Particle Orientation and Its Relationship to Casting Behavior and Casting Faults

2008 ◽  
pp. 1220-1230
Author(s):  
Derek Basnett
Keyword(s):  
Particle Orientation

Characteristic Geometry and Diffraction Contrast of Dispersed ThO2 Crystals

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.

New challenges to image processing posed by cryo-Electron microscopy of single particles

1991 ◽  
Vol 49 ◽  
pp. 422-423
Author(s):  
Joachim Frank
Keyword(s):  
Electron Microscopy ◽  
Phase Contrast ◽  
Particle Orientation ◽  
Single Particles ◽  
Contrast Transfer Function ◽  
Virtual Absence ◽  
Cryo Electron Microscopy ◽  
Spatial Frequencies ◽  
New Challenges ◽  
Particle Images

Compared with images of negatively stained single particle specimens, those obtained by cryo-electron microscopy have the following new features: (a) higher “signal” variability due to a higher variability of particle orientation; (b) reduced signal/noise ratio (S/N); (c) virtual absence of low-spatial-frequency information related to elastic scattering, due to the properties of the phase contrast transfer function (PCTF); and (d) reduced resolution due to the efforts of the microscopist to boost the PCTF at low spatial frequencies, in his attempt to obtain recognizable particle images.

scholarly journals An X-ray CT study of miniature clay sample preparation techniques

2019 ◽  
Vol 92 ◽  
pp. 01004
Author(s):  
Christopher Ibeh ◽  
Matteo Pedrotti ◽  
Alessandro Tarantino ◽  
Rebecca Lunn
Keyword(s):  
Sample Preparation ◽  
Shear Plane ◽  
Cohesive Soil ◽  
Image Resolution ◽  
Particle Orientation ◽  
X Ray ◽  
High Resolution Images ◽  
X Ray Computed ◽  
Sample Disturbance ◽  
Relationship Of

The quality and reliability of cohesive soil laboratory test data can be significantlyaffected by sample disturbance during sampling or sample preparation. Sample disturbance may affect key design and modelling parameters such as stiffness, preconsolidation stress, compressibility and undrained shear strength, and ultimately determine particle mobilization and shear plane development. The use of X-ray computed tomography (X-CT) in the study of soil is restricted by the inverse relationship of specimen size and obtainable image resolution. This has led to the testing of miniature specimen sizes which are far less than conventional laboratory sample size in a bid to obtain high resolution images and detailed particle-scale soil properties; however, these miniature soil specimens are more prone to sample disturbance. In this work 2% muscovite was mixed with speswhite kaolin clay as a strain marker for use in X-CT. The clay soil sample was prepared from slurry and either consolidated using an oedometer or a gypsum mould. Specimens obtained from a 7 mm tube sampler were compared to lathe trimmed specimens with a diameter (Ø) of 7 mm. Results from X-CT imaging were used to study the influence of sampler type on specimen disturbance, by analysing the muscovite particle orientation of the obtained 3D images. The results show that; for samples subjected to large consolidation stress (>200kpa) lathe trimmed specimens may be subject to lesser disturbance compared to tube sampled specimens.

Rock Failure Under Dynamic Loading Conditions

1963 ◽  
Vol 3 (01) ◽  
pp. 1-8 ◽  
Author(s):  
N.T. Burdine
Keyword(s):  
The State ◽  
Cumulative Damage ◽  
Material Behavior ◽  
Particle Orientation ◽  
Loading Conditions ◽  
Hooke’S Law ◽  
Rock Samples ◽  
Cyclic Stresses ◽  
Hooke's Law ◽  
Failure Theories

BURDINE, N.T., SOCONY MOBIL OIL CO., INC., DALLAS, TEX Abstract The present investigation is concerned with the cumulative damage to rock samples when exposed to cyclic stresses under various loading conditions. Information on the response of rocks to repetitive deformational forces is an essential prerequisite to an understanding of the fundamentals of drilling. Using a laboratory designed and constructed dynamic-stress apparatus, preliminary data were obtained on cylindrical rock samples. The experiments consist of measuring the number of cycles to failure for a given axial load ( static plus dynamic). Data were obtained for various confining and pore pressures, pore fluids (air and water), frequencies of stress application and loading procedures. The results are related to failure theories and dynamic fatigue properties of other materials. Introduction In most conventional and new drilling processes, repetitive forces are applied to the bottom of the borehole. Furthermore, in hard-rock drilling the number of applications of the forces to a particular section of rock may become excessively large. The present investigation is concerned with the cumulative damage to rocks when exposed to cyclic stresses under various loading conditions. It is believed that the experiments will lead to a better understanding of the mechanical response of rocks to particular deformational forces and to a more efficient drillingprocedure.Thepresent investigation is the initial part of a general study of the behavior of inelastic materials under static and dynamic conditions, including both theoretical and experimental studies. SURVEY OF FAILURE THEORIES OF MATERIALS Few, even phenomenological, theories on rock deformation have been established because the state of knowledge of flow, fracture and strength of rocks is largely empirical. Most of the theories that do exist were originally formulated for other materials. HOOKE'S LAW The state of stress in continuous media is completely determined by the stress tensor and the state of deformation by the strain tensor . In the linear theory of elasticity the generalized Hooke's law is ..........................(1) where the coefficients are the components of the elasticity tensor. For homogeneous and isotropic conditions the number of independent coefficients reduce to two, and Eq. 1 becomes ..................(2) in which and are Lame's constants; is the kronecker delta; and is the dilation. This simplified version of Hooke's law has been used quite extensively in geophysical research where most of the information about the mechanical properties of the earth have been obtained. However, it has only limited application in rock fatigue studies. MATERIAL BEHAVIOR Many solids obey Hooke's law at small stresses, but for higher stresses a hysteretic effect occurs due to temporary or permanent residual deformation of the solid (inelastic deformation). Such deviations in mechanical behavior exist in varying degrees in different classes of materials. Most elastic materials have a microscopic heterogeneity due either to random distribution of anisotropic particles, or due to some preferred particle orientation, or both. Other materials are quite grossly heterogeneous. And the method of formation, particularly in rocks, oftentimes creates residual stress concentrations which have complicated states of imperfect equilibrium. Also, the thermal effects resulting from structural behavior give rise to nonuniform temperature distributions and the degradation of mechanical energy. When such bodies are exposed to certain large loading conditions, the inelastic behavior is intensified so strongly that the deformation, normally brittle, becomes ductile. SPEJ P. 1^

