变厚度板超声导波检测理论与技术

发布时间：2018-05-13 06:49

本文选题：超声导波 + 变厚度板　；参考：《北京理工大学》2014年博士论文

【摘要】：变厚度板以其强度高质量轻环境适应能力强，能在满足结构安全和力学性能要求的前提下，降低结构质量和成本，被广泛应用于航空航天船舶汽车等工业生产和生活领域但由于受到制造和使用中的外部载荷和外部复杂环境作用产生的腐蚀性凹坑和裂纹等缺陷的破坏，使变厚度板的结构完整性遭到严重破坏，甚至产生机体断裂等安全事故，对产品的使用安全造成严重威胁由于超声导波对板ξ尤其是薄板中缺陷比较敏感，被认为是变厚度板缺陷检测最有发展潜力的检测技术手段然而，由于对厚度变化造成的导波传播规律异常复杂现象尚未展开深入的研究，因此，导致目前在超声导波与缺陷的相互作用机理分析方面存在较大困难本文以变厚度板中的裂纹缺陷为超声导波量化检测对象，以超声导波为主要技术手段，通过对变厚度板中的导波传播规律进行深入研究，提出了相关的量化检测方法主要思路为总体上针对变厚度板特点，采用不同类型导波分别对斜面板频厚积小于2.3MHz-mm薄端部分和频厚积大于2.3MHz-mm厚端部分进行检测，完成斜面板缺陷的检测和量化具体实施过程中采用位移势函数法结合边界条件，求解以弹性理论为基础建立的变厚度板平面应变波动方程，得到了具有多模式和频散特性的导波频散方程和频散曲线，在此前提下，以有限元仿真技术为研究手段，分析了不同激励条件下的变厚度板中导波传播特性以及缺陷对导波的影响基于表面波传播理论，以有限元仿真技术为手段，分析了表面波在变厚度板厚度大于3倍表面波波长区域的传播特性以及缺陷对表面波的影响综合应用时频域分析方法的对导波模式成分和模式转换情况进行研究，在获取能表征缺陷大小特征参数的基础上实现对缺陷检测的目标基于换能器阵列技术搭建多通道换能器阵列检测系统实现对缺陷形位的综合检测，并通过实验验证了该系统的检测效果具体研究内容概括如下（1）第2章，以平板Lamb理论模型及传播特性为指导，基于波动动力学有限元基本原理，通过对二维波动方程的有限元建模过程和结果的分析，提出了平面薄板的有限元模型参数和边界设置方法，为后续研究奠定技术和理论基础在获取和分析导波频散特性和模态的基础上，通过对相关有限元参数的选择建模和求解，分析了不同激励方式下的导波模态以及缺陷对导波的影响，通过实验方法验证了所建模型的正确性（2）第3章，基于平面应变理论建立了变厚度板导波传播的数学模型，采用位移势函数法结合边界条件求解波动方程获取了变厚度板的频散方程和频散曲线通过对不同部位不同激励方式下的导波模式以及声速衰减分析，获取了变厚度板中导波的传播规律角度和激励频率及缺陷对导波的影响，最后通过实验方式验证了所建立模型的正确性（3）第4章，通过分析表面波基本理论和传播规律，分析了斜面板表面波的传播规律和角度对表面波的影响，在分析表面波与缺陷相互作用的基础上，建立了缺陷对声表面波的作用模型（4）第5章，基于时频域分析方法，对超声导波的模式和模式转换规律情况进行分析，提出了基于激励S0模式接收A0模式导波的缺陷识别及特征参数提取方法针对表面波信号则提出了基于横波反射信号的缺陷识别及特征参数提取方法，通过人工缺陷的检测实验结果表明所提出的方法与理论吻合度较好（5）第6章，基于缺陷形位检测的需求，结合单换能器声场特性和椭圆定位原理，，搭建了多通道阵列超声检测系统，并开展了平板和变厚度板缺陷的检测实验工作，结果表明该系统能够有效识别缺陷的位置和几何形态
[Abstract]:The variable - thickness plate has strong adaptability to the high - quality light environment with high strength , can reduce the structural quality and cost under the premise of meeting the requirements of structural safety and mechanical property , and is widely applied to the fields of industrial production and life such as aerospace ship automobiles and the like .

Based on the theory of finite element simulation , this paper analyzes the propagation characteristics of the surface wave in the variable thickness plate and the influence of the defect on the surface wave . The method is based on the theory of finite element simulation . The method is used to construct the multi - channel transducer array detection system based on the elastic theory . The method is used to construct the multi - channel transducer array detection system based on the transducer array technology .

( 1 ) In chapter 2 , the finite element model parameters and boundary setting method of planar thin plate are presented based on the theory of plate Lamb theory and propagation characteristics . Based on the analysis of the finite element modeling process and the results of the two - dimensional wave equation , the influence of the guided modes and the defects on the guided wave in different excitation modes is analyzed by selecting and solving the relevant finite element parameters . The correctness of the model is verified by the experimental method .

( 2 ) In chapter 3 , based on plane strain theory , a mathematical model of variable thickness plate guided wave propagation is established . The dispersion equation and dispersion curve of variable thickness plate are obtained by using displacement potential function method in combination with boundary conditions . The influence of propagation law angle and excitation frequency and defect on guided wave in variable thickness plate are obtained . Finally , the correctness of the model is verified experimentally .

( 3 ) In chapter 4 , by analyzing the basic theory and propagation law of surface waves , the influence of the propagation law and angle of the surface wave on the surface wave is analyzed . On the basis of analyzing the interaction between the surface wave and the defect , the effect model of the defect on the surface acoustic wave is established .

( 4 ) In chapter 5 , based on the time domain analysis method , the mode and mode conversion law of ultrasonic guided wave is analyzed , and the defect recognition and characteristic parameter extraction method based on excitation S0 mode receiving A0 mode guided wave is put forward , and the defect recognition and characteristic parameter extraction method based on the transverse wave reflection signal is proposed for the surface wave signal .

( 5 ) In chapter 6 , based on the requirement of defect - shaped position detection , a multi - channel array ultrasonic detection system is built based on the sound field characteristic and the ellipse positioning principle of single transducer , and the detection experiment of the defect of flat plate and variable thickness plate is carried out , and the result shows that the system can effectively identify the position and the geometry of the defect .

【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TB553

【参考文献】