Volume Of Material Research Articles

Enhancement layout optimisation of grid structures with stability constraints

Grid structures have found widespread use in civil and mechanical engineering owing to their ability of covering long spans with an outstanding strength-to-weight ratio. However, their shallow structural depth and slender members make them susceptible to buckling failures. Therefore, it is crucial to enhance the stability of grid structures. An under-explored way to achieve this is by optimally configuring enhancement materials. This paper addresses the challenges of identifying the optimal enhancement layouts for grid structures by solving a density-based topology optimisation problem. The problem formulation is based on the SIMP approach, minimising compliance while satisfying constraints on material volume and structural stability. The stability constraint is expressed using buckling load factors obtained from a linear eigenvalue analysis. Two types of enhancement schemes, involving in-plane and out-of-plane elements, are developed for the single-layer base grid structures. The efficiency of the proposed method is evaluated by performing enhancement layout optimisation for a flat and three curved square grid structures, subject to a uniformly distributed vertical load and a half-span load. The optimisation results shed light on the impact of in-plane and out-of-plane enhancements on the stability of grid structures, providing insights on optimally configuring enhancement materials to achieve desired stability. In addition, comparative analysis between the case studies indicates that for curved structures, a higher curvature normally leads to greater achievable stability. In contrast, the flat grid structure exhibits the broadest range of customisable stability due to its primarily bending-dominant load-carrying mechanism. Furthermore, the outcomes of geometric non-linear analysis confirm the load-carrying capacity of the optimal structures, with non-linear critical loads typically showing a positive correlation with linear buckling loads.

Modelling the influence of tool wear on shape errors in milling using a hybrid soft-sensor

AbstractThe wear of cutting tools during milling processes not only constrains the volume of material that can be removed by a tool but also results in a progressive deterioration of the quality of the workpiece. Although there are established methodologies for predicting tool wear, there is a paucity of knowledge regarding the impact of tool wear on shape error. The authors present a data-driven soft sensor to model the effect of tool wear on shape error, obviating the need for direct tool wear measurement. To evaluate this approach, a milling experiment was conducted, wherein process forces, spindle current, and resulting shape error were measured. Furthermore, a geometrical cutting simulation was conducted in order to obtain cutting conditions, including the volume of material removed. This study examines the contribution of these features to the prediction performance of the proposed soft sensor. Additionally, the transferability from models trained on different tools is investigated to ascertain the impact of tool wear variance on prediction performance. Prediction experiments demonstrate that a soft-sensor based on a combination of simulation and process monitoring data enables a model trained on data from multiple milling tools to account for wear and predict shape error well under varying wear scenarios. The approach presented here has been demonstrated to result in a reduction of the prediction error of up to 60% compared to an average baseline prediction.

Poisson's Ratio Prediction of Injection Molded Thermoplastics Using Differential Scanning Calorimetry.

In the development of thermoplastic products, it is necessary to conduct the necessary mechanical tests and evaluate the reliability of thermoplastics in each case, because the mechanical properties of the same material vary depending on the molding process conditions and product shape. In order to build a sustainable society, it is expected that the evaluation of the mechanical properties of thermoplastics, which are resource and energy saving, will be required. In this paper, the glass transition temperature and melting point of injection-molded thermoplastics were evaluated by differential scanning calorimetry, and the correlation between Poisson's ratio and free volume was obtained by applying the theory proposed by Flory et al. A certain correlation was found between the Poisson's ratio of polymers and the change in free volume determined by the glass transition temperature. It is also clear that this relationship can be approximated by orders of magnitude. The Poisson's ratio of the core layer tended to be smaller than that of the skin layer. It has also been found that there is a negative correlation between the Young's modulus and the free volume of the polymer material.

