emitting and receiving ultrasound according to a mirror-shadow control scheme, as well as a data processing device connected by its inputs to the outputs of ultrasound receivers, characterized in that the generators and receivers of ultrasound are located on one line in row, and the data processing device is configured to receive a differential signal from the outputs of the measuring channels and compare the level of the specified differential signal with the rejection level. 2. The flaw detector according to claim 1, containing pairs of the generator - receiver with the same characteristics of the electron-acoustic tract. 3. The flaw detector according to claim 2, characterized in that the offset between the receivers is equal to the offset between the generators. 4. The flaw detector according to claim 1, containing pairs of the generator - receiver, located with mutual overlap. 5. A flaw detector according to claim 1, characterized in that the displacement between the generators is from 3 to 900 mm. 6. A flaw detector according to claim 1, characterized in that all the generators and receivers are assembled into groups of homogeneous elements. 7. The flaw detector according to claim 1, characterized in that N> 2, where N is the number of generator-receiver pairs, which is even, and the data processing device is configured to receive differential signals from the outputs of alternating measuring channels. 8. The flaw detector according to claim 7, containing the generator-receiver pairs displaced uniformly, while the data processing device is configured to average the measurement result. 9. The flaw detector according to claim 7, containing the generator-receiver pairs displaced unevenly, the data processing device being capable of imparting weighting coefficients to the difference signals during averaging.

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