FRICTION DAMPING OF HOLLOW AIRFOILS - PART I - THEORETICAL DEVELOPMENT

The quest for higher performance engines in conjunction with the requi rement for lower life cycle costs has resulted in stage configurations that ale more susceptible to high cycle fatigue. One solution is the use of innovative approaches that introduce additional mechanical damp ing. The present paper describes an approach that may be used to asses s the benefits of friction dampers located within internal cavities of a hollow structure. The friction dampers used in this application are often relatively thin devices that, if unconstrained have natural fre quencies in the same range as the natural frequencies of the hollow ai rfoil. Consequently, the analytical approach that is developed is dist inct in that it has to lake into account the dynamic response of the d amper and how it changes as the amplitude of the vibration increases. In this paper, results from the analytical model are compared with ind ependently generated results from a time integration solution of a thr ee mass rest problem. Results from the analytical model are compared w ith experimental data in a companion paper.