In this work a comparison of dielectric and mechanical data is presented based on experiments within the linear response limit and beyond that limit. The linear dynamic and shear-mechanical response is discussed in terms of the molecular supercooled liquid tetramethyl-tetraphenyl-trisiloxane. As the dynamics measured by the two methods depict the same temperature-dependence, the underlying cause for the observed responses is assumed to be identical for both methods, namely structural relaxation. The comparison of dielectric and mechanical measurements under high excitation amplitudes reveals that this cannot be assumed for the nonlinear response: Mechanical experiments on metallic glasses suggest that involved energies are clearly beyond k B T, with observed nonlinear effects based on the activation of microstructural plastic rearrangements. In contrast, nonlinear dielectric measurements on another molecular glass-former involve energies clearly below k B T, so that nonlinear dielectric effects occur due to energy uptake from the electric field or entropy-based changes in the dynamics, but are very unlikely connected to the triggering of plastic rearrangements by the applied electric field.

中文翻译：

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线性范围内外的机械和介电响应

在这项工作中，基于线性响应限制内和超出该限制的实验，对介电和机械数据进行了比较。根据分子过冷液体四甲基-四苯基-三硅氧烷讨论线性动态和剪切机械响应。由于这两种方法测量的动力学描述了相同的温度依赖性，因此假设两种方法观察到的响应的根本原因是相同的，即结构松弛。在高激发振幅下的介电和机械测量的比较表明，这不能假设为非线性响应：金属玻璃的机械实验表明，所涉及的能量显然超出了 k BT，观察到的非线性效应基于微结构塑性重排的激活。