Nonlinear Dynamic Response Structural Optimization of a Joined-Wing Using Equivalent Static Loads

Abstract

The joined-wing configuration that was published by Wolkovich in 1986 has been studied by many researchers. The joined-wing airplane is defined as an airplane that incorporates tandem wings arranged to form diamond shapes in both top and front views. The joined-wing can lead to increased aerodynamic performances and reduction of the structural weight. However, the joined-wing has high geometric nonlinearity under the gust load. The gust load acts as a dynamic load. Therefore, nonlinear dynamic behavior of a joined-wing should be considered in structural optimization. In previous researches, linear dynamic response optimization and nonlinear static responses optimization are performed. It is well known that conventional nonlinear dynamic response optimization is extremely expensive. Therefore, in this research, the nonlinear dynamic response optimization of a joined-wing is carried out by using equivalent static loads. The concept of equivalent static loads is expanded and newly proposed for nonlinear dynamic response optimization. Equivalent static loads are the loads sets which generate the same response field in linear static analysis as that from nonlinear dynamic analysis. Therefore, nonlinear response optimization can be conducted by repeated use of linear response optimization. Because the method is gradient based optimization, the exact optimum solution can be obtained. The procedure for nonlinear dynamic response optimization of a joined-wing using equivalent static loads is explained and the optimum results are described.