A bolted interface friction coefficient testing device and method

Abstract

The application discloses a bolt connection interface friction coefficient testing device and method, and relates to the field of railway vehicle structures. The testing device comprises a first connecting piece, a second connecting piece, a detection bolt, a detection nut and a thrust generating device. The detection bolt and the detection nut are threadedly connected. The first connecting piece and the second connecting piece are located between the screw head of the detection bolt and the detection nut. The first connecting piece and the second connecting piece abut against each other in response to the thrust of the screw head of the detection bolt and the detection nut. The thrust generating device is used for applying thrusts in opposite directions to the first connecting piece and the second connecting piece respectively, and the directions of the thrusts are perpendicular to the axis of the detection bolt. The application effectively detects the friction coefficient of the screw connection interface of the first connecting piece and the second connecting piece by simulating the movement of the first connecting piece and the second connecting piece overcoming friction.

Description

Technical Field

[0001] This application relates to the technical field of rail vehicle structures, and more specifically, to a test apparatus and method for the friction coefficient of bolted connection interfaces. Background Technology

[0002] The bolted connections on the bogies of many rail transit vehicles cannot meet the new anti-slip performance requirements, and increasing the interfacial friction coefficient is the simplest and most effective method. According to the VDI2230 high-strength bolted connection system calculation guide, in the absence of supporting experimental data, the interfacial friction coefficient of the bolted connection is set to the default value of 0.15. To verify the true strength of the bolted connection, the demand for interfacial friction coefficient testing has surged.

[0003] In summary, how to detect the friction coefficient at the interface of bolted connections is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a test device and method for the interface friction coefficient of bolted connections, which can effectively detect the interface friction coefficient of bolted connections.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] A bolt connection interface friction coefficient testing device includes a first connector, a second connector, a test bolt, a test nut, and a thrust generating device. The test bolt and the test nut are threadedly connected. The first connector and the second connector are located between the threaded head of the test bolt and the test nut. The first connector and the second connector abut against the thrust of the threaded head of the test bolt and the test nut. The thrust generating device is used to apply thrusts in opposite directions to the first connector and the second connector, and the direction of the thrusts is perpendicular to the axis of the test bolt.

[0007] Preferably, there is one first connector and two second connectors, with the two second connectors abutting against opposite sides of the first connector, and the head of the detection bolt and the detection nut abutting against the side of the second connector away from the first connector.

[0008] Preferably, both the first connector and the second connector have through holes for the detection bolt to pass through.

[0009] Preferably, the thrust generating device includes a test base, which simultaneously contacts two of the second connecting members, and the output end of the thrust generating device abuts against the side of the first connecting member opposite to the test base.

[0010] Preferably, the thrust generating device further includes a test block, which includes a bearing part and a contact part that are fixedly connected to each other. The output end of the thrust generating device abuts against the bearing part, and the contact part cooperates with the first connecting member to abut against each other.

[0011] Preferably, the first connector is annular and coaxial with the detection bolt, and the contact portion has a mating groove, with the outer wall of the first connector abutting against the groove wall.

[0012] Preferably, the width of the contact portion is less than the distance between the two second connectors.

[0013] Preferably, the test base has a clearance groove, the opening of the clearance groove is directly opposite the first connector, and the width of the clearance groove is greater than the width of the first connector.

[0014] Preferably, the test base is further provided with two placement slots, which are located on both sides of the opening of the relief slot, and each placement slot is for placing one of the second connectors.

[0015] An experimental method using the above-mentioned bolt connection interface friction coefficient testing device includes:

[0016] Two second connectors clamp one first connector, the detection bolt passes through the second connectors and the first connector, and the detection nut is screwed onto the detection bolt;

[0017] Tighten the detection nut and monitor the preload of the detection nut and detection bolt in real time. Stop tightening when the target preload is reached and record the preload at this time as P.

[0018] The first and second connectors, which are close together, are placed on the test base, and the output end of the thrust generating device applies a thrust toward the test base to the first connector.

[0019] The thrust is gradually applied until the first and second connecting parts slide. The load N at this point is recorded, and the anti-slip coefficient is then obtained.

[0020] ;

[0021] Where k is the number of contact surfaces between the first connector and the second connector.

