Increase In Relative Density Research Articles

Liquefaction Resistance of Sand Mixed with Fines-Grained for Reclaimed Land

Liquefaction due to earthquakes can cause collapse, subsidences, landslides, lateral spreading, and sand boiling. The damage is commonly occurred at layer of water-saturayed granular sedimen with low relative density. Reclamation areas formed by loose sand are areas with high risk to liquefaction, such as damages occured in the reclamation area of Tokyo Bay Area (Fukushima Earthquake, 2011) and Wellington Port (New Zealand Earthquake, 2016). Some researches have stated that the gradation of soil grains, relative density and maximum acceleration of an earthquake affected the soil’s resistance to liquefaction. This paper presents the results of the experimental studies about the influence of fines-grained in the sand that has liquefaction potential which is used as a reclamation material to review its resistance to liquefaction. The experimental studies were carried out by adding fines-grained. A mixture of sand with fines-grains was made at a relative density of 25%, 50% and 75% under earthquake load with a maximum acceleration of 0.3g. Experimental results show that the increase in the fines content up to 30% and the relative density up to 75% reduces the resistance to liquefaction of the sand–fines mixture. The liquefaction resistance increases well as the increase of fines-grained and relative density.

Solution-processed antireflective coating for back-contact perovskite solar cells.

Back-contact architectures for perovskite solar cells eliminate parasitic-absorption losses caused by the electrode and charge collection layers but increase surface reflection due to the high refractive index mismatch at the air/perovskite interface. To mitigate this, a ∼85 nm thick layer of poly(methyl methacrylate) (PMMA), with a refractive index between those of air and perovskite, has been applied as an antireflective coating. Transfer matrix modelling is used to determine the ideal PMMA layer thickness, with UV-Vis spectroscopy measurements used to confirm the increase in absorption that arises through the application of the antireflective coating. The deposition of a thin film of PMMA via spin coating onto a solar cell results in a 20-30% relative increase in short circuit current density and stable power output density.

The electrical conductivity properties of B4C ceramics by pressureless sintering

B4C ceramics with different carbon contents were fabricated by pressureless sintering at 2150 °C with SiC as a sintering additive. The effects of carbon content on microstructure, electrical properties and mechanical properties of B4C ceramics were investigated. More carbon content leads to a reduction in grain size and an increase in relative density. With the increase of carbon content, the electrical conductivity of the sample gradually changes from nonlinear to linear because of the formation of a conductive network in the sample. The electrical percolation is obtained when the C content is up to 10 wt%, and the electrical resistivity of the corresponding sample is 56.2 Ω cm. In terms of mechanical properties, flexural strength and elastic modulus shows a slight improvement, fracture toughness remains almost constant while Vickers hardness increases significantly.

Experimental and Constitutive Model on Dynamic Compressive Mechanical Properties of Entangled Metallic Wire Material under Low-Velocity Impact.

In this paper, the dynamic compressive mechanical properties of entangled metallic wire material (EMWM) under low-velocity impact were investigated and the constitutive model for EMWM under low-velocity impact was established. The research in this paper is based on a series of drop-hammer tests. The results show that the energy absorption rate of EMWM is in the range from 50% to 85%. Moreover, the EMWM with a higher relative density would not plastically deform macroscopically and has excellent characteristics of repetitive energy absorption. With the increase in relative density, the maximum deformation of EMWM decreases gradually, and the impact force of EMWM increases gradually. With the increase in impact-velocity, the phenomenon of stiffness softening before reaching the maximum deformation of EMWM becomes more significant. A constitutive model for EMWM based on the Sherwood–Frost model was established to predict the dynamic compressive mechanical properties of EMWM. The accuracy of the model was verified by comparing the calculated results with the experimental data of the EMWM with different relative densities under different impact-velocities. The comparison results show that the established model can properly predict the dynamic compressive mechanical characteristics of EMWM under low-velocity impact loading.

