An apparatus for assembling smart fasteners, an automatic assembling method thereof, and a mechanoluminescent coating

Abstract

This application discloses a device for assembling smart fasteners, its automatic assembly method, and a mechanoluminescent coating. When the fastener is subjected to force and deforms, the mechanoluminescent coating generates a light signal corresponding to the strain state. The assembly execution module applies an assembly load to a nut that matches the fastener connected to the adapter via a controllable torque motor and performs the assembly action according to the instructions of the control unit. A photoelectric sensing unit and a data processing module are used to collect the light signal of the smart fastener during assembly in real time. The data processing module analyzes the signal and sends a stop command to the assembly execution module to terminate the assembly process, achieving closed-loop control of the preload. This application maintains the portability of the device, eliminates the need for large, fixed testing equipment, and eliminates the need for operators to repeatedly manually determine the stop time based on the displayed results. It is better suited for on-site assembly and batch assembly scenarios in industrial production lines, thereby improving assembly efficiency, preload consistency, and ease of operation.

Description

Technical Field

[0001] This application belongs to the field of fastener assembly technology, specifically relating to a device for assembling smart fasteners, its automatic assembly method, and a mechanoluminescent coating. Background Technology

[0002] Sensing technology, as a crucial support for modern industrial development, is widely used in various fields such as intelligent manufacturing, automotive electronics, healthcare, wearable devices, aerospace, and monitoring of major engineering structures. As industrial equipment iterates and upgrades towards intelligence, automation, and precision, sensing technology is simultaneously developing rapidly towards intelligence, miniaturization, integration, and multifunctionality. This places increasingly stringent demands on sensors' real-time response capabilities, detection accuracy, structural adaptability, and environmental stability.

[0003] Bolts and other fasteners are the most basic and commonly used connecting elements in engineering structures and mechanical equipment, widely used in critical scenarios such as aerospace, rail transportation, automobile manufacturing, machine tool equipment, bridge engineering, and large equipment assembly. The reliability of bolted connections directly depends on their preload: insufficient preload can easily lead to loosening of the connection, vibration failure, and even damage to the overall structure; excessive preload may cause bolt yielding and shortened fatigue life. Therefore, accurate and real-time detection of bolt preload is of vital practical significance for ensuring the safety of engineering structures and equipment, improving assembly quality, and realizing intelligent operation and maintenance.

[0004] Currently, existing methods for detecting bolt preload mainly include the torque method, direct measurement method, ultrasonic non-destructive testing method, and computer vision recognition method. However, each method has significant limitations: the torque method is greatly affected by the friction coefficient, lubrication state, and assembly conditions, making it difficult to guarantee detection accuracy; the direct measurement method usually requires the installation of strain gauges, pressure sensors, and other components, resulting in complex wiring, high cost, and poor structural adaptability, making it difficult to adapt to complex assembly scenarios; the ultrasonic non-destructive testing method is easily affected by material properties, temperature changes, coupling state, and operating conditions, requiring high levels of expertise from both the testing equipment and the operators; while the computer vision recognition method has the advantage of non-contact detection, it is easily affected by lighting, obstruction, surface condition, and installation environment, and it is difficult to accurately quantify the bolt preload. Existing bolt preload detection technologies each have their own insurmountable limitations, failing to fully meet the actual needs of real-time, accurate, intuitive, and low-cost detection of fastener preload in automated assembly scenarios. Summary of the Invention

[0005] In view of the above problems, this application provides an intelligent fastener device and corresponding automatic assembly detection method that is easy to integrate into automated assembly processes, batch assembly, can provide real-time feedback on bolt tightness status, and can effectively improve detection reliability and adaptability.

