Finite element modelling and experimental validation of the Main Landing Gear of a trainer aircraft

As structures have become more complex, the analysts were forced to approximations of closed-form solutions, experimentation or numerical methods. In particular with the advent of digital computers many numerical techniques used in engineering applications have been developed. Numerical techniques generally employ a method which discretizes the continuum of the structural system into a finite collection of points by means of mathematical relations from elasticity. The most common technique is the finite element method (FEM) which allows accurate representation of complex geometry, inclusion of dissimilar material properties, user-friendly representation of the total solution and capture of local effects. Once the numerical results have been obtained, in order to understand if they have a real confirmation, experimental tests are set up. The most used experimental method employs electrical resistance strain gages. In this work, both methodologies, numeric and experimental, are applied to a trainer aircraft main landing gear and relative results are compared. Firstly an overview of basic theory of FEM elements is presented, explaining what lies behind software elements. Only the elements most commonly used in the final model are treated. After a brief description of pre and post processor, both FEM analysis of stick model (extracted from CAD) and FEM analysis of three major components are shown. In addition load cases have been investigated: they are calculated using CS 23 regulation and multibodies analyses. Relative results related to the analysed load conditions are compared with lab test results, obtained by the application of strain gauges in the same most stressed areas of real stresses from FEM analysis. As a conclusion, the numerical and experimental comparison highlights the main contributions provided by this work for the identification of reliable values of stress and deformation and consequent model validation.