![]() ; ; Baller, Jörg ![]() in Journal of Physics. Conference Series (2006), 40 The elastic properties of the isotropic state of condensed matter are given by the elastic constants ell and c44. In the liquid state the static shear stiffness c44 vanishes whereas at sufficient high ... [more ▼] The elastic properties of the isotropic state of condensed matter are given by the elastic constants ell and c44. In the liquid state the static shear stiffness c44 vanishes whereas at sufficient high probe frequencies a dynamic shear stiffness may appear. In that latter case the question about the existence of a Cauchy relation appears. It will be shown that a pure Cauchy relation can appear only under special conditions which are rarely fulfilled. For all investigated materials, including ceramics, liquids and glasses, a linear relation between ell and c44 called generalized Cauchy relation is observed, which, surprisingly, follows a linear transformation. [less ▲] Detailed reference viewed: 161 (9 UL)![]() ; Krüger, Jan-Kristian ![]() in Journal of Physics : D Applied Physics (2005), 38(12), 2026-2030 High performance Brillouin microscopy (BM) has been used to characterize the spatial distribution of piezoelectrically induced acoustic fields excited at microwave frequencies in a LiNbO3 single crystal ... [more ▼] High performance Brillouin microscopy (BM) has been used to characterize the spatial distribution of piezoelectrically induced acoustic fields excited at microwave frequencies in a LiNbO3 single crystal. It is demonstrated that under suitable conditions BM is able to detect microwave-induced bulk as well as surface acoustic waves. Brillouin spectroscopy is able to probe sound wave intensities of induced phonons, which are as small as those of thermal phonons. [less ▲] Detailed reference viewed: 87 (1 UL)![]() Krüger, Jan-Kristian ![]() ![]() in Adhesion - Current Research and Application (2005) Detailed reference viewed: 89 (6 UL)![]() Krüger, Jan-Kristian ![]() in Journal de Physique IV (2005), 129 From the structural point of view a simple Cauchy relation is not expected to hold for isotropic materials. Such a Cauchy relation would imply the reduction of independent elastic stiffness constants for ... [more ▼] From the structural point of view a simple Cauchy relation is not expected to hold for isotropic materials. Such a Cauchy relation would imply the reduction of independent elastic stiffness constants for the isotropic state from two to one. However, high frequency elastic data of glasses and viscous liquids show a linear transformation between the shear and the longitudinal elastic stiffness which is called a generalized Cauchy relation. It seems, that the parameters of the linear transformation are related to the global and local symmetry and/or order. Brillouin investigations on the elastic stiffness coefficients of a consolidated nano-crystalline material (CeO2) and of DGEBA/SiO2 nano-composites are used in order to elucidated the role of the discrepancy between local and global symmetry and/or order. [less ▲] Detailed reference viewed: 69 (10 UL) |
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