Intelligent pre-tightening force monitoring and self-adjusting connection box

Abstract

The application discloses a kind of intelligent pre-tightening force monitoring and self-regulating connecting box, including connecting box body, bolt connection component, piezoelectric ceramic pre-tightening force sensing layer and hydraulic self-regulating gasket.Piezoelectric ceramic sensing layer is embedded in connecting box inner wall or adjacent with bolt contact surface, forming annular or sheet piezoelectric film array.Hydraulic self-regulating gasket is arranged between nut and connecting box or connecting plate, and is internally provided with micro-hydraulic cavity with thickness of 5-8mm, elastic diaphragm and one-way liquid supplementing structure, when detecting that pre-tightening force is lower than set threshold, micro-hydraulic cavity automatically compensates pressure.Connecting box body uses high-strength aluminum alloy and / or fiber-reinforced composite material, and inner wall forms buffer boss to reduce stress concentration.The application integrates internet of things monitoring and passive pre-tightening force compensation in connecting box, improves bolt pre-tightening force control precision and long-term shear resistance reliability.

Description

Technical Field

[0001] This invention relates to the field of bolt connection and structural health monitoring technology, specifically to an intelligent connection box that integrates real-time monitoring and automatic compensation of bolt preload, which can be widely used in high-reliability bolt connections in fields such as steel structure engineering, prefabricated buildings, bridges, and new energy equipment. Background Technology

[0002] Bolt preload is a crucial parameter for ensuring the load-bearing capacity and ductility of connection joints, especially in shear-driven connections. A suitable and stable preload can significantly improve anti-slip and fatigue resistance. Current design and experimental studies typically recommend that the bolt preload be taken as a certain percentage of the pull-out load-bearing capacity of the connected members, for example, around 70%, to achieve a balance between safety and material utilization.

[0003] However, in engineering construction sites, bolt preload is usually achieved by torque method, angle method or hydraulic tension method. Due to limitations in tool precision, friction coefficient fluctuation and operator skill, the actual preload is often difficult to control precisely. Furthermore, during service, it will gradually decrease due to factors such as embedding, loosening, creep and environmental vibration, resulting in a decline in connection shear resistance and slip reliability.

[0004] In existing technologies, various solutions have been proposed for monitoring bolt preload. For example, some portable or online axial force testing instruments use pressure sensors or strain gauges to test the axial force of high-strength bolts. These are mostly tools used during construction or for periodic testing and are not integrated with the connecting components, making it difficult to achieve real-time monitoring and data recording throughout the entire life cycle. Some research and products directly integrate strain gauges or piezoelectric force gauges into bolts or connecting components to achieve remote or wireless preload monitoring. However, these typically only provide monitoring and alarm functions and lack the ability to automatically compensate for preload reduction.

[0005] On the other hand, high-pressure hydraulic tensioners and hydraulic locking devices are widely used in heavy equipment and large structures, providing precise bolt tension during the installation phase to improve preload control accuracy. However, these devices are mostly external tools or bulky hydraulic locking mechanisms that require an external high-pressure hydraulic source, making them unsuitable for long-term integration into compact junction boxes, and they typically lack the function of automatic adaptive compensation based on preload decay.

[0006] In the gasket field, there are also automatic control gaskets or structures with a certain self-adjusting capability to improve axial stiffness or compensate for fit clearance. However, they mostly focus on sealing or axial clearance adjustment and are not deeply integrated with bolt preload sensing and wireless IoT monitoring systems.

[0007] In summary, current technologies suffer from the following shortcomings: Separation of monitoring and compensation functions: Existing devices primarily focus on preload monitoring or precise tightening during construction, lacking a structural unit that integrates real-time monitoring with in-service automatic compensation, making it difficult to promptly suppress preload attenuation. Insufficient integration and adaptability: Existing bolt sensors or smart bolts require specialized construction, resulting in high costs, inconvenient replacement, and difficulty in placement within confined junction boxes or cable junction boxes. Poor long-term service reliability: Traditional steel junction boxes are heavy, experience severe stress concentration, and are prone to corrosion. Even with conventional gaskets, it is difficult to achieve full-process management of preload, easily leading to fatigue damage and protective failure.

