Finite element analysis modeling (fea) using fea programs, together with hand calculations, are used to show that a structure will not fail at ultimate loads nor yield at limit loads. Usually the loads are calculated per FAR Part 23, 25, or 27. Loads and stresses in highly redundant structures can be accurately determined using fea methods. A structure can be subjected to airloads, pressure loads, thermal loads, and dynamic loads from shock or random vibration excitation. The fea can take into account the combination of these loads. The material properties and loads can be linear or non-linear. ADI makes extensive use of fea modeling.
A detailed finite element analysis shows the stress distribution in the wing spar, skin, and rib components. For composite structures, the in-plane tension, compression, and shear stresses are shown and compared to material design allowables. The out-of -plane shear stress in the core elements are also determined for sandwich elements. On the left, the shear stress in the face sheet is shown on a deflected wing. The red and gray show areas of high stress.
Often a complete fuselage structure is modeled. After a static analysis is performed, the fea input file is modified to perform the eigenvalue analysis necessary for a flutter analysis.