RU2309402C2 - Method of ultrasonic test of rail welds - Google Patents

Abstract

FIELD: testing engineering.

SUBSTANCE: method comprises mounting the measuring unit on the surface of the rail and probing the weld with measuring members by means of emitting probing ultrasonic signals and receiving ultrasonic signals reflected from defects. The measuring unit is made of several measuring members.

EFFECT: enhanced reliability.

6 dwg

Description

The invention relates to the field of non-destructive testing using ultrasonic (ultrasound) waves to visualize the internal structure of an object and detect internal defects, in particular, in welded joints of rails.

Known methods for ultrasonic welding of rail joints [1] (Markov A.A., Shpagin D.A. Ultrasonic inspection of rails. St. Petersburg: "Education - Culture", 1999. - 230 p.) P. 208, Fig. 3.5.3.6 . which consists in the fact that an ultrasonic measuring element is installed on the railing surface of the rails, which, according to appropriate sounding schemes, is able to detect a defect in a certain part of the welded joint of the rails, probe the welded joint of the rails with a measuring element, for which probing radiation is emitted and reflected ultrasound signals are received. Then assess the fact of the presence or absence of the reflected signal and decide on the presence of a defect in the corresponding part of the welded joint of the rails.

This method of figure 1 suggests the presence of measuring elements consisting of one 1 or two - 2 and 3 ultrasound transducers. The ultrasonic transducer 1 emits a probe and receives the signal reflected from the defect 4 according to the sounding pattern — along the welded joint of the rails 5. The measuring element, consisting of ultrasonic transducers 2 and 3, can use several sounding schemes 2 → 3, 3 → 2, 3 → 3, 2 → 2 to detect a defect 4. Several sounding schemes allow you to detect defects of different properties and orientations in one part (neighborhood of point 4) of the welded joint of the rails. The dimensions of this part are determined by the radiation pattern of the ultrasonic transducer, the orientation and distance to the defect and its dimensions, as well as other circumstances. Thus, in most flaw detection methods, it is assumed that there are interdependent ones: the positions of ultrasonic transducers, sounding schemes, and the location of defects that can be found, i.e. Each measuring element is able to detect a defect in one part of the welded joint.

By changing the position of the ultrasonic transducers on the rails, it is possible to conduct a defectoscopy of welding along the axis of symmetry of the rail with the required resolution. For example, in methods [2] Ultrasonic rail weld scanner, Patent Application No. US 2937522 changes relative, application No. 2003111667/20, publication No. 34018 and [3] Ultrasonic rail weld scanner, US Pat. No. 2937522 the position of the ultrasound transducers and, accordingly, the part of the welded joint undergoing investigation.

The disadvantages of such methods are the low speed and quality of measurements. The first drawback is that moving the measuring element and positioning it (determining and entering the data of its current position into the path for evaluating the measurement results) requires a rather long time. As a result, under factory conditions, the time of investigation of one welded joint of rails reaches 45 minutes [4]. The second drawback is associated with poor quality of detection of defects due to the limited sounding area - the detection sections are located only on the axis of symmetry of the welded joint of the rail.

The quality and reliability of defect detection can be improved using various defect sounding schemes: echo, mirror shadow, shadow, mirror, delta (see [1], p. 37). For example, in the method of ultrasonic monitoring of rails [5] RF Patent No. 2227911 Method of multichannel ultrasonic monitoring of rails, which consists in the fact that on the surface of the rails an ultrasonic measuring unit is installed containing several measuring elements, each of which is capable of detecting defects by sounding schemes in a certain part of the rail, the welded joint of the rails is sequentially probed with measuring elements, for which probing is emitted and reflected ultrasound signals are received. Next, evaluate the received signals and decide on the presence of a defect in the corresponding part of the rail.

This method involves the presence of several measuring elements with different sensing schemes, which allows to detect defects of different types and orientations. By moving the measuring elements, it is possible to detect defects in all parts of the object under study with a given resolution.

