Bolt torque coefficient measuring device and measuring method

Abstract

The present invention discloses a bolt torque coefficient measuring device and a measuring method thereof, comprising a stretching machine, a pair of lower clamp heads located on the base of the stretching machine, an upper clamp frame located in the middle of the stretching machine, an upper clamp head located on the upper clamp frame, a box located on the base of the stretching machine, and an upper pressure plate arranged above the top panel of the box through a support column, the bolt to be measured passes through the top plate of the box, an axial force sensor, an upper pressure plate and a nut in sequence upwards and is connected to the upper clamp head, the first bolt and the second bolt pass through the upper pressure plate and the box in sequence downwards and are connected to the lower clamp head, a static torque sensor coaxial with the bolt to be measured is arranged in the box, and a sleeve is connected between the static torque sensor and the bolt to be measured. The present invention obtains accurate preload through the axial force sensor, obtains torque value through the static torque sensor, and then makes the head of the bolt to be measured and the static torque sensor move coaxially through the sleeve, thereby avoiding measurement errors and ensuring the acquisition of high-precision tightening torque values.

Description

Technical Field

[0001] The invention relates to the field of bolt performance measurement, and in particular to a bolt torque coefficient measuring device and a measuring method thereof. Background Art

[0002] Bolt connections are widely used in engineering fields such as rails, pressure vessels, wind turbines, flange pipelines, and bridges. The reliability of bolt connections is related to the safety of engineering structures. In China, most bolts are tightened by applying preload. If the preload is too large, the connected parts will be crushed and the thread teeth will slip. If the preload is too small, the connected parts will loosen, reducing the fatigue life of the bolts. The bolt preload is generally indirectly controlled by the tightening torque. The relationship between the bolt preload and the tightening torque is expressed by K. According to the formula T = F × K × D, K is the torque coefficient, F is the preload, T is the tightening torque, and D is the bolt diameter. In order to ensure the accurate application of the preload, the torque coefficient K must be accurate. However, K is a comprehensive coefficient with a large range of variation, and it is difficult to obtain an accurate value. Therefore, the accurate acquisition of the torque coefficient is of great significance to the safety of engineering structures.

[0003] According to relevant theories, if the bolt size is certain, the connected structure, bolt size and surface properties are the same, and it is assumed that under different loads, the proportion of contact stress distribution of the thread and the supporting surface is the same, then the torque coefficient is a constant. In general, the torque coefficient is calculated by the empirical formula T = F × K × D. It can be seen from the formula that obtaining an accurate torque coefficient depends on the preload and the tightening torque. At present, the preload can be directly obtained according to Hooke's law through the nut angle method, but this method has measurement errors. The preload is indirectly obtained by sticking a resistance strain gauge on the bolt. Although this method has high accuracy, the experimental cycle is long and the operation is cumbersome. The tightening torque is obtained by a high-precision torque wrench, but there are human errors, which makes the measured value have certain limitations. At present, there are problems such as inaccuracy and cumbersomeness in obtaining the torque coefficient.

[0004] Therefore, it is urgent to solve the above problems. Summary of the invention

[0005] Purpose of the invention: The first purpose of the present invention is to provide a bolt torque coefficient measuring device, which can solve the problem that the torque coefficient is difficult to accurately obtain due to inaccurate tightening torque and pre-tightening force.

[0006] A second object of the present invention is to provide a method for measuring a bolt torque coefficient measuring device.

[0007] Technical solution: To achieve the above objectives, the present invention discloses a bolt torque coefficient measuring device, comprising a stretching machine, a pair of lower clamp heads located on the base of the stretching machine, an upper clamp frame located in the middle of the stretching machine, an upper clamp head located on the upper clamp frame, a box located on the base of the stretching machine, and an upper pressure plate arranged above the top panel of the box through a support column. The bolt to be measured passes through the top plate of the box, an axial force sensor, an upper pressure plate and a nut in sequence upward and is connected to the upper clamp head. The first bolt and the second bolt pass through the upper pressure plate and the box in sequence downward and are connected to the lower clamp head. A static torque sensor coaxial with the bolt to be measured is arranged in the box, and a sleeve is connected between the static torque sensor and the bolt to be measured.

