Acoustic emission source location method based on three-dimensional anisotropic wave velocity model

Abstract

The present invention discloses a method for locating an acoustic emission source based on a three-dimensional anisotropic wave velocity model. The method adopts at least two sensor arrays arranged at any position in a monitoring area, and adopts a genetic algorithm to iteratively solve the spatial position coordinates of the acoustic emission source according to the known spatial position coordinates of the sensors and the arrival time of received P waves. The method does not need to measure the propagation speed of the P wave in the anisotropic medium, thereby avoiding the influence of the P wave measurement error on the positioning result, and realizing the precise positioning of the acoustic emission source of the three-dimensional anisotropic material.

Description

Technical Field

[0001] The invention relates to the technical field of acoustic emission source positioning, and in particular to an acoustic emission source positioning method based on a three-dimensional anisotropic wave velocity model. Background Art

[0002] Acoustic emission source localization is a necessary means to determine the initiation location and development trend of material damage. In the past few decades, research on acoustic emission source localization has achieved rich results. However, most methods require the pre-determination of the propagation speed of the acoustic emission signal inside the material. The accuracy of the speed measurement is closely related to the positioning accuracy.

[0003] There are many problems in the measurement of wave velocity in actual engineering:

[0004] (1) The uncertainty of the tectonic stress concentration area causes the microseismic and acoustic emission areas to be different from the pre-measured velocity areas;

[0005] (2) The material samples taken from the area cannot accurately express the material structure of the test area;

[0006] (3) The measurement itself is highly random. Manual operation, probes, etc. can cause errors, which may lead to positioning results outside the allowable error range obtained by the positioning method based on speed measurement conditions.

[0007] Many scholars have explored methods for locating acoustic emission sources without velocity measurement, but most of these studies are currently based on single velocity models, layered velocity models, and weakly anisotropic velocity models. Although they have good positioning effects and can effectively avoid the influence of velocity measurement errors on positioning results, for non-continuous materials, due to natural defects such as microcracks and pores, microseismic and acoustic emission signals are prone to diffusion, scattering, and attenuation during propagation inside the material. Their propagation speeds show large differences in all directions, and there are large errors in the positioning results.

[0008] In view of this, some scholars proposed a method for locating acoustic emission of anisotropic plates under non-velocimetry conditions. This method arranges 6 sensors into 2 arrays of sensor arrays in the form of right-angled isosceles triangles, and realizes the location of sound sources in anisotropic plates by solving nonlinear equations. The applicability and accuracy of this method are verified on aluminum plates and fiber composite reinforced plates. In subsequent studies, the sensor arrangement form is extended from right-angled isosceles triangles to any right-angled triangle, any triangle and "Z" shape, which can locate the acoustic emission source of anisotropic plates under non-velocimetry conditions (this method can only be used to determine the sound source of planar structures or two-dimensional structures). However, for three-dimensional anisotropic materials, when the sound wave velocity is unknown, it is still a challenging task to accurately locate the acoustic emission source with a small number of sensors. Therefore, it is necessary to propose a method for locating acoustic emission sources of three-dimensional anisotropic wave velocity models under non-velocimetry conditions. Summary of the invention

[0009] The purpose of the present invention is to provide a method for locating an acoustic emission source based on a three-dimensional anisotropic wave velocity model. The method can accurately locate the acoustic emission source of a three-dimensional anisotropic medium without pre-determining the acoustic emission signal wave velocity through a specially arranged sensor array and its structure, so as to overcome the shortcomings of the prior art.

[0010] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for locating an acoustic emission source based on a three-dimensional anisotropic wave velocity model, wherein the method deploys at least two sensor arrays at any position in a monitoring area, and uses a genetic algorithm to iteratively solve the spatial position coordinates of the acoustic emission source according to the known spatial position coordinates of the sensors and the arrival time of the received P wave; the method does not need to measure the propagation speed of the P wave in the anisotropic medium, thereby avoiding the influence of the P wave measurement error on the positioning result, and realizing the precise positioning of the acoustic emission source of the three-dimensional anisotropic material.

[0011] As a further solution of the present invention: the sensor array is distributed in a regular tetrahedron, and corresponding sensors in the sensor array are located at the endpoints of the regular tetrahedron.

[0012] As a further solution of the present invention: the distance D between the acoustic emission source S and the corresponding sensor array C should be greater than the distance L between adjacent sensors in the sensor array C, and the size relationship between the distance D and the distance L is determined by the actual accuracy of locating the acoustic emission source S required.