The Influence of Carbonyl Iron Powder, Grade VK, on Compactability and Strength Properties of Sintered Atomized Iron Powder, Grade PZhRV 2.200.26

This article discusses the influence of carbonyl iron powder, grade VK, on compactability, sintering, and mechanical properties of samples made of atomized iron powder, grade PZhRV 2.200.26, produced on commercial scale in Russia. It is demonstrated that the relative density of compacted samples made of dispersed PZhRV 2.200.26 iron powder can be increased by addition of particles of carbonyl iron powder, grade VK, which are predominantly located in pores between the particles of atomized powder. Additional introduction of solid lubricants in PZhRV 2.200.26 and VK mixture does not lead to further increase in relative density of pressed samples (more than 90%). It is established that addition of the VK carbonyl powder to the atomized PZhRV 2.200.26 powder in the amount of 15–20 wt % atomized the bending strength of green compacted pieces because of difficulties of plastic deformation of atomized particles into pores, but it increases the bending strength of the material after sintering owing to more developed contacts.

Choice of fiber-reinforced base material to reduce internal erosion mass transport

This paper aims to investigate the reduction of the internal erosion by inclusion of fiber in the context of the base sandy soil next to the filter. Two samples overlain by a gravel filter, and with different grain sizes, (i.e., a poorly graded sand, and a poorly graded sand with clay) were used in this study. The specimens with various relative densities were exposed to one-dimensional water flow under 1 bar pressure, and erosion of the base soils without reinforcement along with fiber-reinforced soils through the coarse grain filter was measured. Polypropylene fiber content was adjusted to 0.50, 0.75, and 1.0% by weight of the base soils. The mass of the soil clogged in the filter plus the ones suspended in the water were quantified to determine mass of internal erosion for each specimen. The results indicated that internal erosion and permeability decrease with increase in fiber reinforcement and relative density. In addition, reinforcing sands without or with fines could change their erosion category from some-erosion to no-erosion and from excessive-erosion to some-erosion respectively.

Spark plasma sintering of alumina/yttria‐doped silicon carbide

AbstractSilicon carbide possesses exceptional mechanical and thermal properties, but its densification by conventional sintering is often very difficult. In the present work, silicon carbide was consolidated by spark plasma sintering in the presence of alumina and yttria. The results pointed out that the use of a single oxide does not enhance the sintering kinetics significantly, while the contemporaneous addition of both oxides has a beneficial effect on densification, with a relative density increase of about 10%. Interestingly, the oxide doping allows to double the room‐temperature flexural strength.

Experimental study of one-dimensional compression creep in crushed dry coral sand

Understanding the time-dependent deformation behaviour of backfill coral sand is important to the long-term stability of engineering facilities built on reefs and reclaimed land. A series of one-dimensional compression tests (with no lateral strain) were carried out on crushed coral sand with a variety of grading and relative densities (50%, 70%, and 90%) sampled from the South China Sea. Axial pressure was applied in stepped loading form: 100, 200, 400, 800, and 1600 kPa. Each level loading was applied for 3 days and then completely unloaded until the deformation was stable, after which the next loading level was applied. The test results indicate: (i) the deformation of coral sand is much larger than silica sand and involves a larger proportion of time-dependent and plastic deformation; (ii) the total deformation of coral sand and proportion of irreversible deformation decreases as the relative density increases; (iii) coral sands of better grading tend to deform less in total and have larger proportions of elastic and time-dependent deformation; and (iv) the grading of coral sand changes during the deformation process due to particle breakage. Based on the test results, the relationships between particle breakage and pressure, relative density, and grading, as well as the grain-scale mechanism of the deformation, are discussed.

The Effect of Group of Piles on Existing Tunnel

This work focuses on the effect of construction and loading of piles group on an existing tunnel. This was achieved by performing model tests on a sandy soil using two relative densities (50% and 70%). The experimental models include group of piles (2×1) with 3d spacing and (2×2) with 3d and 8d spacing. Three clear distances between the pile and the tunnel were chosen to be 0, 0.6 and 1.6d (d: pile diameter). The pile used is a reinforced concrete pile with 20 mm diameter and 400 mm in length, the spacing piles in pile group is chosen to be 2d and 3d. The tunnel used was a reinforced concrete tunnel with diameter of 84 mm and 780 mm length. A numerical modelling of experiments was carried out using PLAXIS-software in which the hardening soil model (HS small) has been used for modelling. The main conclusion drawn from this study is that, the stresses generated on the tunnel lining during loading are higher than during construction stages. The stresses generated on the tunnel decreases with the increase in relative density and the distance from the tip of the pile.

