Fiber Bragg grating angle type three-way joint meter based on equal-strength beam theory

Abstract

The invention belongs to the technical field of engineering geological disaster monitoring, and discloses a fiber bragg grating angle type three-way joint meter based on an equal-strength beam theory. The fiber bragg grating angle type three-way joint meter is mainly composed of a guide rail type shell, a connecting rod, a beam fixing connecting piece, a positioning fixing piece, a constant-strength cantilever beam, a guide steel ball and an optical fiber sensing unit. Through an integrated fiber grating sensing technology, the joint meter can accurately measure displacement changes of a crack in three directions of opening and closing, shearing and settling. According to the design, the deformation characteristic of the hyperelastic equal-strength beam is fully utilized, the precision and response speed of crack monitoring are remarkably improved, it is ensured that efficient and accurate crack displacement monitoring can be achieved in various complex structures, and wide application potential and excellent monitoring performance are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of engineering geological disaster monitoring, and relates to a fiber Bragg grating angle-type three-way crack meter based on equal-strength beam theory. Background Art

[0002] The peripheral joint is located between the concrete face plate and the toe plate, and is the most sensitive and leak-prone area in a concrete face rockfill dam. The deformation of this area directly affects the safety of the concrete face plate and toe plate water-stopping structure. Therefore, it is of great significance to evaluate the anti-seepage effect of the rockfill dam and judge the overall safety of the dam body.

[0003] At present, the three-dimensional joint meter has become the main tool for monitoring the deformation of the joints around the concrete face rockfill dam. Its sensitivity and measurement accuracy directly determine the accuracy of deformation calculation. However, the existing three-dimensional joint meters generally have problems such as complex structure, large measurement error, and susceptibility to external disturbance. Therefore, the development of an efficient, accurate and externally resistant three-dimensional joint meter has become an urgent need to ensure the structural safety and anti-seepage effect of the concrete face rockfill dam. Summary of the invention

[0004] In view of the existing problems, the present invention provides a fiber Bragg grating angle three-axis crack meter based on equal strength beam theory.

[0005] The technical solution of the present invention:

[0006] A fiber Bragg grating angle-type three-dimensional crack meter based on the equal-strength beam theory includes a guide rail housing, a connecting rod, a beam fixing connector, a positioning fixture, an equal-strength cantilever beam, a guide steel ball, and a fiber optic sensing unit. The device can accurately monitor the changes of cracks in the three directions of opening and closing, shearing, and settlement by integrating fiber Bragg grating sensing technology. The design makes full use of the deformation characteristics of the hyperelastic equal-strength beam to significantly improve the accuracy and reliability of monitoring, ensuring efficient and accurate crack displacement monitoring in various complex structures, and has wide application potential and reliable monitoring performance.

[0007] The guide rail type housing acts as a protective device.

[0008] The connecting rod is used to connect the three guide rail type housings to keep the relative distance between the housings fixed.

[0009] The main function of the beam fixing connector is to fix the equal strength beam and connect the positioning fixture or the connecting rod. At the same time, the part keeps the height of the fixed end of the equal strength beam constant.

[0010] The main function of the positioning fixture is to fix the three-way crack meter on both sides of the crack.

[0011] The equal-strength cantilever beam adopts a variable-section design and is made of nickel-titanium alloy.

[0012] The guide steel ball is fixed on the free end of the equal strength beam.

[0013] The optical fiber sensing unit is a passive filter device having the advantages of high sensitivity, high resolution and resistance to electromagnetic interference.

