基于超声无损检测技术的需要, 该文在理论分析声表面波混频效应的基础上, 提出了一种混频声表面波的激发方法, 并进行了相应的声表面波混频谐波的实验观察研究。设计并制作了以斜入射的体横波和体纵波分别激发声表面波的楔块, 通过选择适当的体横、纵波激励信号的周波数及时间延迟, 可使斜入射体横、纵波分别激发的声表面波完全混叠。通过对接收到的混叠声表面波时域信号进行脉冲反相处理和傅里叶变换, 得到明显的声表面波混频谐波信号。结果表明, 借助于楔块两列斜入射的体横、纵波可有效产生混频声表面波, 实验观察与理论预期一致, 这为发展基于混频声表面波的超声无损检测技术奠定了基础。

声表面波(SAW）器件广泛应用于极端环境传感, 硅酸镓镧(LGS）是常用高温压电晶体, 但高温下应变胶因结合力导致应变传递效果不佳。该文研究了高温环境下应变传感的过渡层薄膜技术, 提出了一种新的过渡层薄膜解决方案及其工艺技术, 可实现高温应变胶水传递应变更稳定的效果。结果表明, 采用溅射Al再氧化可显著提升LGS与高温胶的结合力, 从而实现很好的应变传递, 使用这种过渡层实现了500 ℃下超大量程(1 000 με）测量。

为了研究多层石墨烯对声表面波的放大作用, 分析了外加电场下石墨烯载流子的可变电导率, 研究了不同衬底下多层石墨烯声表面波放大器的放大性能。对比研究了ZnO和CdS为衬底的石墨烯声表面波放大器, 分别对其在不同载流子漂移速度下的放大倍数进行了研究。结果表明, 以ZnO为衬底, 载流子漂移速度大于且接近声表面波相速度时, 放大性能是最优的, α可以达到34.92 dB。

Within the framework of the linearized theory of electroelastic wave propagation, a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered. The ferroelectric LiNbO₃ is used as the main material of the structure. The initial deformed state of the coating material is homogeneous, induced by the action of initial mechanical stresses and an external electrostatic field, the properties of the coating continuously change in thickness. By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface, the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied. The separate and combined effects of initial actions on changes in the physical properties of the structure, the transformation of the surface wave field, and the change in the SAW velocities in a wide frequency range is studied. The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures, in the optimization and design of new structures and devices on SAW with high performance characteristics.Within the framework of the linearized theory of electroelastic wave propagation, a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered. The ferroelectric LiNbO₃ is used as the main material of the structure. The initial deformed state of the coating material is homogeneous, induced by the action of initial mechanical stresses and an external electrostatic field, the properties of the coating continuously change in thickness. By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface, the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied. The separate and combined effects of initial actions on changes in the physical properties of the structure, the transformation of the surface wave field, and the change in the SAW velocities in a wide frequency range is studied. The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures, in the optimization and design of new structures and devices on SAW with high performance characteristics.

In the characterization of elastic properties of tissue using dynamic optical coherence elastography, shear/surface waves are propagated and tracked in order to estimate speed and Young's modulus. However, for dispersive tissues, the displacement pulse is highly damped and distorted during propagation, diminishing the effectiveness of peak tracking approaches, and leading to biased estimates of wave speed. Further, plane wave propagation is sometimes assumed, which contributes to estimation errors. Therefore, we invert a wave propagation model that incorporates propagation, decay, and distortion of pulses in a dispersive media in order to accurately estimate its elastic and viscous components. The model uses a general first-order approximation of dispersion, avoiding the use of any particular rheological model of tissue. Experiments are conducted in elastic and viscoelastic tissue-mimicking phantoms by producing a Gaussian push using acoustic radiation force excitation and measuring the wave propagation using a Fourier domain optical coherence tomography system. Results confirmed the effectiveness of the inversion method in estimating viscoelastic parameters in both the viscoelastic and elastic phantoms when compared to mechanical measurements. Finally, the viscoelastic characterization of a fresh porcine cornea was conducted. Preliminary results validate this approach when compared to other methods.

为了改善激光超声检测中声表面波的信噪比，利用对激光线源进行时间和空间上的调制获得激光阵列作为激励源辐照铝板表面，采用有限元法分别模拟了大位移幅值声表面波(巨声表面波)的激发以及巨声表面波与铝板表面矩形缺陷相互作用的过程。结果表明，激光阵列经过时间调制后辐照铝材料上激发出的声表面波，其垂直于表面方向的位移幅值与阵列中线源个数成线性比例；且巨声表面波与表面缺陷作用后所产生的反射回波的位移幅值也随着线源个数的增多得到明显增大。模拟结果对在激光超声检测中应用激光阵列提高声表面波的信噪比提供了理论依据。

通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上, 观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时, 衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明：衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关; 正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息; 正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。

提出了一种可用于几百赫兹低频液体表面声波研究的激光衍射法测量新技术。在实验上采用入射光掠入射到表面波上在远场得到了中间亮，两边暗的高反衬度的衍射条纹，实验中发现对频率为几百赫兹的低频衰减液体表面波，当移动振源改变激光入射点与振源间距离时发现零级条纹消失，这意味着此时的衍射效率接近100％。在理论上给出了衍射光强度与表面波振幅的解析关系，并利用所提出的新技术实现了对几百赫兹液体表面波的衰减系数的实时测量。

利用激光激发声表面波及光差分技术研究激光源对声表面波的影响。实验中利用了Nd∶YAG脉冲激光器激发超声，采用632nm的He－Ne激光器基于光束偏转法的光差分检测系统，测量了铝样品表面的声表面波，获得了很好的信号。在此基础上研究了激发源的形状和能量对激发的声表面波幅度的影响。同时从热弹和融蚀机制下讨论激光声表面波的产生。在这两种机制下，声表面波的幅度发生了很大的变化。随着激光能量密度的增加，声表面波的幅度由线性变化转换为非线性变化。这一结果对激光激发声表面波理论研究有一定的指导意义。

实验上实现了低频液体表面波的光衍射，当表面波波长远大于入射光波波长时，得到了稳定、清晰的衍射图样，并首次发现了衍射条纹具有明显的不对称分布．理论上对表面波衍射的近似条件进行了分析，得出了各级衍射条纹角宽度的解析表达式，解释了衍射条纹的非对称分布．衍射图样的不对称分布具有普遍规律，可观察的明显程度与表面波的波长和光波波长的比值有关，在能观察到衍射效应的条件下，当表面波波长远大于光波波长，非对称分布越明显，当表面波波长远接近光波波长时，衍射条纹可近似的看成是对称分布的．