Materials Characterization with Nonlinear Surface Acoustic Wave Pulses

9970241 Schuessler本研究关注高振幅表面声波在固体材料中的传播，并开发了一种新的方法，用于表征基于此类材料的特性的材料。 非线性现象的表现取决于固体的非线性弹性模量，这对材料中不同缺陷的出现很敏感。 因此，非线性模量预计将提供适合材料表征的信息。 在这项工作中，三阶非线性模量将确定几种材料的非线性声波传播的非线性演化方程的解决方案，以实验测量的波形。非接触激光方法将用于激发和检测表面声波。 这些实验将用于测试最近关于这种波传播过程中不寻常性质的理论预测。 这些包括波形的非线性失真，高频频谱成分的产生，冲击波阵面的形成，随后的非线性衰减的波的能量，并在某些条件下，形成孤子。 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一种新的方法。 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。 固体的力学和弹性性质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化的方法来测量这些量是材料研究的持续任务之一。 本项目的目标是研究固体材料中表面声波的非线性传播，并根据这种非线性波的特性开发一种新的材料表征方法。 这项研究将测试现有的理论模型，旨在描述这种波，并将允许量化的影响，如疲劳和裂纹的形成等现象的材料的弹性性能。 这项研究也将有助于发展一种技术，用于表征金刚石和类金刚石薄膜和涂层，晶体材料的弹性和其他性能。 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对学生进行材料科学和相关研究领域的新方法培训，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.