Intelligent fastener based on force-light response

Abstract

The invention discloses an intelligent fastener based on force-light response. The intelligent fastener comprises a bolt, a coating and a detector. Wherein the coating comprises a first light guide layer, a light emitting layer, a second light guide layer, a reflecting layer and a protective layer; the first light guide layer is arranged on the lower surface of the end of the bolt; the light-emitting layer is arranged on the lower surface of the first light guide layer; the second light guide layer is arranged on the lower surface of the light-emitting layer; the reflecting layer is arranged on the lower surface of the second light guide layer; the protective layer is arranged on the lower surface of the reflecting layer; and the detector can receive optical signals which are transmitted by the first light guide layer and the second light guide layer and are emitted by the light emitting layer. The method is simple and convenient to prepare and low in cost, is not limited by the structural form of the bolt end face, and has wide application value.

Description

Technical Field

[0001] The invention belongs to the technical field of fasteners, and in particular relates to an intelligent fastener based on force-light response. Background Art

[0002] The effective measurement of bolt preload is of great significance to the improvement of aerospace equipment assembly performance. In terms of preload measurement, relevant research has been carried out at home and abroad. At present, relatively effective and direct methods are mainly based on ultrasonic guided waves, ultrasonic body waves, and electromechanical impedance detection technology.

[0003] (1) Detection technology based on ultrasonic guided waves:

[0004] When ultrasonic waves pass through solid materials, they cause elastic stress waves in the material, which propagate along the surface or inside of the material to form ultrasonic guided waves. Ultrasonic guided waves have a long propagation distance in the structure and low energy attenuation. They can detect internal and surface defects of mechanical structures and achieve comprehensive inspection.

[0005] Ultrasonic guided waves are divided into low-frequency ultrasonic guided waves and high-frequency ultrasonic guided waves according to the excitation frequency. Low-frequency ultrasonic guided waves are suitable for detecting damage in large-area structures, such as interface debonding damage, but the detection accuracy is low. High-frequency thick-walled ultrasonic guided waves are highly sensitive to micro-damage on the inner surface of medium and long distances, and the modal conversion is not obvious. They are suitable for detecting micro-damage in the thickness direction of multi-layer connection structures.

[0006] Ultrasonic guided wave detection is suitable for simple geometric structures. Under complex boundary conditions, modal conversion and wave interference effects are prone to occur, requiring more advanced signal analysis algorithms. Minor damage has little effect on wave propagation, and environmental compensation is difficult.

[0007] (2) Detection technology based on ultrasonic body waves

[0008] Ultrasonic body waves are a test method based on the acoustoelastic theory. The essence of the acoustoelastic theory is that the propagation speed of ultrasound will be changed by the bolt stress. The bolt preload measurement methods based on ultrasonic body waves mainly include: the resonant frequency shift method and the time-of-flight method. The resonant frequency shift method is a test method based on the acoustoelastic effect. Different bolt preloads will cause the resonant frequency of the bolt system to change. The time-of-flight method evaluates the bolt preload by measuring the time it takes for ultrasound to propagate in the material.

[0009] Ultrasonic body wave detection technology is highly sensitive, quantitative, light and portable, and is suitable for real-time detection of the connection status of aerospace equipment. However, the end faces of the products that need to receive signals are all flat, so the requirements for the structural form are high, and most of the time, the main structure of the bolt needs to be changed. Therefore, the structural adaptability of this detection method is poor.

[0010] (3) Detection technology based on electromechanical impedance

[0011] Electromechanical impedance method (EMI) uses the electromechanical coupling characteristics of piezoelectric materials to associate electrical impedance with mechanical impedance. Changes in the connection contact state affect the mechanical impedance, which in turn reflects changes in electrical impedance characteristics. As a local damage detection method, the electromechanical impedance method needs to consider the sensor size and the selection of the excitation signal frequency when applied. It is mainly used for mechanical connections, mainly for bolt loosening detection, and cannot obtain the preload of the bolt. Summary of the invention

[0012] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and provide an intelligent fastener based on force-light response, which is easy to prepare, low in cost, not limited to the structural form of the bolt end face, and has wide application value.

[0013] The objective of the present invention is achieved through the following technical solutions: an intelligent fastener based on force-light response, comprising: a bolt, a coating and a detector; wherein the coating comprises a first photoconductive layer, a luminescent layer, a second photoconductive layer, a reflective layer and a protective layer; the first photoconductive layer is arranged on the lower surface of the end of the bolt; the luminescent layer is arranged on the lower surface of the first photoconductive layer; the second photoconductive layer is arranged on the lower surface of the luminescent layer; the reflective layer is arranged on the lower surface of the second photoconductive layer; the protective layer is arranged on the lower surface of the reflective layer; the detector can receive the light signal emitted by the luminescent layer transmitted by the first photoconductive layer and the second photoconductive layer.

