Structural Materials Research Articles

Alloying effects on deformation induced microstructure evolution in copper

In this work, we investigated the effects of alloying elements on plastic deformation and microstructure evolution in polycrystalline copper (Cu) and Cu alloyed with 1 wt.%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document} lead (Cu-1%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}Pb). These materials were selected due to the size mismatch between Cu and Pb, with the latter forming precipitates at grain boundaries. Multi-modal characterization techniques, including neutron diffraction, electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), along with finite element simulations were employed to study the deformation behavior across multiple length scales. While both Cu and Cu-1%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}Pb exhibited similar macroscale response and final deformation textures, both dislocation line profile analysis and TEM revealed increased dislocation density in deformed Cu-1%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\%$$\\end{document}Pb specimens. The presence of lead precipitates also significantly affected local plastic deformation during compression, with their influence diminishing with increasing strain. These results demonstrate the complex relationships between alloying elements, plastic deformation, microstructural evolution, and material behavior under load. The insights gained from this multi-scale and multi-technique approach contribute to the fundamental understanding of microstructural evolution in immiscible alloys and are valuable for tailoring the properties of structural materials for specific engineering applications.

Study on the folding damage mechanism of SiC fiber braided fabric based on synchrotron radiation CT and finite-element analysis

Silicon carbide (SiC) fiber exhibits high strength, thermal resistance, and chemical stability, but its insufficient flexural strength renders it unsuitable for use in flexible structural materials. In this study, the microstructure evolution and damage mechanisms of SiC fiber braided fabric were investigated at different braiding angles and folding stages using synchrotron micro computed tomography (µ-CT) and finite-element analysis. Results from synchrotron radiation CT scans indicate that, with an increase in the number of folding cycles, both fiber surface fractures and slippage gradually increased, leading to a looser internal structure and diminished fiber continuity. The SiC fiber braided fabric at 37.8° was predominantly influenced by the folding behavior, exhibiting a higher frequency of fiber breakages. Conversely, the 43.1° SiC fiber braided fabric was primarily affected by inter-bundle abrasion, resulting in looser fiber bundles and increased slippage. In the case of the 41.2° SiC fiber braided fabric, under the combined effects of friction and folding, the highest occurrences of fiber slippage and breakages were observed. Finite-element simulation results reveal that the stress at the folding site of the 40° braided fabric was higher than those of the 45° and 50° braided fabrics, confirming the experimental conclusion that the folding resistance of SiC fiber fabrics is poorest at a braiding angle of around 41° to 42°. This research is of significant importance for a deeper understanding of the folding performance and damage behavior of SiC fiber braided fabric, providing valuable insights for further optimizing material design and applications.

Force Measurement Standards Up to 1 MN and Above

The use of force measurements standards ensures testing of load and force sensors designed for measuring and studying large loads in rocket science, nuclear power plant construction, and testing of structural materials. The article provides an overview of the State Primary Standard of force GET 32–2011 of the Russian Federation in the range up to 1 MN, and also analyzes international experience in the field of reproduction of the unit of force with a value above 1 MN. The range of reproduction and composition of loads of the deadweight machine EU-100 from the composition of the State Primary Standard of force GET 32–2011 of the Russian Federation, deadweight machine of the Physical-Technical Federal Institute (PTB, Germany), deadweight machine of the National Institute of Standards and Technologies, deadweight machine of the Fujian Institute for Metrology (FPIM, China) and the deadweight machine of the Korea Research Institute of Standards and Science (KRISS, Republic of Korea) were assessed. The article is of scientific and practical interest to specialists in the field of reproduction of the unit of force of large values. The generalized experience can become the basis for research in the field of improving the standards of force. The review is also addressed to teachers and students of specialized disciplines of higher education.

