CN110715798B - Test device and test method for measuring self-loosening of bolt - Google Patents
Test device and test method for measuring self-loosening of bolt Download PDFInfo
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- CN110715798B CN110715798B CN201910910440.3A CN201910910440A CN110715798B CN 110715798 B CN110715798 B CN 110715798B CN 201910910440 A CN201910910440 A CN 201910910440A CN 110715798 B CN110715798 B CN 110715798B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M13/00—Testing of machine parts
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M7/00—Vibration-testing of structures; Shock-testing of structures
- G01M7/02—Vibration-testing by means of a shake table
Abstract
The invention relates to a test device and a test method for measuring self-loosening of a bolt, and belongs to the technical field of nuclear power equipment anti-seismic test devices. The testing device comprises an external frame, a first clamping plate, a second clamping plate, a pressure sensor, a horizontal spring and a vertical spring; the first clamping plate, the second clamping plate and the connected spring are combined into a flexible clamp; the device is used with the seismic test bed in a matched mode, and the problem that the existing test device cannot realize continuous change of seismic load loading amplitude and frequency or simultaneous loading in multiple directions is solved. The bolts are installed by adopting flexible clamps, and the design of the clamps can simulate the acceleration amplification effect of different positions on the nuclear power equipment according to different response amplification requirements, so that the loosening condition of the bolts at different positions on the nuclear power equipment can be tested. The device and the method can be used for carrying out bolt connection test under earthquake load of nuclear power equipment, and have great significance for the bolt optimization anti-loosening design of the nuclear power equipment.
Description
Technical Field
The invention relates to a test device and a test method for measuring self-loosening of a bolt, and belongs to the technical field of nuclear power equipment anti-seismic tests.
Background
Bolted connections are the most common structural connection forms for nuclear power equipment. Under seismic conditions, "self-loosening" of bolts is one of the most common failure modes of bolts. The self-loosening means that under a certain load condition, the bolt and the nut rotate relatively due to the reduction of self-locking torque, and the pretightening force of the bolt is reduced to enable the bolt to lose normal working performance and even be separated completely. The self-loosening under the earthquake working condition can cause the failures of force and movement failure, sealing leakage and the like of the nuclear power equipment structure, so that the nuclear power equipment can lose normal functions, major accidents are caused, and huge loss is brought.
Whether the bolt can loosen automatically under the earthquake load or not can not be judged by theoretical calculation at present, and the bolt needs to be tested by a test means. Research shows that the loads causing the bolt connection to loosen comprise multidirectional force and moment effects such as transverse loads perpendicular to the axial direction, torque along the axial direction of the bolt, torque perpendicular to the axial direction of the bolt, tensile stress along the axial direction of the bolt and the like. When the applied external load is too large, the stress on the bolt exceeds the material yield strength to generate plastic deformation, and the loosening is possible. This plastic deformation can be either a single large load induced material yield or a cyclic accumulation of material property strain under cyclic loading. The failure mechanism of the bolt connecting structure under the earthquake load is complex and can not be judged through theoretical calculation. In practical engineering, in order to ensure that nuclear safety-level equipment of a nuclear power plant maintains structural integrity under earthquake loads and performs safety-related functions, the nuclear safety-level equipment needs to pass earthquake simulation tests. The existing bolt loosening test device and method cannot simulate the earthquake working condition. The test device for measuring the bolt looseness adopted at present is a transverse vibration test bed of a fastener under the action of a transverse load, for example, the test bed built according to GB/T10431 and 2008 is used for measuring the looseness prevention performance of the fastener under transverse vibration, unidirectional load can be applied only, three axial six-degree-of-freedom load change cannot be realized, the test bed cannot realize continuous change of loading amplitude and frequency, the loading capacity is limited, the loading frequency is low, and the requirement of testing the looseness prevention performance of a connecting bolt under earthquake load cannot be met. In addition, because the rigidity difference of different parts of the equipment is large, the acceleration response of the connecting bolt at the part with poor equipment rigidity under the earthquake working condition is often far beyond the input limit of the table top of the earthquake test bed, and therefore the bolt loosening test cannot be carried out independently. Therefore, a testing device and a testing method capable of testing the self-loosening of the bolt of the nuclear power equipment under the action of the earthquake load under the condition of simulating the earthquake are needed in the technical field.
