阅读说明：本技术 基于缺陷概率重构算法的空气耦合超声检测方法及装置 (Air coupling ultrasonic detection method and device based on defect probability reconstruction algorithm ) 是由 王丙泉 赵勃 史维佳 谭久彬 于 2021-09-02 设计创作，主要内容包括：本发明公开了一种基于缺陷概率重构算法的空气耦合超声检测方法及装置,其中,该方法包括：根据导波的频散曲线结合待测件的厚度确定发射空耦换能器的激励频率；根据激励频率确定反对称模态的群速度,根据斯涅尔定律确定发射/接收空耦换能器的倾斜角；采用同侧穿透法获得无缺陷试件的初始波形作为参考数据,之后以Z方向为轴,采用旋转扫查法以预设角度间隔旋转360度发射/接收换能器再次采集待测件的N组信号数据与参考数据进行比较,以确定信号特性是否有重大变化,计算待测件上的缺陷分布概率,根据缺陷分布概率对发射/接收空耦换能器旋转覆盖区域进行缺陷成像。该方法提高了传统空耦超声X、Y扫查检测的精度,且相比复杂成像技术耗时少。(The invention discloses an air coupling ultrasonic detection method and device based on a defect probability reconstruction algorithm, wherein the method comprises the following steps: determining the excitation frequency of the transmitting space coupling transducer according to the dispersion curve of the guided wave and the thickness of the to-be-measured part; determining the group velocity of an antisymmetric mode according to the excitation frequency, and determining the inclination angle of the transmitting/receiving space-coupled transducer according to Snell's law; the method comprises the steps of obtaining an initial waveform of a non-defective test piece as reference data by adopting a same-side penetration method, then taking the Z direction as an axis, adopting a rotary scanning method to rotate a transmitting/receiving transducer at a preset angle interval for 360 degrees to acquire N groups of signal data of the to-be-detected piece again and compare the N groups of signal data with the reference data so as to determine whether signal characteristics have significant changes or not, calculating defect distribution probability on the to-be-detected piece, and carrying out defect imaging on a rotary coverage area of the transmitting/receiving space-coupled transducer according to the defect distribution probability. The method improves the precision of the traditional air-coupled ultrasound X, Y scanning detection, and is less time-consuming compared with a complex imaging technology.)

1. An air coupling ultrasonic detection method based on a defect probability reconstruction algorithm is characterized by comprising the following steps:

step S1, determining the excitation frequency of the transmitting space coupling transducer according to the dispersion curve of the guided wave and the thickness of the piece to be detected;

step S2, determining the group velocity of antisymmetric mode according to the excitation frequency, and determining the inclination angles of the transmitting and receiving space-coupled transducers according to Snell' S law;

step S3, placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of a non-defective test piece according to the inclination angle, and obtaining the initial waveform of the non-defective test piece as reference data by adopting a same side penetration method;

step S4, placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of the piece to be detected according to the inclination angle, and obtaining N groups of signal data of the detected piece by adopting a rotary scanning method;

and step S5, comparing the reference data with the N groups of signal data, solving N signal change correlation coefficients, processing the N signal change correlation coefficients based on a defect probability reconstruction algorithm to obtain defect distribution probability on the piece to be detected, and performing defect imaging on the rotation coverage area of the transmitting space coupling transducer and the receiving space coupling transducer according to the defect distribution probability.

2. The air-coupled ultrasonic detection method based on the defect probability reconstruction algorithm of claim 1, wherein the step S4 specifically includes:

step S401, placing the transmitting air coupling sensor and the receiving air coupling sensor on the same side upper surface of the piece to be detected according to the inclination angle;

step S402, rotating the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotating scanning method to acquire new signals until the transmitting air coupling sensor and the receiving air coupling sensor rotate for 360 degrees, and acquiring N groups of signal data.

3. The air coupling ultrasonic detection method based on the defect probability reconstruction algorithm according to claim 2, wherein the signal change correlation coefficient is as follows:

where ρ is a signal variation correlation coefficient, C_XYIs the covariance of X and Y, X is the reference data set, Y is the signal data after a service period, σ_XAnd σ_YIs the standard deviation of X and Y.

