Quantification of strain fields and grain refinement in Ti-6Al-4V inter-pass rolled wire-arc AM by EBSD misorientation analysis

1969 ◽

Vol 27 ◽

pp. 168-169

Author(s):

R. J. Horylev ◽

L. E. Murr

Keyword(s):

Dark Field ◽

Particle Orientation ◽

Contrast Effects ◽

Strain Fields ◽

Diffraction Contrast ◽

Dispersed Particles ◽

Field Electron Microscopy ◽

Dark Field Electron ◽

Particle Images ◽

Diffraction Effects

Smith has shown by dark-field electron microscopy of extracted ThO2 particles from TD-nickel (2% ThO2) that they possess single crystal characteristics. It is generally assumed that these particle dispersions are incoherent. However, some diffraction effects associated with the particle images appeared to be similar to coherency strain fields. The present work will demonstrate conclusively that ThO2 dispersed particles in TD-nickel (2% ThO2) and TD-NiCr (2% ThO2, 20% Cr, Ni) are single crystals. Moreover, the diffraction contrast effects are extinction fringes. That is, these effects arise because of the particle orientation with respect to the electron beam and the extinction conditions for various operating reflections The particles are in fact incoherent.

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Grain Refinement in Titanium-Erbium Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052626 ◽

1974 ◽

Vol 32 ◽

pp. 522-523

Author(s):

B. B. Rath ◽

J. E. O'Neal ◽

R. J. Lederich

Keyword(s):

Electron Microscopy ◽

Size Distribution ◽

Grain Refinement ◽

Grain Growth ◽

Volume Fraction ◽

Pure Titanium ◽

Systematic Investigation ◽

Second Phase ◽

Titanium Matrix ◽

Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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Effect of strain on ADF-STEM high-resolution images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087641 ◽

1991 ◽

Vol 49 ◽

pp. 666-667

Author(s):

M. Kelly ◽

D.M. Bird

Keyword(s):

High Resolution ◽

Strong Influence ◽

Intensity Variation ◽

Dark Field ◽

Atomic Resolution ◽

Strain Fields ◽

High Resolution Image ◽

Annular Dark Field ◽

High Resolution Images ◽

Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

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Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010008866x ◽

1991 ◽

Vol 49 ◽

pp. 870-871

Author(s):

P.M. Rice ◽

MJ. Kim ◽

R.W. Carpenter

Keyword(s):

Colony Growth ◽

Dark Field ◽

Dark Side ◽

Silicide Phase ◽

Strain Fields ◽

Near Surface ◽

Unknown Composition ◽

Secondary Precipitates ◽

20 Nm ◽

2D And 3D

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

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Delamination in the scoring and folding of paperboard

TAPPI Journal ◽

10.32964/tj11.1.61 ◽

2012 ◽

Vol 11 (1) ◽

pp. 61-66 ◽

Cited By ~ 1

Author(s):

DOEUNG D. CHOI ◽

SERGIY A. LAVRYKOV ◽

BANDARU V. RAMARAO

Keyword(s):

Finite Element ◽

Plane Deformation ◽

Strain Analysis ◽

Local Strain ◽

Uniaxial Stress ◽

Material Model ◽

Element Model ◽

Plastic Behavior ◽

Stress Strain ◽

Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

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Mathematical Model of the Effective Properties of a Fiber Reinforced Composite with a Linearly Graded Transition Zone

Tire Science and Technology ◽

10.2346/1.3519536 ◽

2010 ◽

Vol 38 (4) ◽

pp. 286-307

Author(s):

Carey F. Childers

Keyword(s):

Mathematical Model ◽

Transition Zone ◽

Effective Properties ◽

Local Stress ◽

Stress And Strain ◽

Fiber Reinforced ◽

Strain Fields ◽

Shear Moduli ◽

Fiber Reinforced Composite ◽

Reinforced Composite

Abstract Tires are fabricated using single ply fiber reinforced composite materials, which consist of a set of aligned stiff fibers of steel material embedded in a softer matrix of rubber material. The main goal is to develop a mathematical model to determine the local stress and strain fields for this isotropic fiber and matrix separated by a linearly graded transition zone. This model will then yield expressions for the internal stress and strain fields surrounding a single fiber. The fields will be obtained when radial, axial, and shear loads are applied. The composite is then homogenized to determine its effective mechanical properties—elastic moduli, Poisson ratios, and shear moduli. The model allows for analysis of how composites interact in order to design composites which gain full advantage of their properties.

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Computational Models for Multilayered Composite Shells with Application to Tires

Tire Science and Technology ◽

10.2346/1.2137509 ◽

1996 ◽

Vol 24 (1) ◽

pp. 11-38 ◽

Cited By ~ 10

Author(s):

G. M. Kulikov

Keyword(s):

Type Theory ◽

Computational Models ◽

Geometrical Nonlinearity ◽

Higher Order ◽

Stress Strain ◽

Strain Fields ◽

First Order ◽

Timoshenko Type ◽

Joint Influence ◽

Discrete Layer

Abstract This paper focuses on four tire computational models based on two-dimensional shear deformation theories, namely, the first-order Timoshenko-type theory, the higher-order Timoshenko-type theory, the first-order discrete-layer theory, and the higher-order discrete-layer theory. The joint influence of anisotropy, geometrical nonlinearity, and laminated material response on the tire stress-strain fields is examined. The comparative analysis of stresses and strains of the cord-rubber tire on the basis of these four shell computational models is given. Results show that neglecting the effect of anisotropy leads to an incorrect description of the stress-strain fields even in bias-ply tires.

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