Non-contact pre-tightening force measuring bolt system and pre-tightening force measuring method
By introducing low reflectivity and high reflectivity mirrors into the bolt system, forming an F-P cavity and using swept frequency collimated beams for measurement, the problem of lack of contactless bolt preload measurement methods in the prior art is solved, and efficient and accurate measurement of bolt preload is achieved.
Patent Information
- Application Number
- CN202510332230.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-20
- Publication Date
- 2025-05-30
AI Technical Summary
There is a lack of suitable non-contact method in the prior art to evaluate the actual state of the flange fastening bolt connection structure, especially when contactless measurements of the bolt connection structure are required.
Using a non-contact preload measurement bolt system, the system includes a bolt, a low reflectance mirror, a grating temperature sensor and a high reflectance mirror. By forming an F-P cavity and measuring it with a sweeping collimated beam, the preload of the bolt can be measured in a non-contact manner.
It realizes efficient and non-contact measurement of bolt preload, can accurately calculate the preload of bolts, and compensate for the influence of ambient temperature through the grating temperature sensor to improve measurement accuracy.
Smart Images
Figure CN120063566A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of pre-tightening force measurement, and particularly to a non-contact pre-tightening force measurement bolt system and a pre-tightening force measurement method. Background Art
[0002] Bolt connection is an assembly form widely used in engineering. Under the action of environmental factors such as force and vibration, bolts are likely to become loose, which will not only affect the normal use of the connection structure, but may also lead to safety accidents in severe cases. Therefore, non-destructive testing methods for bolt loosening have always attracted the attention of researchers.
[0003] In the prior art, the detection of some large flange bolt connection structures can generally be divided into local detection and overall detection. Local detection is aimed at specific structural components, such as X-ray flaw detection, magnetic particle flaw detection, ultrasonic flaw detection, penetrant flaw detection, eddy current flaw detection and other methods. These detection methods usually need to contact the measured components and are often used when the structural target is clear. However, the local detection method is complex and costly, and cannot comprehensively inspect large and complex structures or structures with unpredictable damage locations in advance; The overall detection method can be divided into static detection method and dynamic detection method. The traditional static detection method is to conduct a static load test on the structure and measure static parameters related to the structural performance, such as deformation, deflection, strain, cracks, etc. The static test is time-consuming and laborious; The dynamic detection method mainly compares the measured structure with the standard structure, and once the test structure is different from the standard structure, it will be shown in the dynamic fingerprint, mainly including frequency, vibration mode, flexibility, strain, power spectrum, frequency response coefficient, etc.
[0004] Although there are already various non-destructive testing methods in the prior art, each testing method has its applicable scope and limitations. Especially when a non-contact measurement of the bolt connection structure is required, the above measurement methods are not very applicable. Therefore, it is necessary to develop a new non-contact non-destructive testing method to evaluate the actual state of the flange fastening bolt connection structure. Summary of the Invention
[0005] The purpose of the present invention is to provide a non-contact pre-tightening force measurement bolt system and a pre-tightening force measurement method, so as to solve the technical problem that there is no applicable method for non-contact measurement of bolt connection structures in the prior art.
[0006] The present invention discloses a non-contact pre-tightening force measurement bolt system, including a bolt system and a pre-tightening force measurement system;
[0007] The bolt system includes a bolt, a low-reflectivity mirror, a grating temperature sensor and a high-reflectivity mirror. A small hole is provided inside the bolt, and the low-reflectivity mirror and the high-reflectivity mirror are respectively arranged at both ends of the small hole;
[0008] The low-reflectivity mirror and the high-reflectivity mirror form a Fabry-Perot (F-P) cavity.
[0009] Working principle: During use, a swept-frequency collimated light beam with a spectral range of 1520 nm to 1570 nm is incident on the bolt surface non-contact vertically. The light beam that matches the resonant wavelength of the F-P cavity will be transmitted and lost, and the light beam that does not match the resonant wavelength of the F-P cavity will be reflected into the pre-tightening force measurement system. By measuring the spectrum of the reflected light beam of the F-P cavity, the resonant wavelength of the F-P cavity can be obtained, and thus the cavity length of the F-P cavity and the magnitude of the bolt pre-tightening force can be calculated. By setting the low-reflectivity mirror and the high-reflectivity mirror, the reflection signals are r1 and r2 respectively. The two reflected optical signals will interfere to form an intensity modulation signal that varies with the wavelength. The signal is approximately sinusoidal, and the period corresponds to the length between the two mirrors. By demodulating this intensity modulation signal, the length of the F-P cavity can be obtained, and further the bolt pre-tightening force can be calculated. By setting a grating temperature sensor, the influence of the ambient temperature on the measurement result can be compensated. By monitoring the change in the reflection wavelength of the grating temperature sensor, the ambient temperature can be obtained, and then the measured value of the bolt pre-tightening force can be corrected.
