Optimization of Aerospace Structures for Aeroelastic Response Reliability

摘要

Reliability-based optimization of a generic, fighter-like wing structure is conducted for gust response and aileron effectiveness. This work is performed within a framework that 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. Young's modulus of the wing skin material is also assumed to be random. The mean thickness values are taken as design variables. Linear unsteady aerodynamics theory is used to estimate frequency response functions due to loads induced by harmonic variations in the vertical component of the freestream velocity. Continuous gust excitation is modeled as a stationary random process that follows the von Karman turbulence spectrum. Reliability index constraints are enforced for gust-induced bending moment and shear at the wing's 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.