【作者】 陈源；

【导师】 师汉民； 胡于进； 黄其柏；

【作者基本信息】 华中科技大学 ， 机械设计及理论， 2006， 博士

【摘要】 声子晶体是一种具有弹性波带隙的结构和材料,由于通常情况下声子禁带起始频率很高,难以满足噪声控制的需要。正是这方面的原因,导致声子晶体在噪声控制应用上受到了限制。所以本文围绕周期结构的带隙机理,特别是低频带隙机理进行了深入研究,揭示其影响带隙有效衰减特性的关键因素。同时,本文也将解决周期性结构在低频降噪应用方面所面临的瓶颈问题,并把该项目的研究成果应用于汽车的噪声控制,为进一步提高我国汽车的整体综合性能提供技术保障。周期性结构的带隙机理研究具有重要的理论和应用价值。本学位论文主要作出了以下几个方面的研究工作:研究了人工编织一维二元声子晶体,通过建立人工一维二元声子晶体动力学模型,计算了其弹性波带隙,并且从理论上找到了一种带隙起始频率低且带宽很宽的一维声子晶体理论结构,为实际构建用于噪声控制的周期性结构提供了理论依据。首次研究了传统多层结构中的无限周期性多层结构的弹性波带隙,通过建立周期性多层结构的振动模型,计算了其带隙。在此基础上研究了有限周期多层结构的传输特性曲线即频响曲线。实例数值计算结果表明:频响曲线上弹性波衰减较大的频率区间与无限周期结构的弹性波带隙一致,所以通过选择合适的材料,能够得到低频的声子带隙。实验验证了周期性多层结构的带隙存在。从二维周期性结构的振动方程出发,建立了二维带隙计算模型,并在此基础上分析了带隙与材料结构特性的关系。实例数值计算结果证明:理论结果与试验仿真计算结果是一致的。根据三维有限周期结构的特点,通过对有限周期结构的有限元的划分,得出了三维有限周期结构振动传输特性的微分方程;分析了不同结构形式和基体材料对传输特性的影响。要把周期性结构成功应用于车内噪声控制,还必须有效解决车身声传递通道识别与车内噪声测试。而车身是复杂结构腔体,由于其结构和材料的复杂性,所以在声学中求解复杂结构的传递函数及其内部声场是一个极其复杂的问题。为了很好解决复杂结构腔体的声学问题,本文提出了基于“虚拟系统”测量复杂结构“综合传递函数”的方法,并预测复杂结构内部任意点的声场。为利用周期性结构有效进行车内噪声控制提供科学依据。最后,基于前面的理论和实验研究结果,本文以模拟车身为实验对象,研究周期性结构在车内噪声控制上的实际应用效果,试验结果验证了理论的正确性。总之,本文从车内低频噪声控制的实际需要出发,通过理论分析、数值计算,深入研究了周期性结构的带隙机理,为人工编织周期性结构和材料提供了理论基础。本文的研究成果为振动与噪声控制,特别是低频振动和噪声控制提供了理论依据。该研究具有重要的理论意义和工程实用价值。更多还原

【Abstract】 Phononic crystals are the periodic elastic materials or structures. As the low-peak of wide frequency band gaps in phononic crystals is higher, it is difficult to be used in the control of vibration and noise. In this dissertation, the band gaps mechanism, especially low frequency band gaps mechanism of periodic structures was studied and the key factor that influences the low frequency band gaps mechanism is found and proved. The problems restricting the application of it in low-frequency vibration/noise are solved. The research results are meaningful for the application in the control of vibration/noise and will offer us new ways inside vehicle vibration and sound control.The major innovations of this dissertation are as follows:A manual weave one-dimensional two-component phononic crystal was studied. Through establishing the manual weave phononic crystals’dynamics model, the elastic wave band gaps was calculated and concerned with the phononic crystal material characteristic. The study is available for low & high frequency noise and vibration control.The vibration model of periodic multiplayer structure is established and the phononic band gaps was calculated. By choosing the proper materials, the low frequency phononic band gaps can be gained. The results provide theory base for applications in control of noise and vibration. And then by analyzing the periodic mass-spring structure model, the elastic wave band gaps of periodic multiplayer structure can be estimated and the wave band gap of periodic multiplayer structure was validated by the experiment and application in vibration and noise control inside automobile was opened up.By analyzing the vibration model of two-dimensional (2D), the elastic wave band gaps of 2D was calculated. The mechanism of band gaps was gained and then the results provide theory base for weaving 2D phononic crystals being used noise and vibration control.Finally numerical calculation method was applied to calculate the frequency response of finite periodic structure, and two results match well. The conclusions are well validated by the experiment.The finite periodic structure of three-dimensional is very complex. The finite difference time domain method was appied to calculate the the frequency response of 3D finite periodic structure and then the frequency responses of difference structures and difference materials were gained. The results were validate by experiment.In order to solve the applications of the periodic structure, transfer channels of vehicle body must be measured. The vehicle body is complex structure. Complex structure is composed of multiple materials and its shape is also irregular. It is very difficult to gain complex structure transfer function and inner sound field. In order to measure complex structure transfer function and calculate inner sound field, transfer function of integration is mentioned. By establishing virtual system, transfer function of integration can be measured and the inner sound field can also be calculated. In the experiment, automobile body transfer function of integration is measured and experimental method of establishing virtual system is very valid.Finally, the wave band gap of periodic multiplayer structure was validated by the experiment and application in vibration and noise control inside automobile was opened up.更多还原