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

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.