CN111238702A - Bolt axial stress testing device and testing method based on ultrasonic measurement - Google Patents
Bolt axial stress testing device and testing method based on ultrasonic measurement Download PDFInfo
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- CN111238702A CN111238702A CN202010264828.3A CN202010264828A CN111238702A CN 111238702 A CN111238702 A CN 111238702A CN 202010264828 A CN202010264828 A CN 202010264828A CN 111238702 A CN111238702 A CN 111238702A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
- G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L25/00—Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency
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Abstract
The invention provides a testing device and a testing method based on ultrasonic measurement of axial stress of a bolt, wherein the testing device comprises a tensile testing machine, a high-low temperature test box, a stress measurement system and an ultrasonic measurement system, the stress measurement system comprises a strain gauge, a signal acquisition unit and a signal processing unit, and the strain gauge is adhered to a screw rod of the bolt to be tested; a detection probe of the ultrasonic measurement system is arranged at the end part of the tested bolt; the high-low temperature test chamber is used for placing a tensile testing machine and a tested bolt and adjusting the testing temperature; during testing, the tensile testing machine applies pressure to the tested bolt, the pressure variable sheet adhered to the tested bolt deforms, and the signal acquired by the signal acquisition unit is processed by the signal processing unit and then output; and the ultrasonic measurement system measures and outputs an acoustic time difference signal of the ultrasonic wave propagating in the bolt.
Description
Technical Field
The invention belongs to the technical field of nondestructive testing, and relates to a testing method for ultrasonically measuring the axial stress of a bolt, which is suitable for testing whether the axial stress of the bolt is accurately ultrasonically detected and manufacturing a data curve of the ultrasonically detected bolt.
Background
At present, domestic research on the ultrasonic measurement technology of bolt stress has achieved certain achievements.
One important influencing factor of ultrasonic stress measurement is temperature, and when the influence of temperature is studied, a correction method for the temperature is proposed to explain two points:
firstly, under the condition of temperature influence, stress measurement by a method combining longitudinal waves and transverse waves is better than that by using longitudinal waves alone;
secondly, due to the use characteristics of the threaded connection pair, the bolt bears axial tension and circumferential torsion when being used in a matched mode, and the influence of the circumferential torsion on the force acoustic elasticity measurement of the screw detection shaft can be ignored when the stress is measured by utilizing ultrasonic.
The coupling of the ultrasonic probe and the workpiece to be tested is taken as a most basic technical parameter, and the influence on the test result is an important problem to be solved firstly. During measurement, meshes must be performed by applying a bandage agent to the probe.
On the processing of the detected workpiece. With the research and development of piezoelectric ceramics, the performance of the piezoelectric ceramics is continuously improved, the preparation methods and means of the piezoelectric ceramics are more and more, and the research on the performance structure of the transducer is continuously broken through.
When the ultrasonic exciter of the tester contacts the piezoelectric ceramic sensor, high-voltage electric pulses are generated and applied to the piezoelectric ceramic to generate ultrasonic waves. The ultrasonic wave is transmitted in the bolt, the return signal is received by the acquisition and receiving device and is analyzed and processed, and the current stress state of the bolt is reflected on a screen.
The defects of the traditional ultrasonic detection and the existing manual detection one by one on site have the problems of safety risk, low detection efficiency and high detection cost.
Disclosure of Invention
The invention provides a test device for measuring the axial stress of a bolt based on ultrasonic, which can test various high-strength bolts of a wind generating set.
The invention also aims to provide a test method for ultrasonically measuring the axial stress of the bolt.
