A kind of calibration device and test method of fiber grating pipeline deformation sensor

Abstract

The application discloses a kind of calibration device and test method of fiber grating pipeline deformation sensor, including fiber grating pipeline expansion strain sensor, expansion cylinder, propelling cone, fixed column, crossbeam, screw, high-precision electronic displacement meter, support frame, first fixed frame plate, second fixed frame plate, bottom plate, contrast femtosecond fiber grating and fiber grating demodulator, fiber grating pipeline expansion strain sensor includes femtosecond fiber grating, flexible sensitization structure, first mounting block, second mounting block and iron wire;Expansion cylinder is used to simulate pipeline, fiber grating pipeline expansion strain sensor is assembled to simulate pipeline, and the expansion strain of simulated pipeline can be monitored;Based on the characteristics of fiber grating structure and fiber grating multiplexing technology, fiber grating pipeline expansion strain sensor can realize the distributed monitoring of pipeline expansion state, and the expansion strain of simulated pipeline is measured and monitored in real time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensing monitoring, and particularly relates to a calibration device and a test method of an optical fiber grating pipeline deformation sensor. BACKGROUND

[0002] Pipeline deformation monitoring is very important in major equipment and fluid transportation fields. Through real-time monitoring of deformation, changes in fluid flow rate, pressure and flow can be reflected, and abnormal changes and deformation can be found in time, which plays a crucial role in safety evaluation and operation and maintenance of the equipment, and helps to optimize the design of the pipeline system. At present, pipeline deformation measurement technology is developing and progressing. In the early stage, artificial visual inspection and periscope monitoring methods were often used to monitor the pipeline condition. Using simple tools for pipeline monitoring has the advantages of convenience, speed, low cost, etc., and has been widely used in pipeline detection. However, the monitoring of the pipeline is mainly concentrated after the accident or after the problem occurs, which causes a certain degree of lag. In addition, the traditional pipeline monitoring method relies heavily on the working experience of the staff, and the monitoring equipment used is mostly expensive and not convenient to carry. With the continuous progress of monitoring technology, pipeline monitoring has been transferred from manual to intelligent machines.

[0003] At present, the main methods of pipeline deformation monitoring at home and abroad include pipeline closed-circuit television method, negative pressure wave method, infrared thermal imaging method, and some methods relying on acoustic principles for monitoring. However, these methods have limitations, such as limited measurement distance, high equipment price, inaccurate measurement, difficult installation, etc., which are difficult to meet the needs of modern industry for high-precision, real-time measurement and possible missed detection. The known pipeline deformation detectors can be roughly divided into three types: the first type is an aluminum disc type deformation detector, which has the advantages of simple structure and good passability, and the disadvantages of only recording the maximum deformation and low measurement accuracy. This kind of detector is still widely used in internal detection process because of its high passability, low risk and low cost. The second type is an angle encoding type multi-channel deformation detector, which has the advantages of high radial detection accuracy and good passability, and the disadvantage of relatively high cost. This kind of detector has become the most commonly used type of deformation detector in pipeline deformation detection because of its high detection accuracy and high passability. The third type is a strain type deformation detector, which has the advantages of simple structure and high passability, but this technology has not been truly applied to industrial site detection. Based on the basic principle of optical fiber grating, a strain type deformation method is provided, which provides a calibration device and a test method of an optical fiber grating pipeline deformation sensor, which can greatly improve the radial detection accuracy. SUMMARY

[0004] In view of the prior art deficiencies, the present application provides a kind of calibration device and test method of fiber grating pipeline deformation sensor, fiber grating pipeline deformation sensor is assembled to pipeline, the expansion strain of pipeline can be monitored, based on its structural characteristics and fiber grating multiplexing technology, fiber grating pipeline deformation sensor can realize the distributed monitoring of pipeline expansion state, realize the real-time measurement and monitoring of pipeline deformation.This technology has the characteristics of high precision, long-distance transmission and strong anti-interference ability, greatly improves the accuracy and reliability of pipeline deformation measurement.

[0005] To solve the above problems, the technical scheme provided by the present application is as follows:

[0006] The present application provides a kind of calibration device of fiber grating pipeline deformation sensor, including deformation transmission component and deformation measurement component;The deformation transmission component includes expansion cylinder (7), push cone (8), fixed column (9), crossbeam (10), screw rod (11), first fixed frame plate (14), second fixed frame plate (15) and bottom plate (16);The third connecting threaded hole group (9-1) of the fixed pile (9) is assembled with the threaded hole of the bottom plate (16) by 9 bolts, the first connecting threaded hole group (7-1) of the lower end of the expansion cylinder (7) is assembled with the fourth connecting threaded hole group (9-2) of the side of the fixed column (9) by 4 bolts;The fastening threaded hole group on the right side of the first fixed frame plate (14) is fixed with the sixth connecting threaded hole group (10-2) on the left side of the crossbeam (10) by four bolts;The fastening threaded hole group on the left side of the second fixed frame plate (15) is fixed with the seventh connecting threaded hole group (10-3) on the right side of the crossbeam (10) by four bolts, the screw rod (11) passes through the fifth connecting threaded hole group (10-1) of the crossbeam (10), and is screwed into the second connecting threaded hole group (8-1) of the push cone (8), so that the screw rod (11), the crossbeam (10) and the push cone (8) are fixed together;

[0007] The deformation measurement component includes fiber grating pipeline expansion strain sensor (6), high-precision electronic displacement meter (12) and support frame (13);The bottom of the support frame (13) and the bottom plate (16) are assembled and fixed together by bolts, the high-precision electronic displacement meter (12) passes through the aperture in the top of the support frame (13), the bottom circular structure of the high-precision electronic displacement meter (12) just contacts the flat circular platform on the upper end of the screw rod (11), and the fiber grating pipeline expansion strain sensor (6) is precisely sleeved on the side of the expansion cylinder (7), for measuring the volume expansion of the expansion cylinder (7).

