Method and system for determining friction coefficient of interface of threaded connection pair

Abstract

The invention discloses a method and a system for determining a friction coefficient of an interface of a threaded connection pair. The method comprises the following steps: preparing a threaded connection pair sample piece with set clamping force; a transverse load is applied to the threaded connection pair sample piece with the set clamping force until the threaded connection pair sample piece fails; obtaining a transverse load borne by the threaded connection pair sample piece when the threaded connection pair sample piece fails, and taking the transverse load as the anti-sliding capability of the threaded connection pair sample piece; the friction coefficient of the interface is determined according to the clamping force and the anti-sliding capacity of the threaded connection pair sample piece, and accurate determination of the friction coefficient of the interface in the threaded connection pair is achieved.

Description

Technical Field

[0001] This invention relates to the field of fastener testing technology, and in particular to a method and system for determining the friction coefficient of the interface of a threaded connection pair. Background Technology

[0002] Most automotive threaded connections are designed to generate axial clamping force through preloaded torque. The connected parts, subjected to this axial clamping force, produce static friction. This static friction balances the lateral external load of the threaded connection, ensuring its overall stability and reliability. The lateral external load refers to the load perpendicular to the bolt's axial clamping force. Therefore, accurately determining the friction coefficient between the connected parts in a threaded connection, i.e., the friction coefficient at the interface, is crucial for accurately determining the anti-slip capability of automotive threaded connections.

[0003] The coefficient of friction between current connecting parts is determined by consulting relevant standards or by measuring with a coefficient of friction meter.

[0004] However, the friction coefficient between connecting parts recorded in the relevant standards has a large range, which makes it impossible to accurately determine the friction coefficient between connecting parts. When measuring the friction coefficient using a friction coefficient meter, it only relies on the self-weight between the connecting parts and does not take into account the influence of the clamping force in the threaded connection pair, resulting in the determined friction coefficient not being applicable to the threaded connection pair. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a method and system for determining the interface friction coefficient of threaded connection pairs, thereby achieving accurate determination of the interface friction coefficient in threaded connection pairs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a method for determining the interface friction coefficient of threaded connection pairs is proposed, including: Prepare a threaded connection assembly sample with a set clamping force; A transverse load is applied to a threaded connection sample with a set clamping force until the threaded connection sample fails. The transverse load borne by the threaded connection sample when it fails is used as the anti-slip capability of the threaded connection sample. The friction coefficient of the interface is determined based on the clamping force and anti-slip capability of the threaded connection sample.

[0007] Furthermore, multiple threaded connection pairs with different clamping forces were prepared; Determine the anti-slip capability of each threaded connection pair sample with different clamping forces; Based on the clamping force and anti-slip capability of each threaded connection pair sample with different clamping forces, multiple friction coefficients of the interface are determined. The final friction coefficient of the interface is obtained by averaging the multiple friction coefficients of the interface.

[0008] Furthermore, multiple threaded connection pairs with the same clamping force were prepared; Determine the anti-slip capability of each threaded connection pair sample with the same clamping force; The minimum value among all threaded connection pairs with the same clamping force is selected as the anti-slip capability of the threaded connection pair sample with that clamping force.

[0009] Furthermore, the multiple lateral loads and lateral displacements borne by the threaded connection sample during the process of applying lateral loads to the threaded connection sample until the threaded connection sample fails were obtained. Based on the multiple lateral loads and lateral displacements borne by the threaded connection sample, determine the force-displacement characteristic curve of the threaded connection sample. The lateral load at which the slope of the force-displacement characteristic curve decreases to a set value is used as the anti-slip capability of the threaded connection pair sample.

[0010] Furthermore, based on the clamping force and anti-slip capability of the threaded connection sample, the friction coefficient of the interface is calculated and determined using the friction calculation formula.

