Effect of Number of Contact Points on the Fretting Wear Estimation of a Frictionally Damped Blade Platform

Abstract

Frictional interfaces, which induce energy dissipation in the system, are intentionally included in bladed disk system of gas turbine engines. By this way, resonant amplitude of the blade is decreased while high cycle fatigue failure of these structures is postponed. Mathematical modeling of the problem becomes complicated due to the nonlinear nature of the frictional contact which also adds difficulty to the solution of the problem. Time domain solution methods are expensive compared to frequency domain method for the determination of steady state response of nonlinear systems. Therefore, Harmonic Balance Method (HBM) is employed to constitute the set of algebraic equations to be solved numerically. Alternating Frequency Time (AFT) Method is utilized to find the Fourier coefficients of the friction force in an iterative way. In addition, analytical Jacobian formulation is implemented to the friction model to enhance the solution performance. Although various friction dampers have been designed, mathematically modeled, and discussed before, fretting wear which is the inevitable outcome of the dry friction is underemphasized up until today. In this work, a blade platform system which represents a simplified underplatform damper is studied to investigate the effect of number of macroslip friction elements on wear estimation and the effect of wear on the dynamic response of the system.