[0008] Therefore, there is an urgent need for an intelligent connection box device that can achieve high-precision real-time monitoring, historical recording, and in-service automatic compensation of preload on standard or conventional bolted connections, while also being lightweight and corrosion-resistant, to improve the long-term shear and slip resistance reliability of bolted connections. This invention addresses these issues by proposing an intelligent preload monitoring and self-adjusting connection box. By integrating a piezoelectric ceramic preload sensing layer, a wireless communication module, and a hydraulic self-adjusting gasket within the connection box, it achieves an organic combination of IoT monitoring and passive hydraulic compensation, structurally and functionally different from the simple assembly of existing technologies. Summary of the Invention

[0009] The main objective of this invention is to provide an intelligent preload monitoring and self-adjusting connector box that achieves the following goals without significantly altering the geometry of traditional bolts and components: high-precision measurement and feedback of bolt preload during construction to assist construction personnel in controlling the preload near the design value; real-time or periodic monitoring of bolt preload during operation to form a preload database covering the entire life cycle; automatic compensation within a certain range of preload by built-in hydraulic self-adjusting shims when the preload significantly decreases due to relaxation, vibration, or temperature changes, without the need for an external hydraulic source or manual intervention; and reduction of the connector box's weight and stress concentration through lightweight, high-strength materials and an inner wall buffer boss design, thereby improving the overall structure's fatigue life and corrosion resistance.

[0010] To achieve the above objectives, the intelligent preload monitoring and self-adjusting connecting box proposed in this invention adopts the following comprehensive technical solution:

[0011] Integrated arrangement of piezoelectric ceramic preload sensing layer: A piezoelectric thin film or piezoelectric ceramic sheet array is directly embedded into the inner wall of the connector box or in a region close to the bolt support surface, forming an integrated sensing layer. This sensing layer generates an electrical charge signal as the contact pressure changes during bolt preload and service. After charge amplification, filtering, and temperature compensation, this signal is converted into a preload value. Compared to methods such as placing strain gauges on the bolt shank or embedding sensors in slots within the bolt, this solution does not alter the standard bolt shape, offers better adaptability, and allows the sensing layer to be integrally formed during the connector box manufacturing stage, improving reliability.

[0012] Passive preload compensation using hydraulic self-adjusting gaskets: A miniature hydraulic chamber, elastic diaphragm, and unidirectional fluid replenishment structure are integrated within a 5-8mm thick gasket. When the bolt preload decreases, leading to a reduction in the average pressure at the contact surface, the pressure within the chamber changes. The elastic diaphragm undergoes a slight deformation under external clamping force, driving fluid flow and causing a slight increase in the axial thickness of the gasket, thereby restoring part of the preload. This process requires no external pump station or control system, relying on the structure's own force-pressure coupling to achieve "self-feedback-self-compensation," offering the advantages of being passive, safe, and requiring minimal maintenance.

[0013] IoT-based data acquisition and historical recording: The connection box integrates signal processing and wireless communication modules, along with a low-power design and energy harvesting unit, to achieve long-term online monitoring. During construction, mobile terminals can be used to read preload values ​​in real time and generate qualification judgments; during operation, data can be uploaded at set intervals to achieve remote preload inspection, historical curve analysis, and linkage with structural health monitoring systems.

[0014] Lightweight and corrosion-resistant design: The connector box body is made of high-strength aluminum alloy or fiber-reinforced composite material, achieving a 30-40% weight reduction and reducing the additional weight and inertia on the main structure; the outer surface is coated with a nano-level anti-corrosion coating to improve resistance to salt spray, humidity and chemical media; the inner wall buffer bosses make the bolt clamping force more evenly distributed within the contact surface area, reducing local stress concentration and improving the fatigue life of the connector box and the connected components.