[0008] Wherein, the nut outer sleeve is provided with a nut sleeve with a cylindrical handle.

[0009] Preferably, a pair of clamping and fixing plates for clamping the nut sleeve are arranged on the upper pressing plate, waist-shaped holes are opened on the clamping and fixing plates, and the third limiting bolts pass through the waist-shaped holes to be fixedly connected with the upper pressing plate.

[0010] Furthermore, the box body includes a top plate, a bottom plate, a middle partition, two side plates and a back plate. The lower clamp head extends into the box body through the bottom plate. The first bolt and the second bolt pass through the upper pressure plate, the top plate and the middle partition in sequence downward to be connected to the lower clamp head.

[0011] Furthermore, a support platform is provided in the box body, an upper panel of the support platform is in contact with the lower surface of the top plate, and a lower panel of the support platform is fixedly connected with the middle partition plate by a second limiting bolt.

[0012] Preferably, the static torque sensor is fixedly connected to the lower panel of the support platform through a first limiting bolt.

[0013] Furthermore, the support column is a foam support column.

[0014] Furthermore, the measuring range of the axial force sensor is 0 to 180 kN.

[0015] Preferably, the measuring range of the static torque sensor is 300 to 800 N.m.

[0016] A method for measuring a bolt torque coefficient measuring device of the present invention comprises the following steps:

[0017] Fix the box on the base of the stretching machine, place the upper pressure plate on the top plate of the box and align it, and put four support columns between the upper pressure plate and the top of the box;

[0018] Place the axial force sensor between the upper pressure plate and the top plate of the box, and insert the bolt to be tested upward through the bolt holes of the top plate of the box, the axial force sensor, and the bolt holes of the upper pressure plate.

[0019] Put the nut into the bolt to be tested and gently screw it to the surface of the upper pressure plate, which is now in a stressed state;

[0020] Pass the first bolt and the second bolt downward through the bolt holes of the upper pressing plate, the top plate and the middle partition plate, and tighten them with the two lower clamp heads of the tensile machine base;

[0021] Tighten the bolt to be tested and the clamp head on the tensile machine;

[0022] Start the tensioning machine and stretch the bolt to be tested to the specified tension and then stop;

[0023] The bolt to be tested is stretched and deformed by the stretching machine, and the nut moves upward accordingly. The cylindrical handle is inserted into the nut sleeve, and the nut sleeve is driven by the cylindrical handle to tighten the nut to the surface of the upper pressure plate;

[0024] Move the upper fixture frame, and the value of the axial force sensor recorded at this time is the preload force F of the bolt to be tested;

[0025] Place the clamping plate on the surface of the upper pressing plate, fix and clamp the nut sleeve through the third limiting bolt, and at the same time, the waist-shaped groove on the clamping plate can adjust the clamping distance of the nut sleeve;

[0026] Gently push the sleeve in the loosening direction;

[0027] Stop rotation at the moment of loosening, record the torque value T of the static torque sensor, and use the sleeve to make the head of the bolt to be tested and the static torque sensor move coaxially. According to the calculation formula T=F×K×D, where D is the diameter of the bolt to be tested, calculate the torque coefficient K.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0029] (1) The present invention obtains accurate preload force through an axial force sensor, obtains accurate torque value through a static torque sensor, and then uses a sleeve to make the head of the bolt to be measured and the static torque sensor move coaxially, thereby avoiding measurement errors and ensuring the acquisition of high-precision tightening torque value, thereby obtaining an accurate torque coefficient and ensuring that the measured torque coefficient has high accuracy;

