Sheet Material Research Articles

Small Size Broadband Printed Antenna for 5G Applications Covering 28 GHz / 38 GHz and 60 GHz Bands

This work offers the radiation insight of a compact modified monopole rectangular printed antenna suitable for 5G applications. A Double copper cladded RT Duroid 5880 material sheet with dimensions 4.4×5.0×0.5mm3 is chosen as the base substrate in the offered design with a loss tangent of 0.004 and a dielectric constant of 2.2. In the provided strategy lower-left corner of a rectangular printed antenna is made in the form of a smooth circular curve. After extensive simulation, a circular slot with an elliptical patch is incorporated into this monopole antenna. The designed antenna parameters are adjusted to cover the impedance bandwidth from 21.7 GHz to more than 70.0 GHz. Three resonances at 28.0 GHz, 38.1 GHz and 60.2 GHz were observed in three bands allocated for 5G communication applications. The efficiency and gain values found sustained in the entire bandwidth range. Stable and desired radiation patterns at all three resonant frequencies 28/38/60 GHz prove the suitability of this antenna for recent 5G applications.

Analytical description of adjustment of rolls for manufacturing parts from elastic sheet material

The object of research is the process of bending sheet material, taking into account its springiness. When manufacturing sheet parts by bending from a completely elastic sheet, its shape is completely restored after the deformation stops, unlike an elastic sheet. Thus, when producing cylindrical parts by drawing between three rolls, the resulting radius of the cylindrical part will be larger than the calculated one. This phenomenon is evaluated by the coefficient of springing – the ratio of the calculated radius to the one obtained after partial expansion. When manufacturing conical parts, this approach cannot be applied, because the value of the radius is variable. The article applies the theory of surface bending from differential geometry. The curvature of the line on the surface has two components - normal and geodesic. When the surface is bent, the normal component changes, while the geodesic component remains unchanged. The magnitude of the normal component depends on the angle between the origin of the cone and its axis. So, for a cone with a base of radius R and an angle of 20°, the normal curvature is 0.94/R, and the geodesic curvature is 0.34/R. For cylindrical parts, the geodesic curvature of the cross-section (circle) is zero, so it is not necessary to take it into account. Usually, adjustment of rolls for the production of conical parts is carried out experimentally. The difference of the proposed approach lies in the elimination of this problem thanks to the decomposition of the curvature of the base of the cone into two components. This allows to calculate the settings of the rolls and thereby reduce their adjustment time. The parameters of the rolls and their mutual placement are calculated for the production of conical parts of the required size, taking into account their springiness. The field of application of the obtained results is the production of parts by bending flat metal sheet blanks

Promising areas for the use of industrial hemp for the manufacture of sheet building materials

The relevance of the study is to identify the potential for creating innovative building materials that can improve the quality and efficiency of construction and furniture production. The purpose of the study is to analyse the market of sheet building materials, explore the possibilities of using plant materials in construction and furniture industry, and compare the properties of the latest building materials with the existing ones. The analysis of literature sources included a search and evaluation of new developments in the construction industry, as well as an analysis of statistical data on the production of architectural materials in Ukraine, using information resources and Internet search services. To evaluate the consumer properties of innovative building materials, the author used quality assessment methods using visual perception and special tools, in accordance with the established regulatory documentation. Important issues aimed at using resource-saving technologies in construction and developing the latest (environmentally-friendly) building materials are considered. The current state of the Ukrainian market of building sheet materials and the properties of industrial hemp are investigated in order to determine the most cost-effective use of hemp raw materials as an effective basis for the creation of building materials for various purposes. The suitability of the raw materials was determined and assessed, experimental samples of chipboards with different fillers were obtained, and the physical, mechanical and aesthetic characteristics of the finished products were investigated. The research will contribute to the development of the hemp processing industry, as well as enterprises that produce goods for various functional purposes from hemp, which will provide conditions for combining the agricultural sector and the construction industry, i.e. building a closed production cycle