[0015] Preload control strategy: The initial preload is set to 70% of the component's pull-out bearing capacity. During monitoring, multi-level compensation and early warning thresholds are set based on the preload change trend and environmental load spectrum. When the preload decreases by more than a certain percentage but does not yet endanger safety, hydraulic self-adjusting shims perform one or more small-scale compensations. If the attenuation is too large, a maintenance early warning is issued simultaneously with compensation, enabling manual inspection and structural health monitoring to complement each other.

[0016] By comprehensively applying the above-mentioned technical features, the present invention achieves an integrated design of sensing, compensation and protection at the structural level, which is different from the existing technology that only monitors or provides precise tightening only during the installation stage. While improving the accuracy of bolt preload control, it also significantly improves long-term service reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and do not constitute a limitation of the present invention.

[0018] Figure 1 This is a schematic diagram of the intelligent preload monitoring and self-adjusting connection box of the present invention; Figure 1 The overall structure of the intelligent preload monitoring and self-adjusting connection box of the present invention is illustrated in a typical application scenario. The connection box body (1) is fixed to the connected component by the mounting flange (10); the box cover (2) is fastened to the connection box body (1) by bolts (3) and nuts (4). A hydraulic self-adjusting gasket (5) is provided between the nut (4) and the connection box body (1), and a piezoelectric ceramic preload sensing layer (6) is provided on the inner wall of the connection box near the bolt support surface. The signal processing and wireless communication module (7) and the power supply module (8) are arranged in the side wall of the cavity inside the connection box body (1) or in a dedicated electronic cavity. The inner wall buffer bosses (9) are evenly distributed around the bolt holes, and the outer surface of the connection box is covered with a nano anti-corrosion coating (11).

[0019] Figure 2 This is an exploded view of the connector box of the present invention; Figure 2 The assembly relationship of the main components of the connector box is shown: from bottom to top, they are the connector box body (1), hydraulic self-adjusting gasket (5), nut (4), and box cover (2). Bolts (3) pass through the bolt holes of the box cover (2), hydraulic self-adjusting gasket (5), and connector box body (1), forming a preload transmission path. The piezoelectric ceramic preload sensing layer (6) is uniformly embedded in the inner wall of the connector box body (1) in a ring or multiple pieces. The signal processing and wireless communication module (7) and the power supply module (8) are installed inside the box by screws or adhesive, and the modules are connected by wires or flexible circuit boards.

[0020] Figure 3 This is a cross-sectional view of the hydraulic self-adjusting pad of the present invention. Figure 3This is a cross-sectional view of the hydraulic self-adjusting gasket (5). A ring-shaped or multi-chambered micro-hydraulic cavity (51) is formed within the gasket, filled with liquid or a liquid-gas mixture. One side of the hydraulic cavity is an elastic diaphragm (52), and the other side can be connected to a unidirectional fluid replenishment structure (53) and a micro-energy storage cavity (54) via a flow channel. When the nut (4) applies an axial clamping force to the gasket, the elastic diaphragm (52) deforms, adjusting the pressure within the cavity. When the bolt preload decreases over time, causing a change in the pressure within the cavity, the unidirectional fluid replenishment structure (53) allows the working fluid to flow unidirectionally into the cavity, thereby "raising" the gasket thickness within a certain range and achieving self-adjustment.

[0021] Figure 4 This is an electrical block diagram of the preload monitoring and communication system of the present invention; Figure 4 An electrical block diagram of the preload monitoring and communication system is shown. Multiple piezoelectric ceramic preload sensing layers (6) are connected to a front-end conditioning circuit (71). The output of the conditioning circuit is collected and processed by a microcontroller unit (72) to calculate the bolt preload and its changing trend. The data is stored in a storage unit (73) and transmitted to an external terminal via a wireless communication unit (74). The power module (8) includes a battery unit (81) and an energy harvesting unit (82) to power the entire system.

