Increase In Strength Properties Research Articles

Research into impacts of extremely cold climates on properties of basalt plastic rods

The results of the research into impacts of extremely cold climates on physical and mechanical properties of basalt plastic rods of a periodic profile have been given. The object of research is a polymer composite building purpose material - basalt composite reinforcement, constituting one-way-polar basalt rods with deformed section diameter from 6 to 8mm., made on the basis of LLC "TBM" production unit with technical production line "Struna" under the technical specifications 2296-001-86166796-2013 "Non-metallic composite basalt reinforcement". Changes of physical and mechanical properties have been defined for the initial and exposed samples of basalt plastic reinforcement. After exposure in Yakutsk, the increase in strength properties by 4–12% depending on the diameter of rods has been revealed. The research of temperature dependences of the samples of basalt plastic reinforcement has showed rather good reproducibility of the results obtained by different methods. The observed increase in Tg, ∆L⁄L0 and ᾱ is due to the prevalence of the effect of post-hardening of the BPA polymeric matrix over the effect of tension relief of the polymeric matrix at the interface with basalt fiber.Thus, as the result of the conducted research, the increase in adhesion strength of the “fiber- matrix” compounds in the process of exposure has been established, and the matrix added solidity to the material and facilitated effective usage of mechanical properties of fibers and uniform distribution of efforts between them.

New eutectic type Al alloys based on the Al-Ca-La(-Zr, Sc) system

Abstract Phase equilibria in the Al-Ca-La system, microstructure and mechanical properties of alloys were investigated. The most promising alloy contents up to 3 wt% Ca and 2 wt% La (Al3Ca2La). The microstructure consists of Al primary crystals and ultra-fine eutectic which consists of binary Al4Ca and Al4La compounds. The Al3Ca2La alloy in as-cast state has ultimate tensile strength of about 125 ± 10 MPa, yield strength of 70 ± 10 MPa and ductility of 15.0 ± 0.2%. The alloying with zirconium and scandium of up to 0.3 wt% provides an increase in strength properties by two times after sample annealing at 350 °C.

The peculiarities of surface friction treatment on beryllium bronze

Abstract The effect of friction surface strengthening on the microstructure of the copper-beryllium alloy BrBNT1.7 is considered using x-ray diffraction and electron microscopic analysis. It is shown that the aging of the quenched alloy is accompanied by intermittent decomposition with a predominant precipitation of the intermetallic χ-phase of the Be12Ti type. The subsequent intense surface plastic deformation via sliding friction heavily refines the matrix solution to the size of a nanometer. Partial deformation dissolution of the second-phase particles occurs. Aging and subsequent friction treatment contribute to an effective increase in strength properties (yield strength and microhardness).

Structure and properties of 17G1S-U low-carbon pipe steel microalloyed by boron

The results of analysis of the influence of boron microalloying on structure and properties of 17G1S-U pipe steel are given in the paper. Studies of metal structure were performed by electron microscopy and local X-ray spectral analysis. It has been established that metal containing 0.006 % of boron is characterized by an increased volume concentration to 0.029 % of oxide (OS) and oxysulfide (OSB) inclusions, whose content in metal without boron reaches 0.006 %. Separate sulphide inclusions (CB), whose concentration does not exceed 0.004 % against 0.029 % in a metal without boron, containing 0.01 % S is practically absent in the metal with boron containing 0.003 % S. The microalloying of pipe steel by boron has ensured the preferential formation of small nonmetallic inclusions, evenly distributed in the volume of metal. The proportion of nonmetallic inclusions with size less than 2 (rm is 76.1 %, whereas in steel without boron it is only 58.5 %. In this case, large nonmetallic inclusions of more than 10 rm are practically absent in the sample with boron. Their share does not exceed 0.6 %, which is 22 times less than their amount in the sample without boron. The structure of the sample without boron consists mainly of ferrite and a small amount of perlite, and the sample with boron is represented by a dispersed ferritic-bainitic structure. Increasing the microhardness of both ferrite and pearlite 80 and 100 HV10, respectively, is observed by adding boron to steel. The mechanical properties of 10 mm hot rolled metal from boron-containing 17G1S-U pipe steel are characterized by increased strength properties with preservation of plastic characteristics, due to the formation of predominantly small nonmetallic inclusions and a finely dispersed ferritic-bainitic structure. The absolute values of the yield stress and the time resistance of pipe steel containing in mass %: 0.006 B and 0.003 S are achieved without heat treatment at 585 and 685 MPa, respectively, and meet the X80 strength class, while retaining sufficiently high plastic characteristics. The pipe steel without boron containing 0.01 % of S belongs to the X70 strength class and is characterized by tensile strength lowered to 540 and 610 MPa and a temporary resistance, respectively.

