In-situ resistance monitoring method for risk of galling of threaded fasteners

Abstract

This invention discloses an in-situ resistance monitoring method for the risk of threaded fastener seizure, belonging to the field of analysis and measurement control technology. The method includes: assembling an uncoated bolt and nut together to form a threaded fastener, and measuring the resistance of the threaded fastener at this time to obtain the resistance value R0 of the fastener body material; applying a coating to the thread surface of the bolt and nut respectively; repeatedly assembling and disassembling the coated bolt and nut, and measuring the resistance of the assembled threaded fastener after each assembly to obtain the resistance value of the threaded fastener corresponding to different assembly times; comparing the resistance value of the threaded fastener corresponding to different assembly times with the resistance value R0, and determining whether the current threaded fastener has a risk of seizure based on the comparison result. This invention solves the problem of difficulty in in-situ, real-time, rapid, and accurate assessment of thread surface coating failure and seizure risk monitoring in current engineering scenarios.

Description

Technical Field

[0001] This invention relates to the field of analysis and measurement control technology, and in particular to an in-situ resistance monitoring method for the risk of threaded fastener seizing. Background Technology

[0002] Threaded connections are detachable connections and are widely used in engineering. More than 60% of equipment components are connected by threads. However, during actual cyclic assembly and disassembly, due to factors such as improper design, manufacturing processes, and operation, the frictional force between the bolt and nut threads gradually increases, the material temperature rises, and the threads wear or even undergo plastic deformation, leading to metal adhesion and seizing. Seizing failures can cause equipment malfunctions and economic losses, and even affect the safe operation of platforms such as steam turbines and spacecraft.

[0003] To reduce the risk of threaded fastener seizure, engineers have studied the anti-seizure mechanism of threaded friction pairs through experiments and computational simulations, focusing on aspects such as thread structure design and thread stress conditions. They have proposed optimizing the design of coatings, preload, assembly torque, and assembly speed to reduce the risk of seizure. For example, applying a pulsed anodizing layer and a molybdenum disulfide lubricating layer to the surface of titanium alloy bolts can effectively reduce the risk of seizure. Studies using thread torsion experiments and other methods have been conducted to predict the probability and frequency of thread seizure by investigating changes in friction force and friction coefficient during assembly.

[0004] While existing methods and measures can reduce the risk of seizure to some extent, it is impossible to measure seizure control factors such as thread friction, friction coefficient, and tightening torque during actual assembly. Operator habits and alignment deviations can introduce additional seizure risks. Furthermore, thread wear behavior and seizure risks cannot be tracked in real time during actual assembly. Therefore, there is an urgent need for a method to quickly and promptly monitor the seizure risk of threaded fasteners during actual use, which is of significant engineering importance for ensuring the safe operation of equipment. Summary of the Invention

[0005] This invention provides an in-situ resistance monitoring method for the risk of threaded fastener seizing, in order to solve the technical problem of not being able to track thread wear behavior and seizing risk in real time during actual assembly.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for in-situ resistance monitoring of the risk of threaded fastener seizure, wherein the threaded fastener includes a matching bolt and nut, and the method for in-situ resistance monitoring of the risk of threaded fastener seizure includes:

[0008] Uncoated bolts and nuts are assembled together to form a threaded fastener. The resistance of the threaded fastener is measured using a resistance measuring instrument to obtain the resistance value R0 of the threaded fastener body material.

[0009] Apply a pre-defined coating to the thread surface of the bolt and nut respectively;

[0010] After the coating was applied, the bolts and nuts were repeatedly assembled and disassembled. After each assembly, the resistance of the assembled threaded fasteners was measured using a resistance measuring instrument to obtain the resistance value of the threaded fasteners corresponding to different assembly and disassembly times as the bolts and nuts were repeatedly assembled and disassembled.

[0011] The resistance value of the threaded fastener corresponding to different assembly times is compared with the resistance value R0 of the threaded fastener body material, and the risk of seizing of the threaded fastener is determined based on the comparison results.

[0012] Furthermore, the method for measuring the resistance of threaded fasteners using a resistance measuring instrument is as follows:

[0013] After the threaded fastener is correctly assembled, connect one electrode of the resistance measuring instrument to the bolt and the other electrode to the nut, then start the resistance measuring instrument to measure the resistance of the threaded fastener.

[0014] Furthermore, the coating has weaker insulation or conductivity than the body material of the threaded fastener.