[0010] Further, the grating temperature sensor is a reflective volume grating temperature sensor with a reflection wavelength of 1560 nm.
[0011] Further, the resonant wavelength of the F-P cavity is 1530 nm.
[0012] Further, the reflection wavelength of the low-reflectivity mirror is 1530 ± 10 nm, and the reflectivity is 10%.
[0013] Further, the reflection wavelength of the high-reflectivity mirror is 1530 ± 10 nm, and the reflectivity is greater than 99.5%.
[0014] Further, the diameter of the small hole is less than 1 mm.
[0015] By setting the diameter of the small hole, it can be ensured that the incident light enters the FP cavity vertically, thereby reducing the cavity length measurement error caused by oblique incidence. It is worth noting that if the diameter of the small hole is too small, the signal intensity will become weak, which is not conducive to signal extraction.
[0016] Further, the pre-tightening force measurement system includes a swept-frequency fiber optic light source, an optical fiber circulator, an optical fiber collimator, and a spectrometer.
[0017] By setting a swept-frequency fiber optic light source, a swept-frequency collimated light beam can be provided. Only by vertically irradiating the collimated detection light beam on the bolt opening, the magnitude of the bolt pre-tightening force can be measured, and the operation is simple and efficient.
[0018] The laser reflected from the bolt enters the spectrometer after passing through the fiber collimator and the fiber optic circulator. The signal detected by the spectrometer is an intensity modulation signal that varies with wavelength. By demodulating this intensity modulation signal, the length of the F-P cavity can be obtained, and further the magnitude of the bolt pre-tightening force can be calculated.
[0019] Furthermore, the swept-frequency fiber light source is a fully fiber-optic structure swept-frequency light source with a swept-frequency range of 1520 - 1570 nm.
[0020] Furthermore, a beam angle adjustment system is also provided within the pre-tightening force measurement system.
[0021] Furthermore, the beam angle adjustment system includes a two-dimensional electric mirror mount.
[0022] Furthermore, the beam angle adjustment system performs a periodic 5° angle scan on the collimated light beam at a scanning speed of 1 kHz.
[0023] It is used to automatically compensate for the deviation angle between the collimated light beam and the bolt surface during actual operation. When the collimated light beam is perpendicular to the bolt surface, the signal of the pre-tightening force measurement system is the strongest.
[0024] A non-contact pre-tightening force measurement method has the above-mentioned non-contact pre-tightening force measurement bolt system.
[0025] Compared with the prior art, the beneficial effects of the present invention are:
[0026] 1. By measuring the spectrum of the reflected beam of the F-P cavity, the resonant wavelength of the F-P cavity can be obtained, thereby calculating the length of the F-P cavity and the magnitude of the bolt pre-tightening force;
[0027] 2. By setting a grating temperature sensor, the influence of the ambient temperature on the measurement result can be compensated;
[0028] 3. By monitoring the change in the reflected wavelength of the grating temperature sensor, the ambient temperature can be obtained, and then the measured value of the bolt pre-tightening force can be corrected;
[0029] 4. By setting a low-reflectivity mirror and a high-reflectivity mirror, the reflected signals are r1 and r2 respectively. The two reflected optical signals will interfere to form an intensity modulation signal that varies with wavelength. The signal is approximately sinusoidal, and the period corresponds to the length between the two mirrors. By demodulating this intensity modulation signal, the length of the F-P cavity can be obtained, and further the bolt pre-tightening force can be calculated;
[0030] 5. By setting a swept-frequency fiber light source, a swept-frequency collimated light beam can be provided. Only by vertically irradiating the collimated detection light beam at the bolt opening, the magnitude of the bolt pre-tightening force can be measured, and the operation is simple and efficient. Description of the Drawings
[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following accompanying drawings only show some embodiments of the present invention, and thus should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related accompanying drawings can also be obtained based on these drawings.
