Flange sealing surface stress detection method and device based on circular array ultrasonic sensor

Abstract

The invention relates to the technical field of mechanical equipment stress nondestructive testing, in particular to a flange sealing surface stress detection method based on a circular array ultrasonic sensor, and the method comprises the steps: obtaining a first sound time difference between an ultrasonic transmitting wave and an ultrasonic receiving wave according to a first oscillogram, solving the stress at the flange plate in the zero stress state according to the acoustic elastic model and the first acoustic time difference; solving the stress at the flange plate under the bolt standard pre-tightening force according to the acoustic elastic model and the second sound time difference; force is applied to the flange plate through the torque wrench according to the fixed torque gradient increment, a third oscillogram of the ultrasonic excitation wave passing through the flange plate under each stress loading is obtained through the circular ring array ultrasonic sensor, and a third sound time difference between the ultrasonic transmitting wave and the ultrasonic receiving wave is obtained according to the third oscillogram; and solving the stress at the flange plate under different stress loading conditions according to the acoustic elastic model and the third acoustic time difference. According to the invention, the stress distribution condition of the flange sealing surface is effectively detected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical equipment stress nondestructive testing, and particularly relates to a flange sealing surface stress detection method and device based on a circular array ultrasonic sensor. BACKGROUND

[0002] Flange connection, as the core static sealing structure of pressure-bearing equipment and pipeline systems, is widely used in the fields of petrochemical industry, energy and power, and special equipment. However, these connection points are long-term served in the working conditions of high temperature, high pressure, corrosion and cyclic load, and the risk of sealing performance failure is extremely high. Once the sealing fails, not only will it cause medium leakage and energy loss, but also it may cause the diffusion of toxic substances, fire and even explosion and other extreme safety accidents. The sealing effectiveness of the flange connection not only depends on the reasonable setting of the bolt pretightening force, but also is more crucial in the uniformity of the stress distribution of the sealing surface. In the actual assembly process, affected by improper bolt tightening sequence, flange surface processing skew or gasket material performance unevenness, the sealing stress is easy to concentrate in the local area, which leads to the overload of the gasket in some areas and the insufficient compression in some areas, and then forms a potential leakage channel, greatly shortens the service life of the sealing structure and increases the leakage risk.

[0003] In some scenarios, due to different working conditions of the flange plate, the stress distribution of the flange sealing surface is difficult to accurately monitor under different working conditions, and uneven bolt pretightening force or gasket material difference is easy to cause stress concentration, forming a leakage risk. Therefore, how to detect the stress distribution of the flange sealing surface is a technical problem to be solved by the person skilled in the art. SUMMARY

[0004] In order to solve the technical problem of detecting the stress distribution of the flange sealing surface, the purpose of the present application is to provide a flange sealing surface stress detection method based on a circular array ultrasonic sensor, and the technical solution adopted is as follows:

[0005] In a first aspect, the embodiments of the present application disclose a flange sealing surface stress detection method based on a circular array ultrasonic sensor, which comprises the following steps: acquiring a first waveform diagram of an ultrasonic excitation wave through a flange under a zero stress state by a circular array ultrasonic sensor, acquiring a first acoustic time difference between an ultrasonic emission wave and an ultrasonic receiving wave according to the first waveform diagram, solving the stress at the flange under the zero stress state according to an acoustic elastic model and the first acoustic time difference, wherein the circular array ultrasonic sensor is composed of eight ultrasonic sensor units arranged in a circle and arranged in eight directions of the circumference of the flange; acquiring a second waveform diagram of the ultrasonic excitation wave through the flange under a standard bolt preload by the circular array ultrasonic sensor, acquiring a second acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave according to the second waveform diagram, and solving the stress at the flange under the standard bolt preload according to the acoustic elastic model and the second acoustic time difference; applying force to the flange according to a fixed torque gradient increment by a torque wrench, acquiring a third waveform diagram of the ultrasonic excitation wave through the flange under each stress loading by the circular array ultrasonic sensor, acquiring a third acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave according to the third waveform diagram, and solving the stress at the flange under different stress loadings according to the acoustic elastic model and the third acoustic time difference.

[0006] In a second aspect, the embodiments of the present application disclose a flange sealing surface stress detection device based on a circular array ultrasonic sensor, which comprises the following components: an electronic device, a bolt, a circular array ultrasonic sensor, a flange and a sealing gasket with a strain gauge sensor; the flange comprises an upper flange and a lower flange and is fixedly connected by the bolt; the circular array ultrasonic sensor is arranged above the upper flange, and the sealing gasket with the strain gauge sensor is arranged between the upper flange and the lower flange; the circular array ultrasonic sensor is connected with the electronic device and is used for transmitting the detected waveform signal to the electronic device for processing.

