1111 Study on Prediction of Fatigue Crack Initiation in Irradiated Material using Electron Backscatter Diffraction

The common approach to crystal-plasticity finite element modeling for load-bearing prediction of metallic structures involves the simulation of simplified grain morphology and substructure detail. This paper details a methodology for predicting the structure–property effect of as-manufactured microstructure, including true grain morphology and orientation, on cyclic plasticity, and fatigue crack initiation in biomedical-grade CoCr alloy. The methodology generates high-fidelity crystal-plasticity finite element models, by directly converting measured electron backscatter diffraction metal microstructure grain maps into finite element microstructural models, and thus captures essential grain definition for improved microstructure–property analyses. This electron backscatter diffraction-based method for crystal-plasticity finite element model generation is shown to give approximately 10% improved agreement for fatigue life prediction, compared with the more commonly used Voronoi tessellation method. However, the added microstructural detail available in electron backscatter diffraction–crystal-plasticity finite element did not significantly alter the bulk stress–strain response prediction, compared to Voronoi tessellation–crystal-plasticity finite element. The new electron backscatter diffraction-based method within a strain-gradient crystal-plasticity finite element model is also applied to predict measured grain size effects for cyclic plasticity and fatigue crack initiation, and shows the concentration of geometrically necessary dislocations around true grain boundaries, with smaller grain samples exhibiting higher overall geometrically necessary dislocations concentrations. In addition, minimum model sizes for Voronoi tessellation–crystal-plasticity finite element and electron backscatter diffraction–crystal-plasticity finite element models are proposed for cyclic hysteresis and fatigue crack initiation prediction.

Download Full-text

Crack nucleation using combined crystal plasticity modelling, high-resolution digital image correlation and high-resolution electron backscatter diffraction in a superalloy containing non-metallic inclusions under fatigue

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2015.0792 ◽

2016 ◽

Vol 472 (2189) ◽

pp. 20150792 ◽

Cited By ~ 35

Author(s):

Tiantian Zhang ◽

Jun Jiang ◽

Ben Britton ◽

Barbara Shollock ◽

Fionn Dunne

Keyword(s):

Fatigue Crack ◽

Crystal Plasticity ◽

Electron Backscatter Diffraction ◽

Crack Nucleation ◽

Image Correlation ◽

Fatigue Crack Nucleation ◽

Resolution Electron ◽

Electron Backscatter ◽

Mechanistic Basis ◽

Backscatter Diffraction

A crystal plasticity finite-element model, which explicitly and directly represents the complex microstructures of a non-metallic agglomerate inclusion within polycrystal nickel alloy, has been developed to study the mechanistic basis of fatigue crack nucleation. The methodology is to use the crystal plasticity model in conjunction with direct measurement at the microscale using high (angular) resolution-electron backscatter diffraction (HR-EBSD) and high (spatial) resolution-digital image correlation (HR-DIC) strain measurement techniques. Experimentally, this sample has been subjected to heat treatment leading to the establishment of residual (elastic) strains local to the agglomerate and subsequently loaded under conditions of low cyclic fatigue. The full thermal and mechanical loading history was reproduced within the model. HR-EBSD and HR-DIC elastic and total strain measurements demonstrate qualitative and quantitative agreement with crystal plasticity results. Crack nucleation by interfacial decohesion at the nickel matrix/agglomerate inclusion boundaries is observed experimentally, and systematic modelling studies enable the mechanistic basis of the nucleation to be established. A number of fatigue crack nucleation indicators are also assessed against the experimental results. Decohesion was found to be driven by interface tensile normal stress alone, and the interfacial strength was determined to be in the range of 1270–1480 MPa.

Download Full-text

Damage Evaluation of Ferrite and Ferrite-Pearlite Steel during Fatigue Crack Initiation by EBSD

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.891-892.410 ◽

2014 ◽

Vol 891-892 ◽

pp. 410-415 ◽

Cited By ~ 5

Author(s):

Mamoru Hayakawa ◽

Masayuki Wakita ◽

Eisuke Nakayama

Keyword(s):

Fatigue Crack ◽

Crack Initiation ◽

Fatigue Testing ◽

Electron Backscatter Diffraction ◽

Fatigue Crack Initiation ◽

Ferrite Matrix ◽

Fatigue Tests ◽

Before And After ◽

Ferrite Steel ◽

Orientation Deviation

Orientation changes during fatigue crack initiation in ferrite and ferritepearlite steel were evaluated by electron backscatter diffraction (EBSD). Ferrite steel with different grain sizes and ferritepearlite steel with different carbon contents were prepared. EBSD measurements and fatigue tests were alternately performed using a small specimen. The tests on both ferrite and ferritepearlite steel suggest that the initial cracks were observed in the ferrite matrix. Thus, crystal rotation induced by fatigue in ferrite matrix is quantitatively evaluated by two misorientation parameters: grain reference orientation deviation, which is the misorientation between measuring points and the average orientation in each grain, and crystal misorientation at the same point before and after fatigue testing.

