Hasil untuk "Mechanical industries"

Stefano Felicioni, Adrian Barbosa Cantu, Elisa Padovano et al.

High-performance copper alloys are increasingly sought across multiple industries, including medical, power and energy, advanced tooling, and manufacturing, due to their exceptional thermal conductivity, oxidation resistance, and mechanical strength. Among these, GRCop-42 (CuCrNb) has gained strategic importance especially in aerospace engineering, where materials must endure extreme thermal gradients and mechanical loads in high-heat-flux environments, most notably in reusable rocket propulsion and combustion chamber applications. The performance of GRCop-42 is largely controlled by a fine dispersion of Cr2Nb Laves phase particles, which strengthen the alloy through precipitation and dispersion-hardening mechanisms.Additive manufacturing techniques, especially Laser Powder Bed Fusion (L-PBF), offer the potential to further refine the microstructure due to their inherently rapid solidification rates. This study investigates the microstructural evolution of L-PBF processed GRCop-42, with a particular focus on the thermal stability and coarsening behaviour of Cr2Nb precipitates under various aging conditions. By employing advanced microscopy techniques (FESEM and TEM) alongside crystallographic analyses (XRD and EBSD), this research aims to elucidate the mechanisms of Ostwald ripening and their influence on the alloy strengthening behaviour.

Chinedu C Nsude, Rebecca Loraamm, Natalie Letsa

Fuel subsidies have been a central topic of discussion for decades in the Global South, including Nigeria, often implemented to enhance energy affordability for the population. However, on 29 May 2023, the President of Nigeria announced the elimination of the fuel subsidy, resulting in an increase in energy and electricity costs exceeding 300%. This resulted in widespread protests nationwide, significantly affecting all sectors, particularly enterprises. Thus, this study examines the impact of fuel subsidy removal on micro, small, and medium enterprises (MSMEs), as well as their level of awareness and correlation with willingness to transition to renewable energy technologies (RETs), utilizing original survey data from 1461 MSMEs across Nigeria. Results indicate that the removal of fuel subsidies impacted 90% of MSMEs surveyed. Regarding the willingness to transition to RETs, 77.2% of MSMEs expressed a positive inclination, whereas 11.7% were unwilling to undertake this transition. The willingness of MSMEs to transition is influenced by several factors, including state of residence, geographical area (settlement), level of education, enterprise category, the role of the respondents, energy type utilized by the enterprise, and the level of awareness of various RETs. The study’s findings enhance understanding of the factors influencing the adoption of RETs among MSMEs in Nigeria and the potential to inform strategies for sustainable energy development. Furthermore, the identification of specific factors influencing the transition decision provides valuable insights for targeted interventions and policymaking.

Ismail O Koklu, Nihan Aydemir, Osman Eksik et al.

This study introduces a sustainable anode material for lithium-ion batteries (LIBs) by integrating boron-phosphorus co-doped graphitic carbon nitride (BPCN) into a polyacrylonitrile-lignin (PAN-Lignin) matrix. The composite leverages lignin’s renewable nature and BPCN’s heteroatom-rich structure to address critical challenges in conventional LIB anodes, such as reliance on fossil-derived materials and limited electrochemical performance. Centrifugal spinning and controlled carbonization (800 °C under argon) yielded hierarchically porous PAN-Lignin/BPCN fibers with expanded interlayer spacing (0.34–0.38 nm), as confirmed by XRD and FTIR. The optimized 75:25 PAN-Lignin/BPCN composite demonstrated exceptional lithium-ion storage, achieving an initial discharge capacity of 522.46 mAh g ^−1 at 0.5 A/g, 1.4× higher than undoped PAN-Lignin anodes—and retained 72.3% capacity (178 mAh g ^−1 ) over 50 cycles. Electrochemical analysis revealed synergistic effects: BPCN enhanced electronic conductivity via polarized B–N/P–N bonds, while the lignin-derived carbon framework provided interconnected porosity for efficient ion diffusion. EIS showed low initial interfacial resistance (7.319 Ω) and charge transfer resistance (303 Ω), though post-cycling R _ct increased to 710 Ω due to SEI formation. The composite outperformed single-doped analogs (BCN: 467 mAh g ^−1 ; PCN: 498 mAh g ^−1 ) and conventional lignin-based carbons, attributed to BPCN’s dual role in stabilizing the SEI layer and introducing active sites. Sustainability was emphasized through lignin’s carbon-negative sourcing and a 200 °C reduction in carbonization temperature compared to graphite anodes. This work advances sustainable LIB technology by replacing >75% fossil-based components with biomass-derived materials while achieving performance metrics rivaling synthetic graphite. The 75:25 PAN-Lignin/BPCN composite sets a benchmark for biomass anodes, aligning with global decarbonization goals. Future efforts should focus on SEI stabilization and full-cell integration to bridge the gap between lab-scale innovation and commercial energy storage systems.

