Flutter Predictions Of Damaged Wings




			FLUTTER PREDICTIONS OF DAMAGED WINGS Ronald L. Hinrichsen, NCSA/UIUC Greg Czarnecki, USAF 46th Test Wing This file is available for download in *.pdf* format. Click here Research Objectives: To use state of the art nonlinear dynamic explicit time integration finite element code (LSDYNA3D) to predict the flutter resulting from damage due to hydrodynamic ram or missile impact. To evaluate the predictions made by the code and make recommendations for its improvement. To evaluate methodologies for effectively coupling the flow field around the wing with the structure of the wing. Methodology: The methodology of this research was to model the wing using the Lagrangian perspective coupled with a boundary element method for modeling the flow field around the wing. The boundary element method used in this work is consistent with several "paneling methods" which can be used for inviscid, incompressible flows. The wing model was initially loaded with the airloads along with g-loads. Then at a selected time in the simulation, a section of structure was instantaneously removed to simulate the damage resulting from a detonation or impact. The simulation was allowed to continue and resulting stresses and wing displacements were observed. *Figure 1. Sample Wing Flutter Model Before Damage* Results: The LSDYNA3D code was found to be effective in coupling the structure with the boundary element method flow field model. The code was also robust enough to handle the instantaneous damage. Significance: This research is significant as it points the way to an effective and efficient method for predicting the flutter resulting from the damage resulting from detonation or impact of a missile or AAA threat on an aircraft wing. This work will be used in the future to assist the 46th Test Wing in designing and controlling a dynamic ground test to more realistically reproduce what actually happens in flight. *Figure 2. Von Mises Stress Contours Before Damage* *Figure 3. VonMises Stress Contours Immediately After Damage* *Figure 4. Stress And Displacements 0.37 Sec After Damage* *Figure 5. Wing Tip Displacements* *Figure 6. VonMises Stresses Near Damage Location*