Reliability-based structural design of aircraft together with future tests

Abstract

Traditional optimization changes variables that are available in the design stage to optimize objectives, such as aircraft structural reliability. However, there are many post-design measures, such as tests and structural health monitoring that reduce uncertainty and further improve the reliability. In this paper, a new reliability-based design framework that can include post-design uncertainty reduction variables is proposed. Among many post-design variables, this paper focuses on the number of coupon tests and the number of structural element tests. Uncertainty in the failure stress prediction, variability due to the finite number of coupon tests, and uncertainties in geometry and service conditions are studied in detail. The Bayesian technique is used to update the failure stress distribution based on results of the element tests. Tradeoff plots of the number of tests, weight and probability of failure in certification and in service are generated, and finally reliability-based design of future tests together with aircraft structure is performed for minimum lifecycle cost. Copyright © 2010 by E. Acar, R.T. Haftka, and N.H. Kim.