MECHANICAL PROPERTIES OF GRAIN CONTACTS IN UNCONSOLIDATED SANDS

Geophysics ◽  
2020 ◽  
pp. 1-39
Author(s):  
Colin M. Sayers
Keyword(s):  
Mechanical Properties ◽  
Confining Pressure ◽  
High Porosity ◽  
Hydrocarbon Production ◽  
Unconsolidated Sands ◽  
Porosity And Permeability ◽  
Freshwater Aquifers ◽  
Shear Compliance

Unconsolidated sands provide zones of high porosity and permeability important for freshwater aquifers, hydrocarbon production and CO2 sequestration. An understanding of the acoustics of unconsolidated sands enables the characterization of such formations using ultrasonics, borehole acoustics and seismic methods. Inversion of ultrasonic compressional and shear velocities measured for unloading as a function of confining pressure for room-dry unconsolidated sands allows information on the mechanical properties of the grain contacts to be obtained using an approach based on the divergence theorem. This allows the effective compliance of sand to be written as the sum of the compliance of the pores and of the grain contacts and does not assume that the grains are identical spheres, in contrast to previous approaches. Grain contacts are found to be more compliant under shear than under normal compression, and the ratio of the normal-to-shear compliance decreases with decreasing confining pressure, implying that the shear compliance increases faster with decreasing confining pressure than the normal compliance. This is of importance in understanding the role of shear in the failure of unconsolidated sands, such as occurs in shallow water flow, sanding and failure around injectors, where the change in stress is a function of the ratio of the normal-to-shear compliance ratio of the grain contacts.

Mesoporous titania-embedded polyacrylonitrile composite nanofibrous membrane for particulate matter filtration

2019 ◽  
pp. 089270571985992
Author(s):  
P Reena ◽  
N Gobi ◽  
P Chitralekha ◽  
D Thenmuhil ◽  
V Kamaraj
Keyword(s):  
Particulate Matter ◽  
Composite Membrane ◽  
Weight Ratio ◽  
Composite Membranes ◽  
Areal Density ◽  
Mesoporous Titania ◽  
High Porosity ◽  
Homogenous Distribution

In the present work, mesoporous titania (MT)-embedded polyacrylonitrile (PAN) nanofibrous membranes have been developed and studied for their efficiency in particulate matter (PM) filtration. Using Box–Behnken method, 15 nanofibrous composite membranes were obtained through electrospinning by choosing three different process variables, such as MT (weight ratio), areal density (g m−2), and spinning time (h). The characterization of resulted nanofibrous composite membranes revealed that the homogenous distribution of MT (2.9 nm) within the PAN delivers high porosity as well as air permeability. Further, filtration efficiency (FE) was also analyzed for PM from 0.3 µm to 3 µm. PM filtration studies suggested that the nanofibrous composite membrane developed from 15% MT, spin time of 2 h, and areal density of 80 g m−2 possesses overall efficiency of 96.4%, without pressure drop for the composite. The results suggest that the role of MT was found to be significant in achieving successful filtration of PM. In addition to successful FE, the desirability value of the developed composite was also calculated statistically and the optimized composite membrane was identified.

Misestimation of the ITZ Thickness around Non-Spherical Aggregates

2021 ◽  
Vol 1036 ◽  
pp. 432-441
Author(s):  
Ming Qi Li ◽  
Hui Su Chen
Keyword(s):  
Mechanical Properties ◽  
Cross Section ◽  
Linear Analysis ◽  
Interfacial Transition Zone ◽  
High Porosity ◽  
Two Dimensional ◽  
One Dimensional ◽  
3D Microstructure ◽  
Porosity And Permeability ◽  
Very High

The ITZ (interfacial transition zone) in concrete has very high porosity and permeability, which affects concrete’s macroscopic mechanical properties and transport properties. Two-dimensional (2D) areal analysis and one-dimensional (1D) linear analysis are usually used to study ITZ’s microstructure. However, 3D microstructure is difficult to be characterized by 1D and 2D information. For example, 2D cross-section planes do not always intercept both the ITZ and the corresponding aggregate, which causes some ITZ regions are ignored by researchers. Therefore, ITZ’s volume and thickness will be misestimated, and leads to the misestimation of the diffusivity. In this paper, the effect of aggregate’s shape on the misestimation of ITZ thickness t is studied. The results reveal that the misestimation increases with the increasing sphericity s of aggregates.