scholarly journals Characterization of proteoglycan and the proteoglycan-hyaluronic acid complex by electric birefringence

1978 ◽  
Vol 173 (1) ◽  
pp. 237-243 ◽  
Author(s):  
M Isles ◽  
A R Foweraker ◽  
B R Jennings ◽  
T Hardingham ◽  
H Muir
Keyword(s):  
Hyaluronic Acid ◽  
Particle Orientation ◽  
Dilute Solution ◽  
Relaxation Rates ◽  
Acid Complex ◽  
Electric Birefringence ◽  
Partial Alignment ◽  
Uronic Acid Content ◽  
Birefringence Relaxation

An electric field causes partial alignment of macromolecules in a dilute solution. The accompanying changes in the solution birefringence offer a sensitive and quick means of monitoring the rates of particle orientation and hence the size of the solute molecules. Such measurements are reported for dilute solutions of proteoglycans in the absence and presence of added hyaluronic acid. The proteoglycan molecules are shown to be some 580 nm long. In the presence of hyaluronic acid they form aggregates that appear to be consistent with the model previously proposed in which the proteoglycans attach radially to the extended hyaluronic acid chain. The electric-birefringence relaxation rates indicate aggregates of similar length to that of the extended hyaluronic acid chain, with the proteoglycans spaced on average at 29nm intervals. A proteoglycan sample the cystine residues of which had been reduced and alkylated showed no evidence of aggregation with hyaluronic acid up to the concentrations of the acid corresponding to 1% of the total uronic acid content. The electric-birefringence method is shown to have a large potential in the study of associating polysaccharide solutions.

scholarly journals Larch (Larix decidua) bark insulation board: interactions of particle orientation, physical–mechanical and thermal properties

2017 ◽  
Vol 76 (2) ◽  
pp. 489-498 ◽  
Author(s):  
Günther Kain ◽  
Bernhard Lienbacher ◽  
Marius-Catalin Barbu ◽  
Klaus Richter ◽  
Alexander Petutschnigg
Keyword(s):  
Thermal Properties ◽  
Larix Decidua ◽  
Particle Orientation ◽  
Mechanical And Thermal Properties

Rigid-Plastic Impact of Single Angular Particles

2021 ◽  
Author(s):  
Sandeep Dhar
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Element Model ◽  
Orientation Dependence ◽  
Particle Orientation ◽  
Rigid Plastic ◽  
Plastic Model ◽  
Model Predictions ◽  
Good Agreement ◽  
Angular Particles

The trajectory of an angular particle as it cuts a ductile target is, in general, complicated because of its dependence not only on particle shape, but also on particle orientation at the initial instant of impact. This orientation dependence has also made experimental measurement of impact parameters of single angular particles very difficult, resulting in a relatively small amount of available experimental data in the literature. The current work is focused on obtaining measurements of particle kinematics for comparison to rigid plastic model developed by Papini and Spelt. Fundamental mechanisms of material removal are identified, and measurements of rebound parameters and corresponding crater dimensions of single hardened steel particles launched against flat aluminium alloy targets are presented. Also a 2-D finite element model is developed and a dynamic analysis is performed to predict the erosion mechanism. Overall, a good agreement was found among the experimental results, rigid-plastic model predictions and finite element model predictions.

scholarly journals Effect of particle orientation on the diffusion of water in the dual porosity of vermiculite porous media

2021 ◽  
Author(s):  
Ali Asaad ◽  
Emmanuel Tertre ◽  
Fabien Hubert ◽  
Eric Ferrage ◽  
Thomas Dabat ◽  
...  
Keyword(s):  
Porous Media ◽  
Particle Orientation ◽  
Dual Porosity
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