General measuring device for thread structure loosening based on distributed optical fiber sensing

Abstract

This invention provides a universal measuring device for loose threaded structures based on distributed optical fiber sensing. A distributed sensing optical fiber is mounted on a spring plate. A bolt passes sequentially through the object to be fixed and a claw washer located on the upper surface of the object, then is threadedly connected to a first nut within the claw washer. Rotating the first nut causes the bolt's nut to abut against the lower surface of the object, fixing the spring plate's moving cavity to the object. When the first nut rotates, the claw washer causes the spring plate to extend and retract along the spring plate's moving cavity, resulting in a first change in the distributed sensing optical fiber. Based on the optical signal returned after receiving the measurement optical signal from the distributed sensing optical fiber, the change in the distributed sensing optical fiber is determined, and the looseness of the threaded structure is determined based on this change. This invention can measure the looseness of threaded structures at any set angle, exhibiting high versatility and high measurement sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of bolt loosening detection, specifically relating to a universal measuring device for loose threaded structures based on distributed optical fiber sensing. Background Technology

[0002] Bolt loosening at multiple nodes, such as those on transmission towers, is a major factor leading to tower deformation or other damage. Therefore, timely identification of the degree of bolt loosening damage at node plates is of great significance. In current bolt loosening measurement methods, most systems employ strain gauges, with one strain gauge corresponding to one measurement point. To measure bolt loosening, multiple strain gauges are typically used. However, this method has drawbacks when inspecting large and numerous structures. It requires a large number of strain gauges and associated electrical equipment, and is susceptible to electromagnetic interference, increasing the system's hardware complexity and raising operating and maintenance costs. To address these issues, researchers have proposed using distributed fiber optic sensing technology to monitor the loosening of threaded structures, as exemplified by patent application number 2022106238554, entitled "Threaded Structure Loosening Measurement Device Based on Distributed Fiber Optic Sensing." However, this patent requires the use of the gravity of some components to achieve thread loosening detection. Therefore, the setting direction must be vertical and the components must be facing upwards. It can be seen that when using distributed fiber optic sensing to measure thread loosening, the thread structure cannot be set at any angle, resulting in a lack of universality in setting angles. Summary of the Invention

[0003] This invention provides a universal measuring device for loose threaded structures based on distributed optical fiber sensing, in order to solve the problem that the setting angle of the threaded structure in current distributed optical fiber threaded structure loosening measuring devices is not universal.

[0004] According to a first aspect of the present invention, a universal measuring device for loosening of threaded structures based on distributed optical fiber sensing is provided, comprising a threaded structure, a claw washer, a spring plate moving cavity, and a spring plate placed in the spring plate moving cavity. The spring plate is provided with distributed sensing optical fibers. The threaded structure includes a bolt and a first nut. The second end of the bolt passes sequentially through the object to be fixed and the claw washer located above the upper surface of the object to be fixed, and is threadedly connected to the first nut in the claw washer. By rotating the first nut, the nut of the bolt abuts against the bottom surface of the object to be fixed, thereby achieving the fastening of the object to be fixed.

[0005] The first end of the spring plate is connected to the spring plate movement cavity, and the second end is connected to the claw washer. The spring plate movement cavity is fixed on the object to be fixed. When the first nut rotates, the claw washer drives the spring plate to extend and retract along the cavity of the spring plate movement cavity, thereby causing a first change in the distributed sensing optical fiber. Based on the optical signal returned after the distributed sensing optical fiber receives the measurement optical signal, the change of the distributed sensing optical fiber is determined, and based on the change of the distributed sensing optical fiber, the loosening of the threaded structure is determined.

[0006] In one alternative implementation, the rotation of the first nut includes the following types of rotation:

[0007] Of the bolt and the first nut, only the first nut rotates in the positive upward direction when subjected to external force;

[0008] Only when the bolt is subjected to external force and rotates downward, it causes the first nut to rotate in the opposite direction. During the reverse rotation of the first nut, the first claw washer abuts against the upper surface of the object to be fixed.

[0009] When the bolt is rotated downward by an external force, and the first nut is affected by an external force that prevents it from rotating in the opposite direction, the first nut may rotate in the forward or reverse direction.

[0010] In another optional implementation, determining the loosening status of the threaded structure based on the changes in the distributed sensing fiber specifically includes: determining whether the changes in the distributed sensing fiber include a first change caused by the rotation of the first nut; if so, determining that the threaded structure has become loose; otherwise, determining that the threaded structure has not become loose.

[0011] In another alternative implementation, when installing the thread structure loosening measuring device, the object to be fixed is first tightened, then the spring plate moving cavity is fixed on the object to be fixed, and then the second end of the spring plate in the spring plate moving cavity is connected to the claw pad.

[0012] The first nut is separately and tightly fitted to the claw washer, with the first nut extending out from the claw washer toward the first end of the bolt.

[0013] In another alternative implementation, the spring sheet is wavy relative to the upper surface of the object to be fixed, and the distributed sensing optical fiber is laid on the spring sheet along the direction of the wave.

[0014] In another alternative implementation, the spring plate moving cavity includes an upper cover and a bottom plate. The upper cover includes a cover plate and a first arcuate partition and a second arcuate partition extending on the cover plate toward the bottom plate. The first arcuate partition and the second arcuate partition are concentric, have equal curvature, and are aligned at both ends. The first end of the spring plate is engaged in a first snap-fit ​​between the first arcuate partition and the second arcuate partition to fix the first end of the spring plate.

[0015] The base plate includes a base plate body, on which an annular groove is formed. The annular groove matches the space between the first arc partition and the second arc partition. After the top cover is installed on the base plate, the space enclosed by the annular groove, the first arc partition, and the second arc partition constitutes the cavity of the spring plate movement chamber.