[0008] In the preferred embodiment of the present application, the fiber grating pipe expansion strain sensor (6) comprises a femtosecond fiber grating (1), a flexible sensitization structure (2), a first mounting block (3), a second mounting block (4) and a wire (5); the fiber at both ends of the femtosecond fiber grating (1) is removed of coating layer and fixed with the flexible sensitization structure (2) in the capillary steel tube groove (2-2) at both ends by an adhesive; the grating region of the femtosecond fiber grating (1) is suspended and arranged at the middle position of the sensitization structure (2-1) of the flexible sensitization structure (2), and the femtosecond fiber grating (1) needs to be pre-stretched before being fixed with the adhesive; the first mounting block (3) and the second mounting block (4) are inserted from the thinner end of the flexible sensitization structure (2), the cavities of the first mounting block (3) and the second mounting block (4) are in a stepped structure, and the flexible sensitization structure (2) is limited; the first mounting block (3) and the second mounting block (4) are connected with the wire (5) through the two groups of through holes of the first mounting block (3) and the second mounting block (4), and are fixed by the four groups of wire fastening screw holes on the front of the first mounting block (3) and the second mounting block (4) through machine screws.

[0009] In the preferred embodiment of the present application, the expansion cylinder (7) is a cylindrical ring structure, and the first connecting thread hole group (7-1) at the bottom of the expansion cylinder (7) comprises eight thread holes which are uniformly distributed in a circumferential array.

[0010] In the preferred embodiment of the present application, the propelling cone (8) is a circular truncated cone structure, the second connecting thread hole group (8-1) is arranged at the center of the propelling cone (8), and four groups of through holes (8-2) are arranged at the same time to reduce the weight; the radius of the lower end of the propelling cone (8) is smaller than the radius of the expansion cylinder (7) and is in close contact with the expansion cylinder (7).

[0011] In the preferred embodiment of the present application, the fixing column (9) is a cylindrical structure, the third connecting thread hole group (9-1) is processed at the bottom of the fixing column (9), the third connecting thread hole group (9-1) comprises nine through holes which are arranged in a cross shape, and the fourth connecting thread hole group (9-2) is arranged on the side surface of the fixing column (9) in a circumferential array.

[0012] In the preferred embodiment of the present application, the cross beam (10) is a rectangular structure, the fifth connecting thread hole group (10-1) is arranged at the center of the cross beam (10) and connected with the screw rod (11) correspondingly and allows the screw rod (11) to pass through; the sixth connecting thread hole group (10-2) and the seventh connecting thread hole group (10-3) are uniformly distributed on the left and right sides of the cross beam (10).

[0013] The support frame (13) is provided with a hole above the support frame (13) to clamp the high-precision electronic displacement meter (12), and the height and angle can be adjusted.

[0014] In an embodiment of the present application, the deformation measurement part assembly comprises a contrast femtosecond fiber grating (17) and a fiber grating demodulator (18); the contrast femtosecond fiber grating (17) is wound around the expansion cylinder (7) for one turn and is fixed at the intersection point by using quick-drying AB glue; the femtosecond fiber grating (1) of the fiber grating pipeline expansion strain sensor (6), the contrast fiber grating (17) and the fiber grating demodulator (18) are connected by using a jumper; the fiber grating demodulator (18) saves data in real time, so as to test the strain response performance of the fiber grating pipeline expansion strain sensor (6) and the contrast fiber grating (17) and the sensitivity difference between them, and complete the calibration test of the fiber grating pipeline deformation sensor by comparing the response performance of the fiber grating pipeline expansion strain sensor (6) and the contrast fiber grating (17).

[0015] The present application provides a kind of calibration test method of fiber grating pipeline deformation sensor, is realized by using the calibration device of fiber grating pipeline deformation sensor of above-mentioned embodiment, wherein, including the following steps:

[0016] Step 1, after calibration device assembly is completed, fixed stake (9) is fixed at the bottom of calibration device, and expansion cylinder (7) and propelling cone (8) connected with fixed stake (9) do not move relative again after assembly correction is completed;First fixed frame plate (14) is fixed at one side of calibration device, and second fixed frame plate (15) is fixed at the other side of calibration device, and beam (10) and screw rod (11) on beam (10) connected with frame plate do not move relative again after assembly and adjustment are completed;

[0017] Step 2, when rotating propelling cone (8), displacement feed amount changes, the measuring rod of high-precision electronic displacement meter (12) is always in contact with the upper platform of screw rod (11), the indication of high-precision electronic displacement meter (12) starts to change, and the displacement change amount of propelling cone (8) sinking can be displayed;Expansion cylinder (7) starts to expand uniformly to the periphery, since the structure characteristics of propelling cone have been calibrated, therefore, the relationship between feed amount and length change amount of expansion cylinder (7) can be inferred according to geometric and mechanical formula, and then the volume expansion change amount of expansion cylinder (7) is obtained;

