CN115127702A - Capacitive self-sensing bolt and detection method thereof - Google Patents

Abstract

The invention discloses a capacitive self-sensing bolt and a detection method thereof. The structure is an integral device composed of a concave nut, a screw, a capacitive pressure element, a wireless transmission system and ancillary components. The inner concave nut is based on the traditional nut to open a cylindrical hole and groove, and a disc buckle is installed at the bottom of the hole and groove, and a small round hole is opened at the bottom of the cylindrical hole. On the basis, a cylindrical hole that runs through the entire screw rod corresponds to the cylindrical hole and groove of the concave nut. The capacitive pressure element adopts a cylindrical form that matches the cylindrical hole of the screw rod. The wireless transmission system is composed of a data acquisition and storage unit, a wireless signal transmission system and a built-in power supply element, and is equipped with a backup power supply. The auxiliary components include a sealing rubber ring, a buckle, a waterproof sealant, and an insulating filler. The grooves and holes of the concave nut and the screw are sealed to ensure the normal operation of the wireless transmission system and the capacitive pressure sensor.

Description

A capacitive self-sensing bolt and its detection method

technical field

The invention relates to capacitive self-sensing bolts and detection technology.

Background technique

Bolted connection is a widely used connection method in the field of engineering structures. It has the advantages of convenient disassembly and assembly and strong reliability. Bolts are widely used in bridge structures, rail transit, aerospace, automobile industry, special equipment, chemical pipelines, etc. . However, various structural damage problems and operation and maintenance problems caused by bolt damage and loosening cannot be ignored. Especially in the aerospace field, major accidents are often caused by neglecting a small bolt loosening. The bolted connection structure is the most commonly used mechanical connection method. Affected by the surface roughness, the joint surface of the two parts connected by bolts will undergo elastic deformation under external loading, so the joint surface shows a complex appearance. mechanical properties. It is worth noting that the internal damage of the bolt and the external loosening problem do not directly lead to the collapse of the structure in most cases, but the continuous accumulation of damage will lead to catastrophic consequences. Therefore, monitoring the loosening of bolted connections has important theoretical significance and engineering practical value.

The most primitive identification method is manual inspection method, which can be divided into two types: visual inspection method and sound inspection method. The manual recognition method is currently the simplest and most widely used method. Visual inspection is to observe the changes and discoloration of metal parts with the naked eye. It can also be judged whether the bolt is loose by drawing a continuous line on the nut and the connected part, and observing the staggered distance of the line within a certain period of time. Beating is to judge whether there is slack or other abnormality from the sound by hitting the bolt connection part. For example, a railway worker hits a steel rail with a hammer and finds a loose bolt from the abnormal sound. The actual loosening identification method for bolt detection at this stage is still mainly based on manual marking. The red line and the blue line represent the marking lines drawn during regular inspection at different time points, and there are obvious differences between the two different color lines. The staggered distance of , indicates that the bolts are loose during this period of time. The advantage of this method is that it is simple and easy to understand, but the accuracy and efficiency are low. When a large number of bolts are used in the structure, the inspection amount is large. The working state of the bolt can only be detected by surface observation, and the internal force of the structure cannot be judged. The complex environment of the connection requires the inspector to climb to a high place, so the potential safety risk is high; the patent provides a new capacitive self-sensing bolt design and its inspection method, which can not only detect the working and stress state of the bolt, and also detect the state of the bolt. Evaluation, and self-monitoring is achieved through the internal self-perception system and wireless transmission system, which avoids manual detection accuracy and low efficiency, and reduces the risk of manual inspection of high-risk structures. Its shock resistance, signal anti-interference, and structural stability are stronger.

The identification and monitoring of loose bolts is a hot issue to be solved urgently in the field of engineering structures. This problem has not been solved well since the Industrial Revolution. Therefore, it is urgent to propose a new type of capacitive self-sensing bolt design and its detection method. The purpose is to design a new type of bolt structure and propose an online detection and monitoring method for bolt loosening, thereby reducing the number of manual inspections, the occurrence rate of safety accidents caused by bolts, and the cost of manual operation and maintenance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a capacitive self-sensing bolt and a detection method thereof.