[0016] In another optional implementation, the base plate body extends upward to form an arc-shaped connecting plate, and the arc-shaped connecting plate extends inward to form an arc-shaped baffle parallel to the base plate body; the base plate body also has an arc-shaped through hole, the arc-shaped through hole is located below the arc-shaped baffle and its two ends extend to the outside directly below the arc-shaped baffle, and the arc-shaped connecting plate, the arc-shaped baffle, the arc-shaped through hole and the second arc-shaped partition are on the same central axis;

[0017] The second arc partition is located outside the first arc partition, and a third arc partition extends outward from one end of the second arc partition facing the bottom plate; protrusions extend downward from both ends of the outer edge of the third arc partition; the third arc partition is inserted between the arc baffle and the bottom plate body, and the protrusions are inserted into the arc-shaped through hole, thereby realizing the snap-fit ​​of the top cover and the bottom plate;

[0018] The arc baffle, cover plate and base plate are all provided with matching first through holes. Fasteners pass through the first through holes of the three in sequence to fix the spring plate moving cavity formed by the upper cover and the base plate to the object to be fixed.

[0019] In another optional implementation, both the cover plate and the base plate body are provided with a central through hole to accommodate the claw pad. The central through hole on the cover plate is located inside the first arc partition, and the central through hole on the base plate body is located inside the annular groove.

[0020] A circular retaining ring extends upward from the outer edge of the annular groove. After the upper cover is snapped onto the base plate, the first arc-shaped partition is located inside the annular groove, and the second arc-shaped partition is located outside the circular retaining ring.

[0021] In another alternative implementation, the claw pad includes a pad, a fixing block, and a connecting part. The pad has a second through hole with a radius greater than or equal to the radius of the bolt. The pad extends upward to form multiple fixing blocks, each of which is circumferentially and evenly arranged outside the second through hole, and one of the fixing blocks extends outward to form a connecting part for mating with the second end of the spring sheet.

[0022] In another alternative implementation, one end of the distributed sensing fiber of the current threaded structure can be connected to the next threaded structure after passing through the spring sheet, and laid on the spring sheet of the next threaded structure. In this way, the loosening measurement of multiple threaded structures can be realized using a single distributed sensing fiber.

[0023] It also includes a light source, a pulse modulator, a frequency shifter, a circulator, a coupler, a photodetector, a data acquisition unit, a data processor, and a test fiber formed by multiple distributed sensing fibers connected in series in a threaded structure. The output end of the light source is connected to the pulse modulator and the frequency shifter respectively. The output end of the pulse modulator is connected to the first end of the circulator. The second end of the circulator is connected to one end of the test fiber in sequence, and the third end is connected to the first input end of the coupler. The output end of the frequency shifter is connected to the second input end of the coupler. The output end of the coupler is connected to the data processor in sequence through the photodetector and the data acquisition unit.

[0024] The light source splits continuous light into two paths: a probe beam and a reference beam. The probe beam is periodically injected into the fiber under test (BUT) through a circulator at a certain period. Upon receiving the probe beam, the BUT generates back-propagating Brillouin scattered light, resulting in a Brillouin frequency shift. The back-propagating Brillouin scattered light is transmitted to the coupler through the circulator. The reference beam is injected into the frequency shifter, shifted, and then transmitted to the circulator. The Brillouin scattered light and the frequency-shifted reference beam interfere at the coupler, forming an interference light signal. The photodetector converts the interference light signal into an interference electrical signal. The data acquisition unit acquires the interference electrical signal and sends it to the data processor. The data processor demodulates the changes in the BUT based on the interference electrical signal and determines the looseness of each thread structure based on the changes in each distributed sensing fiber within the BUT.

[0025] The beneficial effects of this invention are:

[0026] 1. The threaded structure of this invention includes a bolt and a first nut. The nut of the bolt abuts against the object to be fixed, and the second end of the bolt passes through the object to be fixed and is threadedly connected to the first nut. The object to be fixed can be tightened by rotating the first nut. Furthermore, the loosening measurement of this invention mainly relies on the first change of the distributed sensing optical fiber caused by the rotation of the first nut. The rotation of the first nut is independent of the setting angle of the threaded structure. Therefore, the loosening measurement of this invention is independent of the setting angle of the threaded structure. That is, this invention can realize the loosening measurement of the threaded structure at any setting angle, and its versatility is high. This invention sets a spring plate and sets the distributed sensing optical fiber on the spring plate. When the threaded structure is loosened, it drives the spring plate to extend and retract along the cavity of the spring plate. Thus, even if the movement amplitude caused by the loosening of the threaded structure is small, the extension and retraction of the spring plate will be large, and the corresponding change of the distributed sensing optical fiber on the spring plate will also be large. Therefore, the loosening measurement of the threaded structure of this invention has high sensitivity.

[0027] 2. This invention designs the tightness of the threaded connection between the bolt and the first nut so that when the bolt is rotated downwards by an external force, it causes the first nut to rotate in the opposite direction. This allows for further subdivision of the loosening situation when the bolt rotates downwards by force. After subdivision, only when the external force applied to the first nut reaches a specific value can the loosening be determined by the first change of the distributed sensing fiber. The dynamically changing external force environment makes this value negligible. Therefore, it can be considered that any possible loosening situation can be determined by the first change of the distributed sensing fiber. It is evident that this invention can comprehensively monitor all kinds of loosening situations that may occur in the threaded structure, and the monitoring sensitivity of each loosening situation is high. In addition, the threaded structure of this invention only includes two components, the bolt and the first nut, which can form fewer categories of loosening situations. Under the categories of loosening situations formed by combination, by causing the first nut to rotate in the opposite direction when the bolt is rotated downwards by an external force, the first change can be used to monitor all categories of loosening situations.

