Reliability Based Design Using Variable Fidelity Optimization

Competitive marketplaces have driven the need for simulation based design optimiza-tion to produce efficient and cost effective designs. However, such design practices are typically deterministic and don’t take into account model uncertainties or manufacturing tolerances. Deterministic designs may lie on failure driven constraints, resulting in de-signs characterized by a high probability of failure. Reliability based design optimization (RBDO) methods have been developed to obtain designs that optimize a merit function while ensuring a target reliability level. Unfortunately, these methods are notorious for the high computational expense they require to converge. There has been a considerable effort to reduce the computational cost, many of these methods have used approximations which are not guaranteed to converge to the optimal solution of the original high fidelity problem. In this research variable fidelity methods are used to reduce the cost of RBDO. Variable fidelity methods use a set of models with varying degrees of fidelity and computa-tional expense to reduce the cost of optimization. The variable fidelity RBDO methodology developed in this investigation is demonstrated on two test cases: a nonlinear analytic prob-lem and a high-lift airfoil design problem. For each of these problems the proposed metho