Wang Aoxi, Chen Chang Qing
Department of Engineering Mechanics, Center for Nano and Micromechanics and Key Laboratory of Applied Mechanics, Tsinghua University, Beijing 100084, China.
Natl Sci Rev. 2024 Mar 22;11(9):nwae110. doi: 10.1093/nsr/nwae110. eCollection 2024 Sep.
The confinement of waves within a waveguide can enable directional transmission of signals, which has found wide applications in communication, imaging, and signal isolation. Extending this concept to static systems, where material deformation is piled up along a spatial trajectory, remains elusive due to the sensitivity of localized deformation to structural defects and impurities. Here, we propose a general framework to characterize localized static deformation responses in two-dimensional generic static mechanical metamaterials, by exploiting the duality between space in static systems and time in one-dimensional non-reciprocal wave systems. An internal time-reverse symmetry is developed by the space-time duality. Upon breaking this symmetry, quasi-static load-induced deformation can be guided to travel along a designated path, thereby realizing a stress guide. A combination of time-reverse and inversion symmetries discloses the parity-time symmetry inherent in static systems, which can be leveraged to achieve directional deformation shielding. The tailorable stress guides can find applications in various scenarios, ranging from stress shielding and energy harvesting in structural tasks to information processing in mechanical computing devices.
波在波导内的限制能够实现信号的定向传输，这在通信、成像和信号隔离等领域有着广泛的应用。将这一概念扩展到静态系统中，即材料变形沿着空间轨迹堆积，由于局部变形对结构缺陷和杂质的敏感性，目前仍然难以实现。在这里，我们提出了一个通用框架，通过利用静态系统中的空间与一维非互易波系统中的时间之间的对偶性，来表征二维通用静态机械超材料中的局部静态变形响应。通过时空对偶性发展出一种内部时间反演对称性。打破这种对称性后，准静态载荷引起的变形可以被引导沿着指定路径传播，从而实现应力引导。时间反演对称性和空间反演对称性的结合揭示了静态系统中固有的宇称-时间对称性，可利用这一特性实现定向变形屏蔽。可定制的应力引导在各种场景中都有应用，从结构任务中的应力屏蔽和能量收集到机械计算设备中的信息处理。