FRESHMAN SYNDROME IN MEDICAL UNIVERSITIES: ADAPTATION AND PSYCHOLOGY

The article aims to explore the essence of the freshman syndrome in medical universities, to consider the psychological aspects influencing it, and to propose practical approaches to overcoming this phenomenon. The freshman syndrome in medical universities arises from a combination of factors, such as unusual workload, knowledge and skill requirements, a new social environment, and separation from home. This syndrome can cause stress, anxiety, information overload, and fatigue. Students starting their journey in medical universities face a high level of academic demands and a large volume of material they need to master. This situation often leads to stress and anxiety as students need to adapt to a new pace of learning and choose effective learning methods. Additionally, the new social environment at the university can evoke feelings of isolation and loneliness, especially among those who are distant from family and old friends. This can lead to anxiety and the emergence of the syndrome of social adaptation. Therefore, the freshman syndrome in medical universities can be a complex challenge for students and requires support and adaptation strategies to overcome these problems. The article discusses the psychological aspects of the freshman syndrome and the impact of stress on students of medical universities. It explores how students perceive this syndrome, how to cope with stress, and what practical approaches can help facilitate adaptation.

Influence of the friction and wear performance of TiB2/7075 aluminum-based composite materials prepared by friction stir processing

Aluminum-based composite layers with different TiB2 contents were prepared by implanting TiB2 reinforcement powders with mass fractions of 1%, 3%, 5%, and 7% into 7075 aluminum alloy sheets using Friction Stir Processing (FSP) technique. The influence of TiB2 content on the friction and wear performance of the modified aluminum-based composite layers was investigated. The results showed that the incorporation of TiB2 reinforcement powders can reduce the friction coefficient and wear volume of the materials, thereby improving the friction and wear performance. Moreover, as the mass fraction of TiB2 reinforcement powder increases, the overall friction coefficient and wear volume of the composite materials exhibit a gradual decrease trend, with adhesive wear being the predominant wear mechanism.

Dynamic loading platforms coupled to ultra-high speed X-ray imaging at beamline ID19 of the European Synchrotron ESRF

ABSTRACT The intersection of dynamic compression, high-rate material response and X-ray science has seen rapid growth, leading to the establishment of specialized end-stations at international facilities such as Linac Coherent Light Source LCLS (Matter at Extreme Conditions – MEC) and Advanced Photon Source APS (Dynamic Compression Sector – DCS), both USA. Although these facilities excel in working with X-rays tailored for small material volumes (i.e. < 1 mm 3 ), it needs a different approach to delve into subsequent processes. This is particularly the case in the transition from the micro- to mesoscale: here the ESRF distinguishes itself. The large beam size (several cm2) of the ID19 beamline, in conjunction with a strong high energy component, source flux density, and outstanding imaging sensitivity, enables sub-surface visualization of engineering-scale structures as well as natural systems in representative volume, under high rate and shock. This is particularly valuable when studying materials with complex mesostructures and heterogeneities on relevant volumetric scales, which often dominate the dynamic material response. The study of the behavior of materials under dynamic loading presents a unique challenge due to inherently spanning over multiple lengths- and timescales. The evolution of sudden (thermo)mechanical excitation, starting from the lattice scale and progressing through grains, phase domains, and ultimately to structures, exhibits a spectrum of responses spanning from the microscopic to bulk length scales. Consequently, a diverse range of diagnostics as well as driver instrumentation is required to identify, study, and characterize this material response spectrum. This article shall introduce platforms available at beamline ID19 and underline their potential by selected showcase applications. Community access proposals such as the beamtime Block Allocation Group (BAG) allow for access in a routine manner.

Compressive Strength of Geopolymer Mortar Reinforced with Rice Husk Fibers

Geopolymer concrete has been proposed to minimize carbon dioxide emissions related to the cement production industry. This environmentally friendly material consists of industry waste materials activated chemically by an activation solution. In this study, the geopolymer mortar has been designed with 70% fly ash and 30% metakaolin. Hydroxide sodium in 14 molar concentrations blended with sodium silicate in a 2.5:1 ratio was used as the activation solution. Rice husk fibers were added as reinforcement in (1%, 1.5%, and 2%), and waste paper (paper pulp and paper ash) was added in (1%, 2%, and 5%) by volume of cementitious material. The geopolymer mortar samples underwent a curing process through exposure to a temperature of 60°C in an oven for 24 hours. The findings indicate that the samples reinforced with 2% rice husk fibers exhibited the most significant improvement in compressive strength, with 59% and 55% increases after 7 and 28 days of curing, respectively. In general, using waste paper and rice husk fibers significantly enhanced the compressive strength of geopolymer mortar.