[0007] Through the technical solutions disclosed in the embodiments of the present application, the embodiments of the present application adopt a circular array ultrasonic sensor, 8 sensing units complete ultrasonic excitation and reception from 8 circumferential directions, and can capture stress distribution characteristics of a flange sealing surface in all directions. Through accurate calculation of acoustic time difference under zero stress state, standard pre-tightening force state and gradient load state, combined with an acoustic-elastic model, stress values of the flange under different working conditions can be quantitatively obtained. By comparing multiple sets of stress data under zero stress, standard pre-tightening force and gradient load, the transmission law and distribution uniformity of the bolt pre-tightening force on the sealing surface can be clearly presented, and local stress concentration areas caused by improper bolt tightening sequence, flange surface deflection and other factors can be accurately identified, potential leakage channels can be found in advance, early failure risks caused by uneven stress distribution can be eliminated from the root cause, and the reliability and service life of the flange sealing structure can be greatly improved. The attenuation trend of the bolt load can be grasped in real time, and a warning can be given before the stress value approaches the lower limit. At the same time, through stress change analysis under gradient load, the bolt pre-tightening force application process can be optimized, the most reliable sealing effect can be achieved under the lowest bolt load, and the sealing safety and equipment energy efficiency are taken into account. Therefore, through deep integration of acoustic detection and mechanical model, the embodiments of the present application realize detection of stress distribution of the flange sealing surface under different working conditions, potential leakage channels can be found in advance, early failure risks caused by uneven stress distribution can be eliminated from the root cause, and the reliability and service life of the flange sealing structure can be greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 A structural schematic diagram of a flange sealing surface stress detection device based on a circular array ultrasonic sensor is provided for the embodiments of the present application.

[0009] Figure 2 A structural schematic diagram of a circular array ultrasonic sensor is provided for the embodiments of the present application.

[0010] Figure 3 A detection schematic diagram of a circular array ultrasonic sensor and a strain gauge on a flange sealing area is provided for the embodiments of the present application.

[0011] Figure 4 A structural schematic diagram of a flange sealing surface stress detection device based on a circular array ultrasonic sensor is provided for the embodiments of the present application. DETAILED DESCRIPTION

[0012] In order to further clarify the technical means and effects taken by the present application to achieve the predetermined inventive purpose, the specific implementation, structure, features and effects of a flange sealing surface stress detection method and device based on a circular array ultrasonic sensor according to the present application are described in detail as follows. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The specific implementation of a flange sealing surface stress detection method and device based on a circular array ultrasonic sensor provided by the present application is specifically described below with reference to the accompanying drawings.

[0014] Please refer to Figure 1 , Figure 1 The flowchart of a flange sealing surface stress detection method based on a circular array ultrasonic sensor provided by an embodiment of the present application is shown in the figure. The method comprises the following steps:

[0015] Step S101, obtain the first waveform diagram of the ultrasonic excitation wave through the flange under zero stress state by the circular ring array ultrasonic sensor, obtain the first acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave according to the first waveform diagram, and solve the stress at the flange under zero stress state according to the acoustic elastic model and the first acoustic time difference.

[0016] Among them, the circular ring array ultrasonic sensor is composed of 8 ultrasonic sensing units arranged in a circle and arranged in 8 directions of the circumference of the flange.

[0017] Specifically, the circular ring array ultrasonic sensor is composed of 8 ultrasonic sensing units, which are uniformly arranged in a circle, and the overall outer diameter matches the outer diameter of the sealing surface of the flange to be detected. Specifically, the 8 ultrasonic sensing units are fixed in 8 directions of the circumference of the flange, which can be adsorbed on the surface of the flange through the magnetic fixing seat, to ensure that the sensing units are closely attached to the flange, and the attachment surface is coated with ultrasonic coupling agent to reduce the reflection loss of the acoustic wave.

[0018] Furthermore, when testing the stress of the flange under zero-stress conditions, first remove all bolts on the flange, clean the flange sealing surface to ensure it is free of oil and impurities, and arrange the annular array ultrasonic sensor on the surface of the upper flange as described above. The annular array ultrasonic sensor is connected to a signal acquisition instrument. The signal acquisition instrument sequentially sends excitation signals to each ultrasonic sensing unit of the annular array ultrasonic sensor. When each ultrasonic sensing unit is excited, it only receives the ultrasonic signal from the ultrasonic sensing unit in the opposite direction. Eight sets of first waveform diagrams of ultrasonic excitation waves passing through the flange are recorded. Each set of first waveform diagrams is acquired three times, and the average value of the three sets of first waveform diagrams is taken to reduce noise interference.

