Pattern-Changing Instabilities and Giant Magnetostriction in Periodic Magnetoelastic Composites

这项资助的研究目标是阐明具有周期性微观结构的磁弹性复合材料中某种类型的“模式变化”不稳定性的影响，以实现比这些系统迄今为止可能的更大的磁致伸缩应变。在纯机械的背景下，已知这些图案变化不稳定性，其中复合材料中的变形从通常的单胞周期性图案突然改变（或分叉）为涉及胞之间的集体相互作用的新的较低能量变形图案，通常与“软”变形模式相关联，其中所施加应力的小变化可导致大应变。在早期工作的基础上，理论工具将被设计用于有效地模拟这些不稳定性的可能出现和复合材料在分叉后的“软”制度的宏观响应。这些工具将被用来设计磁弹性复合材料，能够显着更大的（“巨”）磁致伸缩应变比迄今为止。这项研究将导致新的和高效的多场建模技术，这将是广泛应用于大类的活性材料系统，并将借给自己的数值实现有限元代码。磁致弹性复合材料的建模和微结构设计的改进导致大的磁致伸缩应变应导致这些材料在许多工业应用中的性能增强，从汽车悬架系统中的自适应调谐减振器到机器人工业中的人工肌肉，以及声子和光子带隙开关。这项研究将与教育和外联活动协同进行。

The research objective of this grant is to elucidate the effect of a certain type of "pattern-changing" instabilities in magneto-elastic composites with periodic microstructures in order to achieve much larger magnetostrictive strains than have been possible to date in these systems. In the purely mechanical context, it is known that these pattern-changing instabilities, where the deformation in the composite abruptly changes (or bifurcates) from the usual one-cell periodic pattern to a new, lower energy deformation pattern involving collective interactions between the cells, is typically associated with a "soft" mode of deformation, where small changes in the applied stress can lead to large strains. Building on earlier work, theoretical tools will be designed for modeling efficiently the possible appearance of these instabilities and the macroscopic response of the composite in the post-bifurcation "soft" regime. These tools will then be used to design magneto-elastic composites that are capable of significantly larger ("giant") magnetostrictive strains than have been possible to date. This research will result in novel and highly efficient multi-field modeling techniques, which will be of broad application to large classes of active material systems, and will lend themselves to numerical implementation in FEM codes. Improvements in the modeling of magneto-elastic composites and in the design of microstructures leading to large magnetostrictive strains should lead to enhanced performance of these materials in many industrial applications, ranging from adaptive tuned vibration absorbers in automotive suspension systems to artificial muscles in the robotics industry, as well as phononic and photonic bandgap switches. The research will be conducted synergistically with educational and outreach activities.