A testing device for the tightening torque and axial force of a threaded structure.

Abstract

This invention relates to the field of mechanical assembly technology, specifically to a testing device for the tightening torque and axial force of a threaded structure. It includes an outer nut, a male connector, a fixed bracket, an axial force transmission component, a first ball bearing, and an axial force testing piece. The outer nut is threadedly connected to the first end of the male connector, and the second end of the male connector passes through the fixed bracket. The axial force testing piece is mounted on the fixed bracket. The axial force transmission component passes sequentially through the outer nut and the male connector, and makes point contact with the axial force testing piece via the first ball bearing. The purpose of this testing device for the tightening torque and axial force of a threaded structure is to solve the problem of the difficulty in measuring the tightening torque and axial force of complex threaded structures.

Description

Technical Field

[0001] This invention relates to the field of mechanical assembly technology, and more specifically to a testing device for the tightening torque and axial force of a threaded structure. Background Technology

[0002] Threaded connections are a detachable and reusable connection method widely used in various mechanical equipment. They are typically used to connect and fasten components. In the assembly of some precision structures, the tightening torque directly determines the magnitude of the axial force generated between the connected parts, affecting the reliability and functionality of the structure. Therefore, accurately obtaining the relationship between the tightening torque and axial force of a threaded connection can improve the assembly level of precision structures.

[0003] Scholars both domestically and internationally have derived the relationship between tightening torque and axial force through theoretical modeling, finite element simulation, and experimental design. These methods can provide satisfactory solutions for some commonly used threaded connection structures. However, as threaded connections are increasingly used in various complex and precision structures, these methods often have certain limitations.

[0004] (1) When using theoretical modeling methods to calculate the relationship between tightening torque and axial force, it is necessary to determine the friction coefficient of the threaded pair. For complex structures, it is also necessary to determine the friction coefficient of other contact surfaces and the bearing radius. The friction coefficient is affected by various factors such as material, surface roughness and surface lubrication process parameters. For complex structures using new materials and new surface treatment processes, the relevant parameters in theoretical modeling methods are not easy to determine.

[0005] (2) The finite element simulation method also needs to know the friction coefficient between the connected structures when calculating. In addition, the calculation accuracy of the finite element method is greatly related to factors such as mesh size and boundary condition settings. For complex precision structures, the calculation accuracy of the finite element method is difficult to measure.

[0006] (3) Traditional testing methods often use strain gauges to measure axial force for general threaded connections (such as bolts and nuts). Strain gauges are simply attached to the outer surface of the screw. However, for some special threaded connections (such as...), ... Figure 1 As shown, during the tightening process, the axial force generated by the threaded part under test acts on the inside of the outer nut, making it impossible for the strain gauge to be directly attached to the threaded part under test for measurement.

[0007] Therefore, the inventors have provided a testing device for the tightening torque and axial force of a threaded structure. Summary of the Invention

[0008] (1) Technical problems to be solved

[0009] This invention provides a testing device for the tightening torque and axial force of threaded structures, solving the technical problem of the difficulty in measuring the tightening torque and axial force of complex threaded structures.

[0010] (2) Technical solution

[0011] This invention provides a testing device for the tightening torque and axial force of a threaded structure, comprising an outer nut, a male connector, a fixed bracket, an axial force transmission component, a first ball bearing, and an axial force testing component; wherein,

[0012] The outer nut is threaded to the first end of the male connector, the second end of the male connector passes through the fixed bracket, the axial force test piece is mounted on the fixed bracket, and the axial force transmission component passes through the outer nut and the male connector in sequence and makes point contact with the axial force test piece through the first ball.

[0013] Furthermore, the testing device also includes a pad, and one end of the axial force test piece contacts the lower end face of the fixed bracket through the pad.

[0014] Furthermore, the testing device also includes a second ball bearing, and one end of the axial force test piece makes point contact with the pad block through the second ball bearing.

[0015] Furthermore, the fixed bracket includes a fixed plate and a support column, and a plurality of fixed plates arranged at intervals along the vertical direction are fixedly connected by the support column.

[0016] Furthermore, the fixing plate is a square flat plate structure with threaded holes for mating with other structures.

[0017] Furthermore, the support column is a columnar structure, and both ends of the multiple support columns are connected to the corners of the fixing plate.

[0018] Furthermore, the axial force transmission component is a cylindrical structure with stepped features, the outer diameter of its thick section is smaller than the internal thread of the outer nut, and it mates with the outer nut in the axial direction through a contact surface, and the outer diameter of its thin section is smaller than the inner diameter of the male connector.

