21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-4.7.2

STRUCTURAL OPTIMIZATION WITH STATIC CONSTRAINTS USING EXPANDABLE MODAL BASIS

Karpel M., Moulin B.
Technion - Israel Institute of Technology, Israel

Keywords: structural optimization, static constraints, expandable modal basis

The modal-based approach to aeroelastic optimization with static aeroelastic and stress constraints is extended by adding static deflection modes to the modal basis. The optimization process starts with a reduced-size model that uses low frequency normal modes of the baseline structure as fixed generalized coordinated. Static deformations in design cases calculated along the optimization path contain local modal-perturbation information that is not included in the modal basis. These modes are orthogonalized with respect to the modal basis and added as new generalized coordinates. With this expansion, the modal-based optimization becomes more efficient and it convergences to the exact optimal design. Numerical example with realistic fighter-aircraft model demonstrates practical applications with CPU speed-up factors of 510, compared to the regular discrete-coordinate approach, with negligible loss of accuracy.

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