4. The air-coupled ultrasonic detection method based on the defect probability reconstruction algorithm of claim 1, wherein the defect distribution probability is the sum of the effect of the transmitting and receiving space-coupled transducers on all signal changes.

5. The air coupling ultrasonic detection method based on the defect probability reconstruction algorithm of claim 4, wherein the defect distribution probability is:

wherein, P_i(x, y) is a multi-order symmetrical mode S of the transmitting space coupling sensor and the receiving space coupling sensor pair_iDefect distribution probability estimation of (1), A_i(x,y)＝1-ρ_iA plurality of orders of symmetrical mode S is formed for the transmitting space coupling sensor and the receiving space coupling sensor_i(beta-R) of (A)_i(x, y))/(beta-1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

6. An air coupling ultrasonic detection device based on defect probability reconstruction algorithm is characterized by comprising:

the excitation frequency determining module is used for determining the excitation frequency of the transmitting space coupling transducer according to the dispersion curve of the guided wave and the thickness of the piece to be detected;

the inclination angle determining module is used for determining the group velocity of an antisymmetric mode according to the excitation frequency and determining the inclination angles of the transmitting null-coupling transducer and the receiving null-coupling transducer according to Snell's law;

the reference data acquisition module is used for placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of a non-defective test piece according to the inclination angle and acquiring an initial waveform of the non-defective test piece as reference data by adopting a same side penetration method;

the signal data acquisition module is used for comparing the reference data with the N groups of signal data, solving N signal change correlation coefficients, placing the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the piece to be detected on the same side according to the inclination angle, and acquiring the N groups of signal data of the piece to be detected by adopting a rotary scanning method;

and the defect imaging module is used for processing the N signal change correlation coefficients based on a defect probability reconstruction algorithm to obtain defect distribution probability on the piece to be detected, and performing defect imaging on the rotating coverage area of the transmitting space coupling transducer and the receiving space coupling transducer according to the defect distribution probability.

7. The apparatus of claim 6, wherein the means for acquiring signal data further comprises:

the placing unit is used for placing the transmitting air coupling sensor and the receiving air coupling sensor on the same side upper surface of the piece to be detected according to the inclination angle;

and the acquisition unit is used for rotating the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotating scanning method to acquire new signals until the transmitting air coupling sensor and the receiving air coupling sensor rotate for 360 degrees, and N groups of signal data are acquired.

8. The air-coupled ultrasonic detection device based on the defect probability reconstruction algorithm of claim 7, wherein the signal change correlation coefficient is:

where ρ is a signal variation correlation coefficient, C_XYIs the covariance of X and Y, X is the reference data set, Y is the signal data after a service period, σ_XAnd σ_YIs the standard deviation of X and Y.

9. The air-coupled ultrasonic detection device based on the defect probability reconstruction algorithm of claim 6, wherein the defect distribution probability is the sum of the effect of the transmitting and receiving space-coupled transducers on all signal changes.

10. The air-coupled ultrasonic detection device based on the defect probability reconstruction algorithm of claim 9, wherein the defect distribution probability is:

wherein, P_i(x, y) is a multi-order symmetrical mode S of the transmitting space coupling sensor and the receiving space coupling sensor pair_iDefect distribution probability estimation of (1), A_i(x,y)＝1-ρ_iA plurality of orders of symmetrical mode S is formed for the transmitting space coupling sensor and the receiving space coupling sensor_i(beta-R) of (A)_i(x, y))/(beta-1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

Technical Field

The invention relates to the technical field of ultrasonic detection, in particular to an air coupling ultrasonic detection method and device based on a defect probability reconstruction algorithm.

Background

With the progress of scientific technology, the development of market and the change of scientific research requirements, conventional materials cannot meet certain harsh requirements, so that engineering application is hindered. To overcome this difficulty, composite materials have come into use to realize materials specific to a particular application scenario. The composite material has very high specific strength and specific stiffness, can realize design and customization, has better fatigue resistance than the traditional material, has strong vibration reduction capability, stable performance under high temperature, good stability and safety and other excellent performances, is widely applied to various industries, and has strong application prospect from military aviation and aerospace to civil automobile medical treatment.

