阅读说明：本技术 一种测试螺纹紧固件预紧力与扭矩关系的方法 (Method for testing relation between pretightening force and torque of threaded fastener ) 是由 张栋 杨锋 张德华 任燕宏 焦春 于 2021-08-17 设计创作，主要内容包括：本发明涉及一种测试螺纹紧固件预紧力与扭矩关系的方法,具体是指通过加载试验实时检测并记录螺纹紧固件所受扭矩及拉力值,再通过数据处理得到螺纹紧固件预紧力与扭矩关系的方法。本发明通过建立用于测试螺纹紧固件预紧力与扭矩关系的试验装置进行螺纹紧固件预紧力与扭矩关系的试验,试验过程完全模拟螺纹紧固件工作时的扭矩加载过程,试验数据结果更贴近实际使用状况,对实际使用指导性更强。无需在被试螺纹紧固件上打孔穿线即可检测螺纹紧固件受力时的应变值,不改变被试螺纹紧固件受力情况,测试状态与实际使用状态完全一致,测试结果更准确可靠。(The invention relates to a method for testing the relation between the pretightening force and the torque of a threaded fastener, in particular to a method for detecting and recording the torque and the tension value of the threaded fastener in real time through a loading test and obtaining the relation between the pretightening force and the torque of the threaded fastener through data processing. The invention carries out the test of the relationship between the pretightening force and the torque of the threaded fastener by establishing the test device for testing the relationship between the pretightening force and the torque of the threaded fastener, the test process completely simulates the torque loading process of the threaded fastener during working, the test data result is closer to the actual use condition, and the instructive performance to the actual use is stronger. The strain value of the stressed threaded fastener can be detected without punching and threading on the tested threaded fastener, the stress condition of the tested threaded fastener is not changed, the testing state is completely consistent with the actual using state, and the testing result is more accurate and reliable.)

1. A method for testing the relationship between the pretightening force and the torque of a threaded fastener is characterized by comprising the following steps: the method comprises the following steps: s1, establishing a test device for testing the relationship between the pretightening force and the torque of the threaded fastener, wherein the device comprises a base plate (1), an insert (2), a pressing plate (3), an adapter (4), a bracket (5), an adapter disc (6), a torque sensor (7), a wrench (8), a bearing (9), a force sensor (11), an anti-rotation pin (12), a data measurement and acquisition system and a data processing system; a threaded hole is drilled in the bottom plate (1), an external thread is arranged on the outer wall of the insert (2), a through hole is formed in the center of the insert (2), an internal thread used for connecting a tested threaded fastener is arranged in the through hole, a through hole is formed in the center of the force sensor (11), the width of the pressing plate (3) is smaller than the diameter of the central through hole of the force sensor (11), and a through hole is formed in the center of the pressing plate (3); the bracket (5) is erected above the pressure plate (3), and the bracket (5) is provided with a through hole for mounting a bearing (9); a switching disc (6) is inserted into a hole of the bearing (9), a polygonal square hole is formed in the lower portion of the switching disc (6), and a polygonal square head matched with the polygonal square hole is arranged on the upper portion of the switching head (4) and is matched with the polygonal square hole to transmit torque; a polygonal hole is formed in the upper part of the torque sensor (7) and is matched with a polygonal head on the wrench (8) to transmit torque; signal wires of the force sensor (11) and the torque sensor (7) are connected into a data acquisition and measurement system;

s2, calculating a maximum pretightening force test value and a maximum fastening torque value according to the following formula according to the material and specification of the tested threaded fastener:

F ₀ ＝ασ _s A _s

T＝KF ₀ d

in the formula:

F ₀ the unit N of pre-tension

αThe pre-tightening force test coefficient is selected according to the actual use condition

σ _s The yield strength of the screw material at the temperature of use, in MPa

A _s Screw nominal stress cross-sectional area in mm²

TFastening torque in units Nm

KTorque coefficient selected according to friction surface condition and lubrication

d-nominal thread diameter in mm;

s3, selecting a force sensor and a torque sensor with proper measuring ranges according to the maximum pretightening force test value and the maximum fastening torque value obtained through calculation;

s4, fixing the bottom plate (1) of the testing device on a stable base body to ensure that the bottom plate (1) is stable and does not move in the process of testing the threaded fastener;

s5, screwing the insert (2) into the corresponding threaded hole of the base plate (1), and inserting the anti-rotation pin (12) to prevent the insert (2) from rotating in the use process;

s6, placing the force sensor (11) on the upper plane of the base plate (1), wherein the central through hole of the force sensor (11) is opposite to the position of the insert (2);

