Stolbov Oleg, Raikher Yuriy
Laboratory of Physics and Mechanics of Soft Matter, Institute of Continuous Media Mechanics, Ural Branch, Russian Academy of Sciences, 614068 Perm, Russia.
Polymers (Basel). 2020 Dec 8;12(12):2933. doi: 10.3390/polym12122933.
Magnetostriction effect, i.e., deformation under the action of a uniform applied field, is analyzed to detail for a spherical sample of a magnetoactive elastomer (MAE). A close analogy with the field-induced elongation of spherical ferrofluid droplets implies that similar characteristic effects viz. hysteresis stretching and transfiguration into a distinctively nonellipsoidal bodies, should be inherent to MAE objects as well. The absence until now of such studies seems to be due to very unfavorable conclusions which follow from the theoretical estimates, all of which are based on the assumption that a deformed sphere always retains the geometry of ellipsoid of revolution just changing its aspect ratio under field. Building up an adequate numerical modelling tool, we show that the 'ellipsoidal' approximation is misleading beginning right from the case of infinitesimal field strengths and strain increments. The results obtained show that the above-mentioned magnetodeformational effect should distinctively manifest itself in the objects made of quite ordinary MAEs, e.g., composites on the base of silicone cautchouc filled with micron-size carbonyl iron powder.
对磁致伸缩效应，即在均匀外场作用下的变形，进行了详细分析，对象是磁活性弹性体（MAE）的球形样本。与球形铁磁流体液滴在外场作用下的伸长有密切的相似性，这意味着类似的特征效应，即滞后拉伸和转变为明显的非椭球体，也应是MAE物体所固有的。到目前为止缺乏此类研究似乎是由于理论估计得出的非常不利的结论，所有这些估计都基于这样的假设，即变形球体始终保持旋转椭球体的几何形状，只是在磁场作用下改变其纵横比。通过建立一个适当的数值建模工具，我们表明，从无穷小场强和应变增量的情况开始，“椭球体”近似就是误导性的。所得结果表明，上述磁致变形效应应在由相当普通的MAE制成的物体中明显表现出来，例如以填充微米级羰基铁粉的硅橡胶为基础的复合材料。