The invention adopts the following specific technical scheme:
a testing device for measuring axial stress of a bolt based on ultrasonic comprises a tensile testing machine, a high-low temperature test box, a stress measuring system and an ultrasonic measuring system; the stress measurement system comprises a strain gauge, a signal acquisition unit and a signal processing unit, wherein the strain gauge is adhered to a screw rod of a bolt to be measured; a detection probe of the ultrasonic measurement system is arranged at the end part of the tested bolt; the high-low temperature test chamber is used for placing a tensile testing machine and a tested bolt and adjusting the testing temperature; during testing, the tensile testing machine applies pressure to the tested bolt, the pressure variable sheet adhered to the tested bolt deforms, and the signal acquired by the signal acquisition unit is processed by the signal processing unit and then output; and the ultrasonic measurement system measures and outputs an acoustic time difference signal of the ultrasonic wave propagating in the bolt.
Further, the ultrasonic measurement system comprises a detection probe, a probe fixing device, an ultrasonic measurement instrument and a coupling agent; the detection probe is arranged at the end part of the tested bolt through the probe fixing device, and the upper matching surface of the tested bolt is filled with a coupling agent; the ultrasonic measuring instrument receives and processes the signals measured by the detection probe.
Further, the probe fixing device comprises a cylindrical probe placing box, a permanent magnet and a fixing bolt; the probe is arranged in the cylindrical probe placing box and is fixed through a fixing bolt; the permanent magnet is positioned at the lower part of the cylindrical probe placing box and fixedly bonded with the probe placing box, and the permanent magnet is simultaneously used for being connected with the bolt.
Further, the permanent magnet is bonded to the probe placement box by 502 glue.
Furthermore, the probe fixing device is also provided with an annular cover for connecting with the end part of the tested bolt; or the annular permanent magnet is connected with the end part of the bolt to be detected.
Furthermore, the ultrasonic measuring instrument requires that the measurement precision of the propagation time of the ultrasonic longitudinal wave and the ultrasonic transverse wave reaches 1ns, and the measurement principle is that the propagation time is measured by adopting a bottom surface reflection echo mode.
Further, a 400-ton tensile testing machine is adopted as the tensile testing machine, and bolt clamps with various specifications are arranged.
Further, the incubator of the high-low temperature test chamber is provided with an extension cover, and the tested bolt is placed in the extension cover.
Furthermore, the temperature adjusting range of the high-low temperature test box is-50 to + 100 ℃, the constant temperature box is provided with an extension cover, and the test bolt performs a test at a specific constant temperature in the extension cover.
A testing method for ultrasonically measuring the axial stress of a bolt, which adopts the testing device of the claims 1-9, and comprises the following steps:
1) polishing an area on a screw of a bolt to be tested;
2) attaching a strain gauge and assembling a stress measurement system;
3) installing a detection probe, and coupling and fixing the detection probe and the end part of the bolt to be detected through a probe fixing device;
4) the detected bolt is fixed on the tensile testing machine, and the extension cover of the high-low temperature test box thermostat seals the detected bolt therein;
5) under the condition that the test temperature of the high-low temperature test box is unchanged, the tensile testing machine applies variable pressure to the bolt to be tested, stress values under various pressure conditions are obtained through measurement of a stress measurement system, and propagation time is measured through an ultrasonic measurement system;
6) according to the test result, calculating the difference between the measured propagation times under the two applied stresses, namely the acoustic time difference, and drawing an axial stress and acoustic time difference curve;
7) adjusting the temperature of the high-low temperature test box under the condition of constant pressure application, and recording the propagation time measured by an ultrasonic measurement system at each temperature;
8) and drawing a temperature and propagation time curve according to the test result.
Further, in the step 5), the values of the changed pressure are respectively 100MPa, 200MPa, 300MPa, 400MPa and 500 MPa.
Further, in the step 7), the temperature of the high-low temperature test chamber is adjusted to-20 ℃, 0 ℃, +10 ℃, +20 ℃, and, +40 ℃.
Compared with the prior art, the invention has the following beneficial effects:
1. the test device for measuring the axial stress of the bolt based on the ultrasonic wave overcomes the defects of the traditional ultrasonic detection and solves the problems of safety risk, low detection efficiency and high detection cost caused by the fact that the existing manual detection is carried out on site one by one. The accuracy of bolt detection is guaranteed.