[0030] (2) The measurement method of the present invention makes the acquisition of torque coefficient simpler, more convenient, safer and more reliable;

[0031] (3) The present invention uses a universal stretching machine to provide axial tension, so that the obtained pre-tightening force is free of torsional shear force and lateral force, thereby improving the pre-tightening force accuracy of the bolt;

[0032] (4) The box design of the present invention facilitates the movement of the measuring device, and at the same time has a simple structure, convenient operation, high repeatability and low manufacturing cost. By replacing the thread specifications of the upper and lower clamp heads of the stretching machine and the bolt holes of the pressure plate, the torque coefficient of different bolts can be tested, which increases the scope of use and greatly reduces the difficulty of measuring the torque coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0034] Figure 2 It is a structural schematic diagram of the box body in the present invention;

[0035] Figure 3 It is a top view of the box body in the present invention;

[0036] Figure 4 It is a structural schematic diagram of the upper pressing plate in the present invention;

[0037] Figure 5 It is a structural schematic diagram of the support platform in the present invention;

[0038] Figure 6 It is a schematic diagram of the structure of the clamping and fixing plate in the present invention;

[0039] Figure 7 It is a structural schematic diagram of the static torque sensor in the present invention;

[0040] Figure 8 It is a schematic diagram of the structure of the sleeve in the present invention. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0042] like Figure 1 As shown, the present invention discloses a bolt torque coefficient measuring device, including a stretching machine 1, an upper fixture frame 2, an upper fixture head 3, an upper pressure plate 4, an axial force sensor 5, a sleeve 6, a box body 7, a support platform 8, a lower fixture head 9, a stretching machine base 10, a first bolt 11, a bolt to be measured 12, a second bolt 13, a support column 14, a static torque sensor 15, a first limit bolt 16, a second limit bolt 17, a third limit bolt 18, a clamping fixing plate 19, a nut sleeve 20, a nut 21 and a cylindrical handle 22.

[0043] A pair of lower clamp heads 9 are located on the base 10 of the stretching machine. The lower clamp heads have threaded holes, and the upper clamp heads have threads. The threaded hole specifications are both M20×2.5. The upper clamp frame 2 is located in the middle of the stretching machine. The upper clamp frame 2 is detachably connected to the stretching machine 1, and the upper clamp head 3 is arranged on the upper clamp frame 2. The box body 7 is located on the base 10 of the stretching machine. The box body 7 includes a top plate, a bottom plate, a middle partition, two side plates and a back plate. The lower clamp head 9 extends into the box body through the bottom plate. The lower clamp head 9 and the upper clamp head 3 are both provided with internal threads. The upper pressure plate 4 is arranged above the top panel of the box body through a support column 14. The support column 14 is a foam support column. The four support columns 14 are fixed at the four corners, which play a supporting and stabilizing role and do not affect the compression of the upper pressure plate 4. A support platform 8 is arranged in the box body 7. The upper panel of the support platform 8 is in contact with the lower surface of the top plate, and the lower panel of the support platform 8 is fixedly connected to the middle partition through a second limiting bolt 17. The static torque sensor 15 is fixedly connected to the lower panel of the support platform 8 through the first limiting bolt 16. The static torque sensor 15 is coaxially arranged with the bolt 12 to be tested, and a sleeve 6 is connected between the static torque sensor 15 and the bolt 12 to be tested. The measuring range of the static torque sensor 15 is 300-800 N.m.

[0044] The bolt 12 to be tested passes through the top plate of the box 7, the axial force sensor 5, the upper pressure plate 4 and the nut 21 upwards and is connected to the upper fixture head 3. The measuring range of the axial force sensor 5 is 0-180 kN. The first bolt 11 and the second bolt 13 pass through the upper pressure plate, the top plate and the middle partition downwards and are connected to the lower fixture head 9.

