A piezoelectric fiber intelligent gasket for bolt loosening monitoring and its manufacturing and application methods

Abstract

The present invention discloses a piezoelectric fiber smart gasket for bolt loosening monitoring and a method for making and applying the same. The smart gasket includes a gasket and a piezoelectric fiber sensor. The gasket is composed of a "step-shaped" upper gasket and a "step-shaped" lower gasket meshing together to form a U-shaped groove in the circumferential direction. The piezoelectric fiber sensor is an annular structure, arranged at the U-shaped groove formed by the upper and lower gaskets, and is composed of a sensitive element and epoxy resin. The smart gasket uses a piezoelectric fiber sensor to sense the size of the bolt preload, monitor the output signal change fluctuation, judge the bolt loosening or failure, and realize real-time monitoring of the bolt connection status. The sensitive element of the smart gasket is composed of multiple piezoelectric fibers in an annular array connected in parallel, which can evenly sense the change of the preload acting on the gasket, has high sensitivity, is suitable for various bolt connectors, can withstand certain impact loads, can be used for bolt status monitoring under harsh working conditions, effectively avoids the high labor intensity of traditional manual detection methods, improves monitoring efficiency, and has a wide application market.

Description

Technical Field

[0001] The invention belongs to the technical field of bolt connection state monitoring, and provides a piezoelectric fiber intelligent gasket for bolt loosening monitoring, which is used for real-time monitoring of the bolt connection state. Background Art

[0002] Bolt connections are widely used in machinery, transportation, electricity, civil engineering and other industries as a way to connect detachable parts and transfer loads. The connection status directly affects whether the entire structure or equipment can work properly, and is related to the overall reliability and safety. In long-term operation or in an environment of impact and forced vibration of cyclic loads, bolts often become loose or fail, resulting in a reduction in equipment life, and even causing serious safety accidents and significant property losses. For bolts working in harsh environments and complex working conditions, their tightness and failure are more difficult to judge directly. In order to avoid catastrophic consequences caused by bolts whose connection status does not meet normal requirements, real-time online monitoring of the bolt connection status is particularly important.

[0003] Commonly used bolt tightening force test methods include torque wrench method, resistance strain gauge electrical measurement method, optical measurement mechanics method, etc. However, these test methods generally have low efficiency, inaccurate precision, and are limited by the bolt installation form, and are difficult to implement in many work situations. At present, the bolt connection state detection technology using piezoelectric material active sensing is favored by researchers due to its fast dynamic response, high detection accuracy, high sensitivity, wide application range, and easy use. Its working principle is to use the piezoelectric characteristics of the piezoelectric fiber sensor arranged in the bolt connection to sense physical quantities such as stress and strain, output electrical signals, analyze the relationship between signal energy loss and bolt preload, and judge the bolt connection state.

[0004] Since piezoelectric ceramic sensors are not impact-resistant, easy to break, and have unstable performance, they are difficult to use for a long time in an environment of cyclic load impact and forced vibration. The more common flexible piezoelectric sensors on the market contain metal core piezoelectric fibers and MFC, which are expensive and have complex preparation processes. The piezoelectric performance of PVDF fluctuates greatly due to the influence of ambient temperature. The invention patent with application publication number CN107355464A discloses a stacked piezoelectric ceramic smart gasket for monitoring bolt loosening, which does not overcome the problems of traditional piezoelectric ceramic elements such as high brittleness, high hardness, and low resistance to impact and vibration. The invention patent with application publication number CN109632157A discloses a PVDF piezoelectric film used in a dynamic stress device for a bolt joint surface, which is not suitable for environments with harsh working temperatures.

[0005] Therefore, this patent describes a piezoelectric fiber smart gasket for bolt loosening monitoring and its manufacturing and application methods. The smart gasket is meshed with each other through stepped upper and lower gaskets, and the sensor is placed in the U-shaped groove formed by the meshing, which can effectively prevent the sensor from being damaged due to excessive torque during bolt pre-tightening. Piezoelectric fiber composite materials with certain toughness and piezoelectric properties are used as sensitive elements to efficiently sense the changes in physical quantities of stress and strain between bolt connection interfaces. Multiple piezoelectric fiber annular arrays are connected in parallel to uniformly sense the bolt connection status and increase the output detection signal amplitude. Epoxy resin acts as a protective layer and insulating layer for the sensitive element, which can withstand certain impact loads and vibrations. The preparation process is simple, the processing cost is low, the weather resistance is strong, and it is suitable for complex working conditions. Summary of the invention

