High Mechanical Characteristics Research Articles

Mechanical and corrosion performance of WAAM printed steel structure

Wire plus arc additive manufacturing (WAAM) is rapidly growing into a popular and cost-effective technology for manufacturing medium-large complex structured components. WAAM is a novel metal additive manufacturing method that deposits material layer by layer using an electric arc as a heat source, allowing the creation of metal components with high mechanical characteristics. The procedure allows for the construction of a near-net-shape structure at a rapid pace of production (50–130 gm/min) and material utilization efficiency (80–90 %). The present study mainly focuses on the fabrication of the WAAM structure and a detailed investigation of the mechanical and corrosion performance of multi-layer fabricated wall components. The most versatile and widely applicable stainless steel SS316L material is employed to build multi-layered wall structures. The average micro-hardness of the WAAM-built structure along the building direction was found to be 197.43±1.46 HV0.3 and that of the commercially available counterpart was found to be 187.26±1.17 HV0.3. Moreover, the maximum hardness was observed close to the bottom region (201.86±1.44 HV0.3) which further reduces with the building height. The ultimate tensile strength, and yield strength of the WAAM printed wall obtained as 573.81±2.3 MPa, and 275.41±1.1 MPa respectively found to have improved mechanical strength to that of wrought counter-part however the ductility in the form of percent elongation gets slightly reduced. Furthermore, comparable corrosion resistance was observed for the WAAM fabricated wall structure and conventionally manufactured SS316L structure. The bottom region experiences better corrosion resistance compared to the upper region in both saline environment and acidic corrosion solution with an average corrosion rate of 0.0276 mm/yr, and 0.0366 mm/yr respectively.

Facile Fabrication of Linezolid/Strontium Coated Hydroxyapatite/Graphene Oxide Nanocomposite for Osteoporotic Bone Defect

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67% and 121%, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ's physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

Microstructural Investigations of Weld Deposits from Manganese Austenitic Alloy on X2CrNiMoN22-5-3 Duplex Stainless Steel

Duplex stainless steels are materials with high performance under mechanical stress and stress corrosion in chloride ion environments. Despite being used in many new applications such as components for offshore drilling platforms as well as in the chemical and petrochemical industry, the automotive industry, etc., they face issues of wear and hardness that limit current applications and prevent the creation of new use opportunities. To address these shortcomings, it is proposed to develop a hardfacing process by a special welding technique using a universal TIG source adapted for manual welding with a pulsed current, and a manganese austenitic alloy electrode as filler material. The opportunity to deposit layers of manganese austenitic steel through welding creates advantages related to the possibility of achieving high mechanical characteristics of this steel exclusively in the working area of the part, while the substrate material will not undergo significant changes in chemical composition. As a result of the high strain hardening rate, assisted mainly by mechanical twinning, manganese austenitic alloys having a face-centered cubic crystal lattice (f.c.c) and low stacking fault energy (SFE = 20–40 mJ/m2) at room temperature, exhibit high wear resistance and exceptional toughness. Following cold deformation, the hardness of the deposited metal increases to 465 HV5–490 HV5. The microstructural characteristics were investigated through optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and Vickers hardness measurements (HV). The obtained results highlighted the feasibility of forming hard coatings on duplex stainless steel substrates.

Pearl-inspired self-extinguishing, thermal-conductive, and robust thermoplastic polyurethane composite by strengthening inter-layer packing

Fabricating thermoplastic polyurethanes (TPU) that exhibit self-extinguishing properties alongside strong mechanical characteristics and high thermal conductivity represents a challenging yet imperative endeavor within both scientific research and industrial applications. Enhancing the thermal conductivity of composites necessitates meticulous attention to surface treatment and the orientation of chemically inert hexagonal boron nitride nanosheets (BNNS). In this study, BNNS are treated by Strengthening inter-layer packing, which enriches the mechanical enhancement mechanism of the “brick-mortar” structure of natural pearl layers. The treatments use copper hydroxyethylidene diphosphonate and melamine hydroxyethylidene diphosphonate, which have a synergistic flame retardancy. Self-extinguishing TPU films with strong mechanical strength (57 MPa) and high thermal conductivity (9.12 W m−1 K−1) are produced when the functional particles are oriented to create multiple synergistic effects with the TPU simultaneously. Furthermore, when comparing CP0.02/MP@BNNS-TPU composite film to BNNS-TPU film, the limiting oxygen index of TPU composites increased to 30.2 %, and there was a significant decrease in both the peak and total heat releases (77.2 % and 80.6 %, respectively), meeting the UL-94 V-0 standard. This work offers a fresh method for creating self-extinguishing materials with high heat conductivity and robust mechanical characteristics.