The disadvantages of this method is also the low speed of measurements, as well as poor fitness for sensing welded joints of rails.

Thus, in most analogues known to the authors, the number of measuring elements and, accordingly, ultrasonic transducers is selected to be minimal and is determined by the number of selected methods and sensing schemes. Most often, one measuring element is used, and the required resolution of sounding is achieved due to its movement on the surface of the controlled product.

Closest to the claimed is a method of ultrasonic testing of welded joints of rails, [6] ULTRASONIC TESTING DEVICE FOR INSPECTING THERMIT RAIL WELDS (Ultrasonic device for monitoring thermite welding of rails) CANAC CONSULTANTS (US), GB 1506214, G01N 29/04, which consists in that in the area of the welded joint on the rolling surface of the rail, a measuring unit is installed containing several measuring elements, each of which is able to detect a defect in a certain part of the welded joint, probe the welded joint in series with each measuring element m, which radiate the probing and receiving the reflected ultrasonic signal. Next, the fact of the presence or absence of the reflected signal is evaluated and a decision is made on the presence of a defect in the corresponding part of the welded joint of the rails.

This method involves the use of three types of measurements. The first is the positioning of the center of the measuring unit above the weld. For this, the "central" measuring element probes the rail perpendicular to the rolling surface, and the measuring unit is moved along the rail. If there is no response from the base of the rail due to poor passage of the probe signal through the weld zone, a decision is made to find the weld under the central measuring element. The second type of measurement is the search for defects (welding porosity) in this position of the measuring unit. In this case, ultrasonic signals that are symmetrical with respect to the central pair of “side” ultrasonic transducers sequentially emit and receive ultrasonic signals, examining porosity defects along the depth of the welded joint. The reflected signal indicates a defect at the corresponding depth of the weld. The third type of measurement is the detection of defects at the border of the welded joint of the rails. In this case, the measuring element, consisting of two “external” ultrasonic transducers (together with the entire measuring unit) is moved along the rail, probing the weld. In the absence of a reflected signal, they conclude that there is a welding defect in the corresponding section of the welded joint of the rails.

The disadvantages of this method are:

- Low measurement speed, associated, as in other analogues, with the need to move and position the measuring unit.

- Poor quality detection of defects in the welded joint of the rails.

The last drawback is connected, firstly, with the fact that the location of the measuring elements on the surface of the rail involves searching for defects only along the symmetry axis of the welded joint (in the zone of the longitudinal axis of the rail) of the rail joint. However, welding defects can be present along the entire width of the head and at the base (in the feathers of the sole) of the rail. Secondly, the principle of detecting defects in the prototype in the second type of measurement is the absence of signals reflected from defects. However, the absence of a defect signal can be explained by various reasons, in particular, the lack of acoustic contact of the measuring element with the rail surface, the presence of a welding defect in the path of the probing pulses, and, finally, a hardware malfunction.

The problems solved by the claimed method are to increase the speed of control and reliability of detection of defects.

To solve these problems in the inventive method for ultrasonic testing of welded joints of rails, which consists in the fact that an ultrasonic measuring unit containing several measuring elements is installed on the rolling surface of the controlled rail, each of which is capable of detecting defects in a certain part of the welded rail joint by appropriate sounding schemes, sequentially probe the welded joint of the rail with measuring elements, for which probes are emitted and reflected ultrasound signals are received, at selected sites The astrages of the rail surface establish and fix motionlessly several ultrasonic measuring units, select additional sounding schemes between different measuring elements, select sounding schemes of the measuring elements so that they together allow to detect defects in the entire section of the welded joint of the rail with a given resolution, when probing, measure the amplitudes and the temporary position of the reflected signals, calculate the spatial position of the defect, combine and display the results of all ndirovany, which evaluate them and make a decision about the quality of the weld joint.