The present invention is a capacitive self-sensing bolt and a detection method thereof. The capacitive self-sensing bolt includes an inner concave nut 1, a screw rod 2, and a capacitive pressure element 3. The bottom of the inner concave nut 1 is opened to take a circle The grooves 1-9 are connected to the top of the screw rod 2, and the inner concave nut 1 is, from top to bottom, the chuck 1-8, the wireless transmission system 1-4, the backup power supply 1-3, and the circular cover. 1-2 and hexagonal bolt 1-1, cut a cylindrical hole 2-1 through the whole screw 2 at the center of the circular section at the bottom of the screw 2, and the hole is not larger than 1/4 of the diameter of the screw 2, and Corresponding to the circular hole groove 1-9 of the concave nut 1, and the diameter of the circular hole groove 1-9 is not larger than 1/2 of the cylindrical hole 2-1, the shape of the built-in capacitive pressure element 3-1 Consistent with the size and cylindrical hole 2-1, the two are connected by cementation, and spot welding is carried out at the bottom of the cylindrical hole 2-1, and the threading section 2 at the bottom of the cylindrical hole 2-1 is close to the bottom. -2 is mechanically connected with Phillips screw 3-2.

The method for detecting a capacitive self-sensing bolt of the present invention includes the following steps:

Step (1) Ensure the tightness of the bottom of the screw 2 and the threading section 2-2 to meet the corresponding gap error and clearance level, determine the type, specification, size, material and heat treatment process of the screw 2, so that after the data transmission Determine the conversion of the corresponding capacitor charge and discharge parameters;

Step (2) Check the connection between the signal output line 3-1a of the capacitive piezoelectric element 3-1 and the wireless transmission system 1-4, and the backup power supply 1-3 is connected to the wireless transmission system 1-4 through the wedge-shaped buckle For connection, the wedge-shaped buckles 1-3a are fixed and powered by metal conductive material to ensure the stability of the internal transmission line and power supply;

Step (3) Make sure that the lead screw 2 of the capacitive self-sensing bolt is in a stressed state, open the circular cover 1-2, and turn on the backup power supply 1-3 and the wireless transmission system 1-4 inside the concave nut 1 Finally, through the circular cover plate 1-2 and the hexagonal bolt 1-1, the inner concave nut 1 is used to monitor the stability of the bolt signal through the acquisition terminal on site;

Step (4) According to the material type, specification and size, material density, elastic modulus, Poisson's ratio and electrical conductivity of the capacitive self-sensing bolt, calculate the capacitance output and voltage through the formula in the background of the PC terminal for the measurement circuit signal. Transform the stress, and calculate the stress limit of the bolted structure to determine the early warning value of the structure, then adjust the detection frequency corresponding to each bolt and sort the bolts by number;

Step (5) When detecting the capacitive self-sensing bolt, the signal-to-noise ratio in the output detection signal is not less than 3:1, and the detection frequency adjusted in the fourth step is uploaded to the monitoring service platform for recording and storage in real time. Set different early warning values according to the type of bolts, alarm the abnormal signals generated in the work, and notify the relevant maintenance personnel to re-inspect and replace the corresponding bolts according to the bolt number.