Sintering polycrystalline silicon carbide composite ceramics with ultra-high hardness under high pressure

Silicon carbide (SiC) is an important structural ceramic material, exhibiting exceptional comprehensive properties that are unmatched by metals and other structural materials. In this study, a combination of α-SiC micron powder and β-SiC nanopowder was utilized as precursor materials for high pressure and high temperature (HPHT) sintering. Under a pressure of 5.0 GPa, polycrystalline SiC samples with mixed grain size were sintered within a temperature range from 1000 to 1700 °C, and compared with SiC samples sintered from single micron powder under identical temperature and pressure conditions. The microstructures of the two sets of SiC samples were observed using scanning electron microscopy. Additionally, the stress states and strengthening mechanisms among SiC grains with mixed grain size under HPHT were further analyzed in conjunction with X-ray diffraction results. The polycrystalline SiC composite ceramics sintered at 1700 °C exhibited superior mechanical and thermal properties, achieving a Vickers hardness of 35.2 GPa that is 23.5 % higher than that obtained by conventional spark plasma sintering and even surpassing the hardness of single crystal SiC, demonstrating thermal stability up to 1405 °C in air environment. Transmission electron microscopy was employed to analyze defects and plastic deformation in these samples. The study suggests that the primary strengthening mechanisms of the sintered polycrystalline SiC composite ceramics under HPHT include the increase in micro defects induced by in-situ plastic deformation at elevated temperatures and the effects of high-temperature creep. This study provides new insights into the HPHT sintering of hard materials.

Thermal Conductivity Measurement System for Functional and Structural Products

An automated system for measuring the thermal conductivity of functional and structural materials was developed. The main building blocks of the setup are the following: heating unit and cooling unit creating a heat flux gradient in the test sample; thermal resistances for temperature registration and control; and thermal pads for better contact between parts of the setup and the sample. The effect of the thermal conductivity of thermal pads and thermal resistances on the distribution of thermal fields in the developed setup was studied by computer modelling. A control software for the measuring setup was developed based on the hardware implementation of the steady-state Fourier’s law-based method for the determination of thermal conductivity. The stopping criterion for the setup control software is the equality of heat fluxes in the heating and cooling units, as well as the stability of the thermal conductivity coefficient readings. The testing and calibration of the device were carried out using a sample of pure aluminum (99.999 wt.% Al). It was found that the experimental value of the thermal conductivity coefficient of the aluminum sample at room temperature (T = 22 °C) is <λ> = 243 ± 3 W/m·K. This value of the thermal conductivity coefficient is consistent with the literature data and experimental values obtained by the laser flash method, which ranges within λ = 210–260 W/m·K.

Extraction and Physicochemical Characterization of Chitin from Galeodes araneoides (Pallas, 1772) (Arachnida: Solifugae)

: Chitin is a biomaterial which has a high potential of use in many areas of technology. It is found as a structural material in the outer skeletons of arthropods, the cell walls of mushrooms, and the shells of marine invertebrates. Chitin is the most abundant biopolymer in nature after cellulose and contains nitrogen in its structure. In recent years, apart from traditional chitin sources, insects, arachnids, coral/crustacean eggs and even bat guano have been reported as alternative chitin sources. In this study, chitin was first extracted from external skeleton of a solifugids species, Galeodes araneoides (Pallas, 1772) and the isolated chitin was characterized by SEM, FTIR, XRD, and TGA. The obtained chitin has been found to have high thermal stability, nanofiber and nanoporous surface, and alpha form and it is suggested that it can be an alternative chitin source.

Algorithms and software for processing images of the structure of metallic materials for the purpose of determining creep characteristics

The paper contains a description of the approach, algorithms, and software tool for image analysis of deformed material structures. The developed approach is based on the analysis of the microstructure of the material to identify important factors that affect high-temperature deformation during creep in a heat-resistant nickel-based alloy, namely, the dimensions of the channels and their orientation. The developed software tool uses algorithms for converting images into binary black and white using the Otsu method. The intensity of the gradient at each point of the image is visualized using the Sobel operator. Fragment boundaries are determined using the Canny edge detector. Straight line segments are found using the Hough transformation. The software tool is implemented in the Python programming language using the OpenCV library. The main components are described and a flow chart of the program is provided. With the use of the developed software, the transformation of the known experimentally obtained images of the structures of the specimens from heat-resistant nickel-based alloy CMSX-4 deformed at a temperature of 1273K and in a wide range of stresses at different time moments was performed. The results of the analysis of the dimensions of the g-phase channels in the alloy using quantitative evaluation of transformed binary images are discussed. The found characteristics were matched to the value of the creep strain rate, which was determined by calculation based on known experimental data. The possibility of determining the transition from the secondary creep to the stage of avalanche-like growth of strains and hidden damage is shown. For the considered example, the location of the channels in the representative image was determined. A technique for correcting creep curves with the involvement of material structure image processing data is proposed.

