【作者】 丁律辉；

【导师】 黄其柏；

【作者基本信息】 华中科技大学 ， 机械设计及理论， 2010， 博士

【摘要】 电流变液是一种智能材料,也属于复杂流体的范畴。电流变液在外电场作用下可以形成沿电场的有序结构,从而导致流变行为巨变。其结构、形态等发生由无序向有序转变,从而使得其许多物理性能(如光学性能、微波性能、流变学性能和声学性能等)出现可调节行为,这些特征使其在技术上具有巨大的应用潜力。本文在介绍电流变液声学特性的基础上,提出以电流变液作为一种水下声学材料,围绕其若干关键技术问题,在理论建模、数值计算以及实验等方面进行了研究和探讨；结合工程实际提出了几种新型的声学结构,建立了声波在几种新型结构中的传播计算模型,并比较了声波在其中的传播特性。论文的主要工作如下：提出了以电流变液作为一种新型的声学材料,将它用于水下吸声。同时以Biot理论为基础,建立声波在电流变液中的传播模型,修正了相关Biot参数,计算了在不同电场下声波传播速度和衰减因子；通过数学模型比较了各Biot参数对声波传播特性的影响；对比理论计算结果和实验结果可知,利用Biot理论建立的声波传播模型与实验结果相吻合,理论模型正确。研究了声波在分层介质中的传播理论,设计了几种透声结构和隔声结构。以Biot理论为基础建立了透声结构声波反射系数的有限元计算模型和隔声结构隔声性能的Matlab计算模型：通过计算比较可知：对于透声结构,多层非均匀介质叠合时,非均匀层中电流变液域不同的布置方式对其结构的反射系数有一定的影响；对于电流变液隔声结构,与双层夹心板相比,三层夹心板在中高频段隔声性能有明显优势,但低频段隔声性能有一定程度上的下降。提出了利用电流变液作为梯度声学材料的理论依据,基于传递矩阵法建立了声波在阻抗连续变化的电流变液中的声学模型,推导了声波的传播计算公式；结合声波在电流变液中传播的Biot模型计算结果,数值模拟了电流变液在不同声阻抗分布时其表面的反射系数；对不同梯度分布的情况下电流变液的声波反射特性进行了分析,为工程应用提供了理论基础。针对电流变液的特点,在总结目前电流变液控制策略的基础上,结合电流变液声阻抗匹配的控制原则,提出了将模糊控制理论应用于本控制系统中,并对控制器输入输出变量选择、控制器控制规则的设计以及模糊控制逻辑推理等问题进行了研究。在此基础上设计出了一个控制系统,比较控制前后电流变液表面的声学特性；控制结构表明模糊控制理论在设计的控制系统中效果明显。在理论研究的基础上设计了一种电流变液声波反射特性的测试系统。实验表明,在对电流变液施加不同电场以及结构中电流变液不同体积比时,其表现出来的声学特性呈现出巨大差异。实验结果与理论计算结果基本吻合。更多还原

【Abstract】 The electrorheological fluid, among the complex fluids, is a kind of smart or intelligent materials. At the presence of an external electric field, the dispersed particles in ER suspensions can form orderly microstructures to a certain extent, resulting in the drastic changes of many physical properties of the materials. So in the dissertation, the electrorheological fluid as the water acoustical material is proposed. Then put the emphasis on the study about the theoretical model, the numerical calculation and experiment. Combined with practice, several acoustical structure is designed, and the characteristic of acoustic wave in its is researched. The main works in the dissertation are list as following:The electrorheological fluid as the water acoustical material is proposed. Base on the Biot theory, the model of the acoustic wave’s propagation is established. To get the result uniformed with experiment, some Biot parameters are modified. The speed of acoustic wave and the loss factor in different electric field are calculated based on the acoustic model. From the result, we can find the influence of different Biot parameters. The theoretical results and experimental results show that the acoustic model based on Biot theory is right.Research the propagation of acoustic wave in layered media and the layered media composing the electrorheological fluid is proposed. For calculating the reflect coefficient, the FEM model based on Biot theory is build. Acoustical insulation analysis and calculation is done through the Matlab. Several acoustic structures are designed. The calculation results show that the arrangement ways of electrorheological fluid is important factor of the acoustical structure. Comparing the double sandwich with the three layered sandwich, the characteristic of sound insulation of the three layered sandwich in middle and high frequency is better, but in the low frequency, the double sandwich is better.The electrorheological fluid is proposed as a gradient acoustic media. On the electric field, the impedance of electrorheological fluid is changeable, the ER fluid have the potential to be active acoustic impedance matching materials, which could especially useful for the matching acoustic impedance between a solid transducer and fluids. In the dissertation, the model of acoustic wave propagation in an inhomogeneous layer is established which based on wave equations. Further we got the transmission matrix of this inhomogeneous layer and derive the energy reflection coefficients for it. Based on this mathematic model, we calculate the reflection coefficients for inhomogeneous layer with different impedance profile, and then the better impedance profile is got.According to the characteristic of electrorheological fluid, fuzzy control method is proposed. Combined with the impedance match method, a new control strategy is applied to the control system. Then puts emphasis on the study about the input/output variable, the control rules and the logical reasoning of controller. At last, the experiment is carried out. The results denoted that the active sound absorption method is feasible.Based on the theory research, a test system is designed which can test the reflection coefficient of electrorheological fluid. From the experiment result, we can know that under the different field, the reflection coefficient and impedance present drastic changes, and the result of the theoretical analysis are proved at the same time.更多还原