Characterization of Modified Multiwalled Carbon Nanotubes

2014 ◽  
Vol 925 ◽  
pp. 369-373
Author(s):  
Rahmam Syuhaidah ◽  
Norani Muti Mohamed ◽  
Suriati Sufian
Keyword(s):  
Sulfuric Acid ◽  
Functional Group ◽  
High Surface ◽  
High Surface Area ◽  
High Porosity ◽  
Multiwalled Carbon ◽  
Direct Functionalization ◽  
Amine Functional Group

Unique characteristics of MWCNT such as high porosity and high surface area make MWCNT as potential material to be explored in-depth through research. The role of MWCNT as CO2 adsorbent will be more efficient after modification with 3-Aminopropyl triethoxysilane (APTS) in order to obtain amine functional group. However, direct functionalization is not permissible due to the hydrophobic problem faced by pristine MWCNT. This complication can be resolved by liquid oxidation treatment using different types of oxidants such as nitric acid (HNO3), sulfuric acid (H2SO4), and mixture of nitric and sulfuric acid (HNO3/H2SO4). The characteristics of pristine MWCNT and modified MWCNT were investigated by analyzing the samples using scanning electron microscopy and energy dispersive X-ray spectroscopy (FESEM-EDXs), fourier transform infra-red (FTIR), and Raman spectroscopy technique. Higher degree of functionalization implies higher attachment of amine functional group for higher CO2 adsorption. Here, MWCNT sample treated with HNO3/H2SO4 and APTS recorded the highest degree of functionalization.

scholarly journals Experimental Study on Physical Mechanical Properties and Microstructure of Diatomite Soil in Zhejiang Province, China

2021 ◽  
Vol 12 (1) ◽  
pp. 387
Author(s):  
Lei Gao ◽  
Yi Luo ◽  
Yingeng Kang ◽  
Mingjun Gao ◽  
Omar Abdulhafidh
Keyword(s):  
Mechanical Properties ◽  
Strain Curve ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Confining Pressure ◽  
Zhejiang Province ◽  
Dry Density ◽  
High Porosity ◽  
Engineering Project ◽  
Geotechnical Tests

Diatomite soil is a kind of bio-siliceous soil with complex composition and special structure, the physical and mechanical properties of diatomite soil are very important for the engineering project. In this paper, the physical properties, mechanical properties, and microstructure of diatomite soil in Zhejiang Province are studied by geotechnical tests and microscopic tests from the macroscopic and microscopic perspective. The results show that: (1) The diatomite soil has special properties different from other soils, including small particle size, low specific gravity value, high liquid-plastic limit, and low compressibility, and the strength indexes c and φ of diatomite soil will decrease with an increase in soil water content; (2) in the triaxial test, when the dry density of diatomite soil increases from 1.30 g/cm3 to 1.50 g/cm3, the effective internal friction angle of diatomite soil increases from 5.6° to 14.5° and the effective cohesion increases from 30.9 kPa to 49.6 kPa. The stress–strain curve of diatomite soil changes from weak softening type to weak hardening type when the confining pressure is above 200 kPa; (3) the diatomite soil has high porosity due to its unique microstructure; it is rich in aluminum oxides and minerals, which will greatly reduce the engineering performance of diatomite soil.

scholarly journals Development and Multiscale Characterization of 3D Warp Interlock Flax Fabrics with Different Woven Architectures for Composite Applications

Fibers ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 15 ◽  
Author(s):  
Henri Lansiaux ◽  
Damien Soulat ◽  
François Boussu ◽  
Ahmad Rashed Labanieh
Keyword(s):  
Mechanical Properties ◽  
Natural Fibers ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Woven Fabrics ◽  
Flax Fiber ◽  
Raw Material ◽  
Mechanical Tensile

Multiscale characterization of the textile preform made of natural fibers is an indispensable way to understand and assess the mechanical properties and behavior of composite. In this study, a multiscale experimental characterization is performed on three-dimensional (3D) warp interlock woven fabrics made of flax fiber on the fiber (micro), roving (meso), and fabric (macro) scales. The mechanical tensile properties of the flax fiber were determined by using the impregnated fiber bundle test. The effect of the twist was considered in the back-calculation of the fiber stiffness to reveal the calculation limits of the rule of mixture. Tensile tests on dry rovings were carried out while considering different twist levels to determine the optimal amount of twist required to weave the flax roving into a 3D warp interlock. Finally, at fabric-scale, six different 3D warp interlock architectures were woven to understand the role of the architecture of binding rovings on the mechanical properties of the dry 3D fabric. The results reveal the importance of considering the properties of the fiber and roving at these scales to determine the more adequate raw material for weaving. Further, the characterization of the 3D woven structures shows the preponderant role of the binding roving on their structural and mechanical properties.

scholarly journals A new hyperelastic model for the multi-axial deformation of blood clots occlusion in vessels