[0014] Furthermore, the seam meter includes a guide rail housing, a connecting rod, a beam fixing connector, a positioning fixture, an equal-strength cantilever beam, a guide steel ball and an optical fiber sensing unit. The guide rail housing is a circular ring structure with a certain thickness and an open end. A smooth, linear inclined groove is provided on the circular ring surface, and a center hole is provided at the bottom. When the angle-type three-way seam meter moves, the housing rotates accordingly, driving the guide steel balls thereon to rise and fall evenly, thereby causing the displacement change of the free end of the equal-strength beam, resulting in the shift of the center wavelength of the optical fiber sensing unit. In addition, the guide rail housing also serves as a protective device. The connecting rod is used to connect the three guide rail housings to keep the relative distance between the housings fixed, while ensuring that the housings are connected to each other to achieve overall coordinated changes. The beam fixing connector is a rod with two fixed ends, one end of the rod is a fixed end vertically upward with the rod, and the fixed end has a notch, and the other end of the rod is located in a column vertically downward with the rod, and its main function is to fix the equal strength beam and connect the positioning fixture or connecting rod, to ensure that the equal strength beam and the positioning fixture or connecting rod are relatively stationary and do not rotate with the shell. At the same time, this part keeps the fixed end height of the equal strength beam constant, so as to accurately measure the rotation angle of the shell. The main function of the positioning fixture is to fix the three-way crack meter on both sides of the crack. There are two types of positioning fixings. The first type of positioning fixings is an L-shaped structure in cross section, consisting of a bottom fixing end that cooperates with the bottom of the guide rail type housing and a vertical end that is an integral structure with the bottom fixing end, and a center hole that is consistent with the bottom of the guide rail type housing is opened on the bottom fixing end; the second type of positioning fixings is composed of a bottom fixing plate and an L-shaped cross-section structural member; wherein a cylindrical protrusion is provided at the center position of the bottom fixing plate; the L-shaped cross-section structural member is composed of a bottom fixing end and a vertical end that is integrally formed therewith, and the bottom fixing end cooperates with the bottom of the guide rail type housing, and is provided with a through hole corresponding to the center hole of the bottom of the guide rail type housing. A circular through hole is provided at the center of the vertical end, and the cylindrical protrusion of the bottom fixing plate cooperates with the circular through hole of the vertical end. This structure enables the L-section structural member to rotate around the cylindrical protrusion in a plane while limiting its displacement; two guide rail housings in the three-way joint meter are fixed on both sides of the crack, one guide rail housing is fixed on a first positioning fixture, and the other guide rail housing is fixed on a second positioning fixture, and the two directions are perpendicular to each other; the third guide rail housing is connected to the two fixed guide rail housings through connecting rods; the positioning fixture allows the three-way joint meter to rotate around the beam fixing connector and the column on the bottom fixing plate in the plane where the crack is located, that is, the xy plane, but limits its displacement in the x, y and z directions to ensure the stability of the measurement. The equal-strength cantilever beam adopts a variable cross-section design, is made of nickel-titanium alloy, is triangular in shape, and its thickness is much smaller than its length and width; the equal-strength cantilever beam is inserted into the notch at the fixed end of the beam fixing connector as a fixed end; this design ensures that when the equal-strength beam is subjected to concentrated force at the free end, the strain at any position remains equal, thereby facilitating optical fiber monitoring.The guide steel ball is fixed on the free end of the equal strength beam. When the crack expands, the positioning fixture moves accordingly, causing the angle between the guide rail housing and the positioning fixture and the connecting rod to change. The guide steel ball moves up and down along the inclined groove of the guide rail housing, and drives the free end of the equal strength cantilever beam to produce displacement changes, causing the equal strength cantilever beam to bend, resulting in changes in the central wavelength of the optical fiber sensing unit attached thereto. By monitoring the strain on the surface of the equal strength beam through the optical fiber sensing unit, the development of the crack can be quantitatively characterized. The optical fiber sensing unit is a passive filter device with the advantages of high sensitivity, high resolution and anti-electromagnetic interference, and is suitable for monitoring multi-dimensional parameters such as structural deformation, stress and temperature.

[0015] Furthermore, the inclined groove on the guide rail housing is smooth and linear, and the inclined groove is at an angle of 30 degrees to the bottom surface of the guide rail housing, and the opening angle is 180 degrees. The guide steel ball moves in the inclined groove, and due to the limitation of the diameter of the guide steel ball, its effective movement angle is 150 degrees. In order to prevent the guide steel ball from slipping out of the inclined groove, the housing is designed to be a thicker structure, so as to ensure that the force direction of the steel ball is always along the diameter direction, and the stability and accuracy of the measurement are guaranteed. The connecting rod is used to connect the three guide rail housings, so that the housings are linked to each other, and no unmonitored relative displacement occurs, thereby achieving overall consistency of movement changes. The main function of the beam fixing connector is to fix the equal strength cantilever beam and connect it to the connecting rod or the positioning fixture, so that the equal strength beam and the connecting rod or the positioning fixture remain relatively stationary and do not rotate with the rotation of the guide rail housing. At the same time, the structure ensures that the height of the fixed end of the equal strength beam is constant, so that the rotation angle of the guide rail housing can be accurately measured. The positioning fixture is mainly used for initial positioning to clarify the initial position of the fixed point of the crack meter on both sides of the crack. In addition, the positioning fixture allows the three-way joint meter to rotate around the beam fixing connector and the cylinder on the positioning fixture in the plane where the crack is located, that is, the xy plane, but limits its displacement in the x, y and z directions to ensure the stability of the measurement. The equal strength cantilever beam adopts a variable cross-section design and is made of nickel-titanium alloy, so that when the beam body is subjected to concentrated force at the free end, the strain at any position is equal. This design greatly improves the efficiency and accuracy of optical fiber monitoring, and at the same time provides a reliable basis for the quantitative characterization of crack development conditions. The guide steel ball is fixed to the free end of the equal strength cantilever beam. When the crack expands, the angle of the joint meter changes, and an angle change is formed between the connecting rod and the guide rail housing. Since the beam fixing connector and the connecting rod remain stationary and fix the equal strength beam, the guide steel ball will move up and down along the inclined groove of the housing. This movement causes the displacement change of the free end of the equal strength beam, causing the equal strength beam to bend, resulting in a change in the central wavelength of the optical fiber sensing unit attached thereto. By monitoring the strain change on the beam surface through the optical fiber sensing unit, the development of the crack can be accurately quantified and characterized. The optical fiber sensing unit is a passive filter device with the advantages of high sensitivity, high resolution and anti-electromagnetic interference. The unit is suitable for multi-dimensional monitoring, including parameters such as structural deformation, stress and temperature, providing reliable guarantee for accurate monitoring of engineering cracks.

