Materials Characterization with Nonlinear Surface Acoustic Wave Pulses

9970241 schuessler这项研究涉及固体材料中高振幅表面声波的传播，以及基于这些材料的特性来表征材料的新方法的发展。非线性现象的表现取决于固体的非线性弹性模量，它对材料中不同缺陷的出现很敏感。因此，非线性模量有望提供适合材料表征的信息。在这项工作中，将非线性声波传播的非线性演化方程的解拟合到实验测量的波形中，确定几种材料的三阶非线性模量。无接触激光方法将用于激发和探测表面声波。这些实验将用于检验最近关于这种波传播过程中不寻常特性的理论预测。这些包括波形的非线性畸变、高频谱成分的产生、激波锋面的形成以及随后波能量的非线性衰减，以及在某些条件下孤子的形成。该项目将为超硬材料薄膜和涂层的表征以及材料的粘弹性行为和各向异性的研究提供新的方法。这项工作的结果将对材料科学、声电子、非线性声学、非线性波理论和地震学等不同领域产生影响。固体的力学和弹性性能是反映其微观结构的重要特征。因此，开发新的多功能和信息丰富的方法来测量这些量是材料研究的持续任务之一。本课题的目标是研究表面声波在固体材料中的非线性传播，并基于这种非线性波的特性开发一种新的材料表征方法。这项研究将测试旨在描述这种波的现有理论模型，并将允许量化疲劳和裂纹形成等现象对材料弹性性能的影响。这项研究也将有助于金刚石和类金刚石薄膜和涂层表征技术的发展，以及晶体材料的弹性和其他特性。这项工作的结果将对材料科学、声电子学、非线性声学、非线性波理论和地震学等不同领域产生影响。该项目的一个重要特点是通过培养学生在材料科学和相关研究领域的新方法，将研究与教育相结合。

9970241 SchuesslerThis research concerns the propagation of high amplitude surface acoustic waves in solid materials and the development of a novel method for the characterization of materials based on the properties of such materials. The manifestation of nonlinear phenomena depends on the nonlinear elastic moduli of the solid, which are sensitive to the appearance of different defects in the material. The nonlinear moduli are therefore expected to give information suitable for materials characterization. In this work the third order nonlinear moduli will be determined for several materials by fitting the solutions of the nonlinear evolution equations of the nonlinear acoustic wave propagation to experimentally measured waveforms. Contact-free laser methods will be used for exciting and detecting the surface acoustic waves. The experiments will serve to test recent theoretical predictions concerning unusual properties during the propagation of such waves. These include nonlinear distortion of the wave shape, generation of high frequency spectral components, formation of a shock front with subsequent nonlinear attenuation of the energy of the wave and, under certain conditions, the formation of solitons. This project will contribute a new method for the characterization of thin films and coatings of superhard materials, as well as to the study of the visco-elastic behavior and anisotropy of materials. The results of this work will have an impact on different fields such as materials science, acoustoelectronis, nonlinear acoustics, the theory of nonlinear waves, and seismology.%%% Mechanical and elastic properties of solids are important characteristics reflecting their microscopic structure. Therefore the development of new versatile and informative methods to measure these quantities is one of the ongoing tasks of materials research. The objective of this project is to study the non-linear propagation of surface acoustic waves in solid materials and to develop a novel method of materials characterization based on the properties of such nonlinear waves. This research will test existing theoretical models that purport to describe such waves and will allow to quantify the influence of such phenomena as fatigue and crack formation on the elastic properties of materials. This research will also contribute to the development of a technique for the characterization of diamond and diamond like films and coatings, to the elastic and other properties of crystalline materials. The results of this work will have an impact on different fields such as materials science, acousto-electronics, nonlinear acoustics, theory of nonlinear waves, and seismology. An important feature of this project is the integration of research and education through the training of students in novel methods of materials science and related research areas.