板状材料中脉冲激光激发超声导波的数值分析  

Numerical Aanalysis of Ultrasonic Guided Waves Generated by Pulsed Laser in Plate

作　　者：关建飞[1] 沈中华[1] 许伯强[1] 陆建[1] 倪晓武[1] 

机构地区：[1]南京理工大学信息物理与工程系,江苏南京210094

出　　处：《光电子．激光》2005年第2期231-235,239,共6页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金资助项目(60208004);江苏省自然科学基金资助项目(BK2001056);教育部高校优秀青年教师奖励计划基金资助项目

摘　　要：利用有限元法(FEM)对板状金属材料中脉冲激光激发的超声导波进行了理论研究。在考虑热弹激发的条件下,利用三维轴对称的有限元模型,计算了相同能量的分别具有不同聚焦半径以及脉冲宽度的脉冲激光光源直接作用于Al板表面激发出的声表面波信号的时域特征,并利用Wigner Ville分布的时频分析工具得到了信号能量在频域上的分布特征。研究结果表明,激光单脉冲能量不变的情况下,超声导波信号的峰值幅度随着脉冲激光的聚焦半径的减小而逐渐增大;同时缩小聚焦半径也可以提高超声导波的频带宽度;然而脉冲宽度的变化却没有引起超声信号在时域及频域特征上的明显变化。A theoretical study on ultrasonic guide waves generated by a pulsed laser was presented,using the finite element method(FEM).Taking only the thermoelastic excitation into the consideration,and with the three dimensional axis-symmetric model,we got the temporal characteristics of the ultrasonic guided waves generated by the pulsed laser with the different beam radius and the various rising time.Furthermore we introduced the Wigner-Ville theory to analysis the distribution of the energy of the SAW in the frequency domain.The results show that the maximum amplitude of the guide wave becomes larger and larger as the beam radius of the pulsed laser decreases;In addition decreasing the beam radius can also enhance the frequency bandwidth of the guide wave;nevertheless,the varied pulse-width has no obviously influence on the temporal and frequency domain features,which are very important in the improving the generation efficiency of the ultrashort pulsed laser ultrasonics.

关 键 词：脉冲激光 光激 信号 聚焦 脉冲宽度 WIGNER-VILLE分布 单脉冲 超声导波 能量 焦半径 

分 类 号：TN4[电子电信—微电子学与固体电子学] TN911