Download Full-text

On the mechanistic basis of fatigue crack nucleation in Ni superalloy containing inclusions using high resolution electron backscatter diffraction

Acta Materialia ◽

10.1016/j.actamat.2015.06.035 ◽

2015 ◽

Vol 97 ◽

pp. 367-379 ◽

Cited By ~ 41

Author(s):

Jun Jiang ◽

Jie Yang ◽

Tiantian Zhang ◽

Fionn P.E. Dunne ◽

T. Ben Britton

Keyword(s):

Fatigue Crack ◽

High Resolution ◽

Electron Backscatter Diffraction ◽

Crack Nucleation ◽

Fatigue Crack Nucleation ◽

Resolution Electron ◽

Electron Backscatter ◽

Mechanistic Basis ◽

Backscatter Diffraction

Download Full-text

The Effect of Phase Angle on the Thermo-Mechanical Fatigue Life of a Titanium Metal Matrix Composite

Materials ◽

10.3390/ma12060953 ◽

2019 ◽

Vol 12 (6) ◽

pp. 953

Author(s):

Ashley Dyer ◽

Jonathan Jones ◽

Richard Cutts ◽

Mark Whittaker

Keyword(s):

Crack Initiation ◽

Metal Matrix Composite ◽

Matrix Composite ◽

Metal Matrix ◽

Electron Backscatter Diffraction ◽

Fatigue Crack Initiation ◽

Test Results ◽

Phase Cycling ◽

Mechanical Fatigue ◽

Backscatter Diffraction

The thermo-mechanical fatigue (TMF) behaviour of a Ti-6Al-4V matrix composite reinforced with SCS-6 silicon carbide fibres (140 μm longitudinal fibres, laid up hexagonally) has been investigated. In-phase and out-of-phase TMF cycles were utilized, cycling between 80–300 °C, with varying maximum stress. The microstructure and fracture surfaces were studied using electron backscatter diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), profilometry, and optical microscopy. The results have shown the damaging effect of out-of-phase cycling with crack initiation occurring earlier than in in-phase tests and crack propagation rates being accelerated in out-of-phase cycles. Fatigue crack initiation has been shown to be sensitive to crystallographic texture in the cladding material and thermo-mechanical fatigue test results can be considered according to a previously proposed conceptual framework for the interpretation of metal matrix composite fatigue.

Download Full-text

The effect of microtexture evaluated by electron backscatter diffraction method on fatigue crack propagation behaviour in rolled copper film

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1111/j.1460-2695.2005.00863.x ◽

2005 ◽

Vol 28 (1-2) ◽

pp. 221-227 ◽

Cited By ~ 8

Author(s):

K. SHIMIZU ◽

T. TORII

Keyword(s):

Fatigue Crack ◽

Crack Propagation ◽

Fatigue Crack Propagation ◽

Electron Backscatter Diffraction ◽

Copper Film ◽

Diffraction Method ◽

Electron Backscatter ◽

Backscatter Diffraction

Download Full-text

Early slip activity and fatigue crack initiation of a near alpha titanium alloy

MATEC Web of Conferences ◽

10.1051/matecconf/202032111040 ◽

2020 ◽

Vol 321 ◽

pp. 11040

Author(s):

Conghui Liu ◽

Rhys Thomas ◽

João Quinta da Fonseca ◽

Michael Preuss

Keyword(s):

Fatigue Crack ◽

Crack Initiation ◽

Electron Backscatter Diffraction ◽

Fatigue Crack Initiation ◽

High Stress ◽

Load Ratio ◽

Bending Test ◽

Plastic Slip ◽

Slip Activity ◽

Alpha Titanium

For titanium alloys, crack initiation as a result of plastic strain accumulation has been shown to govern fatigue life under the high cycle fatigue regime. In this study, the early plastic slip activity and fatigue crack initiation was studied using a cyclic four point bending test at 10 Hz with a load ratio of 0.1, up to 90% of the proof stress. The plastic slip in the high stress area was monitored by interrupting the test and performing optical microscopy. Following fatigue crack initiation, scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD) was used to identify the slip and crack initiation mode in a 600 x 600 μm2 area. Using slip trace analysis, it was shown that primary alpha grains offered dominant plastic deformation with basal slip activation. Cracking along basal planes was determined to be the dominant damage mode.

Download Full-text