The advantages of the present invention are: 1. The capacitive pressure element is installed inside the screw rod of the present invention, and the force change of the screw rod can be accurately collected under external force, and the screw rod can protect the capacitive pressure element. , to avoid the damage caused by the external uncertain factors of the sensor, the part in contact with the external environment is sealed and fixed with a cross screw, and the circuit of the capacitive pressure element is connected inside the screw rod and the inner concave nut to avoid leakage of the circuit. Causes breakage and damage of the transmission line, prolongs its service life, and ensures the authenticity and validity of the measurement signal;

2. The inner concave nut of the present invention can ensure the stability of the wireless transmission system and the backup power supply. It is sealed with the inner concave nut and is sealed by a circular cover to prevent the wireless transmission system and the backup power supply from being caused by changes in the external environment. The round cover and the concave nut have a certain rigidity to form a closed space, and can resist the impact of external loads to ensure the safety of the internal structure. The system and the concave nut are connected by a chuck, which is interlocked, and the gap is filled with an insulating filler, which ensures the stability of the internal structure and prevents the leakage and short circuit of the backup power supply from affecting the wireless transmission system and capacitive pressure elements. damage;

3. The exterior of the capacitive self-sensing bolt of the present invention forms a whole, and has a strong ability to resist external non-monitoring loads. It adopts wireless transmission to avoid the line damage problem of traditional wired transmission and the clutter of lines when a large number of arrangements are made. It can be used under various conditions. This bolt has a wide range of applications, simple installation, strong stability and data measurement effectiveness;

4. The self-induction principle of the capacitive self-sensing bolt of the present invention is that the external load acts on the screw rod, and the load is transmitted to the built-in capacitive pressure element through the screw rod, causing the change of the internal current of the capacitive pressure element, and the The current change is transmitted to the wireless signal system inside the concave nut through the signal transmission line. The wireless signal system records the current change and transmits it to the signal acquisition terminal to monitor the force state of the bolt in real time. Bolts can be inspected or replaced immediately to ensure the safety and stability of the structure and reduce structural damage caused by bolt damage and loosening;

5. The parts involved in the self-sensing bolt device of the present invention can be easily realized by using the current processing technology. After corresponding prefabrication in the factory, it is assembled on site, with strong processing performance and strong connectivity.

Description of drawings

1 is an overall view of the capacitive self-sensing bolt of the present invention, FIG. 2 is a cross-sectional view of the capacitive self-sensing bolt, FIG. 3 is a cross-sectional view of the internal device installation of the concave nut, and FIG. 4 is the interior of the concave nut Fig. 5 is a structural diagram of a screw rod, Fig. 6 is a schematic structural diagram of a capacitive pressure element, Fig. 7 is an internal detailed view of a capacitive pressure element, Fig. 8 is a flow chart of a capacitive self-sensing bolt detection method, and Fig. 9 is a capacitive pressure element Schematic diagram of self-sensing bolt built-in capacitive piezoelectric element monitoring bolt force change data, among which, 1: concave nut, 1-1: hexagonal bolt, 1-2: circular cover, 1-3: spare Power supply, 1-3a: Wedge-shaped clip, 1-4: Wireless transmission system, 1-4a: L-shaped clip, 1-5: Nut barrel, 1-6: Top screw hole, 1-7: Nut Bottom plate, 1-8: Chuck, 1-9: Circular hole slot. 2: Screw, 2-1: Cylindrical hole, 2-2: Thread section, 3: Capacitive pressure element, 3-1: Built-in capacitive pressure element, 3-1a: Signal output line, 3-1b: Glass layer, 3-1c: Isolation diaphragm, 3-1d: Sensing channel, 3-1e: Measuring membrane, 3-1f: Base, 3-1g: Metal membrane, 3-1h, Metal protective case, 3-2 :Phillips screws.