[0022] The bolt connection interface friction coefficient testing device and method provided in this application involve a first connector and a second connector being simultaneously penetrated by a test bolt. After the test nut is tightened to the target preload, the first connector and the second connector are pressed tightly against each other, and are in a state of simulated bolt connection fixation. In this state, a thrust generating device applies opposite thrusts parallel to their contact surfaces to the two connectors, causing them to have a relative sliding tendency. The ratio of the thrust to the preload when the two connectors actually slide can intuitively show the friction coefficient of the bolt connection interface. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram illustrating the connection and mating structure of the first connector, the second connector, the detection bolt, and the test base in the embodiments of this application;

[0025] Figure 2 This is a side view schematic diagram of the structure used to illustrate the test device for the friction coefficient of bolt connection interface in the embodiments of this application;

[0026] Figure 3 This is a schematic diagram illustrating the structure of the experimental pressure block placed above the first connecting member in an embodiment of this application;

[0027] Figure 4 This is a schematic diagram illustrating the structure of the experimental pressing block in the embodiments of this application.

[0028] Figures 1-4 In the accompanying drawings, the reference numerals include:

[0029] 1. First connector; 2. Second connector; 3. Inspection bolt; 4. Inspection nut; 5. Test base; 51. Relief groove; 52. Placement groove; 6. Test block; 61. Bearing part; 62. Contact part; 63. Mating groove. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar words used in this application do not indicate any order, quantity, or importance. Terms such as "connection" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. This application discloses a device and method for testing the friction coefficient of a bolted connection interface.

[0032] The core of this application is to provide a test device and method for the friction coefficient of bolted connection interfaces.

[0033] Please refer to Figure 1 and Figure 2 .

[0034] The bolt connection interface friction coefficient testing device provided in this application includes a first connector 1, a second connector 2, a test bolt 3, a test nut 4, and a thrust generating device. The test bolt 3 and the test nut 4 are connected by a threaded fit. After assembly, the first connector 1 and the second connector 2 are clamped between the thread head of the test bolt 3 and the test nut 4.

[0035] The surface roughness of the contact surfaces of the first connector 1 and the second connector 2 used for testing is consistent with the actual surface roughness of their contact surfaces on the bogie. Relying on the tightening force of the testing bolt 3 and the testing nut 4, the bolt head of the testing bolt 3 and the testing nut 4 clamp the two components together, causing the first connector 1 and the second connector 2 to come into close contact, simulating the tightness of the bolted connection on the bogie. The bolt preload at this point is detected using existing technology, and the normal pressure between the two components is approximately equal to the measured preload.

[0036] A thrust generating device (not shown in the figure) is used to apply thrusts in opposite directions to the first connector 1 and the second connector 2, with the direction of the thrusts perpendicular to the axis of the detection bolt 3 and parallel to the contact surface between the first connector 1 and the second connector 2. This thrust causes the first connector 1 and the second connector 2 to tend to slide relative to each other radially along the detection bolt 3. The ratio of the thrust magnitude (when it causes substantial sliding between the first connector 1 and the second connector 2) to the measured bolt preload directly reflects the coefficient of friction at the bolt connection interface.

[0037] The following description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed account of the bolt connection interface friction coefficient testing device and method provided in this application.

[0038] In one specific implementation, reference is made to... Figure 1 and Figure 2 .

[0039] Specifically, there is one first connector 1 and two second connectors 2, which are respectively fitted against the two opposite sides of the first connector 1. The detection bolt 3 passes through the two second connectors 2 and the middle first connector 1 in sequence. The screw head of the detection bolt 3 is fitted against the side of one of the second connectors 2 that is away from the first connector 1. After the detection nut 4 is tightened, it is fitted against the side of the other second connector 2 that is away from the first connector 1.

[0040] Tightening the testing nut 4 achieves pre-clamping of the first connecting piece 1 and the second connecting piece 2, meaning there are two contact surfaces between the first connecting piece 1 and the second connecting piece 2, and the first connecting piece 1 does not contact the testing bolt 3 and the testing nut 4; during the process of applying a pushing force to the first connecting piece 1 and the second connecting piece 2, the two second connecting pieces 2 remain relatively stationary, so the friction between the second connecting piece 2 and the first connecting piece 1 is not affected by the testing bolt 3 and the testing nut 4, resulting in higher accuracy of the test results.

[0041] Based on the above embodiments, refer to Figure 1 .

[0042] Specifically, through holes are provided at corresponding positions of the first connector 1 and the second connector 2. The size of the through holes must be larger than the shank size of the test bolt 3 to ensure that the test bolt 3 can pass through smoothly without contacting the hole wall. After assembly, the test bolt 3 remains coaxial with the through holes of the first connector 1 and the second connector 2, reducing the bending deformation of the first connector 1 or the second connector 2 caused by unbalanced preload distribution, and ensuring that the preload is evenly transmitted to the interface.

[0043] Based on the above embodiments, refer to Figure 1 and Figure 2 .

[0044] Specifically, the thrust generating device includes a test base 5, which is in contact with two second connecting members 2 at the same time, and the output end of the thrust generating device abuts against the side of the first connecting member 1 away from the test base 5.

