MODAL-BASED ENHANCEMENT OF INTEGRATED DESIGN OPTIMIZATION SCHEMES

The modal approach to integrated structural optimization of aircraft s tructures offers huge computational savings with acceptable loss of ac curacy. The addition of the modal option to existing full-order discre te-coordinate optimization schemes is shown in this paper to provide a very flexible design tool with improved cost effectiveness in typical aerospace design cases. Extensive changes in the modal-based formulat ion are introduced to expand the scope of its applicability, particula rly in the static disciplines. Fictitious masses are used to account f or local effects caused by concentrated loads. High-order modal pertur bations are introduced for improved accuracy with large move limits. A n optional hybrid approach allo cvs the use of modal aeroelastic trim with subsequent discrete-coordinate stress/strain analysis. The new fo rmulation includes the necessary sensitivity analysis for an adequate application in conjunction with the modeling tools of the discrete app roach. Tradeoff studies with a realistic generic fighter aircraft mode l demonstrate the ne cv capabilities.