Significant differences of the proposed method are:

The installation of several ultrasonic measuring units on selected sections of the rail surface, for example, on the surfaces of the sole feathers and on the sides of the rail head, allows to improve the quality of measurements - to perform a flaw detection of the entire welded joint of an object of complex shape, which is the rail. An increase in the number of measuring units (ultrasonic converters) increases the cost of equipment, which is offset by an increase in labor productivity and a decrease in wear of ultrasonic converters.

In the prototype, the quality of the welded joint is examined by one ultrasonic measuring unit - along the axis of symmetry of the rail, which does not provide high quality flaw detection.

The fixed installation and fastening of ultrasonic measuring units on the rail surfaces in the heat-affected zone allows to exclude their movement during the measurement process, and thereby increase the speed and stability of measurement results, reduce costs associated with wear of ultrasonic transducers. In addition, it becomes easier to provide and control the acoustic contact of ultrasonic transducers with the rail surface.

In the prototype, probing the joint of a welded joint requires moving the measuring unit, which leads to fluctuations in the acoustic contact, to wear of the ultrasonic transducers, necessitates the positioning of the ultrasonic measuring units, which increases the complexity and reduces the reliability of the measurements.

The choice of additional sounding schemes between the measuring elements allows the use of new sounding schemes formed due to the presence of several measuring elements in the ultrasonic measuring unit, as well as several ultrasonic measuring units. Such schemes provide additional information about the welded joint of the rail without the introduction of additional measuring elements.

In the prototype there is a strict correspondence between the measuring elements (ultrasonic transducers), sounding schemes and the location of the defect. As a result, despite the presence of several ultrasonic converters, the number of sounding circuits (defects) is limited by the number of measuring elements.

The choice of sounding schemes of the measuring elements so that they together allowed to detect defects over the entire cross section (in all parts) of the welded joint of the rails with a given resolution. This allows you to achieve the specified quality of the diagnostics of the weld joint of the rails at a high measurement speed associated with the stationary position of the measuring units.

In the prototype, the measuring elements can search for a defect in the welded joint of the rail with a given resolution only along the axis of symmetry, while the measuring unit must be moved.

Measurement of the amplitude of the received signals allows you to more accurately assess the reflected signal, the amplitude of which can vary due to size, angle of orientation of the defect, as well as its properties. A differentiated evaluation of the reflected signals allows you to more clearly display the results of sounding, for example, in a grayscale image and thereby improve the quality of flaw detection.

The prototype uses a binary solution - is there a signal or not, which reduces the information content of the measurements and makes it difficult to evaluate their results.

Measuring the temporal position of the received signals and calculating the spatial position of the defect provides information on the exact location of the defect, which improves the quality of diagnostics.

In the prototype, the position of the defect is determined only in the second type of measurement, since each "side" measuring element is uniquely associated with the location of the defect. In the third type of measurement, only defect detection is provided. The exact determination of their size and position requires technical and time costs for positioning the measuring unit.

Combining and displaying the results of all soundings of the welded joint allows one to obtain the results of all measurements on a single rail cut image in the form of a general grayscale picture of the state of the welded joint of the rails taking into account the amplitudes of the reflected signals and the location of the defects. This simplifies diagnosis and improves the quality and speed of evaluation.

In the prototype, the pulse signals received from each measuring element are displayed separately for each channel. In the presence of many measuring elements, the assessment of the quality of the welded joint in this way is significantly complicated and requires highly qualified operator.

Evaluation and decision-making about the quality of the welded joint of the rails according to the integrated circuit allows the operator to easily make a reliable decision about the quality of the welded joint, in particular, it is possible to assess the exact position and dimensions of the defect.

In the prototype, the operator has to observe the reflected pulses (or lack thereof) for each sounding channel separately. This significantly complicates the analysis of sounding results and reduces the operator's productivity.

Thus, the inventive method improves the speed and quality of detection of defects.

The inventive method is illustrated by the following graphic materials:

Figure 1 - sounding diagram of the welded joint of the rails.

Figure 2 - arrangement of the measuring units.

