Effect of Wear on the Forced Response of a Shrouded Blade

Abstract

Abstract Dry friction damping is a commonly used approach in reducing resonant amplitudes in turbomachinery vibrations to prevent High Cycle Fatigue (HCF) failure of the blades in turbines or compressors. Intentional friction contact provides additional damping to the overall system by means of dry friction; however, predicting the forced response of frictionally constrained structures can be challenging due to the nonlinear nature of the problem. Although previous studies have worked on designing and mathematical modelling of various friction dampers, the effect of cumulative wear degradation on the structure over the operational lifetime is often underestimated. In this paper, the finite element model of a shrouded blade is used for this purpose as a case study. Harmonic Balance Method (HBM) in conjunction with Receptance Method (RM) is utilized to formulate the nonlinear algebraic equations of motion which are solved in frequency domain. In this study, one dimensional dry friction element with normal load variation is used in modeling friction contact. Alternating Frequency Time (AFT) method is used to obtain the harmonic coefficients, also known as Fourier coefficients, of the nonlinear forces introduced by frictional contact. Additionally, the well-known wear-energy method, which predicts the wear degradation at the contact interface is coupled to the nonlinear forced response analysis. This study aims to investigate how wear affects the dynamic response, performance, and reliability of the shrouded blade case study considered.