Search Results (3,103)

With the increased power density of internal combustion engines (ICE) and growing demands for lightweight design, the connecting rod big-end bearings are subjected to significant alternating loads. Consequently, the interference–fit interfaces become susceptible to fretting damage, which can markedly shorten engine service life and impair reliability. In the present study, the effects of the big end manufacturing process, bolt preload, and bearing bush interference fit are considered to develop a coupled lubrication–dynamic model of the connecting rod big-end bearing. This model investigates the fretting damage issue in the bearing bush of a marine diesel engine’s connecting rod big end. The results indicate that the relatively low stiffness of the big end is the primary cause of bearing bush fretting damage. Interference fit markedly affects fretting wear on the bush back, whereas the influence of bolt preload is secondary; nevertheless, a decrease in either parameter enlarges the fretting distance. Based on these findings, an optimized design scheme is proposed. Full article

This study investigates the mechanical performance of concrete paving stones manufactured with recycled aggregates derived from TransMilenio slab demolition waste (CDW-A-TS) as a sustainable alternative to conventional natural coarse aggregates (river gravel) and fine aggregates (river sand). Construction and demolition waste from Bogotá’s mass transit system slabs was processed to produce recycled aggregates, which were replaced at substitution levels of 0%, 30%, 50%, and 100% by volume of natural aggregates. The mechanical properties evaluated included compressive strength, flexural strength, abrasion resistance, and water absorption, following Colombian Technical Standards (NTC) and international protocols. Results demonstrate that all CDW-A-TS mixtures exhibit enhanced compressive strength, with improvements ranging from 14.71% to 32.82% compared to the control mix. Flexural strength also increased by 1.34% to 6.13%. However, water absorption increased proportionally with CDW-A-TS content (10.66% to 25.24%). The optimal substitution level was identified at 30% CDW-A-TS based on a composite evaluation of mechanical performance (compressive and flexural strength), durability indicators (water absorption and abrasion resistance), This research demonstrates the technical viability of incorporating TransMilenio demolition waste in paving stone production, contributing to circular economy principles and sustainable urban infrastructure development. This finding aligns with prior research affirming the viability of incorporating recycled coarse aggregates in concrete prefabricates, such as paving stones, for various construction applications. Full article

The rubber industry is facing increasing pressure to adopt sustainable practices due to environmental concerns associated with the use of non-renewable resources and the growing accumulation of waste tyres and agricultural byproducts. This study explores the potential of partially replacing conventional carbon black (CB) with sustainable alternatives derived from agricultural waste (wine by-products) and pyrolysed waste tyres in natural rubber/styrene-butadiene rubber (NR/SBR) composites for tyre applications. A series of NR/SBR composites were formulated with varying ratios of CB to agricultural waste and pyrolysed tyre waste, while maintaining consistent levels of other additives. The resulting composites were then subjected to a comprehensive suite of analyses, including scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area measurements, Fourier transform infrared spectroscopy (FTIR), bound rubber content determination, Payne effect analysis, thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and mechanical property testing. Furthermore, a Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) analysis were conducted to evaluate the environmental and economic viability of the proposed CB replacements. The results reveal that the incorporation of agricultural waste and pyrolysed tyre waste can significantly impact the curing behaviour, mechanical properties, and thermal stability of rubber composites. Importantly, some of the formulations demonstrate comparable tensile strength, elongation at break, and hardness compared to traditional CB-filled composites. The LCA and LCC analyses further highlight the potential for substantial reductions in greenhouse gas emissions, fossil resource depletion, and overall production costs, thereby supporting the transition toward more sustainable tyre manufacturing practices. Full article

The consistent quality control of ultrapure water (UPW) in semiconductor manufacturing depends on removing trace organonitrogen compounds such as urea. Due to its high solubility, chemical stability, and neutral polarity, urea is inadequately removed by conventional processes. Even at low concentrations, it elevates total organic carbon (TOC) and reduces electrical resistivity. The use of reclaimed water as a sustainable feed stream amplifies this challenge because its nitrogen content is variable and persistent. Conventional methods such as reverse osmosis, ultraviolet oxidation, and ion exchange remain limited in treating urea due to its uncharged, low-molecular-weight nature. This review examines the performance and limitations of these processes and explores electrochemical oxidation (EO) as an alternative. Advances in EO are analyzed with attention to degradation pathways, electrode design, reaction selectivity, and operational parameters. Integrated systems combining EO with membrane filtration, adsorption, or chemical oxidation are also reviewed. Although EO shows promise for selectively degrading urea, its application in UPW production is still in its early stages. Challenges such as low conductivity, byproduct formation, and energy efficiency must be addressed. The paper first discusses urea in reclaimed water and associated removal challenges, then examines both conventional and emerging treatment technologies. Subsequent sections delve into the mechanisms and optimization of EO, including electrode materials and operational parameters. The review concludes with a summary of main findings and a discussion of future research directions, aiming to provide a comprehensive foundation for validating EO as a viable technology for producing UPW from reclaimed water. Full article