[0006] The main purpose of the present invention is to provide a piezoelectric fiber smart gasket for bolt loosening monitoring and a method for making and applying the same, which is intended to monitor the connection status of bolt connectors in real time, and utilize the piezoelectric effect characteristics of the piezoelectric sensor, that is, external force is loaded on the piezoelectric sensor, the external force causes the piezoelectric sensor to deform, and the input mechanical energy is converted into an electrical signal through the piezoelectric effect. A certain amount of periodic excitation is applied to the top of the bolt as a calibration excitation. At this time, the piezoelectric fiber sensor in the smart gasket undergoes a certain deformation, and it uses its own piezoelectric effect characteristics to convert the perceived stress strain into an electrical signal; the electrical signal generated by the piezoelectric fiber sensor in the smart gasket is collected, and this signal is used as a reference signal; the calibration excitation is applied regularly, and the electrical signals collected in different time periods are compared with the reference signal. By monitoring the difference in the signal, the bolt connection status can be judged, and a real-time warning can be given, and the bolts can be tightened or replaced in time.

[0007] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: a piezoelectric fiber smart gasket for bolt loosening monitoring and a manufacturing and application method, characterized in that the smart gasket includes a gasket and a piezoelectric fiber sensor, the gasket is composed of a "step-shaped" upper gasket and a "step-shaped" lower gasket meshing to form a U-shaped groove in the circumferential direction, the piezoelectric fiber sensor is an annular structure, arranged in the U-shaped groove formed by the upper and lower gaskets, and is composed of a sensitive element and epoxy resin.

[0008] Furthermore, the sensitive element includes a plurality of piezoelectric fiber rods arranged radially and in a circular array around the center of a circle, an inner electrode, an outer electrode and a terminal; one end of the piezoelectric fiber rod is connected to the inner electrode, and the other end is connected to the outer electrode, and the piezoelectric fiber rod is arranged in parallel between the inner and outer electrodes. The epoxy resin is used as a protective layer and upper and lower insulating layers of the sensitive element to encapsulate the sensitive element to form an annular piezoelectric fiber sensor.

[0009] Furthermore, a first stepped boss structure is provided in the circumferential direction of the through hole in the "step-shaped" lower gasket, and the outer cylindrical surface of the first stepped boss structure is gap-matched with the through hole in the piezoelectric fiber sensor. A second stepped boss structure is provided in the circumferential direction of the through hole in the "step-shaped" upper gasket, and the protrusions of the first stepped boss structure and the second stepped boss structure are meshed with each other and assembled into a whole to form a smart gasket.

[0010] Furthermore, the material and size of the gasket are selected according to the working conditions of the monitored bolts; the sensitive element is composed of a piezoelectric fiber rod in an annular array and inner and outer electrodes, the diameter of the piezoelectric fiber rod is about 3 / 5 times the height of the U-shaped groove, and the height of the U-shaped groove is 1 / 3 times the total height of the gasket. The sensitive element is in the middle of the epoxy resin, and the encapsulation layer formed by the epoxy resin is evenly distributed on the upper and lower sides of the piezoelectric fiber rod. The overall thickness of the piezoelectric fiber sensor encapsulated by the epoxy resin should be equal to or slightly greater than the height of the U-shaped groove; the epoxy resin is formed by mixing A glue and B glue, A glue is epoxy resin glue, B glue is a curing agent, and the solidified epoxy resin has a certain flexibility; the inner electrode, outer electrode and terminal material are copper.

[0011] A piezoelectric fiber intelligent gasket for bolt loosening monitoring is manufactured, characterized by:

[0012] S1: Fabrication of piezoelectric fiber sensors

[0013] The piezoelectric fiber sensor is molded by mold casting. The mold cavity is an annular groove, whose inner diameter is the required inner through hole diameter of the sensitive element, and the outer diameter is the required diameter of the sensitive element. The cavity depth is the thickness of the sensor. Two through holes are opened on the outer wall of the annular groove for extending the wiring terminals of the inner electrode and the outer electrode. The material of the mold used is a weather glue with easy demoulding and strong tensile strength.

