Single crystal nickel-base superalloys deform by shearing along <111> planes, sometimes referred to as “octahedral” slip planes. Under fatigue loading, cyclic stress produces alternating slip reversals on the critical slip systems which eventually results in fatigue crack initiation along the ‘critical’ octahedral planes. A ‘critical plane’ fatigue modeling approach was developed in the present study to analyze high cycle fatigue (HCF) failures in single crystal materials. This approach accounted for the effects of crystal orientation and the micromechanics of the deformation and slip mechanisms observed in single crystal materials. Three-dimensional (3-D) stress and strain transformation equations were developed to determine stresses and strains along the crystallographic octahedral planes and corresponding slip systems. These stresses and strains were then used to calculate several multiaxial critical plane parameters to determine the amount of fatigue damage and also the ‘critical planes’ along which HCF failures would initiate. The computed fatigue damage parameters were used along with experimentally measured fatigue lives, at 1100° F, to correlate the data for different loading orientations. Microscopic observations of the fracture surfaces were used to determine the actual octahedral plane (or facet) on which fatigue initiation occurred. X-ray diffraction measurements were then used to uniquely identify this damage initiation facet with respect to the crystal orientation in each specimen. These experimentally determined HCF initiation planes were compared with the analytically predicted ‘critical planes’.
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ASME Turbo Expo 2002: Power for Land, Sea, and Air
June 3–6, 2002
Amsterdam, The Netherlands
Conference Sponsors:
- International Gas Turbine Institute
ISBN:
0-7918-3609-6
PROCEEDINGS PAPER
Critical Plane Fatigue Modeling and Characterization of Single Crystal Nickel Superalloys
Rajiv A. Naik,
Rajiv A. Naik
Pratt & Whitney, East Hartford, CT
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Daniel P. DeLuca,
Daniel P. DeLuca
Pratt & Whitney, East Hartford, CT
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Dilip M. Shah
Dilip M. Shah
Pratt & Whitney, East Hartford, CT
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Rajiv A. Naik
Pratt & Whitney, East Hartford, CT
Daniel P. DeLuca
Pratt & Whitney, East Hartford, CT
Dilip M. Shah
Pratt & Whitney, East Hartford, CT
Paper No:
GT2002-30300, pp. 675-682; 8 pages
Published Online:
February 4, 2009
Citation
Naik, RA, DeLuca, DP, & Shah, DM. "Critical Plane Fatigue Modeling and Characterization of Single Crystal Nickel Superalloys." Proceedings of the ASME Turbo Expo 2002: Power for Land, Sea, and Air. Volume 4: Turbo Expo 2002, Parts A and B. Amsterdam, The Netherlands. June 3–6, 2002. pp. 675-682. ASME. https://doi.org/10.1115/GT2002-30300
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