Municipal sewage treatment plants generate significant amounts of polluting sludge, which demands innovative valorization approaches to support its sustainable recycling. This work aimed to evaluate the valorization potential of sludge from a municipal sewage treatment plant (STP) as an alternative raw material to traditional limestone in red wall tile formulations. For this purpose, four red wall tile formulations were performed with 0%, 5%, 10%, and 15% weight of STP sludge replacing traditional limestone. The tile formulations prepared by the dry process were characterized to determine their chemical and mineral compositions, thermal analysis, and sintering behavior. The red wall tile pieces were manufactured by pressing and firing at temperatures ranging from 1150 °C to 1180 °C. The effects of STP sludge incorporation and firing temperature on the densification behavior and technological properties were investigated. The results indicated that the STP sludge exhibited good chemical compatibility for use in red wall tile formulations. Water absorption values varied between 16.52% and 19.70%, indicating compliance with the red wall tile production (BIII group). These findings demonstrate the valorization potential of STP sludge in red wall tiles, which offers a relevant recycling option for the sanitation sector and the circular economy. Full article

Brewer’s spent grain (BSG), a byproduct of the brewing process, offers a sustainable alternative applicable to human nutrition. The nutritional composition, health advantages, and value-added uses of BSG in diverse food items, including snacks, bread, cookies, and pasta, are examined in this review. Furthermore, consumer acceptance and organoleptic attributes, including texture, taste and appearance, are discussed. BSG is composed of 60% carbohydrates (of which 50% dietary fiber), 10% lipids, and 30% proteins. BSG is also high in minerals such as calcium and phosphorous and bioactive polyphenols such as catechin, p-coumaric, and ferulic acid. BSG holds significant opportunities to be utilized in enhanced food production, biofuel generation, and other industrial applications. The reported therapeutic effects of BSG include anticarcinogenic, antiatherogenic and oxidative stress reduction. Based on sensory evaluations, the maximum amount of BSG that can be added to food products to maintain consumer acceptance is 15%. There is a need to convince manufacturers and consumers of the potential of incorporating BSG into food products, the health benefits of this, and the sustainability advantages of the use of BSG. The integration of BSG into food systems will contribute to food waste minimization and the promotion of the circular economy. Full article

Natural sand (NS) is facing the problem of resource scarcity, while manufactured sand (MS) has become a favorable alternative resource due to its wide range of sources, superior performance, as well as economic and environmental protection. This study adopted MS to replace NS to prepare manufactured sand concrete (MSC). The water–cement ratio, replacement rate of MS, and stone powder content were systematically investigated for the damage evolution of rebar during bond–slip with MSC. Seven groups of specimens were tested using the center pull-out test to analyze the effects of different factors on the bond–slip characteristics (bond stress–slip curve, bond fracture energy, peak stress, and peak slip). Acoustic emission (AE) monitoring was also adopted to synchronously characterize the slip damage process of reinforced MSC. The results indicate that the water–cement ratio and replacement ratio of MS present significant influences on the bond strength of reinforced MSC, in which the smaller the water–cement ratio is, the stronger the bond strength of reinforced concrete. Further, the larger the replacement rate of MS is, the stronger the bond strength of reinforced concrete. The higher the stone powder content, the higher the bond strength, but the effect is small compared to the two variables mentioned above. In terms of AE, count and energy remain at low values in the first and middle stages, followed by larger values, proving that cracks were beginning to develop within the specimen, and then a very large signal and then splitting occurred. The information entropy is relatively stable in the first and middle stages of the test, then fluctuates with the generation of cracks, and finally fluctuates violently and then the specimen splits. The AE parameters are more active with an increasing water–cement ratio, while they are smoother with increases in the replacement rate of MS and stone powder content. Full article

