Force Amplification Research Articles

Dynamic Analysis of Mechanical Systems With Clearances—Part 1: Formation of Dynamic Model

A mathematical model of an elastic mechanical joint with clearances has been formulated and the dynamical equations of motion derived (Part I). The model, which we have called an Impact Pair, is basic to the determination of the dynamical response of mechanical and electromechanical systems with clearances, including determination of dynamic force amplification, frequency response, time-displacement characteristics, and other dynamic characteristics. Whenever possible, the results for the impact pair under various operating conditions are illustrated by graphs, which may also offer some insight into the behavior of clearance-coupled systems.

Fluidelastic Forces on Circular Cylinders

The fluidelastic behavior of a circular cylinder was studied. It is argued that improved empirical data on cylinders exposed to fluid flow are needed, and that it is better to impose cylinder motions and to measure the resultant fluid lift forces than to study the fluidelastic response directly. Accordingly, lift force data were collected, yielding direct evidence of fluidelastic force amplification and outline limits to the energy that may be extracted from the fluid flow and channeled into sustaining the more serious flow-induced vibrations. The application of fluid lift data at the design stage of cylindrical structures is most feasible when it comes to the question of tradeoff between permissible amplitude and the damping to be provided. Use of lift force data in computing the complete structural response is shown to be more problematic.