期刊文献+
共找到14篇文章
< 1 >
每页显示 20 50 100
Research on Electromagnetic Acoustic Emission Signal Recognition Based on Local Mean Decomposition and Least Squares Support Vector Machine
1
作者 Chenglong Yang Yushu Lai Qiuyue Li 《Journal of Computer and Communications》 2023年第5期70-83,共14页
Electromagnetic acoustic emission technology is one of nondestructive testing, which can be used for defect detection of metal specimens. In this study, round and cracked metal specimens, round metal specimens, and in... Electromagnetic acoustic emission technology is one of nondestructive testing, which can be used for defect detection of metal specimens. In this study, round and cracked metal specimens, round metal specimens, and intact metal specimens were prepared. And the electromagnetic acoustic emission signals of the three specimens were collected. In addition, the local mean decomposition(LMD), Autoregressive model(AR model) and least squares support vector machine (LSSVM) algorithms were combined to identify the eletromagnetic acoustic emission signals of round and cracked, round, and intact specimens. According to the algorithm recognition results, the recognition accuracy of can reach above 97.5%, which has a higher recognition rate compared with SVM and BP neural network. The results of the study show that the algorithm is able to identify quickly and accurately crack defect in metal specimens. 展开更多
关键词 electromagnetic Acoustic Emission Technology LMD LSSVM Defect Detection of Metal Crack
下载PDF
Modeling and finite element analysis of transduction process of electromagnetic acoustic transducers for nonferromagnetic metal material testing 被引量:13
2
作者 郝宽胜 黄松岭 +2 位作者 赵伟 段汝娇 王珅 《Journal of Central South University》 SCIE EI CAS 2011年第3期749-754,共6页
Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer (EMAT), a... Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer (EMAT), a multi-field coupled model was established and the finite element method (FEM) was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected. 展开更多
关键词 metal material nondestructive testing electromagnetic acoustic transducer multi-field coupling Garlerkin method finite element
下载PDF
Excitation and Detection of Shear Horizontal Waves with Electromagnetic Acoustic Transducers for Nondestructive Testing of Plates 被引量:13
3
作者 MA Qingzeng JIAO Jingpin +3 位作者 HU Ping ZHONG Xi WU Bin HE Cunfu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2014年第2期428-436,共9页
The fundamental shear horizontal(SH0) wave has several unique features that are attractive for long-range nondestructive testing(NDT). By a careful design of the geometric configuration, electromagnetic acoustic t... The fundamental shear horizontal(SH0) wave has several unique features that are attractive for long-range nondestructive testing(NDT). By a careful design of the geometric configuration, electromagnetic acoustic transducers(EMATs) have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal(SH) waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet(PPM) EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization. 展开更多
关键词 electromagnetic acoustic transducers shear-horizontal waves strip plate nondestructive testing
下载PDF
Lamb wave signal selective enhancement by an improved design of meander-coil electromagnetic acoustic transducer 被引量:3
4
作者 Wen-Xiu Sun Guo-Qiang Liu +1 位作者 Hui Xla Zheng-Wu Xia 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第8期308-314,共7页
In this paper, we investigate a method of selectively enhancing the single mode signal of a Lamb wave by using a meander-coil electromagnetic acoustic transducer (EMAT) with a new magnetic configuration. We use the ... In this paper, we investigate a method of selectively enhancing the single mode signal of a Lamb wave by using a meander-coil electromagnetic acoustic transducer (EMAT) with a new magnetic configuration. We use the Lamb antisym- metric (A0) mode and symmetric (SO) mode as an example for analysis. The analytical expression of the magnitude of the spatial Fourier transform of the Lorentz force generated by different meander coils is used to determine the optimal driving frequency for single mode generation. The numerical calculation is used to characterize the new magnetic configuration and the conventional EMAT magnet. Experimental examinations of each meander coil in combination with the conventional and new magnetic configuration show that the Lamb wave signal can be selectively enhanced by choosing the appropriate driving frequency and coil parameters through using the improved meander-coil EMAT. 展开更多
关键词 Lamb wave selective enhancement meander-coil electromagnetic acoustic transducer (EMAT)
下载PDF
Circuit-field coupled finite element analysis method for an electromagnetic acoustic transducer under pulsed voltage excitation 被引量:1
5
作者 郝宽胜 黄松岭 +1 位作者 赵伟 王珅 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第6期490-497,共8页
This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs i... This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting's theorem. Then the currents under different frequencies are calculated according to Ohm's law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Furthermore, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied. 展开更多
关键词 electromagnetic acoustic transducer nondestructive testing circuit-field coupling finite element method
下载PDF
Selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers 被引量:1
6
作者 李明亮 邓明晰 高广健 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第12期1-8,共8页
