RU2665360C1 - Universal waveguide of acoustic emission signals - Google Patents

Abstract

FIELD: physics.SUBSTANCE: invention relates to waveguides of acoustic emission signals (AE) intended for controlling and monitoring of hazardous production facilities or their elements at temperatures outside the permissible temperature range of application of the AE converter. Universal waveguide of acoustic emission signals with superimposed heat sink elements is characterized in that the heat dissipating device is collapsible and consists of several constituent elements that allow: to carry out its mounting/dismounting during the operation of the waveguide; reorient the device to a new monitoring object, temperature mode of operation, or other waveguide; ensure the compactness of transportation and storage, as well as manufacturability in manufacturing and maintainability during operation.EFFECT: technical result consists in the possibility of ensuring the compactness of transportation and storage, as well as manufacturability in the manufacture and maintainability during operation.1 cl, 5 dwg

Description

The invention relates to acoustic methods of non-destructive testing and technical diagnostics of industrial equipment, based on the registration of acoustic waves using contact piezoelectric transducers, namely, waveguides for acoustic emission signals (AE). The waveguides are designed to transmit acoustic emission signals from the test object to piezoelectric transducers during non-destructive testing, technical diagnostics and monitoring of hazardous production facilities (OPO) at object temperatures beyond the allowable temperature range for the use of acoustic emission transducers (PAE). The invention may be applicable to other non-destructive testing methods based on the reception of acoustic waves.

The use of the AE method for assessing the technical state of OPO located at high or low temperatures is constantly accompanied by the risk of PAE performance loss. Such tasks include: preliminary AE monitoring of operating equipment before putting it out to overhaul to establish areas of increased attention; periodic AE monitoring of equipment during operation; AE control of start-up of installations with a temperature gradient of operation (refrigeration, compressor, etc.); ensuring the safety of equipment with a defect identified during operation until the next major overhaul, etc.

It is known that the working thermal loading of PAE without built-in electronic components at elevated temperature is limited by the Curie point of the piezomaterial (for example, + 50 ° С for CGS-2 (SbSI + Cr), + 80С ° for PVDF (C ₂ H ₂ F ₂ ) _n , + 290 ° С for TsTS-19 (Pb (ZrXTi _1-X ) O ₃ ), + 1150 ° С for lithium niobate (LiNbO ₃ ), etc.), and for PAE with built-in electronic components it is limited by the operating temperature range of the electronics ( for example, the operating temperature range of a PAE with a pre-amplifier integrated in the housing from -30 to + 80 ° C, without a pre-amplifier from -65 to + 177 ° C), except PAE is a complex device in which welded, soldered and adhesive joints of elements and compounding of materials with different coefficients of linear and volume expansion are used, which, due to temperature changes, leads to internal mechanical stresses, the formation of cracks and discontinuities, worsening the operational parameters of the device and removing it out of service.

The danger of PAE coming out of working condition during AE monitoring forces the operator to periodically monitor the efficiency of AE channels during the test. This leads to a delay in the timing of work, and in the event of failure of at least one transducer to a repeated AE control. Not to mention the fact that the cost of one PAE can be comparable and even more than the cost of work on AE control. Therefore, before conducting AE control, the risks of equipment failure due to exceeding the operating temperature of the converter are carefully analyzed. To reduce the likelihood of overheating or cooling of the PAE, various technical methods are used to reduce its thermal load. One of the main ways to solve the problem is the use of acoustic waveguides, which can significantly expand the scope of the AE method.

When designing an acoustic waveguide, the main problem is to ensure a balance between: the maximum temperature gradient, minimum acoustic losses, the compactness of the waveguide and the convenience of its installation. Consider the well-known technical solutions from the above positions to ensure the universality and efficiency of the use of AE waveguide.

A classical AE waveguide is a rod waveguide, which is a smooth metal round rod, one end of which is attached to the test object using a welded joint (welded waveguide) or holder (clamping waveguide), and a piezoelectric element or PAE is installed on the second [1 ÷ 11].

