CN105044212A - Multimodal ultrasonic Lamb wave complex defect tomography method - Google Patents

Abstract

Translated fromChinese

本发明提供了一种多模态超声Lamb波复杂缺陷层析成像方法，包括以下步骤：通过预设敏感度阈值THs和敏感度死区d_z，计算得到A0和S0两种模态Lamb波合适的工作频率；分别使用A0波EMAT阵列和S0波EMAT阵列，在各自工作频率条件下进行A0波跨孔层析成像和S0波跨孔层析成像；通过图像融合，将两种结果有机结合，得到最终的缺陷图像重建结果。该方法的优势在于，可以充分利用不同模态Lamb波的敏感区域不同的特点，进行敏感区域的互补，从而扩大层析成像方法的整体敏感区域，降低噪声的影响，有效减少从慢度分布图中提取缺陷特征信息的难度，提高对复杂缺陷的识别效率和成像精度，具有广阔的应用前景。

The present invention provides a multi-modal ultrasonic Lamb wave tomography method for complex defects, which includes the following steps: calculating and obtaining two modes of Lamb waves, A0 and S0, through preset sensitivity threshold_THs and sensitivity dead zone dz working frequency; respectively use A0-wave EMAT array and S0-wave EMAT array to perform A0-wave cross-hole tomography and S0-wave cross-hole tomography under their respective working frequency conditions; through image fusion, the two results are organically combined, Get the final defect image reconstruction result. The advantage of this method is that it can make full use of the different characteristics of the sensitive regions of different modes of Lamb waves to complement the sensitive regions, thereby expanding the overall sensitive region of the tomography method, reducing the influence of noise, and effectively reducing the slowness profile from the slowness distribution map. It can improve the recognition efficiency and imaging accuracy of complex defects, and has broad application prospects.

Description

Translated fromChinese

一种多模态超声Lamb波复杂缺陷层析成像方法A Multimodal Ultrasonic Lamb Wave Tomography Method for Complicated Defects

技术领域technical field

本发明涉及一种多模态超声Lamb波复杂缺陷层析成像方法，属于无损检测技术领域。The invention relates to a multi-mode ultrasonic Lamb wave complex defect tomography method, which belongs to the technical field of non-destructive testing.

背景技术Background technique

利用超声Lamb波缺陷层析成像技术可以快速、有效地获得缺陷的轮廓和尺寸等具体信息。该技术继承了传统超声Lamb波检测的诸多优点。Lamb波走时(Time-of-flight，TOF，指Lamb波在收发换能器对之间的传播时间)跨孔层析成像技术，利用线性换能器阵列进行扇束投影和成像，是一种基于迭代法的高效、快速的层析成像方法。该成像方法的直接输出结果为Lamb波的慢度(速度的倒数)分布，其通过不同区域中慢度的变化情况来反映缺陷的分布情况。通常，在成像过程中，多选择使用单一模态Lamb波，这种方法操作简单，收发环境纯净，对于形状参数较为简单的缺陷，如单圆孔缺陷的图像重建，不但计算快速而且成像精度高。然而，当遇到含有深度逐渐变化的复杂缺陷时，其求得的慢度分布上会叠加有较多的噪声，缺陷导致的慢度变化在一定程度上会被噪声所掩盖，进而会使得从慢度分布图中提取缺陷特征信息的难度和误差增大，从而影响到成像结果。中国专利文献公开了一种“一种射线追踪式超声Lamb波缺陷层析成像方法”该技术涉及一种铝板缺陷超声Lamb波在线检测方法，采用EMAT(电磁声换能器)阵列收发单一Lamb波，通过联合迭代重建算法及射线追踪修正算法重建层析图像，可较为精确地实现对铝板单圆孔缺陷的全面检测及缺陷分析，但该技术局限于深度统一的规则缺陷，而对深度变化的复杂缺陷的具体尺寸和轮廓并不能达到十分精确的估计，存在一定的局限性。The specific information such as the outline and size of the defect can be obtained quickly and effectively by using the ultrasonic Lamb wave defect tomography technology. This technology inherits many advantages of traditional ultrasonic Lamb wave detection. Lamb wave travel time (Time-of-flight, TOF, refers to the propagation time of Lamb wave between the transmitting and receiving transducer pairs) cross-aperture tomography technology, using linear transducer array for fan beam projection and imaging, is a kind of An efficient and fast tomography method based on an iterative method. The direct output of this imaging method is the distribution of Lamb wave slowness (reciprocal of velocity), which reflects the distribution of defects through the variation of slowness in different regions. Usually, in the imaging process, the single-mode Lamb wave is mostly used. This method is easy to operate and the receiving and receiving environment is pure. For defects with relatively simple shape parameters, such as image reconstruction of single round hole defects, not only the calculation is fast but the imaging accuracy is high. . However, when encountering complex defects with gradual depth changes, more noise will be superimposed on the obtained slowness distribution, and the slowness changes caused by defects will be covered by noise to a certain extent, which will make the slowness distribution from The difficulty and error in extracting defect feature information from the slowness distribution map will increase, thus affecting the imaging results. Chinese patent literature discloses a "ray-tracing ultrasonic Lamb wave defect tomography method". This technology involves an ultrasonic Lamb wave online detection method for aluminum plate defects, using EMAT (Electromagnetic Acoustic Transducer) arrays to send and receive a single Lamb wave , by combining the iterative reconstruction algorithm and the ray tracing correction algorithm to reconstruct the tomographic image, the comprehensive detection and defect analysis of the single round hole defect of the aluminum plate can be realized more accurately, but this technology is limited to the regular defect with uniform depth, and the depth change The specific size and outline of complex defects cannot be estimated very accurately, and there are certain limitations.