[0028] 3. By designing the installation sequence of each component of the device, this invention can meet the installation requirements of objects of any thickness, thereby further improving the versatility of the device. By separating the first nut and the claw washer, this invention improves the installation flexibility of the device. Even if the spring plate's moving cavity is fixed before the object to be fixed is tightened, the loosening measurement device for objects of any thickness can still be installed, making it highly applicable. Furthermore, by ensuring a tight fit between the first nut and the claw washer, this invention ensures that the first nut rotates smoothly and synchronously with the claw washer. The first nut extends from the claw washer towards the second end of the bolt, facilitating direct rotation and tightening of the first nut during maintenance.

[0029] 4. By making the spring sheet wavy and arranging the distributed sensing optical fiber along the wave direction on the spring sheet, the present invention can amplify the changes caused by the rotation of the first nut and the tilting of the bolt, thereby improving the sensitivity of thread structure loosening measurement.

[0030] 5. This invention divides the spring plate movement cavity into two parts: an upper cover and a bottom plate. After the upper cover is installed on the bottom plate, a cavity for placing the spring plate is formed. When the spring plate and / or the sensing optical fiber distributed on the spring plate is damaged, the upper cover can be removed to take out the spring plate for replacement. When the spring plate is replaced, it is not necessary to replace the spring plate movement cavity, thus reducing maintenance costs. In addition, the upper cover of this invention extends a first arc partition and a second arc partition on the side facing the bottom plate. Both partitions are arc-shaped. Thus, the cavity formed by the two arc partitions on the upper cover and the annular groove on the bottom plate will be an arc shape. This invention sets the cavity for placing the spring plate to be arc-shaped, which makes it convenient for installers to accurately adjust the position of the connecting part on the claw pad for docking the second end of the spring plate.

[0031] 6. By designing the connection mechanism between the upper cover and the base plate, the present invention can easily and quickly snap the upper cover onto the base plate, so that the corresponding through holes on the upper cover and the base plate can be quickly aligned, so that the spring plate moving cavity formed by the upper cover and the base plate can be quickly fixed onto the object to be fixed using fasteners, thereby improving the installation efficiency of the spring plate moving cavity.

[0032] 7. By opening a central through hole on both the upper cover and the bottom plate to accommodate the claw pad, the rotation of the claw pad is not affected by the spring plate movement cavity. The invention extends a circular retaining ring upward from the outer edge of the annular groove, and positions the second arc partition outside the circular retaining ring rather than inside the annular groove. Thus, when the upper cover is snapped onto the bottom plate, it is not necessary to specifically align the two arc partitions in the upper cover with the annular groove, thereby further improving the snapping efficiency between the upper cover and the bottom plate, and thus further improving the installation efficiency of the spring plate movement cavity.

[0033] 8. This invention connects multiple distributed sensing optical fibers corresponding to multiple threaded structures in series, so that the loosening measurement of multiple threaded structures can be realized using a single optical fiber. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the universal measuring device for loose threaded structures based on distributed optical fiber sensing of the present invention;

[0035] Figure 2 This is a side view of the overall structure of an embodiment of the universal measuring device for loose threaded structures based on distributed optical fiber sensing of the present invention;

[0036] Figure 3 yes Figure 2AA section view;

[0037] Figure 4 This is a schematic diagram of the structure of the spring sheet of the present invention;

[0038] Figure 5 This is a schematic diagram of the structure of the top cover of the present invention;

[0039] Figure 6 This is a schematic diagram of the structure of the base plate of the present invention;

[0040] Figure 7 This is a schematic diagram of a portion of the structure in the base plate of the present invention from a first-view perspective;

[0041] Figure 8 This is a structural schematic diagram of a portion of the base plate of the present invention from a second perspective;

[0042] Figure 9 This is a schematic diagram of the structure of the present invention after the top cover and bottom plate are installed;

[0043] Figure 10 This is a schematic diagram of the claw pad structure of the present invention;

[0044] Figure 11 This is a diagram showing the positional relationship between the top cover and the claw pad of the present invention;

[0045] Figure 12 This is a top view of the claw pad and base plate of the present invention;

[0046] Figure 13 This is a schematic diagram of the measurement structure of an embodiment of the universal measuring device for loose threaded structures based on distributed optical fiber sensing of the present invention. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the embodiments of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0048] In the description of this invention, unless otherwise specified and limited, it should be noted that the term "connection" should be interpreted broadly. For example, it can be a mechanical connection or an electrical connection, or it can be a connection between two internal components. It can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above term according to the specific circumstances.

[0049] See Figure 1 This is a schematic diagram of the overall structure of an embodiment of the universal measuring device for loose threaded structures based on distributed optical fiber sensing according to the present invention. Combined with... Figure 2 and Figure 3As shown, the universal measuring device for loose threaded structures based on distributed optical fiber sensing may include a threaded structure, a claw washer 2, a spring plate moving cavity 3, and a spring plate 4 placed in the spring plate moving cavity 3. The threaded structure may include a bolt 1 and a first nut 13. The spring plate 4 is provided with distributed sensing optical fiber. The second end of the bolt 1 passes through the object to be fixed 5 and the claw washer 2 located on the upper surface of the object to be fixed in sequence, and is threadedly connected to the first nut 13 in the claw washer 2. By rotating the first nut 13, the nut 12 of the bolt 1 abuts against the bottom surface of the object to be fixed 5, thereby achieving the fastening of the object to be fixed 5. The first end of the spring plate 4 is connected to the spring plate movement cavity 3, and the second end is connected to the claw pad 2. The spring plate movement cavity 3 is fixed to the object to be fixed 5. When the first nut 13 rotates, the claw pad 2 drives the spring plate 4 to extend and retract along the cavity of the spring plate movement cavity 3, thereby causing a first change in the distributed sensing optical fiber. Based on the optical signal returned after the distributed sensing optical fiber receives the measurement optical signal, the change of the distributed sensing optical fiber is determined, and based on the change of the distributed sensing optical fiber, the loosening of the threaded structure 1 is determined. The change can be strain or deformation; the claw pad 2 can be located inside the spring plate movement cavity 3.

