Size Of Structural Elements Research Articles

High modulus concrete: Effects of low carbon nanotube and nanofiber additions

New tall building designs require higher modulus of concrete that allows to limit lateral deformations and decrease the size of structural elements. The modulus of conventional and high-strength concrete can dramatically improve with the addition of very low amounts of effectively dispersed CNTs and CNFs and without the need of optimizing the mixture proportions with the use of supplementary cementitious materials and/or stiffer aggregates. It is shown that while the American and European empirical relationships suggest the modulus as a function of the square or cube root of compressive strength, compared with concretes of similar modulus values, the addition of 0.1 wt% of CNTs and CNFs resulted in concretes exhibiting approximately 1.6 times higher modulus values at almost half the compressive strength. The proportionality of the compressive stress to strain curves of nanomodified conventional and high-strength concrete indicates that a higher load-carrying capacity in the elastic area can be achieved for loadings up to the percolation threshold. An increase in the count of individual carbon nanotubes and nanofibers above the threshold limit adversely affects the materials’ compliance and the resulting modulus of elasticity.

MODIFICATION OF THE STRUCTURAL-PHASE STATE AND ELECTRICAL PROPERTIES OF COPPER-CONTAINING FULLERITE FILMS DURING THERMAL ANNEALING IN VACUUM

Abstract—Scanning electron and atomic force microscopy, X-ray diffraction, X-ray spectral microanalysis, and diffraction of reflected electrons were used to study changes in the structure, elemental, and phase composition of fullerite–copper films with an atomic metal fraction of 0.5, 1, 2 and 4%, deposited on oxidized single-crystal silicon substrates and subjected to thermal exposure in vacuum at different temperatures (470, 520, 570 and 620 K). It was found that thermal annealing at T = 520 K (t = 1 h) leads to the formation of a nanocrystalline structure with an average structural elements size of 33, 42, 50, and 65 nm for fullerite–copper films with an atomic fraction of metal of 0.5, 1, 2, and 4% respectively. An increase in temperature and annealing time leads to an increase in the size of structural elements and the formation of a new of CuxC60 phase, which belongs to the monoclinic space group P2/m. Electric force microscopy and the four-probe method were used to study changes in the local electrical properties and electrical resistivity of copper-containing fullerite films during vacuum annealing.

Вплив органічного волокна Танлон на експлуатаційні показники політрифторхлоретилену

The impact of organic polysulfonamide Tanlon T700 fiber on the tribological and thermophysical properties of polychlorotrifluoroethylene is considered in the article. As a result of the researches, it was found out that developed organoplastics exceed base polymer in intensity of linear wear and coefficient of thermal linear growth by 2,5-7,5 times and by 25 %. That is due to the decrease in the size of structural elements of supramolecular structure which becomes more orderly and better focused. The results of the research show that developed composition with optimal fiber content (15 mass.%) can be recommended for the manufacturing of the parts of moving joints of machines and mechanisms in various industries

A role of initial microstructure in characteristics of the surface layers produced by ion-plasma treatment in CrNiMo austenitic stainless steel

A study on elemental composition, phase composition, microstructure, nanohardness and fracture micromechanisms of the surface layers obtained by ion-plasma treatment of a stable CrNiMo austenitic stainless steel with different initial microstructures has been carried out. In cold-rolled specimens, containing a high dislocation density and deformation-induced low- and high-angle boundaries and possessing structural elements of 330 nm in size, interstitial concentration (carbon and nitrogen) is much higher than that for cold-rolled and annealed specimens with a similar size of structural elements. After ion-plasma treatment, a surface nanohardness of the pre-deformed specimens is higher by 8 GPa than one for specimens annealed after cold rolling. Deformation-assisted microstructure accumulates carbon more likely than nitrogen under ion-plasma treatment. These results provide experimental support for decisive role of high dislocation density and deformation-assisted well-developed microstructure in accumulation and bulk diffusion of interstitials under ion-plasma treatment of steel.

