STRESS CONSIDERATIONS IN REDUCED-SIZE AEROELASTIC OPTIMIZATION

The modal approach, which is normally used in analysis and optimizatio n with dynamic aeroelastic considerations, is extended here to deal wi th static aeroelastic maneuver trim equations, loads, and stresses. Re duced-size static equilibrium equations, where a subset of low-frequen cy vibration modes of a baseline structure is used as generalized coor dinates, are formulated such that they can be used for modified struct ures without changing the coordinates. These expressions and their der ivatives with respect to structural design variables are investigated in comparison with full-size finite element solutions. A new method, w hich uses modal stress perturbations of the baseline structure to pred ict stresses in the modified ones, is developed. The modal perturbatio n approach facilitates high-accuracy computations of stress sensitivit ies without increasing the model size. The presented formulation facil itates an efficient inclusion of stress and load considerations in on- line aeroservoelastic optimal design schemes.