Design Method Of Scale Model For Large Airship Keel

Large semi-rigid airship is one of the critical points in developing low-speed near space aerocraft presently. To reduce structural weight and meet the requirement of stiffness and strength, its keel is generally made of composite material which has high ratios of stiffness and strength to mass. For the ground test of large composite keel structure, it’s used to utilize scale modeling test instead of full-scale modeling test. The linear elastic laminated rigid framed structure is taken as the object in this paper. The design method of scale model relating to the static response and dynamic characteristics is studied on the basis of similitude theory, whose results are applied to design the scale model of the keel. The main research contents are as follows:Some concepts relating to similitude theory and modeling test are introduced according to the three similitude theorems. The derivation process of similarity relationships based on dimension analysis and the analysis of mathematical model is elaborated. And the method of dealing with partial similarity is discussed.On basis of the theory of thin-walled beams, the displacement expression of closed cross-section thin- walled beam is established. The analytical stiffness equation of the thin- walled composite beams is derived, and it’s verified through the numerical example.The similarity relationships of linear elastic isotropic rigid framed structure is found based on dimension analysis. By developing the analysis of mathematical model combined with finite element method, the similarity relationships of linear elastic composite rigid framed structure is found. Two kinds of partial similarity factors are analyzed, and the comparison between the two kinds of method developing similarity relationships is studied.According to the similarity relationships derived by analysis of mathematical model, the 1/5 scale composite model of a keel structure is designed. Finally, the model is verified by use of FEA software MSC.Patran/Nastran.To sum up, design method of scale model for linear elastic composite rigid framed structure is developed in this dissertation. The result is successfully applied to the scale model design for the keel structure. The method can be extensively used to design scale model for other kinds of large scale keel structures.