Comparative study on manufacturing of EDM electrodes by laser sintering process

The abstract aims to investigate the comparative performance of Electrical Discharge Machining (EDM) and Selective Laser Sintering (SLS) with unconventional machining processes. Unconventional machining processes have gained significant attention due to their versatility and capability to fabricate intricate components with high precision. This study focuses on assessing the efficacy of EDM and SLS techniques in terms of data removal rate and relative wear volume. Electrical Discharge Machining (EDM) is a thermal erosion process that utilizes electrical discharges to remove material from a workpiece. In contrast, Selective Laser Sintering (SLS) is an additive manufacturing technique that employs a laser to selectively fuse powdered material, layer by layer, to build up a three-dimensional object. Both methods offer unique advantages in terms of precision, speed, and material compatibility. The performance evaluation of these techniques involves analyzing key parameters such as data removal rate, which measures the volume of material removed per unit time, and relative wear volume, which quantifies the wear on the tool or workpiece during the machining process. By comparing these metrics, insights into the efficiency and effectiveness of EDM and SLS can be gained, aiding manufacturers and researchers in selecting the most suitable method for specific applications. Through experimental investigations and data analysis, this study aims to provide valuable insights into the capabilities and limitations of EDM and SLS in unconventional machining processes. The findings will contribute to advancing the understanding of these techniques and optimizing their utilization in various industrial sectors, including aerospace, automotive, and biomedical engineering. The experimental analysis examines the impact of the Direct Metal Laser Sintering (DMLS) process parameter on sintering depth. The optimized parameters for AlSi10Mg alloy powder sintering were obtained using laser power at 162 W, scanning speed at 156 mm s−1, porosity at 20%, laser area size of 0.2 mm, and layer thickness of 1 mm.

Modeling Rate Dependent Volume Change in Porous Electrodes in Lithium-Ion Batteries

Automotive manufacturers are working to improve individual cell, module, and overall pack design by increasing the performance, range, and durability, while reducing cost. One key piece to consider during the design process is the active material volume change, its linkage to the particle, electrode, and cell level volume changes, and the interplay with structural components in the rechargeable energy storage system. As the time from initial design to manufacture of electric vehicles decreases, design work needs to move to the virtual domain; therefore, a need for coupled electrochemical-mechanical models that take into account the active material volume change and the rate dependence of this volume change need to be considered. In this study, we illustrated the applicability of a coupled electrochemical-mechanical battery model considering multiple representative particles to capture experimentally measured rate dependent reversible volume change at the cell level through the use of an electrochemical-mechanical battery model that couples the particle, electrode, and cell level volume changes. By employing this coupled approach, the importance of considering multiple active material particle sizes representative of the distribution is demonstrated. The non-uniformity in utilization between two different size particles as well as the significant spatial non-uniformity in the radial direction of the larger particles is the primary driver of the rate dependent characteristics of the volume change at the electrode and cell level.

Design of shaft- and rim-driven contra-rotating reversible pump-turbine to optimize novel low-head pumped hydro energy storages

According to the European-Green-Deal, the share of renewable energy sources (RES) in electricity generation is increased by e.g. solar/wind. This requires the deployment of effective energy storage solutions to compensate the fluctuating network supply of RES. A well-developed storage technology is pumped hydro energy storage (PHES), but especially in lowland countries, e.g. Denmark, typical high-head plant locations are missing. Therefore, new developments in low-head hydraulic turbomachineries and smart operation schemes are needed to shape LH-PHES towards a viable future technology through maximizing performance and minimizing investment costs. Hence, this study demonstrates a novel design of contra-rotating, variable-speed, reversible pump-turbines (CR-VS-RPT) for low-head operation with a peak efficiency above 90 % in pump/turbine mode. The results comparing shaft-driven with rim-driven CR-VS-RPT show the influences of chosen RPT type on the reservoir size/investment. The study also proves that hydraulic losses due to the bulb for shaft-driven CR-VS-RPT have a decisive impact on the head range, and thus on the required dam material volume. Despite the slightly less efficient performance of rim-driven CR-VS-RPT, the absence of the bulb increases the efficiency during operation at low LATs. However, the LAT is the key factor for CR-VS-RPT type selection to minimize the investment for LH-PHES.