[0018] Step 3, the volume change of the expansion cylinder (7) is transmitted as the strain of the iron wire 5, a contrast femtosecond fiber grating (17) is arranged, is horizontally wound on one circle of the expansion cylinder (7), is fixed at the intersection point by using quick-drying AB glue, can reflect the deformation expansion amount of one circle of the expansion cylinder (7), the fiber grating pipeline expansion strain sensor (6) is always close to the expansion cylinder (7), the fiber grating center wavelength is offset under the influence of external strain, and the corresponding relationship between displacement feed amount, pipeline volume deformation expansion amount and fiber grating wavelength change amount can be established, so that calibration can be carried out; the whole calibration test scheme is in a laboratory constant temperature environment, the materials contacted by the fiber grating pipeline expansion strain sensor (6) and the contrast fiber grating (17) are the same, and the influence of temperature on the two can be eliminated;

[0019] Step 4, the femtosecond fiber grating (1) of the fiber grating pipeline expansion strain sensor (6), the contrast fiber grating (17) and the fiber grating demodulator (18) are connected by using a jumper, the high-precision electronic displacement meter (12) is adjusted to be zero at the position where the expansion cylinder (7) just starts to deform, the high-precision electronic displacement meter (12) is set from 0mm to-1mm, then-0.1mm, -0.2mm, -0.3mm, -0.4mm, -0.5mm, -0.6mm, -0.7mm, -0.8mm, -0.9mm, -1.0mmf are kept for at least 30s respectively, so that a stable test effect can be achieved, and the fiber grating demodulator (18) is used to save data in real time, so as to test the strain response performance of the fiber grating pipeline expansion strain sensor (6) and the contrast fiber grating (17) and the sensitivity difference between them; the response performance of the fiber grating pipeline expansion strain sensor (6) and the contrast fiber grating (17) is tested, and the fiber grating pipeline deformation sensor calibration test is completed.

[0020] Compared with the prior art, the embodiment of the present application provides a kind of calibration device and test method of fiber grating pipeline deformation sensor, with the following beneficial effects:(1), fiber grating pipeline expansion strain sensor is designed on the sensitization structure, it plays the effect of sensitization, the deformation of one circle on the pipeline section is concentrated on the flexible sensitization structure of sensor, can better monitor the strain caused by pipeline expansion change.(2), the simulation pipeline expansion device structure of the present application is simple, the expansion amount information of pipeline is converted into the change of push rotating cone feed amount, the vague expansion amount change is expressed by relatively intuitive digital change, to realize the measurement of simulation pipeline expansion.(3), higher accuracy, the present application uses low scale division value ruler to measure, can more accurately control how much feed amount, get more actual measurement calibration result. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings needed to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description only some of the embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0022] Figure 1 The overall structure schematic diagram of the calibration device of the fiber grating pipeline deformation sensor provided by the embodiment of the application.

[0023] Figure 2 The rear view of the calibration device of the fiber grating pipeline deformation sensor provided by the embodiment of the application.

[0024] Figure 3 The schematic diagram of measuring the volume expansion of the simulated pipeline by the calibration device of the fiber grating pipeline deformation sensor provided by the embodiment of the application.

[0025] Figure 4 The schematic diagram of the arrangement of the fiber grating and the deformation sensor in the actual calibration experiment of the calibration device of the fiber grating pipeline deformation sensor provided by the embodiment of the application.

[0026] Figure 5 The partial structure section schematic diagram of the fiber grating pipeline expansion strain sensor with a sensitization effect for measuring the volume expansion of the pipeline provided by the embodiment of the application.

[0027] Figure 6 The overall schematic diagram of the fiber grating pipeline expansion strain sensor with a sensitization effect for measuring the volume expansion of the pipeline provided by the embodiment of the application.

[0028] Figure 7 The structure schematic diagram of the sensitization structure provided by the embodiment of the application.

[0029] Figure 8 The structure schematic diagram of the first mounting block provided by the embodiment of the application.

[0030] Figure 9 The structure schematic diagram of the expansion cylinder provided by the embodiment of the application.

[0031] Figure 10 The structure schematic diagram of the propulsion cone provided by the embodiment of the application.

[0032] Figure 11 The structure schematic diagram of the fixed column provided by the embodiment of the application.

[0033] Figure 12 The structure schematic diagram of the cross beam provided by the embodiment of the application.

[0034] Figure 13 The fiber grating and pipe expansion strain sensor obtained by the pipe volume expansion calibration experiment provided by the embodiment of the application are compared with each other.

[0035] Figure 14 The repeatability experiment data graph obtained by the pipe volume expansion calibration experiment provided by the embodiment of the application.