Numerical simulation of heterogeneous ice sheet-structure interaction based on cohesive element method

The coupling process between sea ice and offshore structures is complex, which involves the influences of physical and mechanical properties of sea ice, structural dynamics, and fluid–structure interaction. In this work, a numerical model was established to simulate the ice-structure interactions, which is based on the cohesive element method combined with random field. The complicated spatial heterogeneity of ice sheet materials was considered, and the fracture energy, which is one of the material properties of the ice sheet model, was assumed to be a Gaussian random field. Numerical simulations of the ice sheet-vertical structures interactions were conducted with two mesh patterns, respectively. A more suitable element was adopted to build the heterogeneous ice field to investigate the effect of heterogeneity on the interactions. Moreover, the parametric sensitivity analysis of Gaussian random fields was performed. It has been found that the heterogeneity of ice sheet led to significant uncertainties in the numerical simulations. The location of ice sheet failure and the shape of ice fragments are associated with the distribution of the properties, and the cracks emerge and propagate in those weaker regions. Furthermore, the mean of ice load and the collision frequency show a decreasing trend with an increase in correlation length.

Improving coffee capsules recyclability - A combined assessment of circularity and environmental performance of a novel design

Coffee capsules have gained high levels of popularity in the last decades due to their convenience of use, flavour choices, and consistent extraction quality. As governmental bodies are promoting more circular solutions for packaging products, concerns have been raised regarding the environmental impacts of single-use coffee capsules, namely their end-of-life treatment and effective recyclability. This paper presents a novel design based on thin steel sheet material application for new packaging solutions that can support a more circular economy. To validate this new design, a framework was presented for a cross-assessment of Life Cycle Assessment with Circularity Analysis to compare the new tinplate capsule with conventional polypropylene and aluminium capsules. The novel design is more circular (0.97 in the material circularity indicator), in comparison with the polypropylene (0.1) and aluminium (0.80) conventional capsules, due to the ferromagnetic properties that allow for better effectiveness during sorting in urban packaging recycling facilities. As for the environmental assessment, the tinplate has higher environmental impacts than the aluminium and the polypropylene capsules (more 63 % and more 92 %, respectively) due to the high energy intensity processes required to produce this material. These results demonstrate that the novel tinplate capsule should complement the strong results in circularity with further improvements in its environmental performance, namely by the transition of the steel industry to the upcoming generation of decarbonized steel production.

Experimental investigation of RC beams strengthened with externally bonded BFRP composites

Abstract Objectives The goal of this article is to examine the behavior of reinforced concrete (RC) rays that strengthen superficially the basalt fiber-reinforced polymer (BFRP) fabrics. We found out that one ray without BFRP and seven rays enveloped within numerous lay-up arrangements. The importance of the study is to improve the flexural capacity of rays, using fiber-reinforced polymer procedure and examine the over-reinforcement technique. Methods Interestingly, we have examined under two-point loading, one BFRP fabric sheet flexure. Results Loads corresponding to the first crack/delamination and ultimate failure of the beams have been verified. Moreover, we have recognized the types of failure and load contrasted with deflection graphs that have been strategized at outstanding ray locations. Novelty Our investigation has unraveled the increased flexural strength of the strengthened RC rays after using coating. Additionally, we have applied pressure to the BFRP fabrics on both sides of the beams. Moreover, we have improved performance with flexural strength, ductility, and failure. Our results are novel and show that the flexural capacity of the wrapped RC rays increases by 46.6%. The ductility increased by 84%, and unfortunately, we had failed the FRB and the concrete had crushed.

