Investigation of the stability and instability failure modes of aircraft wing main spar web and comparison with fem and analytical methods


Thesis Type: Postgraduate

Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2014

Student: BERK KAPLANLIOĞLU

Supervisor: NİHAT GEMALMAYAN

Abstract:

Main spar of wing in aircraft systems is subjected to compression, tension, bending and shear forces due to aerodynamic loads. Under stresses due to the effect of these loads, stability (yield, ultimate) and instability (buckling, crippling) failure modes occur in main spar web and flanges. Within the scope of this thesis, aircraft wing main spar web is investigated for its normal stresses and its buckling strength which is an instability failure mode by using analytical methods and finite elements methods. These results are compared and evaluated. Fine FEM analysis method gives the best and most realistic results provided that the model is prepared according to standards and is verified. However, fine FEM of the entire aircraft takes so long time and requires too much effort. Thus it is not preferred to use in every case. For the first prototype of an aircraft, coarse FEM approaches can be preferred to be more conservative. The coarse FEM is very useful to perform fast and reliable sizing. Furthermore, estimating stress values on a panel by using coarse FEM proves reliable results when considering the maximum difference ratio between fine and coarse model is found as 8.68% due to a fillet which is a high stress concentration region. At the end of this thesis, therefore, a macro is written and developed based on analytical method and analytical results which are verified by finite element method.