[0050] The threaded structure of this invention includes a bolt and a first nut. The bolt's nut abuts against the object to be fixed, and the second end of the bolt passes through the object and is threadedly connected to the first nut. Tightening the object can be achieved by rotating the first nut. Furthermore, the loosening measurement of this invention primarily relies on the initial change in the distributed sensing fiber caused by the rotation of the first nut. Since the rotation of the first nut is independent of the setting angle of the threaded structure, the loosening measurement of this invention is independent of the setting angle of the threaded structure (i.e., the angle of the bolt relative to the horizontal plane). This means that this invention can achieve loosening measurement of threaded structures at any setting angle, exhibiting high versatility. However, when using distributed sensing fiber to detect the loosening of a threaded structure, directly connecting the distributed sensing fiber to the threaded structure makes it difficult to detect small movements caused by loosening, resulting in low sensitivity for loosening detection in this invention. This invention incorporates a spring plate with distributed sensing optical fibers mounted on it. When the threaded structure loosens, the spring plate extends and retracts along the cavity of the spring plate's movement chamber. Thus, even if the movement caused by the loosening of the threaded structure is small, the extension and retraction of the spring plate will be large, and correspondingly, the change in the distributed sensing optical fibers on the spring plate will also be large. Therefore, this invention has high sensitivity in measuring the loosening of the threaded structure.

[0051] In this embodiment, the bolt 1 may include a screw 11 and a nut 12 that are fixedly connected. Since the nut is fixed to the bolt 1, when the nut abuts against the object to be fixed 5, the distance between the first nut 13 and the nut after tightening determines the thickness of the object to be fixed. As the first nut 13 rotates, it drives the claw washer 2 to rotate. Therefore, the position of the first nut 13 on the screw 11 will correspond to the direction of the connecting part on the claw washer 2 used to connect the second end of the spring plate 4. In other words, the direction of the connecting part on the claw washer 2 is related to the thickness of the object to be fixed. If, when installing the device of this invention, the spring plate moving cavity 3 is first fixed to the object to be fixed 5, thus fixing the first end of the spring plate 4, then when the thickness of the object to be fixed 5 causes the connecting part on the claw washer 2 to point towards the first end of the spring plate 4, even if the spring plate 4 is compressed to its limit, it will be impossible to align the second end of the spring plate 4 with the connecting part on the claw washer 2. Therefore, fixing the spring plate moving cavity 3 before rotating the first nut 13 to its position and tightening the object to be fixed may not be able to accommodate objects of arbitrary thickness, resulting in low versatility. Therefore, when installing the universal measuring device for loose threaded structures according to the present invention, the object to be fixed can be tightened first, then the spring plate moving cavity can be fixed to the object to be fixed, and then the second end of the spring plate in the spring plate moving cavity can be connected to the claw pad. By designing the installation sequence of the various components of the device, the present invention can meet the installation requirements of objects of any thickness, thereby further improving the versatility of the device.

[0052] In this embodiment, the first nut 13 can be separately and tightly fitted from the claw washer 2. During installation, if the installation sequence is incorrect, such as first fixing the spring plate's moving cavity to the object to be fixed and then tightening the object, it may be impossible to align the second end of the spring plate 4 with the connecting portion on the claw washer 2. In this case, if the first nut 13 and the claw washer 2 are integrally formed, the spring plate's moving cavity must be disassembled and reinstalled, resulting in poor installation flexibility. In this invention, the first nut 13 and the claw washer 2 are set separately. If the spring plate moving cavity 3 is fixed before the object to be fixed 5 is tightened, the orientation of the connecting part on the claw washer 2 connected to the second end of the spring plate 4 can be adjusted according to the connection position between the first end of the spring plate 4 and the spring plate moving cavity 3. When the first nut 13 rotates to the upper entrance of the claw washer 2, the claw washer 2 is moved toward the first nut 13 so that the first nut 13 is placed inside the claw washer 2. After that, the first nut 13 drives the claw washer 2 to rotate, so as to ensure that the orientation of the connecting part on the claw washer 2 is appropriate after the object to be fixed is tightened. Since the orientation of the connection between the claw washer 2 and the spring plate 4 is adjustable before the claw washer 2 rotates with the first nut 13, this invention improves the installation flexibility of the device by separately setting the first nut and the claw washer. Even if the spring plate's moving cavity is fixed before the object to be fixed is tightened, the loosening measurement device for objects of any thickness can still be installed, making it highly versatile. Furthermore, by ensuring a tight fit between the first nut and the claw washer, this invention ensures that the claw washer rotates smoothly and synchronously when the first nut rotates. Additionally, as... Figure 1 As shown, the first nut 13 can also extend out from the claw washer 2 toward the second end of the bolt 1, so that the first nut can be directly rotated and tightened when it is installed or repaired.