The process of transfer of thermal energy has a symmetry, i.e. upon overheating and supercooling by an equivalent temperature, a symmetric thermal gradient is observed, both when the waveguide is cooled from the side of the control object and when it is heated. Consider in the general case the dissipation of thermal energy supplied to the waveguide from the control object. It is known that with a one-way supply of heat to the rod, its temperature along the length varies according to the law:

where t _OK is the object of control; t _OC is the ambient temperature; m is the thermophysical coefficient, taking into account the cross section of the rod and the conditions of heat removal; L is the waveguide length. Considering that in the steady state heat transfer mode (t _OK -t _OC ) = const and m = const, it is obvious from (1) that in order to minimize the temperature at the waveguide at the installation site of the PAE t (L), it is necessary to increase its length (L). The use of a long waveguide leads to an increase in attenuation and distortion of the acoustic signal propagating in it. Thus, it is necessary to minimize the length of the waveguide, which is especially important for pressure waveguides, since with a long length, difficulties arise in mounting and holding it in the working position, ensuring the constant acoustic contact.

The known design of the clamping AE waveguide [12], which consists of several smooth rods of equal length screwed into each other, the front end of each rod has an external threaded part, and the rear end has an internal part (except for the latter on which the PAE is mounted). In application, several rods are screwed into each other through an acoustically transparent medium until the total waveguide length L, determined by (1), is reached. The main advantage of this design is that the waveguide is detachable, which means that it can be disassembled, compactly transported and assembled at another control object by changing its length L to new control conditions (temperature). The main disadvantage of this approach is that each end face is a phase boundary, which means that the separate acoustic impedance and AE signal loss are greater, the greater L.

From [5, 13], the construction of a pressure waveguide in the form of a tube is known which is filled with a liquid acoustically transparent medium, after which the edges of the tube are closed with sealed plugs. The advantage of this technical solution is that the liquid, which is the main acoustic channel, does not have a shear modulus, which means that only longitudinal acoustic waves can propagate in the waveguide. This solution is aimed at reducing signal distortions when passing through a waveguide, however, this approach has twice as many phase boundaries (which means a greater signal attenuation) compared to a classical rod-shaped clamp waveguide. In addition, the fluid inside the waveguide must have a freezing temperature below the temperature of the control object or a boiling point above the control temperature or under high pressure, which greatly complicates its manufacturing technology, increases the cost of the waveguide and limits its versatility in use. Also, this constructive approach does not increase the efficiency of heat exchange with the environment, therefore, it does not allow to reduce the waveguide length, which is also determined by formula (1).

Closest to the proposed technical solution is a method of increasing the efficiency of heat dissipation by performing fins on a rod waveguide [14, 15]. The presence of fins increases the heat transfer area, which allows more efficient heat dissipation, and therefore reduce the length of the rod. However, heat diffusers made at the same time with the waveguide rod are also an acoustic channel and the ingress of acoustic waves on them leads to increased attenuation and distortion of the latter. Also, this design has a high price, because the manufacture of diffusers along with the rod is technologically time-consuming.

The listed constructions of the known acoustic waveguides are generalized according to the compared physical properties in terms of thermal and acoustic resistance (performance characteristics that determine the waveguide operability) in FIG. 1. In FIG. 2 is an explanatory drawing for a description of structural features and embodiments of the proposed device. In FIG. 3 is a diagram of a device manufactured for experimental evaluation of its performance. In FIG. 4, the results of evaluating thermal fields obtained experimentally using a thermal imager and calculated are compared. In FIG. Figure 5 shows the experimental and calculated dependences of the temperature of heating of the PAE on the waveguide on the temperature of the test object (OBO) at an ambient air temperature of 25 ° C and various numbers of scatterers and the length of the waveguide rod.

The problem to which the invention is directed, is to increase the efficiency of heat dissipation by an acoustic emission waveguide while maintaining or improving its acoustic characteristics.

The technical result of the invention is achieved by using overhead heat dissipators without or having minimal acoustic coupling with the waveguide rod (main acoustic signal transmission channel).

The proposed device is shown in FIG. 2 and contains: heat dissipators (pos. 1), distance spacers (pos. 2), spacers (pos. 3) and latches (pos. 4). The device is universal and can be used independently (independently) or in conjunction with any of the above-described known technical solutions of the rod-type waveguide (Fig. 1), any cross-section (round, square, etc.). It is also seen from the design description that the device is collapsible, therefore: technologically advanced to manufacture, maintainable in use, provides compactness during transportation and storage, and can easily be reoriented to another temperature or control object (by changing the number of heat dissipators) or installed on another waveguide. Based on this, the size and number of spacers, spacers and heat dissipators is not fixed, but depends on the temperature gradient, which must be ensured and selected theoretically or experimentally in each specific case of its application individually, therefore it is limited only by the waveguide length (item 5) and the method its fastening (must support the weight of the device).

