轴-壳体系统耦合振动的建模与分析

Modeling and analysis for coupled vibration of a shaft-hull system

耦合振动建模与分析是振动控制的基础。针对末端带有集中质量的轴与加筋壳体的耦合系统,分别利用解析法和有限元法计算轴系导纳和加筋壳体导纳,并将艉轴承与推力轴承作为子结构连接单元,通过频响函数综合进行模型合成,得到整个系统的频域描述模型。在此模型基础上,分析了系统振动固有特性及其随轴承刚度的变化规律,并讨论在轴上实施纵向振动控制的可行性。结果表明,推力轴承刚度改变轴系纵振频率,对纵振能量传递有明显影响;轴系纵向振动不仅会引起壳体纵向共振,还会引起壳体弯曲振动,形成轴-壳体纵横耦合模态;轴的纵向振动控制可以减小耦合系统振动。

Modeling of coupled vibration is a base for vibration control. In one modeling process, frequency response functions （FRFs） of a shaft with a mass at one of its ends were calculated with the analytical method while FRFs of a reinforced hull structure were calculated with the finite element method （FEM）. A frequency description model of this shaft-hull coupled system was obtained with synthesis of FRFs of the shaft and the hull structure where bearings were regarded as link units between substructures. In terms of the synthesized model, its natural vibration characteristics and their variation with parameters of the thrust bearing were analyzed and the feasibility of performing longitudinal vibration control on the shaft was discussed as well. Analysis results showed that the variation of the thrust bearing stiffness changes the longitudinal vibration frequencies of the shafting system and thus has a significant influence on vibration transmission; the longitudinal vibration of the shaft causes not only the longitudinal resonance of the hull structure but also the lateral vibration in the shaft-hull coupled system; furthermore, the longitudinal vibration control of the shaft can reduce the vibration of the coupled system.