Crystal Plasticity Modelling and HR-DIC Measurement of Slip Activation and Strain Localisation in Single and Oligo-crystal Ni Alloys under Fatigue
File(s)
Published version
Accepted version
Author(s)
Type
Journal Article
Abstract
Single crystal (CMSX4) and oligocrystal (MAR002) nickel have been studied using three-point beam
bending under conditions of cyclic loading. SEM images have enabled identification of slip activation,
and high resolution digital image correlation has been utilized to quantify the developing strain fields
and the strain localization in both single and oligocrystals in fatigue. The single and oligocrystal
microstructures have been replicated within crystal plasticity finite element models and the fatigue
loading analysed such that grain-by-grain comparisons of slip may be carried out. Single and multiple
slip activation, slip localisation and microstructure-sensitive stress evolution have been examined.
Single crystal bend fatigue gives rise to non-symmetric slip fields and localisation depending on
crystallographic orientation. Modelling correctly captures slip activation and the developing nonsymmetric
slip fields. Oligocrystal slip is markedly heterogeneous, with grain misorientations driving
strong variations, also reasonably captured by the model. Microstructure behaviour is found to vary
spatially and include elastic-plastic hysteresis which is stable, and which undergoes mean stress
relaxation so that plastic shakedown occurs. Remarkable variations occur between locations either
side of grain boundaries, providing appropriate opportunities for fatigue crack nucleation.
bending under conditions of cyclic loading. SEM images have enabled identification of slip activation,
and high resolution digital image correlation has been utilized to quantify the developing strain fields
and the strain localization in both single and oligocrystals in fatigue. The single and oligocrystal
microstructures have been replicated within crystal plasticity finite element models and the fatigue
loading analysed such that grain-by-grain comparisons of slip may be carried out. Single and multiple
slip activation, slip localisation and microstructure-sensitive stress evolution have been examined.
Single crystal bend fatigue gives rise to non-symmetric slip fields and localisation depending on
crystallographic orientation. Modelling correctly captures slip activation and the developing nonsymmetric
slip fields. Oligocrystal slip is markedly heterogeneous, with grain misorientations driving
strong variations, also reasonably captured by the model. Microstructure behaviour is found to vary
spatially and include elastic-plastic hysteresis which is stable, and which undergoes mean stress
relaxation so that plastic shakedown occurs. Remarkable variations occur between locations either
side of grain boundaries, providing appropriate opportunities for fatigue crack nucleation.
Date Issued
2016-10-05
Date Acceptance
2016-10-01
Citation
International Journal of Plasticity, 2016, 88, pp.70-88
ISSN
0749-6419
Publisher
Elsevier
Start Page
70
End Page
88
Journal / Book Title
International Journal of Plasticity
Volume
88
Copyright Statement
© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Sponsor
Engineering & Physical Science Research Council (E
Technology Strategy Board
Beijing Institute of Aeronautical Materials (BIAM)
Royal Academy Of Engineering
Royal Academy Of Engineering
Grant Number
EP/K503733/1
110123
N/A
RF/129
MMRE_P54661
Subjects
Mechanical Engineering & Transports
0905 Civil Engineering
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status
Published