Method for testing installation torque of in-service threaded fastener

Abstract

The invention provides a method for testing the installation torque of an in-service threaded fastener, and the method comprises the following steps: S1, rotating the threaded fastener at a first angle in a loosening direction, enabling an internal thread and an external thread of a thread meshing region of the threaded fastener to slide, and rotating the threaded fastener at the first angle in a fastening direction; and S2, the threaded fastener is rotated at a second angle in the fastening direction, and the kinetic friction torque during rotation is collected to serve as the installation torque of the threaded fastener. The beneficial effects of the invention are that compared with a traditional testing scheme, a mode of loosening first and then fastening is adopted, it is ensured that the threaded fastener is in a relative slippage state of internal and external threads when rotating at a second angle, and the accuracy of a testing result is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of threaded fasteners, and in particular relates to a method for testing the installation torque of in-service threaded fasteners. Background Art

[0002] Torque is the core execution parameter in common installation standards. The installation torque test after equipment assembly is an important part of acceptance and quality assessment. During the service of equipment, due to factors such as vibration, temperature change, creep, etc., the connection performance of the fastening structure will gradually decrease over time. Therefore, regular torque testing of bolts in service equipment is of great significance to the operation and safety of equipment.

[0003] At present, some simple bolt torque test methods have been formed in some industries, mainly including the following: First, if the specified installation torque of a certain structure is XNm, then a torque of XNm is applied to the in-service bolt in the tightening direction. If the bolt head does not rotate, it is judged as qualified, and if the bolt head rotates, it is judged as unqualified. The test error caused by the difference between the static friction coefficient and the dynamic friction coefficient is not considered. If the difference between the static and dynamic friction coefficients is large (the difference between the static and dynamic friction coefficients is related to the material pairing), it is likely that even if the installation torque applied during the installation process is lower than the specified torque, the bolt head cannot be rotated when the specified torque is applied during the detection process, resulting in the actual installation torque of the connection structure that is judged to be qualified being lower than the specified value, which poses a safety hazard; second, use a torque wrench to slowly tighten the bolt in the loosening direction to loosen it slowly, read the torque value at the moment of starting to rotate, and judge the torque value at the moment of loosening as the current installation torque. But in fact, due to the existence of the helix angle, the forces on the bolt in the tightening direction and the loosening direction are asymmetric. Under the same preload, the installation torque of the bolt is usually 20%-50% higher than the loosening torque. This ratio is related to the friction coefficient and structural dimensions of each contact interface and cannot be accurately given. It is not scientific to judge the loosening torque as the installation torque error is too large. Summary of the invention

[0004] In view of this, the present invention aims to provide a method for testing the installation torque of an in-service threaded fastener, in order to solve at least one of the above-mentioned technical problems.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A first aspect of the present invention provides a method for testing the installation torque of an in-service threaded fastener, comprising the following steps:

[0007] S1, rotating the threaded fastener at a first angle in a loosening direction, causing the internal threads and external threads in the threaded engagement area of ​​the threaded fastener to slip, and rotating the threaded fastener at a first angle in a tightening direction;

[0008] S2. Rotate the threaded fastener at a second angle along the tightening direction, and collect the dynamic friction torque during the rotation as the installation torque of the threaded fastener.

[0009] Furthermore, it also includes:

[0010] S3. Rotate the threaded fastener at a second angle in a loosening direction.

[0011] Further, the first angle is not less than a critical angle for loosening of the threaded fastener;

[0012] The formula for calculating the critical angle of loosening of threaded fasteners is as follows:

[0013]

[0014] Where l is the clamping length, I P is the polar moment of inertia of the screw, G is the shear modulus of the screw material, T T is the design installation torque, T l To loosen the torque.

[0015] Furthermore, the calculation formula of the first angle is as follows:

[0016]

[0017] Among them, θ loose is the first angle, a is the calculation coefficient, l is the clamping length, and d is the diameter of the threaded fastener.

[0018] Furthermore, the first angle has a value range of 15° to 35°.