Safety and security of household water purifiers against pathogenic microbial contamination and bio-risk evaluation of their microbial community structures

Household water filters, particularly point-of-use systems, are crucial to ensure safe drinking water consumption by eliminating microbial contaminants. This study evaluated the efficacy of three types of water purifiers (ultrafiltration [UF], nanofiltration [NF], and reverse osmosis [RO]) against microbial contamination. In our experiments, Escherichia coli and bacteriophage MS2 were used as two microbial indicators in daily household settings to track the spatial and temporal profiles of their behavior from the filter inlets to in-UF, NF, and RO water purifiers, and then to effluents. The results showed that both NF and RO water purifiers removed 100 % of the indicator organisms. The UF water purifier achieved 100 % removal of E. coli, but the removal of MS2 phage was poor. The presence of coexisting ions and natural organic matter in tap water can significantly affect the behavior of MS2 phages during the water treatment process. Their presence reduces the charge repulsion effect of the UF membrane on the MS2 phage as well as promotes the migration of the MS2 phage on the post-activated carbon cartridge that was placed in the last unit of the water purifier system, which could increase the pathogen transmission risks in drinking water supplies. The bacterial community structures of the cartridge materials and cartridge effluents from each unit were analyzed by 16S rRNA gene sequencing, which revealed distinct microbial profiles of the different purifiers. Environmental conditions such as pH, nutrient availability, materials, and operational parameters can affect the composition of bacterial communities. Scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) was used to examine the surface morphology of the membranes after they were exposed to water contaminants, which demonstrated that the inherent differences in the membrane structure influenced the retention of pollutants and microorganisms on the surfaces. In summary, this study demonstrates that both NF and RO water purifiers can significantly reduce the presence of various enteric and opportunistic pathogenic bacteria in drinking water, leading to safer potable water, whereas UF water purifiers may have certain risks owing to their UF membranes and post-activated carbon. In addition, secondary microbial contamination may be introduced by the post-activated carbon units of water purifiers, especially after long-term usage. Therefore, we concluded that addressing the secondary microbial pollution caused by post-activated carbon after prolonged use and long-term shutdown is essential for maintaining the safety and quality of drinking water.

A composite anode based on intercalation and conversion mechanism for high-rate lithium-ion batteries

To increase the specific capacity and cycle stability of lithium-ion batteries at high current density, we have investigated the anode materials. Among them, black phosphorus has attracted attention because of its large theoretical specific capacity (2596 mA h/g). However, the moderate conductivity of black phosphorus itself makes it less effective. The addition of graphite to form P-C and P-O-C bonds with black phosphorus enhances the performance of the battery cell. Lithium ions are primarily stored in black phosphorus-graphite layered structural materials via an intercalation mechanism, which improves electrochemical performance at tiny current density but is inadequate for charge/discharge cycling at high current density. In addition, lithium ions also can undergo conversion mechanism with metal oxide materials (e.g. Tungsten trioxide). While this conversion mechanism enables more stable battery cycling at high current density, the specific capacity remains insufficiently high. Higher charge/discharge specific capacity and long cycle stability of lithium-ion batteries at high current density can be realized by the joint action of the two mechanisms. In this work, black phosphorus, graphite, and tungsten trioxide (BP/G/WO3) composites are prepared by ball milling method. A comprehensive series of electrochemical analyses reveals that the BP/G/WO3-532 electrode (BP, graphite, and WO3 mass ratio of 5:3:2) exhibits the most substantial enhancement in the cycling stability of lithium-ion batteries. The anode exhibits a high specific capacity of 1463.1 mA h/g at 6 A/g and presents a retention capacity of 1159.8 mA h/g after 300 charge/discharge cycles, indicating a high cycle stability and fast reaction kinetics. This result is mainly attributed to the joint action of two mechanisms of composites.