[0032] Figure 1 It is a schematic structural diagram of a non-contact pre-tightening force measuring bolt system of the present invention.
[0033] Figure 2 It is the reflected laser spectral signal of the present invention.
[0034] In the above accompanying drawings, the meanings represented by each mark are as follows: 1 - bolt system, 2 - pre-tightening force measuring system, 101 - high reflectivity mirror, 102 - grating temperature sensor, 103 - bolt, 104 - low reflectivity mirror, 201 - swept fiber light source, 202 - fiber optic circulator, 203 - fiber optic collimator, 204 - spectrometer, 205 - beam angle adjustment system. Specific embodiments
[0035] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.
[0036] Embodiment 1
[0037] In this embodiment, a non-contact pre-tightening force measuring bolt system is disclosed, and the structure is as Figure 1 shown, including a bolt system 1 and a pre-tightening force measuring system 2;
[0038] The bolt system 1 includes a bolt 103, a low reflectivity mirror 104, a grating temperature sensor 102, and a high reflectivity mirror 101. A small hole is provided in the bolt 103, and the low reflectivity mirror 104 and the high reflectivity mirror 101 are respectively provided at both ends of the small hole;
[0039] The low reflectivity mirror 104 and the high reflectivity mirror 101 form an F-P cavity.
[0040] Working principle: During use, a swept-frequency collimated light beam with a spectral range of 1520 nm to 1570 nm is incident on the surface of the bolt 103 non-contact vertically. The light beam that matches the resonance wavelength of the F-P cavity will be transmitted and lost, and the light beam that does not match the resonance wavelength of the F-P cavity will be reflected into the pre-tightening force measurement system 2. By measuring the spectrum of the reflected light beam of the F-P cavity, the resonance wavelength of the F-P cavity can be obtained, and thus the cavity length of the F-P cavity and the magnitude of the pre-tightening force of the bolt 103 can be calculated. By setting the low-reflectivity mirror 104 and the high-reflectivity mirror 101, the reflection signals are r1 and r2 respectively. The two reflected optical signals will interfere to form an intensity modulation signal that varies with the wavelength. The signal is approximately sinusoidal, and the period corresponds to the length between the two mirrors. By demodulating the intensity modulation signal, the length of the F-P cavity can be obtained, and further the pre-tightening force of the bolt 103 can be calculated.
[0041] By setting the grating temperature sensor 102, the influence of the ambient temperature on the measurement result can be compensated. By monitoring the change in the reflection wavelength of the grating temperature sensor 102, the ambient temperature can be obtained, and then the measured value of the pre-tightening force of the bolt 103 can be corrected.
[0042] Embodiment 2
[0043] As a preferred embodiment of the present invention, on the basis of Embodiment 1, a non-contact pre-tightening force measurement bolt system is disclosed. The resonance wavelength of the F-P cavity is 1530 nm, and the grating temperature sensor 102 is a reflective volume grating temperature sensor with a reflection wavelength of 1560 nm.
[0044] Embodiment 3
[0045] As a preferred embodiment of the present invention, on the basis of Embodiment 2, a non-contact pre-tightening force measurement bolt system is disclosed. The reflection wavelength of the low-reflectivity mirror 104 is 1530 ± 10 nm, the reflectivity is 10%, the reflection wavelength of the high-reflectivity mirror 101 is 1530 ± 10 nm, the reflectivity is greater than 99.5%, and the diameter of the small hole is less than 1 mm.
[0046] Embodiment 4
[0047] As a preferred embodiment of the present invention, on the basis of Embodiment 3, a non-contact pre-tightening force measurement bolt system is disclosed. The pre-tightening force measurement system 2 includes a swept-frequency fiber optic light source 201, an optical fiber circulator 202, an optical fiber collimator 203, and a spectrometer 204.
[0048] The swept-frequency fiber optic light source 201 is a fully fiber-optic structure swept-frequency light source with a swept-frequency range of 1520 to 1570 nm.
[0049] By setting the swept-frequency optical fiber light source 201, a collimated swept-frequency light beam can be provided. It only needs to vertically irradiate the opening of the bolt 103 with the collimated detection light beam to measure the pre-tightening force of the bolt 103, and the operation is simple and efficient.
[0050] The laser reflected from the bolt 103 enters the spectrometer 204 after passing through the fiber collimator 203 and the fiber optic circulator 202. The signal detected by the spectrometer 204 is an intensity modulation signal that varies with wavelength. By demodulating this intensity modulation signal, the length of the F-P cavity can be obtained, and further the pre-tightening force of the bolt 103 can be calculated.
