Low Specific Weight Research Articles

Evaluation of the effect of casting die vibration on the microstructure and mechanical proprties of aluminum alloys : review

Aluminium alloy is one of the most widely used engineering materials due to its properties Relatively lower specific weight and corrosion resistance compared to steel. Moreover, they are They are also relatively easier to machine. Aluminium alloy is found to provide the highest quality Degree of machinability compared to other lightweight metals such as titanium and magnesium Alloy. Various techniques have been used to induce motion during the solidification process of molten metal in the casting mold, such as mechanical vibration, ultrasonic vibration, and electromagnetic vibration. This paper presents a brief review of the above vibration processes and their types, uses, and how they affect the mechanical properties of aluminium alloys

Investigation of the Mechanical Properties of Hybrid E-Glass and Mohair Fiber Reinforced Epoxy Composites

Natural fiber composites have significant potential to replace traditional materials used in industries due to their excellent tensile strength, stiffness, low specific weight, and superior thermal and insulating properties. Mohair fiber, also known as the Noble fiber and the Diamond fiber, is obtained from the Angora goat, an animal of Tibetan origin. Renowned for its brilliant luster and resilience, Mohair is a symbol of luxury and exclusivity. The primary objective of this study is to manufacture and test a new natural fiber composite that could potentially outperform existing materials in real-world applications. Specifically, the study aims to investigate the mechanical properties of this composite. Mohair has previously been identified as a fiber many times stronger than a strand of steel of similar dimensions. Incorporating these highly desirable properties of Mohair into an epoxy matrix is one of the novel aspects of this research. The testing procedure begins with the preparation of ASTM molds, concurrent treatment of the fibers, and the preparation of the binding material. Specimens are created both with and without the addition of electrical glass (E- glass) fibers. The next phase is curing, during which the epoxy is allowed to solidify, forming strong bonds. Once developed and cured, the composites are removed from their molds and undergo post-processing and finishing techniques. This study aims to understand the tensile and flexural characteristics of natural fiber composites reinforced with epoxy. Three fiber orientations—uniaxial, biaxial, and criss-cross—are employed to assess the changes in the mechanical properties of the composites. The results indicate that adding E-glass fibers in alternating layers of the composite significantly enhances both tensile and flexural strength. Statistically, the addition of the biaxial arrangement of fibers with E-glass fibers results in an 18.47% improvement in ultimate tensile strength, while the maximum flexural strength increases by 49.90%. Furthermore, the topography of the cracked surface is examined using field emission scanning electron microscopy, and the breaking of the fibers in all three directions is studied.

Key Aspects of the Integration of the Donetsk People’s Republic into the Economic Space of the Russian Federation

The article considers the problems of integration of the new region - Donetsk People’s Republic into the economic field of the Russian Federation. The main tasks to be solved in the liberated territories are given. It is suggested to form a state programme aimed at solving these problems. It is revealed that one of the key problems limiting further economic growth, along with the ongoing military operations, is the outflow of able-bodied population. As a strategic goal of socio-economic development of the Republic for the next 10 years, it is proposed to restore infrastructure, modernize industry and structural reform of the economy, increase the population, as well as the quality and duration of life. To achieve this goal, three directions are considered: formation and accumulation of human capital; creation of space for human capital development; creation of appropriate economic environment. The stages for the realization of goals and tasks have been identified. It has been determined that industry should form the basis of the economy of the reviving Donbas. It is necessary to develop manufacturing industries, knowledgeintensive and complex production. It is of fundamental importance to improve the quality of economic growth - to build and move along the supply and value chains from the first links, with a low specific weight of added value in the price of goods, to the next links, with a higher specific weight of added value. Priority sectors of the Republic are identified. It was noted that the activation of economic development cannot be carried out without reforming the existing system of state administration in the Republic. An important task is to transfer the functioning of public authorities to the technology of strategic and programme-target planning and budgeting.

