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Simplified modeling methods for mechanically fastened connections in flight structures

  • Author(s): Brewer, Brett Andrew
  • et al.
Abstract

Simplified modeling and analyses methods for aerospace connectors have been around for the better part of 30 years, but continue to evolve with technology. For the preliminary design process, the modeling of individual fasteners is time consuming and unforgiving, as the fastener sizes and locations often change during the process, necessitating a new model each iteration. Further simplifying the design process introduces a so called connector pad, which acts as a representative for entire groups of fasteners within a finite element model. Expanding upon previous developments from the last quarter century, this new method creates small groups of solid elements that are able to accurately represent any number of fasteners that exist within that region. Using FEMAP and NX NASTRAN to validate extensive linear displacement test data, this connector pad can be seen as another successful way to model mechanical connectors in flight structures. The success of the model lies strictly in linear displacements, however. Stresses, strengths, and margins of safety are not considered in this Thesis, though it is possible to extract such data. A group of specimens, consisting of varying state of the art connector types such as Hi-Lok fasteners, and ranging in connection density from two to eight fasteners, was tested axially within the linear elastic range. This data was compared to several different computer based fastener modeling techniques, such as using springs, beams, solids, or the new connector pad to represent the fastener. Not only does this study work to further validate the established techniques, but it also gives rise to the possibilities and advantages of a new, more simplified approach to modeling mechanical fasteners in aircraft

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