Experimental and numerical vibration analyses of a stiffened panel

The publication concentrates on studying the vibration behaviour of onespecially built quite simple stiffened pan el. The finite element method (FEM) is employed for the computational analysis. The example structure is modelled using three different approaches. The main difference between these approaches is the way the stiffeners are modelled, i.e. by using either stiffener elements or flat shell elements. To estimate the errors in the numerical analysis, three element meshes on different levels of accuracy are used in each approach. The resulting natural frequencies and mode shapes are compared within one modelling approach as well as with selected calculated reference results, which are assumed to be accurate enough. Additional information for the evaluation of computational analyses is gained by performing modal testing of the actual panel. The results of this experimental stage are the resonant frequencies and modes of the panel, which are compared with numerical results. To get an idea of the effect of geometrical imperfections and residual stresses on the vibration characteristics of this kind of structure, the panel is tested both in the natural post-welding state and after being straightened.