PHBV-graft-GMA via reactive extrusion and its use in PHBV/nanocellulose crystal composites

Reactive extrusion was used for dicumyl peroxide (DCP)-initiated grafting of glycidyl methacrylate (GMA) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The effects of GMA and DCP content and their weight ratio on the GMA grafting percentage (GP%), the polymer melt viscosity, and the PHBV molecular weight were investigated. FTIR spectroscopy determined that the DCP did indeed initiate GMA grafting. However, the changes in both the zero-shear viscosity (η0) and the molecular weight suggested the existence of crosslinking products in the extruded polymers. A negative correlation between the degree of crystallinity (χc) of the PHBV-g-GMA and the GP% suggested the influence of chain branching on crystallinity. In addition, the GMA content was found as a key factor determining the GP%. The PHBV-g-GMA was used as a matrix polymer in cellulose nanocomposites to evaluate its effects on CNC dispersion and CNC-matrix adhesion relative to the unmodified PHBV matrix. The SEM images and the change in crystallization temperature suggested enhanced dispersion of CNC in a PHBV-g-GMA matrix. However, little increase in strength properties were found with CNC addition suggesting inadequate stress transfer between the matrix and CNCs.

TMP properties and refiner conditions in a CD82 chip refiner at different operation points. Part II: Comparison of the five tests

Abstract This paper is part two of a study on a CD 82 TMP chip refiner where relations between changes in the process conditions and changes in the properties of the produced pulp are investigated. Focus is on the ratio between tensile index and specific energy consumption when results from five tests are compared. Pulp properties were measured for composite pulp samples taken from the refiner blow line. Residence times and pulp consistencies were estimated by use of the extended entropy model. Clearly, an increase in specific energy does not necessarily implicate an increase in strength properties of the pulp produced. It is of high importance to have access to information about the refining zone conditions when searching for an optimal operation point in terms of the ratio between tensile index and specific energy. In these tests, this ratio had a maximum at about 55 % measured blow line consistency. Unfavourable operating conditions were identified at high pulp consistencies, especially after the FZ, where pulp consistencies well above 70 % were observed. The estimated residence time for each refining zone responded differently when applying changes in production rate, plate gaps and dilution water flow rates. In conclusion, the results associated with estimated pulp consistencies where easier to interpret compared with results for residence times, implying that additional tests are required for the latter variable. In addition to tensile index, pulp properties like freeness, Somerville shives and light scattering coefficient were included in the analysis.

Effect of Foundry Sand and Mineral Admixtures on Mechanical Properties of Concrete

Abstract Foundry sand waste can be utilized for the preparation of concrete as a partial replacement of sand. The strength properties of M25 grade concrete are studied with different percentages of replacement of fine aggregates by foundry sand at 0%, 10%, 20%, 30%, 40%, and 50%. The optimum percentage of foundry sand replacement in the concrete corresponding to maximum strength will be identified. Keeping this optimum percentage of foundry sand replacement as a constant, a cement replacement study with mineral admixtures such as silica fume (5%, 7.5%, 10%) and fly ash (10%, 15%, 20%,) is carried out separately. The maximum increase in strength properties as compared to conventional concrete was achieved at 40% foundry sand replacement. Test results indicated that a 40% replacement of foundry sand with silica fume showed better performance than that of fly ash. The maximum increase in strengths was observed in a mix consisting of 40% foundry sand and 10% silica fume. SEM analysis of the concrete specimens also reveals that a mix with 40% foundry sand and 10% silica fume obtained the highest strength properties compared to all other mixes due to the creation of more C-H-S gel formations and fewer pores.