Dualistic effect of the deformation of protective structures made of broken rock in mine workings under static load

Purpose is to reveal physical essence of the dualistic (double) nature of deformation effects and their influence on the mechanical properties of protective structures made of broken rock while unloading coal-bearing mass to ensure stability of side rocks and operational conditions of the development mine working within the working areas of coal mines. Methods. The deformation properties of protective structures made of broken rock was modeled on experimental samples during their static load in terms of uniaxial compression with the possibility of lateral expansion of the original material or its compressive stress. Findings. A dualistic effect of deformations for the conditions of uniaxial compression of protective structures was revealed. Under the effect, a complex transformation of volume and shape occurs in the structures caused by the process of relative changes in the backfill material volume. The observed phenomenon occurs within the range of 0.12 ≤δV ≤ 0.32 and the values of the compaction coefficient of broken rock being 1.13≤k con. ≤ 1.47, depending on the granulometric composition of the source material and its bulk density. It was established that under conditions when broken rock is compressed, there is an effect of forming the bearing capacity of protective structures, which is observed when a relative change in the volume of backfill material is 0.14 ≤ δV ≤ 0.38, and its compaction factor reaches 1.16 ≤ kcon. ≤ 1.59. Depending on the homogeneity degree of the backfill material of protective structures, when comparing the values of kcon., a dualistic (double) effect is manifested in the difference of deformation characteristics of broken rock under uniaxial and compressive stress, reaching two or more times. Originality. A regularity was established that determines the relationship between compaction factor kcon. of broken rock and a relative change in the volume (δV) of backfill material, which makes it possible to evaluate bearing capacity of protective structures, being under static load in a stress-strain state. Practical implications. The research results can be used to substantiate the selection of a method to protect development mine working with flexible supports made of broken rock. To clarify the assessment of bearing capacity of such structures, it is advisable to carry out specific field studies in mine conditions.

PHILOSOPHICAL FEATURES OF THE CHINESE MUSICAL TRADITION. GENERAL ANALYSIS

The article is devoted to the consideration of an interesting topic, the influence of philosophy on the formation of ritual Chinese music, which is taken as the basis for the formation of a unified state culture that creates "correct ethical" views in society. Modern ritualism actively studies all the factors and conditions of the formation, conduct and influence of ritual on society, based on a large volume of heterogeneous material. The researchers identified the principles of ritual formation as a social sacred act, taken as the basis of social practice, where language, poetry, music, power, productive activity, and court are built on the basis of ritual. The ritual allows you to rank society by strata, systematizing it, defining each of its place and types of occupation in accordance with the sacred heritage. This aspect was implemented in the ritual tradition of the Chinese Empire, where the ritual itself corresponded to the creation of the empire from the original chaos. The complexity of the ritual required the formation of a mechanism for the harmonization of the sacred-ritual factor through music, songs and dances, which was realized in Chinese culture through the creation of ritual music, which was included as a necessary element in the system of ritual (sacred) and the structure of society (profane) combining them. The ritual musical tradition arose and developed on the basis of a deep philosophical analysis of the experience of the formation of music and songs of the states of ancient China, conducted by Kung-tzu and his followers. As a result, we have practical experience of centuries-old state development, a powerful cultural system, and an ethnic group capable of development under the leadership of the state. At the same time, ritual music developed based on the integration of the traditional cultural achievements of the Han people and neighboring ethnic groups. The ethical principles embedded in culture by Confucian philosophy made it possible to develop music through the synergy of musical traditions of different peoples. Based on philosophy, the musical structure, lyrics, dance movements were selected and the composition of the participants was determined.