[0053] Since the position of the object to be fixed 5 is fixed, after the object to be fixed 5 is tightened, the first nut 13 cannot continue to rotate downward under the action of external force, and the bolt 1 cannot continue to rotate upward under the limiting action of the nut 12. Therefore, the loosening of this threaded structure may be due to the following situations:

[0054] The first scenario involves only the first nut 13 being subjected to an external force, causing it to rotate upwards in the positive direction. In this case, the bolt 1 is not subjected to external force, and the first nut 13 drives the claw washer 2 to rotate synchronously. The rotation of the claw washer 2 then causes the spring plate 4 to extend or compress along the spring plate's movement cavity 3, resulting in a first positive change in the distributed sensing fiber. Since the spring plate 4 has a certain extension / retraction limit, when the first nut 13 rotates to a certain angle, the spring plate 4 cannot continue to extend or retract, and under the limiting action of the spring plate, the first nut 13 will stop rotating. Furthermore, as the first nut 13 rotates upwards, the distance between the nut 12 and the first nut 13 increases, causing the bolt 1 to tilt relative to the object to be fixed. At this time, the distributed sensing fiber undergoes a second change due to the tilt of the bolt 1. Therefore, in this situation, the distributed sensing fiber undergoes both a first positive change caused by the rotation of the first nut 13 and a second change caused by the tilt of the bolt 1, the changes of which are determined by the rotation angle of the first nut 13 and the tilt angle of the bolt 1.

[0055] The second scenario involves only bolt 1 being subjected to external force and rotating downwards, while the first nut 13 is not subjected to external force. Bolt 1 then drives the first nut 13 to rotate in the opposite direction. The first nut 13, through the claw washer 2, causes the spring plate 4 to compress or extend along the spring plate's movement cavity 3, resulting in a first change in the opposite direction for the distributed sensing fiber. Furthermore, as bolt 1 moves downwards, the distance between the nut 12 and the first nut 13 increases, causing bolt 1 to tilt relative to the object to be fixed. At this point, the distributed sensing fiber undergoes a second change due to the tilt of bolt 1. Therefore, in this situation, the distributed sensing fiber will experience a first change in the opposite direction caused by the rotation of the first nut 13 and a second change caused by the tilt of bolt 1. The specific changes are determined by the rotation angle of the first nut 13 and the tilt angle of bolt 1. It should be noted that when the bolt 1 rotates downwards, causing the first nut 13 and the claw washer 2 to rotate, the first nut 13 and the claw washer 2 will not move downwards due to the position restriction of the object to be fixed 5. Instead, they will only rotate on the contact plane with the object to be fixed 5. That is, when the first nut rotates in the opposite direction, the claw washer 2 will contact the upper surface of the object to be fixed 4.

[0056] The third scenario is that the bolt 1 is rotated downwards by an external force, and the first nut 13 is affected by an external force that prevents it from rotating in the opposite direction. When bolt 1 rotates downwards, causing the first nut 13 and claw washer 2 to rotate, the first nut 13 and claw washer 2 only rotate on the contact plane with the object to be fixed 5. Therefore, under the influence of external force, the first nut 13 may remain in its initial position and will not rotate in either direction. However, since the distance between the nut 12 and the first nut 13 will still increase, the distributed sensing fiber will still undergo a second change caused by the tilt of bolt 1. The change is determined by the tilt angle of bolt 1. Secondly, under the influence of external force, the first nut 13 may also rotate in the opposite direction or in the forward direction. Since the distance between the nut 12 and the first nut 13 will increase regardless of whether the rotation is in the opposite or forward direction, the distributed sensor may undergo a first change in the opposite direction caused by the rotation of the first nut 13 and a second change caused by the tilt of bolt 1, or a first change in the forward direction caused by the rotation of the first nut 13 and a second change caused by the tilt of bolt 1. The change is determined by the rotation angle of the first nut 13 and the tilt angle of bolt 1.

[0057] As can be seen from the above description, the rotation of the first nut can include the following types of rotation: only the first nut rotates upward in the positive direction when the bolt is subjected to an external force; when only the bolt rotates downward in the positive direction when the bolt is subjected to an external force, the first nut rotates in the opposite direction, and during the reverse rotation of the first nut, the first claw washer abuts against the upper surface of the object to be fixed; when the bolt rotates downward in the positive direction and the first nut is affected by an external force that prevents its reverse rotation, the first nut rotates in either the positive or negative direction.

[0058] Furthermore, in the above description, if the first nut 13 remains stationary when the bolt 1 rotates downwards under external force, then loosening can only be determined by relying on a significant first change when the first nut 13 rotates upwards under external force. For all other cases where the first nut 13 does not rotate upwards (e.g., the bolt rotating downwards under external force, or the bolt and first nut being subjected to force simultaneously but the first nut not rotating), loosening can only be determined by relying on a second change, but this second change is usually small and difficult to detect. This patent classifies the downward rotation of the bolt into two cases: the second and the third. In the second case, loosening can be determined entirely by relying on the first change in the opposite direction caused by the rotation of the first nut. In the third case, loosening is only determined by relying on the second change when the external force on the first nut is equal to the force exerted by the bolt causing the first nut to rotate in the opposite direction, keeping the first nut in its initial position and preventing rotation. In the other two cases (i.e., the external force on the first nut is greater than or less than the force exerted by the bolt causing the first nut to rotate in the opposite direction, corresponding to square rotation or reverse rotation of the first nut), loosening can be determined by relying on the first change. Since the external force on the first nut is usually wind force, it is dynamic and changes. When the bolt rotates downwards, the first nut can remain in its initial position under the influence of external force, which is an extremely special and unsustainable situation and can therefore be ignored. Therefore, this invention, by designing the tightness of the threaded connection between the bolt and the first nut, causes the first nut to rotate in the opposite direction when the bolt rotates downwards under external force. This allows for further subdivision of the loosening situation when the bolt rotates downwards under force. After subdivision, only when the external force applied to the first nut reaches a specific value will loosening be impossible to determine based on the first change in the distributed sensing fiber. The dynamically changing external force environment makes this value negligible. Therefore, any possible loosening situation can be determined based on the first change in the distributed sensing fiber. Thus, this invention can comprehensively monitor various loosening situations that may occur in the threaded structure, and the monitoring sensitivity for each type of loosening situation is high.