[0006] In a first aspect, this application provides an apparatus for assembling smart fasteners, comprising: The smart fastener includes a fastener and a mechanoluminescent coating formed on the surface of the fastener head. The mechanoluminescent coating is excited and generates a light signal corresponding to the strain state when the fastener is deformed under stress, and a nut that matches the fastener. The assembly execution module includes a housing, a controllable torque motor, a light-shielding fastener, an adapter that matches and connects to a nut, and a control unit. The controllable torque motor and the control unit are located inside the housing, and the adapter is connected to the controllable torque motor. The light-shielding fastener is connected to a fastener to fix the head of the fastener. The assembly execution module applies an assembly load to the nut connected to the adapter through the controllable torque motor, and starts, runs, and stops the assembly process according to the instructions of the control unit. The system includes a photoelectric sensing unit and a data processing module. The photoelectric sensing unit is located inside the light-shielding fixture, opposite the mechanoluminescent coating on the bolt head. The data processing module is located inside the housing and connected to the photoelectric sensing unit. The photoelectric sensing unit is used to collect the light signal generated by the mechanoluminescent coating during the assembly process in real time, and analyzes it through the data processing module. It then sends a stop command to the assembly execution module to terminate the assembly process, thereby achieving closed-loop control of the preload force.

[0007] In some embodiments, the mechanoluminescent coating is composed of SrAl2O4:Eu,Zr inorganic mechanoluminescent powder and an epoxy resin matrix.

[0008] In some embodiments, the mass ratio of the SrAl2O4:Eu,Zr inorganic mechanoluminescent powder to the epoxy resin matrix is ​​1:1.

[0009] In some embodiments, the mechanoluminescent coating is molded and cured onto the upper surface of the head of the device, and the thickness of the mechanoluminescent coating is 0.8-1.0 mm.

[0010] In some embodiments, the photoelectric sensing unit includes a photoelectric sensor and a transimpedance amplifier, and the data processing module includes an analog-to-digital converter and a main controller. The photoelectric sensor, transimpedance amplifier, analog-to-digital converter, and main controller are connected by electrical connection lines to establish signal links. The photoelectric sensor is coupled to the analog-to-digital converter via the transimpedance amplifier, and the main controller is electrically connected to both the analog-to-digital converter and the control unit.

[0011] In some embodiments, the main controller generates control commands based on the comparison between the real-time light intensity value and the target light intensity threshold, and controls the intelligent assembly module to stop outputting assembly force.

[0012] In some embodiments, the assembly execution module is a portable electric assembly tool.

[0013] Secondly, this application provides an automatic assembly method for smart fasteners, based on the aforementioned apparatus for assembling smart fasteners, comprising the following steps: S1. Connect the matching nut of the fastener to the adapter, connect the light-shielding fastener to the fastener, and fix the head of the fastener; apply assembly load to the fastener using the assembly execution module; S2. During the fastening process, the force-induced light-emitting coating on the surface of the fastener generates a light signal when subjected to force; S3. The photoelectric sensing unit and data processing module collect optical signals and obtain real-time light intensity values; S4. The data processing module compares the real-time light intensity value with the preset target light intensity threshold; S5. When the real-time light intensity value reaches the target light intensity threshold, a stop command is sent to the assembly execution module to complete the assembly.

[0014] Thirdly, this application provides a mechanoluminescent coating, characterized in that it is composed of SrAl2O4:Eu,Zr inorganic mechanoluminescent powder, epoxy resin matrix, and curing agent.

[0015] The beneficial effects of this application are: Compared to existing handheld open-loop devices that only perform "detection-display" functions, this invention not only uses force-induced light emission signals for preload detection and numerical display, but also introduces an intelligent assembly module and control feedback path into the assembly structure, allowing the force-induced light emission signals to directly participate in the assembly control process. Specifically, the force-induced light emission signals are collected in real time through a photoelectric sensing and data processing module, and the light intensity value is compared with a preset threshold. When the light intensity reaches the threshold corresponding to the target preload, the system sends a stop command to the intelligent assembly module, thereby realizing a closed-loop automatic assembly process of "detection-judgment-control-stop". Thus, this invention expands the force-induced light emission signal from preload detection information to assembly control signals, realizing closed-loop control of bolt automatic assembly based on feedback of the actual stress state of the fastener.

[0016] While maintaining the portability of the device, this invention further enhances the ability to perform precise batch assembly of ordinary flat bolts. This invention does not rely on large, fixed testing equipment, nor does it require operators to repeatedly manually determine when to stop the machine based on displayed results. It is better suited for on-site assembly and batch assembly scenarios on industrial production lines, thereby improving assembly efficiency, preload consistency, and ease of operation.

