Normal Modes Analysis Of Flight Vehicle Structure With Contact Surface

Contact surface exist in many complex structure of aircraft, which cause the difficulty of dynamical analysis. The finite element method (FEM) of contact theory and eigenvalue computing is used in this thesis to solve the problem of natural modal analyzing aircraft structure with contact surface.The contact problems in engineering are very important but rather complicated because they deal with stress concentration, boundary nonlinear, and even material and geometric nonlinear problems. At first, the numerical approach of the FEM to solve the contact problems is researched. Then contact surface in the representative structure of the aircraft is introduced, and the appropriate contact physical model is presented. Some examples are given to testify the validity of the method.The natural modal analysis is equal to the eigenvalue computing in essence, which got from derivation of dynamical formulae. The numerical approach of computing the large-scale eigenvalue is investigated. The example is used to select feasible method to solve eigenvalue problems.The pre- force and the number of fastenings affect the natural modal is researched to get correct rules. At last, analyze the natural modal of the real aircraft structure with contact surface to verify the practicability of the method is given in the thesis.