s7, sleeving the pressure plate (3) on the tested threaded fastener, and screwing the tested threaded fastener into the thread of the insert (2) to ensure that the threaded fastener, the pressure plate (3) and the force sensor (11) are exactly contacted with each other pairwise, but do not apply further torque to the tested threaded fastener;

s8, inserting or sleeving a tested threaded fastener with an adapter (4) matched with the threaded fastener in shape and size, and then sequentially placing a support (5), an adapter disc (6) and a torque sensor (7), wherein the adapter disc (6) is connected with the adapter (4);

s9, connecting the force sensor (11) and the torque sensor (7) to a data measurement and acquisition system respectively, and resetting the measurement values of the force sensor (11) and the torque sensor (7) in the data measurement and acquisition system;

s10, opening a data measurement and acquisition system and starting to measure and acquire data; a wrench (8) is used for screwing and loading a tested threaded fastener, meanwhile, a data measurement and acquisition system measures and acquires the measured value of a force sensor (11), namely a pre-tightening force measured value and the measured value of a torque sensor (7), and the data acquisition interval is set according to the requirement;

s11, when the measured value of the force sensor (11) reaches and just exceeds the calculated maximum pretightening force test value, stopping loading the tested threaded fastener, and simultaneously rotating the wrench (8) in the opposite direction to unload the tested threaded fastener;

and S12, importing a series of measured values of the force sensor and the torque sensor obtained by measurement into a data processing system, and obtaining a relation table, a relation chart and related parameters of the pretightening force and the torque of the tested threaded fastener after fitting processing.

2. The method for testing the relationship between the pretightening force and the torque of the threaded fastener as claimed in claim 1, further comprising step S13 of adhering a strain gauge to the unthreaded section of the outer wall of the threaded fastener to be tested, wherein the connecting wire of the strain gauge penetrates out of the gap (13) between the pressure plate (3) and the central through hole of the force sensor (11) without punching a hole on the threaded fastener to be tested, and the connecting wire of the strain gauge is connected to a data measurement and acquisition system, so that strain values can be measured and acquired simultaneously during the tightening and loading process of the threaded fastener to be tested, and more data support can be provided for subsequent analysis.

3. A method of testing the preload force versus torque relationship of a threaded fastener as claimed in claim 1 or claim 2 wherein said insert (2) is formed of the same material as the coupling member to be connected to the threaded fastener under test.

4. The method for testing the relation between the pretightening force and the torque of the threaded fastener as claimed in claim 1 or 2, wherein the pretightening force test coefficient is 0.5-0.7; the torque coefficient is 0.1-0.5.

5. The method for testing the pretightening force and torque relationship of the threaded fastener as claimed in claim 1 or 2, wherein the lower part of the adapter plate (6) is provided with a hexagonal hole, and the upper part of the adapter (4) is provided with a hexagonal head matched with the hexagonal hole.

6. A method of testing the preload force versus torque relationship of a threaded fastener as claimed in either of claims 1 and 2 wherein the data acquisition and measurement system is model number DH 5902.

7. A method of testing the preload force versus torque relationship of a threaded fastener as claimed in claim 1 or 2, wherein the pressure plate (3) is long kidney shaped, i.e. a long kidney is formed by cutting out a portion of each side of the circular plate.

8. A method of testing the preload force versus torque relationship of a threaded fastener as claimed in claim 1 or 2, wherein the torque sensor (7) is fixedly connected to the adapter plate (6) by means of screws.

Technical Field

The invention relates to a method for testing the relation between the pretightening force and the torque of a threaded fastener, in particular to a method for detecting and recording the torque and the tension value of the threaded fastener in real time through a loading test and obtaining the relation between the pretightening force and the torque of the threaded fastener through data processing.

Background

In industrial products, a threaded connection structure is widely used as a connecting fastener, and a pre-tightening force is generated by applying a torque to the threaded fastener, so that the parts are connected and fastened. Whether the pre-tightening design of the threaded fastener between the parts is reasonable or not directly influences the connection reliability between the parts, such as connection strength, rigidity, looseness prevention and the like.

The pre-tightening force after threaded connection cannot be directly measured and can only be indirectly obtained by measuring the torque of the threaded fastener in the tightening process, the relation between the torque and the pre-tightening force is usually obtained by calculation through an empirical formula, the relation between the torque and the pre-tightening force is influenced by various factors such as threaded materials, specifications, surface quality, contact surface size, lubrication conditions and the like, the reliability of a calculation result is poor, certain potential safety hazards can be brought to products, the connection and fastening effects cannot be achieved due to too low pre-tightening force, the connection surface can be damaged due to too high pre-tightening force, and even the service life of the threaded fastener is shortened. Thus, for highly demanding threaded connections, it is often desirable to determine the preload force versus torque relationship of the threaded fastener by experimental means.