[0011] Furthermore, threaded connection pairs with interfaces of multiple materials were prepared; Determine the anti-slip capability of threaded connection pairs at the interface of each material; The coefficient of friction of each material interface is determined based on the anti-slip capability and clamping force of the threaded connection sample at the interface of each material.

[0012] Secondly, a system for determining the interface friction coefficient of threaded connection pairs is proposed, including: a threaded connection pair sample, a clamping force application tool, a testing machine, a data acquisition unit, and a data analysis and processing unit; A clamping force application tool is used to apply torque to the threaded connection assembly sample, so that the threaded connection assembly sample has a set clamping force; A testing machine is used to apply a transverse load to a threaded connection assembly sample with a set clamping force until the threaded connection assembly sample fails. The data acquisition unit is used to acquire the clamping force of the threaded connection sample and the lateral load it bears when the threaded connection sample fails. The data analysis and processing unit is used to take the lateral load borne by the threaded connection sample when it fails as the anti-slip capability of the threaded connection sample; and to determine the friction coefficient of the interface based on the clamping force and anti-slip capability of the threaded connection sample.

[0013] Furthermore, the threaded connection assembly includes a bolt, a nut, a first connector, a second connector, and a third connector; the first connector, the second connector, and the third connector are arranged sequentially; the bolt passes through the first connector, the second connector, and the third connector and then connects with the nut; the interface refers to the contact surface between the first connector and the second connector, and the contact surface between the second connector and the third connector.

[0014] Furthermore, the bottom surfaces of the first and second connectors are flat; the shape of the second connector is adapted to the shape of the load loading head of the testing machine.

[0015] Furthermore, the second connector is located within the load range of the testing machine.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention proposes a method and system for determining the interface friction coefficient of a threaded connection pair. The method involves preparing a threaded connection pair sample with a set clamping force; applying a lateral load to the sample until it fails; obtaining the lateral load borne by the failed sample as its anti-slip capability; and determining the interface friction coefficient based on the clamping force and anti-slip capability of the sample. This achieves accurate determination of the interface friction coefficient in a threaded connection pair. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0018] Figure 1 This is a flowchart of a method for determining the interface friction coefficient of a threaded connection pair proposed in this invention; Figure 2 This is a schematic diagram of the force-displacement characteristic curve proposed in this invention; Figure 3 This is a schematic diagram of the threaded connection pair sample structure proposed in this invention; Figure 4 The following are outline drawings of the first and third connectors proposed in this invention; Figure 5 This is a schematic diagram of the second connector proposed in this invention.

[0019] The components are: 1. First connecting piece, 2. Second connecting piece, 3. Third connecting piece, 4. Bolt, 5. Nut. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, 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.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0024] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0025] First, the application scenarios and application systems of the method for determining the interface friction coefficient of a threaded connection pair proposed in this embodiment will be introduced.

[0026] The application scenario of the method for determining the friction coefficient of the interface of a threaded connection pair proposed in this embodiment is to accurately measure the friction coefficient of the interface in an automotive threaded connection pair.

[0027] The coefficient of friction between current connecting parts is determined by consulting relevant standards or by measuring with a coefficient of friction meter.

[0028] However, the friction coefficient between connecting parts recorded in the relevant standards has a large range, which makes it impossible to accurately determine the friction coefficient between connecting parts. When measuring the friction coefficient using a friction coefficient meter, it only relies on the self-weight between the connecting parts and does not take into account the influence of the clamping force in the threaded connection pair, resulting in the determined friction coefficient not being applicable to the threaded connection pair.

[0029] The method for determining the interface friction coefficient of threaded connection pairs proposed in this embodiment is intended to solve the technical problem that related technologies cannot accurately determine the interface friction coefficient of automotive threaded connection pairs.

