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Research Papers: Gas Turbines: Structures and Dynamics

Fatigue Crack Growth Behavior Evaluation of Grainex Mar-M 247 for NASA’s High Temperature High Speed Turbine Seal Test Rig

[+] Author and Article Information
Irebert R. Delgado

Glenn Research Center, National Aeronautics and Space Administration, 21000 Brookpark Road, Cleveland, OH 44135irebert.r.delgado@nasa.gov

Bruce M. Steinetz

Glenn Research Center, National Aeronautics and Space Administration, 21000 Brookpark Road, Cleveland, OH 44135

Clare M. Rimnac, John J. Lewandowski

 Case Western Reserve University, Cleveland, OH 44106

J. Eng. Gas Turbines Power 131(2), 022504 (Dec 22, 2008) (12 pages) doi:10.1115/1.2980058 History: Received January 10, 2008; Revised May 28, 2008; Published December 22, 2008

The fatigue crack growth behavior of Grainex Mar-M 247 is evaluated for NASA’s turbine seal test facility. The facility is used to test air-to-air seals primarily for use in advanced jet engine applications. Because of extreme seal test conditions of temperature, pressure, and surface speeds, surface cracks may develop over time in the disk bolt holes. An inspection interval is developed to preclude catastrophic disk failure by using experimental fatigue crack growth data. By combining current fatigue crack growth results with previous fatigue strain-life experimental work, an inspection interval is determined for the test disk. The fatigue crack growth life of NASA disk bolt holes is found to be 367cycles at a crack depth of 0.501mm using a factor of 2 on life at maximum operating conditions. Combining this result with previous fatigue strain-life experimental work gives a total fatigue life of 1032cycles at a crack depth of 0.501mm. Eddy-current inspections are suggested starting at 665cycles since eddy current detection thresholds are currently at 0.381mm. Inspection intervals are recommended every 50cycles when operated at maximum operating conditions.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

NASA’s turbine seal test facility

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Figure 2

Surface flaw (Kb) specimen geometry for the GXMM247 fatigue crack growth tests at 649°C. Dimensions are in millimeters.

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Figure 3

Location of fatigue crack-growth Kb specimens from the sacrificial GXMM247 disk

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Figure 4

Surface flaw geometry for the (Kb) specimen. Dimensions are in millimeters. See Fig. 2 for notch location on the (Kb) specimen.

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Figure 5

Kb specimen with alumel wire attachments for potential drop crack growth measurement

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Figure 6

Fatigue crack growth test equipment and controls at NASA’s fatigue and fracture laboratories

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Figure 7

Alumel wire location at the notch area of the Kb specimen

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Figure 8

Nominal fatigue crack growth pretest measurement for the Kb specimen surface flaw geometry

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Figure 9

Thermocouple locations on the Kb specimen gauge section indicated by the arrows. Thermocouples are not shown.

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Figure 10

Fracture surface measurements for the GXMM247 (Kb specimen 13K). Dimensions are in millimeters.

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Figure 11

Fracture surface measurements for the GXMM247 (Kb specimen 32K). Dimensions are in millimeters.

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Figure 12

Fatigue crack growth behavior for GXMM247 at 649°C (Kb specimen 13K)

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Figure 13

Fatigue crack growth behavior for GXMM247 at 649°C (Kb specimen 32K)

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Figure 14

Regression results using both specimen data sets for the GXMM247 fatigue crack growth Kb data

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Figure 15

Fatigue crack growth rate versus the crack depth for GXMM247 at 649°C (Kb specimen 13K)

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Figure 16

GXMM247 fatigue crack growth fracture surface for Kb specimen 13K at 649°C. Dotted area is enlarged in Fig. 1.

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Figure 17

Close-up of GXMM247 fatigue crack growth fracture surface features for Kb specimen 13K at 649°C. Low ΔK region: 23.3–26.4MPa and high ΔK region: 35.7–39.1MPa. SEM (SE mode).

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Figure 18

GXMM247 fatigue crack growth fracture surface for Kb specimen 13K at 649°C showing the grain boundary near beginning of fatigue crack growth (SEM BE mode)

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Figure 19

Low ΔK fatigue striations of the GXMM247 fatigue crack growth fracture surface for Kb specimen 13K at 649°C (SEM SE mode, see also Fig. 1). ΔK range from 23.3Mpato26.4MPa. Arrow indicates the crack growth direction.

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Figure 20

High ΔK fatigue striations of the GXMM247 fatigue crack growth fracture surface for Kb specimen 13K at 649°C (SEM SE mode; see also Fig. 1). ΔK range from 35.7Mpato39.1MPa. Arrow indicates the crack growth direction.

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Figure 21

Comparison of GXMM247 to literature (23-26)

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Figure 22

GXMM247 NASA disk fatigue crack growth rate with increasing cycles at 649°C

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Figure 23

Total fatigue life of GXMM247 at maximum operating conditions of the NASA turbine seal test rig

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Figure 24

Decision flow chart for implementing the eddy-current inspection interval for the GXMM247 NASA disk

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