论文部分内容阅读
激光激发声表面波提供了评价涂层或薄膜的弹性性质的有效手段。考虑激光作用过程中材料热物理参数随温度变化的实际情况,在研究网格大小和时间步长这二个重要参数和求解稳定性的基础上,建立了优化的有限元模型数值模拟两种典型涂层基底系统中声表面波的激光热弹激发和传播过程。数值模拟结果表明:除了掠面纵波外,在快基底慢涂层系统中得到了正常的色散表面波,而在慢基底快涂层系统中得到了反常色散表面波。进一步,采取减小激发激光光斑的办法,使激发出来的声表面波频率高于慢基底快涂层系统中的截止频率时,在慢基底快涂层系统中得到了伪表面波。
Laser-induced surface acoustic waves provide an effective means of evaluating the elastic properties of coatings or films. Considering the fact that the physical parameters of the material change with temperature during the laser process, two important parameters of the grid size and time step are studied and the stability of the solution is solved. Two typical numerical simulations of the finite element model are established Laser thermo-elastic excitation and propagation of SAW in a coated substrate system. The numerical simulation results show that, in addition to the longitudinal wave of the swept surface, the normal dispersion surface wave is obtained in the fast substrate slow coating system, while the anomalous dispersion surface wave is obtained in the slow base rapid coating system. Further, by reducing the excitation laser spot, when the excited surface acoustic wave frequency is higher than the cutoff frequency in the slow base rapid coating system, a pseudo-surface wave is obtained in the slow base rapid coating system.