Finite Element Analysis and Vibration Testing of a Simple Replicate Beam-Type Aircraft Wing with and without Secondary Structure Attached

Ground vibration testing (GVT) is one of the most critical testing procedures for an airplane certification. With proper GVT, analysts can determine the stiffness distribution, natural frequencies, mode shapes and structural damping of each airplane components which are needed for flutter analysis and dynamic loads analysis. Hence the results from GVT are highly important. The problem identified in this paper is one that misleads the structural designing and might result in catastrophic situations, if proper attention is not given to the GVT results. During GVT, technicians and engineers attempt to instrument most of the primary components of the airplane, totally avoiding secondary structures such as bungees, gears, control surfaces, etc. The secondary structures are also of equal importance as the primary structures so that analysts can identify the in-phase and out-of- phase modes. If not, the tuning of the stiffness of the primary structure might not be accurate for flutter analysis, especially when the in-phase and out-of-phase modes are near to the structural modes of the primary structure. The goal of this paper is to recreate the above mentioned problem of the in-phase and out-of-phase mode for a small wing-gear like structure. The detailed objectives and methodologies of the work include, simulating the modal experiments and finite element analysis (FEA) on a free-free beam (primary structure) with and without flexible links (secondary structure) attached to them, determining the stiffness distribution and modal characteristics of the primary structure and the secondary structures, using GVT and FEA. Characterizing the in-phase and out-of- phase modes which involves both primary and secondary structure by signal processing and using simplified beam model (stick model) is another important goal of this research