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arXiv 1906.08087cond-mat.softphysics.comp-ph
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Zabolotskaya方程对所有不可压各向同性弹性固体的推广

Generalization of the Zabolotskaya equation to all incompressible isotropic elastic solids

Michel Destrade, Edvige Pucci, Giuseppe Saccomandi

摘要:

我们研究了由反平面剪切运动和一般平面内运动组成的小而有限振幅的弹性剪切波。我们使用一个多尺度的扩展,推导出一个渐近系统的耦合非线性方程描述其传播在所有各向同性不可压缩的非线性弹性固体,推广标量Zabolotskaya方程的可压缩非线性弹性。我们表明,对于一般各向同性不可压缩固体,反平面和平面内运动之间的耦合不能撤销,从而得出结论,线性偏振是不可能的一般非线性二维剪切波。然后,我们使用的方程来研究在软固体中的非线性高斯光束的演化:我们表明,一个纯(线性偏振)剪切光束源只产生奇次谐波,但在源信号中引入轻微的面内噪声导致第二谐波,相同的幅度作为第五谐波,最近实验观察到的现象。最后,我们提出了一些特殊的剪切运动与线性极化的例子。

英文摘要:

We study elastic shear waves of small but finite amplitude, composed of an anti-plane shear motion and a general in-plane motion. We use a multiple scales expansion to derive an asymptotic system of coupled nonlinear equations describing their propagation in all isotropic incompressible non-linear elastic solids, generalizing the scalar Zabolotskaya equation of compressible nonlinear elasticity. We show that for a general isotropic incompressible solid, the coupling between anti-plane and in-plane motions cannot be undone and thus conclude that linear polarization is impossible for general nonlinear two-dimensional shear waves. We then use the equations to study the evolution of a nonlinear Gaussian beam in a soft solid: we show that a pure (linearly polarised) shear beam source generates only odd harmonics, but that introducing a slight in-plane noise in the source signal leads to a second harmonic, of the same magnitude as the fifth harmonic, a phenomenon recently observed experimentally. Finally, we present examples of some special shear motions with linear polarisation.

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