[0019] Furthermore, the axial force test piece is a cylindrical structure with strain gauges for measuring axial deformation attached to its surface, or axial force data can be directly obtained using a pressure sensor.

[0020] Furthermore, when the axial force test piece is a stepped shaft structure, there are at least three fixing plates, and the lower end of each segment of the axial force test piece with the same diameter has a set gap with the adjacent lower fixing plate when the tightening torque is less than a set value.

[0021] Furthermore, the axial force test piece comprises multiple interconnected columnar sections whose radial dimensions decrease sequentially.

[0022] (3) Beneficial effects

[0023] In summary, this invention uses an axial force transmission component to transfer the axial force generated inside the threaded connection structure formed by the outer nut, male connector, and threaded component under test during assembly to an external axial force testing structure for measurement. This solves the problem that the axial force generated inside the complex threaded connection structure during tightening torque is difficult to measure. Furthermore, when testing threaded connectors of different specifications, only the thread specification on the male connector needs to be changed, and the corresponding outer nut replaced; no modification to the entire tooling is required, avoiding the cumbersome disassembly process. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the 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.

[0025] Figure 1 This is an assembly diagram of an existing threaded connection structure;

[0026] Figure 2 This is a schematic diagram of a test device for the tightening torque and axial force of a threaded structure provided in an embodiment of the present invention;

[0027] Figure 3 This is a cross-sectional view of a testing device for the tightening torque and axial force of a threaded structure provided in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of another threaded structure tightening torque and axial force testing device provided in an embodiment of the present invention;

[0029] Figure 5 This is a cross-sectional view of another threaded structure tightening torque and axial force testing device provided in an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of an axial force test piece with a stepped shaft structure provided in an embodiment of the present invention.

[0031] In the picture:

[0032] 1-Outer nut; 2-Male connector; 3-Fixing plate; 4-Support column; 5-Axial force transmission component; 6-First ball bearing; 7-Axial force test piece; 8-Pan block; 9-Second ball bearing; 100-Threaded part to be tested. Detailed Implementation

[0033] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention. That is, the present invention is not limited to the described embodiments, and any modifications, substitutions and improvements to the parts, components and connection methods are covered without departing from the spirit of the present invention.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "install" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Figure 2 This is a schematic diagram of a testing device for the tightening torque and axial force of a threaded structure provided in an embodiment of the present invention, as shown below. Figure 2-3 As shown, the testing device may include an outer nut 1, a male connector 2, a fixed bracket, an axial force transmission component 5, a first ball bearing 6, and an axial force testing component 7; the outer nut 1 is threaded to the first end of the male connector 2, the second end of the male connector 2 passes through the fixed bracket, the axial force testing component 7 is installed on the fixed bracket, and the axial force transmission component 5 passes through the outer nut 1 and the male connector 2 in sequence and makes point contact with the axial force testing component 7 through the first ball bearing 6.

[0038] In the above embodiment, the axial force generated inside the threaded connection structure formed by the outer nut 1, male connector 2, and threaded component 100 during assembly is transmitted to the external axial force testing structure for measurement via the axial force transmission component 5. For example... Figure 1As shown, during assembly, the threaded component 100 to be tested is connected to the male connector 2 via a threaded structure. During the tightening process, the threaded component 100 and the male connector 2 are mutually compressed, generating an axial force. Since the force-bearing part of the threaded component 100 is inside the outer nut 1 during the compression process, it is inconvenient to measure. Therefore, an axial force transmission component 5 is used instead of the threaded component 100 to transmit the generated axial force to the outside for measurement. This solves the problem that the axial force generated inside the structure during tightening torque in complex threaded connection structures is difficult to measure. At the same time, when testing threaded connectors of different specifications, only the specification of the thread on the male connector 2 needs to be changed and the corresponding outer nut 1 needs to be replaced. There is no need to modify the entire tooling, avoiding the cumbersome disassembly process.

[0039] When testing threaded connectors of different specifications, this testing device considers not only the friction between the outer nut 1 and the male connector 2 on the threaded surface, but also the friction between the outer nut 1 and the mating surface between the axial force transmission component 5, making the test results closer to the actual assembly results.