Achieving metallurgical bonding in steel faceplate/aluminum foam sandwich via hot pressing and foaming processes: interfacial microstructure evolution and tensile behavior

This study introduces an innovative approach to fabricating aluminum foam sandwich with aluminized steel faceplates through metallurgical bonding. The process involves the use of foamable precursor, prepared via melt stirring, and subsequent hot pressing and foaming, offering a cost-effective and industrially feasible method for producing lightweight structural materials and connection of steel/aluminum dissimilar metals. This study focuses on exploring the changes in the microstructure of the bonding interface before and after foaming, and revealing the impact of these changes on the tensile results. Foaming experiment shows that foamable sandwiches have superior foaming ability, and the core layer density after foaming is between 0.283 and 0.591 g/cm ³. Microstructural characterization results demonstrate that, during the hot pressing process, fine equiaxed grains are observed on the iron side of the interface, indicating dynamic recrystallization occurred. The formation of a small amount of η-Al5Fe2 at the interface is a primary factor causing the deflection of the fracture path. Subsequently, during the foaming process, intermetallic compounds (IMCs) θ-Al13Fe4, τ5-Al7Fe2Si, and β-Al4.5FeSi formed sequentially, mainly determined by the diffusion reaction of silicon elements. The formation of these IMCs led to an increase in microhardness at the interface and a decrease in shear strength. Digital image correlation was utilized to examine strain distribution under tensile loading. The result indicates that the damage accumulation is characterized by the formation and expansion of strain bands, with failure manifested as the interconnection of these strain bands.

Thermal modification of fast-growing Firmiana simplex wood using tin alloy: Evaluation of physical and mechanical properties

Wood is an important structural material, but some undesirable properties limit its application in construction. This study investigated the effect of tin alloy thermal modification (TTM) on selected physical and mechanical properties of Firmiana simplex (Chinese bottletree) wood. Tin alloy thermal modification of F. simplex was performed in a tin alloy bath at two different temperatures (150 oC and 210 oC for 2 h and 8 h). Physical properties such as swelling, water absorption and density and mechanical properties like modulus of elasticity, modulus of rupture, impact bending, compression strength and Brinell hardness of tin alloy thermal modified and control samples were evaluated. The results showed that tin alloy thermal modification decreased the swelling of the wood to 4,85 %, 1,45 % and 6,99 % along the tangential, radial and volumetric coefficient and water absorption and density decreased to 53,10 % and 290 kg/m3 respectively compared to the control. Modulus of elasticity, modulus of rupture, impact bending, compression strength and Brinell hardness of tin alloy thermal modified F. simplex at 210 °C for 8 h decreased to 6366,1 MPa, 54,9 MPa, 2,7 MPa, 29,4 MPa and 1113,5 MPa respectively compared to the control. In conclusion, the tin alloy thermal modified wood at 210 oC significantly affected the physical and mechanical properties of the wood.

Mass-Producible Transparent Flexible Passive-Cooling Film.

Passive cooling is regarded as the desired method for interior temperature regulation due to its advantage of energy consumption reduction. An ideal passive-cooling window is expected to exhibit a high emissivity in the mid-infrared (MIR, 8-13 μm) spectral range for cooling and a low transmittance in the near-infrared (NIR, 780-2100 nm) spectral range for reducing heat flow, while presenting a high transmittance in the visible (VIS, 400-780 nm) spectral range for daylighting. However, material structures that meet these requirements often come with high demands for precision in manufacturing and elevated processing costs, which have limited their potential for large-scale mass production. Here, we propose a mass-producible transparent flexible passive-cooling film that is relatively easy to process and low-cost and meets all of the requirements mentioned above. The film is made of poly(methyl methacrylate) mixed with Cs0.33WO3 nanoparticles, and it shows a high absorptance (80%) in NIR for blocking solar radiation penetration and a high emissivity (93%) in MIR for radiative cooling as well as a reasonable transmittance (40%) in VIS for visibility. Under solar intensity of ∼900 W/m2, a maximum temperature reduction of 8.4 and 7.8 °C has been achieved for a window coated by the film compared to the uncoated window in the condition of the absorbing chamber and car, respectively. Such a mass-producible transparent flexible passive-cooling film holds promising applications in large windows, such as those used in automobiles and buildings, where there is a high demand for both daylighting and cooling.