[0022] Figure 5 This is a schematic diagram illustrating the change of bolt preload over time and automatic compensation according to the present invention. Figure 5 The curve illustrating the change of bolt preload over time is shown schematically, with time on the horizontal axis. The vertical axis represents the preload. During initial tightening, the preload reaches the design value. As service time increases, the preload gradually decreases. Drop to threshold At that moment, the hydraulic self-adjusting shim completed its first minor compensation, restoring the preload to near its normal value. The level; if it continues to decay, when Drop to a lower threshold A second compensation is performed, and a warning signal is issued through the wireless communication unit.

[0023] For ease of understanding, the numbering of the main components in the attached diagram is as follows: 1—Connecting box body; 2—Box cover / end cover; 3—Bolt; 4—Nut; 5—Hydraulic self-adjusting gasket; 6—Piezoelectric ceramic preload sensing layer; 7—Signal processing and wireless communication module; 8—Power module; 9—Inner wall buffer boss; 10—Mounting flange or connecting plate; 11—Nano anti-corrosion coating; 12—Miniature hydraulic chamber; 13—Elastic diaphragm; 14—One-way fluid replenishment structure; 15—Miniature energy storage chamber; 16—Front-end conditioning circuit; 17—Microcontroller unit; 18—Storage unit; 19—Wireless communication unit; 20—Battery unit; 21—Energy harvesting unit. Detailed Implementation

[0024] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the described embodiments are only for explaining the present invention and not for limiting the present invention. Without departing from the essential spirit of the present invention, those skilled in the art can make various modifications and substitutions to the embodiments, and all such modifications and substitutions should fall within the protection scope of the present invention.

[0025] I. Overall Structure and Material Selection

[0026] In a typical embodiment, such as Figures 1-2 As shown, the intelligent preload monitoring and self-adjusting connection box of the present invention includes a connection box body (1), a box cover (2), bolts (3), nuts (4), hydraulic self-adjusting gaskets (5), piezoelectric ceramic preload sensing layer (6), signal processing and wireless communication module (7), power supply module (8), and inner wall buffer bosses (9), etc.

[0027] Connector box body (1)

[0028] Materials: High-strength aluminum alloys (such as 6061-T6, 7075-T6) or carbon fiber reinforced epoxy resin composites are preferred. For applications with high load-bearing requirements and severe environmental corrosion, an aluminum-composite hybrid structure can be used: the outer layer is a composite material, and the inner layer uses aluminum alloy inserts for localized reinforcement areas.

[0029] Structure: The main body of the connecting box (1) is a box or cylindrical structure. Its wall thickness is selected based on mechanical calculations and protection level to ensure that it does not yield or deform excessively under the maximum design bolt preload and external load.

[0030] Surface protection: The outer surface of the enclosure is coated with a nano-level anti-corrosion coating (11), such as containing nano-SiO2. Alternatively, a coating of fluorocarbon-based nanoparticles can be used to improve resistance to salt spray, damp heat, and UV radiation.

[0031] Inner wall buffer boss (9): Several annular or radial bosses are machined or formed around the bolt (3) hole so that the bolt clamping force is transmitted to the box body more evenly through the bosses, improving local stiffness and reducing stress concentration at the inner corner.

[0032] Cover (2) and mounting flange (10): The cover (2) can be connected to the body of the connecting box (1) by bolts or quick-locking structure to form a closed space and protect the internal components. The mounting flange (10) can be welded, screwed or expanded anchored to steel components, concrete embedded parts or other connecting parts to ensure the overall stability and reliability of the connecting box.

[0033] Bolts (3) and nuts (4): The present invention preferably uses standard high-strength bolts, such as 8.8 grade, 10.9 grade or 12.9 grade carbon steel bolts, and stainless steel or other alloy bolts may also be used as needed. Since the preload monitoring is achieved by the piezoelectric ceramic preload sensing layer (6), the bolt itself does not need to be slotted or have a pre-embedded sensor hole, thus avoiding weakening its cross-section and facilitating standardized procurement and maintenance.