[0015] Furthermore, the coated bolts and nuts were repeatedly assembled and disassembled. After each assembly, the resistance of the assembled threaded fasteners was measured using a resistance measuring instrument to obtain the resistance values ​​of the threaded fasteners corresponding to different assembly and disassembly cycles, including:

[0016] Step 1: Before actual assembly, first check the thread structure and coating integrity of the bolt and nut threads, and check for any exposed thread matrix.

[0017] Step 2: After the inspection is passed, screw the bolt into the nut for the first time according to the operating procedure. During this process, the coating on the thread surface of the bolt and nut will be partially peeled off, so that the bolt and nut form a closed circuit. Use a resistance measuring instrument to measure the resistance value R1 of the threaded fastener at this time, and then disassemble the bolt and nut.

[0018] Step 3: Tighten the bolt into the nut again according to the operating procedure, then use a resistance measuring instrument to measure the resistance value of the threaded fastener at this time, and then disassemble the bolt and nut again.

[0019] Step 4: Repeat step 3 to obtain the resistance value of the threaded fastener corresponding to different assembly times.

[0020] Furthermore, the resistance value of threaded fasteners shows a trend of first increasing and then decreasing with the increase of assembly times; when the coating on the thread surface of the bolt and nut is completely removed and the coating debris is completely discharged from the thread gap, the resistance value of the threaded fastener measured at this time is equivalent to the resistance value R0 of the body material.

[0021] Furthermore, the resistance values ​​of the threaded fasteners corresponding to different assembly cycles are compared with the resistance value R0 of the body material. Based on the comparison results, it is determined whether the threaded fasteners are at risk of seizing, including:

[0022] After each execution of step 3 and measurement of the resistance value of the threaded fastener, the measured resistance value of the threaded fastener is compared with the resistance value R0 of the material of the threaded fastener body.

[0023] If, within the preset error tolerance range, the measured resistance value of the threaded fastener is equivalent to the resistance value R0 of the fastener body material and the measured resistance value of the threaded fastener is less than R1, it indicates that the bolt and nut are in direct contact, suggesting that the threaded fastener is about to seize, and warning the engineering operator to replace the threaded fastener.

[0024] This invention utilizes the high sensitivity of resistance to structural changes. Changes in resistance can rapidly reflect alterations in the microstructure. By measuring changes in resistance during cyclic assembly, the failure process of the thread surface coating can be monitored in situ in real time, thereby predicting the risk of seizure. This solves the current problem of difficulty in in-situ, real-time, rapid, and accurate assessment of thread surface coating failure and seizure risk monitoring in engineering scenarios.

[0025] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention include at least the following:

[0026] 1. Existing measures to prevent seizing cannot monitor the failure process of threaded fastener coatings in situ and in real time, thus failing to predict the risk of seizing. This invention utilizes the high sensitivity of electrical resistance to overcome the shortcomings of current anti-seizing measures, achieving in-situ monitoring and avoiding the seizing phenomenon of threaded fasteners, thus solving the safety problems caused by seizing and reducing economic losses.

[0027] 2. The resistance measurement device used in this invention is simple, and even a multimeter commonly used in industry can accurately measure resistance changes, resulting in low cost.

[0028] 3. The resistance is extremely sensitive to structural changes, and the measurement process is fast and convenient, significantly improving efficiency.

[0029] 4. The method of this invention has strong adaptability and is applicable to widely used threaded fasteners with surface coatings, such as stainless steel, alloy steel, high-temperature alloys, and titanium alloys. Furthermore, the method of this invention is not limited by factors such as the shape and size of the thread or nut, thus exhibiting good applicability.

[0030] 5. This invention features a simple process, convenient operation, high accuracy, and good flexibility. It requires minimal professional background from operators and causes no damage to the engineering equipment itself, making it non-destructive and possessing strong engineering application prospects. By monitoring the risk of threaded fastener seizure, it alerts engineering technicians to replace threaded fasteners in a timely manner, reducing the risks of equipment failure and economic losses caused by thread seizure. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the execution flow of the in-situ resistance monitoring method for the risk of threaded fastener seizing provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram showing the failure process and resistance change of the surface coating of the TC4 titanium alloy MJ5 bolt + TC4 support plate self-locking nut during the cyclic assembly process provided in this embodiment of the invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0035] First, it should be noted that in the embodiments of the present invention, the words "exemplarily," "for example," etc., are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the term "exemplarily" is intended to present the concept in a specific manner. Furthermore, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either one or the other.

[0036] Furthermore, in embodiments of the present invention, sometimes a subscript (such as W1) may be mistakenly written as a non-subscript form (such as W1). Without emphasizing the difference, the meaning they express is the same.