[0030] The application system for determining the interface friction coefficient of a threaded connection pair proposed in this embodiment includes a threaded connection pair sample, a clamping force application tool, a testing machine, a data acquisition unit, and a data analysis and processing unit. A clamping force application tool is used to apply torque to the threaded connection assembly sample, so that the threaded connection assembly sample has a set clamping force; A testing machine is used to apply a transverse load to a threaded connection assembly sample with a set clamping force until the threaded connection assembly sample fails. The data acquisition unit is used to acquire the clamping force of the threaded connection sample and the lateral load it bears when the threaded connection sample fails. The data analysis and processing unit is used to take the lateral load borne by the threaded connection sample when it fails as the anti-slip capability of the threaded connection sample; and to determine the friction coefficient of the interface based on the clamping force and anti-slip capability of the threaded connection sample.

[0031] Based on the application scenarios and application systems of the method for determining the interface friction coefficient of a threaded connection pair proposed in this embodiment, the method for determining the interface friction coefficient of a threaded connection pair proposed in this embodiment will be described in detail.

[0032] like Figure 1 As shown in this embodiment, a method for determining the interface friction coefficient of a threaded connection pair includes: Prepare a threaded connection assembly sample with a set clamping force; A transverse load is applied to a threaded connection sample with a set clamping force until the threaded connection sample fails. The transverse load borne by the threaded connection sample when it fails is used as the anti-slip capability of the threaded connection sample. The friction coefficient of the interface is determined based on the clamping force and anti-slip capability of the threaded connection sample.

[0033] like Figure 3 As shown, the threaded connection assembly includes a bolt 4, a nut 5, a first connector 1, a second connector 2, and a third connector 3; the first connector 1, the second connector 2, and the third connector 3 are arranged sequentially; the bolt 4 passes through the first connector 1, the second connector 2, and the third connector 3 and then connects to the nut 5, clamping the first connector 1, the second connector 2, and the third connector 3 together with the bolt 4 and the nut 5; the interface refers to the contact surface between the first connector 1 and the second connector 2, and the contact surface between the second connector 2 and the third connector 3.

[0034] In this embodiment, a universal testing machine is used to apply a transverse load to the threaded connection sample. In order to ensure the stability of the threaded connection sample on the testing machine during the test, the bottom surfaces of the first connector 1 and the third connector 3 are set as planes. In order to ensure the stability of the load applied to the threaded connection sample by the testing machine, the testing machine applies the load to the second connector 2 and limits the shape of the second connector 2 to be compatible with the shape of the load loading head of the testing machine.

[0035] In some embodiments, the first connector 1 and the third connector 3 are selected as follows: Figure 4 The rectangle shown in the image, the second connector is selected as follows: Figure 5 The cylindrical shape shown.

[0036] The first connector 1, the second connector 2 and the third connector 3 are provided with channels for the bolt 4 to pass through, and one end of the bolt 4 passes through the channel and is connected to the nut 5.

[0037] Preferably, the bolts are M12*1.25-10.9 grade hexagonal flange bolts, with both ends ground flat, roughness not greater than Ra1.6 and parallelism not greater than 0.2; the nuts are selected to be compatible with the bolts, and the nut performance grade is 10.

[0038] The first connector 1 and the third connector 3 are rectangular parts with a diameter of 35mm*35mm*5mm; the second connector 2 is a cylindrical part with a diameter of 35mm*50mm, where 35mm is the end diameter of the cylindrical part and 50mm is the height of the cylindrical part; a through hole with an inner diameter of 14.2mm is provided at the center of the first connector 1, the second connector 2 and the third connector 3 as a channel for the bolt 4 to pass through.

[0039] Universal testing machine according to Figure 3 The transverse load F is applied to the second connector of the threaded connection sample, and the load loading head is moved at a moving speed of 1 mm / min. The transverse load F is the maximum load that the test machine can output.

[0040] A force measuring device is installed on the threaded connection sample to obtain the lateral load borne by the sample. The overall accuracy of the force measuring device is ±1% of the measured value, and the displacement reading accuracy of the load loading head is ±0.01 mm. The experiment should be conducted at +23℃±5℃.