Amel Gacem, Krishna Kumar Yadav, Zeba Tabassum et al.

Plastics have long been the dominant material in packaging industries; however, their prevalence is gradually decreasing due to increasing government regulations and growing industry shifts toward eco-friendly alternatives. This transition aims to meet sustainability targets, reduce environmental pollution, and improve brand perception. Although bioplastics are biodegradable and eco-friendly, their mechanical strength, thermal stability, and barrier properties often fall short, limiting their application in advanced packaging that requires durability and low permeability. Concurrently, a large quantity of eggshell waste, rich in calcium carbonate, is discarded in landfills, contributing to environmental pollution. The challenge of managing this waste, along with overcoming the limitations of bioplastics, calls for innovative solutions. This review discusses the potential of eggshell waste as a sustainable material in bio-packaging. It highlights how eggshells can serve as mechanical reinforcements in bioplastics through filler incorporation, transforming them into functional materials such as powders, nanoparticles, and derivatives like calcium oxide, calcium chloride, and calcium carbonate. Biopolymers such as polylactic acid (PLA) and polyvinyl alcohol (PVA) are frequently studied for integrating eggshell-derived materials. These materials significantly improve the mechanical, thermal, and barrier properties of bioplastic films, addressing both environmental and industrial challenges. The review also explores the obstacles and future directions in using eggshell waste in bioplastics, such as compatibility issues, scalability, and the need for optimized processing techniques. These advancements contribute to waste valorization and the development of eco-friendly materials, promoting a circular economy.

Atif Shazad, Muhammad Uzair

Shielded Metal Arc Welding (SMAW) is the most widely used welding technique in engineering industries. Compared to other arc welding techniques like TIG, SMAW is less heat-concentrating. However, welding thick jobs using SMAW can result in serious issues such as structural distortion due to non-uniform input heat distribution. High thermal stresses and distortions can degrade mechanical properties, similar to high input heat. Fast heat removal may prevent such defects, and different quenching media like sand, water, and oil were used to investigate variations in mechanical properties. High-strength low-alloy steel was selected due to its good weldability and easy availability, which makes it suitable for many industrial applications, such as in the space and defense industries. The tensile testing results showed that oil quenching was superior to other quenching techniques because oil-cooled joints had the highest tensile strength and ductility. However, water-cooled joints showed the highest yield strength, but oil-quenched joints had the highest welding efficiency. The hardness of water-cooled joints in the heat-affected zone and weld zone was greater due to rapid cooling in water. The impact energy of oil-cooled joints in the heat-affected zone was superior to that of other joints. Overall, the mechanical properties of oil-cooled joints were superior and showed better geometric configuration, such as minimal distortions.