[0014] In the above-mentioned smart fastener based on force-light response, during the tightening process of the smart fastener based on force-light response, after the head of the bolt contacts the connected part, the coating begins to be compressed, and the light-emitting layer in the coating emits a light signal, which is transmitted to the detector through the first photoconductive layer and the second photoconductive layer; the detector obtains the preload force corresponding to the light signal through the light signal and a preset light intensity and preload force correspondence table.

[0015] In the above-mentioned smart fastener based on force-light response, the first photoconductive layer includes a coating and a diluent; wherein the coating includes at least one of epoxy resin, polytetrafluoroethylene and / or polyurethane; and the diluent includes at least one of ethanol, acetone and / or deionized water.

[0016] In the above-mentioned intelligent fastener based on force-light response, the weight ratio of the coating to the diluent is 1:1 to 3:1.

[0017] In the above-mentioned smart fastener based on force-light response, the second photoconductive layer includes a second coating and a second diluent; wherein the second coating includes at least one of epoxy resin, polytetrafluoroethylene and / or polyurethane; and the second diluent includes at least one of ethanol, acetone and / or deionized water.

[0018] In the above-mentioned intelligent fastener based on force-light response, the weight ratio of the second coating to the second diluent is 1:1 to 3:1.

[0019] In the above-mentioned intelligent fastener based on force-light response, the light-emitting layer includes powder and a carrier; wherein the weight ratio of the powder to the carrier is 1:1 to 3:1.

[0020] In the above-mentioned smart fastener based on force-light response, the powder includes at least two of ZnS:Mn orange powder, CaZnOS:Mn orange powder, CaZnOS:Tb green powder, CaZnOS:Ho yellow powder, CaZnOS:Nd near-infrared powder, MgF2:Mn orange powder, MgF2:Yb blue powder, and LiNbO3:Pr red powder; and the carrier is a resin coating.

[0021] In the above-mentioned intelligent fastener based on force-light response, the reflective layer is a silver coating or an aluminum coating.

[0022] In the above-mentioned intelligent fastener based on force-light response, the protective layer is a diamond-like carbon coating, a silver coating, a molybdenum disulfide coating or an aluminum coating.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The intelligent fastener product based on force-light response of the present invention is easy to prepare, low in cost, is not restricted to the structural form of the bolt end face, and has wide application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0026] Figure 1 Schematic diagram of the structure of a smart fastener based on force-light response provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] Figure 1 Schematic diagram of the structure of the intelligent fastener based on force-light response provided by an embodiment of the present invention. Figure 1 As shown, the intelligent fastener based on force-light response includes: a bolt 1, a coating and a detector; wherein the coating includes a first photoconductive layer 2, a luminescent layer 3, a second photoconductive layer 4, a reflective layer 5 and a protective layer 6; the first photoconductive layer 2 is placed on the lower surface of the end of the bolt 1; the luminescent layer 3 is placed on the lower surface of the first photoconductive layer 2; the second photoconductive layer 4 is placed on the lower surface of the luminescent layer 3; the reflective layer 5 is placed on the lower surface of the second photoconductive layer 4; the protective layer 6 is placed on the lower surface of the reflective layer 5; the detector can receive the light signal emitted by the luminescent layer 3 transmitted by the first photoconductive layer 2 and the second photoconductive layer 4.

[0029] In the tightening process of the intelligent fastener based on force-light response, after the head of the bolt 1 contacts the connected part, the coating begins to be compressed, and the luminous layer 3 in the coating emits a light signal, which is transmitted to the detector through the first photoconductive layer 2 and the second photoconductive layer 4; the detector obtains the preload force corresponding to the light signal through the light signal and the preset light intensity and preload force correspondence table. It should be understood that the preset light intensity and preload force correspondence table is stored in the detector in advance.

[0030] The first light-guiding layer 2 includes a coating and a diluent, wherein the coating includes at least one of epoxy resin, polytetrafluoroethylene and polyurethane, and the diluent includes at least one of ethanol, acetone and deionized water, and the weight ratio of the coating to the diluent is 1:1 to 3:1.

[0031] The second light-guiding layer 4 includes a second coating and a second diluent, wherein the second coating includes at least one of epoxy resin, polytetrafluoroethylene and polyurethane, and the second diluent includes at least one of ethanol, acetone and deionized water. The weight ratio of the second coating to the second diluent is 1:1 to 3:1.

[0032] The light-emitting layer 3 includes a powder and a carrier, wherein the weight ratio of the powder to the carrier is 1:1 to 3:1.

[0033] The powder includes at least two of ZnS:Mn orange powder, CaZnOS:Mn orange powder, CaZnOS:Tb green powder, CaZnOS:Ho yellow powder, CaZnOS:Nd near-infrared powder, MgF2:Mn orange powder, MgF2:Yb blue powder, and LiNbO3:Pr red powder; and the carrier is a resin coating.

