Airframe Integrity Based on Bayesian Approach

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dc.contributor.advisorModarres, Mohammaden_US
dc.contributor.authorHurtado-Cahuao, Jose Luisen_US
dc.contributor.departmentMechanical Engineeringen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2007-02-01T20:23:02Z
dc.date.available2007-02-01T20:23:02Z
dc.date.issued2006-11-29en_US
dc.description.abstractAircraft aging has become an immense challenge in terms of ensuring the safety of the fleet while controlling life cycle costs. One of the major concerns in aircraft structures is the development of fatigue cracks in the fastener holes. A probabilistic-based method has been proposed to manage this problem. In this research, the Bayes' theorem is used to assess airframe integrity by updating generic data with airframe inspection data while such data are compiled. This research discusses the methodology developed for assessment of loss of airframe integrity due to fatigue cracking in the fastener holes of an aging platform. The methodology requires a probability density function (pdf) at the end of SAFE life. Subsequently, a crack growth regime begins. As the Bayesian analysis requires information of a prior initial crack size pdf, such a pdf is assumed and verified to be lognormally distributed. The prior distribution of crack size as cracks grow is modeled through a combined Inverse Power Law (IPL) model and lognormal relationships. The first set of inspections is used as the evidence for updating the crack size distribution at the various stages of aircraft life. Moreover, the materials used in the structural part of the aircrafts have variations in their properties due to their calibration errors and machine alignment. A Matlab routine (PCGROW) is developed to calculate the crack distribution growth through three different crack growth models. As the first step, the material properties and the initial crack size are sampled. A standard Monte Carlo simulation is employed for this sampling process. At the corresponding aircraft age, the crack observed during the inspections, is used to update the crack size distribution and proceed in time. After the updating, it is possible to estimate the probability of structural failure as a function of flight hours for a given aircraft in the future. The results show very accurate and useful values related to the reliability and integrity of airframes in aging aircrafts. Inspection data shown in this dissertation are not the actual data from known aircrafts and are only used to demonstrate the methodologies.en_US
dc.format.extent6051589 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.urihttp://hdl.handle.net/1903/4183
dc.language.isoen_US
dc.subject.pqcontrolledEngineering, Mechanicalen_US
dc.subject.pqcontrolledEngineering, Generalen_US
dc.subject.pquncontrolledCrack Growthen_US
dc.subject.pquncontrolledCrack Size Distributionen_US
dc.subject.pquncontrolledBayesian Updatingen_US
dc.subject.pquncontrolledLife Managementen_US
dc.subject.pquncontrolledStructural Reliabilityen_US
dc.titleAirframe Integrity Based on Bayesian Approachen_US
dc.typeDissertationen_US

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