1、硕士学位论文铁磁材料电磁超声检测数值模拟方法及应用研究申请人：学科专业：力学指导教师： 年 月摘 要I论文题目：铁磁材料电磁超声检测数值模拟方法及应用研究学科专业：力学申 请 人 ：指导教师：摘 要电磁超声无损检测技术由于无需耦合剂、检测速度快及可以灵活产生各种波形等优点而被应用于众多领域。电磁超声将传统超声检测技术的应用扩展到高温、高速和在线检测等领域。然而由于电磁超声换能器(EMAT Electromagnetic Acoustic Transducer)的电声转换效率低及本身的复杂性，限制了其在实际工程中的广泛应用。目前，对磁性材料电磁超声无损检测的研究主要采用实验方法。由于数值模拟不仅
2、有助于更好理解电磁超声无损检测的机理及特性，而且可为探头的优化设计和缺陷的定量分析提供手段，开发有效的磁性材料电磁超声数值模拟程序很有必要。针对以上背景，本论文主要研究铁磁性材料电磁超声无损检测技术相关的数值模拟方法、程序和应用。主要研究内容包括：首先基于电磁场理论和波动方程建立铁磁材料电磁超声无损检测的数值计算方法，并开发相应的数值模拟程序；其次搭建电磁超声实验系统并进行实验，通过与实验结果比较验证数值模拟程序；最后，研究了EMAT 对钢板减薄检测的有效性。具体内容包括：（1）以麦克斯韦方程为理论基础，基于等效磁极化法建立了铁磁材料内部磁场强度和磁导率分布的数值计算方法，并开发了相应的数值模
3、拟程序。采用该数值模拟程序分别计算了 EMAT 中两种常见永久磁体作用下的强磁性材料内部磁场及相对磁导率分布。（2）外加非均匀偏置磁场作用下，铁磁材料内部的磁导率随位置的变化而不同。基于已有的 Ar 法瞬态涡流场计算程序，建立了分布磁导率条件下的铁磁材料内部涡流分布的数值计算程序，并研究了相对磁导率对涡流分布的影响。（3）对于铁磁材料而言，由于外加静态偏置磁场和涡流场的相互作用，铁磁材料表现出与非磁性材料不同的性质，即存在磁化效应和磁致伸缩效应。对于铁磁材料电磁超声无损检测数值模拟，本研究不仅考虑了洛伦兹力，而且还考虑了磁化体力和磁致伸缩体力的影响。具体推导了磁化体力和磁致伸缩体力的计算公式，
4、并开发了相应的数值计算程序。（4）建立了基于有限元理论，考虑洛伦兹力、磁化体力和磁致伸缩体力的电磁超声超声场数值模拟方法和程序。最后通过与实验结果进行比较验证了数值模拟程序的正确性。（5）搭建了电磁超声实验系统，并进行相关的实验研究，将电磁超声无损检测技西安交通大学硕士学位论文II术应用于铁磁材料检测中。针对碳素钢板减薄问题，采用横波垂直入射的模型，研究电磁超声技术对不同减薄厚度的检测能力。关 键 词：电磁超声；无损检测；有限元法；数值模拟；铁磁材料论文类型：应用基础本研究得到国家磁约束聚变项目（GB113005） ，国家自然科学基金（51277139, 11021202)及国家 973 项目
5、（2011CB610303）资助ABSTRACT IIITitle: Development and Application of Numerical Simulation Method for EMAT of Ferromagnetic Materials Specialty: MechanicsApplicant: Haiqiang ZhouSupervisor: Prof. Zhenmao ChenABSTRACTDue to features of no physical contact between transducer and test-piece, fast detection
6、 speed, and various wave patterns, the Electromagnetic Acoustic Testing was applied in many industrial fields. It can not only improve the inspection efficiency but also can extend the application area of UT to the fields of high temperature, high speed and on-line inspection. However, due to the co
7、mplicity of Electromagnetic Acoustic Transducer(EMAT) and its low energy transition efficiency, there are still several problems for its broad application in engineering. At present, studies on the EMAT are mainly by means of experiment for ferromagnetic material. As the numerical simulation techniq
8、ue can not only help to have a better understand on the mechanism and property evaluation of the EMAT, but also can provide a useful tool for the transducers optimization design and the defects sizing. To developed numerical simulation method for EMAT of ferromagnetic material and structures is very
9、 important.Based on this background, this thesis focus on the development of a simulation method and the corresponding numerical code for the EMAT of ferromagnetic material. The major works include establishment of the numerical simulation method and development of the corresponding numerical code f
10、or ferromagnetic materials based on the static electromagnetic field theory and the wave equations, validation of the numerical method through conducting EMAT experiments and comparing the experimental results with simulated ones, application of EMAT to wall thinning detection of ferromagnetic plate