2. The invention takes various high-strength bolts of the wind generating set as test samples to carry out test research objects, and utilizes the tensile testing machine, the high-low temperature test box, the stress measurement system, the bolt axial force ultrasonic measurement system and other test equipment to construct a test research platform of a cost project to carry out related tests.
3. The method can be used for judging whether the axial stress of the ultrasonic detection bolt is accurate or not, and manufacturing a characteristic curve of the axial stress of the ultrasonic detection bolt and a characteristic curve of temperature and stress, wherein the characteristic curve of the temperature and the stress is used for correcting the influence of the temperature on the stress, and the characteristic curve of the axial stress of the ultrasonic detection bolt can be used for finding out the linear relation between the acoustic time difference and the axial stress of the bolt, so that an ultrasonic detector is developed and applied to on-site bolt detection.
Drawings
FIG. 1 is a schematic structural diagram of a testing apparatus according to the present invention;
FIG. 2 is a second schematic structural diagram of the testing apparatus of the present invention (also shown in the abstract);
FIG. 3 is a graph showing the relationship between the bolt sound time difference and the axial stress at 20 ℃ for 20 # carbon steel;
in the figure: tensile testing machine 010, tensile testing machine 011 are furnished with the bolt anchor clamps 012 of various specifications, high low temperature test case 020, thermostated container 021, extend cover 022, and bolt axle power ultrasonic measurement system 030 is by detecting probe 031, probe fixing device 032, connecting wire 033, ultrasonic measurement appearance 034, stress measurement system 040, foil gage 041, connecting wire 042, signal acquisition unit 043, signal processing unit 044.
Detailed Description
The invention is further described with reference to the accompanying drawings in which:
the first embodiment is as follows:
the invention discloses a test device for measuring axial stress of a bolt based on ultrasonic, which comprises:
as shown in fig. 1, the tensile testing machine 010, the high-low temperature test chamber 020, the stress measurement system 040, the bolt axial force ultrasonic measurement system 030, and the like.
The tensile testing machine adopts a 400-ton tensile testing machine 011, and is provided with bolt clamps 012 of various specifications. The temperature of the constant temperature box 021 is-50 to + 100 ℃, the high-low temperature test box is provided with an extension cover 022, and a test bolt is tested in the extension cover. The stress measurement system 040 is composed of a strain gauge 041, a connecting wire 042, a signal acquisition unit 043 and a signal processing unit 044, and the strain gauge is adhered to the screw of the bolt to be measured.
The ultrasonic measurement system 030 comprises a detection probe 031, a probe fixing device 032, a connecting line 033, an ultrasonic measurement instrument 034 and a coupling agent, wherein the ultrasonic measurement instrument requires that the measurement precision of the propagation time of ultrasonic longitudinal waves and transverse waves reaches 1ns, and the measurement principle is that the propagation time is measured by adopting a bottom surface reflection echo mode. A detection probe of the ultrasonic measurement system is arranged at the end part of the tested bolt; the high-low temperature test chamber is used for placing a tensile testing machine and a tested bolt and adjusting the testing temperature; during testing, the tensile testing machine applies pressure to the tested bolt, the pressure variable sheet adhered to the tested bolt deforms, and the signal acquired by the signal acquisition unit is processed by the signal processing unit and then output; and the ultrasonic measurement system measures and outputs an acoustic time difference signal of the ultrasonic wave propagating in the bolt.
The first test example:
taking a bolt made of 20-grade carbon steel as an example, the test process of ultrasonically measuring the axial stress of the bolt by adopting the device in the previous example is as follows:
(1) a flat smooth area of 2X 1mm was ground in the middle of the test bolt screw.
(2) And attaching the strain gauge in a smooth area of the screw by adopting 502 glue, wherein the direction is parallel to the axial direction of the bolt. The connecting wire connects gradually foil gage, signal acquisition unit, signal processing unit to debug stress measurement system, record the axial strain value under the outside zero stress.