[0034] The reflective layer is a silver coating or an aluminum coating, and the protective layer is a diamond-like carbon coating, a silver coating, a molybdenum disulfide coating or an aluminum coating.

[0035] This embodiment is an intelligent fastener product based on the force-light response principle, which obtains the preload force of the bolt through the change of the luminescent color in the force-light conversion material, and mainly includes the use of force-luminescent materials and the application of intelligent coatings.

[0036] Mechanoluminescent materials are a new type of material that emits light when subjected to external forces, and their light intensity and color change linearly with stress. The principle of luminescence is that when subjected to external loads, the crystal lattice of the mechanoluminescent material undergoes significant deformation along the stress direction, which causes the coordination environment of the luminescent center to change, thereby causing the radiation transition energy level of the doping center to change, resulting in a shift in the luminescent spectrum.

[0037] In order to ensure the accuracy and stability of the detection, the present invention uses a two-component force-light conversion material with different luminous colors, calibrates the load through the ratio of the relative intensity of the luminous peak, rationally designs the force-light conversion material components, and performs multiple rounds of optimization in simulation tests. In actual use, by collecting the wavelength of light emitted by the force-light conversion material between the bolt head and the connected parts during the tightening of the fastener, the specific value of the instantaneous preload can be dynamically given according to the calibration results.

[0038] The smart coating includes a photoconductive layer, a luminous layer, a reflective coating, and a spray protective layer. During the tightening process of the fastener, after the bolt head contacts the connected part, the coating begins to be compressed, and the luminous layer in the coating emits a light signal, which is transmitted to the edge of the coating through the photoconductive layer. Therefore, when the coating is subjected to force, a luminous signal will be generated on the outside of the coating edge, which can be collected by a light detector.

[0039] As the preload increases, the load on the coating increases, the stress increases, and the color of the light signal emitted by the edge of the coating changes accordingly. Based on the corresponding relationship between the collected dual-band intensity and the preload, the current preload value can be obtained in real time.

[0040] Bolt surface treatment: Pre-treat the lower surface of the bolt head. Use water-based media and environmentally friendly solvents for wet chemical treatment. Use jet cleaning, spraying, immersion cleaning, ultrasonic cleaning, solvent-based high-pressure cleaning and other cleaning technologies to clean the oil, dust and other dirt on the lower surface of the bolt head. Use alcohol or other solvents to clean the surface to ensure that there is no oil or impurities on the surface.

[0041] Spray the first light-conducting layer: Use epoxy resin, polytetrafluoroethylene or transparent polyurethane coating, and select appropriate diluents according to the type of coating, such as ethanol, acetone, and deionized water. The choice of spraying equipment is based on the spraying requirements and the type of coating. Usually, spray guns, pressure tanks, air compressors, etc. are used. After spraying, dry and solidify. During the drying process, control the humidity and temperature to ensure that the coating is fully solidified. The thickness of the cured coating is controlled at about 50-100 μm.

[0042] Preparation of luminescent layer: Select two or more powders with different luminescent colors (such as ZnS:Mn (first orange), CaZnOS:Mn (second orange), CaZnOS:Tb (green), CaZnOS:Ho (yellow), CaZnOS:Nd (near infrared), MgF2:Mn (third orange), MgF2:Yb (blue), LiNbO3:Pr (red), etc.), sieve (200-800 mesh) and mix them evenly as composite fillers. Adjust the powder ratio according to the response characteristics of the selected material to stress and the preload range of the fastener, so that it has a clear color response to the change of preload within the designed preload range.

[0043] The following two methods are used to compound the powder and the carrier material: one is to evenly mix the powder filler and the carrier material and then directly form a mechanoluminescent layer on the surface of the photoconductive layer by powder spraying; the other is to spray or brush a coating of a specific thickness on the surface of the fastener photoconductive layer, and use electrostatic adsorption or throwing methods to make the uncured coating surface adsorb the composite mechanoluminescent powder filler, and then heat or stand to cure. Repeat the above method 1-5 times to ensure that a mechanoluminescent layer of appropriate thickness (50-100 μm) is formed.

[0044] Spraying the second light-conducting layer: Using the method of spraying the first light-conducting layer, spray epoxy resin, polytetrafluoroethylene or transparent polyurethane coating, the thickness is also 50-100 μm.

[0045] Preparation of reflective coating: Activate the surface of the second optical guide layer, perform chemical silver plating or aluminum coating by immersion or spraying, or prepare silver or aluminum coating by electroplating, and control the thickness to be 30-200nm.