ИЗУЧЕНИЕ ПОЛУЧЕНИЯ ДРЕВЕСНЫХ И РАСТИТЕЛЬНЫХ ПЛАСТИКОВ БЕЗ СВЯЗУЮЩИХ В ПРИСУТСТВИИ КАТАЛИЗАТОРОВ ТИПА ПОЛИОКСОМЕТАЛЛАТОВ

The possibility of obtaining wood and plant plastics without a binder (WP-WB) in the presence of a catalyst of man-ganese-containing sodium vanadomolybdophosphate has been investigated. The use of this catalyst makes it possible to reduce the temperature of hot pressing in closed molds from 1,800°C to 1,600°C. The fractional composition of the initial press raw material influences physical and mechanical properties of WP-WB. Higher values of the plastic properties are obtained by using a 0.7 mm fraction, which is associated with an increased specific surface area of the particles compared to 1.3 mm particles. The results has showed that the samples obtained by using the catalyst have increase in strength properties (flexural strength, flexural modulus, hardness) at lower pressing temperature, but reduction of water resistance performance has been observed . This is explained by the increase in the content of functional groups when using a catalyst. The process of obtaining plastic can be broken down into two successive stages: the first is hydrothermal destruction of lignin-carbohydrate complex (initial moisture of the press raw material is 12%, the temperature of hot pressing in closed molds is 160 ... .180 ° C) and partial chemical activation of lignin as a result of hydrogen peroxide and catalyst application; the second stage - formation of plastic with the formation of a network structure due to the formed functional groups. It is established that the values of physical and mechanical properties of WP-WB are higher than those of plastic obtained on the basis of plant raw materials (PP-WB). This can be explained by the fact that lignin of coniferous species has the guaiacylpropane structure, while plant raw material has a hydroxyphenylpropane structure

Performance of Concrete Using Waste Fiber Reinforced Polymer Powder as a Partial Replacement For Fine Aggregate

Proper disposal of fiber waste products is a major problem faced by the FRP industries and hence needs a sustainable solution for its reuse and recycling. The present paper deals with the performance of concrete using waste fiber reinforced polymer powder (FRP), as a partial replacement for fine aggregate in the concrete. Field emission scanning electron microscopy (FESEM) analysis along with energy dispersive X-Ray (EDX) is carried out to find out the elements present in the FRP powder used in the present study. Partial replacement of 5%, 10% and 15% are carried out in the fine aggregate content of control mixture of M30 grade. The workability, compressive strength, split tensile strength, flexural strength, impact and abrasion resistance are measured to observe the effect of waste FRP powder on the concrete. From the study it is observed that workability decreased with increase in percentage of FRP substitution with a considerable increase in strength properties for 10% replacement of fine aggregate content by waste fiber reinforced polymer powder. Also better performance is observed for impact and abrasion resistance

Pulse Processing of Molten Metals

The use of external physical actions (vibration, ultrasound, etc.) on molten metals is a safe way to change the structure and properties of metals and alloys. Such processing contributes to the formation of a fine structure with an increased level of strength properties. The work covers the results of a relatively new method of molten metals processing with electromagnetic pulses. It shows the results of processing pure metals of zinc and aluminum. The increase in strength properties and the decrease in porosity of the casts have been registered. The article also contains the empiric results of steel rods hot zincing. The zinc alloy was exposed to irradiation directly in the hot zincing bath.

Low Density Cellular Concrete Made of Reftinskaya SDPP Fly Ash

There is experience of the production and use of low density autoclaved aerated concrete. It is shown that fly-ash from Reftinskaya State District Power Plant efficiently substitutes the quartz sand aerated concrete technology. Its use opens up additional opportunities for AAC with the density of 300-400 kg/m3. In order to optimize the structure and properties it has been suggested to introduce the gypsum aerated concrete additive into the autoclave in the amount of 3-5% by weight of the dry components. The introduction of gypsum ensures the creation of a uniform homogeneous structure, resulting in the increased strength properties and reduced drying shrinkage. The resulting aerated concrete has thermal conductivity of 0.075-0.100 W/m·K, it allows using and creating single-layer fencing structures without additional insulation. The low-density gas-ash concrete production allows extending the scope of cellular concrete application and increasing its competitive advantages over other walls and insulating materials.

Stabilization of clayey soil using lignosulfonate

Abstract Many customary soil additives (e.g., cement, lime, fly ash and gypsum) are generally used to improve the mechanical properties of the soils. The applicability of most of these traditional stabilizers of soil is limited to particular soils. Moreover, traditionally stabilized soils in some cases exhibit high brittle behavior, which is oftentimes inappropriate for projects such as airport runways and embankments of railroads. This article presents the results of a research study in which an alternative stabilizer -Lignosulfonate (LS)- is investigated. Several basic properties of high plasticity clay, such as Atterberg limits, proctor compaction, unconfined compressive strength (UCS), effect of cyclic wetting/drying on the strength properties, stress-strain behavior and secant modulus of elasticity ( E 50 ) are assessed. To clarify the strength development due to the LS-treatment, scanning electron microscopy is performed on LS-treated and untreated clay. The LS contents were 0.5, 0.75, 1, 2, 3 and 4% by weight of the dry soil and specimens were cured for 0, 4, 7, 14, and 28 days. Results show that the LS-treatment leads to a considerable reduction in plasticity index (PI) of the soil. Also, stabilization with LS has slightly increased the optimum water content and slightly decreased the maximum dry unit weight of the soil. This stabilization has increased the stiffness and UCS of the soil without leading to a considerable brittle behavior. The increase in strength properties is ascribed to the electrostatic reaction that occurs between the mixture of LS-water and soil particles.

