水平剪切波的激发及与金属板中损伤相互作用

发布时间：2018-06-24 02:08

本文选题：有限元法 + d_(36)型压电单晶　；参考：《江苏大学》2017年硕士论文

【摘要】：超声导波具备传播距离远,能量损失小的优点,已成为当前结构健康监测/无损检测领域的研究焦点。薄板结构中存在Lamb波和水平剪切(Shear Horizontal:SH)波,其中Lamb波在损伤检测中已有许多应用,然而其固有的色散和多模态等特征使得接收信号的解读面临挑战。相比于Lamb波,SH波在频率低于一阶截止频率时,具有模态单一且无色散的优点。因此,SH波在无损检测中极具研究价值和应用前景。根据Navier运动方程,采用势函数法,联系边界条件求解板中导波的色散方程。根据超声导波的传播理论,并参照超声导波的探伤流程,分析SH波在损伤检测领域的特点和优势。基于压电双向耦合效应及本构方程,研究了压电材料的导波激发理论和特征,建立三维有限元数值模型模拟研究了d_(36)型压电晶片在金属板中所激发的导波场。提取和分析面内的位移场信息,对比传统的d35型压电材料,证明了d_(36)型压电材料在金属板中高效激发/传感SH波的能力。讨论了d_(36)型压电晶片在金属板中激发各模态导波的空间分布状况,为金属板中SH波的高效激发提供理论基础。基于d_(36)型压电晶片激发的SH波,建立SH波与两种不同类型损伤相互作用的有限元数值模型。针对金属板中的裂缝损伤,利用波形的变化评价SH波检测裂缝损伤的能力;针对金属板中的腐蚀损伤,以反射系数评估SH波对板中腐蚀损伤的敏感程度。本文基于数值模拟,探究了d_(36)型压电材料的激发特征,给出了高效激发SH波的方法;讨论了SH波与金属板中两类损伤的相互作用,为SH波探测特定类型损伤提供了理论依据。
[Abstract]:Ultrasonic guided waves have the advantages of long propagation distance and low energy loss, which have become the focus of research in the field of structural health monitoring and nondestructive testing. There are Lamb waves and Shear Horizontal: SH waves in thin plate structures. Lamb waves have many applications in damage detection, but their inherent dispersion and multi-mode characteristics make the interpretation of received signals difficult. Compared with Lamb wave SH wave, it has the advantages of single mode and no dispersion when the frequency is lower than the first-order cutoff frequency. Therefore, SH-wave is of great value and application prospect in nondestructive testing. According to the Navier equation of motion, the dispersion equation of guided waves in the plate is solved by using the potential function method and the boundary conditions. According to the theory of ultrasonic guided wave propagation and referring to the flaw detection flow of ultrasonic guided wave, the characteristics and advantages of SH wave in the field of damage detection are analyzed. Based on the piezoelectric bidirectional coupling effect and constitutive equation, the guided wave excitation theory and characteristics of piezoelectric materials are studied. A three-dimensional finite element numerical model is established to simulate the guided wave field excited by d _ (36) piezoelectric wafer in a metal plate. The displacement field information in plane is extracted and analyzed. Compared with the traditional d35 type piezoelectric material, the ability of d _ (36) type piezoelectric material to excite / sense SH wave efficiently in metal plate is proved. The spatial distribution of guided waves excited by d36 type piezoelectric wafers in metal plates is discussed, which provides a theoretical basis for the efficient excitation of SH waves in metal plates. Based on the SH waves excited by d36 piezoelectric wafers, a finite element numerical model for the interaction of SH waves with two different types of damage is established. Aiming at crack damage in metal plate, the ability of detecting crack damage by SH wave is evaluated by waveform change, and the sensitivity of SH wave to corrosion damage in plate is evaluated by reflection coefficient for corrosion damage in metal plate. Based on numerical simulation, the excitation characteristics of d _ (36) type piezoelectric materials are investigated, the method of highly efficient excitation of SH waves is given, and the interaction between SH waves and two kinds of damage in metal plates is discussed, which provides a theoretical basis for SH waves to detect specific types of damage.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG115.285

【参考文献】