[0059] It should be noted that while a screw and two nuts can be used to tighten a fixed object, this threaded structure has three components. Different combinations of these three components in different states can lead to more types of loosening. Furthermore, even if the bolt is rotated downwards by an external force, causing the first nut to rotate in the opposite direction, it is impossible to monitor all loosening situations using the first change. The threaded structure of this invention only includes a screw and a first nut, resulting in fewer types of loosening situations. Within each type of loosening situation, by rotating the bolt downwards by an external force, causing the first nut to rotate in the opposite direction, the first change can be used to monitor all types of loosening. Specifically, to ensure that the first nut can rotate in both directions, the spring sheet can be in a non-limited extension / retraction state initially, preferably in a slightly stretched state.

[0060] In this invention, determining the loosening status of the threaded structure based on the changes in the distributed sensing optical fiber specifically includes: determining whether the changes in the distributed sensing optical fiber include a first change caused by the rotation of the first nut; if so, determining that the threaded structure has become loose; otherwise, determining that the threaded structure has not become loose.

[0061] As can be seen from the above embodiments, the threaded structure of the present invention includes a bolt and a first nut. The nut of the bolt abuts against the object to be fixed, and the second end of the bolt passes through the object to be fixed and is threadedly connected to the first nut. The object to be fixed can be tightened by rotating the first nut. Furthermore, the loosening measurement of the present invention mainly relies on the first change of the distributed sensing optical fiber caused by the rotation of the first nut. The rotation of the first nut is independent of the setting angle of the threaded structure. Therefore, the loosening measurement of the present invention is independent of the setting angle of the threaded structure. That is, the present invention can realize the loosening measurement of the threaded structure at any setting angle, and its versatility is high. The present invention sets a spring plate and sets the distributed sensing optical fiber on the spring plate. When the threaded structure is loosened, it drives the spring plate to extend and retract along the cavity of the spring plate. Thus, even if the movement amplitude caused by the loosening of the threaded structure is small, the extension and retraction of the spring plate will be large, and the corresponding change of the distributed sensing optical fiber on the spring plate will also be large. Therefore, the threaded structure loosening measurement of the present invention has high sensitivity.

[0062] In addition, such as Figure 4 As shown, the spring plate 4 has a wavy shape relative to the upper surface of the object to be fixed 5, and the distributed sensing optical fiber is arranged on the spring plate 4 along the wavy direction. By making the spring plate wavy and arranging the distributed sensing optical fiber along the wavy direction on the spring plate, this invention can amplify the changes caused by the rotation of the first nut, thereby improving the sensitivity of thread loosening measurement. Combined with... Figure 4 , 5As shown in Figure 6, the spring plate movement cavity 3 may include an upper cover 6 and a bottom plate 7. The upper cover 6 may include a cover plate 61 and a first arcuate partition 62 and a second arcuate partition 63 extending from the cover plate 61 toward the bottom plate 7. The first arcuate partition 62 and the second arcuate partition 63 are concentric, have equal curvature, and are aligned at both ends. The first end 41 of the spring plate 4 (e.g., Figure 4 The spring sheet 4 is fixed in the first buckle 64 between the first arc partition 62 and the second arc partition 63. The base plate 7 may include a base plate body 71, on which an annular groove 72 is provided. The annular groove 72 matches the space between the first arc partition 62 and the second arc partition 63. After the upper cover 6 is installed on the base plate 7, the space enclosed by the annular groove 72, the first arc partition 62 and the second arc partition 63 constitutes the cavity of the spring sheet movement cavity 3.

[0063] This invention divides the spring plate movement cavity into two parts: an upper cover and a bottom plate. After the upper cover is installed on the bottom plate, a cavity for placing the spring plate is formed. When the spring plate and / or the sensing optical fiber distributed on the spring plate is damaged, the upper cover can be removed to take out the spring plate for replacement. When replacing the spring plate, it is not necessary to replace the spring plate movement cavity as well, thus reducing maintenance costs. Furthermore, the upper cover of this invention extends a first arc-shaped partition and a second arc-shaped partition on the side facing the bottom plate. Both partitions are arc-shaped, so the cavity formed by the two arc-shaped partitions on the upper cover and the annular groove on the bottom plate will be an arc shape. This invention sets the cavity for placing the spring plate as an arc shape, which facilitates the installation personnel in connecting the connecting part 24 (e.g., on the claw pad for docking the second end 42 of the spring plate 4) on the claw pad. Figure 10 Adjust the position accurately as shown.

[0064] Combination Figures 5 to 8 As shown, the base plate body 71 extends upwards to form an arc-shaped connecting plate 73, and the arc-shaped connecting plate 73 extends inwards to form an arc-shaped baffle 74 parallel to the base plate body 71; the base plate body 71 also has an arc-shaped through hole 75, which is located below the arc-shaped baffle 74 and extends to the outside directly below the arc-shaped baffle 74 at both ends; the arc-shaped connecting plate 73, the arc-shaped baffle 74, the arc-shaped through hole 75, and the second arc-shaped partition 63 are all on the same central axis; In the upper cover 6, the second arc-shaped partition 63 is located outside the first arc-shaped partition 62. A third arc-shaped partition 65 extends outward from one end of the second arc-shaped partition 63 towards the bottom plate 7. Protrusions 66 extend downward from both ends of the outer edge of the third arc-shaped partition 65. The third arc-shaped partition 65 is inserted between the arc-shaped baffle 74 and the bottom plate body 71, and the protrusions 66 are inserted into the arc-shaped through holes 75, thereby achieving the snap-fit ​​of the upper cover 6 and the bottom plate 7. Figure 9As shown, the cover plate 61, the arc-shaped baffle 74, and the base plate body 71 are all provided with matching first through holes. Fasteners pass through the first through holes on the three in sequence to fix the spring plate moving cavity 3 formed by the upper cover 6 and the base plate 7 onto the object to be fixed 5. This invention, through the design of the connection mechanism between the upper cover and the base plate, allows for convenient and quick mounting of the upper cover onto the base plate, enabling rapid alignment of the corresponding through holes on the upper cover and the base plate. This facilitates the quick fixing of the spring plate moving cavity formed by the upper cover and the base plate onto the object to be fixed using fasteners, thereby improving the installation efficiency of the spring plate moving cavity.