Estimating the cross-sectional area of inverted-V braces required for mitigating the progressive collapse of Steel Intermediate Moment Resisting Frames

The use of inverted-V braces is one of the retrofitting strategies engineers employ to mitigate progressive collapse in steel intermediate moment-resisting frames (SIMFs). However, the required cross-sectional area of the bracing member is not only dependent on the structural configurations but also on the seismicity of the region. In this study, a new equation is proposed to estimate the cross-sectional area of inverted-V braces required to mitigate failure progression in SIMFs that are subject to abrupt loss of an exterior column in the first storey. In the proposed equation, the area of beam element in the affected span and the seismicity of the region are considered. For this purpose, six SIMF buildings are designed, considering variation in the seismic base shear and the number of storeys. Then, the structural response of these SIMFs when subjected to an exterior column loss is studied. Using dynamic pushdown analyses, failure load factors of these frames are determined. Then, inverted-V braces of five different sizes are added to the studied frames. Results provide a mathematical correlation between the base shear coefficients, the size of structural elements and the associated retrofitting effect. This approximate equation is then validated by analysing two extra case study structures.

The Influence of Dimesions and Phase State of Structural Elements on Mechanical Properties of Binary Alloys of the Ti–Nb and Zr–Nb Systems

The results of investigation of the influence of the structural element size and phase state of the Ti – 45 wt.% Nb and Zr – 1 wt.% Nb binary alloys on their mechanical properties are presented. The structural states of the alloys with the structural elements of different dimensions were formed from the ultrafine-grained state via annealing. The curves of dependence of the yield strength and microhardness on the average size of the structural elements, d –1/2, are obtained using the Hall–Petch relation. It is shown that for the Zr – 1 wt.% Nb alloy, the Hall–Petch relation is fulfilled in the entire range of sizes under study, from ultrafine-grained to finegrained states 0.2–1.9 μm. For the Ti – 45 wt.% Nb alloy, in the analysis of the Hall–Petch relationship within the structural element size range 0.43–45 μm, its phase composition is taken into consideration, specifically, the presence of dispersion-strengthened β-phase grains, α-phase subgrains, nonequilibrium nanosized ω- phase, and the bimodal grain-subgrain structure.

Structure and Properties of Ni47Mn42In11 Alloy after Severe Plastic Deformation

This work has studied the effect of severe plastic deformation performed by high pressure torsion at 8 GPa and room temperature on the crystallographic structure, microhardness, and magnetic susceptibility of the ferromagnetic Ni47Mn42In11 alloy. The size of structural elements decreases, whereas the fraction of a ductile fracture constituent and the microhardness increase with increasing true strain. Severe plastic deformation performed by high pressure torsion results in phase transformation. No modulated martensite is observed in the structure after deformation.

Microstructure and brittle fracture resistance of layered steel composites produced by explosion welding and pack rolling followed by heat treatment

In the present paper, the microstructure and fracture resistance characteristics of 7-layered composites based on Fe-2Mn-1Si low carbon low alloyed steel and Fe-11Cr-9Ni-2Mo-1Ti maraging steel obtained by two different methods such as explosion welding and hot pack rolling with subsequent heat treatment were investigated. It was shown that an important microstructural features of Fe-2Mn-1Si steel layers are associated with the formation of a fragmentation zone ~10 μm wide with a size of structural elements 0.5-1.0 μm near the interface in the welded composites and the appearance of decarburized ferrite zone ~50 μm wide in the hot-rolled composites. Aсcording to local energy dispersive X-ray microanalysis, at the interface of welded and hot-rolled composites, the most active diffusion processes near of Fe-2Mn-1Si and Fe-11Cr-9Ni-2Mo-1Ti steel interlayer borders occur during the composites production by pack rolling. It was established that explosion welding makes it possible to retain the initial microstructure of steel blanks, with the exception of a narrow near-weld zone of grain fragmentation. After the subsequent heat treatment of explosively welded and hot-rolled composites, Fe-2Mn-1Si steel layers are characterized by a viscous ferrite(sorbitol)-pearlite microstructure, and Fe-11Cr-9Ni-2Mo-1Ti steel layers possess a martensitic microstructure with strengthening intermetallic particles. From the results of impact tests at temperatures from +20°C to −60°C, it was found that the impact strength KCV and energy of impact loading A of the hot-rolled composites are 2 and 3.5 – 5.4 times higher than the ones of the welded composites, respectively.