[0051] Embodiment 5
[0052] As a preferred embodiment of the present invention, on the basis of Embodiment 4, a non-contact pre-tightening force measuring bolt system is disclosed. A beam angle adjustment system 205 is further provided in the pre-tightening force measuring system 2. The beam angle adjustment system 205 includes a two-dimensional electric mirror mount, and the beam angle adjustment system 205 performs a periodic scan of 5° on the collimated light beam at a scanning speed of 1 kHz.
[0053] It is used to automatically compensate for the deviation angle between the collimated light beam and the surface of the bolt 103 during the actual operation. When the collimated light beam is perpendicular to the surface of the bolt 103, the signal of the pre-tightening force measuring system 2 is the strongest.
[0054] The specific calculation method is as follows.
[0055] Since the cavity length L of the FP cavity is an integer multiple of the resonant wavelength, assuming that the wavelengths corresponding to the m-th and (m + n)-th order maxima are λm and λm + n, according to the Airy formula, the cavity length can be expressed as:
[0056]
[0057] From the above two equations, the cavity length L of the F-P cavity can be obtained:
[0058]
[0059] In the formula, L is the cavity length, n is an integer. By substituting the wavelengths corresponding to the selected two maxima, the length of the F-P cavity can be calculated. The relationship between the pre-tightening force of the bolt and the cavity length L is mapped in advance, and the pre-tightening force of the bolt can be detected online through a look-up table. Figure 2 There is a peak spectrum λg in the reflected laser spectrum signal shown. It is the reflection spectrum of the grating temperature sensor 102. By measuring λg, the ambient temperature can be measured, thereby correcting the measurement result of the bolt pre-tightening force and improving the measurement accuracy of the bolt pre-tightening force.
[0060] The above are the implementation manners enumerated in this embodiment. However, this embodiment is not limited to the above optional implementation manners. Those skilled in the art can obtain many other implementation manners by arbitrarily combining the above manners. Anyone can obtain various other forms of implementation manners under the inspiration of this embodiment. The above specific implementation manners should not be construed as limiting the protection scope of this embodiment. The protection scope of this embodiment should be defined by the claims, and the specification can be used to interpret the claims.
Claims
1. A non-contact preload force measurement bolt system, characterized in that: It comprises a bolt system (1) and a preload force measuring system (2); The bolt system (1) comprises a bolt (103), a low-reflectivity reflector (104), a grating temperature sensor (102) and a high-reflectivity reflector (101); a small hole is arranged in the bolt (103); and the low-reflectivity reflector (104) and the high-reflectivity reflector (101) are respectively arranged at two ends of the small hole; The low reflectivity reflector (104) and the high reflectivity reflector (101) form an FP cavity.
2. A non-contact preload force measurement bolt system according to claim 1, characterized in that: The FP cavity resonant wavelength is 1530 nm.
3. The non-contact preload force measurement bolt system according to claim 1, characterized in that: The grating temperature sensor (102) is a reflective volume grating temperature sensor with a reflection wavelength of 1560 nm.
4. The non-contact preload force measurement bolt system according to claim 1, characterized in that: The low reflectivity reflector (104) has a reflection wavelength of 1530±10 nm and a reflectivity of 10%.
5. The non-contact preload force measurement bolt system according to claim 1, characterized in that: The high reflectivity reflector (101) has a reflection wavelength of 1530±10 nm and a reflectivity greater than 99.5%.
6. The non-contact preload force measurement bolt system according to claim 3, characterized in that: The diameter of the small hole is less than 1 mm.
7. A non-contact preload force measurement bolt system according to any one of claims 1 to 6, characterized in that: The preload force measurement system (2) comprises a swept-frequency optical fiber light source (201), an optical fiber circulator (202), an optical fiber collimator (203) and a spectrometer (204).
8. The non-contact preload force measurement bolt system according to claim 7, characterized in that: The preload force measurement system (2) is also provided with a light beam angle adjustment system (205).
9. The non-contact preload force measurement bolt system according to claim 8, characterized in that: The beam angle adjustment system (205) comprises a two-dimensional electric mirror frame.
10. A non-contact preload force measurement method, characterized in that: A non-contact preload force measurement bolt system is used as described in any one of claims 1 to 9.