Modification Of Wood By Organic-Mineral Complex

The aim of this work was assess the ability to improve the physicomechanical properties of wood by natural mineralization of the wood matrix under the influence of the organic-mineral complex of the composition arabinogalactan-silica-containing polymineral sand. As a criterion for optimizing the prescription factor, the value of the relative density change of the modified wood was used. For the experiments, prototypes of common pine wood were made. The organic component of the organic-mineral complex was arabinogalactan isolated from larch wood by water extraction. The mineral component of the complex was silica-containing polymineral rock with a silica content of more than 90 %. It has been established that the process of mineralization of the wood matrix with a water-soluble organic-mineral complex based on arabinogalactan and a polymineral silica-containing rock can occur spontaneously, while the maximum relative increase in wood density achieved in 24 hours is limited to 12 %. This increase in the density of wood allows it to increase its strength along the fibers and hardness by 47 % and 71 %, respectively. The obtained mathematical expressions relating the strength and hardness of wood after mineralization with a relative change in its density, which can be the basis for predicting these properties of wood material during its modification.

Global and local sand–geosynthetic interface behaviour

The influence of overall particle shape, mean particle size, initial relative density and effective normal stress on the global and local soil–geosynthetic interaction is investigated here through an extensive series of direct shear interface tests between six sands in contact with one multifilament woven geotextile, one non-woven geotextile and one geomembrane. Analysis of the soil–geosynthetic data highlights mobilisation of higher peak friction angles with increases in initial relative density and angularity of sand particles and decrease in the effective normal stress. The average frictional efficiencies of the sand–geosynthetic interfaces are 0·95 and 0·79, respectively, for the sand–geotextile and sand–geomembrane interfaces. It is shown that the interface slip increases with the initial relative density of sand and regularity of particles, and decreases with increasing the mean particle size and effective normal stress. Analysis of the local particle movements by means of digital particle image velocimetry revealed that the average thickness of the shear zone for the sand–geosynthetic interfaces tested ranges from 3·8 to 11·9 (with an average of 7·0) times the mean particle size of the contact sand. The experimental data indicate that thicknesses of the shear and dilation zones are almost equal for the sand–geosynthetics interfaces tested.

Study of newly developed Ti–Al–Co alloys foams for bioimplant application

Ti–Al–Co (6 wt% of Al and varying amount of Co content) alloys foams of different space holder contents (40 ± 2.5 to 70 ± 5% by volume with an increment of 10%) were fabricated using ammonium bicarbonate (NH4HCO3) as space holder. These foams were analysed in terms of cell morphology, microstructure, mechanical and corrosion properties. The cell sizes were almost invariant to the Co content and space holder content. The cell wall thickness increased with increase in relative density. It was found that with increase in Co contents in the Ti–Al–Co alloys, compressive strength, Young's modulus, energy absorption capacity and microhardness increases. Empirical relations were established to correlate these mechanical properties with Co wt%, strain rate (έ) and relative density. The experimentally obtained results were also verified with the existing analytical relation. It was observed that the openness of the foams increases with increase in space holder content. It was found that the Co concentration in the samples does not influence degree of openness but it influences the corrosion behaviour of the investigated foams. The corrosion rate (in mmpy) and electrochemical potential parameters were also obtained in simulated bio fluid, and compared with those of other Ti-alloys and found to be in close agreement with each other.To examine the suitability for bone implant application, the investigated Ti–Al–Co alloys foams were compared with human cortical as well as cancelleous bone in terms of macrostructural, microstructural, corrosion behaviour and mechanical properties. In every aspects these foams were found to be suited for bone implant application.

Experimental study of the shear strength of carbonate gravel

Current studies on carbonate soils are mostly directed at carbonate sands rather than widely distributed carbonate gravels. In this study, a series of large-scale direct shear tests were conducted to evaluate the parameters that affect the mechanical behaviours of carbonate gravels, including the particle size, gradation, relative density and normal stress. Simultaneously, several tests on quartz gravels with similar gradations were conducted for a comparison. The experimental results showed that a large cohesion, which is defined as the interlocking cohesion in this paper, appears in carbonate gravels and it increases as the average particle size and relative density increase. The strength envelope of the carbonate gravel with an average particle size greater than or equal to 3.9 mm could be expressed as a broken-line with two straight lines in the stress range of 0–1600 kPa, but for quartz gravel, the broken-line mode appears when the average particle size reaches 7.7 mm. This result could be related to the breakage of the particles. Therefore, a certain number of gravel particles with different sizes and different shapes were coloured to trace the breakage mode of the particles. At the same time, it could be found that the strength of the carbonate gravel is not always greater than that of the quartz gravel with a similar gradation.