A qualitative dynamic analysis of the relationship between tourism and human development

This study analyzes the dynamic relationship between tourism and human development in a sample of 123 countries between 1995–2019 using a symbolic time series methodological analysis, with the number of international tourist arrivals per capita as the tourism measurement variable and the Human Development Index as the development measurement variable. The objective was to determine if a higher level of tourism specialization is related to a higher level of economic development. The definition of economic regime is used and the concept of the distance between the dynamic trajectories of the different countries analyzed is introduced to create a minimum spanning tree. In this way, groups of countries are identified that display similar behavior in terms of tourism specialization and levels of human development. The results suggest that countries with a high level of tourism specialization have a higher level of development as compared to those in which tourism has a lower specific weight. However, the largest group of countries identified is characterized by low levels of tourism specialization and economic development, which appears to translate into a poverty trap. Therefore, policies related to tourism activity expansion should be created since higher tourism levels have been linked to higher levels of human development. In the case of less developed countries, however, these projects should be financed by international organizations so that these countries can escape the poverty trap in which they are currently found.

Reprocessable carbon fiber vitrimer composites: Reclamation and reformatting of carbon fibers for second generation composite materials

AbstractCarbon fibers (CFs) are experiencing a growing demand owing to their low specific weight, exceptional mechanical properties, superior temperature, and corrosion resistance, however, their sustainability and energy consumption during manufacturing is still a challenge. Therefore, reclamation of waste CFs and their reformatting has gained significant attention. Herein, we synthesized a chemically degradable vitrimer matrix by curing bisphenol‐A diglycidyl ether (BADGE) with 2‐aminophenyl disulfide (2‐AFD) and further utilized the matrix for the development of CF reinforced composites (CFRCs) through vacuum‐assisted resin infusion molding (VARIM) process. The obtained vitrimeric system and its composites show excellent mechanical, self‐adhering, shape‐memory, and reprocessing properties. Meanwhile, the developed CFRP vitrimer composites can be rapidly dissolved in thiol solvent (1‐octanethiol), resulting in the efficient recycling of CFs. X‐ray diffraction, scanning electron microscopy, and Raman spectroscopy validate that the chemical structure of the recycled fibers closely resembles the structure of the original CFs. The recycled CFs were further used to prepare second generation composite materials with excellent thermal, dynamic, and mechanical properties for nonstructural applications (e.g., sports, automotive, etc.). Thus, with an effective CF recycling method, this study can assist in preparing reliable, long‐term functional, recyclable, and high‐performance composites.

An inspection of the metal-foam beam considering torsional dynamic responses

Metal foam is a multifunctional material with a lower specific weight, high stiffness and compressive strength, and high energy absorption. These remarkable properties make metal foams a promising candidate for conventional materials in different industrial fields. Despite numerous researches on mechanical behavior either static or dynamic of structures made of metal foams, torsional vibration analysis of metal foam structures is still uninvestigated. In this investigation, the influence of various imperfection distribution patterns on the torsional dynamic response of metal foam beams is examined within the framework of Timoshenko-Gere's theory. Two common materials i.e. SUS304 and Aluminum foams are considered the constructive materials of structure. Moreover, three imperfection distribution patterns are taken into account. The virtual work's principle has been employed to derive the torsional governing equation of metal foam beams. Then, the derived governing equation has been solved via an analytical method. The accuracy of the employed methodology has been compared with the findings of former research in the literature. Finally, the influences of different notable parameters on the variation of natural torsional frequency have been examined and demonstrated in a group of tables and diagrams.

Influence of spatial engagement angles on machining forces and surface roughness in turning of unidirectional CFRP

Carbon fibre-reinforced polymer (CFRP) is being widely used due to its low specific weight and outstanding mechanical properties. However, using identical machining parameters on unidirectional CFRP can lead to different results depending on the fibre orientation.Recently, a process-independent model describing the engagement conditions in oblique cutting of unidirectional CFRP has been developed, introducing the spatial angles θ0 and φ0. Since the engagement conditions of milling and drilling are complex, analogy experiments are conducted in turning with variation of the setting κrand inclination angles λs. In this study, process forces and surface roughness were measured as a function of the complete range of fibre cutting angle θ.