Analysis of features of stainless steels in dissimilar welded joints in chloride inducted corrosion

Stainless steels of femtic-austenitic microstructure that means the duplex Cr-Ni-Mo steels, in comparison with austenitic steel includes less expensive nickel and has much better mechanical properties with good formability and corrosion resistance, even in environments containing chloride ions. Similar share of high chromium ferrite and austenite, which is characterized by high ductility, determines that the duplex steels have good crack resistance at temperatures up to approximately -40°C. The steels containing approximately 22% Cr, 5% Ni, 3% Mo and 0.2% N crystallizes as a solid solution δ, partially transforming from the temperature of about 1200°C to 850°C into the phase α. The stable structure of considered steels, at temperatures above 850°C, is ferrite, and at lower temperatures the mixture of phase γ+α +σ. The two-phase structure α+γ the duplex steel obtains after hyperquenching at the temperature of stability of the mixture of α+γ phases, and the share of the phases depends on the hyper quenching attributes. Hyperquenching in water, with a temperature close to 1200°C, ensures the instance in the microstructure of the steel a large share of ferrite and a small share of the high chromium austenite. This causes the increase of strength properties and reducing the plasticity of the steel and its resistance ability to cracking and corrosion. Slower cooling from the mentioned temperature, for example in the air, enables the partial transformation of the a phase into the γ one (α → γ) and increasing the share of austenite in the steel structure. It leads to improvement of plasticity properties. In the paper are presented the results of investigations of heteronymous welded joints of duplex steel and austenitic one. The results include the relation between the chemical composition of steels and their weldability.

Study on the strength characteristics of High strength concrete with Micro steel fibers

The study of High Strength Concrete (HSC) has become interesting as concrete structures grow taller and larger. The usage of HSC in structures has been increased worldwide and has begun to make an impact in India. Ordinary cementitious materials are weak under tensile loads and fiber reinforced cementitious composites (FRCCs) have been developed to improve this weak point. High Strength concrete containing Alccofine as mineral admixture and reinforced with micro steel fibers were cast and tested to study the mechanical properties. The concrete were designed to have compressive strength of 60 MPa. Mixtures containing 0% and 10% replacement of cement by Alccofine and with 1%, 2% and 3% of micro steel fibers by weight of concrete were prepared. Mixtures incorporating Alccofine with fibers developed marginal increase in strength properties at all curing days when compared to control concrete.

Effect of Molybdenum on Microstructure, Mechanical Properties, and Hydrogen Induced Cracking Resistance of Pipe Steel Plates

The effect of molybdenum in an amount of 0.15% on the microstructure and properties of low-alloy pipe steel plate prepared by controlled rolling technology with accelerated cooling is studied. A favorable effect is established for molybdenum on increasing strength properties and sheet hydrogen induced cracking resistance.

The increase of strength properties at nanocrystal formation

To obtain a correct estimate of the microhardness dependence on the size of nanocrystals, the microhardness of amorphous-nanocrystalline samples with the same fraction of the crystalline phase and the same composition of the amorphous matrix but different sizes of nanocrystals was studied. It is shown that the dependence of microhardness on the nanocrystal size in the size range from 5 to 15nm obeys the inverse Petch-Hall law and corresponds to different mechanisms of interaction nanocrystals with shear bands.

Physical and strength properties of Bambusa striata

Strength properties of round bamboo Bambusa striata were determined under static bending and compression parallel to grain tests in air dry and green conditions taking with node and without node at centre of the test specimens from bottom, middle & top portions of the culms. The results show that strength properties i.e. fibre stress at elastic limit (FS at EL), modulus of rupture (MoR), modulus of elasticity (MoE), and maximum crushing stress (Max. CS) are always found higher in air dry than green condition. The presence of node at the centre of the specimen increases strength properties i.e. FS at EL, MoR, and MoE (except Max. CS) significantly in green condition. However difference in ‘Max. CS’ determined in presence and absence of node at the centre of the specimens is found to be statistically non –significant at 95% confidence level. The result also indicates that strength properties occurs maximum at the top and minimum at the middle portion and wall thickness minimum at top and maximum at bottom portion of the bamboo. Bambusa striata species has also been classified (strength wise) on the basis of MoE, MoR, and Max. CS in green condition and found to fall in Group-III for construction purposes.