[0014] 1. Cut the piezoelectric fiber rods into a certain length, polish the cut ends, and obtain multiple piezoelectric fiber rods of equal length with smooth ends, and polarize them in a certain temperature and electric field environment;

[0015] 2. Bend the copper strip into an inner electrode and an outer electrode, evenly distribute the two ends of the polarized piezoelectric fiber rod of equal length between the inner and outer electrodes, and bond the fiber rod to the inner and outer electrodes with conductive glue to obtain a sensitive element;

[0016] 3. Apply a mold release agent on the inner surface of the mold cavity for preparing the piezoelectric fiber sensor, cast a thin layer of epoxy resin as a base for the first time, with a thickness of about 1 / 5 of the cavity height, place the sensitive element in the annular groove of the mold, and extend the terminals of the inner and outer electrodes through the two through holes on the outer wall of the cylinder. Cast epoxy resin in the mold cavity for the second time until the cavity is completely filled to achieve the packaging of the piezoelectric sensitive element;

[0017] 4. After the epoxy resin solidifies, demoulding and edge processing are performed, and the terminal is bent into a hole shape to obtain a piezoelectric fiber sensor;

[0018] S2: Assembly of smart gasket

[0019] Lay the prefabricated "step-shaped" lower gasket flat, insert the piezoelectric fiber sensor with a circular inner through hole into the first step-shaped boss structure of the "step-shaped" lower gasket, and use the prefabricated "step-shaped" upper gasket to engage the second step-shaped boss structure with the first step-shaped boss structure to assemble them into a whole, so as to obtain an intelligent gasket with a piezoelectric fiber sensor.

[0020] A piezoelectric fiber intelligent gasket application method for bolt loosening monitoring, characterized in that:

[0021] Align the mounting holes of the connected workpieces, insert the bolts into the mounting holes, install the smart gaskets and nuts, and tighten the threaded connectors with a torque wrench to the set preload. Apply a certain amount of periodic excitation to the top of the bolt as a calibration excitation. At this time, the piezoelectric fiber sensor in the smart gasket undergoes a certain deformation, and uses its own piezoelectric effect characteristics to convert the perceived stress strain into an electrical signal; collect the electrical signal (such as admittance signal or time domain signal, etc.) generated by the piezoelectric fiber sensor in the smart gasket, and use this signal as a reference signal; apply calibration excitation at regular intervals, and compare the electrical signals (such as admittance signal or time domain signal, etc.) collected in different time periods with the reference signal. By monitoring the difference in the signal, the bolt connection status can be judged, real-time warning can be given, and the bolts can be tightened or replaced in time.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention can realize real-time monitoring of the bolt connection status. The piezoelectric fiber sensor is used to efficiently sense the changes in the physical quantities of stress and strain between the bolt connection interfaces. The relationship between the output signal and the bolt preload can be analyzed to determine the bolt connection status, thereby saving the cost of manual inspection. The bolt connection status can be remotely monitored without being disturbed by external environmental factors, thereby reducing the risk of inspection personnel working in high-risk environments.

[0024] (2) The smart gasket is designed with stepped upper and lower gaskets meshing with each other, and the sensor is placed in the U-shaped groove formed by the meshing, which protects the sensor from being damaged by excessive torque during the bolt pre-tightening process. There is no need to modify the standard bolt parts, which avoids the degradation of the bolt connection performance caused by the modified bolts. The designed gasket has fewer structural components and low production cost, and is generally applicable to the working occasions of ordinary gaskets.

[0025] (3) Multiple piezoelectric fiber annular arrays are connected in parallel to form a sensitive element that can evenly sense the bolt connection status, increase the output detection signal amplitude, facilitate result analysis, and improve monitoring and identification accuracy; epoxy resin acts as a protective layer and insulating layer for the sensitive element, which can withstand certain impact loads and vibrations, is suitable for complex working conditions, improves weather resistance, and does not require the insulation layer to be redesigned, which simplifies the manufacturing process and reduces processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A three-dimensional assembly schematic diagram of a piezoelectric fiber smart gasket for bolt loosening monitoring according to the present invention;

[0027] Figure 2 A three-dimensional structural exploded view of a piezoelectric fiber smart gasket for bolt loosening monitoring according to the present invention;

[0028] Figure 3 A gasket assembly diagram of a piezoelectric fiber smart gasket for bolt loosening monitoring according to the present invention;

[0029] Figure 4 This is a structural diagram of a sensitive element of a piezoelectric fiber smart gasket for bolt loosening monitoring according to the present invention;

[0030] Figure 5 A mold structure diagram of a piezoelectric fiber sensor for manufacturing a piezoelectric fiber smart gasket for bolt loosening monitoring according to the present invention;

[0031] Figure 6 The present invention is a schematic diagram of the assembly of components of a piezoelectric fiber smart gasket for monitoring bolt loosening.