[0016] Furthermore, the calculation of the fiber Bragg grating angle three-axis seam meter based on the equal strength beam theory includes the following steps:

[0017] S101, accurately measuring the central wavelength of the optical fiber sensing unit and recording its initial value;

[0018] S102, using the difference in the central wavelength of the optical fiber sensing unit and the optical fiber Bragg grating strain theory, calculating the strain of the equal strength beam caused by the angle change between the seam meter guide housing and the connecting rod and the positioning fixture;

[0019] S103, further calculating the angle change between the crack meter housing and the connecting rod and the positioning fixture according to the calculated strain value of the equal strength beam and in combination with its material and sensor structure, thereby reflecting the displacement change of the crack in a specific direction;

[0020] S104, calculating the spatial coordinates of point M' according to the angle variation between the joint meter housing and the connecting rod and the positioning fixture, and combining the spatial coordinates of point M, the initial fixed point of the joint meter, to obtain the displacement variation from point M to point M'.

[0021] Furthermore, in the fiber Bragg grating angle three-axis joint meter based on equal strength beam theory, in S102, the strain calculation formula is as follows:

[0022]

[0023] Where ε is the strain of the equal strength beam, Δλ B is the center wavelength difference of the optical fiber sensing unit, λ B is the initial center wavelength of the optical fiber sensing unit, P e is the effective elastic-optical coefficient of the optical fiber sensing unit.

[0024] Furthermore, in the fiber Bragg grating angle-type three-dimensional seam meter based on equal strength beam theory, in S103, the angle change calculation formula between the guide rail housing and the connecting rod and the positioning fixture is as follows:

[0025] ΔR=kε

[0026] Where ΔR is the angle change between the guide rail housing and the connecting rod and the positioning fixture; k is a coefficient obtained through calibration experiments; ε is the strain of the equal strength beam.

[0027] Furthermore, in the fiber Bragg grating angle three-axis seam meter based on equal strength beam theory, in S104, the displacement change from point M to point M' is calculated as follows:

[0028] In three-dimensional space, a point on the crack is selected as the origin, the direction along the length of the crack is the x-axis, the direction perpendicular to the length of the crack is the y-axis, and the plane perpendicular to the crack is the z-axis. The directions of the x, y and z axes conform to the right-hand coordinate system.

[0029] Point A is fixed on one side of the crack as a fixed reference point to maintain the measurement benchmark; AB and BM are two connecting rods with known and constant lengths, both of which are rigid components, and their lengths and geometric shapes remain unchanged; Point M is fixed on the other side of the crack. As the crack gradually develops, Point M will move to a new position M'.

[0030] It is known that the initial coordinates of point M are (x1, y1, z1) and can be calculated using the following formula:

[0031]

[0032]

[0033] z1=MM xy =ABsin(α)-BM cos(α+β-90°)

[0034] During the crack development process, the fiber optic sensing unit is used to monitor the deformation of the crack in real time. The fiber optic sensing unit captures the strain data of the equal-intensity cantilever beam by measuring the change in the central wavelength in the reflection spectrum, and calculates the strain value based on the strain theory of the fiber Bragg grating.

[0035] Based on the measured strain data, combined with the angle change data between the guide rail housing and the connecting rod, the spatial coordinates are accurately calculated; the spatial coordinate calculation module processes the strain data and the angle change data to obtain the spatial coordinates (x2, y2, z2) of the point M' after the crack develops. The formula is as follows:

[0036]

[0037] z2=M'M' xy =AB'sin(α')-B'M'cos(α'+β'-90°)

[0038] According to the difference in spatial coordinates, the relative displacements Δx, Δy and Δz between point M and point M' can be calculated; among which, the change in the opening and closing direction Δx=x2-x1, the change in the shear direction Δy=y2-y1, and the change in the settlement direction Δz=z2-z1.

[0039] Beneficial effects: The present invention discloses a fiber Bragg grating angle three-dimensional crack meter based on the equal strength beam theory. By integrating fiber Bragg grating sensing technology, the crack meter can accurately measure the changes of cracks in the three directions of opening and closing, shearing and settlement. This design makes full use of the deformation characteristics of the hyperelastic equal strength beam to significantly improve the accuracy and response speed of crack monitoring, ensuring efficient and accurate crack displacement monitoring in various complex structures, with wide application potential and excellent monitoring performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required in the embodiments or the prior art description are briefly introduced below. Obviously, the following drawings show some embodiments of the present invention. For ordinary technicians in this field, other relevant diagrams can also be obtained based on these drawings without creative work.

[0041] Figure 1 It is a monitoring flow chart of a fiber Bragg grating angle-type three-dimensional seam meter based on equal-strength beam theory in an embodiment of the present invention;

[0042] Figure 2 Schematic diagram of the principle of a fiber Bragg grating angle-type three-dimensional seam meter based on the equal-strength beam theory in an embodiment of the present invention; wherein (a) is before point M moves, and (b) is after point M moves;

[0043] Figure 3 Schematic diagram of the structure of a fiber Bragg grating angle-type three-axis seam meter based on the equal-strength beam theory in an embodiment of the present invention;

[0044] Figure 4 It is a schematic diagram of the partial structure of a fiber Bragg grating angle-type three-axis crack meter based on the equal-strength beam theory in an embodiment of the present invention.

