CN212645940U - Bolt axial stress measuring device based on ultrasonic wave - Google Patents
Bolt axial stress measuring device based on ultrasonic wave Download PDFInfo
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- CN212645940U CN212645940U CN202021616324.5U CN202021616324U CN212645940U CN 212645940 U CN212645940 U CN 212645940U CN 202021616324 U CN202021616324 U CN 202021616324U CN 212645940 U CN212645940 U CN 212645940U
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Abstract
The utility model discloses a bolt axial stress measuring device based on ultrasonic wave, which comprises an ultrasonic wave measuring device, a temperature measuring device and a microprocessor, wherein the ultrasonic wave measuring device sends the measured sound time difference signal of the ultrasonic wave in the bolt to the microprocessor; the temperature measuring device sends a bolt temperature signal obtained by measurement to the microprocessor; the microprocessor at least measures the acoustic time difference of the ultrasonic waves for three times through the ultrasonic measuring device and the temperature measuring module, determines a coefficient according to a matrix formula, determines a functional relation among the temperature, the axial stress and the acoustic time difference of the bolt according to the coefficient, and determines the current axial stress of the bolt based on the functional relation. Through the utility model discloses a can measure the bolt axial stress who obtains under the arbitrary temperature.
Description
Technical Field
The utility model relates to a bolt pretightning force detects technical field, especially relates to a bolt axial stress measuring device based on ultrasonic wave.
Background
Bolts, which generate stress through threads to fasten a product to be clamped, are widely used in various mechanical devices. The bolt flange connection is a detachable static seal connection structure which is widely applied to wind power generation, pressure vessels, petrochemical equipment and pipelines. In bolt connection, the bolt must be tightened during installation, i.e. before the connection is subjected to working load, the pre-applied force is called pre-tightening force, and the pre-tightening force aims to enhance the reliability and tightness of the connection so as to prevent gaps or relative slippage between the connected parts after loading. Therefore, in the flange bolt connection, the accurate pretension value and the good control precision play an important role in controlling the leakage of the joint surface.
The main failure mode of the flange bolt connection system is leakage, and bolt pre-tightening is one of important links for ensuring that the connection surface does not leak. Most bolt force detection technologies in engineering are not suitable for bolt flange joints or damage to bolt force, so that a nondestructive bolt force online detection method is needed, and bolts are monitored in real time to obtain accurate pre-tightening force values. The temperature effect causes the bolt rod to generate thermal stress and affects the safety of the bolt connecting part, so that the judgment of the thermal stress and the pretightening force applied to the bolt rod under the temperature effect on the working state of the bolt rod is more effective, and the method has guiding significance on the application of the pretightening force of the bolt.
So far, the research on the aspect of measuring the pretightening force of the bolt by using an ultrasonic nondestructive detection technology at home and abroad has obtained a certain result, and the common basic principle is based on the phenomenon that the ultrasonic wave speed changes along with the stress state change of a propagation medium, namely the phenomenon of acoustic elasticity, and the phenomenon exists in an elastic range or a nonlinear stress-strain range. In the existing ultrasonic stress measurement technology, the thermal stress generated by a bolt rod is ignored due to an ultrasonic bolt stress measurement means without considering a temperature effect, so that a result calibrated at normal temperature is not suitable for a high-temperature or low-temperature working environment any more, the safety judgment of a bolt connection part monitoring result is influenced, and the application of bolt pretightening force during production, installation and maintenance is influenced. The patent application publication No. CN109883664A discloses a real-time monitoring and diagnosing system for wind power bolts, which mentions the influence of temperature on ultrasonic measurement stress, and also provides a temperature sensor for temperature compensation, but does not give how to use the measurement result of temperature on ultrasonic stress for compensation. Patent application publication No. CN 111208207A's bolt axial stress testing arrangement based on ultrasonic measurement provides a test means and test equipment, based on experience and experiment, has obtained the compensation to the ultrasonic monitoring of pretension bolt, but this test equipment need combine together high low temperature test case and tensile testing machine to need the multiunit to mark, the complexity is higher, and the cost is higher.