Biodegradable composites made from maize flour filled with olive husk fibers

The development of biomaterials based on maize flour reinforced with natural fiber was studied with the aim of replacing conventional polymers of petrochemical origin and to simplify assimilated rubbish managing strategies, which reduces the pollution of the environment. In this study, several composites based on plasticized maize flour (PMF) reinforced by the olive husk flour (OHF) in a range from 10% to 40% (wt.%) have been produced with double screw extruder. 15% (wt.%) of low-density polyethylene (LDPE) and graft polyethylene combined with maleic anhydride (PE-g-MA) bonding substance at 5 (wt.%) were added to obtain high mechanical characteristics and improve blend compatibility. Scanning electron microscope (SEM) analysis showed that the fibers were well dispersed in matrix. The Fourier-transform infrared (FTIR) spectroscopy analysis revealed an increase in the absorption bands characteristic of hydroxyl groups and the anhydroglucose ring O-C stretch by raising OHF amount in composites. Thermal stabilization and density of composites increase with the percentage of fiber. For fiber weights of 10 and 40 (wt.%), the tensile strength increased as of 8.4 to 16.4 MPa and the Young modulus as of 70 to 245%, respectively. The biodegradability of samples was tested by burying them in the soil for 90 days. The weight loss test showed that the biodegradability accelerated with the increase in OHF quantity in the PMF. The latter finding was confirmed by FTIR analysis and deteriorated surface of samples examined by SEM analysis.

Targeting Bacterial Nanocellulose Properties through Tailored Downstream Techniques.

Bacterial nanocellulose (BNC) is a biodegradable polysaccharide with unique properties that make it an attractive material for various industrial applications. This study focuses on the strain Komagataeibacter medellinensis ID13488, a strain with the ability to produce high yields of BNC under acidic growth conditions and a promising candidate to use for industrial production of BNC. We conducted a comprehensive investigation into the effects of downstream treatments on the structural and mechanical characteristics of BNC. When compared to alkaline-treated BNC, autoclave-treated BNC exhibited around 78% superior flexibility in average, while it displayed nearly 40% lower stiffness on average. An SEM analysis revealed distinct surface characteristics, indicating differences in cellulose chain compaction. FTIR spectra demonstrated increased hydrogen bonding with prolonged interaction time with alkaline solutions. A thermal analysis showed enhanced thermal stability in alkaline-treated BNC, withstanding temperatures of nearly 300 °C before commencing degradation, compared to autoclaved BNC which starts degradation around 200 °C. These findings provide valuable insights for tailoring BNC properties for specific applications, particularly in industries requiring high purity and specific mechanical characteristics.

Nanocomposite coatings for wear protection at high temperatures

The investigation results of friction and wear of the developed detonation composite coatings FeAl2-Ti-Si-B under high-temperature friction conditions are presented. The choice of FeAl2-Ti-Si-B composition and its optimal content for spraying wear-resistant coatings loaded with friction under high-temperature conditions are justified. It is noted that the alloying elements at definite concentrations and technological parameters of spraying have a positive influence on the structure, properties, and quality assurance of multicomponent coatings. It is shown that the introduction of silicon and boron contributes the formation of hard-alloy high-temperature compounds with increased wear resistance. The maximum microhardness corresponds to the Cr-Si coatings with ~ 28 % titan content. In addition, the mechanical properties of the obtained material are improved by additional alloying of ~ 22 % silicon and bor. In turn, the coatings plating at a working gas flow rate in a ratio for acetylene ~ (20/25) l/min and oxygen ~ (22/27) l/min provides the chemical composition and spraying process parameters permanence as well as constant properties of coatings. The obtained results show that for the coatings of FeAl2-Ti-Si-B system at loading 5.0 MPa, sliding speed 1.5 m/s, and temperature up to 650 °C the stable performance of structural adaptability, which ensures the friction and wear parameters minimization, is demonstrated. The metallographic analysis and strip chart recording of specimens indicate that the friction surfaces are characterized by the absence of visible defects; the separate cold-welded regions are located in thin-film surface layers. The composition, structure, and tribological durability of coatings produced from the elements of the country's resource base were studied; their high adhesion, physical and mechanical characteristics and wear resistance under high-temperature conditions were defined. The thin-film surface structure patterns and properties were investigated with the help of modern physical and chemical methods of analysis. It was determined that the combination of mechanical, physical, and chemical properties of the investigated coatings provides vide opportunities for their usage as effective materials under high-temperature wear conditions. According to the test results, the application of the investigated composite coatings for friction unit efficiency improvement provides their operational reliability in accordance with requirements and opportunities that appear with the development of a new competitive material for wear-resistant coatings obtained with the help of the detonation method. Keywords: detonation coating: wear resistance, surface layer, structural adaptability, temperature.