发明内容Contents of the invention

本发明旨在至少解决上述技术问题之一。The present invention aims to solve at least one of the above-mentioned technical problems.

为此，本发明的目的在于提出一种多模态超声Lamb波复杂缺陷层析成像方法。For this reason, the object of the present invention is to propose a multimodal ultrasonic Lamb wave complex defect tomography method.

为了实现上述目的，本发明一方面的实施例公开了一种多模态超声Lamb波复杂缺陷层析成像方法，包括如下步骤：1)在待测板材上选择一个矩形区域作为缺陷层的成像区域，将所述成像区域横纵分割成N₁×N₂个网格；在所述成像区域的一侧设置M个发射电磁声换能器，在所述成像区域与所述发射磁声换能器的相对侧设置M个接收电磁声换能器；其中，N₁、N₂、M为自然数；2)使用射频功率放大器分两次激励所述M个发射电磁声换能器，其中，第一次全向激发A0模态Lamb波，所述M个接收电磁声换能器依次接收所述A0模态Lamb波；第二次全向激发S0模态Lamb波，M个接收电磁声换能器依次接收所述A0模态Lamb波；3)利用伪Wigner-Ville分布对M×M个A0模态电磁声换能器检测波形和M×M个S0模态电磁声换能器检测波形进行时频分析和模态识别；4)提取所述M×M个A0电磁声换能器检测波形的时频分析结果并记录对应的走时T₁(A0)～T_M×M(A0)；提取所述M×M个S0电磁声换能器检测波形的时频分析结果并记录对应的走时T₁(S0)～T_M×M(S0)；5)使用联合迭代重建算法确定所述A0模态和所述S0模态下所述N_1×N₂个网格中每个网格的慢度：In order to achieve the above object, an embodiment of one aspect of the present invention discloses a multi-modal ultrasonic Lamb wave complex defect tomography method, which includes the following steps: 1) Select a rectangular area on the plate to be tested as the imaging area of the defect layer , dividing the imaging area horizontally and vertically into N₁ ×N₂ grids; M emitting electromagnetic acoustic transducers are arranged on one side of the imaging area, and the imaging area is connected to the emitting magnetic acoustic transducer M receiving electromagnetic acoustic transducers are arranged on the opposite side of the device; wherein, N₁ , N₂ , and M are natural numbers; 2) using a radio frequency power amplifier to excite the M transmitting electromagnetic acoustic transducers twice, wherein the first The A0 mode Lamb wave is excited omnidirectionally once, and the M receiving electromagnetic acoustic transducers receive the A0 mode Lamb wave in turn; the S0 mode Lamb wave is excited omnidirectionally for the second time, and the M receiving electromagnetic acoustic transducers The A0 mode Lamb wave is sequentially received by the transducer; 3) the detection waveforms of M×M A0 mode electromagnetic acoustic transducers and the detection waveforms of M×M S0 mode electromagnetic acoustic transducers are performed using the pseudo Wigner-Ville distribution Time-frequency analysis and mode recognition; 4) extract the time-frequency analysis results of the M×M A0 electromagnetic acoustic transducer detection waveforms and record the corresponding travel time T₁ (A0)～T_M×M (A0); extract The M×M S0 electromagnetic acoustic transducers detect the time-frequency analysis results of the waveform and record the corresponding travel time T₁ (S0)～T_M×M (S0); 5) use a joint iterative reconstruction algorithm to determine the A0 mode mode and the slowness of each of the N_{1 ×} N₂ grids in the S0 mode:

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>i</span>i</span>}}<span><span>=</span>=</span>\underset{\mathrm{<span><span>j</span>j</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}}{\overset{\mathrm{<span><span>n</span>no</span>}}{<span><span>\&Sigma;</span>\&Sigma;</span>}}{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>i</span>i</span>}\mathrm{<span><span>j</span>j</span>}}<span><span>*</span>*</span>{\mathrm{<span><span>S</span>S</span>}}_{\mathrm{<span><span>j</span>j</span>}}<span><span>,</span>,</span><span><span>(</span>(</span>\mathrm{<span><span>i</span>i</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}<span><span>,</span>,</span>\mathrm{<span><span>2</span>2</span>}<span><span>,</span>,</span><span><span>...</span>...</span><span><span>,</span>,</span>\mathrm{<span><span>m</span>m</span>}<span><span>)</span>)</span>$

其中，S_j为待求的第j个网格的慢度；L_ij为第i条投影射线在第j个网格中的长度；T_i为第i条投影射线的实测走时；n为正整数，且n＝N₁×N₂；m为正整数，且m＝M×M；6)使用图像融合方法将所述A0模态和所述S0模态下得到的两组慢度分布结果转化为板厚分布结果，再进行叠加，并求取平均，从而得到最终的缺陷分布结果。Among them, S_j is the slowness of the j-th grid to be obtained; L_ij is the length of the i-th projected ray in the j-th grid; T_i is the measured travel time of the i-th projected ray; n is positive Integer, and n=N₁ ×N₂ ; m is a positive integer, and m=M×M; 6) Use the image fusion method to combine the two groups of slowness distribution results obtained under the A0 mode and the S0 mode Converted to plate thickness distribution results, then superimposed, and averaged to obtain the final defect distribution results.

