基于Biot理论的电磁流变液吸声特性研究

发布时间：2018-04-09 18:23

本文选题：电磁流变液　切入点：Biot理论　出处：《华中科技大学》2015年博士论文

【摘要】：电磁流变液是一类重要的智能软物质,在外加电场或磁场作用下,其内部悬浮颗粒形成沿外加场方向的有序结构,从而导致流变性能的巨变,且这种变化是可逆的。除了流变性能发生改变,由于电磁流变液的结构的变化,其诸多物理特性,如光学性能、声学性能等,都出现了外场可控的变化,这一特性使得电磁流变液在各个领域具有巨大的应用潜力。本文在对电磁流变液内部显微结构分析的基础上,提出将电磁流变液作为一种声传播媒质,围绕电磁流变液声传播机理、复合结构声学特性以及变化阻抗耦合层等方面,进行了理论建模和数值计算以及实验测试等方面的研究和探讨。论文的主要工作如下：提出了以电磁流变液作为一种性能可控的声传播媒质,为新型水下吸声材料的研究提供了理论基础。以悬浮液散射理论为基础,建立无外场作用下电磁流变液中的声学模型；以Biot理论为基础,建立了外加场作用下声波在电磁流变液中传播模型。将电磁流变液外场作用下形成的场致微结构等效为液体饱和的多孔结构,建立了以电磁流变液流变学动态测试结果和离散松弛谱理论相结合,获取其全频段动态剪切模量的等效处理方式。通过数值计算,对比了有、无外场作用下的电磁流变液层吸声特性,结果表明,外场作用下,声波在电磁流变液层内的耗散更多,说明了电磁流变液作为吸声介质的可行性。研究了声波在由流固两相多孔材料复合结构中的传播理论,讨论了不同流阻多孔材料的布局方式,并提出了利用多孔材料共振特性提高复合结构整体吸声性能的优化思路。建立了含电磁流变液层的复合结构声学模型。通过数值计算,讨论了电磁流变液层与多孔金属层的复合双层结构的水下吸声性能,研究了多孔结构中饱和液体、材料布局方式以及外加场作用情况对复合结构吸声性能的影响。结果表明,电磁流变液层的场致微结构能明显提高介质内的声能损耗,从而提高复合结构的吸声性能。高粘度的填充液体也有助于声波在两相介质内的损耗。在电磁流变液声阻抗可控的基础上,提出了以设计外加场等方式构建声阻抗连续变化的电磁流变液作为界面耦合层的声反射控制策略。以变参数声波方程为基础,结合传递矩阵法,建立了阻抗连续变化的电磁流变液中的声学模型。设计了几种阻抗分布形式,并数值仿真计算了不同分布形式的耦合层吸声系数。结果表明,随着声波入射,阻抗先缓慢变化、后迅速变化的指数型分布形式的耦合层的吸声性能最优。在此基础上,讨论了耦合层在界面处与入射介质或透射介质阻抗不匹配的情况。通过耦合层两端面材料的去除,能有效提高材料的使用效率。在理论研究的基础上,结合磁流变液的特性,设计了一款水下声学材料的阻抗管,并试验研究了外加磁场强度和磁流变液层厚度对其吸声系数的影响。结果表明,外加磁场的作用使得磁流变液的声阻抗特性发生了变化,结果与理论计算趋势一致。
[Abstract]:Electromagnetic rheological fluid is an important kind of intelligent soft material, in external electric field or magnetic field, the suspended particles to form ordered structure along the applied field direction, resulting in changes in rheological properties, and this change is reversible. In addition to the rheological properties change due to changes in the structure of the electromagnetic rheological fluid, its many physical properties, such as optical properties, acoustic properties, has changed the field controlled, which makes the electromagnetic rheological fluid have great potential applications in various fields. Based on the analysis of the electromagnetic rheological fluid internal microstructure on the electromagnetic rheological fluid as a propagation medium, electromagnetic flow around the liquid sound propagation mechanism of composite structure acoustic characteristics and changes in impedance coupling layer, studies the theoretical modeling and numerical calculation and experimental test and discuss the main. The work is as follows:
Put forward to the magnetorheological fluid as a medium of sound propagation properties of controllable, provides the theoretical basis for studying new sound-absorbing material under the water. With suspension scattering theory, establish the acoustic model under the action of electromagnetic field in the MR fluids; based on the Biot theory, established the external field acoustic wave the propagation model in the electromagnetic field. The rheological fluid electromagnetic rheological fluid formed under the field of micro structure is equivalent to the liquid saturated porous structure, established by electromagnetic rheological fluid dynamic rheological test results and the discrete relaxation spectrum theory, by taking the full band approach equivalent dynamic shear modulus. Through numerical calculation compared with that, no electromagnetic rheological fluid layer absorption characteristics under the external electric field. The results show that the field under the action of electromagnetic waves in dissipative fluid layer more, explains the electromagnetic rheological fluid for absorption The feasibility of the medium.
Study on the acoustic wave in the fluid solid two-phase porous material by composite structure in communication theory, layout of different flow resistance of porous materials is discussed, and put forward to improve the overall performance of the composite structure optimization method of sound absorption using the resonance characteristics of porous materials. A composite structure containing acoustic electromagnetic rheological fluid layer model. By numerical calculation, sound absorption the properties of the composite double-layer structure electromagnetic rheological fluid layer and a porous metal layer of water was discussed on the saturated liquid in the porous structure, and the influence of material layout function field on the sound absorption performance of the composite structure. The results show that the electromagnetic field induced fluid layer micro structure can significantly improve the energy loss in the medium. In order to improve the sound absorption properties of composite structure. The liquid filling high viscosity also contributes to the acoustic loss in two-phase medium inside.
On the basis of electromagnetic rheological fluid acoustic impedance controlled, is proposed to design the field construction methods such as electromagnetic rheological fluid continuous change of the acoustic impedance of the acoustic reflection as the control strategy of the interface coupling layer. The acoustic wave equation with variable parameters as the basis, combined with the transfer matrix method, establish the acoustic model of electromagnetic rheological fluid continuous change in impedance the design of impedance distribution form and several numerical simulation of coupling layer absorption coefficient of different distribution. The results show that with the incident wave impedance, first change slowly after the rapid change of the sound absorption performance of the optimal exponential distribution form of the coupling layer. On this basis, discussed the coupling layer at the interface and incident medium or transmission medium impedance mismatch. By removing the coupling layer two face material, can effectively improve the use efficiency of the material.
On the basis of theoretical research, combined with the characteristics of MRF, designed an underwater acoustic impedance material tube, and the effects of magnetic field intensity and magnetic rheological liquid layer thickness on the sound absorption coefficient. The results show that the magnetic field makes the acoustic impedance characteristics of magnetorheological fluid changes the results with the theoretical calculation, the same trend.

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB381

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