Disclosure of Invention
The invention aims to solve the technical problem that no proper test device and test method are available at present to test the self-loosening condition of the bolts of the nuclear power equipment under the action of earthquake loads.
In order to solve the problems, the technical scheme adopted by the invention is to provide a test device for measuring the self-loosening of a bolt, which is characterized in that: the clamping device comprises an external frame, a first clamping plate, a second clamping plate, a pressure sensor, a horizontal spring and a vertical spring; the external framework is a cubic steel framework, and six faces of the external framework form six faces of a cube; a first clamping plate and a second clamping plate are arranged in the center of the cube, and the first clamping plate and the second clamping plate are of square plate structures; the first clamping plate and the second clamping plate are connected through bolts, and the surfaces of the first clamping plate and the second clamping plate are parallel to the ground plane; horizontal springs are arranged on the end faces of four squares of the second clamping plate perpendicular to the ground plane, the horizontal springs are connected to four corresponding faces of the external frame, and a vertical spring is arranged in the center of the plate face of the first clamping plate and connected with the top face of the corresponding external frame; the center of the second clamping plate is provided with a vertical spring which is connected with the bottom surface of the corresponding external frame.
Preferably, the first clamping plate and the second clamping plate are provided with bolt holes, and the first clamping plate, the second clamping plate and the connected spring are combined into a flexible clamp.
Preferably, the horizontal spring and the vertical spring change the spring stiffness and the fundamental frequency by changing the spring dimension parameters of the diameter of the spring wire, the pitch and the pitch of the spring.
Preferably, the pressure sensor is connected with the bolt to be detected and then fixed in bolt holes formed in the first clamping plate and the second clamping plate; an acceleration sensor is arranged close to the bolt to be measured.
The invention also provides a test method for measuring the self-loosening of the bolt, which comprises the following steps:
the first step is as follows: setting a proper initial input reaction spectrum IRS-1 of the seismic table top according to the capacity of the seismic table;
the second step is that: calculating a transfer function H between a test target reaction spectrum TRRS and a table initial input reaction spectrum IRS-1 according to the test target reaction spectrum TRRS and the table initial input reaction spectrum IRS-1 of the bolt mounting end face;
the third step: carrying out dynamic simulation calculation, and designing a flexible clamp according to the simulation calculation, wherein a clamp frequency response function corresponds to an envelope transfer function H;
the fourth step: searching a design manual according to a design result of the clamp, selecting an applicable spring, and assembling the clamp and the test device;
the fifth step: and fixing the testing device on the earthquake testing stand, and fixing the bolt on the flexible clamp. The pretightening force between the bolts is given according to design requirements, and is measured through a pressure sensor. An acceleration sensor for control is arranged on the mounting end face of the bolt;
and a sixth step: starting the earthquake table, and finely adjusting the input reaction spectrum IRS-2 of the table top of the earthquake table through 1-2 times of preliminary tests, so that the test reaction spectrum TRS measured by the acceleration sensor on the installation end face of the bolt envelops the test target reaction spectrum TRRS;
the seventh step: and re-pre-tightening the bolt, and measuring the pre-tightening force through the pressure sensor. And the seismic table is input according to the table top input reaction spectrum IRS-2 of the seismic table, and the loosening condition of the bolt under the seismic load input is observed and recorded.
Preferably, the first step of adjusting the rigidity of the flexible clamp is realized by calculating a transfer function H between a reaction spectrum TRRS required by a target test at a bolt mounting end and an input reaction spectrum IRS of a table top of a seismic test bed and adjusting structural parameters of the clamp according to dynamic simulation calculation
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a method and a device for testing the self-loosening condition of a bolt of nuclear power equipment under the action of seismic load, which are matched with a seismic test bed for use and solve the problem that the existing test device cannot realize continuous change of seismic load loading amplitude and frequency or simultaneous multi-direction loading. Meanwhile, in order to simulate the response amplification of equipment at different bolt installation positions under earthquake load, the bolts are installed by adopting flexible clamps, and the design of the clamps is realized by selecting springs with different rigidity and fundamental frequency on the basis of dynamic simulation according to different response amplification requirements. The test device can simulate the acceleration amplification effect of different positions on nuclear power equipment, further can test the loosening condition of bolts at different positions on the nuclear power equipment, and has great significance for the bolt connection test and the anti-loosening optimization design of the nuclear power equipment.