Along with the expansion of the application range of the composite material, the application environment of the composite material is more and more complex and worse, so that the damage of the composite material caused by factors such as vibration, impact, fatigue and the like in the service process is more and more obvious, and in addition, the existence of inherent defects or the defects of some materials are inevitable in the production and processing processes, therefore, the nondestructive detection of the composite material is necessary to avoid the loss of engineering caused by the failure of the composite material.

The air-coupled ultrasound is a novel ultrasound detection method, and has the outstanding advantages that no coupling agent is required to be applied in the detection process, and the detection of certain special detection occasions or special materials, such as composite materials, medicinal materials, wood and the like which are not suitable for detection by using the coupling agent, is unique. The traditional ultrasound is excited by a transducer and then must be transmitted to a measured object through a coupling agent, so as to ensure the maximum transmission of energy, but at the same time, the material is polluted and even damaged, so that the use of the ultrasonic detection is limited to a certain extent; the air coupling ultrasonic wave well overcomes the problems, can directly transmit the sound wave out through the air to complete non-contact nondestructive detection, has good adaptability to complex geometric components, and has important significance for the research thereof.

At present, in the market, the air coupling ultrasonic detection of the to-be-detected piece is usually carried out by adopting a different-side vertical penetration method, and scanning in the X, Y direction is carried out on two transmitting and receiving air coupling transducers by combining a scanning mechanism, so that the two-dimensional plane imaging detection is realized. The different-side vertical penetration method needs to place the transmitting space coupling transducer and the receiving space coupling transducer at two sides of the piece to be detected, and the requirement cannot be met for some in-service actual detection scenes. Meanwhile, defect two-dimensional imaging performed through X, Y direction scanning cannot meet the requirement of detection precision, and the missing detection phenomenon is easily generated for some small defects. Although defect detection, growth monitoring and mapping of the location of the guided wave array using computed tomography techniques with wave velocity, attenuation or energy as a feature for image reconstruction can yield accurate defect images, these methods are time consuming and the sensitivity of sparse sensors is unsatisfactory.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.

Therefore, an object of the present invention is to provide an air-coupled ultrasound detection method based on a defect probability reconstruction algorithm, which improves the accuracy of the conventional air-coupled ultrasound X, Y scanning detection and consumes less time compared with the complex imaging technology.

The invention also aims to provide an air coupling ultrasonic detection device based on the defect probability reconstruction algorithm.

In order to achieve the above object, an embodiment of the invention provides an air coupling ultrasonic detection method based on a defect probability reconstruction algorithm, which includes the following steps: step S1, determining the excitation frequency of the transmitting space coupling transducer according to the dispersion curve of the guided wave and the thickness of the piece to be detected; step S2, determining the group velocity of antisymmetric mode according to the excitation frequency, and determining the inclination angles of the transmitting and receiving space-coupled transducers according to Snell' S law; step S3, placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of a non-defective test piece according to the inclination angle, and obtaining the initial waveform of the non-defective test piece as reference data by adopting a same side penetration method; step S4, placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of the piece to be detected according to the inclination angle, and obtaining N groups of signal data of the piece to be detected by adopting a rotary scanning method; and step S5, comparing the reference data with the N groups of signal data, solving N signal change correlation coefficients, processing the N signal change correlation coefficients based on a defect probability reconstruction algorithm to obtain defect distribution probability on the piece to be detected, and performing defect imaging on the rotation coverage area of the transmitting space coupling transducer and the receiving space coupling transducer according to the defect distribution probability.

The air coupling ultrasonic detection method based on the defect probability reconstruction algorithm improves the precision of scanning detection of the traditional air coupling ultrasonic X, Y, is less time-consuming compared with a complex imaging technology, is caused by the defect generation in the same environment and measurement condition, and can monitor the defect growth by tracking the increase of the signal difference relative to the normal condition, so that the fact health monitoring of the piece to be detected is realized.

