大尺度刚柔组合飞艇结构的静动态力学性能分析

STATIC AND DYNAMIC MECHANICS ANALYSIS FOR A LARGE-SCALE RIGIDITY-FLEXIBILITY AIRSHIP STRUCTURE

刚柔组合体的大变形行为和复杂连接接触给飞艇大尺度结构的力学分析、设计和制造带来了挑战。该文选择德国先进的Zeppelin NT飞艇作为研究对象,飞艇结构由内部骨架与外部蒙皮连接而成,是典型的刚柔组合体结构。飞艇骨架的主要结构单元为桁架梁,若采用精细化模型,建模工作量大,因此通过对代表性桁架梁进行精细化分析,得出梁的截面力学参数,建立了等效简化梁模型,使得计算成本大为降低。为了验证有限元方法对柔性结构模态分析的适用性,推导了无限长圆柱形膜结构的二维振动模态频率理论解,并与有限元模拟得到的数值结果进行比较,两者误差较小。将蒙皮振动引起周围空气运动的附加质量引入有限元分析模型,得到蒙皮与骨架结构合理的模态振动频率。该文建立了大尺度刚柔组合飞艇结构的力学分析方法,并验证了方法的可行性。

There is a large deformation and complex contact in a large scale rigidity-flexibility airship structure, which brings a great challenge to the structural analysis, design and manufacture. The Zeppelin NT airship is introduced, which is one kind of advanced German airships. The airship structure is made up with the internal frame and outer skin, which is a typical rigidity-flexibility structure. The framework is mainly composed of the truss beams. Since it is a large scale structure, the FEM modeling is a huge work for the detail analysis. Therefore, the simplified modeling is required. The fine analysis is carried out for the main beam structure to obtain the mechanics parameters of a beam section, and then the complex beam structure model is replaced by a simplified equivalent beam model. In order to verify the applicability of FEM in flexible-structure analysis, the theoretical dynamic analysis is provided for an infinite length cylindrical membrane structure in two dimensional vibrations. The analyzed frequency values agree well with the simulation results by FEM. The modal frequencies of the skin structure of an airship obtained by FEM are a little bit larger than the empirical results. The reason is that a large size skin vibration may cause the movement of surrounding air, so the added mass caused by air movement needs to be considered. After implementing the added mass into FEM model, the reasonable vibration frequencies of the skin-structure model are achieved. Through studying the mechanics capability of an airship, the simulation and analysis method are developed, and the feasibility of the method is also verified.