2020 ◽  
Author(s):  
Behrooz Fereidoonnezhad ◽  
Kevin Mattheus Moerman ◽  
Sarah Johnson ◽  
Ray McCarthy ◽  
Patrick McGarry
Keyword(s):  
Mechanical Properties ◽  
Axial Deformation ◽  
Proposed Model ◽  
Nonlinear Stress ◽  
Blood Clots ◽  
Hyperelastic Model

Mechanical thrombectomy can be significantly affected by the mechanical properties of the occluding thrombus. In this study we provide the first characterization of the volumetric behaviour of blood clots. We propose a new hyperelastic model for the volumetric and isochoric deformation of clot. We demonstrate that the proposed model provides significant improvements over established models in terms of accurate prediction of nonlinear stress-strain and volumetric behaviours of low and high haematocrit clots. We perform a rigorous investigation of the factors that govern clot occlusion of a tapered vessel. The motivation for such an analysis is two-fold: (i) the role of clot composition on the in-vivo occlusion location is an open clinical question that has significant implications for thrombectomy procedures; (ii) in-vitro measurement of occlusion location in an engineered tapered tube can be used as a quick and simple methodology to assess the mechanical properties/compositions of clots. Simulations demonstrate that both isochoric and volumetric behaviour of clots are key determinants of clot lodgement location, in addition to clot-vessel friction. The proposed formulation is shown to provide accurate predictions of in-vitro measurement of clot occlusion location in a silicone tapered vessel, in addition to accurately predicting the deformed shape of the clot.

scholarly journals Synthesis and Characterization of Ni-P-Ti Nanocomposite Coatings on HSLA Steel

2020 ◽  
Author(s):  
Khuram Shahzad ◽  
Eman Mohamed Abdelkhalek Fayyad ◽  
Malik Adeel Umer ◽  
Osama Fayyaz ◽  
Tooba Qureshi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Oil And Gas ◽  
Composite Coatings ◽  
Hsla Steel ◽  
High Strength ◽  
Nanocomposite Coatings ◽  
Superior Mechanical Properties ◽  
P Matrix

Nickel phosphorus (Ni-P) coatings possess tailored mechanical and anticorrosion properties and have found applications in industries like automotive, oil and gas, electronics, and aerospace. Their properties can further be enhanced by incorporating nanoparticles into their (Ni-P) matrix. In the present study, Ni-P-Ti nanocomposite coatings have been developed on high strength low alloy steel (HSLA) through electroless deposition technique. For this purpose, various concentrations of titanium (Ti) nanoparticles are used in the deposition bath containing 0.0g/L, 0.25g/L, 0.5g/L, 0.75g/L, and 1.0g/L nanoparticles. XDR, SEM, microhardness, and nanoindentation have been carried out to elucidate the role of Ti nanoparticle concertation on the microstructure and mechanical properties of the Ni-P-Ti composite coatings. XRD and EDX results confirm the incorporation of nanoparticles into the Ni-P matrix during deposition processing. SEM and AFM results exhibit the formation of a dense, uniform coating without any observable defects. An increase in the mechanical properties of the Ni-P matrix was observed by the addition of Ti nanoparticles. Superior mechanical properties were shown by the samples containing 0.5g/L Ti nanoparticle concentration. Improvement in the structural, as well as mechanical properties of Ni- P matrix by the addition of Ti, confirms the suitability of Ni-P-Ti composite coatings for various engineering applications.

scholarly journals New insights into the mutable collagenous tissue of Paracentrotus lividus: preliminary results*

Zoosymposia ◽  
2012 ◽  
Vol 7 (1) ◽  
pp. 279-285 ◽  
Author(s):  
SERENA TRICARICO ◽  
ALICE BARBAGLIO ◽  
NEDDA BURLINI ◽  
LUCA DEL GIACCO ◽  
ANNA GHILARDI ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Biochemical Characterization ◽  
Paracentrotus Lividus ◽  
Preliminary Results ◽  
Structural Conformation ◽  
Collagenous Tissue ◽  
External Stimuli ◽  
Biomolecular Analysis

The mechanically adaptable connective tissue of echinoderms (Mutable Collagenous Tissue—MCT), which can undergo drastic nervously-mediated changes in mechanical properties, represents a promising model for biomaterial design and biomedical applications. MCT could be a source of, or an inspiration for, new composite materials whose molecular inter­actions and structural conformation can be changed in response to external stimuli. MCT is composed mostly of collagen fibrils, comparable to those of mammals, plus a variety of other components, including other fibrillar structures, proteo­glycans and glycoproteins. This contribution presents the preliminary results of a detailed analysis of MCT components in the sea-urchin Paracentrotus lividus, focusing on biochemical characterization of the fibrils and biomolecular analysis of the presumptive glycoproteins involved. The final aims will be to confirm the presence and the role of these glycoproteins in echinoids and to manipulate simpler components in order to produce a composite with mutable mechanical properties.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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