[0045] When applying thrust, the test base 5 is placed on the platform of the thrust generator. The axis of the test bolt 3 is horizontal. The test base 5 is located below the first connector 1 and the second connector 2. It abuts against the lower side of the two second connectors 2, but does not contact the first connector 1.

[0046] The output end of the thrust generating device applies a thrust to the first connecting member 1 from top to bottom without touching the second connecting member 2, so that the second connecting member 2 remains stationary under the support of the test base 5. At this time, the thrust applied by the thrust generating device to the first connecting member 1 is basically equal to the static friction force on the first connecting member 1.

[0047] Based on the above embodiments, refer to Figure 3 and Figure 4 .

[0048] Specifically, the pressure generating device is also equipped with a test block 6, which is divided into a bearing part 61 and a contact part 62. The two parts are fixedly connected as a whole. The bearing part 61 is used to receive the pressure output end of the pressure generating device, and the contact part 62 directly abuts against the first connecting piece 1 to ensure that each component is subjected to uniform force when the thrust is transmitted.

[0049] The first connector 1 has an overall ring-shaped structure and is coaxially arranged with the detection bolt 3. The contact part 62 has a corresponding mating groove 63. The inner wall of the mating groove 63 fits tightly with the outer wall of the first connector 1 to achieve precise alignment and force application, preventing the force direction of the first connector 1 from shifting during the force application process. The second connector 2 is a square plate with a through hole located at the center of its surface.

[0050] In the specific implementation process, the mating groove 63 is preferably an isosceles trapezoidal groove or a V-shaped groove.

[0051] The width of the contact portion 62 is less than the distance between the two second connectors 2, ensuring that the contact portion 62 only contacts the first connector 1 during the pressure application process and does not touch the second connectors 2 on both sides, so as not to affect the force data.

[0052] Based on the above embodiments, refer to Figures 1-3 .

[0053] Specifically, the test base 5 has a clearance groove 51 on its side. The opening of the clearance groove 51 is directly opposite the first connecting member 1 above it. The width of the groove is greater than the width of the first connecting member 1, so as to reserve sufficient space for the first connecting member 1 to slide under force, and thus the test base 5 will not obstruct the sliding of the first connecting member 1.

[0054] Furthermore, the test base 5 has a placement slot 52 on each side of the opening of the relief groove 51. The two placement slots 52 are symmetrically arranged, and each placement slot 52 corresponds to a second connector 2. The size of the placement slot 52 is adapted to the bottom of the second connector 2, which can limit the two second connectors 2 that are simultaneously close to both sides of the first connector 1, improve the positional accuracy of the first connector 1 and the second connector 2 relative to the test base 5, and reduce the possibility of displacement of them relative to the test base 5 during the test, thereby further improving the accuracy of the test results.

[0055] The bolt connection interface friction coefficient test method provided in this application uses the bolt connection interface friction coefficient test device in the above embodiment, and includes the following steps:

[0056] S1: Complete the assembly of the test components. Place the first connector 1 between the two second connectors 2, so that the two second connectors 2 clamp the first connector 1 from both sides, and adjust the positions of the three to keep them aligned; then, the test bolt 3 passes through one of the second connectors 2, the first connector 1, and the other second connector 2 in sequence, align the test nut 4 with the threaded end of the test bolt 3, and screw it smoothly onto the test bolt 3 to complete the initial assembly. In the specific implementation process, the test bolt 3 is an M30 bolt, and the diameter of the through hole on the first connector 1 and the second connector 2 for the test bolt 3 to pass through is 33mm.

[0057] S2: Apply the target preload. Using a dedicated preload testing device and a torque tool, gradually and evenly tighten the test nut 4, monitoring the preload value between the test bolt 3 and the test nut 4 in real time. Continue to slowly tighten until the preload reaches the preset target value, then immediately stop tightening and accurately record the stable preload value at this point as P. In the specific implementation process, an ultrasonic bolt axial force tester is used to test the axial preload of the bolt.

[0058] S3: Place the assembled and pre-tightened first connector 1 and second connector 2 stably on the test base 5. The test base 5 is placed on the placement platform or fixture of the pressure generating device, ensuring that the bottom of the second connector 2 is fully embedded in the corresponding placement groove 52. Then, place the test block 6, and engage the contact part 62 of the test block 6 with the groove 63 on the upper side of the first connector 1, so that the output end of the pressure generating device accurately abuts against the upper side of the bearing part 61 of the test block 6. In specific implementation, the pressure generating device can be a hydraulic press or a tensile testing machine, etc.