[0019] Furthermore, the second angle has a value range of 0.5° to 2°;

[0020] The process of collecting the dynamic friction torque when rotation occurs is as follows:

[0021] Torque data is collected in real time during the process of rotating the threaded fastener at a second angle along the tightening direction, and a torque-time curve is produced according to the torque data and time. The torque data when the torque-time curve reaches a first peak is the static friction torque, and the torque data of the first valley value after the torque-time curve reaches the first peak is the dynamic friction torque.

[0022] Furthermore, the working time of the threaded fastener is determined before S1;

[0023] If the working time of the threaded fastener is short, proceed to step S2;

[0024] If the working time of the threaded fastener is long, proceed to step S1;

[0025] The method for determining the working time of a threaded fastener comprises the following steps:

[0026] Rotate the threaded fastener in the tightening direction, collect the torque and preload, and if the preload increases with the rotation angle and the torque and the rotation angle change nonlinearly, it is determined that the working time of the threaded fastener is short.

[0027] A second aspect of the present invention provides an electronic device, comprising a processor and a memory communicatively connected to the processor and used to store instructions executable by the processor, wherein the processor is used to execute the method described in the first aspect above.

[0028] The third aspect of the present invention provides a server, comprising at least one processor, and a memory communicatively connected to the processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the processor so that the at least one processor executes the method described in the first aspect.

[0029] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the method described in the first aspect.

[0030] Compared with the prior art, the method for testing the installation torque of an in-service threaded fastener according to the present invention has the following beneficial effects:

[0031] (1) Compared with the traditional testing scheme, the method for testing the installation torque of an in-service threaded fastener described in the present invention adopts a method of loosening first and then tightening, thereby ensuring that the internal and external threads of the threaded fastener are in a state of relative slip when the threaded fastener is rotated at a second angle, thereby ensuring the accuracy of the test result.

[0032] (2) The present invention provides a method for testing the installation torque of an in-service threaded fastener, which improves the testing efficiency by using different testing methods for bolts with different service times. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 This is a flow chart of the testing method according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a torque variation curve of a threaded fastener at different working times according to an embodiment of the present invention;

[0036] Figure 3It is a schematic diagram of a torque variation curve of a threaded fastener when rotating at a second angle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0040] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0041] Embodiment 1:

[0042] like Figures 1 to 3 As shown, a method for testing the installation torque of an in-service threaded fastener comprises the following steps:

[0043] Determine the working time of the threaded fastener before S1;

[0044] If the working time of the threaded fastener is short, proceed to step S2;

[0045] If the working time of the threaded fastener is long, proceed to step S1;

[0046] The working time of threaded fasteners is the time from the completion of assembly of threaded fasteners to the implementation of this plan.

[0047] In some embodiments, the method for determining the working time of a threaded fastener comprises the following steps:

[0048] Rotate the threaded fastener in the tightening direction, collect the torque and preload, and if the preload increases with the rotation angle, and the torque and rotation angle change nonlinearly, the threaded fastener is judged to have a short working time. Figure 2 (shown)

[0049] Threaded fasteners can be a combination of bolts and nuts, and the installation torque is tested by turning one of the bolts or nuts. Threaded fasteners can also be a combination of a bolt and a threaded connection of a plate, and the installation torque is tested by turning the bolt. Threaded fasteners can also be a combination of an internally threaded tube and an externally threaded tube, and the installation torque is tested by turning one of the threaded tubes.

[0050] In other embodiments, the working time of the threaded fastener can be determined by assembly records and other methods. The working time of the threaded fastener is short if it is within 72 hours after assembly, and long if it is more than 72 hours after assembly.

[0051] S1, rotating the threaded fastener at a first angle in a loosening direction, causing the internal threads and external threads in the threaded engagement area of ​​the threaded fastener to slip, and rotating the threaded fastener at a first angle in a tightening direction;

[0052] S2. Rotate the threaded fastener at a second angle along the tightening direction, and collect the dynamic friction torque during the rotation as the installation torque of the threaded fastener.

[0053] S3. Rotate the threaded fastener at a second angle in a loosening direction.

[0054] In some embodiments, the first angle is not less than a critical angle for loosening of the threaded fastener;

[0055] The formula for calculating the critical angle of loosening of threaded fasteners is as follows:

[0056]

[0057] Where l is the clamping length, I P is the polar moment of inertia of the screw, G is the shear modulus of the screw material, T T The design installation torque here is not the installation torque that needs to be measured in the present invention. The design installation torque of the present application is obtained by calculating the design preload force. L To loosen the torque.

