1、摘 要I硕士学位论文电磁超声无损检测的数值模拟方法及在TBC 检测上的应用研究申请人：学科专业：力学指导教师： 教授年 月西安交通大学硕士学位论文论文题目：电磁超声无损检测数值模拟方法及在 TBC 检测上的应用研究学科专业：力学申 请 人 ：指导教师： 教授摘 要电磁超声（EMA：Electromagnetic Acoustic）与传统压电超声同属于超声范畴。与传统的压电超声相比，电磁超声无损检测技术由于无需媒介及与被测物体接触，具有可灵活产生各类波形，对检测工件表面质量要求不高和检测速度快等特点，不但可提高检测效率，而且可将超声无损检测技术的应用扩展到高温、高速和在线检测。然而由于电磁超声检
2、测技术本身的复杂性，对其研究还有待进一步深入，限制了其进一步大范围应用。目前，对电磁超声的研究主要是采用试验研究和数值模拟的方法，而通过数值模拟技术，不仅可以更好的理解电磁超声产生的机理及其特性，更易发现新问题，为探头的优化设计和缺陷的定量分析提供指导，还能为相关新技术应用的可行性研究提供理论依据。本论文主要通过数值模拟的方法对电磁超声检测技术进行研究，并将电磁超声技术扩展到热障涂层（TBC）的无损检测中。主要内容是基于电磁场理论和波动方程，建立了一套电磁超声无损检测数值模拟计算方法，并开发相应的数值模拟程序；在此基础上，建立了一种基于电磁超声技术的热障涂层系统局部界面裂纹的无损检测方法，并用
3、所开发的数值模拟程序初步验证了该方法的有效性。具体包括：（1）建立了基于有限元理论的超声波数值模拟方法，同时为了降低计算过程中的计算量和存储量，提出了一种针对超声波有限元数值模拟的时域显式积分算法。通过理论分析和实际算例，证实了本文所提出的显式积分算法与传统有限元超声波数值模拟时域积分算法相比不但具有较高的计算精度，还能大幅度降低超声波数值模拟中所需的计算机资源。基于以上数值模拟方法和算法，利用 Fortran 语言自主开发了超声波检测二维和三维数值模拟程序，并通过理论分析和实验初步验证了程序的可靠性。（2）推导了基于等效磁荷法永磁体磁场分布计算公式，根据公式分别计算了两种常见永磁体的磁场分布
4、，并通过与已有结果进行比较，验证了该方法的可靠性和实用性。（3）结合前面的工作和已有的 Ar 法瞬态涡流场计算程序，建立了基于有限元理论的电磁超声无损检测数值模拟方法，利用 Fortran 语言开发了相应的数值模拟程序，并通过理论分析，对该数值模拟方法和程序的可靠性进行了初步验证。（4）将电磁超声无损检测技术应用到 TBC 热障涂层的检测，提出了一种针对热摘 要III障涂层界面微裂纹的电磁超声无损检测方法，并通过数值模拟初步证明了该方法可以提供一种检测 1 mm 以上 TBC 界面微裂纹的手段。对于实际的热障涂层中的微小界面裂纹检测，这种基于电磁超声技术的无损检测方法具有很好的研究和应用前景。
5、关 键 词：电磁超声；无损检测；热障涂层；有限元法；数值模拟论文类型：应用基础西安交通大学硕士学位论文IVTitle: Studies of the Numerical Simulation Method for EMAT and Applications to Nondestructive Inspection of TBCSpeciality: MechanicsApplicant: Cuixiang PeiSupervisor: Prof. Zhenmao ChenABSTRACTBoth electromagnetic acoustic testing (EMAT) and tradi
6、tional piezoelectric ultrasonic testing belong to the category of ultrasonic nondestructive testing technology. As no physical contact is necessary between transducer and test-piece, various wave patterns can be generated, surface quality demand of the test-piece is not high, and detection speed is
7、fast, the EMAT 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 complicity of EMAT technique itself, there are still several problems for its continuous development.