[0046] Spraying protective layer: Spraying protective layer on the surface of reflective coating according to the usage scenario, such as wear-resistant diamond-like carbon coating, conductive corrosion-resistant silver coating, lubricating molybdenum disulfide coating, corrosion-resistant and lubricating aluminum coating, etc. The thickness of the protective layer is controlled at 20-50 μm.

[0047] Load calibration: The load is calibrated by the ratio of the relative intensity of the luminescence peaks. The color change range of the force-light conversion material corresponds to the preload design value.

[0048] Preload monitoring: As the preload increases, the load on the coating increases, and the color of the light signal emitted from the edge of the coating changes. The current preload value is obtained in real time based on the corresponding relationship between the collected dual-band intensity ratio and the preload.

[0049] This embodiment is an intelligent fastener product that obtains the preload force of the bolt by changing the color of the light emitted by the force-light conversion material. The force-light conversion material is used to achieve quantitative changes in the light signal with the preload force. The force-light conversion material is matched with two components and different light-emitting colors. The load is calibrated by the ratio of the relative intensity of the light-emitting peaks. The color change range of the force-light conversion material corresponds to the preload design value one by one. The preload force monitoring is mainly achieved by an intelligent coating containing force-light conversion materials. The intelligent coating includes a photoconductive layer, a luminous layer, a reflective coating, a spray protective layer, etc. During the tightening process of the fastener, the intelligent coating is compressed after the bolt head contacts the connected part. The luminous layer emits light signals of different colors according to the size of the force load. The light signal is transmitted to the edge of the coating through the photoconductive layer. The light detector collects the light signal at the edge of the coating and obtains the current preload force according to the calibration.

[0050] The intelligent fastener product based on force-light response in this embodiment is easy to prepare, low-cost, not limited to the structural form of the bolt end face, and has wide application value.

[0051] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A smart fastener based on force-light response, characterized in that include: A bolt (1), a coating and a detector; wherein: The coating comprises a first light-guiding layer (2), a light-emitting layer (3), a second light-guiding layer (4), a reflecting layer (5) and a protective layer (6); The first light-guiding layer (2) is placed on the lower surface of the end of the bolt (1); The light-emitting layer (3) is disposed on the lower surface of the first light-guiding layer (2); The second light-guiding layer (4) is disposed on the lower surface of the light-emitting layer (3); The reflective layer (5) is disposed on the lower surface of the second light-guiding layer (4); The protective layer (6) is disposed on the lower surface of the reflective layer (5); The detector is capable of receiving the optical signal emitted by the light-emitting layer (3) and transmitted by the first optical guide layer (2) and the second optical guide layer (4).

2. The intelligent fastener based on force-light response according to claim 1, characterized in that: During the tightening process of the intelligent fastener based on force-light response, after the head of the bolt (1) contacts the connected part, the coating begins to be compressed, and the luminescent layer (3) in the coating emits a light signal, which is transmitted to the detector through the first light-guiding layer (2) and the second light-guiding layer (4); The detector obtains the preload force corresponding to the light signal through the light signal and a preset light intensity and preload force correspondence table.

3. The intelligent fastener based on force-light response according to claim 1, characterized in that: The first light-guiding layer (2) comprises a coating and a diluent; wherein: The coating comprises at least one of epoxy resin, polytetrafluoroethylene and / or polyurethane; The diluent includes at least one of ethanol, acetone and deionized water.

4. The intelligent fastener based on force-light response according to claim 3, characterized in that: The weight ratio of the coating to the diluent is 1:1 to 3:

1.

5. The intelligent fastener based on force-light response according to claim 1, characterized in that: The second light-guiding layer (4) comprises a second coating and a second diluent; wherein, The second coating comprises at least one of epoxy resin, polytetrafluoroethylene and / or polyurethane; The second diluent includes at least one of ethanol, acetone and deionized water.

6. The intelligent fastener based on force-light response according to claim 5, characterized in that: The weight ratio of the second coating material to the second diluent is 1:1 to 3:

1.

7. The intelligent fastener based on force-light response according to claim 1, characterized in that: The light-emitting layer (3) comprises a powder and a carrier; wherein the weight ratio of the powder to the carrier is 1:1 to 3:

1.

8. The intelligent fastener based on force-light response according to claim 7, characterized in that: The powder includes at least two of ZnS:Mn orange powder, CaZnOS:Mn orange powder, CaZnOS:Tb green powder, CaZnOS:Ho yellow powder, CaZnOS:Nd near-infrared powder, MgF2:Mn orange powder, MgF2:Yb blue powder, and LiNbO3:Pr red powder; The carrier is a resin coating.

9. The intelligent fastener based on force-light response according to claim 1, characterized in that: The reflective layer is a silver-plated layer or an aluminum-plated layer.

10. The intelligent fastener based on force-light response according to claim 1, characterized in that: The protective layer is a diamond-like carbon coating, a silver coating, a molybdenum disulfide coating or an aluminum coating.

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