[0058] Installation torque T T and loosening torque T L Meaning and composition: Design installation torque T of the boltT It refers to the critical torque value applied when tightening the bolt in order to produce a certain preload. The calculation formula is as follows:

[0059]

[0060] Among them, F is the design preload, d2 is the bolt diameter, α is the thread half angle, P is the thread pitch, and d w is the equivalent friction diameter of the bearing surface, μ w is the friction coefficient of the bearing surface. The formula contains 3 items in total. The first item is the friction torque between the meshing thread surfaces when the thread lead angle is not considered, the second item is the additional friction torque caused by the lead angle, and the third item is the friction torque of the bearing surface. The first and third items overcome the interface friction, and the second item is the item that converts the torque into effective preload.

[0061] Loosening torque T L It is the critical torque value at which the preload force of the tightened bolt begins to decrease. The calculation formula is as follows:

[0062]

[0063] Loosening torque T L The calculation formula is simply to replace the installation torque T T The "+" sign in the second item of the calculation formula is changed to a "-" sign. This is because the second item is the additional friction torque caused by the lead angle, which plays a negative role when loosening. Therefore, for bolts of the same specification and the same tightening state, the installation torque and loosening torque are different values ​​(according to theoretical calculations, when the interface friction coefficient is 0.15, the difference between the two is 22%, and the actual value is higher).

[0064] When the bolt is already assembled and the bolt is tightened slowly, the rotation of the bolt head or nut will not immediately cause the internal and external threads to slip relative to each other. Instead, the residual torque value in the tightening direction will first accumulate in the screw. When the applied torque accumulates to a certain extent, exceeding T T When the thread slips, the preload will continue to rise, and the bolt will really start to be tightened. If the torque or angle of rotation is lower than the limit value, the connection state of the bolt will not be affected.

[0065] The same is true for the loosening direction. When the bolt head or nut rotates, it first offsets the residual torque of the screw in the tightening direction, and then gradually accumulates the residual torque in the loosening direction. When the torque accumulates to more than T L , the thread will slip, the preload will decrease, and the bolt will actually begin to be loosened.

[0066] In some other embodiments, the calculation formula of the first angle is as follows:

[0067]

[0068] Among them, θ loose is the first angle, a is the calculation coefficient, l is the clamping length, and d is the diameter of the threaded fastener.

[0069] In other embodiments, the first angle ranges from 15° to 35°, and the preferred first angle is 30°.

[0070] The value range of the second angle is 0.5° to 2°, and the preferred second angle is 1°;

[0071] The process of collecting the dynamic friction torque when rotation occurs is as follows:

[0072] Torque data is collected in real time during the process of rotating the threaded fastener at a second angle along the tightening direction, and a torque-time curve is produced according to the torque data and time. The torque data when the torque-time curve reaches a first peak is the static friction torque, and the torque data of the first valley value after the torque-time curve reaches the first peak is the dynamic friction torque.

[0073] Applied torque T T,rot It does not appear at the moment when the tightening angle is applied, but there is a process of transformation from static friction to dynamic friction. Figure 3 The local method curve of this instantaneous torque change is shown. As the turning angle gradually increases, the applied torque reaches T T,rot,st At this time, the torque overcomes the static friction, and the internal and external threads slip relative to each other. When the static friction turns into dynamic friction, the applied torque will drop to T synchronously due to the decrease in the friction coefficient. T,rot,dy , and then as the angle and preload increase, the torque gradually increases. The torque value T at the moment of dynamic friction conversion T,rot,dy Determined as installation torque T T is the most reasonable method.