[0045] A nut sleeve 20 with a cylindrical handle 22 is provided on the outer sleeve of the nut 21, and a pair of clamping plates 19 for clamping the nut sleeve 20 are provided on the upper pressure plate 4. A waist-shaped hole is opened on the clamping plate 19, and the third limiting bolt 18 passes through the waist-shaped hole and is fixedly connected to the upper pressure plate 4.

[0046] A method for measuring a bolt torque coefficient measuring device of the present invention comprises the following steps:

[0047] Fix the box 7 on the stretching machine base 10, place the upper pressure plate 4 on the top plate of the box 7 and align them, and put four support columns 14 between the upper pressure plate 4 and the top of the box 7;

[0048] Place the axial force sensor 5 between the upper pressing plate 4 and the top plate of the box body 7, and pass the bolt 12 to be tested upward through the bolt hole of the top plate of the box body 7, the bolt hole of the axial force sensor 5 and the bolt hole of the upper pressing plate 4;

[0049] Insert the nut 21 into the bolt 12 to be tested and gently screw it to the surface of the upper pressure plate 4, which is now in a stressed state;

[0050] Pass the first bolt 11 and the second bolt 13 downward through the bolt holes of the upper pressing plate 4, the top plate and the middle partition plate, and tighten them with the two lower clamp heads 9 of the stretching machine base 10;

[0051] Tighten the bolt 12 to be tested and the upper fixture head 3 of the tensile machine 1;

[0052] Start the stretching machine 1, stretch the bolt 12 to be tested to a specified tension and then stop;

[0053] The bolt 12 to be tested is stretched and deformed by the stretching machine 1, and the nut 21 moves upward accordingly. The cylindrical handle 22 is inserted into the nut sleeve 20, and the nut sleeve 20 is driven by the cylindrical handle 22 to tighten the nut 21 to the surface of the upper pressing plate 4;

[0054] Move the fixture frame 2, and the value recorded by the axial force sensor 5 at this time is the preload force F of the bolt 12 to be tested;

[0055] The clamping plate 19 is placed on the surface of the upper pressing plate 4, and the nut sleeve 20 is fixed and clamped by the third limiting bolt 18. Meanwhile, the waist-shaped groove on the clamping plate 19 can adjust the clamping distance of the nut sleeve 20;

[0056] Gently push the sleeve 6 in the loosening direction;

[0057] Stop rotating at the moment of loosening, record the torque value T of the static torque sensor 15, and use the sleeve 6 to make the head of the bolt 12 to be measured and the static torque sensor 15 move coaxially to avoid measurement errors. According to the calculation formula T=F×K×D, where D is the diameter of the bolt 12 to be measured, calculate the torque coefficient K.

[0058] The present invention provides axial tension with the help of a universal stretching machine, so that the obtained pre-tightening force is free of torsional shear force and lateral force, thereby improving the pre-tightening force accuracy of the bolt, and the box design facilitates the movement of the measuring device; the bolt head and the static torque sensor are rotated coaxially by using a sleeve, thereby ensuring the acquisition of a high-precision tightening torque value, thereby calculating an accurate torque coefficient K according to an empirical formula. The present invention ensures that the measured torque coefficient has a high degree of accuracy, and the device of the present invention has a simple structure, convenient operation, high repeatability, and low manufacturing cost; by replacing the thread specifications of the upper and lower clamp heads of the stretching machine and the bolt holes of the pressure plate, the torque coefficient of different bolts can be detected, thereby increasing the scope of use and greatly reducing the difficulty of measuring the torque coefficient.