Selected Aspects of Sustainable Construction—Contemporary Opportunities for the Use of Timber in High and High-Rise Buildings

Due to the favourable pro-environmental properties of timber, including the origin of the raw material from renewable sources, ease of reuse, negative carbon footprint, low specific weight, possibility of prefabrication, etc., there is increasing interest in the use of timber in construction. This paper takes a closer look at the new uses of timber as a load-bearing structure for high and high-rise buildings. Cases described in the literature concerning this type of building with residential and public functions erected worldwide were analysed. The first buildings of this type were put into use in 2009. The aim of this paper is to show new possibilities and to extend the use of timber as a load-bearing structure of high and high-rise buildings previously made of reinforced concrete or steel. The scope of the analysis includes two postulates of sustainable construction, directly related to the above-mentioned goals: limiting interference in the natural areas of cities through efficient use of building plots for high or high-rise buildings and the use of renewable materials—timber—for the load-bearing structure of buildings. A research method based on a case study was used. Conclusions were made on the pro-environmental spatial–functional and material–structural design of these high and high-rise buildings.

Additive Manufacturing of TiC/Steel Composites Using Electron Beam Melting and In Situ Infiltration

Cemented carbides containing titanium carbide (TiC), characterized by low specific weight, superior hardness, and excellent high‐temperature resistance, are widely used as wear‐resistant cutting tools and brake discs. Instead of using conventional powder metallurgical approaches, composites comprising TiC and stainless steel are fabricated in this study by means of an innovative method combining electron beam powder bed fusion (PBF‐EB) and in situ liquid metal infiltration. For PBF‐EB, a pure TiC powder as feedstock and a stainless steel plate as substrate are used, respectively. Owing to the high processing temperature in the hatching area, the TiC particles are inhomogeneously sintered. Simultaneously, an in situ infiltration of liquid steel into the pores between TiC particles takes place during PBF‐EB, forming a dense and crack‐free composite material containing ≈68% TiC. The electrical properties of the raw TiC powder are investigated at different temperatures to optimize the process parameters ensuring high process stability during PBF‐EB. The microstructure and mechanical properties (compression strength, hardness, and fracture toughness) of the PBF‐EB‐produced TiC/steel composite are analyzed.

ИССЛЕДОВАНИЕ ДИНАМИЧЕСКИХ СВОЙСТВ ГИБРИДНОГО ТИТАН-ПОЛИМЕРНОГО КОМПОЗИЦИОННОГО МАТЕРИАЛА

Low specific weight and high mechanical strength (especially at elevated temperatures) of titanium and its alloys make them very valuable aviation materials. In the field of aircraft construction and aircraft engine production, titanium is increasingly replacing aluminum and stainless steel. At present, aircraft developers are restructuring the whole material science concept of aircraft construction, actively involving and using various types of composite materials based on titanium alloys. Combined with the properties of titanium, FML composites based on titanium have greater stiffness, impact resistance, heat resistance, and corrosion resistance especially compared to similar aluminum-based materials. The paper investigates the dynamic characteristics of hybrid titanium-polymer composite materials (TPCM) based on titanium alloy BT-23 and fiberglass with a brief presentation of the main characteristics of prepregs. The process of manufacturing specimens for testing including heat treatment, ply laying scheme and reinforcement scheme in two variants is described. The results of experimental studies of natural frequencies and damping coefficient by the method of free damped oscillations in free oscillations of TPCM plates are presented. The tests are carried out on a specially designed unit with a triangulation sensor in the variant of vertical loading. Two identical specimens with different overall dimensions are tested.Each specimen was tested with a different amplitude. Five tests were conducted for each amplitude. The physical constants of the specimens were pre-determined in static tests. The natural frequencies and damping coefficients for the titanium-polymer composite specimens were found.

How to Easily Make Self-Sensing Pneumatic Inverse Artificial Muscles.

Wearable mechatronics for powered orthoses, exoskeletons and prostheses require improved soft actuation systems acting as 'artificial muscles' that are capable of large strains, high stresses, fast response and self-sensing and that show electrically safe operation, low specific weight and large compliance. Among the diversity of soft actuation technologies under investigation, pneumatic devices have been the focus, during the last couple of decades, of renewed interest as an intrinsically soft artificial muscle technology, due to technological advances stimulated by applications in soft robotics. As of today, quite a few solutions are available to endow a pneumatic soft device with linear actuation and self-sensing ability, while also easily achieving these features with off-the-shelf materials and low-cost fabrication processes. Here, we describe a simple process to make self-sensing pneumatic actuators, which may be used as 'inverse artificial muscles', as, upon pressurisation, they elongate instead of contracting. They are made of an elastomeric tube surrounded by a plastic coil, which constrains radial expansions. As a novelty relative to the state of the art, the self-sensing ability was obtained with a piezoresistive stretch sensor shaped as a conductive elastomeric body along the tube's central axis. Moreover, we detail, also by means of video clips, a step-by-step manufacturing process, which uses off-the-shelf materials and simple procedures, so as to facilitate reproducibility.