Bukovyna as part of the Austro-Hungarian Empire and its socio-economic development on the eve of rail way construction

This article examines how the socio-economic conditions in Bukovyna influenced the formation and development of the railway network in the region. It explores whether these processes aligned with the global trends of the time. Based on the analysis of scientific literature, memoirs, and archival materials, it was found that the topic of the formation and functioning of the railway network in Bukovyna had not been systematically studied. It was revealed that the Austrian authorities, by turning Bukovyna into an internal colony of the Habsburg Empire, kept the region in the position of a raw material appendage and a market for the industry of the empire's central provinces. The tariff, customs, credit, and tax systems introduced by the imperial government supported this process, acting in the interests of Austro-Hungarian capital. The development of the railway network was aimed at ensuring the economic interests of the empire, which affected the socio-economic development of Bukovyna. In particular, the construction of railways improved the transport infrastructure, leading to increased trade and higher volumes of raw material and goods transportation. However, this development had a dual nature. On one hand, it promoted economic growth and modernization of the region, but on the other hand, it intensified Bukovyna's dependence on the central provinces of the empire, limiting its economic autonomy and the development of local industry. The article also analyzes the impact of railway construction on the social aspects of life in Bukovyna. The railway became an important factor in migration, contributing to urbanization and the growth of the working class. However, at the same time, social tensions increased due to the unequal distribution of economic benefits and the intensification of local population exploitation. The conclusions of the article emphasize the need for further research to fully understand the impact of railway development on Bukovyna in the context of the Austro-Hungarian Empire and to compare these processes with similar developments in other parts of the world.

Development of a bulk material volume estimation system using automatic moving rail LiDAR technology

Development of a bulk material volume estimation system using automatic moving rail LiDAR technology

Application of Some Physical Seed Treatment Methods to Increase Germination of the Genus Catalpa Scop.

To increase the production volume of planting material for ornamental plants in the conditions of Central Kazakhstan, the selection of pre-sowing treatment methods for seed material becomes relevant. The use of safe and effective germination activators accelerates the biological processes of plant growth. The aim of the research was to study the impact of physical methods on the germination of Catalpa speciosa seeds as relatively safe methods of seed material activation. The seed treatment was carried out in three ways: the effect of laser irradiation, magnetic fields for 24, 72 hours, and twenty-four-hour aeration. A different response of seedlings to physical factors of influence was noted. The effect of the magnetic field allowed to increase germination by an average of 10 % compared to the control group. The impact of laser irradiation for 1‒4 minutes on the growth of Catalpa speciosa seedlings was less significant. Aeration had a positive effect on the energy of seed germination. Thus, to increase the germination of seedlings during early sowings of Catalpa speciosa seeds, it is promising to use the influence of the magnetic field and aeration.

Topology optimization of vertical shear links in eccentrically braced frames

The inclusion of additive manufacturing (AM) in the construction industry has opened new perspectives on the production of structural members. By coupling AM technologies with topology optimization (TO), significant reductions in material usage and weight can be achieved. Although TO has been applied to optimize simply supported beams, additional factors such as stress concentrations, buckling, and low-cycle fatigue from seismic loads require further investigation. This study presents a numerical approach for optimizing shear links subjected to monotonic and cyclic loading. The numerical models for conventional shear links were validated against experimental work, including cyclic loading tests on individual shear links and scaled eccentrically braced frames (EBF). The implementation of TO led to a 12 % volume reduction in the first optimized link. The optimized link demonstrated superior performance, exhibiting higher shear strength and energy dissipation capacity under both monotonic and cyclic loading. Another study examined EBFs with vertical links, achieving 12 % and 30 % reduction in material volume. The optimized links showed improvements that reached 25 % compared to the conventional link in terms of strength and energy dissipation with 12 % volume reduction, while 30 % volume reduction showed slightly less improvement over EBFs with conventional shear links.

Construction of Co9S8/SnS heterostructures encapsulated in multi-channel carbon nanofibers as long-term stable anodes for sodium-ion batteries

This study presents the design and fabrication of multi-channel self-supported anode materials Co9S8/SnS@MCNFs, through the electrospinning technique. The high compatibility of Co9S8 and SnS at the interface enables the synthesis of a more complete heterostructure within the material, enhancing the electrochemical reaction process through rational heterostructure design. Additionally, the incorporation of high theoretical capacity SnS improves sodium storage performance. The design of multi-channel carbon nanofibers (MCNFs) effectively addresses challenges such as material volume expansion and metal particle aggregation during cycling by providing large specific surface areas and enabling carbon encapsulation. The resulting pore structure and heterostructure formation, coupled with introduction of more defects, enhance the availability of Na+ active sites for electrochemically reversible processes. As expected, Co9S8/SnS@MCNFs exhibit remarkable initial coulombic efficiency (ICE = 92.6 %) and demonstrate stable long-term cycling performance (222.5 mA h g−1 at 2 A g−1 after 400 cycles) for sodium storage, with only a 0.18 % decay rate per cycle. These findings suggest promising application for the electrode material in sustained high-current discharges and long-endurance performance.

