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Gas Turbines: Structures and Dynamics

Probabilistic High-Cycle Fretting Fatigue Assessment of Gas Turbine Engine Components

[+] Author and Article Information
Kwai S. Chan, Michael P. Enright

 Southwest Research Institute, ® San Antonio, TX 78238

Patrick J. Golden

 Air Force Research Laboratory, Wright-Patterson AFB, OH, 45433

Samir Naboulsi

 High Performance Technologies, Inc., Wright-Patterson AFB, OH, 45433

Ramesh Chandra, Alan C. Pentz

 NAVAIRPatuxent River, MD, 20670

J. Eng. Gas Turbines Power 134(6), 062502 (Apr 12, 2012) (8 pages) doi:10.1115/1.4005975 History: Received August 09, 2011; Revised August 19, 2011; Published April 09, 2012; Online April 12, 2012

High-cycle fatigue (HCF) is arguably one of the costliest sources of in-service damage in military aircraft engines. HCF of turbine blades and disks can pose a significant engine risk because fatigue failure can result from resonant vibratory stresses sustained over a relatively short time. A common approach to mitigate HCF risk is to avoid dangerous resonant vibration modes (first bending and torsion modes, etc.) and instabilities (flutter and rotating stall) in the operating range. However, it might be impossible to avoid all the resonance for all flight conditions. In this paper, a methodology is presented to assess the influences of HCF loading on the fracture risk of gas turbine engine components subjected to fretting fatigue. The methodology is based on an integration of a global finite element analysis of the disk-blade assembly, numerical solution of the singular integral equations using the CAPRI (Contact Analysis for Profiles of Random Indenters) and Worst Case Fret methods, and risk assessment using the DARWIN (Design Assessment of Reliability with Inspection) probabilistic fracture mechanics code. The methodology is illustrated for an actual military engine disk under real life loading conditions.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Typical fan speed profile based on the composite mission. Points indicate load steps. From Chandra [1].

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Figure 2

Campbell diagram showing excitation at a frequency that deviates from integral engine order lines at about 72% max. engine speed

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Figure 3

Peak-to-peak (P2P) strain data as a function of time during stall flutter

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Figure 4

Dynamic stresses at various locations at the airfoil and the blade root normalized by the dynamic stress at location Y in the disk

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Figure 5

Finite element mesh of blade/disk assembly

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Figure 6

A refined mesh of first order hexahedral elements (C3D8) for the dovetail portion of the fan blade and the disk

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Figure 7

A comparison of computed and measured peak-to-peak stress ranges normalized by a constant for various strain gauges in the root section

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Figure 8

Combined LCF and HCF load history for a composite mission profile

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Figure 9

Dovetail geometry subjected to radial load R(t) and ΔRHCF (t) and ΔGHCF (t) due to high-cycle flow-induced vibration. Modified from Gean and Farris [18].

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Figure 10

Q and P history for a typical fan speed profile with ΔPHCF (t) and ΔQHCF (t) due to high-frequency forced vibrations due to stall flutter

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Figure 11

A comparison of the LCF stresses at maximum RPM, 72% maximum RPM, HCF maximum and minimum stresses at 72% maximum RPM, and HCF stress range at 72% maximum RPM as a function of crack depth

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Figure 12

A comparison of the predicted flight hours with and without the presence of HCF loads

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Figure 13

Comparisons of fracture risk of engine disk without and with HCF loads due to stall flutter

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Figure 14

Comparison of the LCF and HCF stresses against the threshold stresses for fatigue crack growth for stress ratio, R, values of 0.1 and 0.7

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