【作者】 黄修长；

【导师】 华宏星；

【作者基本信息】 上海交通大学 ， 机械设计及理论， 2011， 博士

【摘要】 舱筏隔振技术是当前舰船减振降噪领域的关键技术,它可以有效地隔离舰船主、辅机系统和其它动力设备的机械振动传递,降低艇体的水下辐射噪声。在以声学设计为主导的安静型潜艇设计中,机械系统噪声定量预报和机械噪声控制及优化是潜艇机械噪声研究急需突破的两大问题。因此,本论文以“十一五”国防预研项目“浮筏声学性能优化”,“高性能主动隔振器的研究”和国家安全重大基础研究973项目子专题“高效隔振浮筏声学构建原理”为背景,突破传统的隔振与总体声学性能割裂的局限性,致力于建立舱筏隔振系统定量化的振动传递及声辐射计算方法和以声学性能为目标的优化方法,并有针对性地提出舱筏振动传递控制和远场声辐射抑制方法,以指导舱筏声学设计,降低整艇机械噪声,该研究具有重要的国防意义和实用价值。第一章,在阅读大量相关文献的基础上,全面综述了柔性复杂隔振系统的弹性耦合效应、水下复杂圆柱壳体结构的流固耦合效应的研究发展概况。从研究对象和建模方法两个角度分别进行论述,介绍了若干极具潜力的舱筏隔振系统建模方法。较为全面地综述了舱筏隔振系统的主、被动和宽频带振动噪声控制方法及隔振系统振动声学性能优化方法,指出当前建模、控制和优化方法在指导舱筏隔振系统声学设计和优化、控制的难点所在。第二章,针对舱筏隔振系统的定量化声学设计这一目标,利用基于频响函数综合的弹性子结构建模方法和基于解析试函数的有限元、边界元耦合方法,建立了典型舱筏隔振系统振动传递和声辐射的整体模型。研究了舱筏隔振系统的多点多向各个层面的弹性耦合效应、艇外流场的流固耦合效应及隔振器的驻波效应对舱筏隔振系统振动传递和声辐射特性的影响,并对结果进行讨论分析,得到了一些颇具价值的结论。讨论分析了带内部基座的圆柱壳体子结构参数变化对舱筏隔振系统振动传递和声辐射特性的影响,给出了带内部基座的圆柱壳体结构的声学设计原则。提出了基座均方力和均方速度传递率,功率流传递率,壳体表面均方振速传递率,壳体表面辐射声功率传递率和远场均方声压传递率等隔振系统振动传递和声学性能评价指标,分析了隔振性能评价指标和远场声辐射指标之间的关系,给出了不同载荷工况下可以替代远场声压评价指标的性能指标。第三章,针对舱筏隔振系统中、高频基础非刚性导致隔振性能下降,引起水下远场声辐射增强的问题,利用弹性波在周期结构阻带内无法传播的特性,提出了在振动传递途径上设置周期结构,对特定带宽频率内的振动传递进行纯被动宽频带的控制方法以及一种曲梁周期结构,充分利用曲梁具有径向刚度和切向刚度耦合及波型转换的特性,利用曲梁来传递载荷。利用波动法系统地研究了曲梁和直梁,曲梁和质量耦合系统中波的传播,传递和反射,验证了振动经过曲梁传递后发生的波型转换特性和能量的传递、反射。为简化曲梁周期结构的设计,提出了m-k等效模型,利用传递矩阵不变量法和波向量法研究了曲梁周期结构的带隙特征和输入输出导纳特性,结果表明曲梁周期结构具有较低频段的宽频带隙。利用传递矩阵法研究了曲梁周期结构在基础为弹性板的单自由度系统、两自由度系统和舱筏隔振系统中的应用。结果表明,曲梁周期结构作为机械滤波器能有效地抑制带隙内基础共振峰和上、下隔振器驻波频率处的振动传递和声辐射。在理论分析的基础上,给出舱筏隔振系统中曲梁周期结构工程实用的设计原则和方法。第四章,针对低频共振峰处的振动传递和导致的基座-壳体结构的声辐射,采用主动隔振的方法对其进行控制。以内部弹性子结构振源-多通道主被动隔振器-水下带基座的圆柱壳体结构受体这一耦合系统为研究对象,利用基于频响函数综合的子结构方法和基于FxLMS的多通自适应控制算法,建立了该耦合系统的动力学模型和控制模型。结合耦合的有限元、边界元模型,首次研究了对基座连接点的振动加速度进行主动控制时,对水下远场声辐射抑制的影响。数值仿真结果表明,采用主动隔振对基座各连接点的振动加速度进行控制后,可以有效地抑制低频时壳体径向变形为主的强全局辐射模态的声辐射,但抑制效果受到各个控制通道之间耦合强弱的影响,并与圆柱壳体结构的模态密切相关。在理论分析的基础上,对由振源板-四通道主动隔振器-流体加载板组成的主动隔振系统进行实验研究,对系统某阶共振频率(对应流体加载板的第一阶共振模态)受到接近该频率的激励干扰时进行主动控制,实验结果表明该频率处流体加载板连接点的振动和水下声辐射得到了明显的抑制。这位机械-结构的低频振动噪声控制提供了一种控制手段。第五章,以舱筏隔振系统的声学优化设计为目标,利用基于频响函数综合的子结构方法,推导了基于频响函数子结构的导纳灵敏度,得到了舱筏隔振系统的振动传递和声辐射结果对浮筏和基座连接点的频响函数及上、下层隔振器的刚度(阻尼)的灵敏度表达式。为克服灵敏度分析容易陷入局部最优的缺点,结合全局搜索能力较强的遗传算法,提出混合遗传算法。利用灵敏度方法,遗传算法和混合遗传算法对低频段上、下层隔振器的刚度在各个振动传递和声辐射优化目标下进行优化,并对各个优化目标下的结果进行讨论,研究了各个优化目标之间的联系和区别。讨论了流固耦合效应、外载荷激励和优化频带对优化结果的影响。数值仿真结果表明,以振动传递特性为优化目标的优化结果不能保证远场辐射声压的最优,以传递到基座的均方力最优时的结果不能保证传递功率流的最优。在优化时,需要考虑流固耦合的影响,并详细考虑不同的优化目标。混合遗传算法兼顾灵敏度分析的局部搜索能力和遗传算法的全局搜索能力,因而能够得到更优的结果,但需要更多的迭代次数。第六章,针对利用实测频响函数进行综合时的常见问题,分析了各种误差对综合结果的影响,利用矩方法研究了误差在综合过程中的传递,采用SVD滤波和分频段插值等方法对频响函数数据进行数值处理。利用以带基座圆柱壳体结构为基础的多点耦合单层隔振系统,验证了基于频响函数综合的子结构法对综合应用数值分析和实验方法得到的频响函数数据进行混合建模的正确性。实验结果表明,在进行振动传递建模时,隔振系统的多点多向耦合效应和隔振器的阻抗特性对综合结果的影响巨大。对基于频响函数综合的子结构方法在舱筏隔振系统中振动传递建模的应用进行实验验证,并分析了综合结果产生误差的原因。对设计制造的曲梁周期结构的导纳进行测试,验证了曲梁周期结构带隙的存在和周期结构建模方法的准确性。研究了曲梁周期结构在基础为弹性板的单自由度系统、两自由度系统、多点耦合单层隔振系统和舱筏隔振系统中的应用。实验结果表明,曲梁周期结构能够有效地抑制带隙内基础共振峰处的振动传递,抑制效果和结构的模态(激励点位置,测点位置和不同的频率点)密切相关。曲梁周期结构在隔振系统中的性能和所承载的质量与本身的质量之比有关。周期结构中的振动传递受到输入输出端负载的影响。对多点耦合单层隔振系统中安装曲梁周期结构前后振动传递的对比测试结果表明,安装曲梁周期结构后,基座连接点的响应在带隙内得到了平均10～15dB的衰减,壳体上的测点也得到了4～5dB的衰减。因此,曲梁周期结构为舱筏隔振系统的振动传递宽频带控制提供了一种具有重要应用前景的新思路。第七章,对本文的研究内容作了全面总结,并对下一步的研究进行了展望。更多还原

【Abstract】 Floating raft system is the key technology to isolate vibration of hosts and auxiliary machines, and reduce the structural noise of ships and submarines effectively. For the acoustic design of quiet submarines, quantitative prediction, control treatment selection and optimization of machinery noise are important factors urgently needed to find a new breakthrough in the performance of submarines. Under the support of National Defense Science Foundation for the projects“Acoustic Optimization of Floating Raft Sytem”and“Research on New Type of Active Vibration