[0037] This embodiment provides an in-situ resistance monitoring method for the risk of threaded fastener seizure. The method predicts the risk of seizure by measuring the in-situ resistance. The key technical problem is to obtain the resistance value of the bolt-nut assembly structure in-situ, quickly, and accurately during cyclic assembly. The design principle of this method is as follows:

[0038] To improve the wear resistance of threaded fasteners, wear-resistant coatings are applied to the thread surfaces of bolts and nuts using methods such as pulse anodizing, anodizing, and passivation. Some thread surfaces are also coated with lubricating coatings such as molybdenum disulfide. These coatings are non-conductive or have a resistance much greater than that of the metal substrate. With repeated assembly and disassembly of the threaded fasteners, under the influence of external loads such as friction and preload, the wear-resistant and lubricating coatings gradually detach and accumulate. The detached material is gradually expelled with each tightening and loosening, gradually exposing the metal substrate of the bolt and nut. This change in the microstructure of the bolt-nut assembly inevitably leads to changes in its physical properties. Resistance is a macroscopic reflection of the electronic structure of a material and is extremely sensitive to changes in its microstructure. Therefore, the changes in the microstructure of the bolt-nut assembly during repeated assembly and disassembly will inevitably cause a significant change in its resistance. As the wear-resistant and lubricating coatings gradually detach, accumulate, and are expelled, the resistance initially increases and then decreases. After a certain number of cycles, the coating on the thread surface completely peels off, and the body material comes into direct contact. The resistance value of the bolt-nut assembly is close to that of the body material, indicating that the threaded fastener is about to seize.

[0039] Based on the above theory, the general idea of ​​this method is to utilize the high sensitivity of resistance to structural changes. By using a resistance measuring device, the resistance of the threaded fastener body material and the bolt-nut assembly structure after different cycles of disassembly and assembly (i.e., different number of screwing in and out) can be measured in situ quickly and accurately. This enables in-situ monitoring of the failure process of the threaded fastener surface coating. By comparing the resistance with that of the body material, the risk of threaded fastener seizing can be monitored, thus solving the safety problems caused by seizing and reducing economic losses.

[0040] Specifically, the execution flow of this method is as follows: Figure 1 As shown, it includes the following steps:

[0041] S1. Assemble the uncoated bolts and nuts together to form a threaded fastener, and use a resistance measuring instrument to measure the resistance of the threaded fastener at this time to obtain the resistance value R0 of the threaded fastener body material.

[0042] S2, apply a pre-defined coating to the thread surface of the bolt and nut respectively;

[0043] The coating is an insulating material or its conductivity is much weaker than that of the body material of the threaded fastener.

[0044] S3, after the coating is applied, the bolts and nuts are repeatedly assembled and disassembled, and after each assembly, the resistance of the assembled threaded fastener is measured with a resistance measuring instrument to obtain the resistance value of the threaded fastener corresponding to different assembly times as the bolts and nuts are repeatedly assembled and disassembled.

[0045] The resistance measuring instrument used in the above steps can be any existing resistance measuring device, including but not limited to multimeters commonly used in engineering.

[0046] The measured resistance value refers to the resistance value of the bolt-nut assembly structure after the threaded fasteners are correctly installed according to the operating procedures. Due to the partial peeling of the coating, the bolt and nut assembly structure, which should be insulated, forms a closed circuit. The resistance value is measured by connecting the positive and negative terminals of a resistance measuring device to the bolt and nut respectively.

[0047] Specifically, the implementation process of S3 above is as follows:

[0048] S31. Before actual assembly, first check the thread structure and coating integrity of the bolt and nut threads, and check for any exposed thread matrix.

[0049] S32. After the inspection is passed, the bolt is screwed into the nut for the first time according to the operating procedure. During this process, due to factors such as friction and thread shrinkage, the coating on the thread surface of the bolt and nut will be partially peeled off, causing the bolt and nut to form a closed circuit. The resistance value R1 of the bolt-nut combination structure at this time is measured using a resistance measuring instrument, and the bolt and nut are then disassembled.