[0013] As a further solution of the present invention, suppose the sensor arrays are C1, C2...C n , each sensor in the sensor array C1 is C 11 , C 12 , C 13 and C 14 ; Set sensor C 11 , C 21 ……C n1 Set to correspond to sensor arrays C1, C2...C n The main sensor inside; then the acoustic emission signal generated by the acoustic emission source S is on the straight line SC 11 The propagation velocity V1 on the array is called the main velocity in the array; let the straight line SC 11 The inclination angle is α1, and the direction angle is β1, then the straight line SC 11 The direction vector can be expressed as:

[0014]

[0015] Straight Line C 12 C 11 , C 13 C 11 and C14 C 11 The direction vector can be expressed as:

[0016]

[0017] Where: (x i1 ,y i1 ,z i1 ) is sensor C i1 The three-dimensional space coordinates of

[0018] According to the straight line SC 11 With C 12 C 11 , C 13 C 11 , C 14 C 11 The direction vector of the straight line SC 11 With C 12 C 11 , C 13 C 11 , C 14 C 11 The angle is θ 12 ,θ 13 and θ 14 :

[0019]

[0020] When the distance D between the acoustic emission source S and the sensor array C1 is greater than the distance L between the sensors in the array, the acoustic emission signals received by the same array sensors are set to have the same wave velocity V, and have almost the same frequency and amplitude and a certain time shift. The acoustic emission signals are parallel to each other in the spatial propagation paths, and the wavefronts reaching each sensor are parallel to each other.

[0021] Assume that the signal emitted by the acoustic emission source is transmitted to sensor C in sensor array C1. 11 , C 12 , C 13 and C 14 The times are t1, t2, t3 and t4 respectively, then the acoustic emission signal reaches sensor C 11 With C 12 , C 13 , C 14 The time delay t 12 ,t 13 ,t 14 They are:

[0022]

[0023] Where: is the side length of a regular tetrahedron.

[0024] Solving equation (4) together, we can obtain:

[0025]

[0026] From the above formula, we can get the acoustic emission source S and sensor C 11 The line coordinate inclination is α1, the direction angle is β1 and the acoustic emission signal is in SC 11 The velocity V1 of the propagation direction depends on the time delay t between sensors. 12 , t 13 and t 14 ; Similarly, sensor arrays C2, C3...C n In the figure, the coordinate inclination angles of the line connecting the acoustic emission source S and the sensors C2, C3, ... C are α2, α3, ... α n , direction angles β2, β3, ... β n ;

[0027] Determine the acoustic emission source S and sensor C 11 , C 21 ……C n1 The inclination angles of the connecting line coordinates are α1, α2, ... α n , the direction angles are β1, β2, ... β n And sensor C 21 , C 21 ……C n1 After obtaining the coordinates, the intersection of any two straight lines can be solved by simultaneous solving, which is the coordinate of the acoustic emission source S.

[0028] As a further solution of the present invention: based on the assumption that the propagation paths of microseismic signals between sensors in the same array are parallel to each other, it is found during the solution process that there is no real number solution, that is, the intersection of the two straight lines has no intersection in space; the point (x0, y0, z0) with the shortest distance to the two straight lines is selected as the coordinate of the acoustic emission source S.

[0029] As a further solution of the present invention: the steps of finding the point (x0, y0, z0) with the shortest distance between two straight lines are as follows

[0030] Step 1: Use α1, α2, β1, and β2 to represent the coordinate inclination and direction angles of the corresponding straight lines:

[0031]

[0032] Where: m i =cosα i sinβ i , n i =cosα i cosβ i , p i = sinα i , is a fixed variable of the straight line.

[0033] Step 2: Calculate the distance D1 from (x0, y0, z0) to one of the straight lines:

[0034]

[0035] Where: (x c1 ,y c1 , z c1 ) is the foot of a perpendicular line from (x0, y0, z0), where x c1 =m1K1+x 11 ,y c1 =n1K1+y 11 , z c1 =p1K1+z 11 .

[0036] Step 3: Calculate the distance D2 from (x0, y0, z0) to another straight line:

[0037]

[0038] Where: (x c2 ,y c2 , z c2 ) is the foot of the perpendicular from (x0, y0, z0) to another line, where x c2 =m2K2+x 21 , y c2 =n2K2+y 21 , z c2 =p2K2+z 21 .

[0039] Step 4: Establish the (x0, y0, z0) objective function as follows:

[0040] f(x0,y0,z0)=min(D1+D2) (9)

[0041] Step 5: Use genetic algorithm to iteratively solve the objective function.