When assembling the device, heat diffusers (pos. 1) are collected alternately through distance spacers (pos. 2) into a heat-dissipating bag. Heat diffusers (item 1) are designed to increase the heat transfer area. Remote spacers (pos. 2) specify the distance between heat dissipators (pos. 1) and provide the condition for heat exchange between heat dissipators.

Rigid or elastic struts (pos. 3), which can have different thicknesses, are installed at the front and back of the heat dissipating bag. The spacers (pos. 3) are used to select the gaps, create a pressing force in the heat-dissipating bag (main or preliminary) and compensate for changes in the distance between the clamps (pos. 4) when changing the thickness of the heat-dissipating bag (changing the number of heat dissipators). The latches (pos. 4) can be: collet or petal type (Fig. 2a); threaded view (Fig. 2b); spring type (c); clamps (Fig. 2d); locking elements, for example, rings (Fig. 2e) or in the form of a tie (Fig. 2e), which can be fixed to the waveguide by the above methods, magnets or using acoustically opaque glue. The clamps (pos. 4) of the heat-dissipating packet can be of any other types that are not described, or a combination of the types described, which ensure the retention of the heat-dissipating packet on the waveguide and a sufficient compression force of the packet for efficient heat transfer. In addition, when assembling on the side surfaces of parts pos. 1, 2 and 3 for patients with heat exchange efficiency, heat-conducting paste can be applied. However, its use is not necessary to achieve a positive effect in the implementation of the device.

The inner diameter of the parts pos. 1, 2 and 3 can be manufactured precisely with the diameter of the waveguide (item 5) or with a gap. For greater heat transfer efficiency, a heat-conducting but acoustically opaque medium can be applied between the waveguide and the device. However, its use is also not necessary to achieve a positive effect in the implementation of the device.

The maximum efficiency of the device can be achieved only with the use of materials of parts pos. 1, 2, 3 and 4 with a maximum coefficient of thermal conductivity (copper, aluminum, steel, etc.). However, the device, although with less efficiency, is operable when using any heat-conducting materials.

The device can be installed at the beginning, end, middle or along the entire length of the waveguide. Depends on the conditions of use and the effectiveness of the exchange. The most effective installation of the device at the end of the waveguide (in front of the PAE). Details pos. 1, 2, 3 and 4 can also be made split or have a groove for mounting the device from the sides of the waveguide if it is impossible to mount the device from the end of the waveguide. In addition to this detail pos. 1, 2, 3, and 4 may have fasteners for the PAE holder or be integral with the PAE holder (Fig. 3).

In addition, if it is necessary to provide more intensive heat transfer, forced cooling can be installed on the device, for example, by attaching to the diffusers or next to them a small low-voltage fan and battery power, etc. However, achieving minimal noise, cost and ease of use of the device can can be achieved only if passive heat exchange is used (without using forced cooling), therefore this option is considered as the main one.

An example of achieving a positive effect and industrial applicability of the device are the results of an experimental study of the performance characteristics of the design of a rod rod waveguide with the proposed device and without it. Upon testing, the waveguide was a steel bolt M16 with a length of 100 mm onto which the proposed device was mounted (Fig. 3) in the following sequence: an aluminum spacer ∅16 / 24 mm with a length of 15 mm (item 3), then heat dissipators in the form of steel disks ∅16 / 80 mm with a thickness of 2 mm (pos. 1) through aluminum spacer rings ∅16 / 24 mm with a length of 5 mm (pos. 2) and the package was completed with an aluminum spacer ∅16 / 24 mm with a length of 15 mm (pos. 3). When assembling between parts, pos. 1, 2 and 3, heat-conducting paste KPT-8 was applied. Package details pos. 1, 2 and 3 was pulled together by a clamp in the form of a steel nut M16 (item 4). The waveguide (pos. 5), assembled with a heat-dissipating bag, was screwed into the threaded hole of the steel base (pos. 6), which was fastened with steel wire braces (pos. 7) to the TEMRSO SVN13864 heating table with some pressing force. The temperature of the heating table was set and maintained by the TEMPCO TRS-1000 control unit by feedback from the TEMPCO TRW00171 K-G thermocouple mounted on the heating table. The surface temperature at the installation site of the PAE (item 8) was recorded using a K-type thermocouple using a DT-838 multimeter and non-contact using a FLIR SC7700M thermal imager (Fig. 4a). During the study, the temperature in the room was maintained at + 25 ° C using an air conditioner, and the humidity in the room did not go beyond the range of 63 ± 3%. Temperature and humidity were controlled by a VIT-2 psychrometric hygrometer.