根据本发明实施例的一种多模态超声Lamb波复杂缺陷层析成像方法，使用A0波EMAT阵列和S0波EMAT阵列，在不同频率下进行A0波跨孔层析成像和S0波跨孔层析成像，并通过图像融合，得到最终的图像重建结果。该方法的优势在于，可以充分利用不同模态Lamb波的敏感区域不同的特点，进行敏感区域的互补，从而扩大层析成像方法的整体敏感区域，降低噪声的影响，有效减少从慢度分布图中提取缺陷特征信息的难度，提高对复杂缺陷的识别效率和成像精度，具有广阔的应用前景。According to a multi-modal ultrasonic Lamb wave complex defect tomography method according to an embodiment of the present invention, the A0 wave EMAT array and the S0 wave EMAT array are used to perform A0 wave cross-hole tomography and S0 wave cross-hole layer at different frequencies Image analysis, and through image fusion, the final image reconstruction result is obtained. The advantage of this method is that it can make full use of the different characteristics of the sensitive regions of different modes of Lamb waves to complement the sensitive regions, thereby expanding the overall sensitive region of the tomography method, reducing the influence of noise, and effectively reducing the slowness profile from the slowness distribution map. It can improve the recognition efficiency and imaging accuracy of complex defects, and has broad application prospects.

另外，根据本发明上述实施例的一种多模态超声Lamb波复杂缺陷层析成像方法，还可以具有如下附加的技术特征：In addition, a multimodal ultrasonic Lamb wave complex defect tomography method according to the above-mentioned embodiments of the present invention may also have the following additional technical features:

进一步地，步骤1)中，所述发射电磁声换能器和所述接收电磁声换能器直径范围均为20～60mm，相邻所述发射电磁声换能器和所述接收电磁声换能器的中心间距均为30～90mm。Further, in step 1), the diameter ranges of the transmitting electromagnetic acoustic transducer and the receiving electromagnetic acoustic transducer are both 20-60mm, and the adjacent transmitting electromagnetic acoustic transducer and the receiving electromagnetic acoustic transducer The distance between the centers of the energy devices is 30-90mm.

进一步地，步骤2)中，所述射频功率放大器的激发频率为(100～1000)kHz；第一次激发的Lamb波为纯净单一的A0模态Lamb波；第二次激发的Lamb波为纯净单一的S0模态Lamb波。Further, in step 2), the excitation frequency of the RF power amplifier is (100-1000) kHz; the Lamb wave excited for the first time is a pure single A0 mode Lamb wave; the Lamb wave excited for the second time is pure A single S0 mode Lamb wave.

进一步地，步骤2)中，所述A0模态Lamb波和所述S0模态Lamb波的激发频率方法进一步包括：201)定义Lamb波对板厚变化的敏感度函数：Further, in step 2), the excitation frequency method of the A0 modal Lamb wave and the S0 modal Lamb wave further includes: 201) defining the sensitivity function of the Lamb wave to the plate thickness variation:

SEN(f,d,Δd)＝|S_the(f,d-Δd)-S_the(f,d)|/ΔdSEN(f,d,Δd)=|S_the (f,d-Δd)-S_the (f,d)|/Δd

其中，S_the(f,d-Δd)和S_the(f,d)分别为所用模态Lamb波在缺陷区域和基础板厚区域的慢度值；f为所用模态Lamb波的工作频率；d为基础板厚；Δd为缺陷区域的板厚相比于基础板厚的减小量；(d-Δd)为缺陷区域的板厚；202)设置Lamb波敏感度函数SEN(f,d)的阈值TH_S：Among them, S_the (f,d-Δd) and S_the (f,d) are the slowness values of the used mode Lamb wave in the defect area and the base plate thickness area respectively; f is the working frequency of the used mode Lamb wave; d is the base plate thickness; Δd is the reduction of the plate thickness in the defect area compared to the base plate thickness; (d-Δd) is the plate thickness in the defect area; 202) Set the value of the Lamb wave sensitivity function SEN(f,d) Threshold TH_S :

THs＝SNR_min×S_noise/d_minTHs＝SNR_min ×S_noise /d_min

其中，SNR_min和d_min分别为层析成像所需的最小信噪比和板厚分辨率；S_noise为噪声幅值；203)分别计算所述A0波和所述S0波的板厚变化敏感度函数SEN(f,d)随d变化的曲线，得到两种模态波SEN(f,d)的幅值在f-d上的二维分布图；其中，工作频率f的取值为(100～1000)kHz。204)在所述S0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线；205)计算曲线fd＝x_s与直线d＝d₀的交点坐标，记为(d₀，f_s)，取f_s为S0模态波的工作频率；其中，所述fd＝x_s对应的虚线曲线是S0波工作区域的边界；d₀为铝板健康区域的板厚；206)计算直线f＝f_s与等高线SEN(f,d)＝THs的交点(d_L，f_s)，得到S0波在工作频率f_s下的工作区域为[d_L，d₀]；207)在所述A0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线；208)计算曲线fd＝x_a和SEN(f,d)＝THs与直线d＝d_L+d_z的交点坐标(d_L+d_z，f_a1)和(d_L+d_z，f_a2)，取f_a1和f_a2中相对较小的一个作为A0波的工作频率f_a；其中，d_z(d_z>0)是为保证A0和S0波的敏感区域重叠而设置的一个死区，使得A0波的敏感区域的上限值d_H满足d_H>d_L+d_z；fd＝x_a对应的虚线曲线是A0波工作区域的边界；209)为提高对微小缺陷的检测灵敏度，取f_a为S0模态波的工作频率，得到A0波在工作频率f_a下的工作区域为[0，d_L+d_z]。Wherein, SNR_min and d_min are the minimum signal-to-noise ratio and plate thickness resolution required by tomography respectively; S_noise is the noise amplitude; 203) Calculate the plate thickness change sensitivity of the A0 wave and the S0 wave respectively The curve of the degree function SEN(f,d) changing with d, and the two-dimensional distribution diagram of the amplitude of the two modal waves SEN(f,d) on fd; where the value of the operating frequency f is (100～ 1000) kHz. 204) On the SEN (f, d) distribution map of the S0 modal wave, find the contour line corresponding to SEN (f, d)=THs; 205) Calculate the relationship between the curve fd=x_s and the straight line d=d₀ Intersection coordinates, denoted as (d₀ , f_s ), take f_s as the operating frequency of the S0 modal wave; wherein, the dotted curve corresponding to fd=x_s is the boundary of the S0 wave working area; d₀ is the health of the aluminum plate Plate thickness in the area; 206) Calculate the intersection point (d_L , f_s ) of the straight line f=f_s and the contour line SEN(f,d)=THs, and obtain the working area of the S0 wave at the working frequency f_s as [d_L , d₀ ]; 207) on the SEN (f, d) distribution map of the A0 modal wave, find the contour line corresponding to SEN (f, d)=THs; 208) calculate the curve fd=x_a and SEN(f,d)=THs and straight line d=d_L +d_z intersection coordinates (d_L +d_z , f_a1 ) and (d_L +d_z , f_a2 ), take the relative of f_a1 and f_a2 The smaller one is the working frequency f_a of the A0 wave; among them, d_z (d_z >0) is a dead zone set to ensure that the sensitive areas of the A0 and S0 waves overlap, so that the upper limit of the sensitive area of the A0 wave The value d_H satisfies d_H >d_L +d_z ; the dotted curve corresponding to fd=x_a is the boundary of the A0 wave working area; 209) In order to improve the detection sensitivity to tiny defects, take f_a as the working area of S0 modal wave frequency, the working area of the A0 wave at the working frequency f_a is [0, d_L + d_z ].