[0041] In some embodiments, multiple lateral loads and lateral displacements borne by the threaded connection pair sample during the process of applying a lateral load to the threaded connection pair sample until the threaded connection pair sample fails are obtained. Based on the multiple lateral loads and lateral displacements borne by the threaded connection sample, determine the force-displacement characteristic curve of the threaded connection sample. The lateral load at which the slope of the force-displacement characteristic curve decreases to a set value is used as the anti-slip capability of the threaded connection pair sample.

[0042] The obtained force-displacement characteristic curve is as follows: Figure 2 As shown, the force-displacement characteristic curve is initially a horizontal straight line, followed by an inclined straight line with a consistent slope. After this inclined straight line, there is a curve with a decreasing slope. When this curve is reached, it indicates that the threaded connection assembly has failed.

[0043] Depend on Figure 2 It can be seen that when the slope of the force-displacement characteristic curve drops to 50% of the slope of the inclined straight line, it indicates that the threaded connection sample has failed.

[0044] In some embodiments, a clamping force application tool applies torque to the threaded connection assembly sample, thereby giving the threaded connection assembly sample a set clamping force.

[0045] By setting an ultrasonic measuring device in the threaded connection sub-sample, ultrasonic signals are transmitted and received. The acoustic time difference between ultrasonic transmission and reception is calculated, and then the clamping force of the threaded connection sub-sample is determined based on the time difference.

[0046] The ultrasonic measuring device can use a 4*4cm-5Hz piezoelectric ceramic sheet, which is then attached to the end of the bolt.

[0047] When applying torque to the threaded connection sample using a clamping force application tool, the torque is applied at a speed of 10 r / min at the bolt head, while an ultrasonic clamping force test is performed at the bolt tail. After the bolt is stretched, the ultrasonic transit time changes. The clamping force of the threaded connection sample can be obtained by comparing this transit time with the bolt calibration curve. The bolt calibration curve refers to the relationship curve between the ultrasonic transit time and the transverse clamping force of the threaded connection sample. This curve can be obtained in advance by measuring various clamping forces of the threaded connection sample and the ultrasonic transit time corresponding to each clamping force, and fitting the clamping force and its corresponding ultrasonic transit time.

[0048] For example, obtain the time difference data of ultrasound corresponding to 0.5Fp±10%, 0.75Fp±10%, Fp±10%, etc.

[0049] In some embodiments, multiple threaded connection pairs with different clamping forces are prepared; Determine the anti-slip capability of each threaded connection pair sample with different clamping forces; Based on the clamping force and anti-slip capability of each threaded connection pair sample with different clamping forces, multiple friction coefficients of the interface are determined. The final friction coefficient of the interface is obtained by averaging the multiple friction coefficients of the interface.

[0050] In this process, a transverse load is applied to each threaded connection sample using a testing machine until the threaded connection sample fails. The transverse load that the threaded connection sample bears when it fails is obtained as the anti-slip capability of the threaded connection sample.

[0051] In some embodiments, the friction coefficient of the interface is calculated and determined using the friction calculation formula based on the clamping force and anti-slip capability of the threaded connection sample.

[0052] The formula for calculating friction is as follows: f=z*F*u*m In the formula, z is the number of bolts in the connecting pair sample; f is the lateral external load in the connecting pair sample, i.e., the anti-slip capability; u is the friction coefficient of the interface in the connecting pair; and m is the number of interfaces in the connecting pair that transmit lateral loads.

[0053] By determining the anti-slip capability of threaded connection pairs with different clamping forces, multiple friction coefficients of the interface are determined. Then, the average of these multiple friction coefficients is taken to obtain the final friction coefficient of the interface, ensuring the accuracy of the determination of the interface friction coefficient.

[0054] In some embodiments, multiple threaded connection pairs with the same clamping force are prepared; Determine the anti-slip capability of each threaded connection pair sample with the same clamping force; The minimum value among all threaded connection pairs with the same clamping force is selected as the anti-slip capability of the threaded connection pair sample with that clamping force.