Плазменная технология формирования поверхности электродов кардиостимуляторов из рутения

The electric pacemaker (EP), a device for electrically stimulating the myocardium, is widely used for treating and rehabilitating patients who have suffered heart attacks and other heart diseases. Stable transfer of energy in impulses from the EP to the heart and the optimal coordination between the EP parameters and the pacemaker electrodes are the most important conditions for the EP operation. The electrode is electrically connected with the myocardium tissue mainly through capacitive coupling. To stimulate the myocardium, an electrical impulse with duration of 100–300 µs and energy of 1–5 μJ is required; with the stimulation threshold equal to 1 V, the coupling capacitance should be equal to 2–10 µF. When an electric potential is applied to the electrode, a double electric layer (DEL) appears in the blood electrolyte at the electrode surface. The DEL’s capacitive impedance is significantly higher than its ohmic resistance. The DEL is electrically equivalent to two series-connected capacitors, and its capacitance is determined by the capacitances of the DEL’s inner dense part and of its outer diffuse part. To improve the EP efficiency, the DEL capacitance should be increased. To do so, two methods are used: increasing the electrode surface area by extending its surface and increasing the surface adsorption by using special coatings. The modern pacemaker electrodes have the characteristic size of extended surface inhomogeneity equal to around 1 µm, which is larger than the DEL’s inner dense layer thickness, which is less than 1 nm. Therefore, for pacemaker electrodes, the size of the surface structure elements should be reduced down to 1 nm. Such structures of the "fuzz" type can be obtained by processing materials with plasma. A PLM plasma installation intended for obtaining an extended surface nanostructure on metals, including that of the “fuzz” type, has been constructed at the National Research University Moscow Power Engineering Institute. Electrodes of metals from the platinum group are the most promising ones; the iridium coating of the electrodes has the lowest capacitive impedance. Ruthenium (Ru) also belongs to the platinum group of elements. In this study, ruthenium, an element which is a chemical analog of iridium but having a number of technological advantages, has for the first time been proposed for coating the electrodes. Ruthenium is the only one of these elements that is naturally present in the human body. In addition, ruthenium is significantly cheaper than iridium. In the PLM installation, a nanostructured coating of ruthenium is produced on the electrode by sputtering Ru by means of a target in plasma discharge. It is proposed to test a few approaches, including that in which a “fuzz” type structure is produced on a titanium surface. After that, ruthenium can be sprayed onto this structure, or a “fuzz” type structure can be produced already on the deposited ruthenium layer. Such experiments open the possibility to develop a new technology for making the pacemaker electrodes with improved characteristics.

Edge Detection of High-Voltage Porcelain Insulators in Infrared Image Using Dual Parity Morphological Gradients

A new edge detection operator based on dual parity morphological gradients is proposed, in order to accurately segment a porcelain insulator string in an infrared image before the identification and diagnosis of deteriorated insulators by the extracted thermal information. When applied to the double-shed insulators, the proposed detector is capable of effectively eliminating the blurred region between the upper and lower sheds as well as preventing over-segmentation by combining both odd and even structural elements. Compared with the multiscale morphological gradient algorithm, this technique reduces the size of the maximum structural elements to optimize the computational complexity. A quantitative evaluation using PSNR, IoU, and FPR indexes shows that the new technique outperforms other common edge detectors. In addition, the experiments on thousands of real infrared images demonstrate the detector to be highly effective despite its low complexity.

Electroosmotic pressure in the process of a biocompatible coating applying on the inner surfaces of nanostructured ceramics

The role of the effect of electroosmosis in the process of electrochemical deposition of a biocompatible coating on the inner surfaces of porous nanostructured ceramics, a material used to make endoprostheses and implants in medicine, is discussed. The biocompatibility of endoprostheses and implants with the human body is ensured by applying a special coating on the internal and external surfaces of the base material. The commonly acepted chemical compound used to form this coating is hydroxyapatite Ca10(PO4)6(OH)2. Multicomponent ceramic materials, from which the basis of endoprostheses and implants are made, are usually obtained by the traditional method of powder metallurgy - sintering, i.e., exposure of a mixture of powders at an elevated temperature under pressure. The material obtained in this way is a polycrystal. In addition, the structure of such a material contains a certain amount of voids in the form of individual pores or their associations (capillaries). The paper shows that the use of nano-structured ceramic materials with a characteristic average size of structural elements (grains, pores and their aggregations) of the order ≈(10–9–10–7)м as a material for the manufacture of implants may determine the greater efficiency of the process of electrochemical application of a biocompatible coating on them, since the resulting large electroosmotic pressure in the capillaries leads to a greater degree of filling of the porous system with electrolyte. The magnitude of the electroosmotic pressure can be increased by increasing the strength of the acting electric field or by decreasing the dielectric constant of the electrolyte ε when additional chemical additives are introduced into the electrolyte. The maximum degree of hollow channels (capillaries) filling with electrolyte, and, consequently, the efficiency of applying a biocompatible coating to the internal surfaces of ceramics using the electrochemical method, is achieved with the capillary system of the material being completely open.