[0050] S33, tighten the bolt into the nut again according to the operating procedure, then use a resistance measuring instrument to measure the resistance value of the threaded fastener at this time, and then disassemble the bolt and nut again;

[0051] S34, repeat S33 to obtain the resistance value of the threaded fastener corresponding to different assembly times;

[0052] In the threaded assembly and disassembly process, the coating on the thread surface of the bolt-nut assembly structure continuously peels off and accumulates. The peeling material is also continuously expelled from the thread gap during the unscrewing process, causing the resistance value of the bolt-nut assembly structure to gradually change. The resistance value R of the bolt-nut assembly structure was measured after different assembly cycles. i R irepresents the resistance value during the i-th screwing-in; the resistance value of the bolt-nut combination structure shows a trend of increasing first and then decreasing as the number of cyclic assemblies, that is, the number of screwing-in and screwing-out, increases. After a certain number of cyclic assemblies, when the coating on the surface of the screw thread is completely peeled off and the peeled materials are completely discharged during the screwing-out process, the base materials of the bolt and nut are in direct contact, and the measured resistance value R f decreases sharply. When the measured resistance value is equivalent to R0, that is, R f ≈R0<R i , and R f <R1, it indicates that the threaded fastener is about to seize.

[0053] S4, comparing the resistance values of the threaded fastener corresponding to different assembly times with the resistance value R0 of the base material of the threaded fastener, and determining whether the threaded fastener has a seizing risk according to the comparison result.

[0054] wherein, when R f is close to R0, it indicates that the bolt-nut base materials are in direct contact, which prompts that the threaded fastener is about to seize, and warns engineering operators to replace the threaded fastener connection structure to avoid seizing.

[0055] Hereinafter, the implementation process of the solution of the present invention will be illustrated with specific cases.

[0056] Case 1

[0057] (1) A threaded fastener combination of TC4 titanium alloy MJ5 bolt + TC4 anchor self-locking nut is selected, wherein the bolt surface coating is pulse anodization + molybdenum disulfide, and the surface of the anchor self-locking nut is coated with molybdenum disulfide. When there is no coating, the resistance of the bolt-nut combination structure of this size is less than 0.05Ω.

[0058] (2) Cyclic assembly is performed on a certain aerospace platform, after inspection, the thread structure, coating and the like are complete, and there is no exposed thread pair base body, as shown in Figure 2 , (a) thereof.

[0059] (3) The TC4 titanium alloy bolt is screwed into the TC4 anchor nut according to the procedure. During this process, the coating on the screw thread surface peels off locally to form a closed loop, and at this time the resistance value R1 of the bolt-nut combination structure is 0.05Ω.

[0060] (4) Then further cyclic assembly is performed, the coating on the screw thread surface peels off and accumulates (as shown in Figure 2 , (b) thereof), and the resistance value of the bolt-nut combination structure also gradually changes. The resistance value R of the bolt-nut combination structure after different numbers of cyclic assemblies i is shown in Table 1. It can be seen that with the increase of the number of screwing-in and screwing-out, the resistance shows a trend of increasing first and then decreasing.

[0061] Table 1. Resistance values ​​(R) of the TC4 titanium alloy MJ5 bolt + TC4 support plate self-locking nut combination structure after different assembly cycles. i

[0062]

[0063]

[0064] (5) The resistance value R of the bolt-nut assembly structure was measured after 22 cycles of assembly. f It is 0.05Ω, which is close to the resistance value R0 of the bulk material.

[0065] (6) Further increasing the number of cycles to 24, the resistance of the bolt-nut combination structure drops to 0.03Ω, the threaded fastener seizes up, and the substrate material is completely exposed, such as Figure 2 As shown in (c) in the figure.

[0066] Case 2

[0067] (1) The selected threaded fastener combination is a TB3 titanium alloy M8 bolt + a TC4 dodecagonal self-locking nut. The bolt surface coating is pulse anodized + molybdenum disulfide, and the self-locking nut surface is coated with molybdenum disulfide. When there is no coating, the resistance of the bolt-nut combination structure of this size is less than 0.05Ω.

[0068] (2) During the cyclic assembly on a certain aerospace platform, the screw thread structure and coating were found to be intact, with no exposed threaded substrate.

[0069] (3) Tighten the TB3 titanium alloy bolt into the TC4 dodecagonal self-locking nut according to the procedure. During this process, the coating on the thread surface will be partially peeled off. At this time, the resistance value R1 of the bolt-nut combination structure is 0.05Ω.

[0070] (4) Subsequently, the assembly process was repeated, and the resistance value of the bolt-nut assembly gradually changed. The resistance value R of the bolt-nut assembly after different assembly cycles was... i As shown in Table 2, it can be seen that as the number of screwing in and out increases, the trend is first increased and then decreased.

[0071] Table 2. Resistance values ​​(R) of the TB3 titanium alloy M8 bolt + TC4 dodecagonal self-locking nut combination structure after different assembly cycles. i

[0072]

[0073]

[0074] (5) The resistance value R of the bolt-nut assembly structure was measured after 25 cycles of assembly. f It is 0.05Ω, which is close to the resistance value R0 of the bulk material.

