激光在楔型板激发ASF模式波的数值模拟研究
通过对模拟结果的分析得出：楔体顶角越大，沿楔尖方向传播的ASF模式楔形波的波形衰减越厉害，通频带越宽；对于周期性楔体结构，楔角越小，其对ASF楔波的频选作用越明显，而当楔角大于30°时，频选作用明显减弱。
关键词 激光超声 ASF模式楔形波 周期结构
毕业设计说明书（论文）外文摘要
Title the numerical study of ASF mode wedge waves generated by laser ultrasound technique
Abstract
Anti-symmetric flexural mode wedge waves have drawn great attention from researchers around the world due to their attractive characteristics. When Anti-symmetric flexural mode wedge waves travels along the tip of a perfect wedge, their energy is tightly confined around the apex with the absence of dispersion, low phase velocity. In this study, a theoretical model of ASF mode wedge waves was created and analyzed by using the finite element method. On this basis, the waveform of ASF mode wedge waves with different wedge angles and spectral characteristics of ASF mode wedge waves in the periodic structure were discussed.
Through the analysis of the simulation results, we can find: with the increase of angle, the waveform attenuation of ASF mode wedge waves become stronger and the passband width; as for periodic structure, when the wedge angle is under 30 degree, the frequency-selective effect is obviously, but when the angle becomes more than 30 degree, the effect stars weaken.
Keywords Laser ultrasonics ASF mode wedge wave periodic structure
目 次
1. 绪论 1
1.1 研究背景和意义 1
1.2 国内外研究进展 2
1.2.1 激光超声研究进展 2
1.2.2 ASF模式楔波的国内外研究进展 3
1.3 本文主要工作 4
2 激光激发ASF模式楔形波的基本理论 5
2.1 激光超声的激发机理 5
2.2 线性热弹性方程 6
2.3 ASF模式楔波的基本理论 8
2.3.1 薄板近似理论 9
2.3.2 几何声学理论 11
2.4 周期性结构基本特征 14
2.4.1 声子晶体 14
2.5 本章小结 15
3 激光在单一铝楔体中激发ASF模式楔波的数值模拟研究 16
3.1 有限元模型 16
3.1.1 激光作用的等效力函数 16
3.1.2 网格大小与时间步长选取 17
3.2 模拟结果及分析 18
3.2.1 楔角对ASF模式楔形波模态数的影响 18
3.2.2 楔角对ASF模式楔形波衰减特性的影响 19
3.2.3 楔角对ASF模式楔波的频带影响 20
3.3 本章小结 22
4 激光在周期性结构中激发ASF楔波的数值模拟研究 23
4.1 周期结构模型及基本物理参数 23
4.2 模拟结果及分析 24
4.2.1 小角度周期结构楔体对ASF楔波的频带影响 24