Multi-objective optimization of composite sandwich structures using Artificial Neural Networks and Genetic Algorithm

Sandwich structures offer significant opportunities to improve the performance of many industrial applications such as aerospace, automotive, and marine. The design of a composite sandwich structure is often challenging because it is driven by the balance between the weight and cost of these structures. In this paper, a multi-objective optimization model using a Genetic Algorithm (GA) and an Artificial Neural Network (ANN) is presented to evaluate a new optimization approach in terms of weight and cost minimization for the composite sandwich structures. Classical lamination and beam bending theories were used, along with Monte Carlo simulation, to generate the design data for the proposed composite sandwich structure, which is applied as a floor panel for a high-speed train. Multilayer feedforward neural networks were used for predicting safety factors, cost, and weight of the designed structure based on the following inputs: core density, core thickness, face sheet materials’ combinations, and applied load. The trained Neural Network model was able to predict the considered results with a good performance metric, namely the coefficient of determination (R2 = 0.99) and the Mean Square Error (MSE = 1.3·10−5).Multi-objective optimization for cost and weight minimization was performed with a Genetic Algorithm using the derived ANN model. The obtained Pareto front provided several non-dominated optimal points leading to insights on the optimization process. The Finite Element Method (FEM) was used to model the key points of the optimal designs (i.e. the design with the lowest cost, weight, and Pareto optimal points). The FEM and optimization results had a maximum deviation of about 8.9%, indicating a good agreement between the two techniques.The newly elaborated methodology demonstrates a new approach for obtaining the optimum design of the investigated composite sandwich structure constructed from honeycomb core and laminated face sheets in terms the cost and weight. The study concluded that the use of Carbon Fiber-Reinforced Plastic (CFRP) or Fiber-Metal Laminate (FML) face sheets results in significant weight savings of about 59.5% and 48.6%, respectively, compared to an all-aluminum sandwich structure.

Flow curve approximation of high-strength aluminium alloys in heat-assisted forming processes

Predicting the flow behaviour at high strain values beyond uniform elongation is a critical factor in sheet metal forming, especially in the context of heat-assisted forming processes of lightweight materials. Based on uniaxial tensile tests conducted at the temperature profiles of the Hotforming, W-Temper, and Warmforming process routes this study presents the determination of the flow curve for EN AW-7021 sheet material using five commonly used empirical approximation models. A support point obtained from layer compression tests was introduced to analyse the accuracy of the extrapolation models at higher strain values. All models considered were found to be in good agreement with the experimental tensile test data in the area of uniform elongation. However, the empirical approximation models show significant differences in strain hardening behaviour when higher strain values and varying temperature profiles are considered. For the Hotforming and W-Temper process routes, the Hockett-Sherby model estimates the flow behaviour with the highest accuracy. When using the Warmforming process, all approximation models considered seem to estimate the flow behaviour with reasonable accuracy, however the Ludwik-Hollomon modified equation shows the best correlation with the experimental data.

Perencanaan Pembelajaran Berbasis Teaching Factory pada Kompetensi Keahlian Teknik Pemesinan di SMK Bhinneka Karya Surakarta

This research aims to describe the teaching factory planning process, the use of the teaching factory application, and its assessment to improve student competency at Bhinneka Karya Surakarta Vocational School. The Teaching Factory planning design was carried out based on the results of observations and analysis at Bhinneka Karya Vocational School, Surakarta. In-depth interview techniques, observation and documentation were used to collect data. Interactive models play a role in analyzing data and procedures starting with data collection, reduction, presentation and verification of conclusions. Research findings show that the implementation of teaching factory-based learning in the context of developing student competency begins with planning, implementation of learning, production/service activities, industrial collaboration, impacts and obstacles faced. In planning the teaching factory, utilizing strategies to realize change, the material in class, titles and job sheets are adjusted to existing standards in the industry, educators adapt the practices carried out by students so that they are equipped to deliver quality material that is driven throughout the day, the talents that they will carry out. Through teaching factories, student competence can be improved with various learning procedures that have been established in the curriculum and implemented for vocational school students.