本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

附图说明Description of drawings

本发明的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

图1为本发明一个实施例的多模态超声Lamb波层析成像流程图；Fig. 1 is a multimodal ultrasonic Lamb wave tomography flow chart of an embodiment of the present invention;

图2为本发明一个实施例的含复杂缺陷铝板的结构示意图；Fig. 2 is a schematic structural view of an aluminum plate containing complex defects according to an embodiment of the present invention;

图3a为本发明一个实施例的多模态Lamb波层析成像方法中，A0模态波工作频率选择的原理示意图；Figure 3a is a schematic diagram of the principle of A0 modal wave operating frequency selection in the multimodal Lamb wave tomography method according to an embodiment of the present invention;

图3b为本发明一个实施例的多模态Lamb波层析成像方法中，S0模态波工作频率选择的原理示意图；Fig. 3b is a schematic diagram of the principle of S0 modal wave operating frequency selection in the multimodal Lamb wave tomography method according to an embodiment of the present invention;

图4为本发明一个实施例的成像区域网格划分示意图；FIG. 4 is a schematic diagram of grid division of an imaging region according to an embodiment of the present invention;

图5为本发明一个实施例的一个实施例的成像区域及缺陷位置示意图；Fig. 5 is a schematic diagram of an imaging area and a defect location of an embodiment of an embodiment of the present invention;

图6为本发明一个实施例的使用270kHz的A0波缺陷层析成像结果；Fig. 6 is the result of defect tomography using A0 wave of 270kHz according to an embodiment of the present invention;

图7为本发明一个实施例的使用700kHz的S0波缺陷层析成像结果；Fig. 7 is the result of defect tomography using S0 wave of 700kHz according to an embodiment of the present invention;

图8为本发明一个实施例的使用多模态Lamb波(A0波和S0波)缺陷层析成像结果。FIG. 8 is a result of defect tomography using multi-modal Lamb waves (A0 wave and S0 wave) according to an embodiment of the present invention.

具体实施方式Detailed ways

下面详细描述本发明的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，仅用于解释本发明，而不能理解为对本发明的限制。Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

在本发明的描述中，需要理解的是，术语“中心”、“纵向”、“横向”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性。In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", " The orientations or positional relationships indicated by "vertical", "horizontal", "top", "bottom", "inner" and "outer" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and Simplified descriptions, rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus should not be construed as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and should not be understood as indicating or implying relative importance.

在本发明的描述中，需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本发明中的具体含义。In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

参照下面的描述和附图，将清楚本发明的实施例的这些和其他方面。在这些描述和附图中，具体公开了本发明的实施例中的一些特定实施方式，来表示实施本发明的实施例的原理的一些方式，但是应当理解，本发明的实施例的范围不受此限制。相反，本发明的实施例包括落入所附加权利要求书的精神和内涵范围内的所有变化、修改和等同物。These and other aspects of embodiments of the invention will become apparent with reference to the following description and drawings. In these descriptions and drawings, some specific implementations of the embodiments of the present invention are specifically disclosed to represent some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited by This restriction. On the contrary, the embodiments of the present invention include all changes, modifications and equivalents coming within the spirit and scope of the appended claims.

以下结合附图描述根据本发明实施例的一种多模态超声Lamb波复杂缺陷层析成像方法。A multimodal ultrasonic Lamb wave complex defect tomography method according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

1)如图2、图4和图5所示，取一块厚度为3mm的待测铝板，在其上表面选择面积为600mm×600mm的矩形作为缺陷成像区域，将该成像区域划分成120×120个小网格(即120×120个像素)；圆孔缺陷中心点位于(310mm，350mm)，缺陷区域1开口直径120mm，孔深1mm，缺陷区域2开口直径60mm，孔深2mm；在成像区域的一侧设置14个发射EMAT(电磁声换能器)，对侧相同位置处设置14个接收EMAT；收发EMAT直径为30mm，相邻EMAT中心间距为40mm。1) As shown in Figure 2, Figure 4 and Figure 5, take an aluminum plate to be tested with a thickness of 3 mm, select a rectangle with an area of 600 mm × 600 mm on its upper surface as the defect imaging area, and divide the imaging area into 120 × 120 A small grid (ie 120×120 pixels); the center point of the circular hole defect is located at (310mm, 350mm), the opening diameter of defect area 1 is 120 mm, the hole depth is 1 mm, the opening diameter of defect area 2 is 60 mm, and the hole depth is 2 mm; in the imaging area Set 14 transmitting EMATs (electromagnetic acoustic transducers) on one side of the tube, and set 14 receiving EMATs at the same position on the opposite side; the diameter of the transmitting and receiving EMATs is 30mm, and the distance between the centers of adjacent EMATs is 40mm.