[0019] Furthermore, in calculating the first acoustic time difference, linear interpolation is used to increase the number of sampling points from 1024 to 10240 on the first waveform, improving the time resolution. Then, a cross-correlation algorithm is used to calculate the first acoustic time difference between the transmitted and received ultrasonic waves. Specifically, the transmitted and received signals are first converted to the frequency domain using a Fast Fourier Transform (FFT), and the cross-power spectrum function is calculated. A Hanning window is used as a weighting function to reduce noise. Then, an inverse Fast Fourier Transform is performed to obtain the cross-correlation function. The time difference corresponding to the peak position of the cross-correlation function is the first acoustic time difference, denoted as . .

[0020] Furthermore, the first sound time difference Substitute into the acoustic elasticity model (K is the acoustoelastic coefficient, calibrated through a tensile test on a zero-stress specimen; for example, the K value for a 304 stainless steel flange is approximately 2.3 MPa / ns). The stress at the flange under zero stress state is calculated. ,at this time The theoretical value should be close to 0, and the deviation should be controlled within ±0.5MPa.

[0021] Furthermore, as an optional embodiment of the present invention, before obtaining the first waveform of the ultrasonic excitation wave passing through the flange under zero stress state by means of the circular array ultrasonic sensor, the method further includes the step of preparing the circular array ultrasonic sensor; wherein, eight ultrasonic sensing units are arranged in eight directions around the circumference of the flange, and adjacent ultrasonic sensing units are bonded together by polyurethane foam double-sided adhesive.

[0022] Specifically, such as Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of a circular array ultrasonic sensor provided in an embodiment of the present invention. The circular array ultrasonic sensor 1 has 8 ultrasonic sensing units 10 arranged in a circular array around its circumference, and adjacent ultrasonic sensing units 10 are bonded to each other; the central region of the circular array ultrasonic sensor 1 is filled with epoxy sound-absorbing material 11.

[0023] Further, as an optional embodiment of the present application, the ultrasonic sensing unit 10 comprises: a wedge 100, a piezoelectric element 101, and a backing block 102 poured above the piezoelectric element 101; the upper surface of the wedge 100 is outwardly inclined to the bottom, forming an angle α with the horizontal plane, and the lower surface of the wedge 100 is horizontal; the wedge 100, the piezoelectric element 101, and the backing block 102 are sequentially fixed and connected together from bottom to top. The piezoelectric element 101 is adhered to the upper surface of the wedge 100 by epoxy resin. Electrode leads are led out through the piezoelectric element 101. The electrode leads include a positive electrode lead 1010 and a negative electrode lead 1011, one end of the positive electrode lead 1010 is connected to the upper surface of the piezoelectric element 101, and the other end is led out to the periphery of the ultrasonic sensing unit 10; one end of the negative electrode lead 1011 is connected to the lower surface of the piezoelectric element 101, and the other end is led out to the periphery of the ultrasonic sensing unit 10.

[0024] Specifically, in the present embodiment, the eight ultrasonic sensing units 10 are the same in structure and size, and are arranged in a circular ring array on the circumference of the flange plate, symmetrically with each other; the wedge 100 is provided to provide an incident angle for the ultrasonic wave excited by the piezoelectric element 101, specifically: by setting the upper surface of the wedge 100 to be outwardly inclined to the bottom, the piezoelectric element 101 above the wedge 100 can also be inclined, when the piezoelectric element 101 of one of the ultrasonic sensing units 10 is excited by an electrical signal, it can emit an excitation ultrasonic wave 30 signal perpendicular to the direction of the surface of the piezoelectric element 101, i.e. the upper surface of the wedge 100, the emitted excitation ultrasonic wave 30 signal enters the flange plate 20 of the detection flange at an inclined angle, is then reflected back into the flange plate 20 when encountering the gasket 21, and is finally received by the piezoelectric element 101 of the ultrasonic sensing unit 10 in the opposite direction which is also inclined; therefore, when the flange is detected, the excitation ultrasonic wave of one of the ultrasonic sensing units 10 is received by the ultrasonic sensing unit 10 in the opposite direction, and the eight ultrasonic sensing units 10 sequentially excite and receive ultrasonic waves, which can realize the detection of the stress in eight direction dimensions of the local sealing area of the flange, and obtain the stress distribution in the eight directions, compared with the prior art, the stress distribution of the sealing area of the flange can be effectively detected.

[0025] Further, the wedge described above in the present embodiment can be an eighth of a circular ring column wedge with an inclined angle, and the piezoelectric element 101 and the backing block can be an eighth of a circular ring piezoelectric element and backing block.

[0026] Further, the embodiment of the present application fills the epoxy sound-absorbing material 11 in the central region of the circular ring array ultrasonic sensor 1, which on the one hand ensures the integrity and stability of the circular ring array ultrasonic sensor 1, and on the other hand reduces the interference of stray sound waves between the ultrasonic sensor unit 10 arrays, and improves the detection accuracy; and the backing block 102 is used to absorb the excess sound wave vibration, reduce the ringing effect of the piezoelectric array element, and improve the detection accuracy.