[0045] In the figure: 1 rail type housing; 2 connecting rod; 3 beam fixing connecting piece; 4 positioning fixing piece; 5 equal strength cantilever beam; 6 guide steel ball; 7 optical fiber sensing unit. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0047] A fiber Bragg grating angle three-dimensional crack meter based on equal strength beam theory, such as Figure 3 The device shown includes a guide rail housing, a connecting rod, a beam fixing connector, a positioning fixture, an equal-strength cantilever beam, a guide steel ball and a fiber optic sensing unit.

[0048] The rail-type housing acts as a protective device, and has a smooth and linearly designed inclined groove on its side wall and a central hole at its bottom.

[0049] The connecting rod is used to connect the three guide rail type housings to keep the relative distance between the housings fixed.

[0050] The main function of the positioning fixture is to fix the three-way crack meter on both sides of the crack.

[0051] The equal-strength cantilever beam adopts a variable-section design and is made of nickel-titanium alloy.

[0052] The guide steel ball is fixed on the free end of the equal strength beam.

[0053] The optical fiber sensing unit is a passive filter device having the advantages of high sensitivity, high resolution and resistance to electromagnetic interference.

[0054] The present invention monitors the strain change of the equal strength beam through the optical fiber sensing unit, and transmits the monitoring data to the spatial coordinate calculation module for processing. After calculation, the user can view the position change of the positioning fixture M point in the output module, that is, the opening and closing, shearing and settlement of the crack. By integrating the fiber grating sensing technology, the crack meter can accurately measure the changes of the crack in three directions. By integrating the fiber grating sensing technology, the crack meter can accurately measure the changes of the crack in the three directions of opening and closing, shearing and settlement. The design makes full use of the deformation characteristics of the superelastic equal strength beam, significantly improves the accuracy and response speed of crack monitoring, ensures that efficient and accurate crack displacement monitoring can be achieved in various complex structures, and has wide application potential and excellent monitoring performance. The output module has its own crack development analysis strategy, which integrates the opening and closing, shearing and settlement of the crack to realize the intelligent monitoring of the safety situation and dynamic changes of the crack deformation. This strategy makes the evaluation results more accurate, and provides systematic, effective and intelligent monitoring for crack development, further promotes the group prevention and control of geological disasters, and enhances the public safety function of the city.

[0055] Working principle and technical details

[0056] In a specific embodiment, the fiber Bragg grating angle three-axis joint meter based on the equal strength beam theory includes a guide rail housing 1, a connecting rod 2, a beam fixing connector 3, a positioning fixture 4, an equal strength cantilever beam 5, a guide steel ball 6 and an optical fiber sensing unit 7. Among them, the inclined groove on the side wall of the guide rail housing 1 is a smooth and linear design. When the angle three-axis joint meter moves, the housing 1 rotates accordingly, driving the guide steel ball 6 thereon to rise or fall evenly, thereby causing the displacement change of the free end of the equal strength beam 5, resulting in a change in the central wavelength of the optical fiber sensing unit 7. In addition, the guide rail housing 1 also serves as a protective device. The connecting rod 2 is used to connect the three guide rail housings 1 to keep the relative distance between the housings fixed, while ensuring that the housings are connected to each other to achieve overall coordinated changes. The beam fixing connector 3 is a rod with two fixed ends, one end of the rod is a fixed end vertically upward to the rod, the fixed end is provided with a notch, and the other end of the rod is located in a column vertically downward to the rod. It is used to fix the equal strength cantilever beam 5 and connect the positioning fixture 4 or the connecting rod 2, ensuring that the equal strength cantilever beam 5 and the positioning fixture 4 or the connecting rod 2 are stationary and do not rotate with the guide rail housing 1; at the same time, the beam fixing connector 3 keeps the fixed end height of the equal strength cantilever beam 5 constant, so as to accurately measure the rotation angle of the guide rail housing 1. The main function of the positioning fixture 4 is to fix the three-dimensional joint meter on both sides of the crack. The positioning fixture 4 allows the three-dimensional joint meter to rotate around the beam fixing connector 3 and the column on the bottom fixing plate in the plane where the crack is located, that is, the xy plane, but limits its displacement in the x, y and z directions to ensure the stability of the measurement. The equal strength cantilever beam 5 adopts a variable cross-section design, is made of nickel-titanium alloy, is triangular, and its thickness is much smaller than the length and width; the equal strength cantilever beam 5 is inserted into the notch of the fixed end of the beam fixing connector 3 as a fixed end. This design ensures that when the equal strength beam 5 is subjected to concentrated force at the free end, the strain at any position remains equal, thereby facilitating monitoring by the optical fiber sensing unit 7. The guide steel ball 6 is fixed to the free end of the equal strength beam 5. When the crack expands, the positioning fixture 4 moves accordingly, causing the angle between the connecting rod 2 and the positioning fixture 4 and the guide rail housing 1 to change, and the guide steel ball 6 will move up and down along the inclined groove of the housing 1, driving the free end of the equal strength beam 5 to move, causing the equal strength beam 5 to bend. The strain on the surface of the equal strength beam 5 is monitored by the optical fiber sensing unit 7, and the development of the crack can be quantitatively characterized. The optical fiber sensing unit 7 is a passive filter device with the advantages of high sensitivity, high resolution and anti-electromagnetic interference, and is suitable for monitoring multi-dimensional parameters such as deformation, stress and temperature of the structure.