[0036] BRIEF DESCRIPTION OF DRAWINGS: femtosecond fiber grating 1, flexible sensitization structure 2, first mounting block 3, second mounting block 4, iron wire 5, fiber grating pipe expansion strain sensor 6, expansion cylinder 7, push cone 8, fixed column 9, crossbeam 10, screw rod 11, high-precision electronic displacement meter 12, support frame 13, first fixed frame plate 14, second fixed frame plate 15, bottom plate 16, comparison femtosecond fiber grating 17, fiber grating demodulator 18. Flexible sensitization structure 2-1, U-shaped groove 2-2, cavity 3-1, through hole group 3-2, iron wire fastening thread hole group 3-3, first connecting thread hole group 7-1, second connecting thread hole group 8-1, through hole group 8-2, third connecting thread hole group 9-1, fourth connecting thread hole group 9-2, fifth connecting thread hole group 10-1, sixth connecting thread hole group 10-2, seventh connecting thread hole group 10-3. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person skilled in the art without creative work fall within the protection scope of the application. In the description of the embodiment structure or mounting position or direction of parts, “up”, “down”, “front”, “back”, “left”, “right” and the like are based on the orientation of the given drawings, and they are only used for convenience of description and distinguishing the relative positions of the parts or directions, and do not represent the orientation of the calibration device or parts in use.

[0038] In recent years, fiber grating sensing technology has developed rapidly. Light is used as a sensing output signal, the signal is stable and anti-interference, and the signal can be transmitted over a long distance with little attenuation. The stability and durability of the sensor are good, and the sensor is very suitable for long-term and real-time safety monitoring. The sensor has a wide application prospect in the field of operation and maintenance safety monitoring of major projects. With the development of science and technology, pipe deformation measurement technology is gradually applied to practical engineering. The embodiment of the application provides a new pipe expansion measurement device and measurement method, and aims to solve the technical problems of complex structure, resource waste, inconvenient installation and low precision in the current pipe measurement field.

[0039] Specifically, as shown in Figure 1 , Figure 2 , Figure 3 and Figure 4 , the embodiment of the present application provides a kind of calibration device of fiber grating pipeline deformation sensor, including deformation transmission part component and deformation measurement part component.Deformation transmission part component includes expansion cylinder 7, propelling cone 8, fixed column 9, crossbeam 10, screw rod 11, first fixed frame plate 14, second fixed frame plate 15 and bottom plate 16.The third connecting threaded hole group 9-1 of fixed pile 9 is assembled with the threaded hole of bottom plate 16 by 9 bolts, and the first connecting threaded hole group 7-1 of the lower end of expansion cylinder 7 is assembled with the fourth connecting threaded hole group 9-2 of the side of fixed column 9 by 4 bolts.The fastening threaded hole group on the right side of first fixed frame plate 14 is fixed with the sixth connecting threaded hole group 10-2 on the left side of crossbeam 10 by four bolts.The fastening threaded hole group on the left side of second fixed frame plate 15 is fixed with the seventh connecting threaded hole group 10-3 on the right side of crossbeam 10 by four bolts, screw rod 11 is passed through the fifth connecting threaded hole group 10-1 of crossbeam 10, and is screwed into the second connecting threaded hole group 8-1 of propelling cone 8, so that screw rod 11, crossbeam 10 and propelling cone 8 are fixed together.Expansion cylinder 7 of the embodiment simulates pipeline.

[0040] Deformation measurement part component includes fiber grating pipeline expansion strain sensor 6, high-precision electronic displacement meter 12 and support frame 13.The bottom of support frame 13 and bottom plate 16 are assembled and fixed together by bolts, high-precision electronic displacement meter 12 is passed through the aperture in the top of support frame 13, and the bottom circular structure of high-precision electronic displacement meter 12 just contacts the flat circular platform on the upper end of bolt 11, fiber grating pipeline expansion strain sensor 6 is precisely sleeved on the side of expansion cylinder 7, and is used for measuring the volume expansion of expansion cylinder 7.

[0041] As Figure 5 , Figure 6 , Figure 7 and Figure 8As shown, the fiber grating pipe expansion strain sensor 6 has two optical fibers drawn from both ends, which are used to measure the volume expansion of the pipe. The fiber grating pipe expansion strain sensor 6 includes a femtosecond fiber grating 1, a flexible sensitization structure 2, a first mounting block 3, a second mounting block 4, and a wire 5. The portions of the optical fiber at both ends of the femtosecond fiber grating 1 are removed of the coating layer and fixed in the grooves 2-2 of the capillary steel pipes at both ends of the flexible sensitization structure 2 with an adhesive, preferably epoxy resin. The grating region of the femtosecond fiber grating 1 is suspended and arranged at the middle position of the sensitization structure 2-1 of the flexible sensitization structure 2, and the femtosecond fiber grating 1 needs to be pre-stretched before being fixed with the adhesive. The first mounting block 3 and the second mounting block 4 are inserted from the thinner end of the flexible sensitization structure 2, and the cavities of the first mounting block 3 and the second mounting block 4 are in a stepped structure, which serves as a limiting function for the flexible sensitization structure 2. The first mounting block 3 and the second mounting block 4 are connected between the wire 5 through the two through-hole groups of the first mounting block 3 and the second mounting block 4, and are fixed by the four wire fastening screw hole groups on the front surface of the first mounting block 3 and the second mounting block 4 through machine screws. Referring to Figure 8 , the first mounting block 3 has a cavity 3-1 and two through-hole groups 3-2 on the side surface, and two wire fastening screw hole groups 3-3 on the front surface. The first mounting block 3 and the second mounting block 4 are similar or identical in structure.