Disclosure of Invention
In view of this, the utility model provides a bolt axial stress measuring device based on ultrasonic wave can measure the bolt axial stress who obtains under the arbitrary temperature.
In order to achieve the above object, the present invention provides an ultrasonic-based bolt axial stress measuring device, comprising an ultrasonic measuring device, a temperature measuring device and a microprocessor, wherein the microprocessor is connected with the ultrasonic measuring device and the temperature measuring device respectively, wherein,
the ultrasonic measuring device sends the measured sound time difference signal of the ultrasonic waves in the bolt to the microprocessor;
the temperature measuring device sends a bolt temperature signal obtained by measurement to the microprocessor;
the microprocessor includes a temperature compensation unit and a processing unit, wherein,
the temperature compensation unit acquires a first acoustic time difference t of at least three measured ultrasonic waves0Second sound time difference taAnd a third sound time difference tbInputting a matrix formula to obtain coefficients A, B, C and D, and obtaining the temperature and the shaft of the bolt according to the coefficientsTo a functional relation of stress and acoustic time difference and inputting said functional relation to said processing unit, wherein said three measurements comprise at a first bolt temperature T0And a first prestress F0Under the condition of (1), the first acoustic time difference t obtained by the first measurement0First bolt temperature T0And a first prestress F1Under the condition of (1) second measured second acoustic time difference taSecond bolt temperature T1And a first prestress F0A third acoustic time difference t obtained by a third measurement under the condition of (2)b；
The matrix formula is satisfied;
δta＝ta-t0，δtb＝tb-t0，
the functional relation is as follows: a, T + B, F + C, delta T and D are 0, delta T is the sound time difference of the current ultrasonic wave in the bolt, T is the current bolt temperature, and F is the current axial stress;
and the processing unit inputs the received current bolt temperature and the received sound time difference of the current ultrasonic wave in the bolt into a functional relation of the bolt temperature, the axial stress and the sound time difference to obtain and output the current axial stress of the bolt.
Preferably, the bolt pretightening force measuring device comprises a probe, the ultrasonic measuring device comprises a first piezoelectric wafer and a second piezoelectric wafer, the temperature measuring module comprises a thermistor, and the first piezoelectric wafer, the second piezoelectric wafer and the thermistor are packaged together at the top end of the probe.
Preferably, the first piezoelectric wafer is connected to the microprocessor, the second piezoelectric wafer is connected to the microprocessor, and the thermistor is connected to the microprocessor, wherein,
the first piezoelectric wafer generates ultrasonic waves to enable the ultrasonic waves to be transmitted in the bolt;
the second piezoelectric wafer receives a signal returned by the ultrasonic wave transmitted by the bolt, converts the signal into a pulse electric signal and sends the pulse electric signal to the microprocessor;
the micro-processing records the receiving time of the received pulse electrical signal, and the difference value operation is carried out on the receiving time and the sending time to obtain the sound time difference of the ultrasonic wave in the bolt;
the thermistor measures the bolt temperature and sends the bolt temperature to a microprocessor.
Preferably, the first measurement condition is a first bolt temperature T0Is 300K and a first prestress F0Is 0 kN; the second measurement condition is set as the first bolt temperature T0Is 300K and a second prestress F1Is 1000 kN; the third measurement condition is set as a second bolt temperature T1Is 350K and a first prestress F0Is 0 kN.
Preferably, the processing unit generates an analysis map corresponding to the relationship among the bolt temperature, the axial stress and the acoustic time difference according to the functional relationship among the bolt temperature, the axial stress and the acoustic time difference, and determines the unique bolt axial stress in the analysis map when the acoustic time difference between the bolt working temperature and the ultrasonic wave is measured based on the analysis map.
Preferably, the processing unit is further configured to determine a unique bolt operating temperature in the analysis map when the axial stress of the bolt and the acoustic time difference of the ultrasonic wave are measured based on the analysis map.