Despite local and national road authorities striving to provide motorists with a durable and safe infrastructure environment, one in six UK roads are currently classed as being in poor condition. In terms of safety, Department for Transport statistics report high numbers of road incidents; 29,711 killed or seriously injured in 2023, representing little change compared to 2022. As such, reported in this paper is research aimed at developing artificial geopolymer cement mortar-based aggregate as a cost/environmentally attractive alternative to calcined bauxite for high friction surfacing applications. Work was undertaken in two distinct phases. In the first, the performance of alkali silicate-based geopolymers comprising a range of industrial wastes as binder materials was assessed using modified versions of standardized polished stone value and micro-Deval tests. In phase two, selected mixes were assessed for resistance to simulated wear by exposing test specimens to 20,000-wheel passes on an accelerated road test machine. Performance was further investigated using a dynamic friction test method developed by the Indiana Department of Transportation. Despite commercially sourced calcined bauxite aggregates exhibiting the highest performance levels, the findings from this preliminary research were generally positive, with acceptable levels of performance noted for manufactured geopolymer-based aggregates. For instance, in accordance with recommended levels of performance prescribed in BBA/HAPPAS standards, this included attainment of polished stone values higher than 65 and, following accelerated road testing, average texture depths greater than 1.1 mm. It is recognized that further research is needed to investigate geopolymer binder systems and blends of aggregate types, as well as artificial aggregate manufacturing procedures. Full article

In the construction sector, cement and concrete are among the most widely utilized manufactured materials, yet their environmental impact remains a significant concern. The concrete industry is a major contributor to carbon dioxide emissions, accounting for over 8% of global greenhouse gas emissions annually. Several reports have estimated that between 1930 and 2013, a total of 4.5 gigatons of carbon was sequestered through the carbonation of cement-based materials. This process offset approximately 43% of the carbon dioxide (CO₂) emissions resulting from cement production during the same period, excluding emissions related to fossil fuel consumption in the manufacturing process. It is well established that producing one ton of cement results in approximately 0.60–0.98 tons of CO₂ emissions, coupled with substantial energy consumption. To mitigate these environmental effects, developing low-carbon or cement-free binders has become crucial. Alkali-activated binders (AABs), derived from industrial by-products or agricultural waste materials and activated with a low-molarity or one-part activator, are increasingly recommended as sustainable alternatives to reduce greenhouse gas emissions in the cement industry and minimize the consumption of natural resources. The production of alkali-activated concrete (AAC) involves several critical factors that significantly influence its mix design, fresh properties, and compressive strength (CS) performance. This study aims to provide a comprehensive review of the key factors affecting AAC’s mix design, workability, and CS characteristics. Firstly, the study discusses various methods employed for AAC mix design and the factors influencing these designs. Secondly, it examines the impact of binder type, source, chemical, mineralogical, and physical properties, as well as alkaline activator solutions, water content, and fillers on AAC’s workability, setting times, and strength development. Additionally, the study explores the correlation matrix and predictive performance models for fresh and strength properties. Lastly, the relationship between workability and CS is extensively analyzed. The review concludes by highlighting the existing challenges and prospects of AACs as sustainable construction materials to replace traditional cement and reduce carbon emissions. Full article

Due to the insufficient durability (wear resistance) of guides made of 50SiCr4 steel tempered to a hardness of 400 HB, 14 variants of the yarn guide manufacturing process were developed. The ring spinner yarn guides were manufactured from three types of steel, from Al99.5% and its alloys, as well as from porcelain, Al₂O₃ sinter, and WC 94% + Co 6% tungsten carbide. The unit manufacturing cost and six manufacturing quality criteria were used as evaluation criteria: four parameters of the geometric structure of the surface and the maximum surface hardness, as well as the depth of hardening of the surface layer. The presented variants were then evaluated against the seven criteria, determining a set of optimal solutions in the Pareto sense. This set consisted of 12 variants. A distance function was then used to select the best manufacturing process variant, corresponding to the smallest value of the distance function. In this study, this is the process variant for which the semi-finished product is a drawn bar ø6 mm of C45 steel tempered to a hardness of 350 HB with a glazed porcelain insert. The alternative process, with a slightly higher distance function value, is the variant with the Al₂O₃ ceramic sinter insert. Full article

Additive Manufacturing is a rapidly developing technology that enables the fabrication of objects with complex geometries and high levels of customization while keeping the prototyping costs relatively low. In recent years, its application has grown to include the fabrication of end-use parts, creating new opportunities in industries such as the automotive, aerospace, mechanical, and hydraulic engineering industries. The present research paper focuses on the fabrication and evaluation of 3D-printed operational end-use parts of a water pump, which were originally made from cast iron. This approach aims to determine whether AM can be an alternative for metal parts in operational systems such as water pumps. In particular, the impeller of a centrifugal pump is remanufactured using material extrusion AM technology with PPS-CF composite polymer as a fabrication material. Subsequently, the surface roughness of the two parts is measured, and the performance of each part is predicted by creating a CFD model. Additionally, the printed part is compared to the original part by conducting a centrifugal pump performance test for each impeller. The results show that the 3D-printed impeller achieves an approximate 15% increase in overall efficiency compared to the original impeller. Full article