[0034] II. Piezoelectric ceramic preload sensing layer (6)

[0035] Structural forms: The piezoelectric ceramic preload sensing layer (6) can take one or a combination of the following forms: Circular piezoelectric ceramic sheet: arranged around the bolt hole, with a thickness of, for example, 0.2-0.5 mm, and connected to the lead wire through a metal electrode; Multi-fan piezoelectric sheet array: evenly distributed in several fan-shaped sheets along the circumference, which is convenient for zone measurement and temperature compensation; Polymer piezoelectric film: such as PVDF piezoelectric film, which has flexible and fatigue-resistant properties and is suitable for laying on the inner wall of curved surfaces.

[0036] Installation method: Embedded: A shallow groove is reserved in the inner wall of the connecting box body (1), the piezoelectric element is embedded in the groove, and fixed with insulating glue or structural glue; Sandwich type: A thin insulating substrate is set between the connecting box body (1) and the hydraulic self-adjusting pad (5), and the piezoelectric element and wires are arranged on it to form an integral sandwich structure.

[0037] Working principle and calibration: When piezoelectric ceramics are subjected to pressure, charges are generated at both ends. The amount of charge and the pressure have an approximately linear relationship within a certain range. The charge is amplified and filtered by the front-end conditioning circuit (71), and the output signal is converted into the corresponding contact pressure. Then, the bolt preload is calculated using geometric relationships. ,For example: ,in This refers to the effective force-bearing area. Before the product leaves the factory, each channel can be calibrated through a standard loading test to obtain a multivariate calibration curve of pressure-voltage-temperature, thereby improving measurement accuracy and achieving a preload measurement error within ±2%.

[0038] III. Hydraulic self-adjusting shims (5)

[0039] Structural design: such as Figure 3 As shown, the hydraulic self-adjusting gasket (5) is generally annular or polygonal, with a central hole for the bolt (3) to pass through. The gasket's interior is formed into a micro hydraulic cavity (51) through precision machining, powder metallurgy, additive manufacturing, or other processes, and the cavity is adjacent to the elastic diaphragm (52). The cavity can be: a single annular continuous cavity; a "petal-shaped" cavity composed of multiple interconnected small cavities; or a multi-cavity structure in which several independent small cavities are interconnected through throttling holes. The elastic diaphragm (52) can be made of metal film, stainless steel corrugated sheet, or high-strength elastomer (such as fluororubber, polyurethane, etc.).

[0040] Working medium and replenishment structure: The micro hydraulic chamber (51) can be filled with low-viscosity liquid, such as synthetic oil or silicone oil, or a liquid-gas mixture medium can be used to achieve compressibility and buffering performance. The one-way replenishment structure (53) can be a micro check valve, a micro-orifice throttle valve, etc., connected to the micro energy storage chamber (54) or the outer peripheral replenishment ring chamber. When the bolt preload is high, the pressure inside the chamber reaches the set initial value; as time goes by, if the preload decreases, the pressure inside the chamber decreases, and the elastic diaphragm moves towards the cavity under the action of the residual clamping force on the outside, pushing the one-way replenishment structure (53) to open, so that the medium in the outer cavity or energy storage chamber flows into the cavity, so that the volume inside the cavity decreases and the pressure increases again; this process is manifested in the axial direction as a slight increase in the thickness of the gasket, that is, passive compensation for the bolt tensile length.

[0041] Compensation range and parameter selection: The preferred gasket thickness is 5-8mm, a compromise between meeting the requirements of micro-hydraulic cavity volume and structural strength while considering installation space. By designing the cavity volume, media compressibility modulus, and diaphragm stiffness, the gasket can undergo reversible axial deformation within the bolt preload range of 5-15%. Let the initial preload be... The initial axial compressive deformation corresponding to the gasket is When the preload decreases due to relaxation At this time, the gasket releases partial deformation and increases the pressure inside the cavity by replenishing fluid, causing additional axial deformation. Converted into additional preload ,achieve: This achieves "range self-recovery" of the preload.