[0055] By conducting lateral loading tests on multiple threaded connection pairs with the same clamping force, the anti-slip capability of each threaded connection pair sample with the same clamping force is determined. Then, the minimum value among all anti-slip capabilities is selected as the anti-slip capability of the threaded connection pair sample with that clamping force, ensuring the accuracy of determining the anti-slip capability of the threaded connection pair sample with each clamping force, and further ensuring the accuracy of determining the friction coefficient of the threaded connection pair interface.

[0056] In some embodiments, threaded connection pairs with interfaces of multiple materials are prepared; Determine the anti-slip capability of threaded connection pairs at the interface of each material; The coefficient of friction of each material interface is determined based on the anti-slip capability and clamping force of the threaded connection sample at the interface of each material.

[0057] For example, the first and third connectors can be made of 20# steel, and the second connector can be made of 6082-T6 aluminum. In addition, other materials can be selected according to specific needs.

[0058] Once the friction coefficients of the interfaces of different materials are determined, when subsequently determining the anti-slip capability of the threaded connection, it is only necessary to obtain the clamping force of the threaded connection and the material of the interface. Specifically: the friction coefficient of the interface is determined based on the material of the interface; the anti-slip capability of the threaded connection is determined based on the friction coefficient of the interface and the clamping force of the threaded connection, thus improving the accuracy and efficiency of determining the anti-slip capability of the threaded connection.

[0059] This embodiment proposes a method for determining the interface friction coefficient of a threaded connection pair. The method involves preparing a threaded connection pair sample with a set clamping force; applying a lateral load to the sample until it fails; obtaining the lateral load borne by the failed sample as its anti-slip capability; and determining the interface friction coefficient based on the clamping force and anti-slip capability of the sample. This method achieves accurate determination of the interface friction coefficient in a threaded connection pair.

[0060] This invention also provides a system for determining the interface friction coefficient of a threaded connection pair, comprising: a threaded connection pair sample, a clamping force application tool, a testing machine, a data acquisition unit, and a data analysis and processing unit; A clamping force application tool is used to apply torque to the threaded connection assembly sample, so that the threaded connection assembly sample has a set clamping force; A testing machine is used to apply a transverse load to a threaded connection assembly sample with a set clamping force until the threaded connection assembly sample fails. The data acquisition unit is used to acquire the clamping force of the threaded connection sample and the lateral load it bears when the threaded connection sample fails. The data analysis and processing unit is used to take the lateral load borne by the threaded connection sample when it fails as the anti-slip capability of the threaded connection sample; and to determine the friction coefficient of the interface based on the clamping force and anti-slip capability of the threaded connection sample.

[0061] Furthermore, the threaded connection assembly includes a bolt, a nut, a first connector, a second connector, and a third connector; the first connector, the second connector, and the third connector are arranged sequentially; the bolt passes through the first connector, the second connector, and the third connector and then connects with the nut; the interface refers to the contact surface between the first connector and the second connector, and the contact surface between the second connector and the third connector.

[0062] Furthermore, the bottom surfaces of the first and second connectors are flat; the shape of the second connector is adapted to the shape of the load loading head of the testing machine.

[0063] Furthermore, the second connector is located within the load range of the testing machine.

[0064] It should be noted that the above-described system for determining the interface friction coefficient of a threaded connection pair is only illustrated by the division of the functional units described above. In practical applications, the functions described above can be assigned to different functional modules as needed, that is, the internal structure of the system can be divided into different functional modules to complete all or part of the functions described above. Furthermore, the above-described system for determining the interface friction coefficient of a threaded connection pair and the embodiment of a method for determining the interface friction coefficient of a threaded connection pair belong to the same concept; the specific implementation process is detailed in the method embodiment and will not be repeated here.