In addition, the air coupling ultrasonic detection method based on the defect probability reconstruction algorithm according to the above embodiment of the present invention may further have the following additional technical features:

further, in an embodiment of the present invention, the step S4 specifically includes: step S401, placing the transmitting air coupling sensor and the receiving air coupling sensor on the same side upper surface of the piece to be detected according to the inclination angle; step S402, rotating the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotating scanning method to acquire new signals until the transmitting air coupling sensor and the receiving air coupling sensor rotate for 360 degrees, and acquiring N groups of signal data.

Further, in one embodiment of the present invention, the signal variation correlation coefficient is:

where ρ is a signal variation correlation coefficient, C_XYIs the covariance of X and Y, X is the reference data set, and Y is a segmentSignal data after service time, σ_XAnd σ_YIs the standard deviation of X and Y.

Further, in one embodiment of the present invention, the defect distribution probability is a sum of the effect of the transmitting and receiving space-coupled transducers on all signal variations.

Further, in an embodiment of the present invention, the defect distribution probability is:

wherein, P_i(x, y) is a multi-order symmetrical mode S of the transmitting space coupling sensor and the receiving space coupling sensor pair_iDefect distribution probability estimation of (1), A_i(x,y)＝1-ρ_iA plurality of orders of symmetrical mode S is formed for the transmitting space coupling sensor and the receiving space coupling sensor_i(beta-R) of (A)_i(x, y))/(beta-1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

In order to achieve the above object, an embodiment of another aspect of the present invention provides an air-coupled ultrasonic detection apparatus based on a defect probability reconstruction algorithm, including: the excitation frequency determining module is used for determining the excitation frequency of the transmitting space coupling transducer according to the dispersion curve of the guided wave and the thickness of the piece to be detected; the inclination angle determining module is used for determining the group velocity of an antisymmetric mode according to the excitation frequency and determining the inclination angles of the transmitting null-coupling transducer and the receiving null-coupling transducer according to Snell's law; the reference data acquisition module is used for placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of a non-defective test piece according to the inclination angle and acquiring an initial waveform of the non-defective test piece as reference data by adopting a same side penetration method; the signal data acquisition module is used for placing the transmitting space coupling sensor and the receiving space coupling sensor on the upper surface of the same side of the piece to be detected according to the inclination angle and acquiring N groups of signal data of the piece to be detected by adopting a rotary scanning method; and the defect imaging module is used for comparing the reference data with the N groups of signal data, solving N signal change correlation coefficients, processing the N signal change correlation coefficients based on a defect probability reconstruction algorithm to obtain defect distribution probability on the to-be-detected piece, and performing defect imaging on the rotating coverage area of the transmitting air-coupled transducer and the receiving air-coupled transducer according to the defect distribution probability.

The air coupling ultrasonic detection device based on the defect probability reconstruction algorithm improves the precision of scanning detection of the traditional air coupling ultrasonic X, Y, consumes less time compared with a complex imaging technology, is caused by the defect generation in the same environment and measurement condition, and can monitor the defect growth by tracking the increase of the signal difference relative to the normal condition, so that the fact health monitoring of the piece to be detected is realized.

In addition, the air-coupled ultrasonic detection device based on the defect probability reconstruction algorithm according to the above embodiment of the present invention may further have the following additional technical features:

further, in an embodiment of the present invention, the module for acquiring signal data further includes: the placing unit is used for placing the transmitting air coupling sensor and the receiving air coupling sensor on the same side upper surface of the piece to be detected according to the inclination angle; and the acquisition unit is used for rotating the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotating scanning method to acquire new signals until the transmitting air coupling sensor and the receiving air coupling sensor rotate for 360 degrees, and N groups of signal data are acquired.

Further, in one embodiment of the present invention, the signal variation correlation coefficient is:

where ρ is a signal variation correlation coefficient, C_XYIs the covariance of X and Y, X is the reference data set, Y is the signal data after a service period, σ_XAnd σ_YIs the standard deviation of X and Y。

Further, in one embodiment of the present invention, the defect distribution probability is a sum of the effect of the transmitting and receiving space-coupled transducers on all signal variations.