Evaluation of a Local Acoustic Resonance Method for Coating Thickness Determination on Stochastic Metal Hybrid Foams

Novel cellular materials promise a combination of high strength and low specific weight for sustainable and energy‐efficient material design. Inhomogeneities of the materials, such as varying coating thickness, are inherent to the production process but require advanced characterization in order to better understand mechanical properties. Herein, global and local acoustic analysis for nondestructive characterization of local coating thickness on an open‐porous hybrid metal foam system is studied. Experiments and numerical simulations are carried out to evaluate vibration behavior stimulated by a low‐energy impact. The novelty of the work is the use of local excitation and analysis of decay times to determine coating thickness gradients. This qualitative measurement can inform and speed up the material development process due to its simplicity, speed, and low cost. Furthermore, it provides a basis for quality control when scaling up the technology of metal hybrid foams for industrial applications.

Process parameters for three-dimensional specimens made of Ti6Al4V materials using additive manufacturing: A review

The Ti6Al4V alloy is highly mechanical, corrosion-resistant, low-specific weight, and biocompatible. Several high-performance applications are ideal for technical uses in the auto, aerospace, and medical sectors. The recent process parameters for Ti6Al4V, manufactured using additive manufacturing methods, are reviewed in this article for the past 20 years. It is possible to link processing parameters with fundamental information. This review finds that the process parameters in additive manufacturing are laser power, scanning speed, layer thickness, and hatch distance. In addition, this reviewed the presence of processes in the additive manufacturing of Ti6Al4V components and their impact on mechanical performance and microstructure analysis. In the additive manufacturing process, the reviewed parameter is the additive manufacturing component that has reduced the defects of microstructural evaluation, residual stress, porosity, compression, and corrosion behaviour of the study.

GFRP reinforced concrete curb: design, economic and regulatory considerations

This paper discusses the use of GFRP reinforcement application for concrete curb design and bridge barrier replacement projects. Unlike conventional steel bars, Glass Fiber Reinforced Polymer rebars have the considerable advantage of not being susceptible to corrosion, preserving the durability of the structures and reducing the maintenance costs during the service life of the bridge. An additional advantage is the low specific weight of the GFRP, which makes it possible to speed up the installation of the reinforcements on site, ensuring greater safety for operators. The paper compares, in terms of structural performance and overall costs, two curbs of the same geometry, one reinforced with classic steel bars, the other with GFRP bars, providing evidence that current code provisions can be practically implemented in typical design situations.

Finite element analysis of laminated composite stiffened hyperbolic paraboloid hypershell subjected to impact loading

Laminated composite has produced a solution in the weight sensitive branches of engineering due to its low specific weight, high specific strength and weathering resistance. It is its low transverse shear capacity under impact load has become a great concern for the researchers for its successful implementation in different industrial sectors. Impact which is likely to occur in cyclone prone zones and aircraft bases where wind borne debris causes the same. The sudden strike may cause delamination, crack in the epoxy medium or tearing of fibers which remains suppressed under the lamina and eventually causes collapse. This study is an effort to analyze the laminated composite hyparshell under impact load with simply-supported boundary conditions. Installation of stiffeners in various positions become unavoidable in certain cases and which is optimized and the best possible combination is concluded. A detailed comparative study of deformation, stress and strain is done with respect to various impactor velocities. The analysis is done by finite element software Ansys 2022 R1.

Fire resistance of gypsum drywall partitions with polyurethane foam filling

AbstractGypsum drywall systems have gained their popularity, among other reasons, due to the excellent fire‐resistant properties. The use of different variants of the structures filled with insulating material (most often mineral wool) makes it possible to shape the parameters of fire resistance according to the requirements. The use of polyurethane foam for filling spaces inside drywall systems has become increasingly popular. This is especially applicable to the performance of thermal insulation of wooden roof slopes. The advantages of polyurethane foams over mineral wool include good adhesion to the substrate, lower specific weight, lower thermal conductivity and shorter time to make a tight filling layer. Its undoubted disadvantage is lower fire resistance. The paper presents a research on the fire resistance of gypsum drywall systems with self‐extinguishing polyurethane foam filling. The fire resistance time of the structures was measured in accordance with EN1363‐1 using a standard temperature‐time curve. The tests simulated a fire on the outside of a service shaft with a layer of polyurethane foam on its interior side, and a fire in an attic room with self‐extinguishing polyurethane foam thermal insulation between wooden rafters, and an interior enclosure made of two layers of gypsum board on a steel frame. The tests made it possible to determine the times of meeting the fire resistance criteria of partitions with polyurethane filling.