A novel zero tool defect accelerated friction stir thin sheet welding technique for automotive light-weight structural component fabrication with dissimilar material

Frequent tool failure and rupturing pose significant challenges in friction stir welding (FSW) of thin dissimilar material sheets with diverse thermal and mechanical properties. These issues exacerbate at higher welding speed (ν), demanding greater precision in welding methodology. This paper presents a novel approach to weld 300 μm thin SS304 and 500 μm thick commercially pure aluminum sheets at ν up to 2400 mm/min using H13 tool without wear, obviating the necessity for expensive high-strength tool materials. Furthermore, the use of a pinless tool negates the requirement for an additional pinhole filling step, which is a prevalent challenge associated with pinned tools. The study unveils that higher tool tilt angle (α) reduces flash formation, leading to a higher effective weld thickness, thereby enhancing weld strength. The increased material extraction (2.048 mm3) from the weld center and higher heat generation (7.6%) compared to the pinless tool imposes a speed limit of 300 mm/min for the pinned tool. The thicker layer (4.9 μm) of inter-metallic compounds (IMC) formed at lower ν showed maximum joint strength (70.03% of base Al). The fracture behavior indicates cleavage facet formation becomes more frequent at higher ν, diminishing joint ductility. With a distortion-free, high lap shear strength and enhanced ν, this novel joining method meets the needs of industrial mass production.

A NON-DESTRUCTIVE METHOD FOR EVALUATING THE ADHESION BETWEEN THE LAYERS OF METAL-POLYMER-METAL COMPOSITE MATERIALS

Development of a non-destructive measuring technique for evaluating the bonding quality of metal-polymer-metal composite sheet materials is introduced. Sufficient adhesion is necessary to ensure further shaping steps or bearing loads when used without failure due to delamination. Much attention is paid to determining the quality of gluing. According to the patent-literature review, no non-destructive measuring or quality control of layers’ bonding quality over the entire surface has been found. Thus, a new technical solution is proposed for defining the quality of bonding between the layers by means of electrodynamic repulsion forces arising from the pulse current passing over the metal layers of a composite in the counter direction. The feasibility of the method is tested in laboratory conditions. For its implementation, the necessary values of the test parameters are obtained, i.e., the values of the current transmitted through metal layers. In addition, the possibility of detecting local defects of different shapes and sizes with the proposed method is estimated.

Relation between water absorption and mechanical properties of flax 3D braided yarn woven fabric PLA bio-degradable composites

Natural fibre (flax) plain type of woven fabric is developed by using solid braided yarn and is utilised as filler material and PLA (polylactic acid) as a matrix. Solution casting is then used to create sheets of pure PLA and flax fabric–PLA. Composites are manufactured by sheets sequencing technique using the hot compression moulding method. Water absorption, thickness swelling and flexural tests are performed in loading directions of warp and weft of the composites. Results revealed that the absorption of water and swelling of thickness are enriched with an addition of flax fabric. The weft direction loaded composite displayed greater values of water uptake and thickness swelling. The warp direction loaded composites demonstrated the highest flexural strength (92.3 MPa) and modulus (4.5 GPa) compared to weft direction loaded composites. These values are decreased after water absorption.

Recrystallization of bulk nanostructured magnesium alloy AZ31 after severe plastic deformation: an in situ diffraction study

The magnesium alloy AZ31, which has undergone high-pressure torsion processing, was subjected to in situ annealing microbeam synchrotron high-energy X-ray diffraction and compared to the as-received rolled sheet material that was investigated through in situ neutron diffraction. While the latter only exhibits thermal expansion and minor recovery, the nanostructured specimen displays a complex evolution, including recovery, strong recrystallization, phase transformations, and various regimes of grain growth. Nanometer-scale grain sizes, determined using Williamson–Hall analysis, exhibit seamless growth, aligning with the transition to larger grains, as assessed through the occupancy of single-grain reflections on the diffraction rings. The study uncovers strain anomalies resulting from thermal expansion, segregation of Al atoms, and the kinetics of vacancy creation and annihilation. Notably, a substantial number of excess vacancies were generated through high-pressure torsion and maintained for driving the recrystallization and forming highly activated volumes for diffusion and phase precipitation during heating. The unsystematic scatter observed in the Williamson–Hall plot indicates high dislocation densities following severe plastic deformation, which significantly decrease during recrystallization. Subsequently, dislocations reappear during grain growth, likely in response to torque gradients in larger grains. It is worth noting that the characteristics of unsystematic scatter differ for dislocations created at high and low temperatures, underscoring the strong temperature dependence of slip system activation.Graphical