Compared with the prior art, the utility model provides a pair of bolt axial stress measuring device based on ultrasonic wave, the beneficial effect who brings is: the utility model can obtain the ultrasonic measurement rule of the bolt under any temperature and any prestress by only three times of measurement, can determine the combined action of the prestress and the temperature compensation effect of the bolt, is applied to the pretightening force measurement under any temperature, and does not need to be repeatedly calibrated under different temperatures; the technical scheme is simpler and more convenient, takes effect more quickly and has wider coverage; the bolt stress measuring part and the temperature measuring part are integrated on one unified probe, and extra additional equipment such as a thermostat and the like is not needed; the characteristic curve of the axial stress of the bolt measured by ultrasonic waves is combined with the characteristic curve of the temperature and the prestress, so that the characteristic map of the comprehensive stress and the temperature is provided, and the method can be more conveniently applied to an ultrasonic detector for on-site bolt detection; the technical scheme for effectively measuring the axial stress of the ultrasonic measurement bolt changing along with the temperature is provided.
Drawings
Fig. 1 is a system schematic diagram of an ultrasonic based bolt axial stress measurement device according to an embodiment of the present invention.
Figure 2 is a schematic diagram of a probe in accordance with one embodiment of the present invention.
Fig. 3 is an analysis map corresponding to the relationship among the bolt temperature, the pre-tightening force and the acoustic time difference according to an embodiment of the present invention.
The reference numbers: 201-a first piezoelectric wafer; 202-a second piezoelectric wafer; 203-a thermistor; 13-a microprocessor.
Detailed Description
The present invention will be described in detail with reference to the specific embodiments shown in the drawings, but the embodiments are not limited to the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the embodiments are included in the scope of the present invention.
As shown in fig. 1 an embodiment of the utility model provides an ultrasonic wave-based bolt axial stress measuring device, including ultrasonic wave measuring device 10, temperature measuring device 11 and microprocessor 12, microprocessor 12 respectively with ultrasonic wave measuring device 10 and temperature measuring device are connected 11, wherein, ultrasonic wave measuring device 10 will measure the ultrasonic wave that obtains and sound time difference signal transmission in the bolt to microprocessor 12, temperature measuring device 11 will measure the bolt temperature signal transmission that obtains to microprocessor 12, microprocessor 12 includes temperature compensation unit 120 and processing unit 121, wherein, temperature compensation unit 120 will acquire the ultrasonic wave of at least cubic measurement's ultrasonic first sound time difference t0The first stepTime difference of two sounds taAnd a third sound time difference tbInputting a matrix formula to obtain coefficients A, B, C and D, obtaining a functional relation of bolt temperature, axial stress and acoustic time difference according to the coefficients, and inputting the functional relation into the processing unit, wherein the three measurements comprise a first bolt temperature T0And a first prestress F0Under the condition of (1), the first acoustic time difference t obtained by the first measurement0First bolt temperature T0And a first prestress F1Under the condition of (1) second measured second acoustic time difference taSecond bolt temperature T1And a first prestress F0A third acoustic time difference t obtained by a third measurement under the condition of (2)b；
The matrix formula is satisfied;
δta＝ta-t0，δtb＝tb-t0，
the functional relation is as follows: a, T + B, F + C, delta T and D are 0, delta T is the sound time difference of the current ultrasonic wave in the bolt, T is the current bolt temperature, and F is the current axial stress;
the processing unit inputs the received current bolt temperature and the received sound time difference of the current ultrasonic wave in the bolt into the functional relation among the bolt temperature, the axial stress and the sound time difference to obtain and output the current axial stress of the bolt,
as shown in fig. 2, the bolt pretension measuring device comprises a probe, the ultrasonic measuring device comprises the first piezoelectric wafer 201 and the second piezoelectric wafer 202, the temperature measuring module comprises a thermistor 203, and the first piezoelectric wafer 201, the second piezoelectric wafer 202 and the thermistor 203 are packaged together and mounted on the top end of the probe and are fittingly mounted on the top of the bolt. During installation, affinity agent is coated on the surface of the probe, and then the probe is installed on the top of the bolt for weighing. The first piezoelectric wafer is connected with the microprocessor, the second piezoelectric wafer is connected with the microprocessor, and the thermistor is connected with the microprocessor. The microprocessor generates a pulsed electrical signal and applies the pulsed electrical signal to the first piezoelectric wafer and records the time of transmission of the pulsed electrical signal. By applying a pulsed voltage to the first piezoelectric wafer, a momentary expansion and contraction can be produced, giving a pulsed pressure signal to the abutting bolt. The first piezoelectric wafer generates ultrasonic waves, which propagate in the bolt. And the second piezoelectric wafer receives the signal returned by the ultrasonic wave transmitted by the bolt, converts the signal into a pulse electric signal and sends the pulse electric signal to the microprocessor. And the microprocessor receives the pulse electrical signal and records the receiving time, and performs difference operation on the receiving time and the sending time to obtain the sound time difference of the ultrasonic wave in the bolt. The thermistor measures the temperature of the bolt and sends the bolt temperature to a microprocessor. In this embodiment, a piezoelectric wafer is used to collect ultrasonic signals, and an electromagnetic ultrasonic ring energy device may be used to collect ultrasonic signals instead.