[0027] Further, in order to isolate the sound field interference between the connected ultrasonic sensor units 10 and improve the detection accuracy, the adjacent ultrasonic sensor units 10 are bonded to each other by the polyurethane foam double-sided adhesive.

[0028] Further, in order to ensure the integrity and stability of the circular ring array ultrasonic sensor 1 and reduce the stray sound wave crosstalk between the ultrasonic sensor unit 10 arrays and improve the detection accuracy, the epoxy sound-absorbing material 11 is filled in the central gap formed by all the ultrasonic sensor units 10. The central region of the circular ring array ultrasonic sensor 1 is cylindrical in shape, and the region opposite to the wedge block 100 is a circular truncated cone shape.

[0029] Further, in order to make the sound field of the piezoelectric array element 101 better propagate into the wedge block 100 and then propagate into the detected flange, and improve the detection accuracy, the lower surface of the piezoelectric array element 101 and the upper surface of the wedge block 100 are bonded together by epoxy resin.

[0030] Further, in the present embodiment, by setting the positive electrode lead 1010 and the negative electrode lead 1011, an electric signal can be applied to the piezoelectric array element 101 for excitation, or an electric signal can be received from the piezoelectric array element 101 during detection.

[0031] Further, as an optional embodiment of the present application, in the first waveform diagram of the ultrasonic excitation wave through the flange under the zero stress state obtained by the circular ring array ultrasonic sensor, the first acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave is obtained according to the first waveform diagram, and before the stress at the flange under the zero stress state is solved according to the acoustic-elastic model and the first acoustic time difference, the method further comprises: preparing a zero stress test block which is completely the same as the material and process of the flange; obtaining the acoustic-elastic model between the stress change amount of the zero stress test block and the acoustic time difference of the excited ultrasonic wave propagation through the tensile experiment, and the acoustic-elastic model is wherein K is the acoustic-elastic coefficient, is the acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave of the zero stress test block, is the stress received by the zero stress test block.

[0032] Specifically, the material of the zero-stress test block is consistent with the flange plate, and the same forging process and heat treatment process as the flange plate are adopted to ensure that the mechanical properties of the zero-stress test block are consistent with the flange plate. Then the zero-stress test block is processed into a standard tensile specimen, and after processing, nondestructive testing is performed to ensure that the zero-stress test block is free of internal defects. Next, the zero-stress test block is installed in the upper and lower clamps of the electronic universal testing machine, with the test block axis aligned with the stress axis of the testing machine; two opposite ultrasonic sensor units (transmitting and receiving units) of a circular array ultrasonic sensor are attached on both sides of the gauge section of the zero-stress test block, and ultrasonic coupling agent is applied to ensure close fitting. Then the tensile load is gradually increased in accordance with the gradient of 10kN, from 0kN to 80kN, a total of 9 load levels; at each load level, after the load is stable, the ultrasonic emission wave and receiving wave signals are collected, and the stress value displayed by the testing machine is recorded; 3 sets of data are collected at each load level, and the average value is taken. Finally, the acoustic time difference at each load level is calculated , with the corresponding stress σ as the vertical coordinate, and the test as the horizontal coordinate, linear fitting is performed by the least square method to obtain the acoustic-elasticity model , wherein K is the fitting slope (i.e. the acoustic-elasticity coefficient). For example, the 304 stainless steel test block fitting obtains K=2.3MPa / ns, and the model expression is . After obtaining the acoustic-elasticity model, it can be used to calculate the stress in the zero-stress state, the stress under the standard pre-tightening force of the bolt, and the stress under different load states.

[0033] Further, as an optional embodiment of the present application, the acoustic time difference is calculated in the following manner: first, the number of sampling points is increased by linear interpolation method, and then the cross-correlation algorithm is used to solve the acoustic time difference.

[0034] Specifically, it is assumed that the original sampling rate of the ultrasonic signal acquisition system of the embodiment of the present application is 100MHz, the sampling interval T=10ns, the number of original sampling points is 1024, and the signal length is 10us. Linear interpolation is used to insert 9 interpolation points between every two adjacent original sampling points, so that the sampling interval is shortened to 1ns and the number of sampling points is increased to 10240. The interpolation formula is:

[0035] , wherein , is the amplitude of the adjacent original sampling point, , is the original sampling point index, and i is the interpolation point index.