Further, in an embodiment of the present invention, the defect distribution probability is:

wherein, P_i(x, y) is a multi-order symmetrical mode S of the transmitting space coupling sensor and the receiving space coupling sensor pair_iDefect distribution probability estimation of (1), A_i(x,y)＝1-ρ_iA plurality of orders of symmetrical mode S is formed for the transmitting space coupling sensor and the receiving space coupling sensor_i(beta-R) of (A)_i(x, y))/(beta-1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a flow chart of an air-coupled ultrasonic inspection method based on a defect probability reconstruction algorithm according to an embodiment of the present invention;

FIG. 2 is a graph showing the variation of the guided wave dispersion characteristic according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of detection by air-coupled ultrasound ipsilateral penetration according to one embodiment of the present invention;

FIG. 4 is a schematic diagram of a rotational scanning method for space-coupled ultrasound according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an elliptical distribution function of a defect probability reconstruction algorithm according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of an air-coupled ultrasonic detection apparatus based on a defect probability reconstruction algorithm according to an embodiment of the present invention.

Description of reference numerals: the method comprises the following steps of 1-transmitting an air coupling transducer, 2-receiving an air coupling transducer, 3-detecting an object to be detected, 10-air coupling ultrasonic detection device based on defect probability reconstruction algorithm, 100-excitation frequency determination module, 200-inclination angle determination module, 300-acquiring reference data module, 400-acquiring signal data module and 500-defect imaging module.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

The air-coupled ultrasonic detection method and device based on the defect probability reconstruction algorithm according to the embodiment of the invention are described below with reference to the accompanying drawings, and firstly, the air-coupled ultrasonic detection method based on the defect probability reconstruction algorithm according to the embodiment of the invention will be described with reference to the accompanying drawings.

FIG. 1 is a flowchart of an air-coupled ultrasonic inspection method based on a defect probability reconstruction algorithm according to an embodiment of the present invention.

As shown in fig. 1, the air-coupled ultrasonic detection method based on the defect probability reconstruction algorithm includes the following steps:

in step S1, the excitation frequency of the transmitting space-coupled transducer is determined according to the dispersion curve of the guided wave and the thickness of the member to be detected.

Specifically, as shown in fig. 2, the guided wave has symmetric modes, antisymmetric modes, and dispersion characteristics, and multiple-order symmetric modes (S0, S1, …, Si) and antisymmetric modes (a0, a1, …, Ai) may be excited at the same excitation frequency. In order to excite a purer mode in the to-be-detected piece by the space coupling transducer, the excitation frequency of the transmitting space coupling transducer can be known to be smaller than a certain upper limit value according to the dispersion curve of the guided wave and the thickness of the to-be-detected piece, and then the excitation frequency is determined according to the actual performance of the space coupling transducer.

In step S2, the group velocity of the antisymmetric mode is determined from the excitation frequency, and the tilt angles of the transmitting and receiving null-coupled transducers are determined according to snell' S law.

Specifically, as can be known by those skilled in the art from research and analysis, the in-plane displacement of the symmetric mode is large, and the out-of-plane displacement of the anti-symmetric mode is large, so that the anti-symmetric mode is adopted for the space-coupled ultrasonic detection. After the frequency-thickness product (frequency x the thickness of the device to be measured) is determined, the group velocity of the antisymmetric mode A0 can also be known, and then the inclination angle of the air-coupled transducer is determined according to the first critical refraction angle of Snell's law and the propagation velocity in the air.

In step S3, the transmitting and receiving space coupling sensors are placed on the same side upper surface of the non-defective specimen according to the inclination angle, and the initial waveform of the non-defective specimen is obtained as reference data by the same side penetration method.

In step S4, the transmitting space coupling sensor and the receiving space coupling sensor are placed on the same upper surface of the piece to be detected according to the inclination angle, and N sets of signal data of the piece to be detected are obtained by a rotary scanning method.

Further, in an embodiment of the present invention, step S4 specifically includes:

step S401, placing a transmitting air coupling sensor and a receiving air coupling sensor on the same side upper surface of a piece to be detected according to an inclination angle;

and S402, rotating the transmitting air-coupling sensor and the receiving air-coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotating scanning method to acquire new signals until the transmitting air-coupling sensor and the receiving air-coupling sensor rotate for 360 degrees, and acquiring N groups of signal data.