Drawings
FIG. 1 is a schematic diagram of the components of a test apparatus for measuring the self-loosening of a bolt according to the present invention.
Detailed Description
In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings:
as shown in fig. 1, a test device for measuring self-loosening of a bolt comprises an external frame 10, a first clamping plate 1, a second clamping plate 2, a pressure sensor 3, a horizontal spring 4, a horizontal spring 5, a horizontal spring 6, a horizontal spring 7, a vertical spring 8 and a vertical spring 9; the external framework is a cubic steel framework, and six faces of the external framework form six faces of a cube; a first clamping plate 1 and a second clamping plate 2 are arranged in the center of the cube, and the first clamping plate 1 and the second clamping plate 2 are of square plate structures; the first clamping plate 1 and the second clamping plate 2 are connected through a bolt 11, and the surfaces of the first clamping plate 1 and the second clamping plate 2 are parallel to the ground plane; horizontal springs are arranged on the end faces of four squares of the second clamping plate 2 perpendicular to the ground plane, the horizontal springs are connected to four corresponding faces of the external frame, and a vertical spring 8 is arranged in the center of the plate face of the first clamping plate 1 and connected with the top face of the corresponding external frame; the center of the surface of the second clamping plate 2 is provided with a vertical spring 9 which is connected with the bottom surface of the corresponding external frame. Bolt holes are formed in the first clamping plate and the second clamping plate. The first clamping plate and the second clamping plate form a flexible clamp. The bolt 11 is fixed in the bolt holes arranged on the first clamping plate and the second clamping plate after being connected with the pressure sensor 3. The acceleration sensors 12 are arranged next to the bolts 11, one acceleration sensor 12 per bolt.
The tested bolt 11 is fixed on the earthquake test bed through a flexible clamp. The bolt is fixed by the force measuring wrench, so that a certain pretightening force is generated. The connection between the two clamped metal plates is loosened by means of the seismic load generated by the seismic test bed, so that the clamping force is reduced or even completely lost.
According to the scheme, the clamp is a test device for fixing the bolt on the test bench. Due to the fact that the equipment is different in structure and earthquake loads borne by the equipment, the bolt mounting positions on the equipment are different, the mounting modes are different, and earthquake response of the bolt mounting end is changed. The flexible clamp is capable of meeting the changing requirements and generating different seismic responses at the bolt mounting end by adjusting the rigidity of the flexible clamp.
According to the scheme, the self rigidity is adjusted by calculating a transfer function H between a reaction spectrum TRRS required by a target test at a bolt mounting end and an input reaction spectrum IRS of a seismic test bed table board, and adjusting the structural parameters of the clamp according to dynamic simulation calculation.
According to the scheme, the adjusting clamp structure comprises the steps of adjusting spring size parameters such as the diameter of a spring wire, the pitch and the like of a spring, and changing the rigidity and the fundamental frequency of the spring. The earthquake test bed is a hydraulic vibration bed which can simulate complex motion caused by an earthquake and generate three-dimensional six-degree-of-freedom motion.
The invention also provides a test method for measuring the self-loosening of the bolt, and the test method for testing the loosening degree of the bolt under the condition of simulating the earthquake load.