[0065] Furthermore, both the cover plate 61 and the base plate body 71 have a central through hole 8 for accommodating the claw pad 2. The central through hole 8 on the cover plate 61 is located inside the first arc-shaped partition 62, and the central through hole 8 on the base plate body 71 is located inside the annular groove 72. By providing central through holes sufficient to accommodate the claw pad on both the upper cover and the base plate, this invention ensures that the rotation of the claw pad is unaffected by the spring plate's movement cavity. Figure 7 As shown, a circular retaining ring 76 extends upward from the outer edge of the annular groove 72. After the upper cover 6 is snapped onto the base plate 7, the first arc-shaped partition 62 is located inside the annular groove 72 and abuts against the inner edge of the annular groove 72. The second arc-shaped partition 63 is located outside the circular retaining ring 76 and abuts against the circular retaining ring 76. This invention extends a circular retaining ring upward from the outer edge of the annular groove and positions the second arc-shaped partition outside the circular retaining ring, rather than inside the annular groove. Therefore, when the upper cover is snapped onto the base plate, it is not necessary to specifically align the two arc-shaped partitions in the upper cover with the annular groove, thus further improving the snapping efficiency between the upper cover and the base plate, thereby further improving the installation efficiency of the spring plate moving cavity.

[0066] like Figure 10 As shown, the claw pad 2 may include a pad 21, a fixing block 22, and a connecting part 24. The pad 21 has a second through hole 23 with a radius greater than or equal to the radius of the bolt 1. Multiple fixing blocks 22 extend upward from the pad 21. Each fixing block 22 is circumferentially evenly arranged outside the second through hole 23, and one of the fixing blocks 22 extends outward for contact with the second end 42 of the spring plate 4 (e.g., Figure 4 (As shown) The connecting part 24 is mated. The circumference of the fixing block 22 is concentric with the second through hole 23. Furthermore, it is combined with... Figure 11 and Figure 12 As shown, the second through hole 23 is coaxial with the second arc partition 63 in the spring plate movement cavity, and the connecting part 24 extends to the inner edge of the annular groove 72 to avoid the rotation of the first nut and claw washer being affected by the spring plate movement cavity.

[0067] Furthermore, one end of the distributed sensing fiber in the current threaded structure can be connected to the next threaded structure after exiting the spring plate, and deployed onto the spring plate of that next threaded structure. Thus, a single distributed sensing fiber can be used to measure the loosening of multiple threaded structures. For example... Figure 13 As shown, the universal measurement device for loose threaded structures based on distributed optical fiber sensing may further include a light source, a pulse modulator, a frequency shifter, a circulator, a coupler, a photodetector, a data acquisition unit, a data processor, and a test fiber formed by connecting multiple distributed sensing optical fibers in the threaded structure. The output end of the light source is connected to the pulse modulator and the frequency shifter respectively. The output end of the pulse modulator is connected to the first end of the circulator. The second end of the circulator is connected to one end of the test fiber in sequence, and the third end is connected to the first input end of the coupler. The output end of the frequency shifter is connected to the second input end of the coupler. The output end of the coupler is connected to the data processor in sequence through the photodetector and the data acquisition unit.

[0068] The light source splits continuous light into two paths: a probe beam and a reference beam. The probe beam is periodically injected into the fiber under test (BUT) through a circulator at a certain period. Upon receiving the probe beam, the BUT generates back-propagating Brillouin scattered light, resulting in a Brillouin frequency shift. The back-propagating Brillouin scattered light is transmitted to the coupler through the circulator. The reference beam is injected into the frequency shifter, shifted, and then transmitted to the circulator. The Brillouin scattered light and the frequency-shifted reference beam interfere at the coupler, forming an interference light signal. The photodetector converts the interference light signal into an interference electrical signal. The data acquisition unit acquires the interference electrical signal and sends it to the data processor. The data processor demodulates the changes in the BUT based on the interference electrical signal and determines the looseness of each thread structure based on the changes in each distributed sensing fiber within the BUT. Specifically, when the corresponding change in a distributed sensing fiber in a thread structure exceeds a corresponding threshold, an early warning can be issued for the looseness of that thread structure.

[0069] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0070] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is defined solely by the appended claims.