[0032] In the picture:

[0033] 1—"stepped" upper gasket, 2—piezoelectric fiber sensor, 3—"stepped" lower gasket, 4—terminal, 5—piezoelectric fiber rod, 6—inner electrode, 7—outer electrode, 8—epoxy resin, 9—mold, 10—U-shaped groove, 31—first stepped boss structure, 32—second stepped boss structure, 91—through hole, 92—annular groove. DETAILED DESCRIPTION

[0034] like Figure 1 As shown in Figures 2 and 3, a piezoelectric fiber smart gasket for bolt loosening monitoring and a manufacturing and application method thereof is characterized in that the smart gasket includes gaskets 1, 3 and a piezoelectric fiber sensor 2. The smart gasket is composed of a "step-shaped" upper gasket 1 and a "step-shaped" lower gasket 3 meshing together to form a U-shaped groove 10 in the circumferential direction. The piezoelectric fiber sensor 2 is an annular structure and is arranged at the U-shaped groove 10 formed by the upper and lower gaskets 1 and 3, and is composed of a sensitive element and an epoxy resin 8.

[0035] like Figure 4 The sensitive element shown includes a plurality of piezoelectric fiber rods 5 arranged radially and in an annular array around the center of a circle, an inner electrode 6, an outer electrode and a terminal 4; one end of the piezoelectric fiber rod 5 is connected to the inner electrode 6, and the other end is connected to the outer electrode 7, and the piezoelectric fiber rod 5 is arranged in parallel between the inner and outer electrodes 6 and 7. The epoxy resin 8 serves as a protective layer and upper and lower insulating layers of the sensitive element, and the sensitive element is encapsulated to form an annular piezoelectric fiber sensor 2.

[0036] The "step-shaped" lower gasket 3 has a first stepped boss structure 31 circumferentially arranged in the inner through hole, and the outer cylindrical surface of the first stepped boss structure 31 is gap-matched with the inner through hole of the piezoelectric fiber sensor 2. The "step-shaped" upper gasket 1 has a second stepped boss structure 32 circumferentially arranged in the inner through hole, and the protrusions of the first stepped boss structure 31 and the second stepped boss structure 32 are meshed with each other and assembled into a whole to form a smart gasket.

[0037] The material and size of the gasket are selected according to the working conditions of the bolts to be monitored; the sensitive element is composed of a piezoelectric fiber rod 5 in an annular array and inner and outer electrodes 6 and 7. The diameter of the piezoelectric fiber rod 5 is about 3 / 5 times the height of the U-shaped groove 10, and the height of the U-shaped groove 10 is 1 / 3 times the total height of the gasket. The sensitive element is in the middle of the epoxy resin 8, and the upper and lower heights of the encapsulation layer formed by the epoxy resin 8 are evenly distributed on the upper and lower sides of the piezoelectric fiber rod 5. The overall thickness of the piezoelectric fiber sensor 2 encapsulated by the epoxy resin 8 should be equal to or slightly greater than the height of the U-shaped groove 10; the epoxy resin 8 is formed by mixing A glue and B glue, A glue is epoxy resin glue, and B glue is a curing agent. The solidified epoxy resin 8 has a certain flexibility; the inner electrode 6, the outer electrode 7 and the terminal 4 are made of copper.

[0038] A piezoelectric fiber intelligent gasket for bolt loosening monitoring is manufactured, characterized by:

[0039] S1: Fabrication of piezoelectric fiber sensor 2

[0040] The piezoelectric fiber sensor 2 is molded by mold casting. Figure 5 As shown, the mold cavity is an annular groove 92, whose inner diameter is the required inner through hole diameter of the sensitive element, and the outer diameter is the required diameter of the sensitive element. The depth of the cavity is the thickness of the piezoelectric fiber sensor. Two through holes 91 are formed on the outer wall of the annular groove 92 for extending the terminals of the inner electrode 6 and the outer electrode 7. The material of the mold used is a weather glue that is easy to demould and has strong tensile strength.