Isolators”, the support of National 973 subproject“Design of Raft with High Vibration Isolation Performance”, the paper is devoted to modeling the vibration transmission of floating raft system and resultant acoustic radiation, providing design guidelines and abatement techniques for floating raft system to achieve an optimized noise level.In chapter 1, the detailed literature reviews on complex flexible isolation system and the vibro-acoustic modeling of complex underwater cylindrical structures are summarized, both in the aspects of research objects and the modeling approaches. Some potential modeling techniques are pointed out. The vibration control means, including passive, active vibration control and broadband control by periodic structures are reviewed. Also the optimization techniques are reviewed. The difficulties about application of these methods to floating raft system are pointed out.In chapter 2, a general method for the integrated vibration transmission and acoustic modeling of floating raft system is presented. The coupled finite element/boundary element method (FE/BEM) is employed to study the vibro-acoustic behavior of the fluid-loaded base-cylindrical shell substructure. The modeling of vibration transmission from the vibrating machinery to the base structure is based on the Frequency Response Function-based (FRF-based) substructuring method. The effect of coupling between substructures on the vibration transmission of floating raft system is investigated. The influence of fluid-loading, the wave effects in the vibration isolators, the parameters of base-cylindrical shell substructure on the vibro-acoustic behavior of the floating raft system is investigated in detail. The acoustic design guidelines of base-cylindrical shell are summarized. Based on the modeling results, the vibration isolation measures, such as weighted mean-square force and velocity transmissibilities at base, power flow transmissibility, mean-square velocities and radiated power transmissibilities on surface of cylindrical shell and mean-square pressure transmissibility at far-field are advanced. The relationship between the performance indices of vibration isolation and those of acoustic radiation is studied. The equivalent substitute for measuring the performance of suppressing sound radiation in the far-field is advanced.In chapter 3, for suppressing the effects of resonances of foundation that significantly increase the force transmissibility and degrade the isolation performance, periodic structure, a passive band-filter vibration isolation device is developed by using its band gaps, in which waves are effectively attenuated. A curved beam periodic structure possesses of broad low frequency band gap has been designed by using the curved beam, which has the characteristic of coupled radial-tangential stiffness and has the potential of conversion of waves. The multi-layer curved beam periodic structure is composed of rigid plates and curved beams. Based on Flugge’s theory, the six-order coupled differential equations are derived to describe the in-plane motion of curved beam, the dispersion relationships and the six wave components that propagate in curved beam are obtained. The wave approach is employed to study the wave propagation, reflection and transmission in coupled curved beam and semi-infinite straight beam, the semi-infinite curved beam with multiple vibration isolation masses, the coupled masses and finite curved beams. The simulation results demonstrate that, for a given incident extensional or flexural