Specifically, as shown in fig. 3 and 4, an initial waveform of a non-defective test piece is obtained by using a same-side penetration method as reference data, then the transmitting space-coupling sensor and the receiving space-coupling sensor are placed on the upper surface of the same side of the test piece to be tested according to the inclination angle, a rotating scanning method is adopted to rotate the transmitting space-coupling transducer and the receiving transducer at preset angle intervals to acquire new signals again by taking the Z direction as an axis, and by analogy, when the test piece is rotated by 360 degrees, N groups of signal data are obtained, then the N groups of signal data are compared with the reference data, and N signal change correlation coefficients are solved to determine whether the signal characteristics have significant changes.

Wherein, the change of the signal can be represented by a signal change correlation coefficient rho as:

in the formula, C_XYIs the covariance of X and Y,

where μ is the average of each data set, K is the length of the data set, X is the reference data set, Y is the signal data after a service period, and σ is_XAnd σ_YIs the standard deviation of X and Y.

In step S5, the reference data and the N groups of signal data are compared to solve N signal change correlation coefficients, the N signal change correlation coefficients are processed based on a defect probability reconstruction algorithm to obtain a defect distribution probability on the to-be-detected object, and defect imaging is performed on the rotation coverage area of the transmitting space-coupling transducer and the receiving space-coupling transducer according to the defect distribution probability.

That is, the embodiment of the present invention detects small defects by measuring the difference of guided wave signals under normal and fault conditions based on a defect probability reconstruction algorithm.

In particular, as shown in FIG. 5, to determine the location of a defect, embodiments of the present invention assume that the probability of a defect occurring at a certain point can be estimated from the severity of the signal variations of different sensor pairs and their location relative to the sensor pairs. This means that the defect will cause the most significant signal change in the direct path, and if the defect is far from the direct path of the sensor pair, the signal change effect will be reduced. The probability of defect distribution in the sensor network can be expressed as the sum of all signal variation effects of each transmitting and receiving space-coupled transducer pair. Here, a simple linearly decreasing elliptical profile is assumed, with the transmitting and receiving space-coupling transducers at the foci of the ellipse. Assuming that in a total number N of null-coupled transducer pair networks, the probability of defect estimation at location (x, y) within the reconstruction region can be written as:

in the formula, P_i(x, y) is from the transmitting and receiving space-coupled transducer pairs of multi-order symmetric modes S_iDefect distribution probability estimation of (1), A_i(x, y) is a pair of a transmitting space-coupled transducer and a receiving space-coupled transducer in a multi-order symmetrical mode S_iSignal difference coefficient of (A)_i(x,y)＝1-ρ_i。(β-R_i(x, y))/(β -1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

In the formula:

is a point (x, y) to a transmitting space-coupled transducer and a receiving space-coupled transducer pair with a multi-order symmetrical mode S_iThe sum of the distances of the transmitting space-coupling transducer and the receiving space-coupling transducer is compared with the distance between the transmitting space-coupling transducer and the receiving space-coupling transducer. Beta is a scaling parameter controlling the size of the effective elliptical distribution area and beta>1. When RD_iBy 1 (x, y) is meant the point (x, y) at the transmit/receive space-coupled transducer pair multi-order symmetric mode S_iOn a straight line of (1), thisWhen is, P_i(x,y)＝A_i(x, y); when RD_iThat (x, y) ═ β means that the point (x, y) is on the boundary of the effective distribution area, in this case, P_i(x, y) ═ β. Generally, β is selected to be about 1.05. If β is too small, artifacts are introduced, and if β is too large, resolution is lost. In general, a set of transmit/receive null-coupled transducer pairs will be affected if a defect occurs. As a result, in the defect distribution probability image, the point where the defect is located will have a significantly greater probability than other points. Therefore, by applying image processing techniques to process the defect distribution probability, for example, selecting a threshold value of the defect estimation image, the defect position can be estimated, and thus the defect of the object to be detected can be imaged.