Investigation of the stress–strain state of a composite blade in ANSYS WorkBench

In this paper, the static strength of a UAV blade made of composite material was calculated. Composite materials have an advantage over traditional materials (metals and alloys) in the field of aviation - gain in weight, low sensitivity to damage, high rigidity, high mechanical characteristics. At the same time, the identification of vulnerabilities in a layered structure is a difficult task and in practice is solved with the help of destructive control. Composite materials available in the ANSYS materials library were used in the modeling: Epoxy Carbon Woven (230 Gpa) Prepreg woven carbon fiber in the form of a semi–finished prepreg impregnated with epoxy resin carbon fiber with Young's modulus E=230 GPa and Epoxy Carbon (230 Gpa) Prepreg is a unidirectional carbon fiber prepreg impregnated with epoxy resin with a Young's modulus E=230 GPa. Modern software products, such as ANSYS WorkBench, allow comprehensive investigation of the layered structure. Several variants of blade designs with different fillers as the median material were investigated. The forward and reverse destruction criteria based on the Tsai-Hill theory were used. The influence of gravity was not taken into account. It is shown that the developed blade design meets the requirements. Balsa wood, pine, aspen and polyurethane foam were chosen as the middle material of the blade. Pine and aspen wood were selected according to the criteria of their availability and having the lowest density. The materials library of the ANSYS WorkBench software package used does not have characteristics for all of them, so the characteristics of the selected materials (pines and aspens) were added manually. For modeling and calculations in the ANSYS WorkBench program, such characteristics as density, axial elastic modulus, Poisson's coefficients, shear modulus and tensile and compressive strength limits are required.

High ductility of Be–Al alloy fabricated by investment casting

Here, we present a high ductility of the Be–Al alloy manufactured by investment casting. It was superior to most Be–Al based alloys reported so far, exhibiting high yield strength of 53∼58 MPa, ultimate tensile strength of 111∼117 MPa, and high tensile strain of 14.1–18.8 %. The many < c + a> dislocations in the Be phase were primarily responsible for the exceptionally high mechanical characteristics. A high Schmid factor for pyramidal slip led to slip transfer between the Be grains and Al grains, which may contribute to relieving stress concentration and delaying early fracture.The profuse activated pyramidal < c + a> dislocations could render the unusual high tensile strain. The high strength was attributed to both the good interfacial strength and the constraint of hard Be phase, which makes the soft Al phase strong like the hard Be phase. It demonstrates the strong texture microstructure design of the Be phase had a synergistic improvement in the strength-ductility balance, suggesting that this could be a useful tactic for enhancing the mechanical characteristics of Be–Al alloys.

Inserting auxeticity into graphene oxide via bottom-up strategy.

Carbon-based materials that process a wide bandgap, high mechanical performance, thermal stability and adjustable characteristics are in high demand. Auxeticity is one of the factors that helps enhances the mechanical performance. Based on this concept, two stable layered carbon-based materials, namely α-C2O and β-C2O, are proposed. A new mechanism (multi-directional negative Poisson's ratio (NPR) effect) is induced, which is attributed to the interaction of modified pz orbitals between interfacial layers. This effect introduces high mechanical properties into materials. Besides, all layered materials are ultrawide bandgap semiconductors, which endows them comparable dielectric properties to those of diamond. Furthermore, α-BK-C2O would maintain its configuration over 2000 K, thereby guaranteeing extremely high thermodynamic stability. So far, these advantages suggested that these carbon-based layer materials could be used in nanoelectronics, especially in electromechanical devices.

