激光激发板状材料中超声导波的有限元数值模拟  

Numerical Simulation of Laser-Generated Ultrasounic by Finite Element Method in the Plate Material

作　　者：许伯强[1] 倪晓武[1] 沈中华[1] 陆建[1] 

机构地区：[1]南京理工大学信息物理与工程系

出　　处：《中国激光》2004年第5期621-625,共5页Chinese Journal of Lasers

基　　金：国家自然科学基金 (No .6 0 2 0 80 0 4 );江苏省自然科学基金;教育部高校优秀青年教师奖励计划资助项目

摘　　要：材料表面吸收激光辐照的能量后 ,产生瞬态温度场 ,引起表面层的局部热膨胀 ,产生超声波沿不同方向传播。激光超声具有非接触、宽频带、多模态的特点 ,提供了材料的弹性性质和材料无损检测的有效手段。考虑激光作用过程中材料热物理参数随温度变化的特性 ,用有限元方法数值模拟激光在板状材料中激发瞬态温度场 ,建立热弹机制下超声导波的产生和传播的有限元模型。数值模拟的结果表明 :材料中瞬态温度场分布在材料的表面层的非常小的区域 ,温升区域是产生超声的体源。分析近场和远场接收的超声导波的表面波形的传播特征 ,讨论激光输入参数和激光产生超声波特征之间的关系 。A laser pulse incident on a material generates the transient temperature field. As rapid and localized thermal expansion occurs, energy is released in the form of propagating ultrasound in all directions. Laser generated ultrasound is non contact, broadband, and multiple propagation modes. Considering the temperature dependence of material properties, the transient temperature distribution is simulated using the finite element method in the plate material; a finite element is developed to simulate the laser thermo elastic generation and propagation of laser ultrasound. The numerical results indicate that the heat affected zone is very localized, such a distribution of the transient temperature is considered as a body source in the generation of ultrasound; analyze the propagation features of surface waveforms in the near and far field; Discuss the relation between the laser input parameters and the generated ultrasonic wave characteristics; establish a quantitative basis for the thermo elastic mechanism in nondestructive evaluation of the material properties.

关 键 词：激光技术 有限元方法 温度场 超声 

分 类 号：TG665[金属学及工艺—金属切削加工及机床] O242.1[理学—计算数学]