Non Linear Effects of Applied Loads and Large Deformations on Aircraft Normal Modes
Abstract
Ground Vibration Test (GVT) is the typical way to verify structural dynamic models. The conditions in which the GVT is performed -the aircraft subjected and deformed under gravity loads- are different from the conditions in which the Finite Element Method (FEM) model is usually elaborated (jig shape without loads). They are also different from the in-flight conditions (the aircraft subjected and deformed under inertia and aerodynamic forces). Although in most cases those differences can be negligible, it is not the case of a very large airplane in which the size and flexibility effects are of such nature that updating a FEM model to match GVT results could go in the opposite direction to the actual airplane in-flight. This paper analyses the influence of aircraft deformation (down bending for GVT, jig shape for FEM model, up bending for flight), shape (control surfaces deflections...), and loads (gravity on ground, inertial and aerodynamic forces in flight) on normal modes to have a better insight in GVT and flight test measurements interpretation of a very large airplane. Those effects are significant especially where large concentrated masses (engine-pylon) are present.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 2000
- Accession Number
- ADP010495
Entities
People
- F. Rosich
- H. Climent
- Matthew J. Oliver