The conventional method for testing the relationship between the pretightening force and the torque of the threaded fastener is mechanical loading, and the threaded fastener is mostly manually loaded when in use, so that the problem that the loading mode during testing is inconsistent with that during use exists, and the test data has poor instructive performance on actual use; when the existing testing method is used for detecting a strain value of a stressed threaded fastener, punching and threading are needed to be carried out on the tested threaded fastener, so that the stress condition of the tested threaded fastener is changed, and the testing state is inconsistent with the actual using state; the existing testing method has the advantages that the tested piece of the connected piece is a whole, the size is large, when the connected piece to be tested is more in material and specification and expensive, the replacement is inconvenient, the material waste of the connected piece is large, and the testing cost is high.

Disclosure of Invention

The invention aims to design a test method for testing the relation between the pretightening force and the torque of a threaded fastener, and solves the problem that the loading mode during testing is inconsistent with the loading mode during use in the existing test method by carrying out loading test on a tested threaded fastener; the problem that the testing state is inconsistent with the actual using state due to the fact that holes need to be punched when strain values of the threaded fastener are detected when the threaded fastener is stressed; and the technical problems of inconvenient replacement of the connecting piece of the test device, large material waste, high test cost and the like.

The invention is realized by adopting the following technical scheme: a method of testing the relationship between preload and torque of a threaded fastener comprising the steps of: s1, establishing a test device for testing the relationship between the pretightening force and the torque of the threaded fastener, wherein the device comprises a bottom plate, an insert, a pressing plate, an adapter, a support, an adapter plate, a torque sensor, a wrench, a bearing, a force sensor, an anti-rotation pin, a data measurement and acquisition system and a data processing system; a threaded hole is drilled in the bottom plate, external threads are arranged on the outer wall of the insert, a through hole is formed in the center of the insert, and internal threads used for connecting a tested threaded fastener are arranged in the through hole; the center of the force sensor is provided with a through hole, the width of the pressing plate is smaller than the diameter of the through hole at the center of the force sensor, and the center of the pressing plate is provided with a through hole; the bracket is arranged above the pressure plate, and a through hole for mounting a bearing is formed in the bracket; an adapter plate is inserted into a hole of the bearing, a polygonal square hole is formed in the lower portion of the adapter plate, and a polygonal square head matched with the polygonal square hole is arranged on the upper portion of the adapter and matched with the polygonal square hole to transmit torque; the upper part of the torque sensor is provided with a polygonal hole which is matched with a polygonal head on the wrench to transmit torque; signal wires of the force sensor and the torque sensor are connected into a data acquisition and measurement system, and data of the force sensor, the torque sensor and the strain gauge can be acquired in real time during loading;

the device can accurately measure the pretension force and the torque of the tested threaded fastener, particularly can be combined with a subsequent method to carry out reasonable treatment on the tested threaded fastener, and provides technical support for accurately obtaining a measured value;

s2, calculating a maximum pretightening force test value and a maximum fastening torque value according to the following formula according to the material and specification of the tested threaded fastener:

F ₀ ＝ασ _s A _s

T＝KF ₀ d

in the formula:

F ₀ the unit N of pre-tension

αThe pre-tightening force test coefficient is selected according to the actual use condition

σ _s The yield strength of the screw material at the temperature of use, in MPa

A _s Screw nominal stress cross-sectional area in mm²

TFastening torque in units Nm

KTorque coefficient selected according to friction surface condition and lubrication

d-nominal thread diameter in mm;

s3, selecting a force sensor and a torque sensor with proper measuring ranges according to the maximum pretightening force test value and the maximum fastening torque value obtained through calculation;

s4, fixing the bottom plate of the testing device on a stable base body to ensure that the bottom plate is stable and does not move in the process of testing the threaded fastener;

s5, screwing the insert into the corresponding threaded hole of the bottom plate, and inserting an anti-rotation pin to prevent the insert from rotating in the use process;

s6, placing the force sensor on the upper plane of the bottom plate, wherein the central through hole of the force sensor is opposite to the position of the insert;

s7, sleeving the pressure plate on the tested threaded fastener, and screwing the tested threaded fastener into the threads of the insert so that the threaded fastener, the pressure plate and the force sensor are exactly in contact with each other pairwise, but do not apply further torque to the tested threaded fastener;

