Metals and their alloys, except for a few intermetallics, are inherently ductile, i.e. plastic deformation precedes fracture in these materials. Therefore, resistance to fracture is directly related to the development of the plastic zone at the crack tip. Recent studies indicate that the fracture toughness of single crystals depends on the crystallographic orientation of the notch as well as the loading direction. In general, the dependence of crack propagation resistance on crystallographic orientation arises from the anisotropy of (i) elastic constants, (ii) plastic deformation (or slip), and (iii) the weakest fracture planes (e.g. cleavage planes). Because of the triaxial stress state at the notch tips, many slip systems that otherwise would not be activated during uniaxial testing, become operational. The plastic zone formation in single crystals has been tackled theoretically by Rice and his co-workers [10–14] and only limited experimental work has been conducted in this area. The study of the stresses and strains in the vicinity of a FCC single crystal notch tip is of relatively recent origin. We present experimental and numerical investigation of 3D stress fields and evolution of slip sector boundaries near notches in FCC single crystal PWA1480 tension test specimens, and demonstrate that a 3D linear elastic finite element model that includes the effect of material anisotropy is shown to predict active slip planes and sectors accurately. The slip sector boundaries are shown to have complex curved shapes with several slip systems active simultaneously near the notch. Results are presented for surface and mid-plane of the specimens. The results demonstrate that accounting for 3D elastic anisotropy is very important for accurate prediction of slip activation near FCC single crystal notches loaded in tension. Results from the study will help establish guidelines for fatigue damage near single crystal notches.
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ASME Turbo Expo 2004: Power for Land, Sea, and Air
June 14–17, 2004
Vienna, Austria
Conference Sponsors:
- International Gas Turbine Institute
ISBN:
0-7918-4171-5
PROCEEDINGS PAPER
Investigation of Three-Dimensional Stress Fields and Slip Systems for FCC Single Crystal Superalloy Notched Specimens
Nagaraj K. Arakere,
Nagaraj K. Arakere
University of Florida, Gainesville, FL
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Shadab Siddiqui,
Shadab Siddiqui
University of Florida, Gainesville, FL
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Fereshteh Ebrahimi,
Fereshteh Ebrahimi
University of Florida, Gainesville, FL
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Luis E. Forero
Luis E. Forero
University of Florida, Gainesville, FL
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Nagaraj K. Arakere
University of Florida, Gainesville, FL
Shadab Siddiqui
University of Florida, Gainesville, FL
Shannon Magnan
United States Navy Reserve
Fereshteh Ebrahimi
University of Florida, Gainesville, FL
Luis E. Forero
University of Florida, Gainesville, FL
Paper No:
GT2004-53938, pp. 207-215; 9 pages
Published Online:
November 24, 2008
Citation
Arakere, NK, Siddiqui, S, Magnan, S, Ebrahimi, F, & Forero, LE. "Investigation of Three-Dimensional Stress Fields and Slip Systems for FCC Single Crystal Superalloy Notched Specimens." Proceedings of the ASME Turbo Expo 2004: Power for Land, Sea, and Air. Volume 6: Turbo Expo 2004. Vienna, Austria. June 14–17, 2004. pp. 207-215. ASME. https://doi.org/10.1115/GT2004-53938
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