[0057] In a specific embodiment, the fiber Bragg grating angle-type three-dimensional seam meter based on the equal-strength beam theory disclosed by the present invention comprises a guide rail housing 1, a connecting rod 2, a beam fixing connector 3, a positioning fixture 4, an equal-strength cantilever beam 5, a guide steel ball 6 and an optical fiber sensing unit 7. Specifically, the inclined groove on the guide rail housing 1 is smooth and linear, and the inclined groove is at an angle of 30 degrees to the bottom surface of the guide rail housing 1, and the opening angle is 180 degrees. The guide steel ball 6 moves in the inclined groove, and its effective movement angle is 150 degrees due to the limitation of the diameter of the guide steel ball 6. In order to prevent the guide steel ball 6 from slipping out of the inclined groove, the housing 1 is designed as a thicker structure, so as to ensure that the force direction of the steel ball 6 is always along the diameter direction, thereby ensuring the stability and accuracy of the measurement. The connecting rod 2 is used to connect the three guide rail housings 1, so that the housings are linked to each other, and no unmonitored relative displacement occurs, thereby achieving overall consistent movement changes. The main function of the beam fixing connector 3 is to fix the equal strength cantilever beam 5 and connect it with the connecting rod 2 or the positioning fixture 4, so that the equal strength beam 5 and the connecting rod 2 or the positioning fixture 4 remain relatively still and do not rotate with the rotation of the guide rail housing 1. At the same time, this structure ensures that the height of the fixed end of the equal strength beam 5 is constant, so that the rotation angle of the guide rail housing 1 can be accurately measured. The positioning fixture 4 is mainly used for initial positioning to clarify the initial position of the fixed point of the joint meter on both sides of the crack. In addition, the positioning fixing member 4 is divided into two forms. The first type of positioning fixing member is an L-shaped structure in cross section, which is composed of a bottom fixing end that matches the bottom of the guide rail type housing 1 and a vertical end that is an integral structure with the bottom fixing end, and a center hole that is consistent with the bottom of the guide rail type housing 1 is opened on the bottom fixing end; the second type of positioning fixing member is composed of a bottom fixing plate and an L-shaped cross-section structural member; wherein a cylindrical protrusion is provided at the center position of the bottom fixing plate; the L-shaped cross-section structural member is composed of a bottom fixing end and a vertical end that is integrally formed therewith, the bottom fixing end matches the bottom of the guide rail type housing 1, and is provided with a through hole corresponding to the center hole of the bottom of the guide rail type housing 1; a circular through hole is provided in the center of the vertical end, and the cylindrical protrusion of the bottom fixing plate The protrusion cooperates with the circular through hole at the vertical end, and this structure enables the L-shaped cross-section structural member to rotate around the cylindrical protrusion in the plane while limiting its displacement; the two guide rail housings in the three-way joint meter are fixed on both sides of the crack, one guide rail housing is fixed on the first positioning fixture, and the other guide rail housing is fixed on the second positioning fixture, and the two directions are perpendicular to each other; the third guide rail housing is connected to the two fixed guide rail housings respectively through the connecting rod 2; the positioning fixture 4 allows the three-way joint meter to rotate around the beam fixing connector 3 and the column on the bottom fixing plate in the plane where the crack is located, that is, the xy plane, but limits its displacement in the x, y and z directions to ensure the stability of the measurement. The equal-strength cantilever beam 5 adopts a variable cross-section design, is made of nickel-titanium alloy, is triangular, and its thickness is much smaller than the length and width, so that when the beam body is subjected to concentrated force at the free end, the strain at any position is equal.This design greatly improves the efficiency and accuracy of optical fiber monitoring, and provides a reliable basis for the quantitative characterization of crack development. The guide steel ball 6 is fixed to the free end of the equal-strength cantilever beam 5. When the crack expands, the angle of the crack meter changes, and the angle between the connecting rod 2 and the positioning fixture 4 and the guide rail housing 1 changes. Since the beam fixing connector 3 and the connecting rod 2 and the positioning fixture 4 remain stationary and fix the equal-strength beam 5, the guide steel ball 6 will move up and down along the inclined groove of the guide rail housing 1. This movement causes the displacement change of the free end of the equal-strength beam 5, causing the equal-strength beam 5 to bend. By monitoring the strain change on the beam surface through the optical fiber sensing unit 7, the development of the crack can be accurately quantified. The optical fiber sensing unit 7 is a passive filter device with the advantages of high sensitivity, high resolution and anti-electromagnetic interference. The unit is suitable for multi-dimensional monitoring, including parameters such as structural deformation, stress and temperature, and provides reliable guarantee for accurate monitoring of engineering cracks.

