Experimental and Numerical Analysis of a Helicopter Gear Box Support

A numerical analysis of a particular helicopter gear box support is presented. Different finite element models of the complete support have been created. Starting from a simplified model up to a more complex one, the sensitivity to the change of the elements used and the refinement of the mesh has been investigated to better understand the capability of the different models to predict correctly the stresses in the structure when subjected to the same loads as those applied in the experimental tests. Validation of each single model has been made by comparison with experimental data from different fatigue tests. Besides the classical way to measure the deformations, a much more recent method, the thermoelastic stress analysis (TSA), has been used to measure stress entity and its distribution. The major advantages in the adoption of a TSA are: it is a non destructive and non intrusive method for stress analysis; during the tests a direct qualitative and quantitative distribution of the principal stresses is available; it can be used to make a direct comparison with a finite element analysis. The paper illustrates in detail the FEM models and the possibility to use the TSA as a valid tool for a direct comparison between the experimental and numerical results, instead of the more classic way to compare FEM analysis results with those taken from strain gages measurements.