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Title: Microstructure and mesh sensitivities of mesoscale surrogate driving force measures for transgranular fatigue cracks in polycrystals

The number of cycles required to form and grow microstructurally small fatigue cracks in metals exhibits substantial variability, particularly for low applied strain amplitudes. This variability is commonly attributed to the heterogeneity of cyclic plastic deformation within the microstructure, and presents a challenge to minimum life design of fatigue resistant components. Our paper analyzes sources of variability that contribute to the driving force of transgranular fatigue cracks within nucleant grains. We also employ crystal plasticity finite element simulations that explicitly render the polycrystalline microstructure and Fatigue Indicator Parameters (FIPs) averaged over different volume sizes and shapes relative to the anticipated fatigue damage process zone. Volume averaging is necessary to both achieve description of a finite fatigue damage process zone and to regularize mesh dependence in simulations. Furthermore, results from constant amplitude remote applied straining are characterized in terms of the extreme value distributions of volume averaged FIPs. Grain averaged FIP values effectively mitigate mesh sensitivity, but they smear out variability within grains. Furthermore, volume averaging over bands that encompass critical transgranular slip planes appear to present the most attractive approach to mitigate mesh sensitivity while preserving variability within grains.
Authors:
 [1] ;  [2]
  1. Woodruff School of Mechanical Engineering, Atlanta, GA (United States)
  2. Georgia Inst. of Technology, Atlanta, GA (United States)
Publication Date:
OSTI Identifier:
1235290
Report Number(s):
SAND--2015-2384J
Journal ID: ISSN 0921-5093; 579580
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
Additional Journal Information:
Journal Volume: 639; Journal ID: ISSN 0921-5093
Publisher:
Elsevier
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
Georgia Institute of Technology, Atlanta, GA (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE fatigue; microstructure; crystal plasticity; cyclic loading; probability and statistics