[0042] IV. Signal Processing and Wireless Communication Module (7) and Power Supply Module (8)

[0043] Hardware components: such as Figure 4 As shown, the signal processing and wireless communication module (7) includes: a front-end conditioning circuit (71): a multi-channel charge amplifier, a programmable gain amplifier and a filter, which also has temperature compensation function; a microcontroller unit (MCU) (72): performs A / D conversion, digital filtering and preload calculation, and implements threshold judgment and control logic; a storage unit (73): stores sensor calibration parameters, historical preload data and event logs; and a wireless communication unit (74): supports protocols such as BLE, Wi-Fi, LoRa or NB-IoT to realize short-range and long-range communication.

[0044] The power module (8) includes: a battery unit (81): which can be a lithium-ion battery or a rechargeable lithium battery to ensure a design life of 3-10 years; and an energy harvesting unit (82): which can be selected based on the installation environment, such as piezoelectric energy recovery (using structural vibration), electromagnetic induction (near a cable or magnetic field source) or a small solar cell to achieve extended battery life or maintenance-free operation.

[0045] Software and Data Processing: The MCU periodically samples the sensor signal and performs the following processing: low-pass filtering to remove high-frequency noise; temperature compensation, using a temperature sensor or multi-point calibration coefficients to correct the preload value; and calculation of the current bolt preload. and with the initial value Compare with historical data; if Below a certain threshold If a "compensation trigger event" occurs, it is recorded as one event; if multiple events occur consecutively within a short period of time, or Below the lower threshold At that time, it sends early warning information to the operation and maintenance terminal via the wireless communication unit. In addition, the module can also generate a preload-time curve according to design requirements, such as... Figure 5 As shown, this provides fundamental data for structural health assessment and life prediction.

[0046] V. Usage methods during construction and operation

[0047] Construction phase

[0048] Step 1: Install the connecting box body (1) in the designed position and fix it to the connected component through the mounting flange (10).

[0049] Step 2: Place the hydraulic self-adjusting shim (5) between the nut (4) and the connecting box body (1) to ensure that the center hole of the shim is concentric with the bolt hole.

[0050] Step 3: Insert the bolt (3), pass it through the cover (2), the hydraulic self-adjusting washer (5) and the connecting box body (1) in sequence, and screw on the nut (4).

[0051] Step 4: Tighten the bolts using a torque wrench or hydraulic tensioner. The construction personnel read the preload value monitored by the piezoelectric ceramic preload sensing layer (6) in real time through a mobile terminal, and adjust the tightening torque to make the preload finally stabilize at the design target value. nearby.

[0052] Step 5: After locking is complete, the system records the initial preload. Timestamps and environmental parameters will be used as a benchmark for subsequent comparisons.

[0053] Operational phase

[0054] During operation, the system automatically wakes up and collects preload data according to the set period (such as 1 hour, 1 day or 1 week). If the environmental vibration is severe, the event-driven mode can also be used to increase the sampling frequency when a large vibration or displacement is detected.

[0055] When the preload is monitored Slow decay, but still above the threshold At this time, the system only records data and does not trigger an alarm.

[0056] when At this time, the structural characteristics of the hydraulic self-adjusting gasket (5) enable it to begin to play a compensating role. The axial thickness of the gasket increases in the range of micrometers to tens of micrometers, and the preload thus rises back to a level closer to the required value. The range; the process requires no electronic control and is completed automatically by force-pressure coupling.

[0057] The MCU detected that the preload was lower than Restored to above The process is recorded as a "compensation event," and the event information can be uploaded to the cloud platform for engineers to analyze.

[0058] If, under certain extreme circumstances, the preload continues to decrease... This indicates that the structure is loose or severely damaged. In this case, even if the hydraulic self-adjusting shim has reached its maximum compensation capacity, it may still be difficult to fully restore the design preload. After identifying such a situation, the system will immediately send an alarm message to the maintenance terminal through the wireless communication unit (74), suggesting manual inspection or replacement of the component.

