An Optimality Criteria Approach to the Minimum Weight Design of Aircraft Structures.

摘要

The research presented in this report is both a continuation and an extension of the optimality criteria approach to structural optimization reported in AFOSR-TR-75-1431. In the present study the optimality criteria method is extended to provide a capability for the automated minimum weight design of elastic,redundant structures composed of one-and two-dimensional structural elements and subjected to multiple,independent static loading conditions. The design variables are taken to be the thicknesses of the structural elements. These variables are constrained to be between specified maximum and minimum values,as are the internal stresses in each element and the nodal displacements of the structure. Results are presented to indicate both the excellent performance of the optimality criteria method and the wide range of structures which can be designed using the algorithm. Finally,the algorithm is extended to include the new (to automated design) and very important requirement that structural integrity under the applied loads be maintained given the presence of existing structural fatigue cracks. This requirement,which is cast in an energy format and incorporated in the design algorithm as an inequality constraint,is shown to have a dominant effect in the design of safe,minimum weight aircraft structures. (Author)