Amelia Seifalian, Alex Digesu, Vik Khullar

Graphene is the wonder material of the 21st century, promising cutting-edge advancements in material science with significant applications across all industries. This study investigates the use of a graphene-based nanomaterials (GBNs) ans trade-registered Hastalex^®, as novel materials for surgical implants aimed at treating pelvic organ prolapse (POP). This study investigates the mechanical properties and physicochemical characteristics of the material, mainly focusing on its potential to address the limitations of existing polypropylene (PP) implants, which has been associated with numerous complications and banned across multiple countries. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) confirmed the bonding between functionalised graphene oxide (FGO) and the base polymer chain. Hastalex exhibited excellent mechanical properties with 58 N/mm² maximum tensile strength at break and 701% elongation at break, whilst maintaining its shape with no plastic deformation. These results were comparable to that of sheep pelvic muscular tissue. Hastalex demonstrated its hydrophilic properties from contact angle measurements. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed a uniform plane with surface nanotopography, promoting cell-to-material interaction. The results confirmed the suitability of Hastalex in the development of a new pelvic membrane to treat POP.

Mahamood Ansari, Imtiaz Ali Khan, Umair Arif

Aluminum Hybrid Composites (AHC) microchannels find extensive applications in aerospace, refrigeration and air conditioning (RAC), microelectronics, automotive, biomedical, and marine industries due to their improved mechanical properties. The combination of lower density, high hardness, elevated thermal and electrical conductivity, superior elasticity, and heightened oxidizing ability at low temperatures makes machining aluminum hybrid composites challenging through orthogonal methods in an open environment. Therefore, it is imperative to investigate the impact of various machining conditions to determine optimal parameter values for microchannel fabrication in aluminum hybrid composite materials. This study aims to identify the ideal machining parameters for Al–SiC micro-SiC nano hybrid composites using wire electrical discharge machining. Four distinct process parameters (pulse on time, gap voltage, wire tension, and wire feed rate) and two response parameters (material removal rate (MRR) and surface roughness (SR)) were considered for process optimization. Additionally, finite element modeling was conducted for the aforementioned process, and the results were compared with experimental outcomes. Single-variable optimization yielded maximum MRR at 125 tons (μs), 25 SV (volt), 12 WT (kgf), and 2 WFR (m/min), and minimum SR at 125 tons (μs), 10 SV (volt), 12 WT (kgf), and 4 WFR (m/min). Single-variable optimization for simulations resulted in maximum MRR at 125 tons (μs), 40 SV (volt), 4 WT (kgf), and 6 WFR (m/min), and minimum SR at 110 tons (μs), 10 SV (volt), 12 WT (kgf), and 2 WFR (m/min). Precise modeling aids in minimizing unnecessary machining, enabling exploration of a broader range of experimental results, thereby promoting environmentally friendly and sustainable machining practices.

Hidayatul Fitri, Gürkan A. K. Gürdil, Bahadır Demirel et al.

Abstract The West Nusa Tenggara (WNT) province is one of the regions that contribute the most to the production of rice, corn, and cacao. The residues of these crops increase as production increases. The potential availability of the residue was calculated on the basis of the amount of agricultural product and the availability of unutilized residues. The estimated potential energy and collected data were processed and combined with converted factors, such as the yield per hectare and the calorific value, taking into account another purpose, the use of domestic residues for animal feed. Paddy straw, corn straw, and corn cobs had the highest percentage of residue availabilities, 85.91%, 82.26%, and 88.25%, respectively. In addition, the WNT regency has a rich diversity of agricultural residues from superior commodities such as rice, corn, coffee, coconut and cacao. The calculation of the total heating value (THV) of the agricultural residue available reached up to 42.4 PJ. Furthermore, the use of biomass for bioenergy resources is promising, particularly for the WNT region, with the potential for unused agricultural residues. The dependence on unsustainable energy, such as coal and fossil fuel, can be reduced by deploying and developing energy production from biomass use. Therefore, the potential for bioenergy generation and the availability of biomass can be developed for sustainable agriculture and energy management.

Binbin Zhang, Mengxin Jia, Chaobo Chen et al.