[0036] ​Further, as an optional embodiment of the present application, the cross-correlation algorithm comprises: placing the circular array ultrasonic sensor above the flange to obtain ultrasonic emission waves and ultrasonic reception waves of the ultrasonic sensing units of the circular array ultrasonic sensor; converting the ultrasonic emission waves and the ultrasonic reception waves into a frequency domain by using fast Fourier transform, and calculating cross-power spectrum functions of the ultrasonic emission waves and the ultrasonic reception waves; weighting the cross-power spectrum functions by using a weighting function to obtain weighted cross-power spectrum functions, the weighting function being used to weaken external noise and reverberation, enhance sound source signals and sharpen peaks of the cross-correlation functions; converting the weighted cross-power spectrum functions into generalized cross-correlation functions by using inverse fast Fourier transform; and performing peak detection on the generalized cross-correlation functions to obtain acoustic time differences.

[0037] Specifically, assuming that the ultrasonic emission waves and the ultrasonic reception waves of the ultrasonic sensing units of the circular array ultrasonic sensor are and respectively, they are represented as follows: (1)

[0038] In the above formula, s(t) is a sound source signal. α1 and α2 are attenuation coefficients of ultrasonic waves. and are external noises. and respectively represent times corresponding to the ultrasonic emission waves and times corresponding to the ultrasonic reception waves.

[0039] Further, and are represented as: (2)

[0040] Further, substituting formula (1) into formula (2), the following formula is obtained: (4)

[0041] wherein s(t), and are not correlated with each other, formula (4) can be simplified as the following formula: (5)

[0042] According to the cross-correlation property, , the maximum value is taken.

[0043] Further, the cross-correlation function is FFT transformed into a frequency domain to obtain a cross-power spectrum function, the cross-power spectrum function is weighted, and then the weighted cross-power spectrum function is IFFT transformed into a time domain to obtain a generalized cross-correlation function, which is shown in the following formula: (6)​

[0044] In the above formula, is the cross power spectrum function of the two signals, is a weighting function.

[0045] Finally, peak detection is performed on the above generalized cross function, wherein the time delay corresponding to the maximum peak is the acoustic time difference Δt between the ultrasonic transmission wave and the ultrasonic receiving wave.

[0046] In step S102, a second waveform diagram of an ultrasonic excitation wave passing through the flange under the standard bolt preload is obtained by the circular ring array ultrasonic sensor, a second acoustic time difference between the ultrasonic transmission wave and the ultrasonic receiving wave is obtained according to the second waveform diagram, and the stress at the flange under the standard bolt preload is solved according to the acoustic-elastic model and the second acoustic time difference.

[0047] Specifically, the embodiment of the present application first queries the mechanical design manual to determine the standard bolt preload (such as 120 kN) according to the specifications of the flange and the bolt (such as M20 bolt, 8.8 grade), tightens the 8 bolts in diagonal order using a torque wrench, ensures that the preload of each bolt reaches the standard bolt preload, and stands still for 10 minutes after tightening to wait for the stress to stabilize. Then, the position of the circular ring array ultrasonic sensor is kept unchanged, the above waveform diagram acquisition process is repeated, a second waveform diagram of an ultrasonic excitation wave passing through the flange under the standard bolt preload is obtained, and the average value is obtained by collecting 3 times. Finally, the second acoustic time difference is calculated in the same way as in the zero stress state , and the stress at the flange under the standard bolt preload is obtained by substituting the acoustic-elastic model , the stress values of the 8 directions are recorded, and the stress distribution trend is preliminarily judged.

[0048] Further, as an optional embodiment of the present application, after obtaining the second waveform diagram of the ultrasonic excitation wave passing through the flange under the standard bolt preload by the circular ring array ultrasonic sensor, obtaining the second acoustic time difference between the ultrasonic transmission wave and the ultrasonic receiving wave according to the second waveform diagram, and solving the stress at the flange under the standard bolt preload according to the acoustic-elastic model and the second acoustic time difference, the method further comprises: tightening the upper flange and the lower flange with 8 bolts, and setting the bolt preload to the standard bolt preload; arranging the circular ring array ultrasonic sensor above the upper flange, arranging the gasket in the middle of the upper flange and the lower flange, and arranging the strain gauge sensor in different regions of the gasket in the middle of the upper flange and the lower flange and within the spacing of the two bolt holes; taking the stress of each region of the strain gauge sensor as the basic range of the stress size on the corresponding region area; and judging the uniformity of the stress distribution in each region of the flange according to the calculated stress and the basic range of the strain gauge sensor obtained from the 8 directional dimensions of the circular ring array ultrasonic sensor.