(3) Selecting a detection probe matched with the specification of the test bolt, installing the detection probe and connecting an ultrasonic measuring instrument to measure the bolt;
(4) and fixing the test bolt on the tensile testing machine by using a bolt clamp, and fixedly coupling the upper end of the bolt with the probe by adopting a fixing device. The tested bolt is placed in the extending cover of the incubator for high and low temperature test.
(5) Keeping the temperature of the high-low temperature test box unchanged at 20 ℃, applying 100MPa, 200MPa, 300MPa, 400MPa and 500MPa of tensile force to the bolt by a tensile testing machine in sequence, measuring the axial stress value of the test bolt through a stress measuring system, measuring the propagation time of ultrasound on the bolt through an ultrasonic detector, and recording the propagation time in a one-to-one correspondence mode.
(6) And finding out the relation between the axial stress of the tested bolt and the ultrasonic propagation time according to the test record, and manufacturing a characteristic curve of the relation between the ultrasonic testing bolt sound time difference and the stress. Fig. 3 shows the characteristic curve of the relationship between the sound time difference and the stress of the 20-steel bolt subjected to ultrasonic measurement at the test temperature of 20 ℃ when the variable pressure is applied. The acoustic time difference is the difference between the measured travel times when the two stresses are applied.
(7) Keeping the tensile testing machine to apply 100MPa to the bolts in sequence, adjusting the temperature of the high-low temperature test box to five grades of-20 ℃, 0 ℃, 10 ℃, 20 ℃ and 40 ℃, respectively, measuring the propagation time of the ultrasound on the bolts at different temperatures by using an ultrasonic detector, and respectively and correspondingly recording the propagation time.
(8) And finding out the relation between the ultrasonic propagation time and the temperature according to the test record, and making a characteristic curve of the ultrasonic measurement bolt temperature and the propagation time. After the bolt bears the axial force, the propagation time of the bolt has a good linear relation with the temperature of the bolt. The bolt has better linearity between the temperature and the propagation time under the load and the non-load bearing condition. Under the load bearing condition and the non-load bearing condition of the same bolt, the propagation time of the bolt and the temperature change of the bolt have a linear relation, and the slopes under the two conditions are close.
And according to the drawn axial stress and acoustic time difference curve, the method is applied to on-site bolt stress detection. And correcting the propagation time measured by actually detecting the temperature on site by referring to the temperature and propagation time curve.
The characteristic curve of temperature and stress and the characteristic curve of the axial stress of the ultrasonic measurement bolt are applied to a software system of an ultrasonic detector, so that the ultrasonic stress detector is developed and applied to on-site bolt stress detection.
Claims (10)
1. The utility model provides a testing arrangement based on ultrasonic measurement bolt axial stress, includes tensile testing machine and high low temperature test box, its characterized in that: the stress measurement system comprises a strain gauge, a signal acquisition unit and a signal processing unit, and the strain gauge is adhered to a screw rod of the bolt to be measured; a detection probe of the ultrasonic measurement system is arranged at the end part of the tested bolt; the high-low temperature test chamber is used for placing a tensile testing machine and a tested bolt and adjusting the testing temperature; during testing, the tensile testing machine applies pressure to the tested bolt, the pressure variable sheet adhered to the tested bolt deforms, and the signal acquired by the signal acquisition unit is processed by the signal processing unit and then output; and the ultrasonic measurement system measures and outputs an acoustic time difference signal of the ultrasonic wave propagating in the bolt.
2. The test device for ultrasonically measuring the axial stress of the bolt according to claim 1, wherein: the ultrasonic measurement system comprises a detection probe, a probe fixing device, an ultrasonic measurement instrument and a coupling agent; the detection probe is arranged at the end part of the tested bolt through the probe fixing device, and the upper matching surface of the tested bolt is filled with a coupling agent; the ultrasonic measuring instrument receives and processes the signals measured by the detection probe.