This study proposes a wind farm active power dispatching (WFAPD) algorithm based on the grey incidence method, which does not rely on an accurate mathematical model of wind turbines. Based on the wind turbine start-stop data at different wind speeds, the weighting coefficients, which are the participation degrees of a variable speed system and a variable pitch system in power regulation, are obtained using the grey incidence method. The incidence coefficient curve is fitted by the B-spline function at a full range of wind speeds, and the power regulation capacity of all wind turbines is obtained. Finally, the WFAPD algorithm, which is based on the regulating capacity of each wind turbine, is compared with the wind speed weighting power dispatching (WSWPD) algorithm in MATLAB. The simulation results show that the active power fluctuation of the wind farm is smaller, the rotating speed of wind turbines is smoother, and the fatigue load of high- speed turbines is effectively reduced.

Martin Nagl, Oskar Haske-Cornelius, Wolfgang Bauer et al.

Abstract Background Pulp refining is an energy consuming, but integral part of paper production with the aim to increase tensile strength and smoothness of paper sheets. Commercial enzyme formulations are used to lower the energy requirements by pre-treatment of pulp before refining. However, a high number of different commercial enzyme products are available on the market containing enzymes of varying origin and composition, which complicates the prediction of their behavior, especially using different pulp types. Results Endoglucanase-rich enzyme formulations were characterized regarding enzyme activity at different temperatures, resulting in a significant decrease of activity above 70 °C. Some enzyme preparations additionally contained arabinosidase, xylanase and β-glucosidase activity consequently resulting in a release of xylose and glucose from pulp as determined by high-performance liquid chromatography. Interestingly, one enzyme formulation even showed lytic polysaccharide monooxygenase (LPMO) activity of 3.05 nkat mg−1. A correlation between enzyme activity using the endoglucanase specific derivatized cellopentaose (CellG5) substrate and enzyme performance in laboratory PFI (Papirindustriens forskningsinstitut) refining trials was observed on softwood pulp resulting in a maximum increase in the degree of refining values from 27.7°SR to 32.7°SR. When added to a purified endoglucanase enzyme (31.6°SR), synergistic effects were found for cellobiohydrolase II (34.7°SR) or β-glucosidase enzymes (35.7°SR) in laboratory refining. Comparison with previously obtained laboratory refining results on hardwood pulp allowed differences in enzyme performance based on varying pulp types to be elucidated. Conclusions Interestingly, the individual enzymes indeed showed different refining effects on softwood and hardwood pulp. This difference could be predicted after development of an adapted enzyme activity assay by combination of the derivatized cellopentaose CellG5 substrate with either softwood or hardwood sulfate pulp.

Naudereh B. Noori, Jessica Yi Ouyang, Mohammad Noori et al.

Total ankle replacement (TAR) is the replacement of a damaged arthritic ankle joint with a prosthetic implant to eliminate the source of resultant pain and swelling. Historically, however, the ankle joint has been one of the most difficult joints to analyze and replicate for successful replacement due to its complex anatomy and multiplanar motion. Ankle fusion, the standard of care for end stage ankle arthritis, has excellent functional outcomes but results in loss of motion at the joint. TAR was first attempted in the 1970s and by the early 1990s, prosthesis designs more closely mirrored the natural anatomy of the ankle and TAR was no longer considered an experimental procedure. Although the outcomes of TAR have significantly improved over this short period of time, there are still many areas that warrant further investigation including (1) optimal patient selection, (2) number of prosthesis components, (3) bearing type, (4) revision rates and causes and (5) comprehensive finite element models (FEM) of the ankle. The main goal of this paper is to present a literature review on the background and evolution of TAR, the current state of practice and prosthesis types and challenges and directions for future improvement.