The dynamics and impact of compositionally originating provinces in a mantle convection model featuring rheologically obtained plates

SUMMARY Previous geodynamic studies have indicated that the presence of a compositionally anomalous and intrinsically dense (CAID) mantle component can impact both core heat flux and surface features, such as plate velocity, number and size. Implementing spherical annulus geometry mantle convection models, we investigate the influence of intrinsically dense material in the lower mantle on core heat flux and the surface velocity field. The dense component is introduced into a system that features an established plate-like surface velocity field, and subsequently we analyse the evolution of the surface velocity as well as the interior thermal structure of the mantle. The distribution and mobility of the CAID material is investigated by varying its buoyancy ratio relative to the ambient mantle (ranging from 0.7 to 1.5), its total volume (3.5–10 per cent of the mantle volume) and its intrinsic viscosity (0.01–100 times the ambient mantle viscosity). We find at least three distinct distributions of the dense material can occur adjacent to the core–mantle boundary (CMB), including multiple piles of varying topography, a core enveloping layer and two diametrically opposed provinces (which can on occasion break into three distinct piles). The latter distribution mimics the morphology of the seismically observed large low shear wave velocity provinces (LLSVPs) and can occur over the entire range of CAID material viscosities. However, diametrically opposed provinces occur primarily in cases with CAID material buoyancy numbers of 0.7–0.85 (corresponding to contrasts in density between ambient and CAID material of 130 and 160 kg m−3, respectively) in our model (with an effective Rayleigh number of order 106). Steep and high topography piles are also obtained for cases featuring buoyancy ratios of 0.85 and viscosities 10–100 times that of the ambient mantle. An increase in relative density, as well as larger volumes of CAID material, lead to the development of a core enveloping layer. Our findings show that when two provinces are present core heat flux can be reduced by up to 50 per cent relative to cases in which CAID material is absent. Surface deformation quantified by Plateness is minimally influenced by variation of the properties of the dense material. Surface velocity is found to be reduced in general but mostly substantially in cases featuring high CAID material viscosities and large volumes (i.e. 10 per cent) or buoyancy ratios.

Effects of small and large shear histories on multiple liquefaction properties of sand with initial static shear

It has been reported that soils belonging to slope grounds show different types of liquefaction behavior than those belonging to horizontal grounds. Some research has also revealed that liquefaction histories can significantly affect the shear behavior of sandy soils. However, the combined effects of the slope angle and the magnitude of past shear histories on the liquefaction properties of soils have not been studied comprehensively. Based on this background, several multiple liquefaction tests with initial static shear were conducted on Toyoura sand. In each of these tests, a single specimen was sheared several times up to small or large double amplitude shear strain under a constant volume condition using a specially designed stacked-ring shear apparatus. The behavior of the Toyoura sand observed in these tests was discussed considering various perspectives, such as the increase in relative density, the induced anisotropy, the change in liquefaction resistance, and the shear strain accumulation. The findings of this study established that shear histories of smaller magnitude had relatively less influence on densification and induced anisotropy than those of larger magnitude. Moreover, shear histories of smaller magnitude also resulted in the relatively higher liquefaction resistance of sand specimens against the next cyclic shear, while the opposite trend was observed in the case of specimens subjected to shear histories of larger magnitude. Finally, shear strain accumulated less easily in tests with small shear histories than in those with large shear histories.

Effect of TiO2 content on the microstructure and mechanical and wear properties of yttria-stabilized zirconia ceramics prepared by pressureless sintering

A yttria-stabilized zirconia ceramic is prepared by pressureless sintering at 1350 °C, and the effects of TiO2 additive (0–10.0 wt%) on the microstructure, phase composition, and mechanical properties of the ceramic are investigated. The ceramic with no added TiO2 consists mainly of a monoclinic phase with a few tetragonal phases. With increasing TiO2 content, more t-ZrO2 phases are stabilized to room temperature, and a new phase, ZrTiO4, forms when the content of the TiO2 excess reaches 5 wt%. TiO2 facilitates the elimination of pores in the YSZ ceramics and increases the densification of the YSZ ceramics. The relative density increases from 91.5% (TiO2 0 wt%) to 96.2% (TiO2 10 wt%). Performance test results show a maximum bending strength of 312.56 MPa when the TiO2 content of reaches 10 wt%. The micro-hardness and wear resistance of the YSZ ceramics first increases then decreases as the TiO2 content increases, and the maximum micro-hardness and best wear resistance occur when the TiO2 is added at 5 wt%; the maximum micro-hardness and the minimum volume wear rate is 1792.5 HV and 2.06 × 10−4 mm3 N−1 × m, respectively. The wear mechanism of the ceramic is mainly plastic deformation and microcracking, and the fracture mechanism is mainly intergranular fracture. These results show that TiO2 is an effective sintering additive that promotes more t-ZrO2 phases stabilized at room temperature, with acceptable mechanical and wear resistance properties.

