罐底腐蚀声发射传播仿真研究

发布时间：2018-05-22 13:34

本文选题：波动理论 + 声发射传播　；参考：《沈阳工业大学》2016年硕士论文

【摘要】：随着经济的发展,石油储罐的安全越来越重要。由于储存介质的特殊性,特别容易引发罐底板腐蚀而导致安全隐患。声发射检测是检测储罐底腐蚀的有效手段。本文主要通过仿真实验,对罐底板声发射信号的波形与传播特性进行了研究。本文对声发射本质与波动理论进行了归纳,确立使用波动理论解决声发射问题。针对罐底板这种复杂结构中的波动,使用有限元方法并采用COMSOL有限元软件进行仿真。对声发射激励信号进行了总结,对罐底板模型在仿真中参数选择进行了分析,使用结构力学-固体力学模块,求解采用瞬态分析方法。运用有限元仿真软件,首先对板中Lamb波进行仿真,确立仿真对象与研究重点。再对罐底板分别进行二维、三维无焊缝模型、三维有焊缝模型的仿真。选取不同采样点的应力、位移分量,应用分段滤波与小波时频图方法进行分析。通过上述理论与仿真研究表明,在频谱段上,声发射在低频信号能量最大,但包含信息较少,在100kHz为激励的信号中,20-80kHz信号最为丰富,能量较100kHz以上信号大,信息量较多。50kHz左右信号在波形与小波时频图上也与实际采集的声发射信号最为吻合,说明采集中主要采集的就是声发射50kHz左右信号。在激励信号上,二维仿真中使用阶跃信号产生了多道脉冲,与Lamb实验相似,在三维仿真中,则使用脉冲信号,信号随时间衰减。在方向上,在底板固定的情况下,法线方向能量强度最高,最适合声发射采集。同时,底板中焊缝对声发射信号传播影响也很大。
[Abstract]:With the development of economy, the safety of oil storage tanks is becoming more and more important. Because of the particularity of storage medium, it is easy to cause tank floor corrosion and lead to hidden danger of safety. Acoustic emission detection is an effective method to detect tank bottom corrosion. In this paper, the waveform and propagation characteristics of acoustic emission signals from tank floor are studied by simulation experiments. In this paper, the essence of acoustic emission and wave theory are summarized, and the wave theory is used to solve the acoustic emission problem. The finite element method (FEM) and COMSOL finite element software are used to simulate the wave in the complex structure of tank floor. The acoustic emission excitation signal is summarized and the parameter selection of the bottom plate model of the tank is analyzed in the simulation. The structural mechanics solid mechanics module is used to solve the problem and the transient analysis method is used to solve the problem. In this paper, the finite element simulation software is used to simulate the Lamb wave in the plate, and the simulation object and research emphasis are established. Then the tank bottom plate is simulated by two-dimensional, three-dimensional weld-free model and three-dimensional weld model. The stress and displacement components of different sampling points are selected and analyzed by using piecewise filtering and wavelet time-frequency image method. The theoretical and simulation results show that in the frequency spectrum, acoustic emission has the largest energy in the low frequency signal, but contains less information. Among the signals excited by 100kHz, the 20-80kHz signal is the most abundant, and the energy is larger than that of the 100kHz signal. The more information about .50kHz signal is the most consistent with the actual acoustic emission signal on the waveform and wavelet time-frequency diagram, which shows that the main acquisition is the acoustic emission 50kHz signal. In the excitation signal, the step signal is used to generate multi-channel pulse in two-dimensional simulation, which is similar to the Lamb experiment. In three-dimensional simulation, the pulse signal is used, and the signal attenuates with time. In the direction, the normal direction energy intensity is the highest when the bottom plate is fixed, so it is most suitable for acoustic emission acquisition. At the same time, the weld in the bottom plate also has a great influence on the acoustic emission signal propagation.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TE988

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