[0041] 1. Cut the piezoelectric fiber rods into a certain length, grind the cut ends, obtain a plurality of piezoelectric fiber rods 5 of equal length with smooth ends, and polarize them in a certain temperature and electric field environment;

[0042] 2. Bend the copper strip into an inner electrode 6 and an outer electrode 7, evenly distribute the two ends of the polarized piezoelectric fiber rod 5 of equal length between the inner and outer electrodes 6 and 7, and bond the piezoelectric fiber rod 5 to the inner and outer electrodes 6 and 7 with conductive adhesive to obtain a sensitive element;

[0043] 3. Apply a mold release agent on the inner surface of the mold cavity prepared by the piezoelectric fiber sensor 2, cast a thin layer of epoxy resin 8 as a base for the first time, with a thickness of about 1 / 5 of the cavity height, put the sensitive element into the annular groove 92 of the mold, and extend the terminals of the inner and outer electrodes 6 and 7 through the two through holes 91 on the outer wall of the cylinder. Cast the epoxy resin 8 in the mold cavity for the second time until the cavity is completely filled to realize the packaging of the piezoelectric sensitive element;

[0044] 4. After the epoxy resin 8 solidifies, demoulding and edge processing are performed, and the terminal 4 is bent into a hole shape to obtain the piezoelectric fiber sensor 2;

[0045] S2: Assembly of smart gasket:

[0046] Lay the prefabricated "step-shaped" lower gasket 3 flat, insert the piezoelectric fiber sensor 2 with a circular inner through hole into the first step-shaped boss structure 31 of the "step-shaped" lower gasket 3, and use the prefabricated "step-shaped" upper gasket 1 to engage the second step-shaped boss structure 32 with the first step-shaped boss structure 31 to assemble into a whole, so as to obtain a smart gasket with a piezoelectric fiber sensor 2.

[0047] A piezoelectric fiber intelligent gasket application method for bolt loosening monitoring, characterized in that:

[0048] Align the mounting holes of the connected workpieces, insert the bolts into the mounting holes, install the smart gaskets and nuts, and tighten the threaded connectors with a torque wrench to the set preload. Apply a certain amount of periodic excitation to the top of the bolt as a calibration excitation. At this time, the piezoelectric fiber sensor 2 in the smart gasket undergoes a certain deformation, and uses its own piezoelectric effect characteristics to convert the perceived stress strain into an electrical signal; collect the electrical signal (such as an admittance signal or a time domain signal, etc.) generated by the piezoelectric fiber sensor 2 in the smart gasket, and use this signal as a reference signal; apply calibration excitation regularly, and compare the electrical signals (such as admittance signals or time domain signals, etc.) collected in different time periods with the reference signal. By monitoring the difference in the signal, the bolt connection status can be judged, real-time warnings can be given, and the bolts can be tightened or replaced in time.

Claims

1. A piezoelectric fiber smart gasket for bolt loosening monitoring, characterized in that: The smart gasket includes a gasket and a piezoelectric fiber sensor. The gasket is composed of a "step-shaped" upper gasket and a "step-shaped" lower gasket meshing to form a U-shaped groove in the circumferential direction. The piezoelectric fiber sensor is an annular structure, arranged in the U-shaped groove formed by the upper and lower gaskets, and is composed of a sensitive element and epoxy resin. A first stepped boss structure is provided in the circumferential direction of the through hole in the "step-shaped" lower gasket, and the outer cylindrical surface of the first stepped boss structure is gap-matched with the through hole in the piezoelectric fiber sensor. A second stepped boss structure is provided in the circumferential direction of the through hole in the "step-shaped" upper gasket, and the protrusions of the first stepped boss structure and the second stepped boss structure are meshed with each other and assembled into a whole to form a smart gasket.

2. The piezoelectric fiber smart gasket for bolt loosening monitoring according to claim 1 is characterized in that: The sensitive element comprises a plurality of piezoelectric fiber rods arranged radially and arranged in a circular array around a center, an inner electrode, an outer electrode and a connection terminal; One end of the piezoelectric fiber rod is connected to the inner electrode, and the other end is connected to the outer electrode. The piezoelectric fiber rod is arranged in parallel between the inner and outer electrodes. The epoxy resin is used as a protective layer and upper and lower insulating layers of the sensitive element to encapsulate the sensitive element to form an annular piezoelectric fiber sensor.

