当前船舶机舱局部动力分析中，以集中质量点模拟主机不能准确反映主机振动对双层底的影响，而建立详细的主机实体有限元模型则其自由度数目庞大、计算成本过高。为解决此类问题，在主机-双层底耦合系统振动分析中引入模态综合法。分别以主机、双层底有限元模型为对象，通过MATLAB编程实现主机和双层底的模态综合，可获得阶数显著降低的主机-双层底耦合系统质量矩阵、刚度矩阵。计算结果表明，固定界面模态综合法的引入不仅能够准确地反映主机-双层底的耦合振动特性，解决主机详细建模带来的计算成本过高的问题，而且还可以方便地应对双层底结构的修改，避免主机模态的重复计算。%An approach for analyzing the ship’s engine and double-layer bottom coupled vibration was presented using the component mode synthesis (CMS) method. In traditional modal analysis of this coupled system, simplifying the engine as a concentrated mass can’t reflect the effects of engine vibration, and a complete 3D finite element model may drastically increase computational cost. In this paper, the CMS method was applied to deal with these problems. The modal synthesis of the engine and the double-layer bottom was accomplished by MATLAB, and the order-reduced coupled system matrices were obtained. Solutions of an example illustrate that this approach can effectively reduce the cost of computation and retain the vibration information of the coupled system. Also, the solutions demonstrate the advantages of this approach that only the mode information of the modified substructure need to be computed when the substructure is modified.
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