In the simulated seismic test, the test requirement is that the test response spectrum TRS at the installation end of a prototype envelops the test target response spectrum TRRS. In order to simulate the response of different bolt installation positions on equipment, the input reaction spectrum IRS of the earthquake table top and the rigidity of a flexible clamp for installing bolts need to be adjusted before the test, so that the test reaction spectrum TRS at the bolt installation end envelops the test target reaction spectrum TRRS. The test procedure was as follows:
the first step is as follows: setting a proper initial input reaction spectrum IRS-1 of the seismic table top according to the capacity of the seismic table;
the second step is that: calculating a transfer function H between a test target reaction spectrum TRRS of the bolt mounting end face and a table top initial input reaction spectrum IRS-1;
the third step: carrying out dynamic simulation calculation, and designing a flexible clamp according to the simulation calculation, wherein a clamp frequency response function corresponds to an envelope transfer function H;
the fourth step: searching a design manual according to a design result of the clamp, selecting an applicable spring, and assembling the clamp and the test device;
the fifth step: and fixing the testing device on the earthquake testing stand, and fixing the bolt on the flexible clamp. The pretightening force between the bolts is given according to design requirements, and is measured through a pressure sensor. An acceleration sensor for control is arranged on the mounting end face of the bolt;
and a sixth step: starting the earthquake table, and finely adjusting the input reaction spectrum IRS-2 of the table top of the earthquake table through 1-2 times of preliminary tests, so that the test reaction spectrum TRS measured by the acceleration sensor on the installation end face of the bolt envelops the test target reaction spectrum TRRS;
the seventh step: and re-pre-tightening the bolt, and measuring the pre-tightening force through the pressure sensor. And the seismic table is input according to the table top input reaction spectrum IRS-2 of the seismic table, and the loosening condition of the bolt under the seismic load input is observed and recorded.
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Those skilled in the art can make various changes, modifications and equivalent arrangements, which are equivalent to the embodiments of the present invention, without departing from the spirit and scope of the present invention, and which may be made by utilizing the techniques disclosed above; meanwhile, any changes, modifications and variations of the above-described embodiments, which are equivalent to those of the technical spirit of the present invention, are within the scope of the technical solution of the present invention.
Claims (4)
1. The utility model provides a test device that measuring bolt is pine by oneself and takes off which characterized in that: the clamping device comprises an external frame, a first clamping plate, a second clamping plate, a pressure sensor, a horizontal spring and a vertical spring; the external framework is a cubic steel framework, and six faces of the external framework form six faces of a cube; a first clamping plate and a second clamping plate are arranged in the center of the cube, and the first clamping plate and the second clamping plate are of square plate structures; the first clamping plate and the second clamping plate are connected through bolts, and the surfaces of the first clamping plate and the second clamping plate are parallel to the ground plane; horizontal springs are arranged on the end faces of four squares of the second clamping plate perpendicular to the ground plane, the horizontal springs are connected to four corresponding faces of the external frame, and a vertical spring is arranged in the center of the plate face of the first clamping plate and connected with the top face of the corresponding external frame; a vertical spring is arranged in the center of the second clamping plate and connected with the bottom surface of the corresponding external frame; the first clamping plate and the second clamping plate are provided with bolt holes, and the first clamping plate, the second clamping plate and the connected springs are combined into a flexible clamp.
2. The test device for measuring the self-loosening of the bolt according to claim 1, wherein: the horizontal spring and the vertical spring change the spring stiffness and the fundamental frequency by changing the spring size parameters of the diameter of the spring wire, the pitch and the pitch of the spring.
3. The test device for measuring the self-loosening of the bolt according to claim 1, wherein: the pressure sensor is connected with the bolt to be detected and then fixed in bolt holes formed in the first clamping plate and the second clamping plate; an acceleration sensor is arranged close to the bolt to be measured.
4. A test method of a test device for measuring self-release of a bolt according to any one of claims 1 to 3, comprising the steps of:
the first step is as follows: setting a proper initial input reaction spectrum IRS-1 of the seismic table top according to the capacity of the seismic table;
the second step is that: calculating a transfer function H between a test target reaction spectrum TRRS and a table initial input reaction spectrum IRS-1 according to the test target reaction spectrum TRRS and the table initial input reaction spectrum IRS-1 of the bolt mounting end face;
the third step: carrying out dynamic simulation calculation, and designing a flexible clamp according to the simulation calculation, wherein a clamp frequency response function corresponds to an envelope transfer function H;
the fourth step: searching a design manual according to a design result of the clamp, selecting an applicable spring, and assembling the clamp and the test device;
the fifth step: fixing the test device on a seismic table, and fixing a bolt on a flexible clamp; the pretightening force between the bolts is given according to the design requirement, and the pretightening force is measured through a pressure sensor; an acceleration sensor for control is arranged on the mounting end face of the bolt;
and a sixth step: starting the earthquake table, and finely adjusting the input reaction spectrum IRS-2 of the table top of the earthquake table through 1-2 times of preliminary tests, so that the test reaction spectrum TRS measured by the acceleration sensor on the installation end face of the bolt envelops the test target reaction spectrum TRRS;
the seventh step: the bolt is pre-tightened again, and the pre-tightening force is measured through a pressure sensor; and the seismic table is input according to the table top input reaction spectrum IRS-2 of the seismic table, and the loosening condition of the bolt under the seismic load input is observed and recorded.
