Beli Danilo, Fabro Adriano T, Ruzzene Massimo, Arruda José Roberto F
School of Mechanical Engineering, University of Campinas, Cidade Universitária, Campinas, SP, 13083-860, Brazil.
Department of Mechanical Engineering, University of Brasilia, Brasilia, DF, 70910-900, Brazil.
Sci Rep. 2019 Apr 4;9(1):5617. doi: 10.1038/s41598-019-41999-0.
Additive manufacturing has become a fundamental tool to fabricate and experimentally investigate mechanical metamaterials and phononic crystals. However, this manufacturing process produces spatially correlated variability that breaks the translational periodicity, which might compromise the wave propagation performance of metamaterials. We demonstrate that the vibration attenuation profile is strictly related to the spatial profile of the variability, and that there exists an optimal disorder degree below which the attenuation bandwidth widens; for high disorder levels, the band gap mistuning annihilates the overall attenuation. The variability also induces a spatially variant locally resonant band gap that progressively slow down the group velocity until an almost zero value, giving rise to wave trapping effect near the lower band gap boundary. Inspired by this wave trapping phenomenon, a rainbow metamaterial with linear spatial-frequency trapping is also proposed, which have potential applications in energy harvesting, spatial wave filtering and non-destructive evaluation at low frequency. This report provides a deeper understanding of the differences between numerical simulations using nominal designed properties and experimental analysis of metamaterials constructed in 3D printing. These analysis and results may extend to phononic crystals and other periodic systems to investigate their wave and dynamic performance as well as robustness under variability.
增材制造已成为制造和实验研究机械超材料及声子晶体的基本工具。然而，这种制造过程会产生破坏平移周期性的空间相关变化，这可能会损害超材料的波传播性能。我们证明，振动衰减曲线与变化的空间曲线严格相关，并且存在一个最佳无序度，低于该无序度时衰减带宽会变宽；对于高无序水平，带隙失谐会消除整体衰减。这种变化还会诱导出空间变化的局部共振带隙，该带隙会逐渐降低群速度直至几乎为零，从而在较低带隙边界附近产生波捕获效应。受这种波捕获现象的启发，还提出了一种具有线性空间频率捕获功能的彩虹超材料，其在能量收集、空间波滤波和低频无损评估方面具有潜在应用。本报告更深入地理解了使用名义设计属性的数值模拟与对3D打印构建的超材料进行实验分析之间的差异。这些分析和结果可能会扩展到声子晶体和其他周期性系统，以研究它们的波动和动态性能以及在变化情况下的稳健性。