[0042] The fiber grating pipe expansion strain sensor 6 is installed and fixed: the length and angle of the wire 5 are adjusted, the sensor mounting block is inserted, and the fastening machine screws on the front surface of the mounting block are adjusted. After the installation and assembly are completed, the installation position of the sensor needs to be adjusted to ensure that it is in a horizontal state and closely adheres to the surface of the pipe. Then, the angle and position of the two fixed frame plates are adjusted to ensure that the center of the circular platform at the bottom of the screw rod 11 and the center of the advancing cone 8 are in the same vertical direction, and the cross beam 10 and the advancing cone 8 are both in a horizontal direction without change. The opening angle and length of the support frame 13 ensure that the high-precision electronic displacement meter 12 is in a vertical direction, and the top end of the circular structure at the bottom of the high-precision electronic displacement meter 12 is located at the center position of the circular platform of the screw rod 11. The cross beam 10, the screw rod 11, the high-precision electronic displacement meter 12, the first fixed frame plate 14, and the second fixed frame plate 15 do not move relative to each other after being assembled and calibrated.

[0043] The working principle of the fiber Bragg grating (FBG) pipe expansion strain sensor 6 is as follows: The FBG pipe expansion strain sensor is placed on the pipe. To ensure a tight connection between the sensor and the pipe and to better transmit strain, the length of the iron wire 5 and the tightness of the nut screws can be adjusted for better fixation and fit to the pipe. When the pipe expands, the resulting radial force causes the iron wire to deform. The FBG sensor mounted on the pipe is affected by external strain, causing a shift in the center wavelength of the FBG. The change in wavelength of the FBG sensor reflects the strain of the iron wire. Calibration tests are conducted on the sensor in the laboratory. The pipe equipped with the FBG sensor is fixed in place, and the volume change of the pipe is varied using a calibration device to obtain the wavelength shift under different expansion states. Data processing is used to obtain the relationship between the pipe volume change and the wavelength shift of the FBG pipe expansion strain sensor. In practical applications, the actual wavelength shift of the FBG pipe expansion strain sensor can be used to deduce the pipe volume change state at the location of the FBG pipe expansion strain sensor through the calibrated functional relationship. Based on fiber Bragg grating multiplexing technology, multiple fiber Bragg grating sensors can be arranged along the pipeline axis to perform distributed monitoring of the entire pipeline status.

[0044] The measurement principle of this invention is as follows:

[0045] When the ambient temperature is constant, for an initial center wavelength of λ B The fiber grating has a wavelength shift Δλ B The relationship between it and the axial strain Δε it experiences is as follows:

[0046]

[0047] Pe is the effective elastic coefficient of the optical fiber, which is approximately 0.22 at room temperature.

[0048] It consists of steel wires fixed to the outer wall of the pipe by precision set screws. Under the action of uniform internal pressure P, the strain ε on the pipe surface... eq A tensile force F is generated on both sides of the sensitization shaft through linear coupling, and the overall equivalent stiffness coefficient k of the calibration device is determined. eq Related to the axial length and the dimensions of the hollow shaft, the expression is:

[0049] F = k eq ·X (2);

[0050] The tensile force F on both sides of the sensitized structure generates an axial displacement ΔX within the structure. Since the sensing wire and the sensitized structure have different equivalent stiffness coefficients, the tensile strain monitored by the FS-FBG sensor can be used to derive the sensor's equivalent strain ε. eq :

[0051]

[0052] where k sen and k st represent the equivalent stiffness coefficients of the sensitized structure and the steel wire respectively. Substituting equation (4) into equation (5), the relationship between the volume change rate of the pipe and the strain of the FS-FBG can be derived as follows:

[0053]

[0054] The theoretical relationship between the volume change of the pipe and the wavelength change of the FBG Δλ B can be obtained from the above equation, and there is a good corresponding relationship between the load F borne by the bolt and the wavelength change of the FBG Δλ B . Before practical application, the FBG pipe expansion strain sensor needs to be further calibrated. The volume change of the pipe is changed by the calibration device, and the wavelength change of the FBG pipe expansion strain sensor is monitored at the same time, so as to establish the measurement function relationship between the volume change and the wavelength change of the FBG Δλ B . In practical application, the pipe state at different positions of the pipe can be inversely calculated according to the wavelength drift of the FBG at the positions and in combination with the measurement function.

[0055] As shown in Figure 9 , the expansion cylinder 7 is a cylindrical annular structure. The first connecting threaded hole group 7-1 at the bottom of the expansion cylinder 7 comprises eight threaded holes which are uniformly distributed in a circumferential array. The bottom end of the expansion cylinder 7 in the embodiment is fixed, and the upper end thereof has four centrally symmetric notches, and a part away from the bottom is also transversely cut, so that the entire expansion cylinder 7 can naturally expand under the action of external force.

[0056] As shown in Figure 10 , the advancing cone 8 is a circular truncated cone structure. The second connecting threaded hole group 8-1 is arranged at the center of the advancing cone 8, and four through hole groups 8-2 are arranged at the same time for weight reduction. The lower end radius of the advancing cone 8 is smaller than the radius of the expansion cylinder 7, and the advancing cone 8 is in close contact with the expansion cylinder 7.

[0057] As shown in Figure 11 , the fixed column 9 is a cylindrical structure. The third connecting threaded hole group 9-1 is processed at the bottom of the fixed column 9, and the third connecting threaded hole group 9-1 comprises nine through holes which are arranged in a cross shape. The fourth connecting threaded hole group 9-2 is arranged on the side surface of the fixed column 9 in a circumferential array.