wave, the reflected and transmitted waves contain both kinds of waves. In order to simplify the design process of curved beam periodic structure, the equivalent m-k model is developed. The transfer matrice invariant method and the wave vector approach are employed to analyze the band gap and the driving-point and transfer mobilities of curved beam periodic structure, respectively. The simulation results verify the feasibility of obtaining broad low frequency band by using the curved beam. The transmission matrix method is used to study the dynamics of curved beam periodic structure in one DOF system, two DOFs system with flexible plate as foundations and the floating raft system. Numerical simulation results have demonstrated that by use of periodic structure, the vibration transmission at resonances of bases and isolators is reduced, and the radiation of the foundation plate/shell at resonances is suppressed. Finally, the design guidelines of designing curved beam periodic structure in a given floating raft system are summarized.In chapter 4, to improve the low frequency vibration isolation performance of the vibration source-mounts-receiver (SMR) system and suppress the resultant sound radiation, the multi-channel active vibration isolation is employed. Numerical simulation of vibration control of a submerged base-cylindrical shell substructure with active vibration isolation from a vibration flexible plate is presented. The adaptive multi-channel control based on the filtered-x least mean squares (FxLMS) algorithm is used in the active vibration isolation to reduce the acceleration responses of all the connecting points on the bases. The sound radiation with/without control is studied by the dynamic model of the base-cylindrical shell substructure. The relationship between active vibration isolation and the resultant sound radiation is investigated in the time-domain. Numerical results have demonstrated that suppression of vibration on the bases leads to attenuation of sound radiation in the far-field induced by the radial displacement dominant mode of the shell. The performance of control is influenced by the coupling between control channels and related to the structural vibration modes. An experimental system, including a vibration plate, four active vibration isolators and a fluid-loaded plate is established to investigate the role of the proposed active vibration isolation in suppressing vibration transmission as well as underwater sound radiation. The exciting frequency is chosen to be nearly equal to a natural frequency of the coupled system to control the resonance of the fluid-loaded plate. The measured results show that the proposed active isolation is effective.In chapter 5, by using the FRF-based substructuring formulation, the expressions of design sensitivity analysis (SA) in terms of the partial derivatives of the physical parameters as well as FRFs of substructures are developed. In order to overcome the shortcomings of SA that may be trapped in a local optimum, the hybrid genetic algorithm (HGA) involving the FRF-based substructuring SA and the genetic algorithm (GA) is developed. To improve the performance at low frequencies, the proposed optimal schemes are employed to determine the optimal stiffness of the upper and lower isolators under five different objective functions concerning both vibration transmission and acoustic radiation. The influence of different objective functions, fluid-loading, the optimized frequency band and the source properties on the optimized results is studied. The