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기술보고서 게시판 내용
타이틀	Reliability Based Design for a Raked Wing Tip of an Airframe
저자	Patnaik, Surya N.;; Pai, Shantaram S.;; Coroneos, Rula M.
Keyword	AIRFRAMES;; COMPOSITE MATERIALS;; DESIGN ANALYSIS;; FAILURE MODES;; LOADS (FORCES); RELIABILITY;; TRANSPORT AIRCRAFT;; WINGS
URL	http://hdl.handle.net/2060/20110023701
보고서번호	NASA/TM-2011-216808
발행년도	2011
출처	NTRS (NASA Technical Report Server)
ABSTRACT	A reliability-based optimization methodology has been developed to design the raked wing tip of the Boeing 767-400 extended range airliner made of composite and metallic materials. Design is formulated for an accepted level of risk or reliability. The design variables, weight and the constraints became functions of reliability. Uncertainties in the load, strength and the material properties, as well as the design variables, were modeled as random parameters with specified distributions, like normal, Weibull or Gumbel functions. The objective function and constraint, or a failure mode, became derived functions of the risk-level. Solution to the problem produced the optimum design with weight, variables and constraints as a function of the risk-level. Optimum weight versus reliability traced out an inverted-S shaped graph. The center of the graph corresponded to a 50 percent probability of success, or one failure in two samples. Under some assumptions, this design would be quite close to the deterministic optimum solution. The weight increased when reliability exceeded 50 percent, and decreased when the reliability was compromised. A design could be selected depending on the level of risk acceptable to a situation. The optimization process achieved up to a 20-percent reduction in weight over traditional design.