[0058] As shown in Figure 12As shown, the crossbeam 10 is a cuboid structure, and a fifth connecting threaded hole group 10-1 is arranged at the center of the crossbeam 10, and is connected with the screw rod 11 in a corresponding manner and allows the screw rod 11 to pass through; the left and right sides of the crossbeam 10 are uniformly provided with a sixth connecting threaded hole group 10-2 and a seventh connecting threaded hole group 10-3.

[0059] Figure 2 In combination Figure 1 , the lower end of the screw rod 11 is connected with the propelling cone 8, the threaded part is connected with the crossbeam 10 and is fixed, and the upper end is a flat circular platform. The high-precision electronic displacement meter 12 is composed of an electronic displacement dial and a measuring rod, and the bottom of the measuring rod has a spherical structure. The support frame 13 is generally a rectangular column structure, and a hole is formed at the upper part of the support frame 13 to clamp the high-precision electronic displacement meter 12, and the height and angle can be adjusted. The first fixed frame plate 14 is a cuboid structure, is placed on the left platform, is fixed, and the right side is uniformly provided with threads corresponding to the left side of the crossbeam 10. The second fixed frame plate 15 has the same structure and parameters as the first fixed frame plate 14, and the uniformly distributed threads on the left side correspond to the right side of the crossbeam 10. The fixed bottom plate 16 has the same structure and parameters as the first fixed frame plate 14, and the uniformly distributed threads on the upper side correspond to the fixed lower side.

[0060] After assembly, the position of the high-precision electronic displacement meter 12 can be controlled by adjusting the extension length and angle of the support frame 13. Before the expansion strain measurement starts, the bottom of the high-precision electronic displacement meter 12 needle is in contact with the flat platform on the screw rod 11, and the active range is in the center position of the upper circular platform of the screw rod 11. The propelling cone 8 and the expansion cylinder 7 are always in contact, and appropriate lubricating oil can be applied to ensure that the smoothness of the mutual contact is always unchanged.

[0061] As shown in Figure 3 and Figure 4 , the deformation measurement part assembly includes a contrast femtosecond fiber grating 17 and a fiber grating demodulator 18. The contrast femtosecond fiber grating 17 is wound around the expansion cylinder 7 for one turn, and the intersection is fixed with quick-drying AB glue; the femtosecond fiber grating 1 of the fiber grating pipeline expansion strain sensor 6, the contrast fiber grating 17 and the fiber grating demodulator 18 are connected by using a jumper wire, and the fiber grating demodulator 18 saves data in real time, so as to test the strain response performance of the fiber grating pipeline expansion strain sensor 6 and the contrast fiber grating 17 and the sensitivity difference between them, and complete the fiber grating pipeline deformation sensor calibration test by testing the response performance of the contrast fiber grating pipeline expansion strain sensor 6 and the contrast fiber grating 17.

[0062] The embodiment of the application also provides a calibration test method of a fiber grating pipeline deformation sensor, which is realized by using the calibration device of the fiber grating pipeline deformation sensor in the above embodiment, and includes the following steps:

[0063] Step 1, after the calibration device is assembled, the fixed pile 9 is fixed to the bottom of the calibration device, and the expansion cylinder 7 and the push cone 8 connected with the fixed pile 9 do not move relative to each other after being assembled and corrected; the first fixed frame plate 14 is fixed to one side of the calibration device, and the second fixed frame plate 15 is fixed to the other side of the calibration device, and the cross beam 10 connected with the frame plate and the screw rod 11 on the cross beam 10 do not move relative to each other after being assembled and adjusted;

[0064] Step 2, when the push cone 8 is rotated, the displacement feed amount changes, the measuring rod of the high-precision electronic displacement meter 12 is always in contact with the upper platform of the screw rod 11, the reading of the high-precision electronic displacement meter 12 starts to change, and the displacement change amount of the push cone 8 sinking can be displayed; the expansion cylinder 7 starts to expand uniformly in all directions, and since the structure of the push cone has been calibrated, the relationship between the feed amount and the change amount of the circumference of the expansion cylinder 7 can be inferred according to geometric and mechanical formulas, and then the volume expansion change amount of the expansion cylinder 7 can be obtained;

[0065] Step 3, the volume change amount of the expansion cylinder 7 is transmitted to the strain of the iron wire 5, the comparison femtosecond fiber grating 17 is horizontally wound on one turn of the expansion cylinder 7, and is fixed at the intersection point by using quick-drying AB glue, which can reflect the deformation and expansion amount of one turn of the expansion cylinder 7, the fiber grating pipeline expansion strain sensor 6 always closely contacts the expansion cylinder 7, the center wavelength of the fiber grating is shifted due to the influence of external strain, and then the corresponding relationship between the displacement feed amount, the simulated pipeline volume deformation and expansion amount and the wavelength change amount of the fiber grating can be established, so as to calibrate. The whole calibration test scheme is in a laboratory constant temperature environment, the materials contacted by the fiber grating pipeline expansion strain sensor 6 and the comparison fiber grating 17 are the same, which can eliminate the influence of temperature on the two;

[0066] Step 4, the femtosecond fiber grating 1 of the fiber grating pipeline expansion strain sensor 6, the comparison fiber grating 17 and the fiber grating demodulator 18 are connected by using a jumper, the high-precision electronic displacement meter 12 is adjusted to be zero at the position where the expansion cylinder 7 just starts to deform, the high-precision electronic displacement meter 12 is set from 0 mm to-1 mm, and then is kept at-0.1 mm, -0.2 mm, -0.3 mm, -0.4 mm, -0.5 mm, -0.6 mm, -0.7 mm, -0.8 mm, -0.9 mm and-1.0 mm for at least 30 s respectively, so as to achieve a stable test effect, and the fiber grating demodulator 18 is used to save data in real time, so as to test the strain response performance of the fiber grating pipeline expansion strain sensor 6 and the comparison fiber grating 17 and the sensitivity difference between them; the response performance of the fiber grating pipeline expansion strain sensor 6 and the comparison fiber grating 17 is tested, and the fiber grating pipeline deformation sensor calibration test is completed.