optimized results demonstrate that some of the objective functions are equivalent to each other and can be replaced by each other. This investigation reveals that the optimized results for reducing vibration transmission to the base is not necessarily the optimized results for suppressing the sound radiation to the far-field. Thus, it should take into account of fluid-structure interaction and take comprehensive consideration of different vibration or acoustic objectives in the design stage. The numerical results also show that HGA possesses the merits of local search ability of SA and the strong global search ability of GA. Compared with SA and GA, however, HGA requires more evaluation of objective functions in each iteration step and as a result is not computationally efficient.In chapter 6, to improve the modeling accuracy of FRF-based substructuring method by using actual measured data, effects of various commonly encountered errors and noise of test data on the modeling results are investigated; propagation of uncertainties of FRFs through FRF-based substructuring is quantified based on an analytical approximation using static moment method; and filters constructed by the SVD approach and piecewise linear interpolation method are used to condition the FRF datas. An experiment to validate the effectiveness of the developed FRF-based substructuring method in modeling isolation system composed of flexible raft and base-cylindrical shell connected through multiple isolators is carried out. The experimental results demonstrate that it should take into account of the wave effects of isolators and the coupling between different degrees of freedom (DOFs). The applicability of FRF-based substructuring method in modeling vibration transmission in floating raft system is verified and the modeling errors are analysed. The experiment of detecting the band gap of designed curved beam periodic structure by measuring driving-point and transfer mobilities is carried out. The experimental results verify the accurancy of the proposed methods in dynamic modeling. The comparative trials of one DOF system, two DOFs system with flexible plate as foundations, a single-layer vibration isolation system connected through multiple isolators and the floating raft system with/without curved beam periodic structure are carried out. The experimental simulation results have demonstrated that by use of periodic structure, the vibration transmission at resonances of bases is reduced and the radiation of the foundation plate/shell at resonances is suppressed. The suppression is related to the structural vibration modes and dependent on the tested points and the frequencies. The modeling results also show that the performance of periodic structure is influenced by the mass ratio of the masses itself to the loaded masses. The vibration transmission in periodic structure is determined by the impedance loading on the input/output end. For the single-layer vibration isolation system connected through multiple isolators with proposed curved beam periodic structure, the experimental results show that responses on both the bases and the surface of the cylindrical shell are attenuated in the band gap of periodic structure. An average attenuation of 10~15dB on the bases and 4~5dB on the shell are obtained. Thus curved beam periodic structure offers a new means for controlling vibration tranmission in broad frequency band.Finally, the research and the contributions are summarized and some problems to be further studied are pointed out.更多还原