[0058] In a specific embodiment, there are three rail-type housings 1, which are used to monitor the angle changes of the joint meter at three different positions, so that the subsequent spatial coordinate calculation module can perform accurate coordinate calculation. The three rail-type housings 1 have the same structure, and a circular hole is opened in the center of the bottom to facilitate the beam fixing connector 3 to be connected to the connecting rod 2 or the positioning fixture 4 through the hole. A rectangular through hole is opened on the side wall of the housing to form an inclined groove to guide the movement of the steel ball 6. The beam fixing connector 3 adopts a Z-shaped design, one end of which is used to clamp the equal strength beam 5 to ensure that its fixed end does not move; the other end is cylindrical and can pass through the circular hole at the bottom of the housing 1 and realize free rotation therein. This design not only ensures the stability of the equal strength beam 5, but also provides sufficient rotation flexibility. There are three equal strength cantilever beams 5, which adopt a variable cross-section design and are made of nickel-titanium alloy. This design ensures that when the beam body is subjected to concentrated force at the free end, the strain at any position is equal, so that the measurement results are more consistent and reliable. There are three optical fiber sensing units 7, which are respectively attached to the surfaces of the three equal strength beams 5 to monitor their strain changes in real time. These fiber optic sensing units 7 utilize fiber Bragg grating technology to capture the strain information of the beam with high precision, provide data support for crack development and displacement changes, and ensure the monitoring effect of the crack meter and the reliability of the data.

[0059] In a specific embodiment, the calculation includes the following steps

[0060] S101, accurately measuring the central wavelength of the optical fiber sensing unit 7 and recording its initial value;

[0061] S102, using the central wavelength difference of the optical fiber sensing unit 7 and the optical fiber Bragg grating strain theory, the strain of the equal strength beam 5 caused by the angle change between the seam meter guide rail housing 1 and the connecting rod 2 and the positioning fixture 4 is calculated;

[0062] S103, based on the calculated strain value of the equal strength beam 5, combined with its material and sensor structure, further deduce the angle change between the joint meter housing 1 and the connecting rod 2 and the positioning fixture 4, thereby reflecting the displacement change of the crack in a specific direction.

[0063] S104, the spatial coordinates of point M' are calculated based on the angle change between the joint meter housing 1 and the connecting rod 2 and the positioning fixture 4, and the displacement change from point M to point M' is obtained by combining the spatial coordinates of the initial fixed point M of the joint meter.

[0064] In a specific embodiment, in S102, the strain calculation formula is as follows:

[0065]

[0066] Where ε is the strain of the cantilever beam 5 with equal strength, Δλ B is the center wavelength difference of the optical fiber sensing unit 7, λ B is the initial center wavelength of the optical fiber sensing unit 7, P e is the effective elastic-optical coefficient of the optical fiber sensing unit 7.

[0067] In a specific embodiment, in S103, the angle change calculation formula between the guide rail housing 1 and the connecting rod 2 and the positioning fixture 4 is as follows:

[0068] ΔR=kε

[0069] Wherein, ΔR is the angle change between the guide rail housing 1 and the connecting rod 2 and the positioning fixture 4; k is a coefficient obtained through a calibration experiment; and ε is the strain of the equal strength beam 5.

[0070] In a specific embodiment, in S104, the relative displacement change between point M and point M' is calculated as follows:

[0071] In three-dimensional space, a point on the crack is selected as the origin, the direction along the length of the crack is the x-axis, the direction perpendicular to the length of the crack is the y-axis, and the plane perpendicular to the crack is the z-axis. The directions of the x, y and z axes conform to the right-hand coordinate system.

[0072] Point A is fixed on one side of the crack as a fixed reference point to maintain the measurement benchmark. The location of point A is not affected by the crack development process, so the stability and accuracy of the entire measurement system can be ensured. AB and BM are two connecting rods 2 with known and constant lengths. Both are rigid components. Their lengths and geometric shapes remain unchanged, providing reliable geometric constraints for subsequent displacement calculations. Point M is fixed on the other side of the crack. As the crack gradually develops, point M will move to a new position M'.

[0073] It is known that the initial coordinates of point M are (x1, y1, z1) and can be calculated using the following formula:

[0074]

[0075] z1=MM xy =ABsin(α)-BM cos(α+β-90°)

[0076] During the crack development process, the measurement system monitors the deformation caused by the crack in real time using the optical fiber sensing unit 7. The optical fiber sensing unit 7 captures the strain data of the equal strength beam 5 by measuring the change of the central wavelength in the reflection spectrum, and calculates the strain value based on the strain theory of the fiber Bragg grating.

[0077] Based on the measured strain data, combined with the angle change data between the rail housing 1, the connecting rod 2 and the positioning fixture 4, the spatial coordinates can be accurately calculated. The spatial coordinate calculation module can obtain the spatial coordinates (x2, y2, z2) of the point M' after the crack develops by processing the strain data and the angle change data. The formula is as follows:

[0078]

[0079] z2=M'M' xy =AB'sin(α')-B'M'cos(α'+β'-90°)

[0080] According to the difference in spatial coordinates, the relative displacements Δx, Δy and Δz between point M and point M' can be calculated, where the change in the opening and closing direction Δx = x2-x1, the change in the shear direction Δy = y2-y1, and the change in the settlement direction Δz = z2-z1.

