Multiscale strain measurements of plastically deforming polycrystalline titanium: Role of deformation heterogeneities

Efstathiou, C.; Şehitoğlu, Hüseyin; Lambros, John

doi:10.1016/j.ijplas.2009.04.006

Cited by 129 publications

(84 citation statements)

References 47 publications

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“…This in principle enables one to compare the true level of strain heterogeneity for different alloys, microstructures and microstructure inhomogeneity. Previous studies using optically based DIC have concentrated on strain localisation at the microscale, reporting maximum strain concentrations ranging between 2-3.5 times the average strain [20,21] when strain hot spots are compared to the average strain. By utilising the gold remodelling technique to produce nanoscale patterns in combination SEM imaging in the present work, it is now possible to gain an understanding of the strain concentrations that occur across a single grain and variations in strain across several grains.…”

Section: Discussionmentioning

confidence: 99%

Slip Band Characterisation in Ti‐6Al‐4V with Varying Degrees of Macrozones

Lunt

Fonseca

Rugg

et al. 2016

Proceedings of the 13th World Conference on Titanium

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Electron Backscatter Diffraction (EBSD) orientation maps and Digital Image Correlation (DIC) was combined to analyse slip trace formation of Ti-6Al-4V with varying degrees of microstructural inhomogeneity. The focuses of the study are three products forms of Ti-6Al-4V that are strong-macrozone, intermediate-macrozone and no-macrozone material that were loaded to study the impact of the primary macrozone orientation on strain localisation. Strain localisation was characterised at the nanoscale by a applying a fine speckle pattern to the sample surface using the Gold remodelling technique. All materials exhibited a proportion of grains that exhibited high intensity planar slip traces, neighbouring regions within the same grain showed little deformation. In the no-macrozone material the majority of grains deformed but the level of transgranular strain remained relatively constant across the material. For the intermediate-macrozone condition, macrozones with their caxis parallel to the loading direction resulted in grains that did not deform and the neighbouring grains that had favourable orientations for easy slip showed highly planar strain slip traces. The strain map of the strong-macrozone condition loaded at 45 to the extrusion direction (ED) showed that a pronounced high strain band developed in the macrozone region. The primary crystallographic orientation of the macrozone had the c-axis perpendicular to the loading direction and the likely activated slip system was prismatic slip. There were higher overall transgranular strains across the macrozone region compared to the neighbouring region, which displays greater misorientation between grains. The 45 loading direction of the strong-macrozone condition produced finer slip trace spacing and more intense strain heterogeneity and increased localised deformation than the no-macrozone condition

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Section: Discussionmentioning

confidence: 99%

Slip Band Characterisation in Ti‐6Al‐4V with Varying Degrees of Macrozones

Lunt

Fonseca

Rugg

et al. 2016

Proceedings of the 13th World Conference on Titanium

View full text Add to dashboard Cite

show abstract

“…DIC, on the other hand, is more forgiving in terms of experimental requirements, which opens up possibilities for both ex situ and in situ measurements at different length scales, once appropriate random patterns are generated on the surface of a specimen. Generally, ex situ DIC can provide measurements at higher resolution [21][22][23]. However, it can only be done post-mortem, hence only residual deformation can be measured.…”

Section: Introductionmentioning

confidence: 99%

In Situ Experimental Study of Near-Tip Strain Evolution of Fatigue Cracks

Lupton

Zhu

et al. 2015

Exp Mech

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Near crack tip strain fields in a stationary and a growing fatigue crack have been studied in situ using the Digital Image Correlation (DIC) technique in a compact tension specimen of stainless steel 316 L under tensiontension cyclic loading. The evolution of near-tip strains normal to the crack plane was monitored at selected locations ahead of the crack tip in consecutive cycles during fatigue crack growth experiments. A stationary crack was examined first to provide a baseline reference whilst the evolution of the strain field ahead of a growing crack was monitored in situ at peak loads during fatigue cycling. The results show that strain accumulation with loading cycle occurred at all tracked locations in both cases, and it is particularly evident close to the crack tip. Moreover, a higher strain accumulation rate was found near the growing crack tip than that near the stationary crack tip. The results on near-tip strain evolution were collected for the first time in situ during the fatigue crack growth experiments, which may hopefully inform a physical-based modelling strategy of fatigue crack growth.

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“…Typically the displacement resolution and subset size limit this technique to measurements of plastic strain fields [8]. DIC has been used to investigate damage nucleation associated with microstructures and has been conducted in Ti alloys [9,10], as well as nickel based superalloy Hastelloy X [11], and recent developments of the technique are reviewed in [8].…”

mentioning

confidence: 99%

Slip localization and fatigue crack nucleation near a non-metallic inclusion in polycrystalline nickel-based superalloy

Zhang

Jiang

Shollock

et al. 2015

Materials Science and Engineering: A

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Fatigue crack nucleation at a non-metallic agglomerate inclusion has been studied by high spatial resolution Digital Image Correlation (HR-DIC) and high angular resolution Electron Backscatter Diffraction (HR-EBSD). Spatial and temporal characterization and correlation of deformation with underlying microstructures has been performed, with distributions of plastic strain measured from HR-DIC; and residual stress and density of geometrically necessary dislocations (GND) measured from HR-EBSD. Initial residual stress and GND fields, as a consequence of differing thermal expansivities in the metallic and oxide phases, localized around the agglomerate have been quantified using HR-EBSD. The localization of the pre-existing stress and dislocation states appear to lead to early onset of plasticity upon subsequent mechanical loading. Heterogeneous distributions of plastic strain have been observed in the course of the fatigue test by HR-DIC. Crack nucleation via agglomerate/nickel interface decohesion and particle fracture has been demonstrated and this is correlated with the elevation in strain and dislocation density. The measurements of residual stress, strain, and dislocation density provide key information for the mechanisms of fatigue cracking and the development of damage nucleation criteria in these material systems.2

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Multiscale strain measurements of plastically deforming polycrystalline titanium: Role of deformation heterogeneities

Cited by 129 publications

References 47 publications

Slip Band Characterisation in Ti‐6Al‐4V with Varying Degrees of Macrozones

Slip Band Characterisation in Ti‐6Al‐4V with Varying Degrees of Macrozones

In Situ Experimental Study of Near-Tip Strain Evolution of Fatigue Cracks

Slip localization and fatigue crack nucleation near a non-metallic inclusion in polycrystalline nickel-based superalloy

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