[0040] The outer nut 1 can be selected according to the actual thread structure. Figure 2-3 The inner part is only a certain type of outer nut, which contains threads that mate with the threaded structure on the male connector 2; the two ends of the male connector 2 mate with the fixed bracket and the outer nut 1 respectively, and serve to provide a threaded structure that mates with the outer nut 1. It is only necessary to ensure that the threads are consistent with the threads in the actual structure.

[0041] Meanwhile, the purpose of setting the first ball 6 on the contact surface between the axial force transmission component 5 and the axial force test component 7 is to ensure that there is no deviation during the transmission of axial force.

[0042] As an optional implementation method, such as Figure 2-3 As shown, the testing device also includes a pad 8, and one end of the axial force test piece 7 contacts the lower end face of the fixed bracket through the pad 8.

[0043] As an optional implementation method, such as Figure 3 As shown, the testing device also includes a second ball bearing 9, and one end of the axial force testing piece 7 makes point contact with the pad block 8 through the second ball bearing 9. The purpose of setting the second ball bearing 9 on the contact surface between the axial force testing piece 7 and the pad block 8 is to cooperate with the first ball bearing 6 to ensure that there is no deviation during the transmission of axial force.

[0044] As an optional implementation method, such as Figure 2 As shown, the fixed bracket includes a fixed plate 3 and a support column 4. Multiple fixed plates 3 are arranged at intervals along the vertical direction and are fixedly connected by the support column 4.

[0045] Specifically, the fixed bracket has a single-layer or multi-layer structure composed of multiple single layers, and the deformation at different positions of the axial force test piece 7 can be selected according to the magnitude of the tightening torque, thus realizing high-precision measurement of axial force under a wide range of tightening torques.

[0046] As an optional implementation, the fixing plate 3 is a square flat plate structure with threaded holes for mating with other structures. Specifically, such as... Figure 2 As shown, the fixing plate 3 is used to cooperate with other structures to fix the entire device.

[0047] As an optional implementation, the support column 4 is a columnar structure, with both ends of multiple support columns 4 connected to the corners of the fixing plate 3. Specifically, as shown... Figure 2 As shown, there are four or more sets of support pillars 4, located at the four corners of the square fixing plate 3, which are used to support the entire test device.

[0048] As an optional implementation method, such as Figure 6 As shown, the axial force transmission component 5 is a cylindrical structure with stepped features. Its thicker section has an outer diameter smaller than the internal thread of the outer nut 1, and mates with the outer nut 1 via a contact surface in the axial direction. Its thinner section has an outer diameter smaller than the inner diameter of the male connector 2. The specific structure of the axial force transmission component 5 is designed to facilitate simultaneous threaded assembly with both ends of the outer nut 1 and the male connector 2. The shapes of its two ends are adapted to the corresponding internal threads of the outer nut 1 and the inner cavity of the male connector 2, respectively, and will not be elaborated upon here.

[0049] As an optional implementation method, such as Figure 2 As shown, the axial force test piece 7 is a cylindrical structure with strain gauges attached to its surface for measuring axial deformation, or axial force data can be directly obtained using a pressure sensor. The axial force test piece 7 serves as a replacement for the threaded part 100 under test. The axial force of the axial force test piece 7 obtained by the strain gauges or pressure sensor is the axial force experienced by the threaded part 100 under test during assembly.

[0050] As an optional implementation method, such as Figure 4-5 As shown, there are at least three fixing plates 3, and the lower end of each segment of the axial force test piece 7 of the same diameter has a set gap with the adjacent lower fixing plate 3 when the tightening torque is less than the set value.

[0051] Specifically, when testing a wide range of tightening torques, a multi-layer structure can be constructed by stacking a single-layer structure. The axial force test piece 7 uses a stepped shaft structure, with the thicker shaft on the upper layer of the device. Holes are opened between the layers, and there is a certain gap between the end faces where the thick and thin shafts meet and the layers (e.g., ...). Figure 5As shown, the thick shaft of the axial force test piece 7 and the layer plate are shown. Assuming the length of the thin shaft of the axial force test piece is L, the moment of inertia of the section is I, and the area of ​​the cross section is A, the initial gap d between the end face of the thick shaft and the layer plate is calculated according to the following formula. When the measured tightening torque is small, the deformation of the thin shaft of the axial force test piece is easier to measure, and the axial force data is obtained from the deformation of the thin shaft. When the tightening torque is about to exceed the bearing limit of the thin shaft, the end face of the thick shaft contacts the layer plate, and the columns of the thin shaft layer will bear the axial load simultaneously with the thin shaft, thus preventing buckling of the thin shaft. At this time, the thick shaft of the axial force test piece can also produce easily measurable deformation, and the axial force measurement data will be obtained from the thick shaft.