Investigation of the Microstructure of Porous Tube-Shaped Elements Made of Ti-Powder Materials

The method of powder metallurgy for the manufacture of titanium products has the advantages of low cost of raw titanium, short technological process, low energy consumption, and less equipment investments. This allows to significantly reduce the total costs. The method is a potential technology to manufacture inexpensive products from titanium alloys. Due to its high strength, low specific weight and high corrosion resistance, titanium is widely used in aerospace and automotive industries and biomedicine. Among various applications of titanium, tube- and disc-shaped products from titanium powder are essential. The paper presents the results on the investigation of products made of titanium powder by the method of magneto-pulse pressing. Titanium powders with a particle size of 160-1000 mm produced by grinding titanium sponge and its powder compositions were used in the investigation. Investigation results on microstructure and porosity are also discussed. The mean porosity of the samples after sintering was 25-28% for products of 4-6 mm thick. With increasing thickness, the porosity increases to 35% and more, while it was non-uniform both over the cross-section of a tube-shaped product and along its length. The outer surface of the product was found to have a looser microstructure. This can be explained by the application of an intermediate fusible layer to the inner wall of the shell, which makes easier the removal of the shall after pressing. The studies generally confirm the possibility tof using the magneto-pulse pressing of titanium powders in shells to manufacturesmall product batches.

A review of the evolution of research on proposals for bamboo culms connections in structural systems

Structural systems built from raw bamboo have been used for years due to its highly renewable characteristics, versatility, and abundance in various countries, e.g., China, Indonesia, all over South America, and especially Brazil. It is also considered a low specific weight material, which means it is easy to handle and transport. These characteristics make it a low-cost material for building construction. The objective of this systematic bibliometric review is to identify innovations in bamboo culms structural connections in order to contribute to the advancement of technology applied to civil construction by seeking joints that consider the use of industrialized or standardized products. This review revealed there is still no ideal connection capable of solving the great problem of this subject, which points out the need for more studies on the topic. This investigation also allows for the classification of the connections into 5 categories: Bolted connections; Steel member and Steel plate connections; Reinforced Connections with filler; Parameterized connections, and; Connections with the use of wooden dowels.

Modification of the structure and properties of oxide layers on aluminium alloys: A review

Abstract Aluminium alloys are a material that is increasingly used in industry. This is due to very good strength properties with low specific weight and low production costs. The disadvantage of kinematic system aluminium elements is their surface’s susceptibility to adhesive wear. One method of eliminating the adverse impact of adhesive tacks on the surfaces of cooperating aluminium components of machinery is the application of the method based on the anodic oxidation of alloys surface. The layers obtained by this method are widely used in sliding connections of kinematic machine parts. The modification of anodic oxide layers with admixtures has been an uninterrupted area of interest since the 1990s. This article is a review of selected methods of modifying the structure and properties of aluminium oxide layers on aluminium alloys.

Grading bamboo through four-point bending tests. A report on six species of Italian bamboo

The adoption of natural construction materials can help mitigate the environmental impact of the construction industry by reducing the amount of energy required and emissions. Among the natural materials, bamboo is a remarkable option, combining high mechanical resistance with a low specific weight and a very high growth speed; however, its application is limited by the absence of a suitable grading method. This paper aims at filling this lack by providing a strength-based grading methodology relying on a four-point bending test. Experimental results were processed considering bamboo both as a homogeneous material and as a non-homogeneous material and using the ANOVA test. Results show that statistical groups can be defined which are not based on the bamboo species, but on the values of the mechanical properties, hence supporting the appropriateness of strength classes. The bending tests used in this paper could be a crucial test for bamboo grading: it is easier to perform than a tensile test and it gives complete information on the change of material properties along the culm wall thickness. The study focuses on six different species of bamboo grown in Italy, for which little data is present in the literature.