Figure 3 - scheme for selecting additional sounding schemes.

4 is a diagram of the sounding zone of the sole (base) of the rail.

5 is an example of displaying measurement results.

6 is a device that implements the inventive method.

Consider the possibility of implementing the proposed method of ultrasonic testing of welded joints of rails.

The measuring unit is a design that combines several measuring elements, with the possibility of their snug fit to the rail surface to ensure acoustic contact. The measuring elements contain one or two ultrasonic transducers. Several ultrasound measuring units are installed on selected sections of the rail surface in the area of the welded joint. A complex rail profile, for example, may require, FIG. 2, the presence of ultrasonic measuring units on the rolling surface of the rail 6, on the side walls of the head 7 and 8, as well as on the feathers of the sole of the rail 9 and 10. Each measuring element has sounding schemes that allow it to detect defects of certain properties in a given zone of the welded joint of the rails. For example, the ultrasonic measuring unit 6, Fig. 1, mounted on the rolling surface of the rail 5, consists of three ultrasonic transducers 1, 2 and 3, forming two measuring elements. The first one consists of one ultrasonic transducer 1 and has a sounding circuit directed along the axis of the weld. The second measuring element contains two ultrasonic transducers 2 and 3 and can use several sounding schemes 2 → 3, 3 → 2, 3 → 3.1 → 1 to detect defect 4 by echo or mirror (tandem) ultrasonic testing methods [1]. Each of the schemes is effective for detecting a defect of a certain orientation and properties. To sound the entire vertical axis of symmetry of the welded joint, it is necessary to install several measuring elements, Fig. 3, with sounding schemes similar to those described, but directed to different parts in height.

Sounding schemes for the head and sole of the rail can be similarly constructed. Figure 4 shows the measuring units 9 and 10 mounted on the feathers of the rail base and consisting of ultrasonic transducers 9 ₁ -9 ₄ and 10 ₁ -10 _4, respectively, and, as an example, the sounding diagram of defect 4 from the ultrasonic transducer 9 ₁ -10 ₂ according to the mirror method.

The number of measuring units and measuring elements in them is selected based on the requirements for the resolution of measurements, which is associated with the size of the defects that must be detected. 2, a grid of cells is applied to the rail profile. The grid step determines the size of the defects to be detected and, accordingly, the number of measuring blocks, elements in them and the sounding scheme.

The presence of several measuring elements in block 6 allows you to select additional sounding schemes inside it, for example, as shown in figure 1, 2 → 1, 1 → 2, realizing the delta method of ultrasonic inspection [1]. In Fig. 3, the signal emitted by the ultrasonic transducer 2 can be received not only by the ultrasonic transducer 3 - its own measuring element, but also by the neighboring 11 and 12, which are part of the measuring elements 11-13 and 12-14 and t .P. Such sounding schemes provide additional information about the location and properties of the defect 4. For certain orientations of the defect 4, the reflected signals obtained by the additional circuits can have even greater amplitude than the signals from the standard sounding circuits inside the measuring element.

Measuring blocks 6-10 can be installed on one or both sides of the welded joint. The latter option allows you to detect defects on both sides of the welded joint of the rails, and thereby improve the quality of detection of defects.

Additional sounding schemes can also be obtained due to cross-sensing of the welded joint by measuring elements of different blocks. For example, ultrasonic measuring units 7 and 8 are designed to detect welding defects in the rail head. The probe signals emitted in one block can be received in another. Thus, additional sensing schemes can improve the quality of sounding without installing new measuring elements. At the same time, switching of ultrasonic converters is somewhat more complicated, but, given the multichannel nature of modern ultrasonic flaw detectors and the high speed of electronic switching of ultrasonic converters, the effect of additional sounding schemes exceeds the cost of their implementation.

Fundamentally, it is possible with each radiation of the probe signal to receive the signals reflected from the defect by all other ultrasonic converters, however, this would require excessive hardware costs. The result of the choice of sounding schemes is a sounding table, which establishes the correspondence between all ultrasonic converters, when they work in the radiation mode, and receivers of signals reflected from defects.