СТРУКТУРА И СВОЙСТВА ПОВЕРХНОСТИ НАПЛАВКИ, ОБЛУЧЕННОЙ ИНТЕНСИВНЫМ НИЗКОЭНЕРГЕТИЧЕСКИМ ИМПУЛЬСНЫМ ЭЛЕКТРОННЫМ ПУЧКОМ

To substantiate the selection of a coatings material conforming to the operating conditions of the products and the subsequent electron-beam processing conditions, the authors studied the microhardness, Young’s modulus and the microstructure of modified surface layer deposited on the martensitic low-carbon Hardox 450 steel with the high-carbon powder wires of various chemical composition (No. 258 (NbC-G), No. 720 (DT-DUR), No. 760 (DT-DUR)) and further modified by the irradiation with the intense pulsed electron beam using the two-step method. The formation of fused layer on steel surface was carried out in the shielding gas environment containing 98 % Ar, 2 % CO 2 , with the welding current of 250–300 A and the arc voltage of 30–35 V. The modifying of a fusion layer was carried out by irradiating the fusion layer surface with a high-intensity electron beam in the mode of melting and high-speed crystallization. The load on the indenter was 50 mN. The Young’s modulus microhardness was determined in 30 arbitrarily selected points of the modified surfacing surface. The structure of modified by electron beam surfacing surface was studied with the scanning electron microscopy methods. It is determined that the increase in strength properties of the modified by the electron beam weld layer is caused by the formation of a sub-microsized structure, the hardening of which is caused by the quenching effect and the presence of the second phase inclusions (borides, carboborides, carbides). It was found that the maximum hardening effect is observed when surfacing with a flux-cored wire containing 4.5 % of boron. The study shows that the microcracks systems are formed on the surfacing surface formed by a wire, the elemental composition of which includes 4.5 % of boron, and additionally irradiated with the intense pulsed electron beam. While the surface surfacing formed by the powdered wires free of boron after the pulsed electron beam treatment demonstrated the absence of microcracks on the modified surface. The authors determined the significant spread in nanohardness and Young’s modulus values that was apparently conditioned by the nonuniform distribution of strengthening phases.

Влияние легирования на свойства высокоотпущенных сталей, применяемых для производства обсадных труб

The effect of alloying on the properties of high-tempered steels used for production of casing pipes is studied. The steels contained 0.25 %C, 0.9 %C and different amounts of Mo, V and Nb. It is shown that an increase in the molybdenum content from 0.15 to 0.53 % provides a noticeable increase in the mechanical characteristics of chromium-molybdenum steels after tempering at 600–690 °C. Vanadium and niobium addition (about 0.03 %) results in a further increase of strength properties. The highest hardening of steel with 0.32 % molybdenum in tempered state is provided by complex alloying with niobium and vanadium, which results in the same strength as that of 0.53 % Mo steel without additional alloying. V-notch impact toughness at –60 °C for all steels tempered at 660–690 °C is sufficiently high (150–280 J/cm2). The same is true for tempering at 600 °C with the exception of the vanadium-niobium steel.

Features of Nonmetallic Inclusion (Precipitates) Evolution During Heating of Structural Steel for Rolling

Evolution of nonmetallic inclusions on heating a billet for rolling is studied using contemporary methods of electron microscopy and local x-ray spectral analysis for steels 20-KSKh and 13KhFA from an industrial melt. It is established that it is controlled by the occurrence of three main processes. The first consists in the deposition of manganese sulfide on the surface of aluminum-magnesium spinel and other oxide composites MgO–Al2O3–CaO both from solid solution and from soluble MnS precipitates, as a result of which inclusions become corrosion-active and their amount increases. An increase in metal heating duration leads to the coalescence of sulfide components from smaller to larger sizes. As a result of this, the number of inclusions exhibiting corrosion activity decreases. The majority of titanium nitride inclusions are retained with the metal composition outside a dependence on billet heating temperature and duration, and there may be formation of complex TiN inclusions with niobium nitride, with calcium and manganese sulfides, and also of even more complex composition, including aluminum-magnesium spinel, and these inclusions may have an unfavorable effect on the steel’s properties. In contrast, a favorable process is deposition during subsequent cooling on the surface of sulfide and other forms of inclusions of cementite and other carbides, which may lead to a marked increase in strength properties without a reduction in steel ductility. On the basis of results obtained, a number of effective production methods are suggested for improving steel resistance to local corrosion and other service properties.