磁力负刚度薄膜结构吸声机理研究及优化设计

A light and thin design of low frequency sound absorbers has been a challenging task. For a membrane absorber, it usually requires a large back cavity for the low frequency sound absorption that make the realization of thin and light sound absorber difficult. In this study, a low-frequency resonant membrane absorption unit and its periodic structure with magnetic negative stiffness are designed utilizing nonlinear magnetic absorption and local resonance mechanisms. Then, a series of theoretical models is derived and constructed for them, such as the nonlinear dynamic equations, magnetic negative stiffness theoretical calculation models and sound absorption theoretical models. After that, simulations and experimental tests on the sound absorption performance of the designed unit and its periodic structure are performed. Finaly the sound-absorption mechanism, vibrational modes, and key physical structural design of the sound-absorber unit including its periodic structure are studied in depth, and methods for optimization of its design are proposed. Through the combination of theoretical modeling, simulation analysis and experimental verification, this study will ultimately attain a thin and light membrane sound absorer with magnetic negative stiffness, which is optimized for low-frequency and broad-band absorption. The results are of theoretical and practical significance for applications such as aerospace and traffic noise alleviation, where thin and lightsound-absorbing materials are necessary.

轻薄结构实现低频声波的吸收一直都是一个颇具挑战性的任务，针对低频共振吸声结构背腔深度较大、频带较窄且难以实现轻薄结构设计的问题，本课题以薄膜共振结构为研究对象，利用非线性磁力吸附作用及局域共振机理，设计实现磁力负刚度薄膜低频吸声单元及其周期结构，建立结构的非线性动力学方程、磁力负刚度计算模型及其吸声理论模型；在上述吸声单元及其周期结构理论研究基础上，对其吸声性能进行仿真分析和实验验证，深入研究单元及其周期结构的吸声机理、振动模态及关键物理结构设计，并提出优化设计方法。整项研究采用理论建模、仿真分析和实验验证相结合的方法，最终将实现轻薄低频宽带及优化的磁力负刚度薄膜吸声结构，这将为航空航天、交通噪声等需要采用轻薄吸声材料的应用领域提供新的研究成果，具有理论和实际意义。

在噪声控制领域，轻薄结构实现低频声波的吸收一直都是一个颇具挑战性的任务，一个小巧紧凑的亚波长吸收结构的实现对于噪声控制具有重要理论及实际意义。针对低频共振吸声结构背腔深度较大、频带较窄且难以实现轻薄结构设计的问题，本课题以薄膜共振结构为研究对象，利用磁力吸附作用及局域共振机理，设计实现磁力负刚度薄膜低频吸声单元及其周期结构，建立结构的动力学方程、磁力负刚度计算模型及其吸声理论模型；在上述吸声单元及其周期结构理论研究基础上，对其吸声性能进行仿真分析和实验验证，深入研究单元及其周期结构的吸声机理、振动模态及关键物理结构设计，提出优化设计方法。通过理论及实验研究表明，磁力负刚度作用，使得结构具备良好的低频特性，同等低频吸声范围，背腔深度可以减少50%以上；可以利用2cm深度背腔，实现100-600Hz可调的低频吸声结构设计，这些研究结果，为后续大面积周期结构的声场控制奠定基础，同时为航空航天、交通噪声等需要采用轻薄吸声材料的应用领域提供新的研究成果，具有理论和实际意义。