[0017] This invention employs a mechanoluminescent coating with a simpler fabrication process and applies it to the upper surface of the bolt head. This structural improvement allows the photoelectric sensor to be directly positioned above the smart fastener for optical signal acquisition, reducing the difficulty of sensor installation and system integration. It also avoids obstruction, scattering, or mechanical interference to the optical signal during sleeve rotation, thereby improving the stability and reliability of optical signal acquisition.

[0018] This invention directly establishes a linear correspondence between monochromatic light intensity and preload, allowing the bolt preload status to be determined simply by detecting a single luminous intensity. This method eliminates the need for multi-wavelength spectral dispersion, dual-color signal ratio calculations, or complex spectral demodulation, reducing spectral cross-interference and signal processing errors, improving computational efficiency and system response speed. It is more suitable for high-frequency real-time judgment in automated assembly processes and for precise industrial batch assembly.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the structure of a device for assembling smart fasteners according to this application; Figure 2 This is a schematic diagram of the structure of an intelligent fastener for assembling an intelligent fastener according to the present application; Figure 3 The diagram shows a comparison of the elastic modulus and simulated strain of the smart fastener of this application and the fastener of Comparative Example 1. Figure 4 A comparison diagram of the mechanoluminescence performance of the smart fastener of this application and the fastener of Comparative Example 1 is shown. Figure 5 Comparison of the mechanoluminescence properties of fasteners in Example 1 and fasteners with other coatings; Figure 6 This diagram illustrates the relationship between the preload and the luminous signal in an automatic assembly method for an intelligent fastener according to this application.

[0021] The reference numerals in the detailed embodiments are as follows: 1. Intelligent fastener; 2. Photoelectric sensor; 3. Signal amplification circuit; 4. Housing; 5. Analog-to-digital conversion circuit; 6. Main controller; 7. Power supply and protection circuit; 8. Relay; 9. Controllable torque motor; 10. Rotating head; 11. Nut; 12. Light-shielding collection housing. Detailed Implementation

[0022] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0024] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0025] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0027] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0028] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0029] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0030] According to some embodiments of this application, refer to Figure 1 , 2 A portable, automated assembly smart fastener device based on force-luminescence is disclosed, which mainly includes: a smart fastener 1, an assembly execution module, a photoelectric sensing unit, and a data processing module. The device can sense the pre-tightening state of the smart fastener 1 (metal bolt) in real time during bolt assembly and automatically control the start and stop of assembly based on the force-luminescence signal, thereby achieving portable, automated, and precise assembly of metal bolts.

[0031] The smart fastener 1 includes a fastener (metal bolt) and a force-luminescent coating disposed on the upper surface of the head of the metal bolt, as shown in the attached figure. Figure 2 As shown, the mechanoluminescent coating is formed by the composite curing of SrAl2O4:Eu,Zr mechanoluminescent powder and an epoxy resin matrix, and is tightly adhered to the upper surface of the metal bolt head. The thickness of the mechanoluminescent coating is 0.8-1.0 mm, preferably 0.8 mm. When the metal bolt is subjected to axial preload during assembly, the bolt head undergoes a slight deformation. Under this deformation, the mechanoluminescent coating generates a light signal, and the intensity of the light signal has a linear correlation with the magnitude of the metal bolt preload. Therefore, the target preload of the metal bolt can be determined by detecting the intensity of the light signal.

[0032] If the coating thickness is too thin (<<0.8 mm), the luminous signal intensity is insufficient, the total amount of effective force-induced luminescent powder within the coating is reduced, and the number of photons generated when excited by the same bolt head strain is insufficient, resulting in a weak light signal, deteriorated signal-to-noise ratio, and difficulty in reliable acquisition by photoelectric sensors; strain transmission distortion, although the interface strain transmission between the thin coating and the metal bolt head is direct, the coating itself weakens the "amplification" effect on micro-strain (the thickness of the coating, as a strain transmission medium, affects the uniformity of stress distribution), which may lead to deviation of the linear relationship between light intensity and preload; coating uniformity is difficult to guarantee, and excessively thin coatings are prone to uneven thickness, local defects, or bubbles during mold forming, resulting in inconsistent luminous response, increased dispersion in the preload detection accuracy of the same batch of bolts, and reduced wear resistance and lifespan; insufficient mechanical protective layer of the coating, during assembly process, repeated contact with the light-shielding fastener or environmental friction, it is easy to wear off and peel off, affecting long-term reliability.

