【作者】 严谨；

【导师】 刘土光； 李天匀；

【作者基本信息】 华中科技大学 ， 船舶与海洋结构物设计制造， 2006， 博士

【摘要】 本文的研究工作是“十五”预研基金资助项目“结构声传递和声辐射计算(2)”(项目编号:10105010204)的一部分。本文采用周期结构理论和振动能量流的方法,对水下无限长周期环肋加强圆柱壳、环肋和舱壁双周期加强圆柱壳以及粘弹性复合圆柱壳等结构模型的振动能量流和声辐射进行了理论分析和相关的试验研究,系统探讨了环肋、舱壁、阻尼层以及重要结构参数对圆柱壳结构振动声性能的影响。分析模型接近工程实际结构,可为研制出结构振动响应级小、辐射噪声水平低的新型高性能潜艇提供可靠实用的计算方法。文中首先以一流场中无限长周期环肋加强圆柱壳受激振动的能量流及声辐射为研究对象。分析中,将周期结构理论和振动能量流理论引入到周期加肋圆柱壳—流场耦合系统,分别用Flügge方程和Helmholtz方程描述壳体及声场的波运动,并利用圆柱壳—流场的耦合条件,把环肋对圆柱壳振动的影响用环肋对壳体的作用力和力矩代替,采用空间简谐分析方法推导周期耦合系统在外载荷作用力下的响应,根据壳体微元应力、应变关系推得壳体中的各内力和力矩,并最后推得外力输入到圆柱壳的能量流、加肋圆柱壳内力传播的能量流以及壳体辐射线功率和声功率的计算公式。在数值分析中,针对不同频率、不同周向波数、不同结构阻尼和不同肋骨参数,计算了周期环肋加强圆柱壳的输入能量流、传播能量流以及声辐射,并同真空加肋圆柱壳和充液加肋圆柱壳的结果做了比较。接着,将研究对象扩展到双周期耦合系统,研究了流场中无限长环肋和舱壁双周期加强圆柱壳受外激励的振动能量流和声辐射。与肋骨的处理相似,把舱壁对圆柱壳振动的影响用舱壁对壳体的作用力和力矩代替,同样采用空间简谐分析方法推导双周期耦合系统在外载荷作用力下的响应,根据壳体微元应力、应变关系推得壳体中的各内力和力矩,计算了不同频率、不同周向波数、不同结构阻尼等情况下环肋和舱壁双周期加强圆柱壳的输入能量流、传播能量流以及声辐射,着重探讨了舱壁参数的影响。鉴于粘弹性阻尼材料在减振降噪中的广泛应用,进而分析了表面敷设粘弹性阻尼层的圆柱壳—流场耦合系统的振动能量流和声辐射。利用Flügge壳体理论和Helmholtz方程导出了流场中自由阻尼复合壳的振动微分方程,用复模量形式计及基壳和粘弹性阻尼材料的损耗因子以及流固耦合作用,采用波传播分析方法求解,着重探讨了粘弹性阻尼层的影响。在理论方面,本文的研究丰富和发展了周期结构理论和振动能量流方法,首次采用空间简谐分析方法研究了水下周期及双周期加强圆柱壳耦合系统的振动能量流和声辐射,并基于波传播方法,对自由阻尼圆柱壳在流场中的振动和声辐射特性进行了探讨。在试验方面,设计了周期加肋圆柱壳结构模型,对流场中周期环肋加强圆柱壳的输入能量流和辐射声压的进行了测量,通过测量结果与理论结果的对比,证实了本文理论分析的合理性。结构中的振动及噪声,以波的形式向远处传播,其本质是振动能量流的传播,而辐射声功率等于结构输入的能量流扣除在传播过程中阻尼损耗能量的剩余部分;另外,低频时无限结构的响应近似地是相应有限结构响应的平均值,随着频率增高,有限结构与相应无限结构的响应趋于一致。因而,本文的研究工作对指导潜艇的减振降噪具有较大意义。更多还原

【Abstract】 The work of this paper is one part of the research project“Calculation of Structural Sound Transmission and Sound Radiation of Submerged Structure”which was supported by foundation of national key project in“the State 10th Five-Year Plan”(Contract No.10105010204). Using periodic structure theory and vibrational power flow method, the characteristics of vibrational power flow and sound radiation in an infinite submerged periodic ring-stiffened cylindrical shell, a submerged infinite cylindrical shell reinforced by doubly periodic supports of rings and bulkheads, a submerged infinite unconstrained viscoelastic cylindrical shell, are studied by both analysis and experiment, respectively. The influences of different structural parameters such as ring, bulkhead, viscoelastic damping layer, etc, are discussed detailedly. The analytic model is close to engineering practice, and it will provide reliable calculated method for the design of new type and high performance submarine with small vibrational response and low radiated noise level.First, vibrational power flow and sound radiation in an infinite submerged periodic ring-stiffened cylindrical shell are considered. Periodic structure theory and vibrational power flow method are introduced into the cylindrical shell-fluid coupled system. The harmonic motion of the shell and the pressure field in the fluid are described by Flügge shell equations and Helmholtz equation, respectively, and the coupling condition on the outer surface of the shell wall is considered. The influences of the ring are replaced by the exerting forces and moments on the shell. Space-harmonic analysis is used to deduce the responses of the coupled system excited by a driving force. The forces and moments of the shell are derived by infinitesimal stress and stress-strain relationship, and then the calculated formulas of input power flow, propagation power flow as well as sound radiation can be obtained. In the numerical calculation, the influences of frequency, circumferential order number, structural damping and ring parameters on the results are discussed, respectively, and the comparison are made with those of vacuum stiffened shell and fluid-filled stiffened shell.Then, the researched object is extend to doubly periodic coupled system, and vibrational power flow and sound radiation in a submerged cylindrical shell reinforced by doubly periodic supports of rings and bulkheads are investigated. The dispose of the bulkhead is similar to that of the ring, and space-harmonic analysis is used once again to deduce the responses of the doubly periodic coupled system. The influences of deferent parameters, especially bulkhead parameters on the results are discussed, respectively.Due to the extensive application of viscoelastic damping material, vibrational power flow and sound radiation in a submerged infinite unconstrained viscoelastic cylindrical shell are also studied. The harmonic motion of the shell and the pressure field in the fluid are described by Flügge shell equations and Helmholtz equation, respectively. The damping characteristics are considered by complex modulus method, and the solutions are obtained by wave propagation approach. Among the numerical results, the discussions concentrate on the influences of viscoelastic damping layer.The theory of periodic structure and the method of power flow have been developed. Space-harmonic analysis method is firstly employed to analysis vibrational power flow and sound radiation in the submerged periodic and doubly periodic coupled system. The characteristics of vibrational power flow and sound radiation are also investigated for a viscoelastic cylindrical shell immersed in the fluid. In experiment, the model of a periodic ring-stiffened cylindrical shell is designed. Both the power flow into a cylindrical shell immersed in the fluid and the radiated sound pressure of the model underwater are measured. Comparison between experiment results and theoretical predictions verifies the validity of the theoretical method in this paper.The vibration and noise in the structure will propagate to a far location by means of waves, the essence of which is the propagation of power flow, and the radiated sound power is equal to the residual of loss energy caused by damping deducted from the input power flow. In addition, the response of unbounded structure is approximately equal to the average of that of bounded structure at low frequency, and the responses of two kinds of structures drive to coincidence with the increasing of frequency. So, the results presented here will be helpful to reduce vibration and noise of submarine and other structure.更多还原