2)选择AG1024型射频功率放大器激励EMAT，第一次全向激发A0模态Lamb波，14个接收EMAT依次接收Lamb波；第二次全向激发S0模态Lamb波，14个接收EMAT依次接收Lamb波；第一次激发的Lamb波为纯净单一的A0模态Lamb波；第二次激发的Lamb波为纯净单一的S0模态Lamb波。2) Select the AG1024 RF power amplifier to excite the EMAT, the first omnidirectional excitation of the A0 mode Lamb wave, the 14 receiving EMATs receive the Lamb wave in turn; the second omnidirectional excitation of the S0 mode Lamb wave, the 14 receiving EMATs receive the Lamb wave in turn Lamb wave; the Lamb wave excited for the first time is a pure and single A0 mode Lamb wave; the Lamb wave excited for the second time is a pure and single S0 mode Lamb wave.

如图3所示，A0和S0两种模态Lamb波相应的工作频率(激发频率)选择方法如下：As shown in Figure 3, the corresponding working frequencies (excitation frequencies) of the two modes of A0 and S0 Lamb waves are selected as follows:

a、定义Lamb波对板厚变化的敏感度函数：a. Define the sensitivity function of Lamb wave to plate thickness change:

SEN(f,d,Δd)＝|S_the(f,d-Δd)-S_the(f,d)|/ΔdSEN(f,d,Δd)=|S_the (f,d-Δd)-S_the (f,d)|/Δd

其中，S_the(f,d-Δd)和S_the(f,d)分别为所用模态Lamb波在缺陷区域和基础板厚区域的慢度值；f为所用模态Lamb波的工作频率；d为基础板厚；Δd为缺陷区域的板厚相比于基础板厚的减小量；(d-Δd)为缺陷区域的板厚。Among them, S_the (f,d-Δd) and S_the (f,d) are the slowness values of the used mode Lamb wave in the defect area and the base plate thickness area respectively; f is the working frequency of the used mode Lamb wave; d is the base plate thickness; Δd is the reduction of the plate thickness in the defect area compared to the base plate thickness; (d-Δd) is the plate thickness in the defect area.

b、设置Lamb波的敏感度函数SEN(f,d)的阈值TH_S：b. Set the threshold TH_S of the sensitivity function SEN(f,d) of the Lamb wave:

THs＝SNR_min×S_noise/d_minTHs＝SNR_min ×S_noise /d_min

其中，SNR_min和d_min分别为层析成像所需的最小信噪比和板厚分辨率；S_noise为噪声幅值。Among them, SNR_min and d_min are the minimum signal-to-noise ratio and plate thickness resolution required by tomography, respectively; S_noise is the noise amplitude.

c、分别计算A0波和S0波的板厚变化敏感度函数SEN(f,d)随d变化的曲线，得到两种模态波SEN(f,d)的幅值在f-d上的二维分布图；其中，工作频率f的取值为(100～1000)kHz。c. Calculate the curves of the thickness change sensitivity function SEN(f,d) of the A0 wave and the S0 wave respectively as a function of d, and obtain the two-dimensional distribution of the amplitudes of the two modal waves SEN(f,d) on f-d Figure; Among them, the value of the operating frequency f is (100 ~ 1000) kHz.

d、如图3a所示，在S0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线。d. As shown in Figure 3a, find the contour line corresponding to SEN(f,d)=THs on the SEN(f,d) distribution map of the S0 modal wave.

e、计算曲线fd＝x_s与直线d＝d₀的交点坐标，记为(d₀，f_s)，取f_s为S0模态波的工作频率。其中，fd＝x_s对应的虚线曲线是S0波工作区域的边界；d₀为铝板健康区域的板厚。e. Calculate the coordinates of the intersection point of the curve fd=x_s and the straight line d=d₀ , record it as (d₀ , f_s ), and take f_s as the operating frequency of the S0 modal wave. Among them, the dotted curve corresponding to fd=x_s is the boundary of the S0 wave working area; d₀ is the plate thickness of the healthy area of the aluminum plate.

f、计算直线f＝f_s与等高线SEN(f,d)＝THs的交点(d_L，f_s)，得到S0波在工作频率f_s下的工作区域为[d_L，d₀]。f. Calculate the intersection point (d_L , f_s ) of the straight line f=f_s and the contour line SEN(f,d)=THs, and obtain the working area of the S0 wave at the working frequency f_s as [d_L , d₀ ] .

g、如图3b所示，在A0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线。g. As shown in Figure 3b, find the contour line corresponding to SEN(f,d)=THs on the SEN(f,d) distribution map of the A0 modal wave.