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| CN201910910440.3A CN110715798B (en) | 2019-09-25 | 2019-09-25 | Test device and test method for measuring self-loosening of bolt |
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| CN201910910440.3A CN110715798B (en) | 2019-09-25 | 2019-09-25 | Test device and test method for measuring self-loosening of bolt |
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| CN111750902B (en) * | 2020-06-24 | 2021-12-24 | 兰州理工大学 | Multi-sensitivity piezoelectric bolt looseness monitoring device and use and identification method thereof |
| CN112798243B (en) * | 2020-12-25 | 2022-07-05 | 汉思科特(盐城)减震技术有限公司 | Air spring aging test device and working method thereof |
| CN113567074A (en) * | 2021-07-13 | 2021-10-29 | 杭叉集团股份有限公司 | Device and method for testing vibration resistance of bolt |
| CN115265973A (en) * | 2022-06-29 | 2022-11-01 | 中国航发湖南动力机械研究所 | Loosening life analysis method for self-locking nut |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5594177A (en) * | 1995-05-17 | 1997-01-14 | Hanse; John K. | Shaker table |
| CN101825538A (en) * | 2009-03-05 | 2010-09-08 | 名硕电脑(苏州)有限公司 | Method for detecting locking reliability of screws |
| CN107271166A (en) * | 2017-06-30 | 2017-10-20 | 武汉理工大学 | It is threadedly coupled interface anti-loosening property experimental rig and its detection method |
| CN107490431A (en) * | 2016-11-14 | 2017-12-19 | 宝沃汽车（中国）有限公司 | Oscillation drive and vibration performance test system is tightened with its bolt |
| CN107609293A (en) * | 2017-09-22 | 2018-01-19 | 上海航天测控通信研究所 | The determination methods of product loosened fastener in random vibration |
| CN108195535A (en) * | 2017-12-22 | 2018-06-22 | 清华大学 | Bolt engaging portion based on non-linear exciting feature loosens detection method and system |
| CN109855828A (en) * | 2019-04-15 | 2019-06-07 | 南昌航空大学 | A kind of bolt group connection vibration reliability experimental provision and test method |
-
2019
- 2019-09-25 CN CN201910910440.3A patent/CN110715798B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5594177A (en) * | 1995-05-17 | 1997-01-14 | Hanse; John K. | Shaker table |
| CN101825538A (en) * | 2009-03-05 | 2010-09-08 | 名硕电脑(苏州)有限公司 | Method for detecting locking reliability of screws |
| CN107490431A (en) * | 2016-11-14 | 2017-12-19 | 宝沃汽车（中国）有限公司 | Oscillation drive and vibration performance test system is tightened with its bolt |
| CN107271166A (en) * | 2017-06-30 | 2017-10-20 | 武汉理工大学 | It is threadedly coupled interface anti-loosening property experimental rig and its detection method |
| CN107609293A (en) * | 2017-09-22 | 2018-01-19 | 上海航天测控通信研究所 | The determination methods of product loosened fastener in random vibration |
| CN108195535A (en) * | 2017-12-22 | 2018-06-22 | 清华大学 | Bolt engaging portion based on non-linear exciting feature loosens detection method and system |
| CN109855828A (en) * | 2019-04-15 | 2019-06-07 | 南昌航空大学 | A kind of bolt group connection vibration reliability experimental provision and test method |
Non-Patent Citations (1)
| Title |
|---|
| 紧固件防松性能振动试验台的研制;叶涛 等;《矿山机械》;20160430;第44卷(第4期);第70-73页 * |
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