Separation of Soil Macropore Types in Three‐Dimensional X‐Ray Computed Tomography Images Based on Pore Geometry Characteristics

Core Ideas For preferential flow modeling, different macropore types must be considered. A method was developed for separating biopores and cracks in 3D images from XRCT. The method enabled a more objective determination of structuring element sizes. The voxel‐based approach was found useful for quantification of macropore types. In structured soils, earthworm burrows, root channels, shrinkage cracks, and interaggregate spaces form complex macropore networks. Depending on the type and morphological properties, each macropore surface type is coated with specific organo‐mineral compounds, differently affecting sorption and mass exchange during preferential flow and turnover processes. For a quantitative, macropore type–specific analysis using X‐ray computed tomography (XRCT) with subsequent three‐dimensional (3D) image analysis, a discrimination of biopores from cracks and interaggregate spaces is necessary. We developed a method that allows separating biopores from other larger macropores in 3D images from XRCT of intact soil cores. An image‐processing workflow using the MAVI (Modular Algorithms for Volume Images) software framework ToolIP (Tool for Image Processing) was created to handle XRCT 3D images. Masking steps enabled to retain the surface roughness in the resulting two images of separated biopores and cracks. As a key point, the sizes of the structuring elements used in the spherical opening and dilation were objectively determined. For this purpose, maximum differences in the pore shapes between the 3D images of cylindrical biopores vs. more flat cracks and unregularly interaggregate spaces were focused. At the given resolution of 231‐μm voxel edge length, an optimum size of 2.5 voxels was found for both processing steps. The voxel‐based approach is applicable to XRCT 3D images of different spatial resolution and appears useful for the quantification of physicochemical surface properties of different macropore types for soil volumes, enabling a more precise description of preferential flow and transport.

Strengthening of Magnesium Alloy WE43 by Rotary Swaging

The article presents the results of an investigation of microstructure, mechanical properties and corrosion resistance of magnesium alloy WE43 processed by rotary swaging. The resulting microstructure is characterized by an average size of structural elements of 0.5 – 0.8 μm. The grain refinement leads to an increase in the strength of the alloy to 393 – 416 MPa while the tensile elongation stays at a level of 7 – 12.5%. The microstructure produced by rotary swaging does not lead to deterioration of the resistance of the alloy to electrochemical and chemical corrosion.

Phase composition of macroporous Ni-Al alloys obtained by combustion synthesis

This paper discusses the phase composition of macroporous Ni-Al alloys obtained by self-propagating high-temperature synthesis. The alloys have been synthesized in a nonstationary combustion mode. The combustion wave consists of super adiabatic foci, and macroporous structure is realized under the action of capillary hydrodynamic effects. The influence of reaction mixture composition of aluminium in the range of 13.5-31.5 wt.% is also discussed. The specific requirements to obtain the single phase B2 NiAl and LI2 Ni3Al as well as biphase gas permeable alloys with the average size of structure elements in the range of 1.2-3.15 mm are described in the paper.

Evolution of the structure and properties of pure aluminum under severe plastic deformation

The influence of severe plastic deformation (SPD) by equal-channel angular pressing (ECAP) on the formation of the structure and the mechanical properties of pure aluminum is studied. It is established that an ultrafine-grained structure is formed with an average size of structural elements of ∼ 1.5 µm. X-ray diffraction studies have shown that SPD results in a broadening of interference lines with a decrease in their intensity, which indicates an increase in the imperfection of the structure and its high dispersion. SPD also results in a significant enhancement of microhardness, yield stress and ultimate tensile strength in aluminum.

Effect of ECAP on structural, mechanical and functional characteristics of the austenitic Cr-Ni-Ti steels

In this study, equal-channel angular pressing (ECAP) of austenitic Cr-Ni-Ti stainless steel was carried out. Effect of ECAP on the evolution of the microstructure and mechanical and service properties of the Cr-Ni-Ti steel was investigated. The microstructure in the completely austenitic state processed by 6 passes of ECAP at 200 °C was obtained and examined by optical and transmission electron microscopy. Mechanical properties were determined by the Vickers micro-hardness measurements and tensile testing. Fracture toughness was evaluated and tribological properties of Cr-Ni-Ti stainless steel processed by ECAP were studied. It was revealed that submicrocrystalline structure with an average size of structural elements of 100 nm produced by ECAP significantly increased the strength properties of Cr-Ni-Ti stainless steel than that in the quenched state. After ECAP the ultimate tensile strength increased by 1.7 times, the fatigue limit by 1,5 times than that in the initial state. It was revealed that Cr-Ni-Ti steel after ECAP demonstrates 2.9 times higher fracture toughness than that in the quenched state. It is established that ECAP does not significantly affect the coefficient of friction and mass wear.

