Magnetorheological elastomers are a class of smart hybrid material where magnetic microparticles are embedded in an elastomer matrix. The combination of elastic and magnetic properties leads to highly complex material behaviour, which is strongly affected by the arrangement and the magnetically induced motion of the magnetic particles. Thus, the knowledge of the internal particle structure is key to gain a deeper understanding of the complex material behaviour. In this paper, X-ray microtomography was applied to analyse the internal particle structure of a magnetorheological elastomer containing magnetically hard NdFeB-particles. A stepwise magnetisation of the material enabled a detailed characterisation of the occurring non-reversible chain formation process. Furthermore, the application of magnetic fields during measurements enabled an analysis of a mostly reversible particle motion occurring in connection with the magnetorheological effect. The collected tomography data of the particle structure was evaluated on a single particle basis as well as by means of a direction-dependent pair correlation function. To provide a scale bridging between macroscopic and microscopic properties, the found results regarding the particle motion were linked to mechanical and magnetic properties of the material.

中文翻译：

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磁流变弹性体中钕铁硼粒子的可逆和不可逆运动

磁流变弹性体是一类智能混合材料，其中磁性微粒嵌入弹性体基质中。弹性和磁性的结合导致了高度复杂的材料行为，这受到磁性粒子排列和磁感应运动的强烈影响。因此，了解内部粒子结构是深入了解复杂材料行为的关键。在本文中，X 射线显微断层扫描用于分析含有硬磁 NdFeB 颗粒的磁流变弹性体的内部颗粒结构。材料的逐步磁化能够详细表征发生的不可逆链形成过程。此外，在测量过程中应用磁场能够分析与磁流变效应相关的几乎可逆的粒子运动。收集到的颗粒结构的断层扫描数据在单个颗粒的基础上以及通过依赖于方向的对相关函数进行评估。为了提供宏观和微观特性之间的尺度桥梁，关于粒子运动的发现结果与材料的机械和磁特性有关。