Multi-Objective Evolutionary Structural Optimization Using Combined Static/Dynamic Control Parameters. Delivery Order 0007; Interim rept. 12 Sep 2006-20 Mar 2007

摘要

A thermal protection system (TPS) is responsible for protecting a spacecraft's components from melting due to high reentry temperatures. In the design of TPS, both maximum thermal stress and minimum natural frequency must be considered due to the combined thermoacoustic environment inherent in high- speed vehicle applications. A multiobjective structural optimization method for the three-dimensional acreage TPS design is developed using an evolutionary structural optimization (ESO) algorithm. The static control parameter used to find the optimum in minimum thermal stress design is modified to address an irregular mode-switching phenomenon, as well as to improve the modal stiffness in dynamic analysis. Two objectives are optimized simultaneously, namely, the maximization of fundamental natural frequency and the minimization of maximum thermal stress. The proposed modified control parameter is demonstrated in the design of a metallic TPS using the method of weighted objectives. The results are then compared with the conventional ESO sensitivity approach. This work concludes by applying the methodology which makes use of both topology and shape optimization in the design of an acreage TPS.