Stress considerations in reduced-size aeroelastic optimization

Abstract

The modal approach, which is normally used in analysis and optimization with dynamic aeroelastic considerations, is extended here to deal with static aeroelastic maneuver trim equations, loads, and stresses. Reduced-size static equilibrium equations, where a subset of low-frequency vibration modes of a baseline structure is used as generalized coordinates, are formulated such that they can be used for modified structures without changing the coordinates. These expressions and their derivatives with respect to structural design variables are investigated in comparison with full-size finite element solutions. A new method, which uses modal stress perturbations of the baseline structure to predict stresses in the modified ones, is developed. The modal perturbation approach facilitates high-accuracy computations of stress sensitivities without increasing the model size. The presented formulation facilitates an efficient inclusion of stress and load considerations in on-line aeroservoelastic optimal design schemes