Mykhailo Sukach, Svitlana Komotska

В природному стані тиксотропні явища в ґрунтах найбільш часто виникають при зовнішніх навантаженнях динамічного характеру: землетрусах, вібрації від транспортних засобів, що рухаються, працюючих машин і механізмів. Відомості про дослідження тиксотропії ґрунтів свідчать про те, що при динамічному навантаженні зменшувати міцність і переходити в рідкий стан можуть дисперсні ґрунти різного типу, генезису і віку. Вплив динамічного навантаження особливо суттєвий у випадку слабоущільнених і водонасичених піщаних та глинистих ґрунтів. При динамічному навантаженні може відбуватися як ущільнення ґрунту і відповідно підвищення його міцності, так і зменшення міцності. Частіше доводиться стикатися з процесами зменшення міцності і розріджування ґрунтів при динамічному впливі. Найбільш вивчені процеси, що відбуваються у водонасичених пісках. Стан розрідження при вібрації виникає внаслідок руйнування контактів між окремими зернами, тривкість піщаного ґрунту падає практично до нуля. Після зняття вібронавантаження піщинки під впливом власної ваги переміщуються вниз, викликаючи стискання рідкої фази. Чим більше піски містять тонкодисперсних часток і органічної речовини, тим довше вони зберігають рідиноподібний стан, тим повільніше відбувається відтискання води і ущільнення. Можливість розрідження піщаних ґрунтів визначається не стільки природною пористістю, скільки напруженим станом ґрунту і характером вібровпливу.

Joseph E. Iboyi, Michael J. Mulvaney, Kipling S. Balkcom et al.

Abstract Brassica carinata, a nonfood oilseed crop, is used to produce renewable fuels because of its high oil content and favorable fatty acid profile. Production in the southeastern United States is relatively new, and information on agronomic management practices to optimize growth and yield is limited. Since optimal seeding rate may depend on the land preparation method for this small‐seeded crop, a study was conducted to evaluate the effect of tillage system (conventional, no‐till, broadcast‐disc, and ripper‐roller) and seeding rate (1.12, 5.60, 10.09, and 14.57 kg seed ha−1) on the performance of B. carinata. A randomized complete block design with a strip‐plot restriction on randomization and four replications was implemented in Headland, AL, Jay, FL, and Quincy, FL, over five site‐years during the 2017–2018 and 2018–2019 growing seasons. Data were collected on soil residue cover; plant population; soil penetrometer resistance and moisture; biomass (including carbon and nitrogen); stalk diameter; yield and yield components; seed oil, protein, and glucosinolates concentration; and oil composition. Soil penetrometer resistance was significantly affected by tillage system, with the ripper‐roller consistently having the lowest penetration resistance values across all site‐years. Ripper‐roller tillage had the highest oil content and lowest protein and glucosinolate contents. Yield response to tillage system was variable. Among seeding rate treatments, yield was lowest at 1.12 kg seed ha−1 and similar among 5.60, 10.09, and 14.57 kg seed ha−1 at all site‐years. There was no tillage by seeding rate interaction for yield. Results indicate that among seeding rate treatments used, 5.6 kg seed ha−1 rate was optimal at all site‐years regardless of land preparation method and is thus the recommended seeding rate for commercial carinata production in the Southeastern United States.

Світлана Федорівна Гавенко, Олена Георгіївна Котмальова, Марта Тарасівна Лабецька

Shrink label today is one of the leading innovative solutions in the field of packaging labeling. Heat-shrinkable film has mechanical strength, elasticity and moisture-proof properties, easily changes linear dimensions under the influence of temperature, which allows it to take the form of packaged products, prevents unauthorized opening and forgery, and attracts buyers through original design solutions. The technology of heat-shrinkable labelling of products is used in the pharmaceutical, cosmetology, food, dairy, confectionery industries. To preserve the product’s proper appearance until the end of its service life, as well as to be able to decorate it printing on the shrink label is performed on its inner side. Gravure and flexographic printing technologies are mainly used to apply images to shrink labels. The specifics of the technological process of manufacturing a shrink label determines the use of materials with different physical properties: transparency, gloss, thickness, strength, coefficients of friction and tensile, temperature, percentage and time of shrinkage, which significantly affects its final cost. The most widely used are PET and PVC films. PVC film is deformed at lower temperatures and is more resistant to the external environment, while the use of PET films allows to achieve better thermal shrinkage and, accordingly, to ensure higher print quality. When applying the information to the heat-shrinkable film, it can be used water-based inks, but then there is a possibility of blurring of the image when passing the package through the steam furnace. As an alternative to printing on such films, UV fixing inks are used, which allows to apply multi-color complex images on any type of material, but this method is quite expensive due to the high cost of inks and printing equipment. Therefore, it is important to conduct system-technical, economic analysis and determine the most cost-effective and efficient technology for the production of shrink labels.

