薄壁圆柱壳体的模态特性与隔振系统主被动控制策略

发布时间：2018-04-04 10:40

本文选题：圆柱壳体　切入点：导纳　出处：《山东大学》2014年硕士论文

【摘要】：针对薄壁圆柱壳体内安装动力机械后的隔振设计及结构声控制问题,基于经典薄壳理论,研究了两端剪力薄膜支撑各向同性圆柱壳体结构的模态特性。采用模态叠加法对复合激励下两端剪力薄膜支撑各向同性圆柱壳体结构的点导纳表达式进行了详细推导。结合功率流理论,运用子结构导纳法分析了圆柱壳体内动力机械隔振系统的能量传递特性,着重分析了隔振器斜置安装角对隔振效果的影响,探究了动力机械横向-横摇耦合振动的去耦条件。为改善被动隔振措施低频域的控制效果,建立了前馈自适应控制主被动支承一体的混合隔振系统模型。在频域中引入了考虑作动器输出约束的泄漏算法,对比分析了约束算法控制、纯被动措施及作动器理想无约束输出条件下的隔振效果。并对混合隔振系统中主被动支承斜置安装后产生的不利影响及原因和改进措施进行了论述。最后,采用锤击激励法对两端开口自由悬挂圆柱壳体结构进行了试验模态测试分析,将试验获取的模态参数同有限元分析结果进行了对比。具体内容如下：通过“标准”方法,建立了一般壳体结构的振动微分方程,基于不同的位移-应变关系,导出了三种常用薄壳理论(Donnell-Mushtari理论、Goldenveizer-Novozhilov理论、Flugge-Byrne-Lur'ye理论)下的圆柱壳体自由振动微分方程。针对工程实际中常见的两端剪力薄膜支撑边界条件,采用解析法求得了模态特征表达式。结合数值算例,将理论计算结果同商业有限元软件分析结果进行了比较,确定了不同几何参数条件下,各薄壳理论的计算精度及适用范围。研究发现：在多种长径比及厚径比条件下,采用Goldenveizer-Novozhilov薄壳理论计算的结果相对精度最高。基于模态叠加原理,考虑圆柱壳体非径向振动惯性项的贡献,同时计及正、余弦模态响应,推导了两端剪力薄膜支承各向同性圆柱壳体结构在简谐集中力与集中力矩激励下的力导纳、力矩导纳和耦合导纳的完整解析表达式。研究发现：圆柱壳体运动方程中的非径向振动惯性项对各阶模态及导纳幅频的预估精度影响显著；力导纳和力矩导纳的实部恒正,耦合导纳实部具有可负性规律,其负值实部的出现依赖于轴向节线参数的取值以及激励与响应点的选取位置,可为壳体结构的减振降噪工作提供一种潜在手段,即通过合理布置外施载荷的相对大小、位置来降低壳体结构在某个频率范围的振动功率级。建立了由多向扰动(包含力、力矩激励成分)振源、斜置分布参数弹性支承、圆柱壳体基础组成的隔振系统解析形式波动模型。运用子结构导纳法对隔振系统的动态特性传递方程进行了理论推导,以功率流为价值函数对系统的耦合振动机理及隔振效果进行了探究与分析。数值仿真表明：隔振器的分布参数特性及与基础模态的耦合交互使得高频域系统功率流下降趋势变缓,影响高频隔振设计可靠性；适度增大隔振器斜置倾角,可使系统的三向刚体模态波峰聚集在较窄的频带范围内,进而降低传递到基础的功率流幅值,收到更好的隔振效果；可通过配置合适的斜置隔振倾角,获取动力机械独立的横向及横摇振动模态。建立了由多向扰动振源、斜置主被动隔振支承及柔性圆柱壳体基础组成的自适应前馈控制混合隔振系统解析模型。在频域中,引入计及作动器输出约束的泄漏算法,依据导纳矩阵理论推导了总体系统的动态特性传递方程。以传递到圆柱壳基础的总功率最小、径向力最小、径向速度响应最小、径向功率流最小及径向速度与径向力加权和最小为控制策略,分析约束算法在作动器总体输出约束及单个作动器输出约束情况下对系统隔振效果的影响。数值仿真表明：泄漏约束算法能收到良好的主动控制力约束效果,并可有效抑制最小化径向力、最小化径向速度、最小化径向功率流及最小化径向速度与径向力加权和策略下的“功率循环”现象发生。采用径向速度最小化策略会改变壳体基础的边界条件配置,使得功率流谱中基础模态峰值右移。当主被动隔振支承倾斜安装时,虽然可以收到更好的被动隔振效果,却对主动隔振情况产生了不利影响。在各种控制策略下,斜置安装隔振支承时传递到壳体基础的总功率流均明显高于隔振支承平置安装情况,可通过单独安装沿壳体基础面内、面外两个维度的作动器来克服这种问题。搭建了柔性圆柱壳体结构振动模态试验测试平台,采用锤击激励法对两端自由弹性悬挂薄壁开口圆柱壳体的振动特性进行了试验研究,将所得模态参数同有限元法分析结果进行了对比,两者吻合程度良好。分析了产生误差和影响测试精度的因素。
[Abstract]:Based on the classical thin shell theory , the modal characteristics of the structure of the isotropic cylindrical shell supported by shear thin films at both ends are studied in detail . Based on the classical thin shell theory , the energy transfer characteristics of the dynamic mechanical vibration isolation system in the cylindrical shell are studied by using the modal superposition method .

By means of " standard " method , the differential equation of vibration differential equation of general case structure is established . Based on different displacement - strain relations , the differential equation of free vibration of cylindrical shell under three common thin - shell theory ( Donnell - Birtari theory , Goldenveizer - Novozhilov theory , Flugge - Byrne - Lur ' ye theory ) is derived .

Based on the principle of modal superposition , considering the contribution of the non - radial vibration inertia term of the cylindrical shell , the full analytical expression of the force admittance , moment admittance and coupling admittance of the isotropic cylindrical shell structure under the excitation of harmonic concentration and concentrated torque is deduced .
The real part constant positive and coupled admittance real part of the force admittance and moment admittance has a negative law . The occurrence of the negative value real part depends on the value of the axial joint parameter and the selection position of the excitation and response points , which can provide a potential means for damping and noise reduction of the shell structure , namely , the vibration power level of the shell structure in a certain frequency range is reduced by reasonably arranging the relative size and position of the external application load .

The analytical form fluctuation model of vibration isolation system composed of multi - directional disturbance ( including force , moment excitation component ) , oblique distribution parameter elastic support and cylindrical shell foundation is established . The dynamic characteristic transfer equation of vibration isolation system is theoretically deduced by using substructure admittance method .
the inclined inclination angle of the vibration isolator can be moderately increased , the three - way rigid body mode peak of the system can be gathered in a narrow frequency band range , so that the power flow amplitude transmitted to the foundation is reduced , and better vibration isolation effect is received ;
The independent transverse and roll vibration modes of the power machine can be obtained by arranging the proper inclined vibration isolation angle .

Based on the admittance matrix theory , the dynamic characteristic transfer equation of the whole system is derived . The dynamic characteristic transfer equation of the whole system is derived from the theory of the admittance matrix . It is shown that the leakage restraint algorithm can receive good active control force and minimize radial force , minimize radial power flow and minimize radial force and radial force .

The vibration modal test platform of flexible cylindrical shell structure was built , and the vibration characteristics of the thin - walled open cylindrical shell with two ends were experimentally studied by hammering excitation method . The obtained modal parameters were compared with the results of finite element method .

【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB535

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