Detailed ways

The present invention is a capacitive self-sensing bolt and a detection method thereof. The capacitive self-sensing bolt includes an inner concave nut 1, a screw rod 2, and a capacitive pressure element 3. The bottom of the inner concave nut 1 is opened to take a circle The grooves 1-9 are connected to the top of the screw rod 2, and the inner concave nut 1 is, from top to bottom, the chuck 1-8, the wireless transmission system 1-4, the backup power supply 1-3, and the circular cover. 1-2 and hexagonal bolt 1-1, cut a cylindrical hole 2-1 through the whole screw 2 at the center of the circular section at the bottom of the screw 2, and the hole is not larger than 1/4 of the diameter of the screw 2, and Corresponding to the circular hole groove 1-9 of the concave nut 1, and the diameter of the circular hole groove 1-9 is not larger than 1/2 of the cylindrical hole 2-1, the shape of the built-in capacitive pressure element 3-1 Consistent with the size and cylindrical hole 2-1, the two are connected by cementation, and spot welding is carried out at the bottom of the cylindrical hole 2-1, and the threading section 2 at the bottom of the cylindrical hole 2-1 is close to the bottom. -2 is mechanically connected with Phillips screw 3-2.

For the capacitive self-sensing bolts described above, the L-shaped buckles 1-4a at the bottom of the wireless transmission system 1-4 in the concave nut 1 correspond to the openings of the chucks 1-8, and then rotated and fixed, and the backup power supply 1-3 Through the wedge-shaped buckle 1-3a at the bottom and the card hole on the upper part of the wireless transmission system 1-4, they are fixed by pressing to ensure that the wireless transmission system 1-4 and the backup power supply 1-3 It is stable to prevent it from hitting the inner wall of the concave nut 1 and causing damage. The circular cover plate 1-2 is connected and fixed with the top screw hole 1-6 on the concave nut 1 through the hexagonal bolt 1-1.

For the capacitive self-sensing bolts described above, the shape, size and length of the capacitive pressure element 3 are consistent with the cylindrical hole 2-1 of the screw rod 2, and the two are connected by glue and point through the bottom of the cylindrical hole 2-1 Solder to fix the capacitive pressure element 3-1, and finally fix and seal it with the bottom cross screw 3-2; the capacitive pressure element 3 consists of the outer metal protective shell 3-1h, the base 3-1f, the isolation diaphragm 3-1c, The measuring film 3-1e, the glass layer 3-1b, the metal film 3-1g, the sensing channel 3-1d, and the signal output line 3-1a are composed.

For the capacitive self-sensing bolts mentioned above, the metal protective shell 3-1h protects the capacitive pressure element 3 as a whole, the base 3-1f is used to ensure the stability of the internal structure and the validity of the output measurement value, and the isolation diaphragm 3-1c is used to isolate the metal protective shell 3-1h from the internal structure and play the role of transferring loads, the metal film 3-1g is used to separate the glass layer 3-1b and the internal measurement unit, and the glass layer 3-1b is used to protect the interior The measurement unit separates the outer base 3-1f, when the external load changes, the force is transmitted to the induction channel 3-1d through the isolation diaphragm 3-1c, and the internal capacitance changes through the compression or tension of the induction channel 3-1d , so that the measurement film 3-1e at the position of the central axis of the structure is offset, and the change of the internal capacitance causes the change of the current. Finally, the change of the current is outputted through the signal output line 3-1a to achieve the purpose of monitoring the force change of the bolt. .

The capacitive self-sensing bolts described above are mechanically connected by the integral capacitive pressure element 3 and the cylindrical hole 2-1 of the screw rod 2, and are fixed and sealed by pressing the sealing rubber ring through the cross screw 3-2. The signal output line 3-1a of the type pressure element 3 passes through the circular hole slot 1-9 in the concave nut 1 corresponding to the wire hole and is connected to the wireless transmission system 1-4, and the backup power supply 1-3 passes through The wedge-shaped buckle 1-3a is fixed with the wireless transmission system 1-4. Finally, the circular cover plate 1-2 and the hexagonal bolt 1-1 are used to seal the inner concave nut 1 to ensure the capacitive pressure element inside the whole bolt. 3. The wireless transmission system 1-4 and the backup power supply 1-3 will not cause internal damage due to rain erosion and impact in the external environment.