[0075] (6) Further increase the number of cycles to 28 times, the resistance value of the bolt-nut combination structure drops to 0.02Ω, and the threaded fasteners seize up.

[0076] In summary, this embodiment provides an in-situ resistance monitoring method for the risk of threaded fastener seizure. Utilizing the high sensitivity of resistance, it measures the change in the resistance value of the bolt-nut combination during repeated disassembly and assembly of threaded fasteners. This allows for real-time, rapid, in-situ, and accurate monitoring of thread surface coating failure, thereby predicting the risk of seizure. It is applicable to widely used threaded fasteners with surface coatings, such as stainless steel, alloy steel, high-temperature alloys, and titanium alloys, and is unaffected by factors such as thread shape and size.

[0077] Furthermore, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0078] Furthermore, it is understood that in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0079] Finally, it should be noted that the above description represents a preferred embodiment of the present invention. It should be pointed out that although preferred embodiments have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make various improvements and modifications without departing from the principles described herein. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. A method of in-situ resistance monitoring of the risk of galling of a threaded fastener, wherein, The threaded fastener includes a matching bolt and nut, characterized in that the method includes: Uncoated bolts and nuts are assembled together to form a threaded fastener. The resistance of the threaded fastener is measured using a resistance measuring instrument to obtain the resistance value R0 of the threaded fastener body material. Apply a pre-defined coating to the thread surface of the bolt and nut respectively; After the coating was applied, the bolts and nuts were repeatedly assembled and disassembled. After each assembly, the resistance of the assembled threaded fasteners was measured using a resistance measuring instrument to obtain the resistance value of the threaded fasteners corresponding to different assembly and disassembly times as the bolts and nuts were repeatedly assembled and disassembled. The resistance value of the threaded fastener corresponding to different assembly times is compared with the resistance value R0 of the threaded fastener body material, and the risk of seizing of the threaded fastener is determined based on the comparison results. The coated bolts and nuts were repeatedly assembled and disassembled. After each assembly, the resistance of the assembled threaded fasteners was measured using a resistance measuring instrument. This yielded the resistance values ​​of the threaded fasteners corresponding to different assembly and disassembly cycles, including: Step 1: Before actual assembly, first check the thread structure and coating integrity of the bolt and nut threads, and check for any exposed thread matrix. Step 2: After the inspection is passed, screw the bolt into the nut for the first time according to the operating procedure. During this process, the coating on the thread surface of the bolt and nut will be partially peeled off, so that the bolt and nut form a closed circuit. Use a resistance measuring instrument to measure the resistance value R1 of the threaded fastener at this time, and then disassemble the bolt and nut. Step 3: Tighten the bolt into the nut again according to the operating procedure, then use a resistance measuring instrument to measure the resistance value of the threaded fastener at this time, and then disassemble the bolt and nut again. Step 4: Repeat step 3 to obtain the resistance value of the threaded fastener corresponding to different assembly times; The resistance value of threaded fasteners shows a trend of first increasing and then decreasing with the increase of assembly times; when the coating on the thread surface of the bolt and nut is completely removed and the coating debris is completely discharged from the thread gap, the resistance value of the threaded fastener measured at this time is equivalent to the resistance value R0 of the threaded fastener body material. The resistance value of the threaded fastener corresponding to different assembly cycles is compared with the resistance value R0 of the fastener body material. Based on the comparison results, it is determined whether the threaded fastener has a risk of seizing, including: After each execution of step 3 and measurement of the resistance value of the threaded fastener, the measured resistance value of the threaded fastener is compared with the resistance value R0 of the material of the threaded fastener body. If the difference between the measured resistance value of the threaded fastener and the resistance value R0 of the fastener body material is within the preset error allowable range and the measured resistance value of the threaded fastener is less than R1, it indicates that the bolt and nut are in direct contact, suggesting that the threaded fastener is about to seize, and warning the engineering operator to replace the threaded fastener.

2. The method of in-situ resistance monitoring of the risk of galling of a threaded fastener according to claim 1, characterized in that, The method for measuring the resistance of threaded fasteners using a resistance measuring instrument is as follows: After the threaded fastener is correctly assembled, connect one electrode of the resistance measuring instrument to the bolt and the other electrode to the nut, then start the resistance measuring instrument to measure the resistance of the threaded fastener.

3. The in-situ resistance monitoring method for the risk of threaded fastener seizure as described in claim 1, characterized in that, The coating has weaker insulation or conductivity than the body material of the threaded fastener.

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