[0033] Excessive thickness (>1.0 mm) leads to decreased strain transfer efficiency. When the coating is too thick, the strain in the bolt head metal is attenuated during the transfer to the coating surface due to stress relaxation within the coating. The actual surface strain is less than the true strain in the bolt head, causing the optical signal to inaccurately reflect the preload. Self-absorption / scattering of the optical signal occurs because the photon propagation path is longer within the thick coating, increasing the probability of self-absorption (reabsorption by other luminescent particles) and multiple scattering, reducing the effective emitted light intensity and disrupting the linear relationship between light intensity and preload. Stress concentration within the coating is also a concern. The large curing shrinkage stress of a thick coating, combined with the significant difference in thermal expansion coefficients between the thick coating and the bolt head, results in substantial interfacial stress, which can easily lead to microcracks or interfacial peeling under long-term use, reducing durability. Furthermore, increased bolt head thickness may cause mechanical interference with the nut countersunk hole, the surface of the connector, or the light-shielding fastener, affecting normal assembly and versatility. Finally, response delays occur because the elastic deformation of a thick coating requires time to transfer, causing a lag in the mechanoluminescence response relative to changes in preload, affecting the timeliness of real-time closed-loop control.

[0034] The assembly execution module is used to drive the intelligent fastener 1 to tighten and achieve automatic and controllable assembly. The assembly execution module includes a controllable torque motor 9, an adapter and housing 4 for tightening bolts, a relay 8, and a power supply and protection circuit 7. One end of the adapter is connected to the controllable torque motor 9, and the other end engages with a nut that matches the metal bolt. A light-shielding retainer is connected to the fastener 1 to fix its head. The light-shielding retainer can be a wrench that matches the fastener 1 and engages with a light-shielding acquisition housing, or an internal hex wrench with a light-shielding acquisition housing. A photoelectric sensing unit is installed inside the light-shielding acquisition housing; this allows the controllable torque motor 9 to drive the nut to rotate via the adapter and complete the assembly. The relay 8 is located in the motor control circuit and is used to connect or disconnect the working state of the controllable torque motor 9 according to control commands issued by the photoelectric sensing unit and the data processing module.

[0035] The photoelectric sensing unit and data processing module collect the light signal generated by the mechanoluminescent coating and determine the preload state of the metal fastener based on the intensity of the light signal. The photoelectric sensing unit consists of a photoelectric sensor 2, a signal amplification circuit 3, and a light-shielding collection housing 12. The signal amplification circuit 3 is a transimpedance amplifier, and both the photoelectric sensor 2 and the signal amplification circuit 3 are installed inside the light-shielding collection housing 12. The light-shielding collection housing 12 is fixedly positioned above the head of the metal fastener and is separate from the rotary adapter used to engage the fastener and transmit tightening torque, with no movement interference between the two. During operation, the photoelectric sensor 2 receives the light signal generated by the force applied to the coating and converts it into an electrical signal. The signal amplification circuit 3 converts and amplifies the weak photocurrent output by the sensor into a voltage signal. The signal amplification circuit 3 is connected to the analog-to-digital converter circuit 5 through a fixedly laid signal line, and the analog-to-digital converter circuit 5 converts the analog voltage signal into a digital signal. The main controller 6 calculates the light signal intensity and compares the calculation result with a preset preload threshold to complete the preload state determination.

[0036] During assembly, the assembly execution module drives the adapter to tighten the matching nut of the metal bolt. As the assembly process proceeds, the head of the metal bolt deforms under the axial preload, and the SrAl2O4:Eu,Zr composite mechanoluminescent coating on the upper surface of the metal bolt head generates a light signal. The photoelectric sensor 2 receives this light signal and outputs an electrical signal, which is transmitted to the main controller 6 after passing through the signal amplification circuit 3 and the analog-to-digital conversion circuit 5. The main controller 6 compares the real-time light intensity value with a preset threshold. When the light intensity reaches the threshold corresponding to the target preload, the main controller 6 sends a stop command to the relay 8. The relay 8 disconnects the motor control circuit, causing the assembly execution module to stop tightening, thereby realizing automatic and precise assembly based on mechanoluminescence.