[0065] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for determining the friction coefficient at the interface of a threaded connection pair, characterized in that, include: Prepare a threaded connection assembly sample with a set clamping force; A transverse load is applied to a threaded connection sample with a set clamping force until the threaded connection sample fails. The transverse load borne by the threaded connection sample when it fails is used as the anti-slip capability of the threaded connection sample. The friction coefficient of the interface is determined based on the clamping force and anti-slip capability of the threaded connection sample.

2. The method for determining the interface friction coefficient of a threaded connection pair as described in claim 1, characterized in that, Multiple threaded connection pairs with different clamping forces were prepared. Determine the anti-slip capability of each threaded connection pair sample with different clamping forces; Based on the clamping force and anti-slip capability of each threaded connection pair sample with different clamping forces, multiple friction coefficients of the interface are determined. The final friction coefficient of the interface is obtained by averaging the multiple friction coefficients of the interface.

3. The method for determining the interface friction coefficient of a threaded connection pair as described in claim 2, characterized in that, Prepare multiple threaded connection pairs with the same clamping force; Determine the anti-slip capability of each threaded connection pair sample with the same clamping force; The minimum value among all threaded connection pairs with the same clamping force is selected as the anti-slip capability of the threaded connection pair sample with that clamping force.

4. The method for determining the interface friction coefficient of a threaded connection pair as described in claim 1, characterized in that, The results show that the threaded connection sample was subjected to multiple lateral loads and lateral displacements during the process from the application of lateral loads to the failure of the threaded connection sample. Based on the multiple lateral loads and lateral displacements borne by the threaded connection sample, determine the force-displacement characteristic curve of the threaded connection sample. The lateral load at which the slope of the force-displacement characteristic curve decreases to a set value is used as the anti-slip capability of the threaded connection pair sample.

5. The method for determining the interface friction coefficient of a threaded connection pair as described in claim 1, characterized in that, Based on the clamping force and anti-slip capability of the threaded connection sample, the friction coefficient of the interface is calculated and determined using the friction calculation formula.

6. The method for determining the interface friction coefficient of a threaded connection pair as described in claim 1, characterized in that, Based on the materials of various interfaces, various threaded connection pairs with set clamping forces were prepared; the friction coefficient of the interface for each material was determined. The friction coefficient of the interface with the same material as the interface in the threaded connection is selected as the friction coefficient of the interface in the threaded connection.

7. A system for determining the interface friction coefficient of a threaded connection pair, characterized in that, include: Threaded connection sample, clamping force application tool, testing machine, data acquisition unit and data analysis and processing unit; A clamping force application tool is used to apply torque to the threaded connection assembly sample, so that the threaded connection assembly sample has a set clamping force; A testing machine is used to apply a transverse load to a threaded connection assembly sample with a set clamping force until the threaded connection assembly sample fails. The data acquisition unit is used to acquire the clamping force of the threaded connection sample and the lateral load it bears when the threaded connection sample fails. The data analysis and processing unit is used to take the lateral load borne by the threaded connection sample when it fails as the anti-slip capability of the threaded connection sample; and to determine the friction coefficient of the interface based on the clamping force and anti-slip capability of the threaded connection sample.

8. The system for determining the interface friction coefficient of a threaded connection pair as described in claim 7, characterized in that, The threaded connection assembly includes a bolt, a nut, a first connector, a second connector, and a third connector; the first connector, the second connector, and the third connector are arranged sequentially; the bolt passes through the first connector, the second connector, and the third connector before connecting with the nut; the interface refers to the contact surface between the first connector and the second connector, and the contact surface between the second connector and the third connector.

9. The system for determining the interface friction coefficient of a threaded connection pair as described in claim 8, characterized in that, The bottom surfaces of the first and second connectors are flat; the shape of the second connector is adapted to the shape of the load loading head of the testing machine.

10. The system for determining the interface friction coefficient of a threaded connection pair as described in claim 8, characterized in that, The second connector is located within the load range of the testing machine.

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