A method for optimizing different geometric shields of D-T neutron generators by combining BP neural network and Analytic Hierarchy Process

In this paper, an optimization of shielding structures with different geometries is established for the D-T neutron generator system by combining Back Propagation (BP) neural network and Analytic Hierarchy Process (AHP). The D-T neutron generator (Model NG-9) used in the system was developed independently by Northeast Normal University. After investigating the rule of shielding performance among spherical, cylindrical and cubic geometries, the spherical shield is selected for BP neural network prediction to determine the total dose rate through it. Information about spherical multilayer-shielding structures and properties calculated by MCNP code is used to train the neural network. The predicted result serves as a parameter of the evaluation function, which provides a comprehensive assessment of the dose rate penetrated the shield, the shielding mass, and the shielding volume. Together with AHP, the weight factors are determined for all the optimization objectives to construct the evaluation function. By comparing its values, the optimal shielding structures for spherical, cylindrical and cubic materials are found. Against MCNP simulated values, the total dose rates’ errors of the optimal shielding structures for the sphere, cylinder, and cube are 1.72 %, -4.94 %, and -5.17 %, respectively. This result demonstrates that the combination of BP neural network and AHP is more effective in addressing multi-objective optimization problems related to the design of radiation shielding for various geometries.

Recent progress on wet-oxygen corrosion resistance of SiCf/SiC composites

Being an aero-engine hot-end structural material, silicon carbide fiber (SiCf) reinforced silicon carbide (SiC) ceramic matrix composites (SiCf/SiC) display remarkable application potential. The wet-oxygen environment inside the aero-engine erodes the composites and leads to their performance degradation, which has become a key factor limiting the long-time service of SiCf/SiC. Finding an appropriate way to improve the wet-oxygen corrosion resistance of the composites is worthy of attention. This paper briefly analyzes the mechanisms of wet-oxygen corrosion and reviews the research progress in modified SiCf/SiC from three aspects: coatings, matrix, and interface. At last, the future development trend of the composites against the wet-oxygen environment is prospected.

Fluid-structure interaction mechanism in shear thickening fluid/Foam composite for advanced protective structures

Fluid-structure interaction (FSI) between shear thickening fluid (STF) and soft materials is pivotal in designing advanced protective structures. This study delves into the FSI mechanisms within a composite structure known as STF/Foam, which features the infusion of STF into foam. Through comprehensive drop weight tests, the STF/Foam exhibited exceptional cushioning performance. In addition to analyzing FSI from the perspective of structural materials, this study also examines it from the STF standpoint, enabling a multi-faceted understanding of the energy absorption mechanism. To accurately characterize the rheological properties of STF, a novel decoupling method is proposed, accounting for both temporal and spatial inhomogeneities of STF. The research findings indicate that the viscosity variation of STF significantly enhances the energy absorption capabilities of the STF/Foam composite. This study reveals the intricate fluid-solid coupling mechanism between STF and foam. The STF demonstrates a unique combination of shear resistance akin to high-viscosity fluids and the easy flow characteristics of low-viscosity fluids. The modulation of STF viscosity optimizes the structural deformation pattern, thereby rationalizing the energy absorption mechanism of the composite. Consequently, STF/Foam showcases superior cushioning performance. Further investigation into various parameters associated with STF and foam highlights their influence on the structural cushioning performance. These insights lay a theoretical foundation and provide design guidelines for the future development of STF-based controllable protective structures.

Light-Responsive Smart Nanoliposomes: Harnessing the Azobenzene Moiety for Controlled Drug Release under Near-Infrared Irradiation.

