Studying the propagating properties of surface acoustic wave traveling in functional gradient materials by laser ultrasonic
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摘要: 利用有限元的方法建立了脉冲激光在功能材料中激发声表面波的理论模型,根据该理论模型分别分析了脉冲激光在不同空间调制下所激发的声表面波(SAWs)在功能梯度材料表面的传播特性,以及不同力学参量变化对所激发的声表面波传播特性的影响。模拟结果表明:线源激发的宽带声表面波在功能梯度材料表面传播时,声表面波会出现明显的色散效应;当使用光栅调制的脉冲激光在功能梯度材料上激发声表面波时,与均匀材料中所激发的声信号相比,激发频率发生相应的频移现象。该模型为功能梯度材料的非接触表征提供了理论基础。Abstract: A theoretical model which is used to describe the propagating properties of surface acoustic wave(SAW) excited by a pulse laser in functional gradient materials(FGMs) has been proposed by means of the finite element method(FEM).In the theoretical model,the pump laser is focused as the linear and grating source to excite SAWs in the surface of FGMs,the traveling properties of SAWs caused by gradual variation of physical parameters of FGMs have been analyzed.The numerical results of theoretical models indicate that the wide-band SAW induced by a line-source laser will obviously disperse when traveling in FGMs;while the frequency of the single-frequency SAW generated by a laser induced thermal grating method will shift accordingly due to the gradual change of different parameters of material. The numerical results provide a theoretical basis for non-contact characterization of FGMs.
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