[0049] Specifically, as​Figure 3 As shown, Figure 3 A schematic diagram of a circular array ultrasonic sensor and a strain gauge for detecting a sealing area of a flange plate is provided in an embodiment of the present application, Figure 3 In the embodiment, a sealing gasket 303 for mounting a strain gauge sensor is arranged between the upper flange plate 301 and the lower flange plate 302, and a waveform diagram of an excitation sound wave 304 and a received sound wave 305 detected by the circular array ultrasonic sensor 1 is shown. In the embodiment, the upper flange plate 301 and the lower flange plate 302 are selected, the bolts are inserted into the flange bolt holes in diagonal order, the torque wrench is used to set the bolt pretightening force to a standard pretightening force, and the torque detector is used to review the pretightening force of each bolt after tightening. The sealing gasket is made of butyl rubber, and the strain gauges are attached to the areas corresponding to the bolt hole spacing of the flange plate (a total of 8 areas). The strain gauges are attached by 502 glue, and are cured for 2 hours after attachment. The leads of the strain gauges are led to the data acquisition instrument, and the leads are ensured to be unwound and in good contact during connection.

[0050] Further, the data acquisition instrument is started, the stress values of the areas where the 8 strain gauges are located are collected, 10 groups of data are collected for each area, and the average value is taken as the basic range calibration value σ of the stress size on the area. Then, according to the second acoustic time difference of the bolt under the standard pretightening force in the above embodiment of the present application, the stress values σ of the 8 directions are calculated according to the acoustic elastic model. Finally, the deviation rate of the ultrasonic detection stress in each direction and the calibration stress of the corresponding area strain gauge is calculated, the deviation rate = |σ - σ| / σ × 100%, when the deviation rate of all directions ≤ the first threshold value, and the coefficient of variation (standard deviation / average value) of the stress values of the 8 directions ≤ the second threshold value, it is determined that the stress distribution in each area of the flange plate is uniform; otherwise, factors such as bolt tightening order and flange flatness need to be analyzed and adjusted for re-detection. The first threshold value can be 5%, and the second threshold value can be 3%.

[0051] In step S103, the torque wrench is used to apply force to the flange plate according to a fixed torque gradient increment, the third waveform graph of the ultrasonic excitation wave passing through the flange plate under each stress loading is obtained by the circular array ultrasonic sensor, the third acoustic time difference between the ultrasonic emission wave and the ultrasonic receiving wave is obtained according to the third waveform graph, and the stress at the flange plate under different stress loadings is solved according to the acoustic elastic model and the third acoustic time difference.

[0052] Specifically, the embodiment of the present application takes 10% of the standard bolt preload as the fixed torque gradient increment (such as 12kN), gradually increases the bolt preload through the torque wrench, starts from 50% of the standard bolt preload (60kN), and ends at 150% (180kN), a total of 11 load levels are set. Then, after applying a load level, it is static for 5 minutes, waits for the stress to be stable, collects the third waveform diagram of the ultrasonic excitation wave passing through the flange under the load, collects 3 times for each load level to ensure data repeatability. Finally, for the third waveform diagram of each load level, calculate the third acoustic time difference , solve the corresponding stress by combining the acoustic-elastic model record the values of the 8 directions under different loads to form a "load-stress-direction" three-dimensional data matrix, which is used to analyze the variation law and distribution uniformity of stress with load.

[0053] It is worth noting that the setting of load levels can also be determined according to the actual scene, and the embodiment of the present application does not limit it here.

[0054] Through the technical scheme disclosed in the embodiment of the present application, the embodiment of the present application adopts a circular array ultrasonic sensor, and 8 sensing units complete ultrasonic excitation and reception from 8 directions around the circumference, which can capture the stress distribution characteristics of the sealing surface of the flange in all directions. Through accurate calculation of the acoustic time difference under the conditions of zero stress, standard preload and gradient load, and combining the acoustic-elastic model, the stress values of the flange under different working conditions can be quantitatively obtained. By comparing multiple sets of stress data under zero stress, standard preload and gradient load, the transmission law and distribution uniformity of the bolt preload on the sealing surface can be clearly presented, the local stress concentration area caused by improper tightening sequence of the bolt, flange surface deflection and other factors can be accurately identified, potential leakage channels can be found in advance, and early failure risks caused by uneven stress distribution can be eliminated from the root cause, greatly improving the reliability and service life of the flange sealing structure. The attenuation trend of the bolt load can be grasped in real time, and a warning can be given before the stress value approaches the lower limit. At the same time, through the stress variation analysis under the gradient load, the bolt preload application process can be optimized to achieve the most reliable sealing effect under the lowest bolt load, taking into account the sealing safety and equipment efficiency. Therefore, through the deep integration of acoustic detection and mechanical model, the embodiment of the present application realizes the detection of the stress distribution of the flange sealing surface under different working conditions, can find potential leakage channels in advance, eliminate early failure risks caused by uneven stress distribution from the root cause, and greatly improve the reliability and service life of the flange sealing structure.