For the capacitive self-sensing bolt described above, when the external load acts on the screw 2, the force is transmitted to and acts on the internal capacitive pressure element 3, and the current change is transmitted to the wireless transmission system through the signal output line 3-1a 1-4. Power supply and support through the built-in power supply components of the backup power supply 1-3 and the wireless transmission system 1-4, record data and transmit the load changes on the screw rod 2 to the acquisition terminal.

The method for detecting a capacitive self-sensing bolt of the present invention includes the following steps:

Step (1) Ensure the tightness of the bottom of the screw 2 and the threading section 2-2 to meet the corresponding gap error and clearance level, determine the type, specification, size, material and heat treatment process of the screw 2, so that after the data transmission Determine the conversion of the corresponding capacitor charge and discharge parameters;

Step (2) Check the connection between the signal output line 3-1a of the capacitive piezoelectric element 3-1 and the wireless transmission system 1-4, and the backup power supply 1-3 is connected to the wireless transmission system 1-4 through the wedge-shaped buckle For connection, the wedge-shaped buckles 1-3a are fixed and powered by metal conductive material to ensure the stability of the internal transmission line and power supply;

Step (3) Make sure that the lead screw 2 of the capacitive self-sensing bolt is in a stressed state, open the circular cover 1-2, and turn on the backup power supply 1-3 and the wireless transmission system 1-4 inside the concave nut 1 Finally, through the circular cover plate 1-2 and the hexagonal bolt 1-1, the inner concave nut 1 is used to monitor the stability of the bolt signal through the acquisition terminal on site;

Step (4) According to the material type, specification and size, material density, elastic modulus, Poisson's ratio and electrical conductivity of the capacitive self-sensing bolt, calculate the capacitance output and voltage through the formula in the background of the PC terminal for the measurement circuit signal. Transform the stress, and calculate the stress limit of the bolted structure to determine the early warning value of the structure, then adjust the detection frequency corresponding to each bolt and sort the bolts by number;

Step (5) When detecting the capacitive self-sensing bolt, the signal-to-noise ratio in the output detection signal is not less than 3:1, and the detection frequency adjusted in the fourth step is uploaded to the monitoring service platform for recording and storage in real time. Set different early warning values according to the type of bolts, alarm the abnormal signals generated in the work, and notify the relevant maintenance personnel to re-inspect and replace the corresponding bolts according to the bolt number.

The technical content of the present invention is further developed below in conjunction with the embodiments. As shown in Figure 1 and Figure 2, the overall structure of the capacitive self-sensing bolt is composed of a concave nut 1, a lead screw 2, and a capacitive pressure element 3, of which the concave nut 1 and the lead screw 2 are formed. In the overall structure, the capacitive pressure element 3 is built in the cylindrical hole 2 - 1 of the screw rod 2 .

As shown in Figures 3 and 4, it is the internal structure of the concave nut 1, in which the hexagonal bolt 1-1 and the circular cover plate 1-2 are used to seal the concave nut 1 to reduce external loads Impact damage to the internal structure, and prevent the short circuit and corrosion of the internal structural unit caused by rain erosion; the wireless transmission system 1-4 is connected and fixed with the chuck 1-8 at the bottom of the nut barrel 1-5 through the L-shaped buckle at the bottom, The circular hole slot 1-9 is used for the wire hole through which the transmission line of the lower capacitive pressure element 3 passes. The backup power supply 1-3 is connected and fixed with the wedge-shaped card on the top of the wireless transmission system 1-4 through the wedge-shaped clip 1-3a at the bottom. , and the gaps in the nut barrels 1-5 are filled with insulating materials, and the surfaces of the wireless transmission system 1-4 and the backup power supply 1-3 are painted with insulating paint to prevent equipment damage caused by short circuits.

As shown in Figure 6, which is the structure diagram of the screw rod 2, a cylindrical hole 2-1 is drilled on the screw rod 2 by a drilling machine, and the bottom section of the cylindrical hole 2-1 is covered with wire. 2 The length is not more than 1/6 of the total length.