[0037] The main controller 6 can also be set with a safety threshold. When the intensity of the acquired light signal exceeds the safety threshold, the main controller 6 determines that the bolt is at risk of overload and immediately sends a protective shutdown command to the assembly execution module to avoid damage to the bolt or the connected parts. The photoelectric sensing unit and data processing module can also be optionally equipped with a wireless communication unit to upload the real-time light intensity, preload judgment results, and shutdown status to an external terminal, but the wireless communication unit is not a necessary component for the automatic assembly control of this invention.

[0038] The device's workflow is as follows: The assembly execution module drives the nut to rotate via an adapter. The SrAl2O4:Eu, Zr and epoxy resin composite mechanoluminescent coating on the head of the metal bolt generates a light signal under stress. The photoelectric sensing unit and data processing module collect and process the light signal. When the light signal intensity reaches the preset target threshold, the data processing module sends a stop command to the intelligent assembly module, causing the motor to stop working, thereby completing the precise assembly of the metal bolt.

[0039] The smart fasteners in this application are obtained using the following method: The raw materials were accurately weighed according to the molar ratio of Al2O3, SrCO3, Eu2O3, and ZrO2 of 1:0.98:0.01:0.04 and added to a mortar. After being mixed evenly, the mixture was sintered at 1400℃ for 6 hours to synthesize SrAl2O4:Eu,Zr mechanoluminescent bulk material. The obtained mechanoluminescent bulk material was ground and sieved to obtain inorganic mechanoluminescent powder with uniform particle size distribution of SrAl2O4:Eu,Zr. SrAl2O4:Eu,Zr inorganic mechanoluminescent powder and epoxy resin matrix with added polyetheramine D230 curing agent are mixed at a mass ratio of 1:1 to obtain composite sensing slurry.

[0040] Excessive luminescent powder ratio (>1:1) leads to decreased coating mechanical strength. Excessive inorganic powder weakens the continuous network structure of the epoxy resin matrix, resulting in increased coating brittleness and reduced impact resistance, making it prone to cracking or peeling under repeated stress on the bolt head. Interface adhesion failure occurs because excessive powder particles prevent the epoxy resin from fully coating all particles, reducing the interfacial bonding force between the coating and the metal bolt head and affecting strain transfer efficiency. Optical signal saturation / nonlinearity occurs because excessively high powder concentration may cause photons to undergo self-absorption or scattering loss within the coating, thereby reducing effective light output and disrupting the linear relationship between light intensity and preload. The coating process is difficult because excessively high slurry viscosity results in poor flowability during mold forming, making it difficult to uniformly cover the curved surface of the bolt head and easily causing bubbles or uneven thickness.

[0041] If the proportion of luminescent powder is too low (<<1:1), the luminescence intensity will be insufficient, the number of effective luminescent centers will be reduced, resulting in a weak light signal. The photoelectric sensor will have difficulty in reliably acquiring the light, and the signal-to-noise ratio will deteriorate. The detection sensitivity will decrease, the strain-luminescence response caused by changes in preload will be weaker, and the system's ability to distinguish small differences in preload will decrease, affecting assembly accuracy. The error in determining the preload threshold will increase, the light intensity signal will approach the background noise level, and the digital signal after analog-to-digital conversion will fluctuate greatly, which will easily lead to misjudgment (early shutdown or over-tightening). The elastic modulus of the coating will deviate from the optimal value, and the high proportion of the substrate will make the coating too "soft" overall, reducing the strain transmission efficiency.

[0042] Preferably, the epoxy resin precursor and polyetheramine D230 curing agent are weighed and mixed uniformly at a mass ratio of 3:1 to obtain a modified epoxy resin matrix; then the inorganic mechanoluminescent powder obtained in step S2 is uniformly dispersed in the matrix liquid, and after thorough stirring to remove bubbles, a composite sensing slurry is obtained. A molding die adapted to the shape of the metal bolt head is set on the upper surface of the bolt head. The composite sensing slurry is injected into the molding die to uniformly cover the upper surface of the metal bolt head. Subsequently, it is heated and cured at 60-80 ℃ for 2-4 h to fully crosslink and cure the epoxy resin precursor and polyetheramine D230, forming a mechanoluminescent composite coating that is firmly bonded to the metal bolt head, thus obtaining the intelligent fastener preload sensor.