[0055] As shown in Figure 4 , Figure 4A structure schematic view of a flange sealing surface stress detection device based on a circular array ultrasonic sensor provided by the embodiment of the present application, comprising: an electronic device 401, a bolt 402, a circular ring ultrasonic sensor 1, a flange plate, and a sealing gasket 303 with a strain gauge sensor; the flange plate comprises an upper flange plate 301 and a lower flange plate 302, and is fixedly connected through the bolt 402.

[0056] The circular ring ultrasonic sensor 1 is arranged above the upper flange plate 301, and the sealing gasket 303 with the strain gauge sensor is arranged between the upper flange plate 301 and the lower flange plate 302; the circular ring ultrasonic sensor 1 is connected with the electronic device 401, and is used for transmitting the detected waveform signal to the electronic device 401 for processing.

[0057] Further, as an optional embodiment of the present application, the circular ring ultrasonic sensor is composed of 8 ultrasonic sensing units arranged in a circle, each ultrasonic sensing unit comprises a wedge, a piezoelectric array element, and a backing block poured above the piezoelectric array element, an electrode lead wire is led out through the piezoelectric array element, and the piezoelectric array element is adhered to the upper surface of the wedge through epoxy resin; the upper surface of the wedge is outwardly inclined to the bottom and forms an inclination angle with the horizontal plane, and the lower surface of the wedge is horizontal; the circular ring ultrasonic sensor is arranged above the upper flange plate, one of the ultrasonic sensing units excites ultrasonic waves, and the ultrasonic sensing unit in the opposite direction receives the ultrasonic waves; the 8 ultrasonic sensing units excite and receive signals in turn, so as to realize 8-directional dimension detection of the stress of the flange sealing area.

[0058] It should be noted that the flange sealing surface stress detection device based on the circular array ultrasonic sensor provided by the embodiment of the present application is based on the same application concept as the flange sealing surface stress detection method based on the circular array ultrasonic sensor provided by the embodiment of the present application, so the specific implementation of this embodiment can be referred to the foregoing implementation of the flange sealing surface stress detection method based on the circular array ultrasonic sensor, and has the same or similar beneficial effects, and the repeated parts will not be described herein.

[0059] It should be noted that: the above-mentioned embodiment sequence of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0060] Each embodiment in the specification is described in a progressive manner, and the same and similar parts of each embodiment can be referred to each other, and each embodiment mainly describes the differences from other embodiments.

Claims

1. A method for detecting stress on a flange sealing surface based on a circular array ultrasonic sensor, characterized in that, The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor includes: The first waveform of the ultrasonic excitation wave passing through the flange under zero stress is obtained by a circular array ultrasonic sensor. The first acoustic time difference between the ultrasonic transmitted wave and the ultrasonic received wave is obtained based on the first waveform. The stress at the flange under zero stress is solved based on the acoustoelastic model and the first acoustic time difference. The circular array ultrasonic sensor consists of 8 ultrasonic sensing units arranged in a circle and respectively arranged in 8 directions around the circumference of the flange. The second waveform of the ultrasonic excitation wave passing through the flange under the standard preload of the bolt is obtained by a circular array ultrasonic sensor. The second acoustic time difference between the ultrasonic transmitted wave and the ultrasonic received wave is obtained according to the second waveform. The stress at the flange under the standard preload of the bolt is solved according to the acoustoelastic model and the second acoustic time difference. The flange is subjected to a fixed torque gradient increment using a torque wrench. The third waveform of the ultrasonic excitation wave passing through the flange under each stress loading is obtained by the circular array ultrasonic sensor. The third acoustic time difference between the ultrasonic transmitted wave and the ultrasonic received wave is obtained based on the third waveform. The stress at the flange under different stress loading conditions is solved based on the acoustoelastic model and the third acoustic time difference.

2. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 1, characterized in that, Before acquiring the first waveform of the ultrasonic excitation wave passing through the flange under zero stress state using a circular array ultrasonic sensor, the method further includes: The steps for preparing the circular array ultrasonic sensor; The eight ultrasonic sensing units are arranged in eight directions around the circumference of the flange, and adjacent ultrasonic sensing units are bonded together with polyurethane foam double-sided adhesive.

3. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 2, characterized in that, One of the ultrasonic sensing units in the circular array ultrasonic sensor excites ultrasonic waves, and the ultrasonic sensing unit in the opposite direction receives ultrasonic waves. The eight ultrasonic sensing units sequentially excite and receive ultrasonic waves to detect the stress in the sealing area of ​​the flange in eight dimensions.

4. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 2, characterized in that, Each ultrasonic sensing unit includes a wedge, a piezoelectric element, and a backing block cast above the piezoelectric element. Electrode wires are led out through the piezoelectric element, which is bonded to the upper surface of the wedge with epoxy resin. The upper surface of the wedge is inclined outward and downward, forming an angle with the horizontal plane, while the lower surface of the wedge is horizontal. The electrode wires include a positive wire and a negative wire. One end of the positive wire is connected to the upper surface of the piezoelectric array element, and the other end is led out to the periphery of the ultrasonic sensing unit. One end of the negative wire is connected to the lower surface of the piezoelectric array element, and the other end is led out to the periphery of the ultrasonic sensing unit.

5. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 2, characterized in that, After obtaining a second waveform diagram of the ultrasonic excitation wave passing through the flange under the standard bolt preload using a circular array ultrasonic sensor, obtaining a second acoustic time difference between the ultrasonic transmitted wave and the ultrasonic received wave based on the second waveform diagram, and solving for the stress at the flange under the standard bolt preload using the acoustoelastic model and the second acoustic time difference, the method further includes: Tighten the upper and lower flanges with 8 bolts, and set the bolt preload to the standard bolt preload. The circular array ultrasonic sensor is arranged above the upper flange, a sealing gasket is arranged between the upper flange and the lower flange, and strain gauge sensors are arranged in different areas of the sealing gasket between the upper flange and the lower flange and within the distance between the two bolt holes. The stress of the strain gauge sensor in each region is used as the basic range of stress magnitude over the corresponding region area for calibration. The stress obtained by calculating the second acoustic time difference in the eight directional dimensions of the circular array ultrasonic sensor and the basic range calibration are used to determine the uniformity of stress distribution in each region of the flange.

6. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 1, characterized in that, Before acquiring a first waveform diagram of the ultrasonic excitation wave passing through the flange under zero stress state using a circular array ultrasonic sensor, obtaining a first acoustic time difference between the ultrasonic transmitted wave and the ultrasonic received wave based on the first waveform diagram, and solving for the stress at the flange under zero stress state based on the acoustoelastic model and the first acoustic time difference, the method further includes: Prepare a zero-stress test block with the same material and process as the flange; The acoustoelastic model between the stress change and the acoustic time difference of the excitation ultrasonic wave propagation in the zero-stress specimen was obtained through tensile testing. The acoustoelastic model is as follows: Where K is the acoustoelastic coefficient, Δt is the acoustic time difference between the ultrasonic emitted wave and the ultrasonic received wave of the zero-stress test block, and the... The stress experienced by the zero-stress specimen is denoted as .

7. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 6, characterized in that, The acoustic time difference is calculated as follows: first, the number of sampling points is increased by linear interpolation, and then the acoustic time difference is solved by cross-correlation algorithm.

8. The method for detecting flange sealing surface stress based on a circular array ultrasonic sensor according to claim 7, characterized in that, The cross-correlation algorithm includes: The circular array ultrasonic sensor is placed above the flange to obtain the ultrasonic transmitted wave and ultrasonic received wave from the ultrasonic sensing unit of the circular array ultrasonic sensor. The ultrasonic transmitted wave and ultrasonic received wave are converted to the frequency domain using Fast Fourier Transform, and the cross power spectrum function of the ultrasonic transmitted wave and ultrasonic received wave is calculated. The cross-power spectrum function is weighted by a weighting function to obtain a weighted cross-power spectrum function. The weighting function is used to reduce external noise and reverberation, enhance the sound source signal and sharpen the peak value of the cross-correlation function. The weighted cross-power spectrum function is converted into a generalized cross-correlation function using the inverse fast Fourier transform; Peak detection is performed on the generalized cross-correlation function to obtain the acoustic time difference.

9. A flange sealing surface stress detection device based on a circular array ultrasonic sensor, characterized in that, include: Electronic equipment, bolts, annular ultrasonic sensors, flanges, and gaskets with strain gauge sensors; the flanges include an upper flange and a lower flange, which are fixedly connected by bolts; The annular ultrasonic sensor is arranged above the upper flange, and the gasket with strain gauge sensor is arranged between the upper flange and the lower flange; the annular ultrasonic sensor is connected to an electronic device to transmit the detected waveform signal to the electronic device for processing.

10. The flange sealing surface stress detection device based on a circular array ultrasonic sensor according to claim 9, characterized in that, The annular ultrasonic sensor consists of eight ultrasonic sensing units arranged in a circle. Each ultrasonic sensing unit includes a wedge, a piezoelectric element, and a backing block cast above the piezoelectric element. Electrode wires are led out through the piezoelectric element, which is bonded to the upper surface of the wedge with epoxy resin. The upper surface of the wedge is inclined outward and downward, forming an angle with the horizontal plane, while the lower surface of the wedge is horizontal. The annular ultrasonic sensor is arranged above the upper flange. One ultrasonic sensing unit excites ultrasonic waves, and the ultrasonic sensing unit in the opposite direction receives ultrasonic waves. The eight ultrasonic sensing units excite and receive signals in sequence to realize the detection of stress in eight dimensions of the flange sealing area.

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