h、计算曲线fd＝x_a和SEN(f,d)＝THs与直线d＝d_L+d_z的交点坐标(d_L+d_z，f_a1)和(d_L+d_z，f_a2)，取f_a1和f_a2中相对较小的一个作为A0波的工作频率f_a。其中，d_z(d_z>0)是为保证A0和S0波的敏感区域重叠而设置的一个死区，使得A0波的敏感区域的上限值d_H满足d_H>d_L+d_z；fd＝x_a对应的虚线曲线是A0波工作区域的边界。h. Calculate the intersection coordinates (d_L +d_z , f_a1 ) and (d_L +d_z , f_a2 ) of the curve fd=x_a and SEN(f,d)=THs and the straight line d=d_L +d_z , take the relatively smaller one of f_a1 and f_a2 as the working frequency f_a of the A0 wave. Among them, d_z (d_z >0) is a dead zone set up to ensure that the sensitive areas of A0 and S0 waves overlap, so that the upper limit d_H of the sensitive area of A0 wave satisfies d_H >d_L +d_z ; The dotted curve corresponding to fd=x_a is the boundary of the A0 wave working area.

i、为提高对微小缺陷的检测灵敏度，取f_a为S0模态波的工作频率。于是，得到A0波在工作频率f_a下的工作区域为[0，d_L+d_z]。i. In order to improve the detection sensitivity to tiny defects, f_a is taken as the working frequency of the S0 modal wave. Thus, the working area of the A0 wave at the working frequency f_a is [0, d_L +d_z ].

3)利用伪Wigner-Ville分布(PWVD)对14×14个A0模态EMAT检测波形和14×14个S0模态EMAT检测波形进行时频分析和模态识别；3) Perform time-frequency analysis and mode identification on 14×14 A0 mode EMAT detection waveforms and 14×14 S0 mode EMAT detection waveforms by using pseudo Wigner-Ville distribution (PWVD);

4)提取196个A0检测波形的时频分析结果并记录对应的走时T₁(A0)～T₁₉₆(A0)；提取196个S0检测波形的时频分析结果并记录对应的走时T₁(S0)～T₁₉₆(S0)。4) Extract the time-frequency analysis results of 196 A0 detection waveforms and record the corresponding travel time T₁ (A0) ~ T₁₉₆ (A0); extract the time-frequency analysis results of 196 S0 detection waveforms and record the corresponding travel time T₁ (S0 )～T₁₉₆ (S0).

5)如图4所示，使用联合迭代重建算法(SIRT)确定A0和S0模态下每个网格的慢度(速度的倒数)：5) As shown in Figure 4, the slowness (reciprocal of velocity) of each mesh in A0 and S0 modes is determined using the joint iterative reconstruction algorithm (SIRT):

${\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>i</span>i</span>}}<span><span>=</span>=</span>\underset{\mathrm{<span><span>j</span>j</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}}{\overset{\mathrm{<span><span>n</span>no</span>}}{<span><span>\&Sigma;</span>\&Sigma;</span>}}{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>i</span>i</span>}\mathrm{<span><span>j</span>j</span>}}<span><span>*</span>*</span>{\mathrm{<span><span>S</span>S</span>}}_{\mathrm{<span><span>j</span>j</span>}}<span><span>,</span>,</span><span><span>(</span>(</span>\mathrm{<span><span>i</span>i</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}<span><span>,</span>,</span>\mathrm{<span><span>2</span>2</span>}<span><span>,</span>,</span><span><span>...</span>...</span><span><span>,</span>,</span>\mathrm{<span><span>m</span>m</span>}<span><span>)</span>)</span>$

其中，S_j为待求的第j个网格的慢度；L_ij为第i条投影射线在第j个网格中的长度；T_i为第i条投影射线的实测走时；由步骤5可知，n＝120×120＝14400，m＝14×14＝196。Among them, S_j is the slowness of the j-th grid to be found; L_ij is the length of the i-th projected ray in the j-th grid; T_i is the measured travel time of the i-th projected ray; by step 5 It can be seen that n=120×120=14400, m=14×14=196.

6)使用图像融合技术(Lamb波的频散关系)，将A0模态和S0模态下得到的两组慢度分布结果转化为板厚分布结果，再进行叠加，并求取平均，从而得到最终的缺陷分布结果。6) Using image fusion technology (the dispersion relationship of Lamb waves), the two sets of slowness distribution results obtained in A0 mode and S0 mode are converted into plate thickness distribution results, and then superimposed and averaged to obtain The final defect distribution result.

经过计算，如图6、图7和图8所示，针对深度逐渐变化的复杂缺陷而言，相比于单一模态Lamb波跨孔层析成像，配合使用A0模态和S0模态Lamb波得到的成像结果噪声干扰更小，成像精度更高。After calculation, as shown in Fig. 6, Fig. 7 and Fig. 8, for complex defects with gradually changing depths, compared with single-mode Lamb wave trans-hole tomography, the combination of A0 mode and S0 mode Lamb wave The obtained imaging results have less noise interference and higher imaging accuracy.

另外，本发明实施例的一种多模态超声Lamb波复杂缺陷层析成像方法的其它构成以及作用对于本领域的技术人员而言都是已知的，为了减少冗余，不做赘述。In addition, other components and functions of a multimodal ultrasonic Lamb wave complex defect tomography method according to the embodiment of the present invention are known to those skilled in the art, and will not be repeated in order to reduce redundancy.

