NDLI: Investigation of Three-Dimensional Stress Fields and Slip Systems for FCC Single Crystal Superalloy Notched Specimens

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Nagaraj, K. Arakere Siddiqui, Shadab Magnan, Shannon Ebrahimi, Fereshteh Luis, E. Forero
Copyright Year	2004
Abstract	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.
Sponsorship	International Gas Turbine Institute
Starting Page	207
Ending Page	215
Page Count	9
File Format	PDF
ISBN	0791841715
DOI	10.1115/GT2004-53938
e-ISBN	0791837394
Volume Number	Volume 6: Turbo Expo 2004
Conference Proceedings	ASME Turbo Expo 2004: Power for Land, Sea, and Air
Language	English
Publisher Date	2004-06-14
Publisher Place	Vienna, Austria
Access Restriction	Subscribed
Subject Keyword	Elastic constants Deformation Intermetallic compounds Accounting Metals Crystals Alloys Fracture (materials) Superalloys Stress Crack propagation Fracture toughness Finite element model Anisotropy Tension Shapes Fatigue damage Testing
Content Type	Text
Resource Type	Article

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