As shown in Figures 6 and 7, the capacitive pressure element 3 consists of a signal output line 3-1a, a glass layer 3-1b, an isolation diaphragm 3-1c, a sensing channel 3-1d, a measurement film 3-1e, a base The seat 3-1f, the metal film 3-1g, the metal protective shell 3-1h, the size of the capacitive pressure element 3 is the same as the cylindrical hole 2-1 of the screw rod 2, and the signal output line 3-1a passes through the cylindrical hole 2-1 It is connected with the circular hole groove 1-9 at the bottom of the concave nut 1 and the wireless transmission system, and the thread section 2-2 at the bottom of the screw rod 2 is fixed and sealed with a cross screw 3-2 of the same length.

As shown in Figure 8 and Figure 9, in order to detect the flow chart and the force change diagram of the lead screw 2, first check whether the capacitive self-sensing bolt is damaged, and then determine the conversion relationship between the capacitive charge and discharge parameters according to the type of bolt, and secondly Turn on the backup power supply 1-3 and the wireless transmission system 1-4 in the concave nut 1, number the monitored bolts, record the data through the wireless transmission system 1-4 and upload it to the acquisition terminal, and finally set according to the type of bolt Early warning value, alarm for abnormal signals; the figure also provides the signal detected by the internal capacitive piezoelectric element 3-1 when the external load acts on the screw 2, and the force transformation of the bolt is obtained through the corresponding conversion relationship. The type and material calculation and analysis of bolts set warning values.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (7)