Features of the Behavior of Highly Frost-Resistant Modified Concretes

One of the main criteria of construction is reliability and durability. Therefore, for the implementation of modern construction projects, especially in harsh operating conditions, cement composites with increased resistance to aggressive external cyclic influences are necessary. For the climatic conditions of the Russian Federation, special attention should be paid to ensuring the frost resistance of concrete. Thus, in accordance with GOST 31384–2017 “Protection of concrete and reinforced concrete structures from corrosion. General technical requirements”, for the lowest temperature and under the condition of alternating freezing and thawing of concrete in a saturated state, the frost resistance mark must be at least F2450. In addition, high mechanical characteristics of the materials used, including the modulus of elasticity, are required, for example, in the construction of infrastructure facilities in the Arctic zone of Russia. To ensure these characteristics, effective modifying additives must be introduced into the concrete mix. However, there is evidence in the literature that water-reducing additives of various genesis, with similar values of water reduction, have different effects on the structure of the formed cement stone. Therefore, in order to ensure high durability of concrete, this article will consider the relationship between the emerging structure of cement stone in concrete and its resistance parameters.

FILM MATERIALS BASED ON POLYVINYL ALCOHOL, FILLED WITH SILVER NANOPARTICLES

In the present work polymeric composite films materials based on polyvinyl alcohol (PVA), glycerol and silver nitrate the conducted composites with high mechanical characteristics were created. In the process of composites drying, glycerol acts as a reducing agent and the formation of silver nanoparticles occurs, moreover the reducing take places at room temperature. The AgNO3 content is varied from 0.01 to 30 wt.%. Taking into account the physical-mechanical and conducting properties of composites, it is established that the optimum content of glycerol in the final material is equal to 30 wt%. The formation of metallic silver was confirmed by an appearance of a surface plasmon resonance band at 420-430 nm in UV spectra and the appearance of two diffraction peaks at 38.17° and 44.15° in X-ray diffraction pattern as well, corresponding to the crystallographic planes (111) and (200) of a face centered cubic lattice of Ag0. Dielectric spectroscopy data show that the increasing of glycerol content up to 30-40 wt.% leads to enhance the conductivity by three orders in comparison with the initial PVA. An increase in the silver content resulted in further rise of the conductivity, reaching value of 5.72 10-6 S/cm at 15 wt.% of silver concentration, at room temperature (20 °C). At 100-120 °С, the conductivity was the highest for the composite with 25 wt.% of AgNO3 - 3.67-3.84 10-4 S/cm. The resulting samples had high physical and mechanical properties: relative elongation of about 400%, tensile strength of 32–36 MPa. Studies of the dynamic light scattering of films solution with Ag NPs showed that the smallest size was for the sample with 0.5 wt.% - 6.3 nm.

Preparation of ionic liquid modified graphene and its effect on enhancing the properties of PA6 composites

AbstractIn this study, an ionic liquid (IL) with imidazole and amide groups has been prepared, and used to modify graphene (TSG) by ball milling to fabricate ionic liquid functional graphene (TSG‐IL). During the melt blending process, TSG‐IL forms hydrogen bond with the amide group of PA6, which destroys the hydrogen bond of PA6 itself, enhances the interfacial force between TSG‐IL and PA6 matrix, and improves the dispersion of TSG‐IL in PA6 matrix. There has been some improvement in the mechanical and thermal conductivity of PA6 composites. Additionally, the presence of amide groups makes it easy to form hydrogen bonds between TSG‐IL sheets, thus strengthening the connection between TSG‐IL and each other, which is conducive to the construction of thermal conductivity network. The findings indicate that compares to TSG/PA6 composites with the same filler amount, the TSG‐IL/PA6 composites have better heat conductivity and higher mechanical characteristics. 9 wt.% TSG‐IL/PA6 composite has the highest thermal conductivity (0.498 W·m−1·k−1), which is 92.3% and 17.2% greater than that of pure PA6 and 9 wt.% TSG/PA6, and its impact strength (11.12 kJ/m2) is 11.0% and 7% higher, which would be a popular candidate material in the field of thermal conductivity.Highlights Imidazole ionic liquids with amide groups was synthesized. Amide groups were modified onto graphene sheets by ball‐milling. The dispersion of TSG‐IL in PA6 was studied. Improved mechanical property and thermal conductivity of TSG‐IL/PA6 composites.