LCA applied to comparative environmental evaluation of aggregate production from recycled waste materials and virgin sources

Nowadays, all productive sectors, including the construction industry, are facing the challenge of reducing their environmental impact. To achieve this objective, numerous actions are being carried out to access greater levels of environmental and economic sustainability. Techniques as Life Cycle Assessment contribute to quantifying environmental impacts, promoting a circular economy in a sector that consumes a high volume of resources, materials, and energy while generating large amounts of gaseous, liquid, or solid emissions. The present study aims to deepen our understanding of aspects that demonstrate the benefits of using RA instead of natural aggregates. This study not only quantifies the environmental impact but also explores the effects of potential improvements in the productive system and their impact on reducing environmental harm. The Life Cycle Assessment methodology is applied to quantify and compare the environmental impacts generated in the production of a ton of mixed recycled aggregates (MRA) from construction and demolition wastes, based on the data provided by plant managers. This is compared to the environmental impacts generated in the production of one ton of natural aggregates extracted from a quarry. The results revealed that the production of mixed recycled aggregate is more environmentally beneficial, confirming a reduction of 70.66% in environmental impacts during the production of recycled aggregates, in comparison to the natural aggregates extraction. Furthermore, the economic analysis demonstrates the economic advantage since the cost of producing recycled aggregates is over 30% cheaper than natural aggregates, being more competitive even when the transportation distances from the plant to the work sites exceed those of natural aggregates.Graphical

Exploiting small punch test for mechanical characterization of cold sprayed deposits

Conventional testing procedures often encounter challenges to characterize the mechanical properties of deposits of limited thickness such as coatings. To overcome this limitation, the literature has explored various miniature-testing methods, and, among these, the small punch test has emerged as a promising solution offering the main advantage of requiring a minimal volume of material. This study focuses on cold sprayed deposits in as-sprayed and thermally treated conditions and presents the results of an experimental campaign of mechanical characterization of 316L steel and copper deposits. In parallel, small punch tests are simulated numerically with inverse analysis to estimate comprehensively the stress-strain curves. Results suggest an extremely brittle behavior of the as-sprayed specimens and a good agreement between the experimental and numerical estimations of the mechanical properties of the ductile thermally treated specimens. Ultimately, the findings highlighted the sensibility of the small punch test to the microstructure and its gradients of cold sprayed deposits.

Emergence of critical state in granular materials using a variationally‐based damage‐elasto‐plastic micromechanical continuum model

AbstractThe mechanical response of granular materials, exemplified by frictional grain interactions, is characterized by a critical state in which deformation occurs without change of material volume or stresses when subjected to large shear deformation. In this work, a granular micromechanics approach (GMA) based continuum model is used to investigate the emergence of such a critical state. The continuum description is constructed through mechanical concepts based upon elastic and dissipation energies defined for a generic grain‐pair interaction. A hemivariational principle provides the basis for considering the evolution of damage and plasticity phenomena comprising grain‐pair contact loss and irreversible deformation. As a consequence, the Karush–Kuhn–Tucker (KKT)‐type conditions are derived, which give the evolution equations for the irreversible phenomena. Notably, in this derivation there is no invocation of flow rules and other similar assumptions of classical phenomenological continuum damage and plasticity. Further, Piola's ansatz is elaborated to kinematically connect granular micromechanics of grain‐pair to the continuum description. While the concept of critical state analysis has been handled with either phenomenological approaches or discrete numerical frameworks, in the present paper this concept is examined within a micromechanics‐based continuum description. The constitutive model is established and the coupled damage and plastic irreversible quantities are assessed. The critical state is shown to emerge as grain‐pair related damage and plastic evolution in a competitive/collaborative manner during the imposed loading path.