s8, inserting or sleeving an adapter which is matched with the head of the threaded fastener in shape and size on the tested threaded fastener, and then sequentially placing a bracket, an adapter plate and a torque sensor, wherein the adapter plate is connected with the adapter;

s9, connecting the force sensor and the torque sensor to a data measurement and acquisition system respectively, and clearing the measured values of the force sensor and the torque sensor in the data measurement and acquisition system;

s10, opening a data measurement and acquisition system and starting to measure and acquire data; tightening and loading the tested threaded fastener by using a wrench, simultaneously measuring and collecting force sensor measurement values, namely a pretightening force measurement value and a torque sensor measurement value in real time by using a data measurement and collection system, and setting data collection intervals as required;

s11, when the measured value of the force sensor reaches and just exceeds the calculated maximum pretightening force test value, stopping loading the tested threaded fastener, and simultaneously rotating the wrench in the opposite direction to unload the tested threaded fastener;

and S12, importing a series of measured values of the force sensor and the torque sensor obtained by measurement into a data processing system, and obtaining a relation table, a relation chart and related parameters of the pretightening force and the torque of the tested threaded fastener after fitting processing.

Further, the method comprises the step S13 of pasting the strain gauge on the unthreaded section of the outer wall of the tested threaded fastener, enabling the connecting line of the strain gauge to penetrate out of the gap between the pressure plate and the central through hole of the force sensor without punching on the tested threaded fastener, connecting the connecting line of the strain gauge to a data measurement and acquisition system, and measuring and acquiring strain values simultaneously in the tightening and loading process of the tested threaded fastener to provide richer data support for subsequent analysis.

Further, the insert is made of the same material as the coupling member to be connected to the screw fastener to be tested.

Further, the pre-tightening force test coefficient is 0.5-0.7; the torque coefficient is 0.1-0.5.

Compared with the traditional test method, the method has the advantages that:

(1) the testing device for testing the relation between the pretightening force and the torque of the threaded fastener is used for testing the relation between the pretightening force and the torque of the threaded fastener, the torque loading process of the threaded fastener during working is completely simulated in the testing process, the testing data result is closer to the actual use condition, and the practical use instruction is stronger.

(2) The strain value of the stressed threaded fastener can be detected without punching and threading on the tested threaded fastener, the stress condition of the tested threaded fastener is not changed, the testing state is completely consistent with the actual using state, and the testing result is more accurate and reliable.

(3) The insert is made of the material of the connected piece, the insert is small in size and can be conveniently detached, the material of the connected piece is saved, the purpose of testing threaded fasteners of different materials and different specifications can be achieved by changing the insert so that the pre-tightening force testing device of the threaded fasteners, the material usage amount of the connected piece is reduced, the testing cost is greatly reduced, and the universality of the testing device is stronger.

Drawings

FIG. 1 is a front view of a device for testing the pretension of a threaded fastener.

FIG. 2 is a top view of a threaded fastener pretension testing apparatus.

FIG. 3 is a schematic diagram of the gap between the pressure plate and the center through hole of the force sensor.

FIG. 4 is a graph illustrating pretension-torque relationship according to the embodiment.

In the figure:

1-bottom plate, 2-insert, 3-clamp plate, 4-adapter, 5-support, 6-switching dish, 7-torque sensor, 8-spanner, 9-bearing, 10-screw, 11-force sensor, 12-anti-rotation pin, 13-space.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

A certain M10 x 1.5 external hex head screw (screw 10 tested) is known. The method of the invention is used for testing the relationship between the pretightening force and the torque when the screw and the specified material are connected by the connecting piece, and comprises the following steps:

s1, establishing a testing device (figures 1-3) for testing the relationship between the pretightening force and the torque of the threaded fastener, comprising a base plate 1, a threaded hole drilled on the base plate 1, an insert 2 embedded in the threaded hole, and an anti-rotation pin 12 inserted between the base plate 1 and the insert 2 to prevent the insert 2 from rotating in the using process. The outer wall of the insert 2 is provided with an external thread, the center of the insert 2 is provided with a through hole, an internal thread used for connecting a tested screw 10 is arranged in the through hole, a force sensor 11 is placed right above the insert 2, and the central through hole of the force sensor 11 is aligned with the insert 2. The pressing plate 3 is placed on the upper surface of the force sensor 11, the pressing plate 3 is long waist-shaped (a part is respectively cut off from two circular sides), the width of the pressing plate 3 is smaller than the diameter of a central through hole of the force sensor 11, and the center of the pressing plate 3 is provided with the through hole. A support 5 is erected above the pressing plate 3, a through hole is formed in the support 5, and a bearing 9 is installed in the through hole. The switching disk 6 is inserted into the hole of the bearing 9, the lower part of the switching disk 6 is provided with a hexagonal hole (three-square, four-square, five-square, eight-square holes and the like can also be adopted), and the six-square head (three-square, four-square, five-square, eight-square and the like can also be adopted) at the upper part of the lower switching head 4 is matched with the transmission torque. The torque sensor 7 is mounted above the adapter plate 6 through screws, and a polygonal hole is formed in the upper portion of the torque sensor 7 and matched with a polygonal head on the wrench 8 to transmit torque. The signal lines of the force sensor 11, the torque sensor 7, the strain gauge and the like are connected to a data acquisition system, and the data of the force sensor 11, the torque sensor 7 and the strain gauge can be acquired in real time during loading. When in use, the DH5902 type data acquisition system and the computer data processing system are simultaneously equipped.

S2, calculating a maximum pretightening force test value and a maximum fastening torque value according to the material and specification of the tested screw 10 according to the following formula:

F ₀ ＝ασ _s A _s

T＝KF ₀ d

wherein: coefficient of pre-tightening force testαTaking 0.6, the yield strength of the material of the screw 10 to be tested at the service temperature (300 ℃ C.)σ _s 586.1MPa, the nominal 10 of the tested screwCross section area of forceA _s Is 58mm²Coefficient of torqueKTake 0.23, nominal diameter of screw 10 testeddIs 10 mm.

And (3) calculating the result: pretightening forceF ₀ =20.4（kN）

Fastening torqueT=46.9（Nm）

S3, selecting the force sensor 11 with the measuring range of 50kN and the torque sensor 7 with the measuring range of 100Nm according to calculation.

S4, fixing the bottom plate 1 of the threaded fastener pre-tightening force testing device on a stable cement platform, and ensuring that the bottom plate 1 does not move stably in the threaded fastener testing process.

And S5, screwing the insert 2 into the corresponding threaded hole of the base plate 1, and inserting the anti-rotation pin 12.

And S6, placing the force sensor 11 on the upper plane of the base plate 1, wherein the central through hole of the force sensor 11 is opposite to the position of the insert 2.

S7, the pressure plate 3 is sleeved on the tested screw 10, and the tested screw 10 is screwed into the thread of the insert 2, so that the lower plane of the tested screw 10 is exactly contacted with the upper plane of the pressure plate 3, the lower plane of the pressure plate 3 is exactly contacted with the upper plane of the force sensor 11 in pairs, but no further torque is applied to the tested screw 10.

S8, sleeving the tested screw 10 with an adapter 4 matched with the shape and size of the head of the tested screw, and then sequentially placing the bracket 5, the adapter plate 6 and the torque sensor 7 (fixedly connected with the adapter plate 6 into a whole through screws).

And S9, connecting the force sensor 11 and the torque sensor 7 to a DH5902 type data acquisition system respectively, and clearing the measured values of the force sensor 11 and the torque sensor 7 in the DH5902 type data acquisition system.

And S10, opening the DH5902 type data acquisition system and starting to measure the acquired data. The wrench 8 is used for tightening and loading the tested screw 10, and meanwhile, a DH5902 type data acquisition system measures and acquires the measurement value (namely the pretightening force measurement value) of the force sensor 11 and the measurement value of the torque sensor 7 in real time, and the data acquisition interval is set to be 1 second.

And S11, stopping loading the tested screw 10 when the measured value of the force sensor 11 reaches and slightly exceeds the calculated maximum pretightening force test value of 20.4kN, and simultaneously rotating the wrench 8 in the opposite direction to unload the tested screw 10.

S12, importing a series of measured values of the force sensor 11 and the torque sensor 7 into a DH5902 type data acquisition system, and obtaining a relation table (simplified data in the table) of the pretightening force and the torque of the tested screw 10, a relation curve graph (figure 4) and related parameters (linear fitting curve formula: y =1.9609x, and fitting reliability R) through fitting treatment²Value).

S13, pasting a strain gauge on the outer wall of the tested screw 10 without a threaded section, enabling a connecting line of the strain gauge to penetrate out of a gap (figure 3) between the pressure plate 3 and a central through hole of the force sensor 11 without punching the tested screw 10, and connecting the connecting line of the strain gauge to a DH5902 type data acquisition system, so that strain values can be measured and acquired simultaneously in the tightening and loading process of the tested screw 10, and richer data support is provided for subsequent analysis.