Active tuning of vibration and noise by the optimal design of acoustic metamaterial structures

智能材料具有对外界力学环境变化的敏感性和主动响应能力，在结构振动主动控制中得到了广泛的应用。因此，这类智能材料在主动调谐声学超材料的带隙特性方面具有很大的潜力。基于这一事实，如果通过主动结构优化设计将智能材料嵌入到声学超材料结构中，则可以将声学超材料的被动隔声能力与智能材料的主动控制性能有效地结合起来。所提出的新型有源超材料结构将具有以下两个功能：(1)通过设计控制算法，可以主动调整超材料结构单胞的刚度和质量，以主动控制频带的宽度和位置；(2)利用声学超材料的带隙特性，可以抑制频带内的振动和噪声；而对于频带内的振动和噪声，可以通过智能材料的主动控制能力来抑制。因此，通过这种新的策略，可以在全频率范围内减小振动和噪声。本项目将提出并设计具有主动控制功能的新型声学超材料结构。在新的系统中，将采用压电巨纤维复合材料(MFC)作为主动控制器。考虑到材料的各向异性和MFC的机电耦合特性的影响，本文对MFC的带隙特性、隔声能力和主动控制优化设计进行了系统的理论、数值和实验研究。研究中将声学超材料的被动控制性能与压电材料的主动控制能力有效地结合起来，将结构的振动和噪声控制在期望的频率范围内，为结构振动控制、弹性波调谐以及新型降噪材料和结构的开发提供了新的思路和方法。因此，该项目对声学超材料和结构在减振降噪方面的创新工程应用具有重要意义。该项目是德国和中国申请者的合作项目。两支球队几年来一直保持着密切的合作。通过这一联合项目，应该继续和加强他们以前的合作。两个团队将在拟议的项目上合作，结合各自的研究优势，促进参与的德国和中国年轻科学家。

Smart or intelligent materials are widely used in the structural active vibration control because they have the sensitivity to external mechanical environment changes and the ability to actively respond. Therefore, these kinds of intelligent materials have a great potential to actively tune the band-gap properties of the acoustic metamaterials. Based on this fact, if the intelligent materials can be embedded into the acoustic metamaterial structures by using the active structural optimization design, the passive acoustic insulation ability of the acoustic metamaterials can be effectively combined with the active control performance of the intelligent materials. The proposed novel active metamaterial structures will possess the following two functions: (i) the stiffness and the mass of the unit-cell of the metamaterial structures can be actively tuned by the design of the control algorithm to actively control the widths and locations of the frequency band-gaps, and (ii) the vibration and noise in the frequency band-gaps can be suppressed by using the band-gap property of the acoustic metamaterials, while for the vibration and noise in the frequency pass-bands, they can be suppressed by the active control ability of the intelligent materials. Thus, the vibration and the noise can be reduced in the full frequency range via this proposed novel strategy. In this project, novel acoustic metamaterial structures with active control functions will be proposed and designed. In the novel systems, the piezoelectric macro-fiber composites (MFC) will be adopted as an active controller. Taking into account the effects of the material anisotropy and the electromechanical coupling properties of the MFC, theoretical, numerical and experimental investigations on the vibration band-gap property, the noise isolation ability and the active control optimization design will be systematically conducted. In the investigations, the passive control performance of the acoustic metamaterials and the active control ability of the piezoelectric materials will be effectively combined to suppress the vibration and the noise levels in the desired frequency range, which will provide a novel idea and a new approach for the structural vibration control, the elastic wave tuning and the development of novel noise reduction materials and structures. Thus, the project has a great importance and significance in innovative engineering applications of the acoustic metamaterials and structures for the vibration and noise reduction. This proposed project is a cooperation project by the German and the Chinese applicants. Both teams have a close cooperation since several years. Through this joint project, their previous cooperation should be pursued and strengthened. Both teams will work together on the proposed project, combine their individual research strengths and promote participating young German and Chinese scientists.