发布时间 : 星期四 文章超声Lamb波的激励及频率调谐 - 图文更新完毕开始阅读
二、完成后应交的作业（包括各种说明书、图纸等） 1. 毕业设计论文一份（不少于1.5万字）； 2. 外文译文一篇（不少于5000英文单词）； 3. 相关数据处理图像及Matlab数值计算程序。 二、 完成日期及进度 2010年2月27日至2010年6月5日，共12周。 进度安排： (1) 2月27日-3月5日，查阅资料、调研，完成开题报告； (2) 3月6日-4月10日，完成理论推导及Matlab数值计算； (3) 4月11日-5月10日，完成实验部分及撰写部分毕业论文； (4) 5月11日-5月20日，数据处理及完成毕业论文初稿； (5) 5月21日-6月14日，论文修改及答辩PPT制作； (6) 6月15日，毕业答辩。 iii
四、主要参考资料（包括书刊名称、出版年月等）: [1] Z. Q. Su, L. Ye, Y. Lu. Guided Lamb waves for identification of damage in composite structures: A review[J]. Journal of Sound and Vibration. 2006, 295: 753-780. [2] M. Rguiti, S. Grondel, F. E. youbi, et al. Optimized piezoelectric sensor for a specific application: Detection of Lamb waves[J]. Sensors and Actuators A. 2006, 126: 362-368. [3] 李家伟, 陈积懋. 无损检测手册[M]. 机械工业出版社. 2002年: 206-214. [4] D. Leduc, B. Morvan, A. C. Hladky, et al. Interaction of Lamb waves with a grating composed of two spatial periodicities: Study in dual space[J]. NDT&E International. 2009, 42:513-517. [5] 孙亚杰, 袁慎芳, 邱雷, 等. 基于Lamb波相控阵和图像增强方法的损伤监测[J]. 航空学报. 2009, 30(7): 1325-1330. [6] H. S. Yoon, R. DeCicco. Lamb wave excitation and detection with smart fasteners for structural health monitoring[J]. Proc. SPIE. 2010, 7649(14): 2412-2422. [7] J. S. Leng, A. Asundi. Structural health monitoring of smart composite materials by using EFPI and FBG sensors[J]. Sensors and Actuators A: Physical. 2003, 103(3): 330-340. [8] 王强, 袁慎芳. 无参考主动Lamb波结构损伤时反成像监测方法[J]. 航空学报. 2010, 31(1): 178-183. [9] 张海燕, 他得安, 刘镇清, 著. 层状各向异性复合板中的兰姆波[M]. 科学出版社. 2008年: 138-156. [10] 王珅, 黄松岭, 赵伟. 平板和管道周向Lamb波频散和波结构特性[J]. 清华大学学报(自然科学版). 2009, 49(7): 925-928. 系(教研室)主任： （签章） 年 月 日 学院主管领导： （签章） 年 月 日 iv
江苏科技大学本科毕业设计（论文）
摘 要
基于Lamb波的材料损伤检测和结构健康监测在航空工业、船舶制造、土木工程和智能材料等领域得到了广泛的研究和应用。本课题在研究超声Lamb波波动理论的基础上分析板中Lamb波的传播特性，并求出自由板中Lamb波频散方程的数值解。利用Gaussian函数、Hamming窗和Hanning窗对正弦信号进行调制，然后采用调制后的脉冲猝发信号对粘结在铝薄板表面的正方形PZT压电晶片进行激励，从而在铝薄板中产生并采集Lamb波。重点研究了各向同性铝薄板中Lamb波的传播特性、频散特性、模式识别、模式选择和频率调谐。对时域信号的分析结果表明，激励频率在10~200kHz范围内能在板内得到明显的Lamb波信号，120~150kHz时发生谐振，采集的信号最强；对信号进行频域分析时发现，各种激励波形产生的Lamb波信号都发生了频散现象，其中采用正弦单周期信号激励时板中Lamb波的频散现象最严重，而采用Hamming窗调制的五步波脉冲信号激励时频散最小，适合作为激励信号；实验测试了各种频率下A0和S0模式Lamb波的群速度并与理论值相比较，发现实验结果与数值解接近。实验还研究了采用不同波形激励时不同模式（A0和S0）Lamb波的强度随频率的变化关系，结果发现在20~60kHz和100~150kHz两区间内，A0和S0模式Lamb波的强度有明显差异。因此，可以通过选择适当的激励频率来获得模式单一性好、强度高、对某类缺陷敏感的Lamb波。
关键词：超声兰姆波；激励与接收；频散特性；模式识别与选择；各向同性铝薄板
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江苏科技大学本科毕业设计（论文）
Abstract
Material damage detection and structural health monitoring based on Lamb wave are widely studied and applied in the areas of aerospace industry, ship manufacturing, civil engineering and smart material. In this research, the propagation characteristics of Lamb wave were analyzed by the study of the wave theorem of Lamb wave in plate, and the numerical solutions of dispersion equation of Lamb wave in free plate were also calculated. Excitation signals in a variety of waveforms were obtained via modulating the sinusoidal waveform by Gaussian function, Hamming window and Hanning window. Then Lamb wave was actuated and collected in the thin aluminium plate by square PZT crystal wafer which bonded on the thin aluminium plate. The major emphasis is placed on the propagation characteristics, dispersion characteristics, mode identification, mode selection and frequency tuning of Lamb wave in the thin isotropic aluminium plate. The time-domain analysis shows that apparent Lamb wave signals were detected when the excitation frequency ranges from 10kHz to 200kHz, in which, the most intensive signal was detected under a frequency about 120~150kHz due to the harmonic oscillation; The frequency-domain analysis indicates that dispersion phenomenon of Lamb wave exists under any conditions of the excitation signal, in which, the Lamb wave excited by a single-cycle sinusoidal burst pulse shows a serious frequency dispersion, while the Lamb wave excited by a Hamming window modulated five-step waveform burst pulse shows the lowest frequency dispersion. Therefore, the later is the most workable excitation signal. The group velocity of both A0 and S0 modes were measured, which are closed to the theoretical results. The relationship between frequency and signal intensity of both A0 and S0 modes under different conditions of excitation waveforms were studied experimentally to find the intensity of A0 and S0 modes show an apparent difference when the excitation frequency band fall in the ranges of 20~60kHz and 100~150kHz. Accordingly, we can obtain a Lamb wave with good unity, high intensity and sensitive for certain defect types by selecting appropriate excitation frequency.
Keyword：Ultrasonic Lamb Wave; Excitation and Collection; Dispersion Characteristics;
Mode Identification and Selection; Isotropic Thin Aluminium Plate
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