Study on mechanical properties of the gravelly soils with consolidated-undrained conditions

A standard stress path triaxial test system (STDTTS) was applied to study the mechanical properties of gravelly soil at initial relative densities of 0.13,0.5K 0.67 and 0.81 under confining pressures of 50,100,200 and 400 KPa, respectively. The results in the consolidated undrained tests show that all stress-strain curves behalf strain softening. With an increase of confining pressures, the pore pressure increases gradually and is almost irrelevant to initial relative density. With the increase of initial relative density, the peak strength of tested samples shows an uptrend, and its strength conforms to the Mohr-Coulomb strength criterion.

Enhanced tensile properties and corrosion resistance of stainless steel with copper-coated graphene fillers

Graphene (Gr) can significantly improve the mechanical properties of metal matrix materials. However, the reinforcing effect of Gr on stainless steel (SS) has rarely been investigated due to the difficulty in its uniform dispersion. In this study, 316L stainless steel was reinforced with copper-coated graphene (Gr-Cu/SS) through molecular level mixing, ball milling, and spark plasma sintering (SPS). The tensile strength and yield strength of Gr-Cu/SS have increased by 74.0% and 65.5%, respectively, with 0.2 wt% graphene added. The improvement on the tensile strength and yield strength of Gr-Cu/SS is attributed to the effective load transfer and the increase of relative density due to the addition of graphene. Moreover, the corrosion resistance of Gr-Cu/SS was improved, attributed to the low cathodic overvoltage of copper and the prevention of ionic transfer between stainless steel grains by graphene.

Microstructure, mechanical and EMI shielding performance in open cell austenitic stainless steel foam made through PU foam template

Open cell austenitic stainless steel foams having different porosities were made by impregnation of polyurethane foam followed by sintering. The austenitic stainless steel foams were characterized with respect to various techniques such as XRD, FESEM, EDX and compressive behaviour. The results show that the yield stress, elastic modulus and energy absorption are in the range of 5.2–10.5 MPa, 2.01–7.31 GPa and 1.2–3.5 MJ/m3 respectively. The yield strength, elastic modulus, average plateau stress and energy absorption increased with an increase in relative density and densification strain deceased with increase in relative density. The experimentally determined plateau stress, elastic modulus and densification strain were compared with Gibson-Ashby's relation and are found to be in close agreement. The electromagnetic interference shielding of austenitic stainless steel were measured in X-band frequency region (8.2–12.4 GHz) and found that electromagnetic interference shielding increases with relative density in all cases. The austenitic stainless steel foam has maximum electromagnetic interference shielding of −31.5 dB with absorption dominating mechanism at relative density of 0.17. This has been explained from the microstructural characteristics of austenitic stainless steel foam.

Influence of sintering aid on the microstructure and conductivity of the garnet-type W-doped Li7La3Zr2O12 ceramic electrolyte

Li6.4La3Zr1.7W0.3O12 (LLZWO) garnet-type structure was prepared with SiO2 as sintering aid via solid-state reaction method. The prepared ceramic samples were characterized by X-ray diffraction and Raman spectra to judge the structure. Microstructure, lithium-ion conductivity and electronic conductivity of all components were investigated by means of scanning electron microscopy, electrochemical impedance spectroscopy and potentiostatic polarization measurement, respectively. These investigations show that SiO2 was found to be a better additive to reduce the porosity and improve conductivity. The relative density and ionic conductivity increase first and then decrease with increasing SiO2 content. The relative density of 93.8% and ionic conductivity of 9.11 × 10−4 S cm−1 in the sample with 0.2 wt% SiO2 were obtained. In contrast, the activation energy reaches a minimum value of 0.38 eV.