3. The test device based on ultrasonic measurement bolt axial stress of claim 2, characterized in that: the probe fixing device comprises a cylindrical probe placing box, a permanent magnet and a fixing bolt; the probe is arranged in the cylindrical probe placing box and is fixed through a fixing bolt; the permanent magnet is positioned at the lower part of the cylindrical probe placing box and fixedly bonded with the probe placing box, and the permanent magnet is simultaneously used for being connected with the bolt.
4. The test device based on ultrasonic measurement bolt axial stress of claim 3, characterized in that: the permanent magnet is bonded with the probe placing box through 502 glue.
5. The test device based on ultrasonic measurement bolt axial stress of claim 3, characterized in that: the probe fixing device is also provided with an annular cover for connecting with the end part of the tested bolt; or the annular permanent magnet is connected with the end part of the bolt to be detected.
6. The test device based on ultrasonic measurement bolt axial stress of claim 3, characterized in that: the thermostated container of high low temperature test case is equipped with and extends the cover, is placed in extending the cover by the test bolt.
7. The test device based on ultrasonic measurement bolt axial stress of claim 3, characterized in that: the temperature adjusting range of the high-low temperature test box is-50 to + 100 ℃.
8. A test method for ultrasonically measuring the axial stress of a bolt by using the test device of the claims 1-7 comprises the following steps:
1) polishing an area on a screw of a bolt to be tested;
2) attaching a strain gauge and assembling a stress measurement system;
3) installing a detection probe, and coupling and fixing the detection probe and the end part of the bolt to be detected through a probe fixing device;
4) the detected bolt is fixed on the tensile testing machine, and the extension cover of the high-low temperature test box thermostat seals the detected bolt therein;
5) under the condition that the test temperature of the high-low temperature test box is unchanged, the tensile testing machine applies variable pressure to the bolt to be tested, stress values under various pressure conditions are obtained through measurement of a stress measurement system, and propagation time is measured through an ultrasonic measurement system;
6) according to the test result, calculating the difference between the measured propagation times under the two applied stresses, namely the acoustic time difference, and drawing an axial stress and acoustic time difference curve;
7) adjusting the temperature of the high-low temperature test box under the condition of constant pressure application, and recording the propagation time measured by an ultrasonic measurement system at each temperature;
8) and drawing a temperature and propagation time curve according to the test result.
9. The method for testing the axial stress of the bolt according to claim 8, wherein in the step 5), the values of the changed pressure are 100MPa, 200MPa, 300MPa, 400MPa and 500MPa respectively.
10. The method for testing the axial stress of a bolt according to claim 9, wherein in step 7), the temperatures of the high and low temperature test chambers are adjusted to-20 ℃, 0 ℃, +10 ℃, +20 ℃, and, +40 ℃.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010264828.3A CN111238702A (en) | 2020-04-07 | 2020-04-07 | Bolt axial stress testing device and testing method based on ultrasonic measurement |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112033798A (en) * | 2020-08-26 | 2020-12-04 | 北京理工大学 | Baxinge effect test fixture |
| CN112033602A (en) * | 2020-09-24 | 2020-12-04 | 罗治军 | High-strength bolt ultrasonic axial force coefficient field calibration system |
| CN113155357A (en) * | 2021-03-11 | 2021-07-23 | 中国长江电力股份有限公司 | Ultrasonic measurement calibration experiment table and method for axial tensile stress of large bolt |
-
2020
- 2020-04-07 CN CN202010264828.3A patent/CN111238702A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112033798A (en) * | 2020-08-26 | 2020-12-04 | 北京理工大学 | Baxinge effect test fixture |
| US11674871B2 (en) | 2020-08-26 | 2023-06-13 | Beijing Institute Of Technology | Bauschinger effect test fixture |
| CN112033602A (en) * | 2020-09-24 | 2020-12-04 | 罗治军 | High-strength bolt ultrasonic axial force coefficient field calibration system |
| CN113155357A (en) * | 2021-03-11 | 2021-07-23 | 中国长江电力股份有限公司 | Ultrasonic measurement calibration experiment table and method for axial tensile stress of large bolt |
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