Effect of process parameters on the synthesis and lead ions removal performance of novel porous hydroxyapatite sheets prepared via non-aqueous precipitation method

Herein, porous hydroxyapatite sheets with high lead ions removal performance are synthesized via self-assembly non-aqueous precipitation method, and the effects of process parameters on the synthesis and lead ions removal performance are systematically investigated. The optimized precursors concentration, the molar ratio of calcium to phosphorus and the calcination temperature are 0.25 mol/L, 1.67 and 650 °C, respectively. The refinement XRD, FE-SEM and EDS tests of the optimized samples show that the samples have a porous sheet structure with uniform pore size and wall thickness. The lead ions removal rate of hydroxyapatite sheets has the maximum value of 99.6% when the hydroxyapatite addition amount is 1 g/L. The lead ions removal content is the maximum of 1303.6 mg/g when the initial lead ions concentration is 9 mmol/L. The removal mechanism of lead ions by porous hydroxyapatite sheets prepared in this work is the composite mechanisms of surface adsorption, surface complexation and ions exchange. The hydroxyapatite porous sheet material prepared by optimizing the process parameters in this study has the advantages of high removal capacity and wide adaptability, so it is expected to become a novel adsorbent to solve lead-containing wastewater.

An alternative and robust formulation of the fatigue crack growth rate curve for long cracks

Crack growth simulations are an important method for estimating the remaining service life of components and structures with cracks under cyclic loading. In particular, the evaluation of cracks emanating from clinched joints is a major challenge because the fracture mechanical properties of the sheet materials can change locally due to the joining process. Special specimens are used to determine the relevant crack growth rate curves. For the application of these curves within simulation programs, they are described using crack propagation equations. This requires an accurate formulaic description of the entire crack curve with clearly identifiable parameters that unambiguously describe certain characteristics of the crack growth rate curve. Known approaches either describe only parts of the crack growth rate curve or the single parameters affect different characteristics of the curve and thus influence each other. Therefore, a new alternative and robust mathematical fit of the crack growth rate curve is developed and validated with experimental results.

Shock absorption and dispersion capability of a novel five-layer mouthguard sheet material.

There is a growing need for a mouthguard sheet material with higher shock absorption and dispersion capacity than those obtained by conventional materials. A five-layer mouthguard sheet material was previously developed using laminated ethylene vinyl acetate and polyolefin copolymer resin. In this study, the shock absorption capacity and dispersion capability of the new sheet material were investigated and compared with those of other materials. Impact testing for the new sheet material showed that the force required to displace the sheet by 1 mm was significantly higher at all thicknesses (p<0.001), whereas the puncture energy and displacement were significantly lower than those for ethylene vinyl acetate (p<0.05). The five-layer mouthguard sheet material successfully absorbed and resisted shock. Therefore, the sheet material potentially increases resistance to applied deformation in teeth and alveolar bone and maintains structure. The five-layer sheet material could expand the range of mouthguard products and help prevent oral trauma.