[0052] As an optional implementation, the axial force test piece 7 comprises multiple interconnected columnar sections with successively decreasing radial dimensions. Specifically, a specific structural form of the axial force test piece 7 with a stepped shaft structure is given, similar to a telescopic mobile phone selfie stick, but the difference is that each column is fixedly connected and there is no axial telescopic movement between them.

[0053] Example 1

[0054] This testing device for the tightening torque and axial force of the threaded structure was applied to the testing of aviation hydraulic pipe fittings. For a certain type of pipe fitting, the outer nut and the male fitting are connected using an MJ14*1.5 threaded structure. The inner diameter of the outer nut is 12.54mm, the inner diameter of the male fitting is 7mm, the thickness of the fixing plate is 10mm, and the support uses a 10mm diameter cylinder. The contact surface between the axial force transmission component and the outer nut is machined according to the actual structure. The axial force test piece uses a 5mm diameter cylinder made of steel with an elastic modulus of 200GPa. The testing device is then installed according to… Figure 2 Assemble the device by fixing it on the workbench, attaching strain gauges along the axial direction of the axial force test piece, and connecting strain sensors. During the test, use a torque wrench to control the tightening torque, read the axial deformation of the axial force test piece through the sensor, and obtain the magnitude of the axial force based on the elastic modulus of the axial force test piece.

[0055] The experiment revealed that when the tightening torque was 18 Nm, 20 Nm, and 22 Nm, the axial forces on the test piece were 8571 N, 9524 N, and 10477 N, respectively. Based on the calculation formulas for tightening torque and axial force:

[0056] T = kFd;

[0057] In the formula, T is the tightening torque, F is the axial force, d is the nominal diameter of the thread, and k is the tightening torque coefficient. Based on the obtained test data, the value of k is 0.15. Thus, the relationship between tightening torque and axial force has been obtained.

[0058] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0059] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A testing device for the tightening torque and axial force of a threaded structure, characterized in that, Includes an outer nut (1), a male connector (2), a fixed bracket, an axial force transmission component (5), a first ball bearing (6), and an axial force test piece (7); among which, The outer nut (1) is threaded to the first end of the male connector (2), the second end of the male connector (2) passes through the fixed bracket, the axial force test piece (7) is installed on the fixed bracket, and the axial force transmission piece (5) passes through the outer nut (1) and the male connector (2) in sequence and makes point contact with the axial force test piece (7) through the first ball (6); The axial force transmission component (5) is a columnar structure with stepped features. Its thick section has an outer diameter smaller than the internal thread of the outer nut (1) and it engages with the outer nut (1) through a contact surface in the axial direction. Its thin section has an outer diameter smaller than the inner diameter of the male connector (2). It also includes a pad (8), one end of the axial force test piece (7) is in contact with the lower end face of the fixed bracket through the pad (8); It also includes a second ball (9), one end of the axial force test piece (7) making point contact with the pad (8) through the second ball (9).

2. The testing device for tightening torque and axial force of threaded structures according to claim 1, characterized in that, The fixed bracket includes a fixed plate (3) and a support column (4), and multiple fixed plates (3) arranged at intervals along the vertical direction are fixedly connected by the support column (4).

3. The testing device for tightening torque and axial force of threaded structures according to claim 2, characterized in that, The fixing plate (3) is a square flat plate structure with threaded holes for cooperating with other structures.

4. The testing device for tightening torque and axial force of threaded structures according to claim 2, characterized in that, The support column (4) is a columnar structure, and both ends of the multiple support columns (4) are connected to the corners of the fixing plate (3).

5. The testing device for tightening torque and axial force of threaded structures according to claim 1, characterized in that, The axial force test piece (7) is a cylindrical structure with strain gauges attached to its surface for measuring axial deformation, or axial force data can be obtained directly using a pressure sensor.

6. The testing device for tightening torque and axial force of threaded structures according to claim 2, characterized in that, When the axial force test piece (7) is a stepped shaft structure, there are at least three fixing plates (3), and the lower end of each section of the same diameter of the axial force test piece (7) has a set gap with the adjacent lower fixing plate (3) when the tightening torque is less than the set value.

7. The testing device for tightening torque and axial force of threaded structures according to claim 6, characterized in that, The axial force test piece (7) comprises multiple columnar sections that are interconnected and whose radial dimensions decrease sequentially.

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