1. A capacitive self-sensing bolt, comprising an inner concave nut (1), a lead screw (2), and a capacitive pressure element (3), characterized in that a circle is drawn at the bottom of the inner concave nut (1). The groove (1-9) penetrates to the top of the screw (2), and the inner concave nut (1) from top to bottom is the chuck (1-8), wireless transmission system (1-4), For the backup power supply (1-3), the circular cover plate (1-2) and the hexagonal bolt (1-1), cut a cylinder running through the entire screw (2) at the center of the circular section at the bottom of the screw (2). hole (2-1), and the hole is not larger than 1/4 of the diameter of the screw (2), and corresponds to the circular hole groove (1-9) of the concave nut (1), and the circular hole The diameter of the groove (1-9) is not larger than 1/2 of the cylindrical hole (2-1), and the shape and size of the built-in capacitive pressure element (3-1) are consistent with the cylindrical hole (2-1). They are connected by cementation, and fixed by spot welding at the bottom of the cylindrical hole (2-1). 3-2) By mechanical connection. 2. The capacitive self-sensing bolt according to claim 1, characterized in that: the L-shaped buckle (1-4a) at the bottom of the wireless transmission system (1-4) in the concave nut (1) and the The openings of the disk (1-8) correspond to each other, then rotate and fix, the backup power supply (1-3) is fixed by pressing the wedge-shaped buckle (1-3a) at the bottom and the card hole at the upper part of the wireless transmission system (1-4), The circular cover plate (1-2) is connected and fixed with the cap screw hole (1-6) on the concave nut (1) by the hexagonal bolt (1-1). 3. The capacitive self-sensing bolt according to claim 1, characterized in that: the shape, size and length of the capacitive pressure element (3) are consistent with the cylindrical hole (2-1) of the screw (2), and two The capacitor pressure element (3-1) is fixed by glue connection and spot welding through the bottom of the cylindrical hole (2-1), and finally fixed and sealed by the bottom Phillips screw (3-2); the capacitive pressure element (3-2) ) consists of outer metal protective shell (3-1h), base (3-1f), isolation diaphragm (3-1c), measuring film (3-1e), glass layer (3-1b), metal film (3 -1g), induction channel (3-1d), signal output line (3-1a). 4. The capacitive self-sensing bolt according to claim 1, characterized in that: the metal protective shell (3-1h) protects the capacitive pressure element (3) as a whole, and the base (3-1f) is used to ensure the internal The stability of the structure ensures the validity of the output measurement value. The isolation diaphragm (3-1c) is used to isolate the metal protective shell (3-1h) from the internal structure and play the role of transferring the load. The metal film (3-1g) is used for To separate the glass layer (3-1b) and the internal measurement unit, the glass layer (3-1b) is used to protect the internal measurement unit and separate the external base (3-1f), when the external load changes, through the isolation diaphragm ( 3-1c) The force is transmitted to the sensing channel (3-1d), and the internal capacitance changes caused by the compression or stretching of the sensing channel (3-1d), so that the measurement membrane (3-1e) at the position of the central axis of the structure is biased. The change of the current will be caused by the change of the internal capacitance. Finally, the change of the current will be output as a signal through the signal output line (3-1a), so as to achieve the purpose of monitoring the change of the bolt force. 5. The capacitive self-sensing bolt according to claim 1, characterized in that: the integral capacitive pressure element (3) is mechanically connected with the cylindrical hole (2-1) of the screw (2), and is passed through The Phillips screw (3-2) is pressed against the sealing rubber ring for fixed sealing, and the signal output line (3-1a) of the capacitive pressure element (3) passes through the circular hole in the concave nut (1) corresponding to the wire hole The holes (1-9) are passed out and connected to the wireless transmission system (1-4), and the backup power supply (1-3) is fixed to the wireless transmission system (1-4) through the wedge-shaped buckle (1-3a), and finally the The circular cover plate (1-2) and the hexagonal bolt (1-1) seal the female nut (1). 6. The capacitive self-sensing bolt according to claim 1, characterized in that: when an external load acts on the lead screw (2), the acting force is transmitted to and acts on the internal capacitive pressure element (3), and its current changes The situation is transmitted to the wireless transmission system (1-4) through the signal output line (3-1a), and the power supply is supported by the backup power supply (1-3) and the built-in power supply element of the wireless transmission system (1-4), recording data and wire The load changes on the rod (2) are transmitted to the acquisition terminal. 7. the detection method of capacitive self-sensing bolt according to claim 1, is characterized in that, its step is: Step (1) Ensure that the sealing of the bottom of the screw (2) and the threading section (2-2) meet the corresponding clearance error and clearance level, and determine the type, specification, size, material and heat treatment process of the screw (2). , to determine the conversion of the corresponding capacitor charge and discharge parameters after data transmission; Step (2) Check the connection between the signal output line (3-1a) of the capacitive piezoelectric element (3-1) and the wireless transmission system (1-4). 3a) The connection with the wireless transmission system (1-4), the wedge-shaped buckle (1-3a) is fixed and powered by metal conductive material to ensure the stability of the internal transmission line and power supply; Step (3) Make sure that the lead screw (2) of the capacitive self-sensing bolt is in a stressed state, open the circular cover (1-2), and connect the backup power supply (1-3) inside the concave nut (1). And the wireless transmission system (1-4) is turned on, and finally the concave nut (1) is installed through the circular cover plate (1-2) and the hexagonal bolt (1-1), and the signal of the bolt is monitored on the spot through the acquisition terminal. stability; Step (4) According to the material type, specification and size, material density, elastic modulus, Poisson's ratio and electrical conductivity of the capacitive self-sensing bolt, calculate the capacitance output and voltage through the formula in the background of the PC terminal for the measurement circuit signal. Transform the stress, and calculate the stress limit of the bolted structure to determine the early warning value of the structure, then adjust the detection frequency corresponding to each bolt and sort the bolts by number; Step (5) When detecting the capacitive self-sensing bolt, the signal-to-noise ratio in the output detection signal is not less than 3:1, and the detection frequency adjusted in the fourth step is uploaded to the monitoring service platform for recording and storage in real time. Set different early warning values according to the type of bolts, alarm the abnormal signals generated in the work, and notify the relevant maintenance personnel to re-inspect and replace the corresponding bolts according to the bolt number.

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