The azobenzene moiety is an intriguing structure that deforms under UV and visible light, indicating a high potential for biomedical applications. However, its reaction to UV radiation is problematic because of its high energy and low tissue penetration. Unlike previous research on azobenzene structures in photoresponsive materials, this study presents a novel method for imparting photostimulation-responsive properties to liposomes by incorporating the azobenzene moiety and extending the light wavelength with up-conversion nanoparticles. First, the azobenzene structure was incorporated into a phospholipid molecule to create Azo-PSG, which could spontaneously form vesicle assemblies in aqueous solutions and isomerizes within 1 h of light exposure. Furthermore, orthogonal up-conversion nanoparticles with a core-shell structure were created by sequentially growing lanthanide rare earths in the shell layer, which efficiently converts near-infrared light into ultraviolet (400 nm) and blue-green (540 nm) light. Combining these core-shell structured up-conversion nanomaterials with Azo-PSG molecules resulted in the creation of a near-infrared light-responsive smart nanoliposome system. Under near-infrared light irradiation, UCNPs emit UV and blue-green light, causing conformational changes in Azo-PSG molecules that allow drug release within 6 h. The reversible structural shift of Azo-PSG in response to light stimulation holds enormous promise for improving drug release techniques. This novel technique also expands the usage of UV-responsive compounds beyond their constraints of low penetration and high biotoxicity, allowing for rapid medication release under NIR light.

Application of Experimental Studies of Humidity and Temperature in the Time Domain to Determine the Physical Characteristics of a Perlite Concrete Partition

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals.

Tribological and investigation study of a dlc-coated H13 friction drilling tool on AZ31B magnesium alloy

IntroductionFriction drilling is an innovative method in hole-making for sheet metal applications, thin sheets of conventional structural alloy materials like copper, titanium, steel etc., even though there are other methods, such as thermal distortion for the welding of nuts, riveting of nuts, and threading. For the last hundred years, researchers have focused on studying the development of this technique to maintain strength, hole roughness, hole geometry, hardness etc. It is interested in finding solutions for wear, tool life, and plastic deformation.MethodFriction drilling is also called a green hole-making process because this process uses the friction between the rotating tool and the workpiece. In this research, instead of regular HSS and Tungsten Carbide tools, the H13 tool steel is used, because the H13 steel tool has unique chemical compositions like chromium and molybdenum, which give high toughness, hot hardness, and wear resistance. Diamond-like-carbon (DLC) coating has been used in this research to enhance tool life and AZ31B magnesium alloy is used as the work material. Initially, in this research, the wear stability of the DLC-coated H13 tool was investigated, and later, the tool surface roughness and hole quality were verified.Results and DiscussionThe material loss observed for the DLC-coated H13 steel tool in the pin-on-disk test was 0.05 g. This investigation used two different diameter tools, namely 3 and 7 mm. Research has concluded that the 7 mm tool is better for friction drilling by seeing the roughness and hole quality. However, the conditions were that the spindle should rotate at 4,000 rpm and the feed rate of the tool to be at 200 mm/rev.

THE MODERN AND PROSPECTIVE STRUCTURAL MATERIALS` FOR WHEELED ARMORED VEHICLES STRENGTH CHARACTERISTICS ANALYSIS

The article presents the results of research in those the modern structural materials` strength characteristics for wheeled armored vehicles (WAV) production, as well as the technical requirements for them, were analyzed. It has been established that ordinary structural steels are used for armored car frames, and special armored steels with high strength and hardness characteristics are used for armored plating. It is expedient to use new promising materials - martensitic steels, which are characterized by extremely high strength, new ceramic materials and glass, and the latest nanomaterials - for the WAV armoring. A military vehicles protection promising direction is modern modular armor protection with the use of various materials.

3D printed PEEK/CF nanocomposites metamaterial for enhanced resonances toward microwave absorption and compatible camouflage

The stealth materials for future weapons and equipment need to operate within the radar working band, be lightweight, easy to process, and compatible with infrared stealth. Integrating all these characteristics poses a significant challenge. This work utilizes poly (ether-ether-ketone)/carbon fibers (PEEK/CF) composite materials and employed reverse-guided manufacturing through simulation design. Incorporating a grid structure within the pyramid metamaterial enables electromagnetic wave reflecting multiple times in various directions. By optimizing the important interaction between dielectric properties of the materials structures，the Pyramid Grid Filled Metamaterial enables broadband electromagnetic wave absorption (<-10 dB, 8–18 GHz), weak angular dependence (5- 45o incidence), polarization insensitivity, radar cross section (RCS) reduction (reduction over 10 dB between θ = −60° and 60°), and infrared camouflage performance. The PGF metamaterial of 180◊180 mm2, weighs only 103.1 g at a thickness of 9 mm. This work paves a way for the design the radar infrared compatible composite metamaterials.