Eric W. Slessarev, Erin E. Nuccio, Karis J. McFarlane et al.

Abstract Perennial bioenergy crops have been shown to increase soil organic carbon (SOC) stocks, potentially offsetting anthropogenic C emissions. The effects of perennial bioenergy crops on SOC are typically assessed at shallow depths (<30 cm), but the deep root systems of these crops may also have substantial effects on SOC stocks at greater depths. We hypothesized that deep (>30 cm) SOC stocks would be greater under bioenergy crops relative to stocks under shallow‐rooted conventional crop cover. To test this, we sampled soils to between 1‐ and 3‐m depth at three sites in Oklahoma with 10‐ to 20‐year‐old switchgrass (Panicum virgatum) stands, and collected paired samples from nearby fields cultivated with shallow rooted annual crops. We measured root biomass, total organic C, 14C, 13C, and other soil properties in three replicate soil cores in each field and used a mixing model to estimate the proportion of recently fixed C under switchgrass based on 14C. The subsoil C stock under switchgrass (defined over 500–1500 kg/m2 equivalent soil mass, approximately 30–100 cm depth) exceeded the subsoil stock in neighboring fields by 1.5 kg C/m2 at a sandy loam site, 0.6 kg C/m2 at a site with loam soils, and showed no significant difference at a third site with clay soils. Using the mixing model, we estimated that additional SOC introduced after switchgrass cultivation comprised 31% of the subsoil C stock at the sandy loam site, 22% at the loam site, and 0% at the clay site. These results suggest that switchgrass can contribute significantly to subsoil organic C—but also indicated that this effect varies across sites. Our analysis shows that agricultural strategies that emphasize deep‐rooted grass cultivars can increase soil C relative to conventional crops while expanding energy biomass production on marginal lands.

Volodymyr Rashkivskiy, Roman Bordyug

На сьогоднішній день зберігається тенденція використання землерийної техніки зі змінними робочими органами. З точки зору технології виконання робіт це має економічно доцільне обґрунтування [1]. Проте, якщо розглядати довговічність окремих вузлів машини, така експлуатація базової машини призводить до різкого зменшення її довговічності та погіршення експлуатаційних показників, особливо у випадку використання робочих органів активної дії. Гідромолот є активним видом обладнання, що динамічно впливає на базову машину. Під час роботи гідромолота на базову машину діє знакозмінна сила, спрямована уздовж поздовжньої осі молота, обумовлена зворотнопоступальним рухом бойка гідромолота. Динамічний вплив гідромолота на базову машину виявляється  у створенні більш високого вібраційного навантаження, ніж при використанні змінного обладнання інших видів. Підвищений рівень вібраційних навантажень є причиною різкого погіршення експлуатаційних показників машини, що може нівелювати економічну доцільність використання змінного робочого обладнання. Практично проблема гасіння негативних коливань вирішується шляхом використання віброізоляції окремих вузлів машини: внутрішніх вузлів змінного навісного обладнання, елементів підвіски навісного обладнання на базову машину, стрілового обладнання тощо. Засобами ізоляції можуть бути демпфери, системи демпферів або поліуретанових подушок в конструкції гідромолота або систем його навіски на базову машину. Тому доцільним є пошук та аналіз технічних рішень віброізоляції навісного ударного обладнання одноківшевого екскаватора з метою визначення актуальності даної проблеми та подальшого аналізу технічних рішень. Аналіз доцільно проводити по міжнародній класифікації винаходів шляхом патентного пошуку, що найбільш повно відображає реальний стан розвитку визначеної галузі.

