Standard Methods for Aerospace Stress Analysis

14Dynamics and Vibration Aspects

14.1 Introduction to Dynamic and Vibration Aspects of the Structures

The dynamic response of a structural assembly is of interest in aircraft stress analysis. Repeated harmonic and nonharmonic behavior of structures and their subassemblies could lead to failure and fatigue of the structures. In an aircraft, there are engines that consciously rotating and generating harmonic motion, and any imbalance of such motion could result in failure loads that could lead to catastrophic failure of the aircraft. For this reason, it is important that the fundamentals of structural dynamics or vibrations are known, and how to evaluate them is explained.

14.2 Fundamental Concepts

Any structural system that is excited and is in motion could at any time achieve the resonant frequencies of the structure. The resonant frequencies are the repeated motions of the system based on its natural frequency that, if it does not foresee a damping of some kind, either internal or external, could continue forever. Every structure has its own embedded natural frequencies at which the system freely vibrates until it is stopped by an exerted forcing or damping.

Here, in this chapter, we examine two main structural dynamics topics. The topic of shell plate vibration for either metallic or composite material, and also the structural assembly vibration of interior monuments. These two topics are at the very base of structural failure in an aircraft.

14.3 Analytical Methods for ...