[0043] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, instead of using polyetheramine D230 curing agent, triethylenetetramine curing agent was used to cure the epoxy resin. Other conditions were the same as in Example 1.

[0044] The elastic modulus and bolt head strain were tested separately. The test results are as follows: Figure 3 The composite coating described in this application has a higher elastic modulus than the comparative example, and according to the simulation strain results of the embodiments and the comparative example, the embodiments can produce a more efficient strain transfer capability.

[0045] Further comparative experiments were designed to examine the mechanoluminescence properties of different composite coatings. The SrAl2O4:Eu,Zr / epoxy resin-D230 composite coating described in this application was used as an example, while other mechanoluminescent composite coatings, such as SrAl2O4:Eu,Zr / ordinary epoxy resin coating, SrAl2O4:Eu,Zr / silicone coating, SrAl2O4:Eu,Zr / UV-curable adhesive coating, SrAl2O4:Eu,Zr / polyesteramide coating, and SrAl2O4:Eu,Zr / polydimethylsiloxane (PDMS) coating, were used as comparative examples. The mechanoluminescence characteristics of these coatings were observed under the same preload conditions. Under the same preload conditions, the SrAl2O4:Eu,Zr / ordinary epoxy resin coating exhibited the strongest mechanoluminescence response. We then compared the mechanoluminescence of the SrAl2O4:Eu,Zr / epoxy resin-D230 composite coating and the SrAl2O4:Eu,Zr / ordinary epoxy resin coating described in this application. The test results showed that the mechanoluminescence response of the embodiment was significantly stronger than that of the SrAl2O4:Eu,Zr / ordinary epoxy resin coating. According to... Figure 3-5 This application demonstrates that by increasing the elastic modulus of the coating and the adhesion to the metal interface, the transmission efficiency of strain from the bolt head to the composite force-luminescent coating is enhanced, thereby improving the light signal response intensity and the preload detection sensitivity.

[0046] Compared to existing technologies that rely on manual experience, torque wrenches, or large assembly equipment, this invention integrates a force-illuminating intelligent fastener, an intelligent assembly module, and a photoelectric sensing and data processing module into one unit, enabling precise quantitative assembly of metal bolts. This device eliminates the need for complex circuits or large testing equipment, offering advantages such as simple structure, small size, portability, real-time response, high assembly accuracy, and suitability for on-site operations and batch assembly.

[0047] In this application, during the installation and testing of bolt fasteners, the intensity of force-induced emission has a linear correlation with the magnitude of the assembly force. (Refer to...) Figure 6 As shown. Specifically, when the intelligent assembly device assembles the intelligent fastener, the intelligent fastener is subjected to assembly force, and its bolt head generates strain, thereby causing the mechanoluminescent coating on the surface of the bolt head to generate a light signal. The light signal is converted and amplified by a photoelectric sensor and a data acquisition module, and then digitally acquired and processed by an analog-to-digital converter and a main controller. It is then transmitted to a computer via a Bluetooth communication module. The operator can observe the signal change curve in real time during the assembly process on the computer, thereby identifying the stress state of the intelligent fastener during the assembly process and judging the specific assembly force of the bolt fastener based on the intensity of the mechanoluminescence.

[0048] By fitting the luminescence intensity data collected under different preload conditions, a quantitative relationship between luminescence intensity I and axial preload F can be established. In a preferred embodiment, the luminescence intensity I and axial preload F exhibit a linear positive correlation, which can be expressed as: I = a + b * F Where I represents the collected force-induced emission intensity, F represents the axial preload applied to the smart fastener, a represents the initial background signal, and b represents the sensitivity coefficient. Based on the above linear relationship, the magnitude of the bolt's preload can be inferred from the detected emission intensity, thus enabling non-destructive quantitative detection of the fastener's preload state.

