Optimization of a wing structure for gust response and aileron effectiveness

Reliability-based weight optimization of a generic, fighter-like wing structure is conducted for gust response and aileron effectiveness constraints. The formulation accounts for parametric uncertainties in these aeroelastic response quantities. Reliability indices measure the probability of satisfying each constraint, and a preliminary design procedure is developed in which constraints are enforced on these indices. This framework integrates ASTROS for structural and loads analysis, object-oriented MATLAB tools for reliability analysis, and DOT for optimization and most probable point estimation. The reliability analysis algorithm takes advantage of adaptive nonlinear approximations to compensate for nonlinearity of the failure surfaces. The wing structure is modeled with finite elements, each of which is assumed to have random thickness of known standard deviation. Youngʹʹs modulus of the wing skin material is also assumed to be random. Mean thickness values are taken as design variables. Linear unsteady aerodynamics is used to estimate frequency response functions caused by continuous gust loads. Reliability index constraints are enforced for gust-induced bending moment and shear at the wingʹʹs root, and also for aileron effectiveness. Redistribution of structural mass by the optimizer produces designs with improved aeroelastic performance reliability and relatively small weight penalties.