Because the current airplane structures become more and more complex, it is impossible to build an exact analytical model for the real structures. So, we have to choose an approximate model such as finite element method to know the vibration characteristics. But the finite element modeling of a real 3-D wing frame is difficult and time-consuming task. Thus equivalent modeling methods are commonly used in the practical design process. In this study, the various modeling techniques for beams and concentrated masses have been devised to build up the effective equivalent structural dynamic model of wing.
The equivalent structural modeling technique is composed of equivalent mass modeling and equivalent stiffness modeling. The equivalent stiffness modeling technique is mainly focused in this study. The plate wing and various box beam wings are modeled using the equivalent beam model. Dynamic and flutter analyses using both the 3D FEM model and equivalent model are performed and the equivalent beam model represent the dynamic characteristic of 3D FEM model very well.
Generally, there are two major benefits of equivalent beam modeling method; the modeling process is very simple and the accurate and easy modification can be obtained using compared with GVT(Ground Vibration Test) results.