[0081] In a specific embodiment, the computing system of the fiber Bragg grating angle three-axis seam meter based on the equal strength beam theory includes:

[0082] The measurement module is closely connected with the spatial coordinate calculation module. Its core components include the optical fiber sensing unit and the optical fiber sensing unit demodulator. The main function of this module is to measure and record the central wavelength change of the optical fiber sensing unit in real time and transmit the data to the spatial coordinate calculation module for processing. As a highly sensitive strain sensing element, the optical fiber sensing unit can accurately reflect the deformation state of the equal strength beam with a slight deviation of its central wavelength.

[0083] The spatial coordinate calculation module is connected to the measurement module and the output module. First, the spatial coordinate calculation module presets a three-dimensional coordinate system and receives the central wavelength data of the optical fiber sensing unit provided by the measurement module. Through complex algorithms, these wavelength data are converted into strain and angle changes, and finally into spatial coordinates in the preset coordinate system. This process converts the strain of the equal-strength beam into the three-dimensional spatial position of the measurement point.

[0084] The output module is connected to the spatial coordinate calculation module and is responsible for receiving and processing the spatial coordinate values ​​output by the spatial coordinate calculation module. Based on these coordinate values, the output module calculates the changes in the three directions of opening and closing, shearing and settlement of the cracks. These data are displayed in precise digital form, providing important support for structural health monitoring and geological disaster early warning.

[0085] In a specific embodiment, the computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the calculation method of the fiber Bragg grating angle three-axis crack meter based on the equal-intensity beam theory.

[0086] In a specific embodiment, the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the processor executes the steps of a calculation method of a fiber Bragg grating angle three-axis crack meter based on equal-intensity beam theory.

[0087] In a specific embodiment, the information data processing terminal is used to implement the calculation system of the fiber Bragg grating angle three-axis crack meter based on the equal-strength beam theory.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the above embodiments have described the present invention in detail, those skilled in the art should understand that they can still modify the technical solutions described in the embodiments, or replace some or all of the technical features therein with equivalents. Such modifications or replacements do not change the essence of the corresponding technical solutions, nor do they exceed the protection scope of the embodiments of the present invention.

Claims

1. A fiber Bragg grating angle three-axis seam meter based on equal strength cantilever beam theory, characterized in that: The fiber Bragg grating angle type three-way seam meter comprises a guide rail type housing, a connecting rod, a beam fixing connecting piece, a positioning fixing piece, an equal strength cantilever beam, a guide steel ball and an optical fiber sensing unit; The guide rail housing is a circular ring structure with a certain thickness and an open end, a smooth, linear inclined groove is opened on the circular ring surface, and a center hole is opened at the bottom; The connecting rod is used to connect the three guide rail type housings to keep the relative distance between the guide rail type housings fixed; The beam fixing connector is used to fix the equal strength cantilever beam and connect the positioning fixture or the connecting rod, ensuring that the equal strength cantilever beam and the positioning fixture or the connecting rod are relatively stationary and do not rotate with the guide rail housing; at the same time, the beam fixing connector keeps the fixed end height of the equal strength cantilever beam constant, thereby accurately measuring the rotation angle of the guide rail housing; The positioning fixture fixes the three-way crack meter on both sides of the crack; The isotropic cantilever beam adopts a variable cross-section design and is made of nickel-titanium alloy; The guide steel ball is fixed to the free end of the equal strength cantilever beam; The optical fiber sensing unit is a passive filter device.

2. The fiber Bragg grating angle three-axis seam meter according to claim 1, characterized in that: The beam fixing connector is a rod with two fixed ends, one end of the rod is a fixed end vertically upward from the rod, the fixed end is provided with a notch, and the other end of the rod is located at a column vertically downward from the rod; The positioning fixing member is divided into two forms. The first type of positioning fixing member is an L-shaped structure in cross section, which is composed of a bottom fixing end that cooperates with the bottom of the guide rail type shell and a vertical end that is an integral structure with the bottom fixing end, and a center hole that is consistent with the bottom of the guide rail type shell is opened on the bottom fixing end; the second type of positioning fixing member is composed of a bottom fixing plate and an L-shaped cross-section structural member; wherein a cylindrical protrusion is provided at the center position of the bottom fixing plate; the L-shaped cross-section structural member is composed of a bottom fixing end and a vertical end integrally formed therewith, the bottom fixing end cooperates with the bottom of the guide rail type shell, and is provided with a through hole corresponding to the center hole of the bottom of the guide rail type shell. A circular through hole is provided at the center of the vertical end, and the cylindrical protrusion of the bottom fixing plate is matched with the circular through hole of the vertical end. This structure enables the L-section structural member to rotate around the cylindrical protrusion in the plane, while limiting its displacement; two guide rail housings in the three-way joint meter are fixed on both sides of the crack, one guide rail housing is fixed on the first positioning fixture, and the other guide rail housing is fixed on the second positioning fixture, and the two directions are perpendicular to each other; the third guide rail housing is connected to the two fixed guide rail housings through connecting rods; the positioning fixture allows the three-way joint meter to rotate around the beam fixing connector and the cylinder on the bottom fixing plate in the plane where the crack is located, that is, the xy plane, but limits its displacement in the x, y and z directions to ensure the stability of the measurement; The equal strength cantilever beam adopts a variable cross-section design and is triangular in shape, and its thickness is much smaller than its length and width; the equal strength cantilever beam is inserted into the notch at the fixed end of the beam fixing connector as a fixed end; The guide steel ball is fixed on the free end of the equal-strength cantilever beam; when the crack expands, the positioning fixture moves accordingly, causing the angle between the guide rail housing, the positioning fixture and the connecting rod to change, and the guide steel ball moves up and down along the inclined groove of the guide rail housing, and drives the free end of the equal-strength cantilever beam to produce a displacement change, causing the equal-strength cantilever beam to bend, resulting in a change in the central wavelength of the optical fiber sensing unit attached thereto. By monitoring the strain on the surface of the equal-strength cantilever beam through the optical fiber sensing unit, the crack development condition can be quantitatively characterized.