在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本发明的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不一定指的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施例或示例中以合适的方式结合。In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

尽管已经示出和描述了本发明的实施例，本领域的普通技术人员可以理解：在不脱离本发明的原理和宗旨的情况下可以对这些实施例进行多种变化、修改、替换和变型，本发明的范围由权利要求及其等同限定。Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (4)

Translated fromChinese

1.一种多模态超声Lamb波复杂缺陷层析成像方法，其特征在于，包括如下步骤：1. a multimodal ultrasonic Lamb wave complex defect tomography method, is characterized in that, comprises the steps:1)在待测板材上选择一个矩形区域作为缺陷层的成像区域，将所述成像区域横纵分割成N₁×N₂个网格；在所述成像区域的一侧设置M个发射电磁声换能器，在所述成像区域与所述发射磁声换能器的相对侧设置M个接收电磁声换能器；其中，N₁、N₂、M为自然数；1) Select a rectangular area on the plate to be tested as the imaging area of the defect layer, divide the imaging area into N₁ ×N₂ grids horizontally and vertically; For the transducer, M receiving electromagnetic acoustic transducers are arranged on the opposite side of the imaging area and the emitting magnetic acoustic transducer; wherein, N₁ , N₂ , and M are natural numbers;2)使用射频功率放大器分两次激励所述M个发射电磁声换能器，其中，第一次全向激发A0模态Lamb波，所述M个接收电磁声换能器依次接收所述A0模态Lamb波；2) Use a radio frequency power amplifier to excite the M emitting electromagnetic acoustic transducers twice, wherein, the first omnidirectional excitation of the A0 modal Lamb wave, and the M receiving electromagnetic acoustic transducers receive the A0 modal Lamb waves in turn. Modal Lamb wave;第二次全向激发S0模态Lamb波，M个接收电磁声换能器依次接收所述A0模态Lamb波；Exciting the S0 mode Lamb wave omnidirectionally for the second time, and the M receiving electromagnetic acoustic transducers receive the A0 mode Lamb wave in turn;3)利用伪Wigner-Ville分布对M×M个A0模态电磁声换能器检测波形和M×M个S0模态电磁声换能器检测波形进行时频分析和模态识别；3) Time-frequency analysis and mode identification are performed on the detection waveforms of M×M A0 mode electromagnetic acoustic transducers and M×M S0 mode electromagnetic acoustic transducers by using the pseudo Wigner-Ville distribution;4)提取所述M×M个A0电磁声换能器检测波形的时频分析结果并记录对应的走时T₁(A0)～T_M×M(A0)；提取所述M×M个S0电磁声换能器检测波形的时频分析结果并记录对应的走时T₁(S0)～T_M×M(S0)；4) Extract the time-frequency analysis results of the detected waveforms of the M×M A0 electromagnetic acoustic transducers and record the corresponding travel time T₁ (A0)～T_M×M (A0); extract the M×M S0 electromagnetic The sound transducer detects the time-frequency analysis results of the waveform and records the corresponding travel time T₁ (S0)～_TM×M (S0);5)使用联合迭代重建算法确定所述A0模态和所述S0模态下所述N₁×N₂个网格中每个网格的慢度：5) Using a joint iterative reconstruction algorithm to determine the slowness of each grid in the N₁ ×N₂ grids under the A0 mode and the S0 mode:$\begin{array}{cc}{\mathrm{<span><span>T</span>T</span>}}_{\mathrm{<span><span>i</span>i</span>}}<span><span>=</span>=</span>\underset{\mathrm{<span><span>j</span>j</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}}{\overset{\mathrm{<span><span>n</span>no</span>}}{<span><span>\&Sigma;</span>\&Sigma;</span>}}{\mathrm{<span><span>L</span>L</span>}}_{\mathrm{<span><span>i</span>i</span>}\mathrm{<span><span>j</span>j</span>}}<span><span>*</span>*</span>{\mathrm{<span><span>S</span>S</span>}}_{\mathrm{<span><span>j</span>j</span>}}& <span><span>(</span>(</span>\mathrm{<span><span>i</span>i</span>}<span><span>=</span>=</span>\mathrm{<span><span>1</span>1</span>}<span><span>,</span>,</span>\mathrm{<span><span>2</span>2</span>}<span><span>,</span>,</span>\mathrm{<span><span>...</span>...</span>}<span><span>,</span>,</span>\mathrm{<span><span>m</span>m</span>}<span><span>)</span>)</span>\end{array}$其中，S_j为待求的第j个网格的慢度；L_ij为第i条投影射线在第j个网格中的长度；T_i为第i条投影射线的实测走时；n为正整数，且n＝N₁×N₂；m为正整数，且m＝M×M；Among them, S_j is the slowness of the j-th grid to be obtained; L_ij is the length of the i-th projected ray in the j-th grid; T_i is the measured travel time of the i-th projected ray; n is positive Integer, and n=N₁ ×N₂ ; m is a positive integer, and m=M×M;6)使用图像融合方法将所述A0模态和所述S0模态下得到的两组慢度分布结果转化为板厚分布结果，再进行叠加，并求取平均，从而得到最终的缺陷分布结果。6) Using the image fusion method to convert the two sets of slowness distribution results obtained under the A0 mode and the S0 mode into plate thickness distribution results, and then superimpose and calculate the average to obtain the final defect distribution results .2.根据权利要求1所述的一种多模态超声Lamb波复杂缺陷层析成像方法，其特征在于，步骤1)中，所述发射电磁声换能器和所述接收电磁声换能器直径范围均为20～60mm，相邻所述发射电磁声换能器和所述接收电磁声换能器的中心间距均为30～90mm。2. a kind of multimodal ultrasonic Lamb wave complex defect tomography method according to claim 1, is characterized in that, in step 1), described transmitting electromagnetic acoustic transducer and described receiving electromagnetic acoustic transducer The diameters range from 20 to 60 mm, and the center-to-center distances between adjacent transmitting electromagnetic acoustic transducers and receiving electromagnetic acoustic transducers are both 30 to 90 mm.3.