According to the air coupling ultrasonic detection method based on the defect probability reconstruction algorithm, the precision of scanning and detecting of the traditional air coupling ultrasonic X, Y is improved, time consumption is low compared with that of a complex imaging technology, the defect is generated due to the change under the same environment and measurement conditions, and the defect growth can be monitored by tracking the increase of the signal difference relative to the normal condition, so that the fact health monitoring of the piece to be detected is realized.

The air coupling ultrasonic detection device based on the defect probability reconstruction algorithm provided by the embodiment of the invention is described next with reference to the attached drawings.

Fig. 6 is a schematic structural diagram of an air-coupled ultrasonic detection apparatus based on a defect probability reconstruction algorithm according to an embodiment of the present invention.

As shown in fig. 6, the apparatus 10 includes: excitation frequency determination module 100, tilt angle determination module 200, acquire reference data module 300, acquire signal data module 400, and defect imaging module 500.

The excitation frequency determining module 100 is configured to determine the excitation frequency of the transmitting space-coupled transducer according to the dispersion curve of the guided wave and the thickness of the to-be-detected element. The tilt angle determination module 200 is used for determining the group velocity of the antisymmetric mode according to the excitation frequency, and determining the tilt angles of the transmitting and receiving null-coupled transducers according to snell's law. The reference data acquiring module 300 is configured to place the transmitting space coupling sensor and the receiving space coupling sensor on the same side upper surface of the non-defective test piece according to the inclination angle, and acquire an initial waveform of the non-defective test piece as reference data by using a same side penetration method. The signal data acquiring module 400 is used for placing the transmitting space coupling sensor and the receiving space coupling sensor on the same upper surface of the piece to be detected according to the inclination angle, and acquiring N groups of signal data of the piece to be detected by adopting a rotary scanning method. The defect imaging module 500 is configured to compare the reference data with the N groups of signal data, solve N signal change correlation coefficients, process the N signal change correlation coefficients based on a defect probability reconstruction algorithm to obtain a defect distribution probability on the to-be-detected object, and perform defect imaging on the rotation coverage area of the transmitting space-coupling transducer and the receiving space-coupling transducer according to the defect distribution probability.

Further, in an embodiment of the present invention, the module 400 for acquiring signal data further includes: the placing unit is used for placing the transmitting air coupling sensor and the receiving air coupling sensor on the upper surface of the same side of the piece to be detected according to the inclination angle; and the acquisition unit is used for rotationally transmitting the air coupling sensor and receiving new signals from the air coupling sensor on the upper surface of the same side of the piece to be detected at preset angle intervals by adopting a rotational scanning method, and acquiring N groups of signal data until the rotation is 360 degrees.

Further, in one embodiment of the present invention, the signal change correlation coefficient is:

where ρ is a signal variation correlation coefficient, C_XYIs the covariance of X and Y, X is the reference data set, Y is the signal data after a service period, σ_XAnd σ_YIs the standard deviation of X and Y.

Further, in one embodiment of the present invention, the defect distribution probability is the sum of the effect of the transmitting and receiving space-coupled transducers on all signal variations.

Further, in one embodiment of the present invention, the defect distribution probability is:

wherein, P_i(x, y) is a multi-order symmetrical mode S of a transmitting space-coupled sensor and a receiving space-coupled sensor pair_iDefect distribution probability estimation of (1), A_i(x,y)＝1-ρ_iFor transmitting and receiving space coupling sensor pair multi-order symmetrical mode S_i(beta-R) of (A)_i(x, y))/(beta-1) is a multi-order symmetric mode S_iThe contour of the non-negative spatial distribution function of (3) is a set of ellipses.

It should be noted that the foregoing explanation of the embodiment of the air-coupled ultrasonic detection method based on the defect probability reconstruction algorithm is also applicable to the apparatus, and is not repeated here.

According to the air coupling ultrasonic detection device based on the defect probability reconstruction algorithm, the precision of scanning and detecting of the traditional air coupling ultrasonic X, Y is improved, time consumption is low compared with that of a complex imaging technology, the defect is generated due to the change under the same environment and measurement conditions, and the defect growth can be monitored by tracking the increase of the signal difference relative to a normal condition, so that the fact health monitoring of a piece to be detected is realized.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.