[0059] S4: Start the pressure generating device and smoothly apply a downward thrust to the test block 6 through the output end. The direction of the thrust is perpendicular to the axis of the test bolt 3. The thrust is applied slowly in stages, maintaining a brief period of stability after each stage, and continuously observing the relative state between the first connecting member 1 and the second connecting member 2. Continue to apply the thrust until there is obvious relative slippage between the first connecting member 1 and the second connecting member 2, or the curve recorded by the pressure generating device shows a downward inflection point or a significant change in slope. At this point, immediately stop the loading and record the critical load value output by the pressure generating device as N.

[0060] Based on the preload P and critical load N obtained from the experiment, and combined with the number of contact surfaces k between the first connector 1 and the second connector 2, the final friction coefficient μ of the bolt connection interface is obtained:

[0061]

[0062] In this embodiment, the first connector 1 is in contact with two second connectors 2 on both sides, so the number of contact surfaces k is 2.

[0063] This device and method can stably output anti-slip coefficient test results and ensure that the test results are consistent with the actual application of bolted connections. Furthermore, the test device is compact and simple in structure, and can be used on various pressure generating devices, greatly reducing testing requirements and costs.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0065] The foregoing has provided a detailed description of the testing device and method for the interface friction coefficient of bolted connections. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A test device for the coefficient of friction at the interface of a bolted connection, characterized in that, The device includes a first connector (1), a second connector (2), a detection bolt (3), a detection nut (4), and a thrust generating device. The detection bolt (3) and the detection nut (4) are threaded together. The first connector (1) and the second connector (2) are located between the head of the detection bolt (3) and the detection nut (4). The first connector (1) and the second connector (2) abut against the thrust of the head of the detection bolt (3) and the detection nut (4). The thrust generating device is used to apply thrusts in opposite directions to the first connector (1) and the second connector (2), and the direction of the thrusts is perpendicular to the axis of the detection bolt (3).

2. The test device for the friction coefficient of bolted connection interfaces according to claim 1, characterized in that, There is one first connector (1) and two second connectors (2). The two second connectors (2) abut against the opposite sides of the first connector (1). The head of the detection bolt (3) and the detection nut (4) abut against the side of the second connector (2) away from the first connector (1).

3. The test device for the coefficient of friction at the interface of a bolted connection according to claim 2, characterized in that, Both the first connector (1) and the second connector (2) have through holes for the detection bolt (3) to pass through.

4. The test apparatus for the coefficient of friction at the interface of a bolted connection according to claim 2 or 3, characterized in that, The thrust generating device includes a test base (5), which is in contact with two second connecting members (2) at the same time. The output end of the thrust generating device and the first connecting member (1) abut against the side away from the test base (5).

5. The test device for the coefficient of friction at the interface of a bolted connection according to claim 4, characterized in that, The thrust generating device further includes a test block (6), which includes a bearing part (61) and a contact part (62) that are fixedly connected to each other. The output end of the thrust generating device abuts against the bearing part (61), and the contact part (62) and the first connecting member (1) cooperate to abut against each other.

6. The test apparatus for the interface friction coefficient of bolted connections according to claim 5, characterized in that, The first connector (1) is annular and coaxial with the detection bolt (3). The contact part (62) has a mating groove (63), and the outer wall of the first connector (1) abuts against the groove wall of the mating groove (63).

7. The test apparatus for the coefficient of friction at the interface of a bolted connection according to claim 5, characterized in that, The width of the contact portion (62) is less than the distance between the two second connectors (2).

8. The test device for the coefficient of friction at the interface of a bolted connection according to claim 4, characterized in that, The test base (5) has a relief groove (51), the opening of the relief groove (51) is directly opposite the first connector (1), and the width of the relief groove (51) is greater than the width of the first connector (1).

9. The test apparatus for the coefficient of friction at the interface of a bolted connection according to claim 8, characterized in that, The test base (5) is also provided with a placement slot (52). There are two placement slots (52) and they are located on both sides of the opening of the relief slot (51). Each placement slot (52) is used to place one of the second connectors (2).

10. A test method using the bolt connection interface friction coefficient test apparatus according to any one of claims 4-9, characterized in that, include: Two second connectors (2) clamp one first connector (1), the detection bolt (3) passes through the second connectors (2) and the first connector (1), and the detection nut (4) is screwed onto the detection bolt (3); Tighten the detection nut (4), and detect the preload of the detection nut (4) and the detection bolt (3) in real time. Stop tightening when the target preload is reached, and record the preload at this time as P. The first connector (1) and the second connector (2) that are close to each other are placed on the test base (5), and the output end of the thrust generating device applies a thrust toward the test base (5) to the first connector (1). The thrust is gradually applied until the first connecting member (1) and the second connecting member (2) slide. The load N at this time is recorded, and the anti-slip coefficient is obtained: ； Where k is the number of contact surfaces between the first connector (1) and the second connector (2).

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