[0059] The preferred implementation modes of the present invention are described in detail above, but the design concept of the present invention is not limited thereto. Within the technical concept of the present invention, various equivalent transformations can be made to the technical scheme of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A bolt torque coefficient measuring device, characterized in that: The invention comprises a stretching machine (1), a pair of lower clamp heads (9) located on a stretching machine base (10), an upper clamp frame (2) located in the middle of the stretching machine, an upper clamp head (3) located on the upper clamp frame, a box body (7) located on the stretching machine base, and an upper pressure plate (4) arranged above the top panel of the box body through a support column (14); a bolt (12) to be tested passes through the top panel of the box body (7), an axial force sensor (5), the upper pressure plate (4) and a nut (21) in sequence upwards to be connected to the upper clamp head (3); a first bolt (11) and a second bolt (13) pass through the upper pressure plate (4) and the box body (7) in sequence downwards to be connected to the lower clamp head (9); a static torque sensor (15) coaxial with the bolt (12) to be tested is arranged in the box body (7); a sleeve (6) is connected between the static torque sensor (15) and the bolt (12) to be tested; and a sleeve (6) is arranged on the outer sleeve of the nut (21) with a cylindrical handle ( 22) of the nut sleeve (20), the upper pressure plate (4) is provided with a pair of clamping plates (19) for clamping the nut sleeve (20), the clamping plates (19) are provided with waist-shaped holes, and are fixedly connected to the upper pressure plate (4) by passing through the waist-shaped holes through the third limiting bolts (18); the box body (7) comprises a top plate, a bottom plate, a middle partition plate, two side plates and a back plate, the lower clamp head (9) passes through the bottom plate and extends into the box body, the first bolt (11) and the second bolt (13) pass through the upper pressure plate, the top plate and the middle partition plate in sequence downward and are connected to the lower clamp head (9), a support platform (8) is provided in the box body (7), the upper panel of the support platform (8) is in contact with the lower surface of the top plate, the lower panel of the support platform (8) is fixedly connected to the middle partition plate through the second limiting bolts (17), and the static torque sensor (15) is fixedly connected to the lower panel of the support platform (8) through the first limiting bolts (16).

2. The bolt torque coefficient measuring device according to claim 1, characterized in that: The support column (14) is a foam support column.

3. The bolt torque coefficient measuring device according to claim 1, characterized in that: The measuring range of the axial force sensor (5) is 0 to 180 kN.

4. The bolt torque coefficient measuring device according to claim 1, characterized in that: The static torque sensor (15) has a measuring range of 300 to 800 N.m.

5. A method for measuring a bolt torque coefficient measuring device according to any one of claims 1 to 4, characterized in that: The steps include: Fix the box on the base of the stretching machine, place the upper pressure plate on the top plate of the box and align it, and put four support columns between the upper pressure plate and the top of the box; Place the axial force sensor between the upper pressure plate and the top plate of the box, and insert the bolt to be tested upward through the bolt hole of the top plate of the box, the axial force sensor, and the bolt hole of the upper pressure plate. Put the nut into the bolt to be tested and gently screw it to the surface of the upper pressure plate, which is now in a stressed state; Pass the first bolt and the second bolt downward through the bolt holes of the upper pressing plate, the top plate and the middle partition plate, and tighten them with the two lower clamp heads of the tensile machine base; Tighten the bolt to be tested and the clamp head on the tensile machine; Start the tensioning machine and stretch the bolt to be tested to the specified tension and then stop; The bolt to be tested is stretched and deformed by the stretching machine, and the nut moves upward accordingly. The cylindrical handle is inserted into the nut sleeve, and the nut sleeve is driven by the cylindrical handle to tighten the nut to the surface of the upper pressure plate; Move the upper fixture frame, and the value of the axial force sensor recorded at this time is the preload force F of the bolt to be tested; Place the clamping plate on the surface of the upper pressing plate, fix and clamp the nut sleeve through the third limiting bolt, and at the same time, the waist-shaped groove on the clamping plate can adjust the clamping distance of the nut sleeve; Gently push the sleeve in the loosening direction; Stop rotation at the moment of loosening, record the torque value T of the static torque sensor, and use the sleeve to make the head of the bolt to be tested and the static torque sensor move coaxially. According to the calculation formula T=F×K×D, where D is the diameter of the bolt to be tested, calculate the torque coefficient K.

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