[0042] As a further solution of the present invention: based on the assumption that the propagation paths of microseismic signals between sensors in the same array are parallel to each other, it is found during the solution process that there is no real number solution, that is, there is no intersection point between two straight lines in space; the point with the shortest distance between any two adjacent straight lines is first selected, and then the middle of the polyhedron space surrounded by all the points with the shortest distance between any two straight lines is used as the coordinates of the acoustic emission source S.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention verifies the applicability and accuracy of three-dimensional non-continuous media through a specially arranged sensor array and its structure; therefore, under three-dimensional non-velocity measurement conditions, the present invention can realize the positioning of acoustic emission sources of non-continuous media, avoiding the positioning error caused by using a single velocity model in traditional positioning methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of the sensor array arrangement for the three-dimensional acoustic emission source localization method;

[0045] Figure 2 Schematic diagram of the sensor layout within the array. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Example 1, please refer to Figure 1-2 This embodiment provides a method for locating an acoustic emission source based on a three-dimensional anisotropic wave velocity model. The method assumes that a positioning system consists of two sensor arrays and eight sensors, and the spatial distribution positions are as follows: Figure 1 As shown, sensor C 11 , C 12 , C 13 and C 14 Composed of sensor array C1, sensor C 21 , C 22 , C 23 and C 24 The sensor array C2 is composed, and the sensor numbers and coordinates are shown in Table 1. According to the acoustic emission monitoring area and the sensor size used in the actual detection, the sensor spacing in the array is set to 60 mm. Table 2 shows the numbers and coordinates of the 8 proposed acoustic emission sources.

[0048] Table 1 Sensor number and coordinates (mm)

[0049]

[0050] Table 2 Acoustic emission source number and coordinates (mm)

[0051]

[0052] Assume that the acoustic emission source occurs at 0:00:00 on a certain day of a certain year. The main velocity of the acoustic emission signal in the direction of sensor array C1 is SC11 The equivalent wave velocity V1 on the straight line is 5m / ms, and the main velocity in the direction of sensor array C2 is SC 21 The equivalent wave speed on the straight line is V2 = 4m / ms. Table 3 shows the time when each acoustic emission source signal reaches each sensor.

[0053] Table 3 The time when the acoustic emission source signal arrives at each sensor

[0054]

[0055]

[0056] MATLAB programming is used to solve the objective function with a genetic algorithm. The results of positioning according to the actual arrival time of the acoustic emission signal received by the sensor are shown in Table 4, where the positioning error Δδ represents the Euclidean distance between the obtained acoustic emission source coordinates and the proposed acoustic emission source position.

[0057] Table 4 Positioning results (mm)

[0058]

[0059] The results show that when the acoustic emission source positioning method under three-dimensional non-velocimetry conditions is used to locate the acoustic emission source, the eight positioning results all fall near the proposed acoustic emission source, and the positioning point error fluctuations are small in repeated tests, and the discreteness is low, all within the range of 37-55mm, which verifies the applicability and accuracy of the positioning method in three-dimensional non-continuous media. Therefore, the acoustic emission source positioning method under three-dimensional non-velocimetry conditions can realize the positioning of acoustic emission sources in non-continuous media, avoiding the positioning error caused by the use of a single velocity model in traditional positioning methods.

[0060] Embodiment 2: If more than two sensor arrays are used (i.e., if three sensor arrays are used, 12 sensors), the calculation method and process of the relevant parameters of each sensor array are consistent with those of embodiment 1, and the straight line parameter algorithm of the main sensor and the acoustic emission source in each sensor array is also consistent with the embodiment. Then, the nearest points between the straight lines formed by the two main sensors and the acoustic emission sources are calculated respectively (the calculation process is consistent with embodiment 1), and finally the three nearest points are obtained. The middle of the space surrounded by the three nearest points is the acoustic emission source. In order to provide more precision and accuracy, the number of corresponding sensor arrays can be increased so that the space surrounded by the corresponding nearest points is more complete and the position of the acoustic emission source is more accurate.

[0061] Embodiment 3: Based on Embodiment 1, in order to avoid distortion of corresponding sensor data or inability of some sensors to collect accurate signals, the corresponding sensor array may be set to a regular polyhedron structure or a regular polyhedron structure; specifically, a positioning system is set to consist of 2 groups of sensor arrays and 12 sensors (the sensor array is a regular hexahedron structure). In the calculation process, the main sensor of the corresponding sensor array is first determined, and then three sensor signals (three sensor signals with high accuracy) from the other five sensors in the corresponding sensor array are selected, and then the calculation process in Embodiment 1 is followed (the only difference is that the geometric dimensions of the sensors in the sensor array with a regular tetrahedron structure are consistent and the positions correspond; while in this embodiment, the positions and spacings of the four sensors are inconsistent, and this can be achieved by listing mathematical formulas according to the corresponding geometric relationships).