Thus, the choice of the number and installation locations of ultrasonic measuring units, the number of measuring elements in them, as well as the choice of methods, basic and additional schemes of the sounding scheme should ensure the detection of defects in all areas of the welded joint of the rails with a given resolution and the required quality.

The measuring blocks are fixedly mounted on the rail in the vicinity of the welded joint using clamping elements of any design or magnets to ensure reliable acoustic contact. A possible gap between the measuring unit and the rail surface is filled with contacting liquid.

Probe the welded joint of the rails sequentially with measuring elements according to the selected schemes. For this, the next ultrasonic transducer emits a pulsed ultrasonic signal and receives the reflected ultrasonic signals according to the selected sounding schemes and the sounding table.

The amplitudes of the received signals are measured for each ultrasound transducer that is currently receiving the reflected signal.

The temporal position of the received signals is measured, i.e. time interval between emitted and received signals.

The spatial position of the defect is calculated according to the well-known sounding scheme, the temporary position of the received signals and the propagation speed of the ultrasonic signal in the rail.

Combine and display the results of all sounding — the positions and amplitudes of all received signals in a common grayscale or color scheme, for example, in the image of a section of a welded rail joint, see FIGS. 2, 5. Note that the same defect 4 can be detected in several sounding schemes of ultrasonic transducers from measuring units 6, 7 and 8. In Fig.5b, a defect 4 with a large amplitude of the reflected signals (red color) is detected, and in 5a a continuation of a defect 4 is detected, but with a lower response amplitude (orange color). This display method provides high visibility and ease of decision making.

Evaluate the results of all soundings and decide on the quality of the welded joint of the rails. For this, the location and amplitudes of the received signals are compared, extended defects detected in adjacent parts of the welded joint, etc., are detected, on the basis of which a conclusion is made about its quality.

Thus, the inventive method provides a high speed sensing of the weld due to the elimination of the time-consuming procedure for moving ultrasound transducers with dynamic acoustic contact [7]. The proposed multi-channel sounding scheme allows to achieve high quality defect detection.

The structural diagram of a device that implements the inventive method is presented in Fig.6, where:

15. Ultrasonic transducers.

16. The first switch.

17. The second switch.

18. Generator of ultrasonic sounding signals.

19. The receivers of the reflected signal.

20. Analog-to-digital converters (ADC).

21. The computer.

22. Display.

Ultrasonic transducers 15 are designed for radiation and reception of ultrasonic signals and can be implemented on the basis of piezoelectric transducers. Each of them has its own radiation - reception angle, based on the chosen method and sounding scheme.

The first switch 16 is designed for sequential supply of a probe signal to ultrasonic converters 15. It can be implemented on the basis of electronic keys with a common input, control inputs and outputs connected to the corresponding ultrasonic converters.

The second switch 17 is designed to supply the signals reflected from the defect received by the selected ultrasonic converters 15 to the inputs of the reflected signal receivers 19. If the number of ultrasonic converters is N and the number of inputs of the processing device is M, then the second switch 3 should be able to connect any of N inputs with any of M outputs, depending on the control code K in accordance with the sounding table. Such a device can be implemented based on an analog N × M switching matrix.

The generator of ultrasonic sounding signals 18 is designed to generate a pulsed sounding signal and can be implemented on the basis of any of the traditional schemes.

The receivers of the reflected signal 19 are designed to receive, amplify and generate signals received by M - ultrasonic converters 15, currently operating in the receiving mode. They can be implemented on the basis of amplifier-forming devices.

Analog-to-digital converters (ADCs) 20 are designed to input M signals reflected from defects into a digital processing device. Signal conversion is carried out according to clock signals, which are not shown in the diagram for the purpose of simplification.

