Standard Methods for Aerospace Stress Analysis

3FEA Modeling Approach

3.1 Introduction to General FEA Modeling Approach

Finite element modeling (FEM) or finite element analysis (FEA) is an essential approach to the development of a global model that includes the plate elements, laminate elements, beams, rods, trusses, CBUSH spring/dampers, and solid elements representing the aerospace vehicle buildup. For example, aircraft shell skins are modeled as plates or laminates, and frames are modeled as beams in a FEM model (i.e. Figure 3.1). Once the FEA model is generated, the loads, such as the maneuvering loads, flight loads, inertia loads, internal pressure, and landing loads, are applied to the model. Then, boundary constraints are defined on the aircraft. The FEA is run, and the displacements, component loads, and stress levels are numerically computed. Component loads are considered and used to do local stress analysis of the components for typical stresses such as normal and shear stresses, as well as buckling of long members and shells.

FEA is a tool that can also be utilized to perform further detailed analysis of the cross‐section or part under loading. For example, a frame bay of the aircraft can be modeled alone to investigate the buckling modes of the frame where otherwise hand calculation would not be possible. Refer to Figure 3.2 for an example of a bay frame under buckling investigation.

FEA technique can be used in determining the stress levels and displacement of aerospace structures where a temperature gradient ...