Claims

1. A method for locating an acoustic emission source based on a three-dimensional anisotropic wave velocity model, characterized in that: The method uses at least two sensor arrays deployed at any position in the monitoring area, and uses a genetic algorithm to iteratively solve the spatial position coordinates of the acoustic emission source based on the known spatial position coordinates of the sensor and the arrival time of the received P wave. There is no need to measure the propagation speed of the P wave in the anisotropic medium, thereby avoiding the influence of the P wave measurement error on the positioning result, and realizing the precise positioning of the acoustic emission source of the three-dimensional anisotropic material. The sensor array is distributed in a regular tetrahedron, and corresponding sensors in the sensor array are located at the endpoints of the regular tetrahedron; The distance D between the acoustic emission source S and the corresponding sensor array C should be greater than the distance L between adjacent sensors in the sensor array C; Assume that the sensor arrays are C1, C2, ... n , each sensor in the sensor array C1 is C 11 , C 12 , C 13 and C 14 ; Set sensor C 11 , C 21 ……C n1 Set to correspond to sensor arrays C1, C2...C n The main sensor in the AE source S generates an AE signal on the straight line SC. 11 The propagation velocity V1 on the array is the main velocity; let the straight line SC 11 The inclination angle is α1, and the direction angle is β1, then the straight line SC 11 The direction vector is: Straight Line C 12 C 11 , C 13 C 11 and C 14 C 11 The direction vector is: Where: (x1i, y1i, z1i) is the three-dimensional space coordinate of sensor C1i; According to the straight line SC 11 With C 12 C 11 , C 13 C 11 , C 14 C 11 The direction vector of the straight line SC 11 With C 12 C 11 , C 13 C 11 , C 14 C 11 The angle is θ 12 ,θ 13 and θ 14 : When the distance D between the acoustic emission source S and the sensor array C1 is greater than the distance L between the sensors in the array, the acoustic emission signals received by the same array sensors are set to the same wave velocity V, the propagation paths of the acoustic emission signals in space are parallel to each other, and the wavefronts reaching each sensor are parallel to each other; Assume that the signal emitted by the acoustic emission source is transmitted to sensor C in sensor array C1. 11 , C 12 , C 13 and C 14 The times are t1, t2, t3 and t4 respectively, then the acoustic emission signal reaches sensor C 11 With C 12 , C 13 , C 14 The time delay t 12 ,t 13 ,t 14 They are: Where: is the side length of the regular tetrahedron; Solving equation (4) together, we can obtain: From the above formula, we can get the acoustic emission source S and sensor C 11 The line coordinate inclination is α1, the direction angle is β1 and the acoustic emission signal is in SC 11 The velocity V1 of the propagation direction depends on the time delay t between sensors. 12 ,t 13 and t 14 ; Similarly, sensor arrays C2, C3...C n In the figure, the coordinate inclination angles of the line connecting the acoustic emission source S and the sensors C2, C3, ...C are α2, α3, ... n , direction angles β2, β3, ... β n ; Determine the acoustic emission source S and sensor C 11 , C 21 ...Cn1 line coordinate inclination angle α1, α2...α n , direction angles β1, β2, ... β n And sensor C 11 , C 21 ……C n1 After the coordinates are obtained, the coordinates of the acoustic emission source S are solved simultaneously; The point (x0, y0, z0) with the shortest distance between the two straight lines is selected as the coordinate of the acoustic emission source S; The steps to find the point (x0, y0, z0) with the shortest distance between two straight lines are as follows Step 1: Use α1, α2, β1, and β2 to represent the coordinate inclination and direction angles of the corresponding straight lines: where: m i = cosα i sinβ i , n i = cosα i cosβ i , p i = sinα i , is the fixed variable of the straight line; Step 2: Calculate the distance D1 from (x0, y0, z0) to one of the straight lines: Where: (x c1 ,y c1 , z c1 ) is the foot of a perpendicular line from (x0, y0, z0), where x c1 =m1K1+x 11 ,y c1 =n1K1+y 11 , z c1 =p1K1+z 11 ; Step 3: Calculate the distance D2 from (x0, y0, z0) to another straight line: Where: (x c2 ,y c2 , z c2 ) is the foot of the perpendicular from (x0, y0, z0) to another line, where x c2 =m2K2+x 21 ,y c2 =n2K2+y 21 , z c2 =p2K2+z 21 ; Step 4: Establish the (x0, y0, z0) objective function as follows: f(x0,y0,z0)=min(D1+D2) (9) Step 5: Use genetic algorithm to iteratively solve the objective function.

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