In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers (EMATs). With the modal expansion approach for wave... In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers (EMATs). With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave's mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT's meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT's geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated (strengthened or restrained) by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs. 展开更多
关键词 ultrasonic Lamb waves selective generation electromagnetic acoustic transducer (EMAT) Lorentz surface stress
下载PDF
Damage evolution law of coal-rock under uniaxial compression based on the electromagnetic radiation characteristics 被引量:8
7
作者 Jin Peijian Wang Enyuan +2 位作者 Liu Xiaofei Huang Ning Wang Siheng 《International Journal of Mining Science and Technology》 SCIE EI 2013年第2期221-227,共7页
Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered re... Based on electromagnetic radiation characteristics, the present research studied the damage evolution of rock under uniaxial compression. Besides, this research built the coal-rock damage evolution model considered residual strength. The applicability and accuracy of the model were verified through experiments. The results show that coal-rock damage evolution consists of four periods. The first period is from the beginning of compression to nearly 20% of the stress peak value, during which the damage variable changes stably about 0.1, and accordingly a few of electromagnetic radiation signals emerge. The second period is from about 20% to 70% of the stress peak value. The damage has stable development, and the parameter of electromagnetic radiation characteristics turns larger continuously with the increase of stress. The third period is when the damage has accelerated development, the coal-rock was broken which result from sharp increasing of the damage variable, meanwhile a great quantity of electromagnetic radiation signals emerge. The fourth period is after the coal-rock fracture, during which the damage variable corresponding to the parameter of electromagnetic radiation characteristics has a stable development. This research has great academic and realistic significance for further studies the electromagnetic radiation characteristics of coal-rock under loading and damage and the forecasting of coal-rock dynamic disasters. 展开更多
关键词 electromagnetic radiation (EMR) Acoustic emission (AE) Uniaxial compression Damage evolution
下载PDF
Comparison of three formulations for eddy-current problems in a spiral coil electromagnetic acoustic transducer
8
作者 石文泽 吴运新 +3 位作者 龚海 赵志然 范吉志 谭良辰 《Journal of Central South University》 SCIE EI CAS CSCD 2016年第4期817-824,共8页
Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density (TCD). Formulations II and {I1 are based on inc... Three differential equations based on different definitions of current density are compared. Formulation I is based on an incomplete equation for total current density (TCD). Formulations II and {I1 are based on incomplete and complete equations for source current density (SCD), respectively. Using the weak form of finite element method (FEM), three formulations were applied in a spiral coil electromagnetic acoustic transducer (EMAT) example to solve magnetic vector potential (MVP). The input impedances calculated by Formulation III are in excellent agreement with the experimental measurements. Results show that the errors for Formulations I & II vary with coil diameter, coil spacing, lift-off distance and external excitation frequency, for the existence of eddy-current and skin & proximity effects. And the current distribution across the coil conductor also follows the same trend. It is better to choose Formulation I instead of Formulation Ili to solve MVP when the coil diameter is less than twice the skin depth for Formulation I is a low cost and high efficiency calculation method. 展开更多
关键词 electromagnetic acoustic transducer (EMAT) eddy current finite element method (FEM) skin and proximity effects spiral coil
下载PDF
Optimal Design of Electromagnetic Acoustic Transducer
9
作者 Eiji Matsumoto Shinji Kitamura Jun Abe 《Journal of Energy and Power Engineering》 2012年第4期561-569,共9页
This paper considers the design of EMAT (Electro-Magnetic Acoustic Transducer) based on numerical simulation. The EMAT consists of an exiting coil and two permanent magnets, which transmits the ultrasonic wave by th... This paper considers the design of EMAT (Electro-Magnetic Acoustic Transducer) based on numerical simulation. The EMAT consists of an exiting coil and two permanent magnets, which transmits the ultrasonic wave by the Lorentz force between the eddy current and the static magnetic field by the magnets. From the experimental result on self-prepared EMATs, the intensity and the directivity of the transmitted wave depend on the widths of the coil and the magnets. By means of EEM analysis the authors attempt to determine the optimal values of the above widths such that both the intensity and the directivity achieve the maximum or allowable performance. 展开更多
关键词 acoustics actuators eddy current electromagnetic acoustic transducer finite element methods magnetic forces SENSORS
下载PDF
Micro-Sized Pinhole Inspection with Segmented Time Reversal and High-Order Modes Cluster Lamb Waves Based on EMATs
10
作者 Jinjie Zhou Yang Hu +3 位作者 Xiang Li Yang Zheng Sanhu Yang Yao Liu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第1期224-236,共13页
Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspect... Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection. 展开更多
关键词 Pinhole corrosion High-order modes cluster Lamb waves Segmented time reversal inspection electromagnetic acoustic transducer
下载PDF
Transformation method and wave control 被引量:3
11
作者 Zheng Chang Jin Hu Geng-Kai Hu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2010年第6期889-898,共10页