3. The fiber Bragg grating angle three-axis seam meter according to claim 2, characterized in that: The inclined groove on the guide rail housing is smooth and linear, and the inclined groove forms an inclination angle of 30 degrees with the bottom surface of the guide rail housing, and the opening angle is 180 degrees.

4. The calculation method of the fiber Bragg grating angle three-axis seam meter according to any one of claims 1 to 3, characterized in that: The following steps are involved: S101, measuring the central wavelength of the optical fiber sensing unit; S102, calculating the strain of the equal-strength cantilever beam according to the central wavelength difference of the optical fiber sensing unit; S103, using the strain value of the equal-strength cantilever beam, calculating the changed angles of the guide rail housing and the connecting rod; S104, calculating the spatial coordinates of point M' according to the angle change, and further obtaining the displacement change from point M to point M'; Among them, point M is the initial fixing point of the positioning fixture, and point M' is the point after the positioning fixture moves due to crack development.

5. The calculation method according to claim 4, characterized in that: In S102, the strain calculation formula is as follows: Where ε is the strain of the cantilever beam with equal strength, Δλ B is the central wavelength difference of the optical fiber sensing unit, λ B is the initial center wavelength of the optical fiber sensing unit, P e is the effective elastic-optical coefficient of the optical fiber sensing unit.

6. The calculation method according to claim 5, characterized in that: In S103, the angle change between the guide rail housing and the connecting rod is calculated as follows: ΔR=kε Where ΔR is the angle change between the guide rail housing and the connecting rod; k is a coefficient obtained through calibration experiments; ε is the strain of the equal-strength cantilever beam.

7. The fiber Bragg grating angle type three-axis joint meter based on equal strength cantilever beam theory according to claim 6, characterized in that: In S104, the displacement change from point M to point M' is calculated as follows: In three-dimensional space, a point on the crack is selected as the origin, the direction along the length of the crack is the x-axis, the direction perpendicular to the length of the crack is the y-axis, and the plane perpendicular to the crack is the z-axis. The directions of the x, y and z axes conform to the left-hand coordinate system. Point A is fixed on one side of the crack as a fixed reference point to maintain the measurement benchmark; AB and BM are two connecting rods with known and constant lengths, both of which are rigid components, and their lengths and geometric shapes remain unchanged; Point M is fixed on the other side of the crack. As the crack gradually develops, Point M will move to a new position M'. It is known that the initial coordinates of point M are (x1, y1, z1) and can be calculated using the following formula: z1=MM xy =ABsin(α)-BMcos(α+β-90°) During the crack development process, the fiber optic sensing unit is used to monitor the deformation of the crack in real time. The fiber optic sensing unit captures the strain data of the equal-intensity cantilever beam by measuring the change in the central wavelength in the reflection spectrum, and calculates the strain value based on the strain theory of the fiber Bragg grating. Based on the measured strain data, combined with the angle change data between the guide rail housing and the connecting rod, the spatial coordinates are accurately calculated; the spatial coordinate calculation module processes the strain data and the angle change data to obtain the spatial coordinates (x2, y2, z2) of the point M' after the crack develops. The formula is as follows: z2=M'M' xy =AB'sin(α')-B'M'cos(α'+β'-90°) According to the difference in spatial coordinates, the relative displacements Δx, Δy and Δz between point M and point M' can be calculated; among which, the change in the opening and closing direction Δx=x2-x1, the change in the shear direction Δy=y2-y1, and the change in the settlement direction Δz=z2-z1.

8. A computing system using the fiber Bragg grating angle three-axis seam meter according to any one of claims 1 to 3, characterized in that: include: A measuring module, connected to the spatial coordinate calculation module, for inputting the measured central wavelength of the optical fiber sensing unit into the spatial coordinate calculation module; The measuring module includes a fiber optic sensing unit and a fiber optic sensing unit demodulator; The spatial coordinate calculation module is connected to the measurement module and the output module, and is used to set the coordinate system and convert the central wavelength of the optical fiber sensing unit input by the measurement module into strain and angle changes, and finally calculate the spatial position coordinates of the measurement point; The output module is connected with the spatial coordinate calculation module to calculate the changes in the opening and closing, shearing and settlement directions according to different spatial coordinates; The information data processing terminal is used to implement a computing system.

9. A computer device, characterized in that: The computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the computing method according to any one of claims 4 to 7.

10. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the computing method according to any one of claims 4 to 7.

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