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近几年来,在一些先进的造船工业国家,部件模态综合法在船体结构动态计算中已开始应用。通过将整船分成上层建筑、桅杆、船体梁等若干部分,分别计算各部件的动态特性然后加以综合,可得到整船的结构动态特性。这就有效地解决了计算机容量不足的问题,使绝大部分拥有中小型计算机的企业对这类大型复杂结构的动态计算成为可能。本文根据动力变换原理和超单元的模态分析,导出了一种新的动态子结构法——模态综合超单元法,克服了一般模态综合法与通用有限元法技术相结合的困难,改进了Guyan、Kuhar等人提出的静力、动力缩聚计算的精度。本文提出的模态综合超单元法是将模态综合法与阻抗匹配法结合起来的一种新的动态子结构法,在超单元的缩聚动刚度矩阵中保留了若干阶的固定对接主模态,从而保证了计算精度。在取得超单元的动态缩聚信息后,采用与有限元相同的对接步骤,得到缩聚了的、依赖于系统频率的动刚度矩阵。解此非线性特征方程,即得到所求系统的特征值。本文对非线性特征值的计算原理和步骤也作了专门阐述,这在动态子结构法中是十分关键的一步。根据本方法的计算原理,在我所国产的108计算机上建立了通用程序,并对已有精确解和试验结果的立体双层框架进行了计算考核,结果吻合良好。然后用本方法对5000吨舱口驳模型进行了计算,利用对称和反对称原理计算了具有456个自由度的驳船模型的四分之一部分,将该部分分成四个超单元,每个超单元分别由132个自由度或108个自由度的膜梁组合结构立体舱段组成,用子空间联立迭代法计算得到每个舱段的模态,加以综合后求得整船的动态特性。最后将计算结果与对该模型采用先进的模态识别试验(击锤法)及Molré干涉横向测振试验结果进行了比较,一致性也是满意的。
In recent years, in some advanced shipbuilding industry countries, the component modal synthesis method has begun to be applied in the dynamic calculation of the hull structure. By dividing the entire ship into several parts such as superstructures, masts, and hull girders, the dynamic characteristics of each component are calculated and integrated to obtain the structural dynamic characteristics of the entire ship. This effectively solves the problem of insufficient computer capacity, making it possible for most companies with small and medium-sized computers to dynamically calculate such large and complex structures. Based on the principle of dynamic transformation and modal analysis of superelements, this paper derives a new dynamic substructure method-modal integrated superelement method, which overcomes the difficulties of combining general modal synthesis method with general finite element method technique. The accuracy of static and dynamic condensation calculations proposed by Guyan and Kuhar et al. was improved. The modal synthetic superelement method proposed in this paper is a new dynamic substructure method combining modal synthesis method and impedance matching method. The fixed butt joint main modes of several orders are preserved in the superplastic dynamic stiffness matrix of the superelement. , thus ensuring the calculation accuracy. After obtaining the dynamic condensation information of the superelement, the same docking procedure as the finite element is used to obtain a condensed dynamic stiffness matrix that depends on the system frequency. Solve the nonlinear characteristic equation, that is to obtain the eigenvalues of the system. In this paper, the principle and steps of calculation of nonlinear eigenvalues are also elaborated. This is a crucial step in the dynamic substructure method. According to the calculation principle of this method, a general program was established on the 108 computers that I have made, and the calculations of the three-dimensional, two-tier framework with accurate solutions and experimental results were performed. The results were in good agreement. Then the 5,000-ton hatchway model was calculated using this method. A quarter of the 456-degree-of-freedom barge model was calculated using the principles of symmetry and anti-symmetry. The section was divided into four superelements, each The superelements are composed of 132-degree-of-freedom or 108-degree-of-freedom capsule-beam composite structures. The modalities of each chamber are calculated by using the subspace iterative iteration method, and the dynamic characteristics of the entire ship are obtained after synthesis. . Finally, the results are compared with the model using advanced modal identification test (hammer method) and Molré interferometric transverse vibration test results, and the agreement is also satisfactory.