Claims

1. A universal measuring device for loosening of threaded structures based on distributed optical fiber sensing, characterized in that, The device includes a threaded structure, a claw washer, a spring plate moving cavity, and a spring plate placed inside the spring plate moving cavity. The spring plate is provided with distributed sensing optical fibers. The threaded structure includes a bolt and a first nut. The second end of the bolt passes through the object to be fixed and the claw washer located on the upper surface of the object to be fixed in sequence, and then is threadedly connected to the first nut inside the claw washer. By rotating the first nut, the nut of the bolt abuts against the bottom surface of the object to be fixed, thereby achieving the fastening of the object to be fixed. The first end of the spring plate is connected to the spring plate movement cavity, and the second end is connected to the claw washer. The spring plate movement cavity is fixed to the object to be fixed. When the first nut rotates, the claw washer drives the spring plate to extend and retract along the cavity of the spring plate movement cavity, thereby causing a first change in the distributed sensing optical fiber. Based on the optical signal returned after the distributed sensing optical fiber receives the measurement optical signal, the change of the distributed sensing optical fiber is determined, and based on the change of the distributed sensing optical fiber, the loosening of the threaded structure is determined. The spring sheet is wavy relative to the upper surface of the object to be fixed, and the distributed sensing optical fiber is laid on the spring sheet along the direction of the wave; The spring plate movement cavity includes an upper cover and a bottom plate. The upper cover includes a cover plate and a first arc partition and a second arc partition extending on the cover plate toward the bottom plate. The first arc partition and the second arc partition are on the same central axis, have equal curvature and are aligned at both ends. The first end of the spring plate is snapped into a first buckle between the first arc partition and the second arc partition to fix the first end of the spring plate. The base plate includes a base plate body, on which an annular groove is formed. The space between the annular groove and the first and second arc partitions is matched. After the top cover is installed on the base plate, the space enclosed by the annular groove, the first and second arc partitions constitutes the cavity of the spring plate movement chamber. The claw pad includes a pad, a fixing block, and a connecting part. The pad has a second through hole with a radius greater than or equal to the radius of the bolt. Multiple fixing blocks extend upward from the pad. Each fixing block is circumferentially evenly arranged outside the second through hole, and one of the fixing blocks extends outward to form a connecting part for docking with the second end of the spring sheet.

2. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 1, characterized in that, The first nut rotation includes the following types of rotation: Of the bolt and the first nut, only the first nut rotates in the positive upward direction when subjected to external force; Only when the bolt is subjected to external force and rotates downward, it causes the first nut to rotate in the opposite direction. During the reverse rotation of the first nut, the claw washer abuts against the upper surface of the object to be fixed. When the bolt is rotated downward by an external force, and the first nut is affected by an external force that prevents it from rotating in the opposite direction, the first nut may rotate in the forward or reverse direction.

3. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 1 or 2, characterized in that, Determining the loosening status of the threaded structure based on the changes in the distributed sensing fiber specifically includes: determining whether the changes in the distributed sensing fiber include the first change caused by the rotation of the first nut; if so, determining that the threaded structure has become loose; otherwise, determining that the threaded structure has not become loose.

4. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 3, characterized in that, When installing the thread structure loosening measuring device, first tighten the object to be fixed, then fix the spring plate moving cavity on the object to be fixed, and then connect the second end of the spring plate in the spring plate moving cavity to the claw pad. The first nut is separately and tightly fitted to the claw washer, with the first nut extending out from the claw washer toward the first end of the bolt.

5. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 1, characterized in that, The base plate extends upward to form an arc-shaped connecting plate, and the arc-shaped connecting plate extends inward to form an arc-shaped baffle parallel to the base plate. The base plate also has an arc-shaped through hole, which is located below the arc-shaped baffle and extends to the outside of the arc-shaped baffle at both ends. The arc-shaped connecting plate, the arc-shaped baffle, the arc-shaped through hole, and the second arc-shaped partition are all on the same central axis. The second arc-shaped partition is located outside the first arc-shaped partition, and a third arc-shaped partition extends outward from one end of the second arc-shaped partition facing the bottom plate; The third arc-shaped partition plate has protrusions extending downward from both ends of its outer edge; the third arc-shaped partition plate is inserted between the arc-shaped baffle and the base plate body, and the protrusions are inserted into the arc-shaped through hole, thereby realizing the snap-fit ​​of the top cover and the base plate; The arc-shaped baffle, cover plate and base plate are all provided with matching first through holes. Fasteners pass through the first through holes of the three in sequence to fix the spring plate moving cavity formed by the upper cover and the base plate to the object to be fixed.

6. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 1 or 5, characterized in that, Both the cover plate and the base plate body are provided with a central through hole to accommodate the claw pad. The central through hole on the cover plate is located inside the first arc partition, and the central through hole on the base plate body is located inside the annular groove. A circular retaining ring extends upward from the outer edge of the annular groove. After the upper cover is snapped onto the base plate, the first arc-shaped partition is located inside the annular groove, and the second arc-shaped partition is located outside the circular retaining ring.

7. The universal measuring device for loose threaded structures based on distributed optical fiber sensing according to claim 1, characterized in that, One end of the distributed sensing fiber of the current threaded structure can be connected to the next threaded structure after passing through the spring plate and laid on the spring plate of the next threaded structure. In this way, the loosening measurement of multiple threaded structures can be realized by using a single distributed sensing fiber. It also includes a light source, a pulse modulator, a frequency shifter, a circulator, a coupler, a photodetector, a data acquisition unit, a data processor, and a test fiber formed by multiple distributed sensing fibers connected in series in a threaded structure. The output end of the light source is connected to the pulse modulator and the frequency shifter respectively. The output end of the pulse modulator is connected to the first end of the circulator. The second end of the circulator is connected to one end of the test fiber in sequence, and the third end is connected to the first input end of the coupler. The output end of the frequency shifter is connected to the second input end of the coupler. The output end of the coupler is connected to the data processor in sequence through the photodetector and the data acquisition unit. The light source splits continuous light into two paths: a probe beam and a reference beam. The probe beam is periodically injected into the fiber under test (BUT) through a circulator at a certain period. Upon receiving the probe beam, the BUT generates back-propagating Brillouin scattered light, resulting in a Brillouin frequency shift. The back-propagating Brillouin scattered light is transmitted to the coupler through the circulator. The reference beam is injected into the frequency shifter, shifted, and then transmitted to the circulator. The Brillouin scattered light and the frequency-shifted reference beam interfere at the coupler, forming an interference light signal. The photodetector converts the interference light signal into an interference electrical signal. The data acquisition unit acquires the interference electrical signal and sends it to the data processor. The data processor demodulates the changes in the BUT based on the interference electrical signal and determines the looseness of each thread structure based on the changes in each distributed sensing fiber within the BUT.

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