11、. The detailed research work and major results are as follows:(1) Based on the theory of Maxwells equations and Equivalent Magnetic Polarization Method(EMPM), a numerical simulation method for calculating magnetic field and permeability in the ferromagnetic material was established. As example, the
12、distributions of the magnetic field and the relative permeability were calculated for plate specimen with two typical permanent magnets structures of EMAT. (2) Considering the non-uniform bias magnetic field, the relative permeability is also not uniform in the inspection target specimen of ferromag
13、netic material. In view of this, The ECT code of Ar method was upgraded to treat the distributed permeability, which is 西安交通大学硕士学位论文IVpredicted with the equivalent polarization code. By using the developed code, the influence of the permeability on the eddy current was studied.(3) For ferromagnetic
14、materials, because of the effects of the bias magnetic field and the eddy current, not only the Lorentz force, but also the magnetization force and the magnetostrictive force can be generated. Magnetization effect and magnetostrictive effect play a very important role to generate ultrasonic wave of
15、EMAT. The calculation method and the numerical simulation code to deal with the magnetization force and the magnetostriction force were established.(4) Based on the finite element method, a numerical simulation method was developed for simulation of the ultrasonic wave in ferromagnetic material due
16、to all the Lorentz force, the magnetization force and magnetostrictive force. The developed EMAT code was validated verified by comparing its results with the experimental results obtained with a home made EMAT system. (5) To extend the application of EMAT to the wall thinning of a ferromagnetic pla
17、te, a shear wave EMAT probe of vertical incidence type was developed and is used to detect the wall thinning of 20 mm thick carbon steel plate. Both the experimental and numerical results reveal that EMAT method is very suitable for the detection of wall thinning of ferromagnetic material.KEY WORDS:
18、 Electromagnetic Acoustic Testing; Nondestructive Evaluation; FEM; Numerical Simulation Method; Ferromagnetic Materials TYPE OF THESIS: Application Fundamentals*This study is supported by National Magnetic Confinement Fusion Program of China (Grant.GB113005), the Natural Science Foundation of China
19、(Grant No. 51277139, 11021202) and the National Basic Research Program of China (Grant No.2011CB610303)目 录V目 录1 绪 论 .11.1 研究背景及意义 .11.2 铁磁材料无损检测的研究现状 .11.2.1 铁磁材料无损检测方法概述 .11.2.2 电磁超声无损检测技术概述 .21.3 电磁超声无损检测的研究现状 .31.4 论文研究目标及内容框架 .52 电磁超声无损检测基本理论 .62.1 电磁超声无损检测的基本原理 .62.2 电磁超声数值模拟的电磁场基本理论方法 .72.2.1