3. A piezoelectric fiber smart gasket for bolt loosening monitoring according to claim 1 or 2, characterized in that: The material and size of the gasket are selected according to the working conditions of the monitored bolts; the sensitive element is composed of a piezoelectric fiber rod in an annular array and inner and outer electrodes, the diameter of the piezoelectric fiber rod is 3 / 5 times the height of the U-shaped groove, and the height of the U-shaped groove is 1 / 3 times the total height of the gasket; the sensitive element is in the middle of the epoxy resin, and the packaging layer formed by the epoxy resin is evenly distributed on the upper and lower sides of the piezoelectric fiber rod, and the overall thickness of the piezoelectric fiber sensor encapsulated by the epoxy resin should be equal to or slightly greater than the height of the U-shaped groove; the epoxy resin is formed by a mixture of A glue and B glue, A glue is epoxy resin glue, and B glue is a curing agent, and the solidified epoxy resin has a certain flexibility; the outer electrode, inner electrode and terminal materials are copper.

4. A method for manufacturing a piezoelectric fiber smart gasket for bolt loosening monitoring, characterized in that: Used to manufacture the piezoelectric fiber smart gasket for bolt loosening monitoring according to any one of claims 1 to 3, S1: Fabrication of piezoelectric fiber sensors The piezoelectric fiber sensor is molded by mold casting. The mold cavity is an annular groove, whose inner diameter is the required inner through hole diameter of the sensitive element, and the outer diameter is the required diameter of the sensitive element. The cavity depth is the thickness of the sensor. Two through holes are opened on the outer wall of the annular groove for extending the wiring terminals of the inner electrode and the outer electrode. The material of the mold used is a weather glue with easy demoulding and strong tensile strength.

1. Cut the piezoelectric fiber rods into a certain length, polish the cut ends, and obtain multiple piezoelectric fiber rods of equal length with smooth ends, and polarize them in a certain temperature and electric field environment; 2. Bend the copper strip into an inner electrode and an outer electrode, evenly distribute the two ends of the polarized piezoelectric fiber rod of equal length between the inner and outer electrodes, and bond the fiber rod to the inner and outer electrodes with conductive glue to obtain a sensitive element; 3. Apply a mold release agent on the inner surface of the mold cavity for preparing the piezoelectric fiber sensor, cast a thin layer of epoxy resin as a base for the first time, with a thickness of 1 / 5 of the cavity height, place the sensitive element in the annular groove of the mold, and extend the terminals of the inner and outer electrodes through the two through holes on the outer wall of the cylinder. Cast epoxy resin in the mold cavity for the second time until the cavity is completely filled to achieve the packaging of the piezoelectric sensitive element; 4. After the epoxy resin solidifies, demoulding and edge processing are performed, and the terminal is bent into a hole shape to obtain a piezoelectric fiber sensor; S2: Assembly of smart gasket Lay the prefabricated "step-shaped" lower gasket flat, insert the piezoelectric fiber sensor with a circular inner through hole into the first step-shaped boss structure of the "step-shaped" lower gasket, and use the prefabricated "step-shaped" upper gasket to engage the second step-shaped boss structure with the first step-shaped boss structure to assemble them into a whole, so as to obtain an intelligent gasket with a piezoelectric fiber sensor.

5. A piezoelectric fiber smart gasket application method for bolt loosening monitoring, characterized in that: The piezoelectric fiber smart gasket for bolt loosening monitoring according to any one of claims 1 to 3 is used. Align the mounting holes of the connected workpieces, insert the bolts into the mounting holes, install the smart gaskets and nuts, and tighten the threaded connectors with a torque wrench to the set preload. Apply a certain amount of periodic excitation to the top of the bolts as a calibration excitation. At this time, the piezoelectric fiber sensor in the smart gasket undergoes a certain deformation, and uses its own piezoelectric effect characteristics to convert the perceived stress strain into an electrical signal. The electrical signal generated by the piezoelectric fiber sensor in the smart gasket is collected and used as the reference signal. Calibration excitation is applied regularly to compare the electrical signals collected in different time periods with the reference signal. By monitoring the degree of difference in the signal, the state of the bolt connection can be determined, and real-time warning can be given to tighten the bolts or replace them in time.

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