[0067] As Figure 13 andFigure 14 As shown, the fiber grating pipe expansion strain sensor 6 corresponds to the curve of the pipe deformation sensor, and the comparative fiber grating 17 corresponds to the FBG. When the simulated pipe device expands and deforms, the wavelength change amount of the fiber grating pipe expansion strain sensor 6 and the comparative fiber grating 17 is linear to the feed displacement amount, and under the same feed displacement, the wavelength change amount of the fiber grating pipe expansion strain sensor 6 is larger than that of the comparative fiber grating 17. It can be further concluded that under the same strain, the wavelength change amount of the fiber grating pipe expansion strain sensor 6 is larger, and the sensitivity is higher. The test is repeated three times, the error of the test result is small, and in a reasonable interval, to prove the feasibility and rationality of the simulated pipe expansion deformation calibration device and the calibration method.

[0068] Although the present application has been disclosed with the preferred embodiments as above, the above preferred embodiments are not intended to limit the present application, and those skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application is subject to the range defined by the claims.

Claims

1. A calibrating device for fiber Bragg grating pipe deformation sensor, characterized in that, The deformation transmission part assembly includes an expansion cylinder (7), a propelling cone (8), a fixed column (9), a crossbeam (10), a screw rod (11), a first fixed frame plate (14), a second fixed frame plate (15) and a bottom plate (16); the third connecting threaded hole group (9-1) of the fixed column (9) is assembled with the threaded hole of the bottom plate (16) by 9 bolts, the first connecting threaded hole group (7-1) of the lower end of the expansion cylinder (7) is assembled with the fourth connecting threaded hole group (9-2) of the side surface of the fixed column (9) by 4 bolts; the fastening threaded hole group on the right side of the first fixed frame plate (14) is fixed with the sixth connecting threaded hole group (10-2) on the left side of the crossbeam (10) by four bolts; the fastening threaded hole group on the left side of the second fixed frame plate (15) is fixed with the seventh connecting threaded hole group (10-3) on the right side of the crossbeam (10) by four bolts, the screw rod (11) is passed through the fifth connecting threaded hole group (10-1) of the crossbeam (10) and screwed into the second connecting threaded hole group (8-1) of the propelling cone (8), and the screw rod (11), the crossbeam (10) and the propelling cone (8) are fixed together; The deformation measurement part assembly includes a fiber grating pipeline expansion strain sensor (6), a high-precision electronic displacement meter (12) and a support frame (13); the bottom of the support frame (13) and the bottom plate (16) are assembled and fixed together by bolts, the high-precision electronic displacement meter (12) is passed through the aperture in the top of the support frame (13), the bottom circular structure of the high-precision electronic displacement meter (12) just contacts the flat circular table on the upper end of the screw rod (11), and the fiber grating pipeline expansion strain sensor (6) is precisely sleeved on the side surface of the expansion cylinder (7) and used for measuring the volume expansion amount of the expansion cylinder (7).

2. The calibration device of a fiber Bragg grating pipeline deformation sensor according to claim 1, characterized in that, The fiber grating pipeline expansion strain sensor (6) comprises a femtosecond fiber grating (1), a flexible sensitization structure (2), a first mounting block (3), a second mounting block (4) and a wire (5); the fiber grating (1) is fixed with the flexible sensitization structure (2) in the capillary steel tube groove (2-2) at both ends by an adhesive after removing the coating layer at both ends of the fiber grating (1); the fiber grating (1) is suspended and arranged at the middle position of the sensitization structure (2-1) of the flexible sensitization structure (2), and the fiber grating (1) needs to be pre-stretched before being fixed with the adhesive; the first mounting block (3) and the second mounting block (4) are inserted from the thinner end of the flexible sensitization structure (2), the cavities of the first mounting block (3) and the second mounting block (4) are in a stepped structure, and the flexible sensitization structure (2) is limited; the first mounting block (3) and the second mounting block (4) are connected through the two through hole groups of the first mounting block (3) and the second mounting block (4) between the first mounting block (3) and the wire (5), and the four wire fastening screw hole groups on the front of the first mounting block (3) and the second mounting block (4) are fixed by machine screws.

3. The calibration device of a fiber Bragg grating pipeline deformation sensor according to claim 2, characterized in that, The expansion cylinder (7) is a cylindrical ring structure, and the first connecting threaded hole group (7-1) at the bottom of the expansion cylinder (7) comprises eight threaded holes which are uniformly distributed in a circumferential array.

4. The calibration device of a fiber Bragg grating pipeline deformation sensor according to claim 3, characterized in that, The propelling cone (8) is a circular truncated cone structure, the second connecting threaded hole group (8-1) is arranged at the center of the propelling cone (8), and four through hole groups (8-2) are arranged at the same time to reduce the weight; the lower end radius of the propelling cone (8) is smaller than the radius of the expansion cylinder (7), and the propelling cone (8) is in close contact with the expansion cylinder (7).

