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Investigation of Three-Dimensional Stress Fields and Slip Systems for FCC Single Crystal Superalloy Notched SpecimensMetals 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 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 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.
Document ID
20040082294
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Arakere, Nagaraj K.
(Florida Univ. Gainesville, FL, United States)
Magnan, Shannon
(Florida Univ. Gainesville, FL, United States)
Ebrahimi, Fereshteh
(Florida Univ. Gainesville, FL, United States)
Ferroro, Luis
(Florida Univ. Gainesville, FL, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2004
Subject Category
Metals And Metallic Materials
Meeting Information
Meeting: ASME Turbo Expo
Location: Vienna
Country: Austria
Start Date: June 14, 2004
End Date: June 17, 2004
Sponsors: American Society of Mechanical Engineers
Funding Number(s)
OTHER: 376-20-20
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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