Since the assembled experimental setup was limited in the possibility of investigation to a temperature of + 300 ° C, and the waveguide in the number of options: waveguide length, number of scatterers and cooling conditions, the heat dissipation characteristics of the AE waveguide of all other options were estimated by mathematical modeling. To do this, according to the experimental data obtained, a mathematical model was compiled in the Siemens NX8 software package (Fig. 4b), which allows calculating various variations in the application of this waveguide by the finite element method with a difference from the experimental data of no more than 2% (Figs. 4 and 5).

- экспериментальные данные (остальные расчетные); «Температура ОПО» - температура первого конца волновода (у нагревателя), имитирующая температуру объекта контроля; «Температура ПАЭ» - температура второго конца волновода в месте установки ПАЭ; N - количество рассеивателей тепла (вариант N=0 соответствует волноводу без предлагаемого устройства); I - зона безопасной работы ПАЭ с ПУ (низкая вероятность выхода ПАЭ из строя); II - предельная зона работы ПАЭ с ПУ (65÷85°С) (высокая вероятность выхода ПАЭ из строя); III - зона гарантированного выхода ПУ ПАЭ из строя. Фиг. 5а - длина стержня волновода 100 мм, Фиг. 5б - 150 мм, Фиг. 5в - 200 мм и Фиг. 5г - 250 мм.In FIG. Figure 5 shows the limits of applicability for AE monitoring of high-temperature OPO waveguides of the type under study with the proposed device and without it according to the worst cooling option (configuration heat transfer in calm weather / calm, heat dissipators are perpendicular to the free fall vector). All other simulated heat exchange options provide a lower heat loading of the PAE, which means they have obviously better working conditions for the operation of the PAE. In FIG. 5 is indicated:

- experimental data (other calculated); “OPO temperature" - the temperature of the first end of the waveguide (at the heater), simulating the temperature of the object under control; "PAE temperature" - the temperature of the second end of the waveguide at the installation site of the PAE; N is the number of heat diffusers (option N = 0 corresponds to the waveguide without the proposed device); I - zone of safe operation of PAE with PU (low probability of PAE failure); II - the limiting zone of PAE operation with PU (65 ÷ 85 ° С) (high probability of PAE failure); III - zone of guaranteed PU PUE failure. FIG. 5a - waveguide rod length 100 mm, FIG. 5b - 150 mm, FIG. 5c - 200 mm and FIG. 5g - 250 mm.

FIG. 5a shows that the waveguide of the studied design without the proposed device (option N = 0), provided that the PAE temperature is not higher than + 65 ° C at an ambient temperature of + 25 ° C, can be used in AE monitoring of air-condition temperature with a temperature of no higher than + 78 ° C. In the presence of the proposed device under the same conditions, the temperature of the waveguide is: with 4 diffusers (N = 4) up to 102 ° C; with N = 5 to 115 ° C; with N = 6 to 125 ° C; with N = 7 to 132 ° С and from N = 8 to 142 ° С, i.e. the temperature of application of the waveguide rises by 1.5 ÷ 2.1 times. FIG. 5b ÷ 5g show that with a change in the waveguide length, the positive effect increases. The calculation results also show that by combining changes in the waveguide length and the number of scatterers it is possible to effectively optimize the dimensions of the waveguide for various installation and control conditions.

по следующей эмпирической формуле:According to the calculation results, it was found that using the nomograms of FIG. 5 with an error of not more than 5 ° C, it is possible to determine the heating temperature of the PAE on the waveguide of the studied design with convective heat transfer in the ambient temperature range (t) from +25 to + 45 ° C

according to the following empirical formula:

Where:

- значение температуры разогрева ПАЭ на волноводе взятой по номограмме Фиг. 5 при соответствующей дине волновода (I) и количестве рассеивателей (N), кроме случая N=0. Остальные обозначения, как в формуле (1).