PROPERTIES INVESTIGATION OF POLYESTER RESIN COMPOSITE MATERIALS AND PRODUCTS

The use of composite materials in construction is a promising direction due to their potential to reduce costs and improve the operational characteristics of building structures. The results of this study will allow to determine the optimal formulations and manufacturing technologies of polymer composite materials for use in construction. In this paper, a detailed analysis of the composite material based on polyester resin (polymer sand concrete) used for the manufacture of hatch covers for manholes in water supply and sewage systems is carried out. The main components of the considered composition are quartz sand, unsaturated polyester resin, hardening accelerator - cobalt naphthenate solution and hardener - benzoyl peroxide. As part of the study, the improvement of the composite material’s properties is also considered by adjusting the technological modes of formation. Special attention was paid to the analysis of the hardness of the samples after the research, since this parameter determines the resistance of the material to wear. The effect of different ratios of these components on the physical and mechanical properties of the final material was studied. It was experimentally determined how the consumption of polyester and hardener affects the compressive strength, bending strength, impact toughness and hardness of the composite material. To obtain optimal characteristics, the STATISTICA 12 software package was used to specify the values of the factors that lead to maximum compressive and bending strength. The results of the research are presented in the conclusions in the form of quantitative indicators that indicate the optimal composition to achieve high physical and mechanical characteristics. The response surfaces of the variation factors’ influence on the properties of interest are shown. Keywords: composite material, polymer sand concrete, quartz sand, polyester resin, hardening accelerator - cobalt naphthenate solution and hardener - benzoyl peroxide

Mix design optimization of metakaolin-slag-based geopolymer concrete synthesis using RSM

Geopolymers have attracted considerable attention recently due to their promising environmental and economic benefits. This study used alkali activation to create an environmentally friendly material with good workability and high mechanical qualities from metakaolin from Oulmès, Morocco, and SONASID-Jorf steel factory slag (BFS). The authors optimized geopolymer synthesis using mixture design and Response Surface Methodology. The results demonstrate the importance of components in ANOVA modelling. This is evidenced by the high experimental Fisher factor (FCv = 16.8916 and FSt = 20.5902), which exceeds the critical value of the Fisher factor (Fc = 15.52) according to the F-test. In addition, the high values of the coefficient of determination (R2) and the adjusted coefficient of determination (R2Adj) indicate strong correlations between the experimental and calculated values (R2Cs = 95.48 % and R2Adj-Cs = 89.83 %, and R2St = 96.26 % and R2Adj-St = 91.58 %). Furthermore, the response surface analysis in the range of variables suggests that metakolin, blast furnace slags, and alkaline activation solution are best for the synthesis of a 35.31 MPa geopolymer. Under ideal conditions, Fourier transform infrared spectroscopy (FTIR) revealed bands associated with the asymmetric strain modes Si–O–Si and Al–O–Si in the metakaolin-BFS-based geopolymer. Similarly, X-ray diffraction (XRD) analysis shows a remarkable peak between 15° and 40° in 2Ɵ, indicating a significant growth rate of the amorphous phase corresponding to geopolymer formation. This study shows that design of experiments and response surface methods can optimize geopolymer synthesis, producing a material with high mechanical characteristics and good workability.

Effects of hydroxyapatite-coated porous titanium scaffolds functionalized by exosomes on the regeneration and repair of irregular bone.

As a traditional bone implant material, titanium (Ti) and its alloys have the disadvantages of lack of biological activity and susceptibility to stress shielding effect. Adipose stem cells (ADSCs) and exosomes were combined with the scaffold material in the current work to effectively create a hydroxyapatite (HA) coated porous titanium alloy scaffold that can load ADSCs and release exosomes over time. The composite made up for the drawbacks of traditional titanium alloy materials with higher mechanical characteristics and a quicker rate of osseointegration. Exosomes (Exos) are capable of promoting the development of ADSCs in porous titanium alloy scaffolds with HA coating, based on experimental findings from in vitro and in vivo research. Additionally, compared to pure Ti implants, the HA scaffolds loaded with adipose stem cell exosomes demonstrated improved bone regeneration capability and bone integration ability. It offers a theoretical foundation for the combined use of stem cell treatment and bone tissue engineering, as well as a design concept for the creation and use of novel clinical bone defect repair materials.

3D g-C3N4 porous nanoribbons pillared-MXene/ PVA nanocomposite: An architecture with high dielectric, breakdown strength, thermal conductivity, and mechanical strength characteristics