[0074] Therefore, the installation torque T T The data determination method is as follows: when the tightening angle is applied, the torque curve is collected in real time. The torque time curve is initially in an ascending state, and the peak value is the static friction torque T T,rot,st , and then turns into a descending state, and the valley value is the dynamic friction torque T T,rot,dy , and then the second transition to the rising state, take T T =T T,rot,dy .(like Figure 3 (shown)

[0075] like Figure 2 As shown in the figure, for bolts with short working time, the residual torque value in the tightening direction of the screw is usually equal to the tightening limit value. At this time, tightening a small angle value can make the thread continue to rotate, such as Figure 2As shown in the three figures on the left, the preload increases during the application of the angle, indicating that the internal and external threads have completely slipped, that is, the threads rotate (such as Figure 2 At this time, since the residual torque value is consistent with the tightening limit value, the torque changes when the angle is continued to be applied, and it is not monotonically increasing (such as Figure 2 left middle image);

[0076] The residual torque value of bolts with long working time will decrease to varying degrees. At this time, tightening a small angle value will only accumulate residual torque inside the screw and will not cause the thread to rotate. Figure 2 As shown in the three figures on the right, the preload does not increase during the corner application process (such as Figure 2 The upper right figure shows that the internal and external threads do not rotate relative to each other, and because the residual torque value is lower than the tightening limit value, the torque will increase monotonically with the rotation angle (such as Figure 2 Middle side upper picture), Figure 2 The origin in the lower middle figure indicates the angle application point. When testing the installation torque of a batch of bolts, first test their service time. Different testing methods are used for bolts with different service times to improve the testing efficiency.

[0077] Compared with the traditional testing scheme, the method of loosening first and then tightening is adopted to ensure that the internal and external threads of the threaded fastener are in a state of relative slip when the threaded fastener is rotated at the second angle, thereby ensuring the accuracy of the test results.

[0078] Embodiment 2:

[0079] An electronic device comprises a processor and a memory which is communicatively connected to the processor and is used to store instructions executable by the processor, wherein the processor is used to execute the method described in the first embodiment above.

[0080] Embodiment three:

[0081] A server includes at least one processor and a memory communicatively connected to the processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the processor so that the at least one processor executes the method described in Example 1.

[0082] Embodiment 4:

[0083] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described in embodiment 1 is implemented.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for testing the installation torque of an in-service threaded fastener, characterized in that: The following steps are involved: S1, rotating the threaded fastener at a first angle in a loosening direction, causing the internal threads and external threads in the threaded engagement area of ​​the threaded fastener to slip, and rotating the threaded fastener at a first angle in a tightening direction; S2. Rotate the threaded fastener at a second angle along the tightening direction, and collect the dynamic friction torque during the rotation as the installation torque of the threaded fastener.

2. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: Also includes: S3. Rotate the threaded fastener at a second angle in a loosening direction.

3. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: The first angle is not less than the critical angle of loosening of the threaded fastener; The formula for calculating the critical angle of loosening of threaded fasteners is as follows: Where l is the clamping length, I P is the polar moment of inertia of the screw, G is the shear modulus of the screw material, T T is the design installation torque, T l To loosen the torque.

4. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: The calculation formula for the first angle is as follows: Among them, θ loose is the first angle, a is the calculation coefficient, l is the clamping length, and d is the diameter of the threaded fastener.

5. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: The value range of the first angle is 15° to 35°.

6. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: The value range of the second angle is 0.5° to 2°; The process of collecting the dynamic friction torque when rotation occurs is as follows: Torque data is collected in real time during the process of rotating the threaded fastener at a second angle along the tightening direction, and a torque-time curve is produced according to the torque data and time. The torque data when the torque-time curve reaches a first peak is the static friction torque, and the torque data of the first valley value after the torque-time curve reaches the first peak is the dynamic friction torque.

7. A method for testing the installation torque of an in-service threaded fastener according to claim 1, characterized in that: Determine the working time of the threaded fastener before S1; If the working time of the threaded fastener is short, proceed to step S2; If the working time of the threaded fastener is long, proceed to step S1; The method for determining the working time of a threaded fastener comprises the following steps: Rotate the threaded fastener in the tightening direction, collect the torque and preload, and if the preload increases with the rotation angle and the torque and rotation angle change nonlinearly, it is determined that the working time of the threaded fastener is short.

8. An electronic device, comprising a processor and a memory connected to the processor for storing instructions executable by the processor, characterized in that: The processor is used to execute the method described in any one of claims 1 to 7.

9. A server, characterized in that: It includes at least one processor and a memory communicatively connected to the processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the processor so that the at least one processor executes the method according to any one of claims 1-7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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