[0049] This application provides a portable device for automatically assembling intelligent fasteners based on force-luminescence. It can convert the mechanical stress state during bolt assembly into detectable light signals, and further convert these into electrical and digital signals for processing, enabling real-time detection, quantitative judgment, and automatic shutdown control of the bolt fastener assembly process. This device has advantages such as simple structure, intuitive response, strong real-time detection, easy integration, and suitability for automated batch assembly scenarios.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A device for assembling smart fasteners, characterized in that, include: The smart fastener includes a fastener and a mechanoluminescent coating formed on the surface of the fastener head. The mechanoluminescent coating is excited and generates a light signal corresponding to the strain state when the fastener is deformed under stress, and a nut that matches the fastener. The assembly execution module includes a housing, a controllable torque motor, a light-shielding fastener, an adapter that matches and connects to a nut, and a control unit. The controllable torque motor and the control unit are located inside the housing, and the adapter is connected to the controllable torque motor. The light-shielding fastener is connected to a fastener to fix the head of the fastener. The assembly execution module applies an assembly load to the nut connected to the adapter through the controllable torque motor, and starts, runs, and stops the assembly process according to the instructions of the control unit. The system includes a photoelectric sensing unit and a data processing module. The photoelectric sensing unit is located inside the light-shielding fixture, opposite the mechanoluminescent coating on the bolt head. The data processing module is located inside the housing and connected to the photoelectric sensing unit. The photoelectric sensing unit is used to collect the light signal generated by the mechanoluminescent coating during the assembly process in real time, and analyzes it through the data processing module. It then sends a stop command to the assembly execution module to terminate the assembly process, thereby achieving closed-loop control of the preload force.

2. The device for assembling intelligent fasteners as described in claim 1, characterized in that, The mechanoluminescent coating is composed of SrAl2O4:Eu,Zr inorganic mechanoluminescent powder, epoxy resin matrix, and curing agent.

3. The device for assembling intelligent fasteners as described in claim 2, characterized in that, The mass ratio of the SrAl2O4:Eu,Zr inorganic mechanoluminescent powder to the epoxy resin matrix is ​​1:

1.

4. A device for assembling smart fasteners as described in claim 1 or 2, characterized in that, The mechanoluminescent coating is formed and cured on the upper surface of the head of the metal bolt by a mold, and the thickness of the mechanoluminescent coating is 0.8-1.0 mm.

5. The device for assembling intelligent fasteners as described in claim 1, characterized in that, The photoelectric sensing unit includes a photoelectric sensor and a transimpedance amplifier, and the data processing module includes an analog-to-digital converter and a main controller. The photoelectric sensor, the transimpedance amplifier, the analog-to-digital converter and the main controller are connected by electrical connection lines to establish a signal link. The photoelectric sensor is coupled to the analog-to-digital converter via the transimpedance amplifier, and the main controller is electrically connected to the analog-to-digital converter and the control unit respectively.

6. The apparatus for assembling intelligent fasteners as described in claim 5, characterized in that, The main controller generates control commands based on the comparison between the real-time light intensity value and the target light intensity threshold, and controls the intelligent assembly module to stop outputting assembly force.

7. The device for assembling intelligent fasteners as described in claim 1, characterized in that, The assembly execution module is a portable electric assembly tool.

8. An automatic assembly method for intelligent fasteners, characterized in that, The apparatus according to any one of claims 1-7 includes the following steps: S1. Connect the matching nut of the fastener to the adapter, connect the light-shielding fastener to the fastener, and fix the head of the fastener; apply assembly load to the fastener using the assembly execution module; S2. During the fastening process, the force-induced light-emitting coating on the surface of the fastener generates a light signal when subjected to force; S3. The photoelectric sensing unit and data processing module collect optical signals and obtain real-time light intensity values; S4. The data processing module compares the real-time light intensity value with the preset target light intensity threshold; S5. When the real-time light intensity value reaches the target light intensity threshold, a stop command is sent to the assembly execution module to complete the assembly.

9. A mechanoluminescent coating, characterized in that, The mechanoluminescent coating in the apparatus of any one of claims 1-3 or the method of claim 8 is composed of SrAl2O4:Eu,Zr inorganic mechanoluminescent powder, epoxy resin matrix, and curing agent.

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