Relation of elastic properties, yield stress and ultimate strength of polycrystalline metals to their melting and evaporation parameters with account for nano and micro structure

The paper is concerned with the main factors that determine the mechanical characteristics of materials. The values of these factors are shown to be related to the size of structural elements. These elements are the lattice atoms in the case of calculation of Young’s modulus and the crystallites of various sizes in the case of determining the yield stress and ultimate strength. The models are constructed which allow obtaining fundamental relationships that adequately determine the mechanical characteristics of solid metals. Verification of the dependences is carried out on the basis of experimental data, and the adequacy of the proposed models is proved.

The Effect of Microarc Oxidation on the Structure and Hardness of Aluminum-Oxide Coatings Formed by Plasma Spraying on Titanium

Coatings formed by plasma spraying of electrocorundum on VT6 titanium alloy and subsequent microarc oxidation at different current densities were examined. The parameters of structure and hardness of metal-oxide layers were studied. The effect of current density on them was also found. During microarc oxidation, the open porosity (from 50.3 ± 4.5 to 10.3 ± 1.5%), the thickness (from 47.4 ± 3.3 to 30.2 ± 5.3 μm), and the average size of structural elements of presprayed coating were decreased, while its hardness was increased from 760 ± 486 to 875 ± 238 HV2. The magnitude of changes in the structure of the plasma coatings depended on the current density during modification. Microarc oxidation makes it possible to form structural elements in the form of pores and crystals with a size from 15 to 150 μm on the surface of sprayed aluminumoxide coatings.

Comparative analysis of the complete plastomes of garlic Allium sativum and bulb onion Allium cepa

Sequencing and comparative characterization of plant plastid genomes, or plastomes, is an important tool for modern phylogenetic and taxonomic studies, as well as for understanding the plastome evolution. The genusAlliumL. (family Amaryllidaceae) incorporates more than 900 species, includes economically signifi­cant vegetable crops such as garlicA. sativum, onionA. cepa, leekA. porrum, etc. In this work, the plastome of garlicA. sativumhas been completely sequenced. TheA. sativumplastome is 153172 bp in size. It consists of a large unique (LSC, 82035 bp) and small unique (SSC, 18015 bp) copies, separated by inverted repeats (IRa and IRb) of 26561 bp each. In the garlic plastome, 134 genes have been annotated: 82 protein-coding genes, 38 tRNA genes, 8 rRNA genes, and 6 pseudogenes. Comparative analysis ofA. sativumandA. cepaplastomes reveals differences in the sizes of structural elements and spacers at the inverted repeat bound­aries. The total numbers of genes inA. sativumandA. cepaare the same, but the gene composition is dif­ferent: therpl22gene is functional inA. sativum, being a pseudogene inA. cepa; conversely, therps16gene is a pseudogene inA. sativumand a protein-coding gene inA. cepa. In theA. sativumandA. cepaplastomes, 32 SSR sequences have been identified. More than half of them are dinucleotides, and the remaining are tetra-, penta-, and hexanucleotides at the same time, trinucleotides were absent. The compared plastomes differ in the numbers of certain SSRs, and some are present in only one of the species.

Relationship of the Structure and the Effective Diffusion Properties of Porous Zinc- and Copper-Containing Calcium Phosphate Coatings

The morphology and the structure of zinc- or copper-containing calcium phosphate coatings deposited by the microarc oxidation (MAO) method at different voltages on pure titanium and low-modulus Ti-40 wt % Nb alloy substrates are investigated. The morphology of the MAO coatings on both substrates is composed of sphere-shaped structural elements 8–42 μm in size and pores 1–15 μm in size. When the process voltage is increased from 200 to 300 V, these structural elements grow and partially destruct. It is ascertained that the MAO voltage increase leads to the linear increase in the surface porosity of the coatings from 14 to 24%. It is established that the effective diffusion coefficients of the model biological fluid in porous coatings vary from 0.85 × 10–10 to 9.0 × 10–10 m2/s. Under the increase in the structure element size, the effective diffusion coefficient of the model biological fluid increases in the MAO coatings deposited on a titanium substrate and decreases in those deposited on Ti-40 wt % Nb alloy. The observed difference is related to the increase in the crystalline phase fraction.