压电超声导波在层状管道结构中传播特性研究

发布时间：2018-03-15 21:11

本文选题：结构健康监测　切入点：PZT　出处：《沈阳建筑大学》2015年硕士论文　论文类型：学位论文

【摘要】：19世纪中叶,管道运输业开始兴起。由于对油气资源的大量开发和市场对能源需求的急剧增加,使之成为与公路、铁路、航空、水运并驾齐驱的五大运输业之一,在经济建设和国防工业中发挥重要作用。在实际工程中,为了保护管道结构,通常在管道外部设置一定厚度的保温和保护层,直接放置在地下或水底。然而随着使用时间的增加,带有保温和保护层的管道也会出现损伤,除了影响正常的生产、造成资源浪费、经济损失外,甚至还会给人们的生命财产安全造成巨大损失。由此可见对于层状管道结构的损伤检测是十分必要的。由于常规检测方法的局限性,一种新的无损检测方法—利用压电陶瓷的超声导波检测方法逐渐被关注并发展。其中,对于管道结构中超声导波频散曲线特性分析以及其传播规律的研究是这个领域最关键的科学问题,亟需通过系统的研究加以解决。本文主要通过理论分析、试验验证和数值分析相结合的方法,分别对单层钢管和层状管道中超声导波频散曲线特性进行研究,主要研究内容包括：首先,借助前人的研究成果推导出对空心圆管和空心层状管道结构中的超声导波的频散方程,进而利用Matlab软件对导波的频散方程进行求解,绘制出制定材料与几何参数的两种管道结构的群速度和相速度频散曲线；对两种管道结构中导波的三种模态：T模态、F模态、L模态进行模态分析,发现T模态与F模态频散曲线变化复杂、频散大不适合作为激励信号,并同时分析了两种管道结构中L(0,2)模态的频散曲线,为管道结构超声导波检测中激励信号的选择提供了理论依据。其次,进行了两种无损管道结构的验证性试验。在试验之前,通过对激励信号的分析发现,经Hanning窗调制的正弦叠加信号适合作为检测的激励信号。利用压电陶瓷片作为信号的激发与接收装置,分别激励L(0,2)模态和L(0,1)模态的导波信号,分别对单层无损钢管和层状无损管道进行检测。对根据实验数据绘制频散曲线,将试验频散曲线与理论分析结果进行比较,两者基本吻合,从而证明了频散曲线绘制方法的正确性。最后,对单层管道中超声导波频散曲线特性进行了研究。以单层管道中超声导波频散曲线的L(0,2)模态作为分析模态,分别从单一管材(单层钢管)和多种管材两个方面进行大量的分析研究,拟合出单层钢管特征频率和弱频散区域的经验公式,给出了单层钢管超声导波检测技术中激励信号的选取原则；并发现不同材料的单层管道中超声导波频散曲线的特征频率与其弹性模量和密度的比值关系较大,随着该比值的增大,特征频率也在不断增大。
[Abstract]:In the middle of 19th century, pipeline transportation began to rise. As a result of the massive exploitation of oil and gas resources and the sharp increase in the market demand for energy, it became one of the five transportation industries that kept pace with roads, railways, aviation and water transportation. It plays an important role in economic construction and national defense industry. In practical projects, in order to protect the pipeline structure, a certain thickness of insulation and protective layer is usually placed outside the pipeline. Directly placed underground or underwater. However, with the increase of service time, pipes with thermal insulation and protective layer will also be damaged, in addition to affecting normal production, resulting in waste of resources, economic losses, It can even cause great loss of life and property safety. It can be seen that the damage detection of layered pipeline structure is very necessary. Due to the limitations of conventional detection methods, A new nondestructive testing method, ultrasonic guided wave detection method using piezoelectric ceramics, has been paid more and more attention. The characteristic analysis of ultrasonic guided wave dispersion curve and the study of its propagation law in pipeline structure are the most key scientific problems in this field, which need to be solved by systematic research. The characteristics of ultrasonic guided wave dispersion curves in single-layer steel pipe and layered pipe are studied by the combination of experimental verification and numerical analysis. The main research contents are as follows: first of all, The dispersion equations of ultrasonic guided waves in hollow circular pipes and hollow layered pipes are derived by previous research results, and the dispersion equations of guided waves are solved by using Matlab software. The dispersion curves of group velocities and phase velocities of two kinds of pipeline structures with material and geometric parameters are plotted, and three modes of guided waves in two kinds of pipeline structures are analyzed, such as: t mode / F mode / L mode. It is found that the dispersion curves of T mode and F mode are complex, and the frequency dispersion is not suitable for the excitation signal. The dispersion curves of the L0 / 2) modes in the two kinds of pipeline structures are also analyzed at the same time. It provides a theoretical basis for the selection of excitation signals in ultrasonic guided wave detection of pipeline structures. Secondly, two kinds of validation tests of non-destructive pipeline structures are carried out. The sinusoidal superposition signal modulated by Hanning window is suitable to be used as the excitation signal for detection. The guided wave signals of the L0 / 2) mode and the L0 / 1) mode are excited by using the piezoelectric ceramic chip as the excitation and receiving device of the signal, respectively. The dispersion curves are drawn according to the experimental data, and the experimental dispersion curves are compared with the theoretical analysis results. Finally, the characteristics of ultrasonic guided wave dispersion curve in single-layer pipeline are studied. The L0 / 2 mode of ultrasonic guided wave dispersion curve in single-layer pipeline is taken as the analytical mode. A great deal of analysis and research are carried out from two aspects of single pipe (single layer steel pipe) and many kinds of pipes respectively, and the empirical formulas of characteristic frequency and weak dispersion region of single layer steel pipe are fitted out. The principle of selecting excitation signal in ultrasonic guided wave detection technology of single-layer steel tube is given, and it is found that the characteristic frequency of ultrasonic guided wave dispersion curve in single-layer pipe with different materials is closely related to the ratio of elastic modulus and density. With the increase of the ratio, the characteristic frequency is increasing.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE973

【相似文献】