Robustly Tuning Bandgaps in Two-Dimensional Soft Phononic Crystals with Criss-Crossed Elliptical Holes

Tuning band gaps in soft materials by post-buckling deformation is becoming an appealing means to manipulate elastic waves. As one of the most favorable topologies, two- dimensional soft structures with circular holes have been extensively studied. Based on the contrarian thinking, this paper starts from the two-dimensional soft structures with criss-crossed elliptical holes, which is close to the post-buckling configuration of soft structures with circular holes, and then proposes to tune the band gaps through elongating or stretching rather than compressing. Influences of the loading magnitude and loading pattern （i.e., uniaxial and biaxial elongations） on the band gaps are studied via the nonlinear finite element simulations. Effects of the geometric parameters （the major-to-minor half-axis ratio and the porosity of the structure） are also discussed. It is shown that, compared with the traditional circular hole case, the band gaps of the unloaded structure with criss-crossed elliptical holes are much richer, and they could be reversely and continuously tuned by tensile loadings. In particular, the deformation is very robust and is insensitive to small geometric imperfections, which is always necessary for triggering the post-buckling deformations. The present work provides a useful reference to the manipula- tion of elastic waves in periodic structures as well as the design of soft phononic crystals/acoustic devices.

带隙可调的超结构梁：数值和实验研究（英文）

目的:1.研究晶格常数、预应力和弹簧刚度对超结构梁带隙的影响,优化结构并形成伪禁带或低频且宽的禁带;2.通过实验验证伪禁带的存在性、排列对带隙的影响以及缺陷对带隙的影响等。创新点:1.通过预应力调节超结构梁的带隙特征,并可以形成伪禁带;2.通过排列不同弹簧振子构成宽频禁带和宽频伪禁带。方法:1.通过有限元软件模拟预应力、弹簧刚度和晶格常数等参数对该超结构梁带隙的影响情况;2.设计合适的参数并进行结构优化,使得该结构的带隙宽,频率低,且易于实验实现;3.在实验中通过替换弹簧、改变弹簧间距和施加轴向拉力分别研究弹簧刚度、晶格常数和预应力的影响,并通过移除部分弹簧和同时布置不同弹簧的方式研究缺陷和排列对带隙的影响。结论:1.该结构存在一条局域共振禁带和多条布拉格散射禁带;通过调节预应力、弹簧刚度和晶格常数等可以有效地控制带隙特征。2.在特定条件下可以形成宽频伪禁带;通过排列不同弹簧振子可以达到拓宽禁带、形成宽频伪禁带的效果。3.缺陷对布拉格散射禁带的影响较大,对局域共振禁带的影响较小。

浙江大学智能材料与结构力学研究实验室（英文）

目的:如今新兴的智能化时代比以往任何时候都更需要性能优越的材料和结构来设计更灵活、更主动、更自动化的机器和系统,以应对越来越复杂的环境。本实验室力图探求智能材料与结构在实验或计算中观测到的力学现象(如自由振动、波传播以及结构失稳等)或是多场耦合行为背后的机理,从而为先进功能设备、机械以及机器人的创新发展提供参考。最终,开发具有卓越性能的新型智能多功能器件,以满足各种实验室、工业甚至社会应用的特殊或一般要求。研究点:1.智能结构的振动与失稳分析;2.软材料的设计与制备;3.声子晶体和超材料中弹性波的调控;4.智能材料和结构中的多场耦合行为分析;5.压电、多铁性以及压电电子学器件的研发;6.多轴力/力矩智能传感器的设计。展望:虽然对智能材料和结构的研究已有近40年的历史,且其在许多现代技术和工程领域中已有了成功的应用,但是即将到来的智能化时代对"智能力学"的需求将是无穷无尽的。如果说传感器和驱动器是智能化时代的基础,那么智能材料和结构就是这些基本设备的核心。新型多功能材料的开发显然为智能材料和结构力学带来了新的生机和活力。此外,拓扑物理学等新的科学概念也将为智能材料和结构的研究开辟新的方向。本实验室将继续为基础科学、技术发展以及智能材料和结构的实际应用做出贡献。