根据权利要求1所述的一种多模态超声Lamb波复杂缺陷层析成像方法，其特征在于，步骤2)中，所述射频功率放大器的激发频率为100～1000kHz；第一次激发的Lamb波为纯净单一的A0模态Lamb波；第二次激发的Lamb波为纯净单一的S0模态Lamb波。3. A kind of multimodal ultrasonic Lamb wave complex defect tomography method according to claim 1, is characterized in that, in step 2), the excitation frequency of described RF power amplifier is 100～1000kHz; The first Lamb wave is a pure and single A0 mode Lamb wave; the second excited Lamb wave is a pure and single S0 mode Lamb wave.4.根据权利要求1所述的一种多模态超声Lamb波复杂缺陷层析成像方法，其特征在于：步骤2)中，所述A0模态Lamb波和所述S0模态Lamb波的激发频率方法进一步包括：4. a kind of multimodal ultrasonic Lamb wave complex defect tomography method according to claim 1, is characterized in that: in step 2), the excitation of described A0 modal Lamb wave and described S0 modal Lamb wave Frequency methods further include:201)定义Lamb波对板厚变化的敏感度函数：201) Define the sensitivity function of Lamb wave to plate thickness change:SEN(f,d,Δd)＝|S_the(f,d-Δd)-S_the(f,d)|/ΔdSEN(f,d,Δd)=|S_the (f,d-Δd)-S_the (f,d)|/Δd其中，S_the(f,d-Δd)和S_the(f,d)分别为所用模态Lamb波在缺陷区域和基础板厚区域的慢度值；f为所用模态Lamb波的工作频率；d为基础板厚；Δd为缺陷区域的板厚相比于基础板厚的减小量；(d-Δd)为缺陷区域的板厚；Among them, S_the (f,d-Δd) and S_the (f,d) are the slowness values of the used mode Lamb wave in the defect area and the base plate thickness area respectively; f is the working frequency of the used mode Lamb wave; d is the base plate thickness; Δd is the reduction of the plate thickness in the defect area compared to the base plate thickness; (d-Δd) is the plate thickness in the defect area;202)设置Lamb波敏感度函数SEN(f,d)的阈值TH_S：202) Setting the threshold TH_S of the Lamb wave sensitivity function SEN(f,d):THs＝SNR_min×S_noise/d_minTHs＝SNR_min ×S_noise /d_min其中，SNR_min和d_min分别为层析成像所需的最小信噪比和板厚分辨率；S_noise为噪声幅值；Among them, SNR_min and d_min are the minimum signal-to-noise ratio and plate thickness resolution required by tomography, respectively; S_noise is the noise amplitude;203)分别计算所述A0波和所述S0波的板厚变化敏感度函数SEN(f,d)随d变化的曲线，得到两种模态波SEN(f,d)的幅值在f-d上的二维分布图；其中，工作频率f的取值为100～1000kHz；203) Calculate the curves of the plate thickness change sensitivity function SEN(f,d) of the A0 wave and the S0 wave as a function of d, and obtain the amplitudes of the two modal waves SEN(f,d) on f-d The two-dimensional distribution diagram of ; where, the value of the working frequency f is 100 ~ 1000kHz;204)在所述S0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线；204) On the SEN(f,d) distribution map of the S0 modal wave, find the contour line corresponding to SEN(f,d)=THs;205)计算曲线fd＝x_s与直线d＝d₀的交点坐标，记为(d₀，f_s)，取f_s为S0模态波的工作频率；其中，所述fd＝x_s对应的虚线曲线是S0波工作区域的边界；d₀为铝板健康区域的板厚；205) Calculate the coordinates of the intersection point of the curve fd=x_s and the straight line d=d₀ , denoted as (d₀ , f_s ), take f_s as the operating frequency of the S0 modal wave; wherein, the fd=x_s corresponds to The dotted curve is the boundary of the S0 wave working area; d₀ is the plate thickness of the healthy area of the aluminum plate;206)计算直线f＝f_s与等高线SEN(f,d)＝THs的交点(d_L，f_s)，得到S0波在工作频率f_s下的工作区域为[d_L，d₀]；206) Calculate the intersection point (d_L , f_s ) of the straight line f=f_s and the contour line SEN(f,d)=THs, and obtain the working area of the S0 wave at the working frequency f_s as [d_L , d₀ ] ;207)在所述A0模态波的SEN(f,d)分布图上，找到SEN(f,d)＝THs对应的等高线；207) On the SEN(f,d) distribution map of the A0 modal wave, find the contour line corresponding to SEN(f,d)=THs;208)计算曲线fd＝x_a和SEN(f,d)＝THs与直线d＝d_L+d_z的交点坐标(d_L+d_z，f_a1)和(d_L+d_z，f_a2)，取f_a1和f_a2中相对较小的一个作为A0波的工作频率f_a；其中，d_z(d_z>0)是为保证A0和S0波的敏感区域重叠而设置的一个死区，使得A0波的敏感区域的上限值d_H满足d_H>d_L+d_z；fd＝x_a对应的虚线曲线是A0波工作区域的边界；208) Calculate the intersection coordinates (d_L +d_z , f_a1 ) and (d_L +d_z , f_a2 ) of the curve fd=x_a and SEN(f, d)=THs and the straight line d=d_L +d_z , take the relatively smaller one of f_a1 and f_a2 as the working frequency f_a of A0 wave; among them, d_z (d_z >0) is a dead zone set to ensure that the sensitive areas of A0 and S0 waves overlap, Make the upper limit d_H of the sensitive area of the A0 wave satisfy d_H >d_L +d_z ; the dotted curve corresponding to fd=x_a is the boundary of the A0 wave working area;209)为提高对微小缺陷的检测灵敏度，取f_a为S0模态波的工作频率，得到A0波在工作频率f_a下的工作区域为[0，d_L+d_z]。209) In order to improve the detection sensitivity for tiny defects, f_a is taken as the operating frequency of the S0 modal wave, and the working area of the A0 wave at the operating frequency f_a is [0, d_L + d_z ].