20、基于等效磁极化法的磁性介质静态磁场数值计算方法 .72.2.2 基于 Ar 法和棱边元的涡流场计算方法 .102.2.3 磁化效应 .162.2.4 磁致伸缩效应 .162.3 超声波的有限元数值模拟方法 .172.3.1 二维超声波的有限元数值模拟方法 .182.3.2 三维超声波的有限元数值模拟方法 .213 铁磁材料电磁超声无损检测的数值模拟 .253.1 铁磁材料内部磁场的数值计算 .253.1.1 数值模拟程序的开发 .253.1.2 磁场和相对磁导率的计算 .263.2 铁磁材料涡流场和洛伦兹力的数值计算 .283.2.1 数值计算方法的建立 .283.2.2 数值计算实例 .29
21、3.3 磁化体力及磁致伸缩体力计算 .333.3.1 磁化体力计算 .333.3.2 磁致伸缩体力计算 .343.4 电磁超声检出信号数值计算方法 .393.5 铁磁材料电磁超声二维有限元数值模拟 .403.5.1 铁磁材料电磁超声数值模拟程序的开发 .403.5.2 数值计算实例 .403.6 铁磁材料电磁超声三维有限元数值模拟 .443.6.1 数值计算模型的建立 .443.6.2 数值计算结果及分析 .44西安交通大学硕士学位论文VI3.7 本章小结 .464 铁磁材料电磁超声无损检测的实验研究 .474.1 电磁超声无损检测实验系统 .474.2 电磁超声换能器的设计 .484.2.1
22、 偏置磁场设计 .484.2.2 激励线圈设计 .494.3 铁磁材料电磁超声实验结果 .494.4 铁磁材料电磁超声数值模拟程序的实验验证 .514.5 本章小结 .525 电磁超声技术在碳素钢板减薄上的应用 .535.1 碳素钢板减薄的电磁超声数值模拟研究 .535.1.1 数值计算模型的建立 .535.1.2 数值计算结果 .535.2 碳素钢板减薄的电磁超声实验研究 .555.3 本章小结 .576 总结与展望 .586.1 主要工作和结论 .586.2 研究工作展望 .59参考文献 .60致 谢 .63攻读学位期间获得的研究成果 .64声明CONTENTSVIICONTENTS1 P
23、reface.11.1 Research background and motivation .11.2 Research status of ferromagnetic material inspection.11.2.1 Introduction of NDT for ferromagnetic materials.11.2.2 Introduction of EMAT technique.21.3 Research status of EMAT technique.31.4 Objectives and main works .52 Basic theories and methods
24、of EMAT .62.1 Basic principles of EMAT .62.2 Numerical simulation methods of electromagnetic field in EMAT.72.2.1 Numerical calculation of magnetic field based on EMPM .72.2.2 Ar method and FEM in numerical simulation of eddy current .102.2.3 Magnetization.162.2.4 Magnetostriction .162.3 Numerical s
25、imulation for ultrasonic wave based on FEM.172.3.1 Two-dimensional FEM simulation method of ultrasonic wave.182.3.2 Three-dimensional FEM simulation method of ultrasonic wave.213 Numerical simulation of ferromagnetic materials of EMAT.253.1 Calculation of magnetic field in ferromagnetic materials.25
26、3.1.1 Development of numerical simulation code.253.1.2 Calculation of magnetic field and relative permeability .363.2 Calculation of eddy current and Lorentz force in ferromagnetic materials .283.2.1 Establishment of numerical model.283.2.2 Examples of numerical simulation.293.3 Calculation of magne
27、tization force and magnetostriction force .333.3.1 Magnetization force .333.3.2 Magnetostriction force .343.4 Numerical calculation of pickup signal for EMAT.393.5 2D numerical simulation of EMAT for ferromagnetic materials.403.5.1 Development of numerical simulation code.403.5.2 Examples of numeric
28、al simulation.403.6 3D numerical simulation of EMAT for ferromagnetic materials.443.6.1 Establishment of numerical model.443.6.2 Numerical results and analysis.443.7 Summaries.464 Experiment research of EMAT for ferromagnetic materials .474.1 Experiment system of EMAT .474.2 Design of EMAT.484.2.1 Design of magnetic field .48西安交通大学硕士学位论文VIII4.2.2 Design of exciting coil .494.3 Experiment results of EMAT for ferromagnetic materials .494.4 Verification of numerical code of EMAT by experiment.514.5 Summaries.