In polymer nanocomposites with conductive fillers, obtaining boosted dielectric constant, breakdown strength, lower dielectric loss concurrently, and mixing to build a homogeneous structure is challenging. In this work, 3D g-C3N4 porous nanoribbons pillared-MXene/PVA nanocomposite (MXene/CNNR/PVA) was fabricated. The solution casting method was utilized for embedding Mxene/CNNR into poly (vinyl alcohol) (PVA) to produce MXene/CNNR/PVA dielectric composites. The maximum observed electrical displacement is 10.95 μC/cm2 at (T = 25 °C and E = 400 MV/m). Furthermore, the obtained density of discharged energy is 18.11 J/cm3, much higher than that of pristine PVA (4.21 J/cm3 at E = 200 MV/m). The relative permittivity of 3.5 wt% ternary composites (MXene/CNNR/PVA) at 25 °C and 1000 Hz is 25.1, and the loss is just 0.03. Moreover, the combined use of MXene and CNNR results in a synergistic effect; the MXene/CNNR/PVA composite films exhibit more incredible mechanical characteristics compared to pure PVA nanocomposite modified by MXene alone, with notable increases in tensile strength and Young’s modulus while retaining the majority of its elasticity.

Research of Nano-modified Plain Cement Concrete Mixtures and Cement-Based Concrete

The use of complex modifiers for plain cement concrete mixtures and concrete is becoming increasingly popular in modern materials science. The article presents studies of the influence of a polymer additive structured by carbon nanomaterials on physical and mechanical characteristics of plain cement concrete mixtures. IR spectroscopy and thermogravimetry have shown that the use of carbon nanomaterials significantly altered the structure of plain cement concrete mixtures. As a result of the fact that the high-strength nanomaterial is the center of crystallization of cement rock newly formed structures, a denser reinforced microstructure is formed, which significantly increases the strength properties of plain cement concrete mixtures. The inclusion of a polymer complex additive in plain cement concrete mixtures leads to higher and longer plasticizing, which plays an important role in the production of monolithic products. It was determined that, in the presence of a complex modifier (polymer additive structured by carbon nanotubes), the crystalline structure of calcium hydrosilicates is compacted, which causes high physical and mechanical characteristics of modified plain cement concrete mixtures. It has been experimentally shown that the additive Ethacryl HF (France) from the class of polycarboxylates, chosen for research, acts as an accelerator for setting and curing cement paste, and also increases its strength characteristics. In general, in this study, there is a water-reducing effect from the application of the additive for all plain cement concrete mixtures. Water requirements are reduced by 5 mas. %, while the strength is increased by 19%. The formulation of plain cement concrete mixtures modified by polymer additives, structured by carbon nanotubes, with high performance were developed.

Masonry Wall Reinforcement

Unreinforced masonry has been used as a construction material for thousands of years. Whilesome of these structures survive to this day, these tend to have massive walls and would be unpractical formodern use. Unreinforced masonry can be reinforced with proper masonry techniques. As a result,reinforced and confined types of masonry were developed to exploit the strength potential of masonry andto solve its lack of tensile strength, significantly improving not only resistance, but also ductility andenergy dissipation capacity.Fiber reinforced polymer composites have emerged as an effective means of reinforcing masonrystructures due to their high mechanical characteristics, low weight and durability. The role of FRPmaterials is to act as a tensile reinforcement which can be used to improve the ability of a wall against inplane shear and/or out-of-plane bending.This contribution, based on experimentation and numerical modelling, aims at a better understanding ofthe behaviour of structures in masonry. Multiple reinforcement techniques and methods are illustrated inthis summary, such as the reinforcement of masonry walls by composite materials like CFRP (CarbonFiber Reinforced Polymer) and glass fibre reinforced polymer (GFPR), also there are Near surfacemounted (NSM), carbon fibers reinforced polymer (CFRP) and other techniques are cited in this work.

Tribologic behavior and surface integrity of NAB bronze coatings reinforced with WC and Cr3C2 carbides using ytterbium fiber laser

Nickel-aluminum bronzes (NAB) are widely used in different applications due to their high mechanical properties and operational characteristics. These properties can be further improved using different finishing processes. This paper’s objective involves the wear and surface integrity characterization of CuAl7Ni6P bronze coatings formed firstly by plasma spraying and then by laser alloying with WC and Cr3C2 carbides. The YLR-2000 fiber ytterbium laser was used for laser processing and the effect of process conditions, namely a laser spot speed (LSS) and a square of the laser spot (SLS)was studied under 500 N and 1000 N loads. It was revealed that processing parameters do not have a significant effect on microhardness and friction process factors, but have significant effect on carbide alloying results. Under load of 500 N wear rates have an advantage up to 5–6 times regardless of the processing parameters and the type of reinforcing particulates. Under load of 1000 N alloying advantage is very high: 15–20 times using Cr3C2, and even 30–50 times using WC compared with results obtained for plasma spraying. These results are very important when choosing NAB laser processing input parameters in industrial applications.