[0059] VI. Optional Embodiments and Variations

[0060] Multi-bolt connection box: In connection nodes where multiple bolts need to work together, multiple sets of bolts (3) and hydraulic self-adjusting gaskets (5) can be arranged in the same connection box. The piezoelectric ceramic preload sensing layer (6) can adopt a multi-channel structure to independently monitor each bolt and realize the uniformity analysis of preload within the group; at the software level, an asymmetric attenuation identification algorithm can be set to give a local warning when the preload of individual bolts drops abnormally.

[0061] Different communication modes: For underground or electromagnetically poor locations, Mesh self-organizing networks or wired-wireless hybrid communication can be used. The connection boxes can form multi-hop transmission to the centralized gateway to reduce the dependence on single base stations.

[0062] Different media and compensation strategies: The working medium in the hydraulic self-adjusting gasket (5) can also be selected based on factors such as ambient temperature and load change frequency. For example, in high-temperature environments, high-temperature resistant silicone oil is selected, and a larger compression space is set in the energy storage chamber (54) to ensure that the compensation performance remains effective at high temperatures. Threshold and The threshold can be adjusted based on the structural importance and safety factor. For example, for critical nodes, the threshold can be set higher to provide compensation and early warning when the attenuation is small.

[0063] Integrated sensor-pad structure: In some embodiments, the piezoelectric ceramic preload sensing layer (6) can be directly integrated onto the hydraulic self-adjusting pad (5), that is, a piezoelectric film and electrodes are laid on the upper or lower surface of the pad, so that the sensing and compensation functions are concentrated in one component. At this time, no additional sensing layer is required on the inner wall of the connecting box, thereby simplifying the structure.

[0064] The above embodiments detail the structure and working principle of an intelligent preload monitoring and self-adjusting connecting box according to the present invention. Those skilled in the art can make various modifications and optimizations to the materials, dimensional parameters, electronic component selection, and software algorithms without departing from the spirit and scope of the present invention; all such modifications and optimizations should be considered to fall within the protection scope of the present invention.

Claims

1. An intelligent pre-tightening force monitoring and self-adjusting connection box, characterized in that, include: The connection box body (1) is used to accommodate components connected by bolts; the bolt connection assembly includes bolts (3) and nuts (4); the piezoelectric ceramic preload sensing layer (6) is disposed on the inner wall of the connection box body (1) and / or on the pressure-bearing surface in contact with the bolt connection assembly, for converting bolt preload into an electrical signal; the signal processing and wireless communication module (7) is electrically connected to the piezoelectric ceramic preload sensing layer (6), for conditioning, storing and wirelessly transmitting the preload signal to an external construction or maintenance terminal; the power supply module (8) provides power to the piezoelectric ceramic preload sensing layer (6). The layer (6) and the signal processing and wireless communication module (7) are powered; the hydraulic self-adjusting gasket (5) is set between the nut (4) and the connecting box body (1) or the connected component. The hydraulic self-adjusting gasket (5) has a micro hydraulic cavity inside, which is used to automatically compensate the bolt axially by the change of pressure in the cavity when the bolt preload decreases. The piezoelectric ceramic preload sensing layer (6) is used to realize real-time monitoring of the bolt preload, and the measurement accuracy is preferably ±2%. The hydraulic self-adjusting gasket (5) is used to realize automatic compensation of the initial preload within the range of 5-15%.

2. The intelligent preload monitoring and self-adjusting connection box according to claim 1, characterized in that, The hydraulic self-adjusting gasket (5) includes: a gasket housing; a ring-shaped or multi-chamber micro hydraulic chamber (51) with a thickness of 5-8 mm disposed inside the gasket housing; an elastic diaphragm (52) separated from the micro hydraulic chamber (51); a one-way fluid replenishment structure (53) and / or a micro energy storage chamber (54) connected to the micro hydraulic chamber (51). When the bolt preload decreases due to relaxation or creep, causing the pressure inside the micro hydraulic chamber (51) to decrease, the elastic diaphragm (52) is compressed under the action of external clamping force, draws liquid from the one-way fluid replenishment structure (53) and increases the pressure inside the chamber, thereby causing a slight increase in the axial height of the gasket to restore the bolt preload.

