Abstract
Fretting fatigue is most likely to occur in the dovetail joint of aero engine compressor resulting in small amplitude displacement of a few micrometers. This leads to degradation of the material in the form of fatigue strength and corrosion. This paper reports optimal conditions of blade geometrical parameters such as flank length, flank angle and coefficient of friction in order minimize the failure due to fretting fatigue. ANOVA indicated that Von-mises stresses, deformation, contact pressure and sliding distance were influenced by coefficient of friction and flank angle. While deformation, contact pressure and sliding distance decreased with increase in coefficient of friction and increased with increase in flank angle and flank length. Von-mises stress increased with increase in coefficient of friction. Response surface methodology results indicated that the optimum value of Von-mises stress (328.24 MPa), deformation (153.87 µm), contact pressure (275.48 MPa) and sliding distance (80.66 µm) were found at coefficient of friction 0.35, flank angle 65° and flank length of 12 mm which were in agreement with those of grey relational analysis results.
Highlights
Aeroengine compressor rotates at very high speed of 10000-17000 rpm and induces high centrifugal stresses [1]
Contact pressure decreased with increase in coefficient of friction (COF) from 0.1 to 0.4 and increased with increase in flank angle from 64° to 70° and flank length from 12 mm to 14 mm as predicted from the main effects plot as shown in the Fig. 4
Nonlinear static structural analysis was carried out to examine the effect of geometrical parameters such as coefficient of friction, flank angle and flank length on fretting fatigue responses such as von-Mises stress, deformation, contact pressure and sliding distance
Summary
Aeroengine compressor rotates at very high speed of 10000-17000 rpm and induces high centrifugal stresses [1]. Due to the complexity of loading and interaction between two surfaces in dovetail joint, high stresses are induced which leads to crack and subsequent failure due to fretting fatigue phenomenon. Papanikos et al reported that coefficient of friction, flank angle and flank length influenced the maximum stress concentration below the lower contact point of the blade and disc interface. Nandish et al carried out contact stress analysis of the dovetail attachment with and without friction along the contact length using theoretical and finite element formulation for IMI685 material. Hammouda et al analyzed the macro mechanics behavior of the fretted surfaces in dovetail joints in aero engine compressors using two dimensional elasto-plastic finite element analysis. Malay et al [6] investigated variation of stresses and crack growth assessment in the dovetail joint of compressor disc. Witek [7] investigated finite element numerical analysis of the turbine casing of an aero engine to present stress and deformation
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