Yuriy Abrashkevych, Grigory Machishin, Elena Chovnyuk

Щорічне споживання абразивних армованих кругів обраховується сотнями мільйонів штук. Круги є складною композицією, яка складається із абразивного зерна, що закріплене в полімерній матриці. В процесі аналітичних досліджень встановлено, що зносостійкість кругів в основному визначається теплофізичними показниками бакелітової зв’язки. Визначення кореляційного зв’язку між зносостійкістю абразивного армованого круга та теплофізичними показниками полімерної матриці дозволить підвищити його зносостійкість та експлуатаційні показники. Визначення температури, що виникає в процесі різання чи зачищення є складною задачею. Її вирішення дозволить змінювати теплофізичні параметри складових круга і, як наслідок, стане можливим керувати тепловими процесами та зносостійкістю абразивних відрізних і зачисних кругів армованих склосіткою. Дослідження проводилися експериментальним шляхом з реєстрацією питомої теплоємності та теплопровідності, що залежать від матриці круга. Визначався вплив армувальної склосітки на теплофізичні показники. Встановлено, що скосітка суттєво не впливає на теплопровідність круга, а також, що між зносостійкістю абразивного армованого круга та коефіцієнтом температуропровідності існує кореляційний зв'язок. Зі збільшенням коефіцієнта температуропровідності на 50% коефіцієнт шліфування збільшується на 20%. Одним із важливих напрямків підвищення зносостійкості абразивних армованих кругів є введення в їх склад модифікаторів, які дозволяють підвищити теплопровідність і одночасно знизити теплоємність інструмента. Це може бути досягнуто шляхом уведення домішок як у зв’язуюче, так і в армуючу склосітку круга, а також шляхом металізації абразивних зерен та застосуванням нових зв’язуючих з підвищеними теплофізичними властивостями.

S. N. Sanin, N. A. Pelipenko

Advantages and prospects for the use of mobile robotic machine-tools in the manufacture of large parts in the mining, cement and nuclear industries are considered, as well as the importance of using welded structures to reduce production costs. Schemes for finishing mechanical machining of welded large-sized parts such as bodies of revolution with the use of mobile robotic machine-tools equipped with a belt-grinding tool, an enlarged description of the technological process for manufacturing a large-sized shell of a welded structure are presented. The conclusion is made that it is necessary to take into consideration the use in the industry of frameless production technology, especially for the machining of large-sized parts, and the use of small mobile robotic machine-tools is a productive approach and has a prospective character. The technological approaches proposed in the article make it possible to remove the restriction on the overall size and mass of the parts being manufactured, which are proposed to be manufactured directly at the site of future operation. The effectiveness of this technology is confirmed both by theoretical research and by practical data of the authors. It was noted that the production by the domestic machine-tool industry of mobile universal and special robotic machine-tools will allow the country's engineering industry to be brought to a new, high-quality world level.

Haris Rudianto, Gwang Joo Jang, Sang Sun Yang et al.

Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. Formation of liquid phase seems to support achieving high sintering density. Optimum mechanical properties also were obtained under those conditions. T6 heat treatment was done to improve the mechanical properties by formation of precipitation strengthening, and MgZn2 appears to be dominant strengthening precipitate. X-ray diffraction, optical microscopy, and SEM-EDS were used to characterize powder, and sintered and heat treated samples.

Riho HIRAMOTO, Kuniaki TOYODA, Kotaro SATO

Flow visualization, particle image velocimetry (PIV), and fluctuating static pressure measurements were carried out simultaneously in a turbulent shear flow separated from a sharp-edged fence to estimate the probable location of the sound source that is closely related to vortex motion and aerodynamic sound generation. The measurement of the fluctuating static pressure is an effective way to detect vortices from pressure drops and the sound source term of the dilatation theory proposed by Ribner, which is a double time derivative of the fluctuating static pressure. Therefore, in this study, attempts were made to find the relationship between variations in the waveforms of the fluctuating static pressure, sound source term, and vortex motions obtained from the flow visualization and PIV measurements. From the results, it was revealed that pressure drops deduced from the waveforms agreed with the visualized vortices, and the waveform of the sound source term was almost the same as that of the aerodynamic sound. The results suggest that this simultaneous measurement method is useful for determining the mechanism of aerodynamic sound generation.