3. The intelligent preload monitoring and self-adjusting connecting box according to claim 1 or 2, characterized in that, The main body (1) of the connecting box is made of high-strength aluminum alloy and / or fiber-reinforced composite material, which reduces the weight by 30-40% compared with traditional steel connecting boxes. Its outer surface is provided with a nano anti-corrosion coating (11), and the inner wall forms multiple circumferential or ribbed buffer protrusions (9) to expand the contact area of ​​the force and reduce the stress concentration at the inner corner.

4. The intelligent preload monitoring and self-adjusting connecting box according to any one of the preceding claims, characterized in that, The piezoelectric ceramic preload sensing layer (6) is a piezoelectric film or an array of piezoelectric ceramic sheets, which is evenly distributed around the bolt (3) on the inner wall of the connecting box body (1), or is set in a sandwich structure between the hydraulic self-adjusting pad (5) and the connecting box body (1) to simultaneously measure the bolt axial force and the average compressive stress of the contact surface.

5. The intelligent preload monitoring and self-adjusting connecting box according to any one of the preceding claims, characterized in that, The signal processing and wireless communication module (7) includes: a front-end conditioning circuit for amplifying, filtering and compensating the piezoelectric signal by charge; a microcontroller unit for calculating the bolt preload value according to a preset algorithm and generating a preload attenuation curve; a storage unit for recording the initial preload, the amount of compensation each time and the history of preload throughout the entire life cycle; and a wireless communication unit for sending data to the construction terminal and / or cloud platform using Bluetooth, Wi-Fi, LoRa or cellular communication.

6. The intelligent preload monitoring and self-adjusting connecting box according to any one of the preceding claims, characterized in that, The power module (8) includes a primary battery, a rechargeable battery and / or an energy harvesting unit, wherein the energy harvesting unit is selected from at least one of piezoelectric energy recovery, electromagnetic induction coupling or solar cells, so as to realize long-term self-powering or low-maintenance power supply of the connection box.

7. A bolt preload control method based on the intelligent preload monitoring and self-adjusting connecting box according to any one of claims 1-6, characterized in that, The steps include: 1) During the construction phase, the initial preload of bolt (3) is set to 70% of the pull-out bearing capacity of the connected component using a bolt tightening tool, denoted as ,Right now ;2) The bolt preload is monitored in real time by the piezoelectric ceramic preload sensing layer (6), and the data is sent to the construction terminal for real-time display and verification through the signal processing and wireless communication module (7);3) During the operation phase, the bolt preload is collected periodically or continuously to generate a preload decay history. When the preload is detected to be lower than the set threshold, the bolt preload is monitored. At that time, the hydraulic self-adjusting shim (5) is triggered to automatically compensate for pressure; 4) the bolt preload is increased to the specified value through the axial micro-displacement of the micro hydraulic cavity of the hydraulic self-adjusting shim (5). The compensation amount is kept within 5-15% of the initial preload.

8. The bolt preload control method according to claim 7, characterized in that, The preload threshold Set as initial preload The compensation process is divided into multiple levels based on the environmental load spectrum and material creep characteristics, ranging from 50% to 80% of the preload: when the preload is within the range of 50-80%. to During this period, only monitoring data is recorded; when the preload drops to to A small compensation is made when the price is between these points; when the price is below a certain level... Secondary compensation will be performed and maintenance warnings will be issued in a timely manner.

9. The intelligent preload monitoring and self-adjusting connecting box according to any one of the preceding claims, characterized in that, The connection box is suitable for steel structure nodes, prefabricated building connections, bridge auxiliary component installation, cable bracket connections inside wind turbine towers, and other connection occasions that require long-term maintenance of bolt preload.

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