Computer 21 is designed to process measurement results. The processing algorithms are obvious and include the following program blocks:

- management of the first and second switches 16 and 17 according to the sounding table;

- start generator ultrasonic probe signal 18;

- receiving digitized reflected signals;

- measuring the temporary position of the received signals;

- estimates of the amplitudes of the received signals, in particular comparisons with detection thresholds;

- calculation of the location of the defect;

- display of all measurement results on the display screen 22.

Display 22 is designed to display measurement results.

The operation of this device is as follows.

Computer 21 provides control codes to the first 16 and second 17 switches. In this case, one of the ultrasound transducers is connected to the output of the probe signal generator 18, and several ultrasound transducers 15 are connected to the receivers according to the sounding table 19. According to the signal from the computer 21, the probe signal from the generator 18 is connected through the switch 16 and the selected ultrasound transducer 15 is fed to welded rail joint. The reflected signals are received by ultrasonic converters 15 and fed through the switch 17 to the receivers 19 and to the ADC 20, which, with a high frequency set by the clock generator, form the digitized values of the reflected signals supplied to the computer 21. The latter compares the received responses with the detection thresholds and calculates the location defect. The computer 21 performs similar operations, sequentially selecting all ultrasound transducers 15 as a source of sounding signals, and other ultrasonic transducers 15 according to the sounding table as receivers. After sounding the weld by all ultrasonic transducers 15, the coordinates of all the points that are “suspicious” of the defect appear in the computer's memory. In this case, the coordinates of the defects obtained by different ultrasound transducers 15 may be the same. These points are displayed together on the screen of the monitor 22 against the background of the cut of the welded joint. Depending on the number of coincidence of coordinates, you can change the brightness, size or color of the points. According to this image, the operator makes a decision on the quality of the welded joint of the rails.

Thus, the claimed method can be implemented in practice and provides increased control speed and reliability of detection of defects of welded joints of rails.

Literature

1. Markov A.A., Shpagin D.A. Ultrasonic flaw detection of rails. St. Petersburg: "Education - Culture", 1999. - 230 p.

2. Liksakov SV, Kononov SB, Bovdey V.A., Markov A.A. and other Device for ultrasonic testing of welded joints, application No. 2003111667/20, patent for utility model No. 34018, Bull. No. 32, 2003.

3. Ultrasonic rail weld scanner (SPERRY PROD INC (US), patent US 2937522.

4. Molotkov S.L. Tests of control tools for aluminothermic welded joints of rails. - In the world of NK. No. 2004. S.76-77.

5. Markov A.A., Shpagin D.A., Shilov M.N., Verevkin A.Yu. Method of multichannel ultrasonic rail monitoring. RF patent No. 2227911. Bull. No. 12, 2004.

6. ULTRASONIC TESTING DEVICE FOR INSPECTING THERMIT RAIL WELDS (Ultrasonic device for control of thermite welding of rails) CANAC CONSULTANTS (US), GB 1506214, G01N 29/04.

7. Non-destructive testing: Handbook of 7 volumes. Under the general ed. V.V. Klyueva. T.3: Ermolov I.N., Lange Yu.V. Ultrasonic inspection - M.: Mechanical Engineering, 2004 .-- 864 p.

Claims (1)

The method of ultrasonic testing of welded joints of rails, which consists in the fact that an ultrasonic measuring unit containing several measuring elements, each of which is capable of detecting defects in a specific area of the welded joint of a rail, is subsequently probed by a welded joint of the rail with measuring elements for which they emit sounding and receive ultrasonic signals reflected from possible defects, characterized in that you early sections of the rail surface are installed by several ultrasonic measuring units, which are fixedly mounted on them, additional sounding schemes are selected between the measuring elements, the sounding schemes of the measuring elements are chosen so that they together allow to detect defects in the entire section of the welded joint of the rail with a given resolution when probing measure the amplitudes and temporary position of the reflected signals, calculate the spatial position of the defect, combine and about They represent the results of all soundings, according to which they are evaluated and a decision is made on the quality of the welded joint.

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