- the value of the heating temperature of the PAE on the waveguide taken according to the nomogram of FIG. 5 with the corresponding waveguide length (I) and the number of scatterers (N), except for the case N = 0. The remaining notation is as in formula (1).

Therefore, having done a similar job once, it is possible to establish dependences similar (2) for any type of waveguide on which the device is supposed to be used and in the future it is calculated to select the elemental composition of the device for specific conditions of its use.

The acoustic characteristics of the experimental waveguide described above were studied by changing the estimated parameters (amplitude-frequency characteristic of the waveguide, attenuation and dispersion of the waves in the waveguide) transmitted through the waveguide of acoustic pulses specified by the calibrated acoustic pulse generator MSAE-UCA01. The amplitude of the calibrated acoustic pulses was 40 pm ± 5%, and the duration was 100 ns ± 5%. Acoustic signals were recorded and analyzed by AE A-Line 32D system. Since the acoustic path does not undergo significant changes when using the device, the expected results were obtained, showing the absence of changes in the characteristics of the acoustic signals recorded through the waveguide with and without the device.

Thus, the application of the developed technical solution does not lead to a change in the acoustic characteristics of the waveguide and increases the heat transfer efficiency, therefore, it allows to achieve the claimed result.

Information sources

1. Leaird J.D. Acoustic Emission. Training Guide. How to Ensure an Accurate and Valid Acoustic Emission Test / Greensland Publishing Company, USA, 1997, p. 168.

2. Baranov B.M., Gritsenko A.I., Karasevich A.M. et al. Acoustic diagnostics and control at enterprises of the fuel and energy complex / M .: Nauka, 1998 - p. 304.

3. Non-destructive testing: Reference: In 7 t. Under the general. ed. V.V. Klyueva. T. 7: in 2 book. Book 1: V.I. Ivanov, I.E. Vlasov. Acoustic emission method / M.: Mechanical Engineering, 2005, p. 829.

4. Nuspl S.P. Acoustic emission signal collectors / Patent EP No. 0663587, 16.16.1994.

5. Sherwin L.H., Gilmore R.S. Apparatus for focusing and collimating ultrasonic waves / Patent US No. 3934460, 01/27/1976.

6. Feng C.C. Apparatus for acoustic emission detection including a waveguide made of aluminum or beryllium oxide / Patent US No. 4510812, 04.16.1985.

7. Secoy T.C. Acoustic emission waveguide / Patent US No. 5000045, 03/19/1991.

8. Caines M.J. High temperature pressure coupled ultrasonic waveguide / Patent US No. 4392380, 01/21/1983.

9. Morozov S.A., Kovtun C.H., Uralets A.Yu. and other Piezoelectric transducer of acoustic emission / Patent RU No. 94042353, 09.20.1996.

10. Bobylev N.V., Mezintsev E.D., Karpov V.I. Piezoelectric transducer for receiving acoustic emission signals / A.S. SU No. 1270680, 02.22.1985.

11. Vorontsov VB, Smolnikov GV Piezoelectric transducer of waveguide type / A.S. SU No. 1793368, 08.29.1990.

12. Songmei Ping, Zhang Ying, Mosun Guang, Li Wai, Yan Zhijun / Length-adjustable waveguide rod for acoustic emission testing / Patent CN No. 202471655, 03.10.2012.

13. Terhune J.H. Ultrasonic waveguide / Patent US No. 5289436, 02.22.1994.

14. Vorontsov V.B. The method of determining the gas content in liquid metals / Patent RU No. 2052810, 01/10/1992.

15. Vorontsov V.B., Gorchinsky A.V. A device for determining the content of gases in liquid metals / Patent RU No. 2307348, 09/27/2007.

Claims (1)

A universal waveguide of acoustic emission signals with laid on heat-removing elements, characterized in that the heat-dissipating device is collapsible and consists of several components that allow: its installation / dismantling during operation of the waveguide; reorient the device to a new control object / temperature operating mode or other waveguide; to provide compact transportation and storage, as well as manufacturability in manufacturing and maintainability during operation.

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