Привод подачи режущего инструмента фрезерного станка для обработки вафельного фона

The paper describes the process of designing the cutting tool feed drive of a special metalworking machine, which due to the circuit solution and automatic control system will increase the productivity of processing one cell of wafer background on sheet material up to 10–15 seconds. On the basis of the analysis of the technology of milling of a given regular pattern of wafer background and peculiarities of the equipment operation it proposed to replace the traditional ball bearing gear in the cutting tool feed drive with a flat combined crank-slide mechanism. Geometrical parameters of the lever transmission mechanism calculated in accordance with the known dimensions of the regular cell pattern and the recommended value of the angle of motion transmission. The analysis of kinematic and power characteristics of the lever mechanism allowed to justify the technical characteristics of the electric motor. In order to realize the required trapezoidal law of the output link speed change, the inverse problem of kinematics solved, numerical values of the instantaneous angular velocity of the input crank and pulse control signals to the servomotor obtained.

Formation of reflective shells by electric arc spraying and application of composite material to the punch

In the course of the work, the process of forming reflective shells and finding the position of grid elements after deformation was investigated. Fixation of mesh nodes by electric arc spraying. After that, a composite material such as polystyrene is applied to form reflective shells. Minimization of potential energy is carried out numerically by an iterative method. The result of the work is the formation of the antenna array shell by the method of electric arc spraying and the application of the composite material. The following forming operations of sheet metal stamping are known: drawing, rotary drawing, relief forming, trimming, including rubber and liquid drawing, hydromechanical drawing, explosion drawing, electric discharge stamping, electromagnetic stamping, hydropneumatic drawing, which allow to obtain a shell from sheet material (solid or gas and water permeable) by pressing it against a die or punch with a transfer medium.

ПРЕОБРАЗОВАНИЕ СХЕМЫ ФОРМООБРАЗОВАНИЯ ОБТЯЖКОЙ НА ПРИНЦИПАХ СИММЕТРИИ

We assume that the concept of symmetry plays an important role in improving the theory and practice of the forming process by covering load-bearing thin-sheet shells of double curvature, which guarantees the production of contour-forming parts of the skin of modern aircraft with an exact geometric shape and minimal variation in thickness. To understand our assumption, it is necessary to remember that the complexity of the theory of plastic shells lies in the geometric and physical nonlinearity and the need to take into account shear stresses and deformations along the surface of the shell and its variability in curvature, therefore there is still no unified approach to the analysis of the formative processes of covering from sheet material. This assumption applies only to thin-sheet shells of double curvature, providing a different isometric position (curved surfaces one on top of the other) of the open surface as a whole, and not closed like a sphere. Therefore, the process of shaping a sheet blank into a shell part of an aircraft has some form of symmetry with respect to a given set of surface transformations, unless certain properties or relationships, the so-called invariants of the set of transformations, change when they are performed.

Bio-leather: Sustainable clothing fabrics made from simple media ingredients and slime mold Physarum polycephalum

The textile industry contributes significantly to global warming and pollution, especially the leather industry, which uses livestock and toxic tanning processes that have a great environmental impact. Currently, efforts are being made to mitigate the negative impacts of the textile industry by using alternative non-toxic chemicals or by recycling fabric. More recent efforts explore utilization of non-conventional biomaterials and organisms, such as mushroom mycelia, algae or genetically-engineered microorganisms. In this study, we implemented slime mold Physarum polycephalum perfused through leather-like fabrics made from air-dried simple nutritious media in order to develop environmentally friendly, easy-to-manufacture and sustainable fabrics. Plasmodium was validated for its viability and propagation under non-sterile conditions and in contaminated environments on different media compositions made from agar, peach gum, gelatin, carrageenan or glycerol. We determined optimal media components to be agar, gelatin and glycerol which supported plasmodium growth and yielded sturdy and flexible fabric sheets after air-drying. Ultimately, plasmodium-perfused fabric sheets were sewed into apparel and footwear. This study demonstrates the use of simple media as a clothing fabric perfused with plasmodium, which produces intricate colors and patterns on the fabric. Plasmodium has the ability to enhance fabric properties due to its natural problem-solving abilities, such as biosensing, fabric self-repair, and distant fabric communication.