In a general case, the structural properties of a material may be defined by the young's modulus E and the poisson ratio v, and both may be defined by a temperature-dependent piecewise function T, and measured experimentally. At present, various steel products applied in industry have detailed database which can be inquired.
Based on the structural physical properties of the material defined by the young's modulus E and the poisson ratio v, the physical properties defined by the lame coefficient, i.e. the first lame coefficient parameter λ:
second ramet coefficient parameter μ:
adding three-order superelasticity coefficient correction l, m and n on the basis of the first Lame coefficient parameter and the second Lame coefficient parameter, wherein the superelasticity coefficient correction is obtained by experimental measurement to obtain a correction relational expression of the pretightening force to the sound velocity and a sound velocity relational expression:
cσ＝c0(1+CLσ)；
wherein, cσFor the speed of sound under the influence of the pre-tightening force, c0At acoustic velocity without pre-tightening effect, CLTo calculate cσAnd the sigma is the deformation of the bolt per unit length caused by the pretightening force. Through the pulse electrical signal converted by the second piezoelectric wafer, the microprocessor obtains the sound time difference of the ultrasonic wave in the bolt, and the sound time difference is influenced by the sound velocity, namely the sound velocity of the ultrasonic wave is changed due to the pretightening force and the temperature, the sound path length is also changed, and the pretightening force causes the deformation of the bolt and the deformation caused by the thermal expansion effect. The research shows that under the condition that the daily temperature change is not large (-50K-100K) and the pre-tightening force does not cause the material to generate plastic deformation, the influences can be approximately regarded as a linear relation. And calibrating the coefficients based on the principle.
The temperature compensation unit at least measures the propagation time of the third ultrasonic wave through the ultrasonic measuring device and the temperature measuring module, wherein the propagation time is respectively the temperature T of the first bolt0And a first prestress F0The first acoustic time difference t measured under the condition of (1)0At a first bolt temperature T0And a first prestress F1Measured under the conditions of (1) the resulting second acoustic time difference taAnd a second bolt temperature T1And a first prestress F0Measured under the condition of (1) and the obtained third acoustic time difference tbThe coefficients A, B, C and D are determined according to the following matrix equation;
wherein, δ ta＝ta-t0，δtb＝tb-t0. Specifically, the first measurement: measuring the temperature T of the bolt working at the first bolt by a thermistor0At 300K, a first prestress F is applied to the bolt by an external stress-stretching device0Under the condition of 0kN, the microprocessor generates a pulse electric signal and applies the pulse electric signal to the first piezoelectric wafer, the first piezoelectric wafer excites an ultrasonic signal and transmits the ultrasonic signal in the bolt, the second piezoelectric wafer receives an echo signal, converts the echo signal into a pulse electric signal and transmits the pulse electric signal to the microprocessor, and the microprocessor obtains a first sound time difference t of the ultrasonic wave0. Likewise, the second measurement: at a first bolt temperature T0Is 300K and a second prestress F1Second acoustic time difference t measured at 1000kNa(ii) a The third measurement: at a second bolt temperature T1Is 350K and a first prestress F0The third acoustic time difference t measured at 0kNb. Based on the three sets of measured data, coefficients A, B, C and D are calculated according to the matrix equation described above. In this embodiment, the coefficient calibration can be realized by using three times of measurement data. But adopt the measured data of more multiunit to carry out the coefficient and mark to realize higher precision, also belong to within the scope of the utility model.