5. The calibration device of a fiber Bragg grating pipe deformation sensor according to claim 4, characterized in that, The fixed column (9) is a cylindrical structure, the third connecting threaded hole group (9-1) is arranged at the bottom of the fixed column (9), the third connecting threaded hole group (9-1) comprises nine through holes which are arranged in a cross shape, and the fourth connecting threaded hole group (9-2) is arranged on the side of the fixed column (9) in a circumferential array.

6. The calibration device of a fiber Bragg grating pipeline deformation sensor according to claim 5, characterized in that, The cross beam (10) is a rectangular structure, the fifth connecting threaded hole group (10-1) is arranged at the center of the cross beam (10) and connected with the screw rod (11) correspondingly, and the screw rod (11) is allowed to pass through; the sixth connecting threaded hole group (10-2) and the seventh connecting threaded hole group (10-3) are uniformly distributed on the left and right sides of the cross beam (10).

7. The device for calibrating a fiber Bragg grating pipe deformation sensor according to claim 6, characterized in that, The support frame (13) is provided with apertures above to clamp the high-precision electronic displacement meter (12), and the height and angle can be adjusted.

8. The device for calibrating a fiber Bragg grating pipe deformation sensor according to claim 7, characterized in that, The deformation measuring part assembly comprises a contrast femto fiber grating (17) and a fiber grating demodulator (18); the contrast femto fiber grating (17) is wound on the inflation cylinder (7) for one turn and is fixed at the intersection point by using quick-drying AB glue; the femto fiber grating (1) of the fiber grating pipeline inflation strain sensor (6), the contrast femto fiber grating (17) and the fiber grating demodulator (18) are connected by using a jumper; the fiber grating demodulator (18) saves data in real time, so as to test the strain response performance of the fiber grating pipeline inflation strain sensor (6) and the contrast femto fiber grating (17) and the sensitivity difference between them; the response performance of the fiber grating pipeline inflation strain sensor (6) and the contrast femto fiber grating (17) is compared through the test, and the fiber grating pipeline deformation sensor calibration test is completed.

9. A method for calibrating a fiber grating pipeline deformation sensor, which is implemented by using the calibration device for a fiber grating pipeline deformation sensor according to claim 8, characterized in that, The method comprises the following steps: Step 1, after the calibration device is assembled, the fixed column (9) is fixed at the bottom of the calibration device, and the inflation cylinder (7) and the advancing cone (8) connected with the fixed column (9) do not move relative to each other after being assembled and corrected; the first fixed frame plate (14) is fixed on one side of the calibration device, the second fixed frame plate (15) is fixed on the other side of the calibration device, and the cross beam (10) and the screw rod (11) on the cross beam (10) connected with the frame plates do not move relative to each other after being assembled and adjusted; Step 2, when the advancing cone (8) is rotated, the displacement feed amount changes, the measuring rod of the high-precision electronic displacement meter (12) is always in contact with the upper platform of the screw rod (11), the indication of the high-precision electronic displacement meter (12) starts to change, and the displacement change amount of the advancing cone (8) can be displayed; the inflation cylinder (7) starts to uniformly expand to the surrounding, and since the structure characteristics of the advancing cone have been calibrated, the relationship between the feed amount and the change amount of the circumference of the inflation cylinder (7) can be inferred according to geometric and mechanical formulas, and then the inflation cylinder (7) volume expansion change amount information can be obtained; Step 3, the volume change amount of the inflation cylinder (7) is transmitted as the strain of the iron wire 5, the contrast femto fiber grating (17) is arranged and wound on the inflation cylinder (7) for one turn, and is fixed at the intersection point by using quick-drying AB glue, which can reflect the deformation expansion amount of the inflation cylinder (7) for one turn; the fiber grating pipeline inflation strain sensor (6) always closely contacts the inflation cylinder (7) and is affected by external strain, the central wavelength of the fiber grating is offset, and then the corresponding relationship among the displacement feed amount, the pipeline volume deformation expansion amount and the fiber grating wavelength change amount can be established, so as to calibrate; the whole calibration test scheme is in a laboratory constant temperature environment, the materials contacted by the fiber grating pipeline inflation strain sensor (6) and the contrast femto fiber grating (17) are the same, and the influence of temperature on the two can be eliminated; Step 4, the femto fiber grating (1) of the fiber grating pipe expansion strain sensor (6), the contrast femto fiber grating (17) and the fiber grating demodulator (18) are connected by jumper, the high-precision electronic displacement meter (12) is adjusted to zero at the position where the expansion cylinder (7) just starts to deform, the high-precision electronic displacement meter (12) is set from 0mm to-1mm, then respectively at-0.1mm, -0.2mm, -0.3mm, -0.4mm, -0.5mm, -0.6mm, -0.7mm, -0.8mm, -0.9mm, -1.0mm f respectively keep at least 30s, to achieve a stable test effect, and the fiber grating demodulator (18) is used to save data in real time, so as to test the strain response performance of the fiber grating pipe expansion strain sensor (6) and the contrast femto fiber grating (17) and the sensitivity difference between each other; through the response performance test of the fiber grating pipe expansion strain sensor (6) and the contrast femto fiber grating (17), the fiber grating pipe deformation sensor calibration test is completed.

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