Transformation method provides an efficient way to control wave propagation by materials.The transformed relations for field and material during a transformation are essential to fulfill this method.We propose a syste... Transformation method provides an efficient way to control wave propagation by materials.The transformed relations for field and material during a transformation are essential to fulfill this method.We propose a systematic method to derive the transformed relations for a general physic process,the constraint conditions are obtained by considering geometrical and physical constraint during a mapping. The proposed method is applied to Navier's equation for elastodynamics,Helmholtz's equation for acoustic wave and Maxwell's equation for electromagnetic wave,the corresponding transformed relations are derived,which can be used in the framework of transformation method for wave control.We show that contrary to electromagnetic wave,the transformed relations are not uniquely determined for elastic wave and acoustic wave,so we have a freedom to choose them differently.Using the obtained transformed relations,we also provide some examples for device design,a concentrator for elastic wave,devices for illusion acoustic and illusion optics are conceived and validated by numerical simulations. 展开更多
关键词 Wave control Elastic wave Acoustic wave electromagnetic wave Local affine transformation
下载PDF
Single SH guided wave mode generation method for PPM EMATs 被引量:1
12
作者 Guo-Fu Zhai Yong-Qian Li 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第5期326-332,共7页
Using periodic permanent magnet(PPM)electromagnetic acoustic transducers(EMATs),different shear horizontal(SH)guided wave modes can form simultaneously in some situations,which can interfere with the inspection.The ma... Using periodic permanent magnet(PPM)electromagnetic acoustic transducers(EMATs),different shear horizontal(SH)guided wave modes can form simultaneously in some situations,which can interfere with the inspection.The main cause of this phenomenon(typically named multiple modes)is related to the frequency bandwidth of excitation signals and the transducer spatial bandwidth.Simply narrowing the frequency bandwidth cannot effectively limit the number of different SH modes.Previous researches showed that unnecessary SH wave modes can be eliminated by using dual EMATs.However,in practical applications,it is more convenient to change the excitation frequency than to use dual EMATs.In this paper,the stress boundary conditions of the PPM-EMAT are analyzed,the analytical expression of SH guided wave is established,and the magnitude of SH guided wave mode under continuous tone and tone-burst input is obtained.A method to generate a single SH mode by re-selecting an operating point is proposed.Furthermore,the influence of the frequency bandwidth of the tone-burst signal is analyzed.Finally,a single SH mode excitation is achieved with tone-burst input. 展开更多
关键词 operating point multiple modes SH guided waves electromagnetic acoustic transducer(EMAT)
下载PDF
INITIAL VALUE TECHNIQUES FOR THE HELMHOLTZ AND MAXWELL EQUATIONS 被引量:2
13
作者 Frank Natterer Olga Klyubina 《Journal of Computational Mathematics》 SCIE CSCD 2007年第3期368-373,共6页
We study the initial value problem of the Helmholtz equation with spatially variable wave number. We show that it can be stabilized by suppressing the evanescent waves. The stabilized Helmholtz equation can be solved ... We study the initial value problem of the Helmholtz equation with spatially variable wave number. We show that it can be stabilized by suppressing the evanescent waves. The stabilized Helmholtz equation can be solved numerically by a marching scheme combined with FFT. The resulting algorithm has complexity n^2 log n on a n x n grid. We demonstrate the efficacy of the method by numerical examples with caustics. For the Maxwell equation the same treatment is possible after reducing it to a second order system. We show how the method can be used for inverse problems arising in acoustic tomography and microwave imaging. 展开更多
关键词 Stability of elliptic initial value problems Parabolic wave equation Inverseproblems in acoustics and electromagnetics.
原文传递
Research on Online Texture Measurements in Metal Rolling Field
14
作者 何飞 殷安民 杨荃 《Journal of Shanghai Jiaotong university(Science)》 EI 2012年第6期690-696,共7页
In rolled strip material,the orientation of the crystallites,known as texture,is influenced by various kinds of thermo-mechanical processes,such as casting,plastic deformation,annealing and phase transformation. The m... In rolled strip material,the orientation of the crystallites,known as texture,is influenced by various kinds of thermo-mechanical processes,such as casting,plastic deformation,annealing and phase transformation. The modern industry production requires stable product performance,real-time monitoring and full controlling of the quality.The online texture measurement in metal rolling can be used to real-time monitor the whole process, and then feedback control to the production process can be implied to adjust the process parameters to ensure the stability of the products.The principles,advantages and disadvantages of related detection methods(2D X-ray diffraction,neutron diffraction,laser-ultrasonics and electromagnetic acoustic transducers(EMAT)) and the possibility of online measurement are discussed.Finally,2D X-ray diffraction and laser-ultrasonics are employed on online texture measurement,and the schemes of online texture measurement are proposed. 展开更多
关键词 texture measurement 2D X-ray diffraction laser-ultrasonics electromagnetic acoustic transducers neutron diffraction
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部