The temperature compensation unit obtains a functional relation among the temperature, the axial stress and the acoustic time difference of the bolt according to the coefficient, and determines the current axial stress of the bolt based on the functional relation, wherein the functional relation is as follows:
A·T+B·F+C·δt+D＝0；
and delta T is the sound time difference of the current ultrasonic wave in the bolt, T is the current bolt temperature, and F is the current axial stress. And the delta t is obtained by calculating the sound velocity correction relational expression and the sound velocity relational expression. Based on the plane formula, under the condition of a given temperature T, the bolt pretightening force F and the sound time difference have a one-to-one correspondence relationship, and therefore the relationship between the sound time difference and the axial stress of ultrasonic waves at different temperatures can be obtained. And the processing unit inputs the received current bolt temperature and the received sound time difference of the current ultrasonic wave in the bolt into a functional relation of the bolt temperature, the axial stress and the sound time difference to obtain and output the current axial stress of the bolt. The working temperature of the current bolt is obtained through thermistor measurement, the sound time difference of the current ultrasonic wave in the bolt is obtained through ultrasonic measurement, and the pretightening force of the current bolt can be correspondingly obtained according to the plane formula.
According to the utility model discloses a specific embodiment, the processing unit basis the functional relation of bolt temperature, axial stress and sound time difference generates the analysis map that bolt temperature, axial stress and sound time difference three relation correspond, as shown in FIG. 3, F shows axial stress in the picture, and T shows sound time difference. Based on the analysis map, when the working temperature of the bolt and the acoustic time difference of the ultrasonic wave are measured, determining the only axial stress of the bolt in the analysis map; or, based on the analysis map, determining a unique bolt operating temperature in the analysis map when the axial stress of the bolt and the acoustic time difference of the ultrasonic wave are measured.
According to the utility model discloses a specific embodiment, microprocessor includes a burning module, will the functional relation burning of bolt temperature, axial stress and sound time difference extremely microprocessor. And in the bolt pretightening force measuring process, the microprocessor calculates and obtains the corresponding axial stress according to the obtained working temperature of the current bolt and the ultrasonic sound time difference. The utility model discloses a still another embodiment, microprocessor sends the operating temperature of the current bolt that will acquire and ultrasonic sound time difference to high in the clouds server, the high in the clouds server basis the functional relation calculation of bolt temperature, axial stress and sound time difference obtains corresponding axial stress.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (3)
1. A bolt axial stress measuring device based on ultrasonic waves is characterized by comprising an ultrasonic measuring device, a temperature measuring device and a microprocessor, wherein the microprocessor is respectively connected with the ultrasonic measuring device and the temperature measuring device,
the ultrasonic measuring device sends the measured sound time difference signal of the ultrasonic waves in the bolt to the microprocessor;
the temperature measuring device sends a bolt temperature signal obtained by measurement to the microprocessor;
the microprocessor includes a temperature compensation unit and a processing unit.
2. The ultrasonic-based bolt axial stress measurement device of claim 1, wherein the bolt pretension measurement device comprises a probe, the ultrasonic measurement device comprises a first piezoelectric wafer and a second piezoelectric wafer, the temperature measurement module comprises a thermistor, and the first piezoelectric wafer, the second piezoelectric wafer and the thermistor are together encapsulated at a tip of the probe.
3. The ultrasonic-based bolt axial stress measurement device of claim 2, wherein the first piezoelectric wafer is connected to the microprocessor, the second piezoelectric wafer is connected to the microprocessor, and the thermistor is connected to the microprocessor.
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| CN113984256A (en) * | 2021-10-08 | 2022-01-28 | 苏州热工研究院有限公司 | Measuring device and measuring method for pipeline hanger load |
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| CN113984256A (en) * | 2021-10-08 | 2022-01-28 | 苏州热工研究院有限公司 | Measuring device and measuring method for pipeline hanger load |
| CN113984256B (en) * | 2021-10-08 | 2023-12-22 | 苏州热工研究院有限公司 | Measuring device and measuring method for pipeline hanger load |
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