8、 At present, the studies on the EMAT are mainly by means of experimental research and numerical simulation method. The numerical simulation technique can not only help to have a better understand on the producing mechanism and properties of the EMA, find some new problems more easily, provide a usef
9、ul tool for the transducers optimization design the defects sizing analysis, but also provide theoretical basis for the feasibility study of the application of associated new techniques.The studies on the EMAT technique were mainly by means of numerical simulation method, and the application of EMAT
10、 was extended to the detection of thermal barrier coatings (TBC) in this thesis. A finite element method (FEM) for the numerical simulation of EMAT signals was established and the corresponding numerical code was developed independently. Finally, as an application, the feasibility of a newly propose
11、d EMAT type transducer is evaluated by using the new code for detecting macro delaminating defect in TBC. The main research works are presented as follows:1) A finite element method for numerical simulation of ultrasonic testing signal is established. Meanwhile, To improve the neck point of FEM for
12、UT simulation, i.e., the great computational burden, a new explicit integration algorithm of time domain is introduced, which can reduce the data operand and memory consumpsion significantly. Through theoretical analysis and numerical calculation, it can be found that the new explicit integration al
13、gorithm has a high precision and can satisfy the engineering calculation needs. At last, a 2-dimentional and a 3-dimentional code for the simulation of ultrasonic testing ABSTRACTVwere developed based on the proposed numerical method and integration scheme, and the feasibility of the numerical metho
14、d and developed codes was verified by comparing the calculation results with the theoretical and experimental ones. 2) The calculation formulas for the magnetic field distribution of permanent magnets was deduced based on the equivalent magnetic charge approach. According to the formulas, the magnet
15、ic field distribution of two typical magnets was calculated, By comparing to the previous known results, the validity of the formulas was verified.3) A finite element method for numerical simulation of EMAT was established based on the works above and using an ECT code of Ar method, and the correspo
16、nding codes were developed with FORTRAN language. The feasibility of the simulation method and developed numerical codes was verified by comparing the calculation results with theoretical results.4) To extend the application of EMAT to the detection of TBC, a new transducer of EMAT for detecting mac
17、ro delamination defect in TBC is proposed and evaluated with the developed numerical code. It was preliminarily conformed that the new method can be used to detect a delamination defect as small as 1 mm long in TBC. It reveals that this EMAT based method for TBC inspection has a broad prospect of fu
18、rther research and application.KEY WORDS: Electromagnetic Acoustic Testing; Nondestructive Evaluation; Thermal Barrier Coatings; FEM; Numerical Simulation MethodTYPE OF THESIS: Application Fundamentals*This study is supported by National 973 Projects (No.2006CB601206, 2007CB707702), National Natural
19、 Science Fundation of China (No.50677049) and Ministry of Education New Century Talent Project.西安交通大学硕士学位论文VI目 录1 绪论 .11.1 背景 .11.1.1 无损检测方法概述 .11.1.2 超声波无损检测技术概述 .11.1.3 电磁超声无损检测技术概述 .21.1.4 热障涂层（TBC）系统简介及其失效形式 .41.2 电磁超声在国内外的发展 .51.3 热障涂层的检测及其研究现状 .51.4 本论文研究目标 .61.5 本论文主要内容 .62 电磁超声无损检测的基本理论方法 .7
20、2.1 超声波的基本理论 .72.1.1 超声波简介 .72.1.2 超声波的波形 .72.2 电磁超声无损检测原理 .92.3 涡流场计算中的棱边有限元和 Ar 方法 .92.3.1 基本微分控制方程 .102.3.2 基于 Ar 方法的棱边元控制方程 .112.4 本章小结 .163 各向同性介质超声波的数值模拟 .173.1 基于有限差分的超声波数值模拟 .173.1.1 基本微分控制方程 .173.1.2 建立控制方程的离散差分形式 .183.1.3 基于有限差分的超声波检测的数值模拟及验证 .213.2 超声波的有限元数值模拟方法 .223.2.1 二维超声波的有限元数值模拟方法 .
21、223.2.2 三维超声波的有限元数值模拟方法 .283.3 一种新的基于有限元的超声波数值模拟时域积分算法 .323.3.1 传统隐式积分算法 .323.3.2 传统显式积分算法 .333.3.3 一种新的显式积分算法 .34目 录绪论VII3.3.4 几种时域积分算法的计算精度实例比较 .363.4 超声波无损检测有限元数值模拟实例及验证 .373.4.1 超声无损检测二维有限元数值模拟 .373.4.2 超声波的三维有限元数值模拟及实验验证 .453.5 本章小结 .474 电磁超声的数值模拟 .484.1 基于等效磁荷法的静态磁场的计算 .484.1.1 等效磁荷法的建立 .484.1
22、.2 矩形永磁体的磁场计算 .494.1.3 U 型永磁体的磁场计算 .514.1.4 永磁体的磁场计算实例及验证 .534.2 脉冲涡流场和洛仑兹力的计算 .544.2.1 迭代公式的建立 .544.2.2 数值模拟实例 .554.3 洛仑兹力作用下电磁超声的数值模拟 .574.3.1 电磁超声数值模拟计算公式的建立 .574.3.2 电磁超声数值模拟程序的开发 .584.3.3 电磁超声数值模拟计算实例及验证 .594.4 本章小结 .615 电磁超声技术在 TBC 检测上的应用 .625.1 TBC 电磁超声检测初步方案及原理 .625.2 TBC 电磁超声检测数值模拟应用实例 .635
23、.2.1 数值计算模型的建立 .635.2.2 数值模拟结果 .645.3 TBC 电磁超声检测的进一步研究 .665.4 小结 .696 总结与展望 .706.1 主要工作和结论 .706.2 研究工作展望 .71参考文献 .72致 谢 .74攻读学位期间取得的研究成果 .75声明西安交通大学硕士学位论文VIIICONTENTS1 Introduction .11.1 Background .11.1.1 Introduction of NDT Technology.11.1.2 Introduction of UT Technology .11.1.3 Introduction of EM
24、AT Technique.21.1.4 Introduction of TBC System and the Coating Failure.41.2 Development of EMAT in Worldwide.51.3 Research Status of TBC Inspection.51.4 Objectives.61.5 Main Works .62 Basic Theories and Methods of EMAT.72.1 Basic Theories of Ultrasonic Waves .72.1.1 Introduction of Ultrasonic Waves
25、.72.1.2 Waveforms of Ultrasonic Waves .72.2 Basic Principles of EMAT .92.3 FEM and Ar Method in Numerical Simulation of Eddy Current.92.3.1 Basic Governing Equations .102.3.2 Establishing FEM Equations Based on Ar Method.112.4 Summary .163 Numerical Simulation of UT.173.1 Numerical Simulation for UT based on FDM.173.1.1 Basic Differential Control Equations .173.1.2 Discrete Control Equations of FDM .