Biomimetic restorative treatments in pediatric dentistry increase the longevity of the restoration compared to traditional methods and aim to preserve the natural tooth structure. Prefabricated zirconia crowns have been developed as aesthetic alternatives to stainless steel crowns for full-coronal restorations of primary teeth. This study aimed to compare the fracture resistance and microleakage of two different posterior zirconia crown brands—NuSmile^® (USA) and ProfZrCrown^® (Turkey)—cemented with either conventional glass ionomer cement (GIC) or resin-modified glass ionomer cement (RMGIC). Eighty extracted primary molars were divided into four groups (n = 20). Crowns were cemented with Ketac™ Cem Radiopaque (GIC) or Ketac™ Cem Plus (RMGIC), in accordance with the manufacturers’ instructions, and then subjected to thermocycling. Fracture resistance was tested on 40 samples by applying an increasing compressive load until failure, with values recorded in Newtons (N). The remaining 40 samples were immersed in basic fuchsin dye for microleakage testing and evaluated under a stereomicroscope at 30× magnification. The results revealed that the ProfZrCrown^®/RMGIC group exhibited significantly higher fracture resistance compared to the NuSmile^®/RMGIC group (p < 0.05). No statistically significant differences were found among the other groups. Although no significant differences in microleakage were observed among the groups (p > 0.05), crowns cemented with GIC demonstrated higher microleakage levels. Within the limitations of this in vitro study, ProfZrCrown^® may be considered a promising alternative for aesthetic posterior restorations in pediatric dentistry. Full article

Stainless steel is essential in high-performance industries due to its strength, corrosion resistance, and biocompatibility. However, conventional manufacturing methods limit material efficiency, design complexity, and customization. Additive manufacturing (AM) has emerged as a powerful alternative, enabling the production of stainless-steel components with complex geometries, tailored microstructures, and integrated functionalities. Key AM methodologies, including laser powder bed fusion (L-PBF), binder jetting, and directed energy deposition (DED), are evaluated for their effectiveness in producing stainless-steel components with optimal performance characteristics. This review highlights innovations in stainless-steel AM, focusing on microfabrication, multi-material approaches, and post-processing strategies such as heat treatment, hot isostatic pressing (HIP), and surface finishing. It also examines the impact of process parameters on microstructure, mechanical anisotropy, and defects. Emerging trends include AM-specific alloy design, functionally graded structures, and AI-based control. Applications span biomedical implants, micro-tooling, energy systems, and automotive parts, with emphasis on microfabrication for biomedical micromachines and precision microforming. Full article

Supply chain resilience is a growing concern as risk becomes increasingly challenging to interpret and anticipate due to sudden global events that disrupt the core of global supply chains. This paper discusses the use of advanced technologies to enhance supply chain resilience, proposing a two-step hybrid fuzzy analytic hierarchy process (FAHP) and the technique for order of preference by similarity to ideal solution (TOPSIS) approach that evaluates a set of different supply chain KPIs or criteria that trigger possible supply chain risks, with a focus on transportation disruptions. Using FAHP, the highest potential risks from disasters are identified, and TOPSIS is used to rank alternative solutions that enhance supply chain resilience. The approach is tested on real-world applications across multiple supply chain systems involving various companies and experts to demonstrate its validity, feasibility, and applicability. Based on five criteria and six alternatives per case study, the findings showed that for manufacturing supply chains, the highest risk was attributed to travel time (46%), and the most effective solution to mitigate it was found to be strengthening highway networks (0.72). For transportation, delivery time (56%) was the primary risk, addressed by green logistics and sustainability (0.89). Full article

With the increasing demand for sustainable and cost-effective alternatives in the construction industry, polymer composites have emerged as a promising solution. This study focuses on the development of innovative composite tiles using Linear Low-Density Polyethylene (LLDPE) powder blended with epoxy resin and a hardener as a green substitute for conventional ceramic and cement tiles. LLDPE is recognized for its flexibility, durability, and chemical resistance, making it an effective filler within the epoxy matrix. To optimize its material properties, composite samples were fabricated using three different LLDPE-to-epoxy ratios: 30:70, 40:60, and 50:50. Flexural strength testing revealed that while the 50:50 blend achieved the highest maximum value (29.887 MPa), it also exhibited significant variability, reducing its reliability for practical applications. In contrast, the 40:60 ratio demonstrated more consistent and repeatable flexural strength, ranging from 16 to 20 MPa, which is ideal for flooring applications where mechanical performance under repeated loading is critical. Scanning Electron Microscopy (SEM) images confirmed uniform filler dispersion in the 40:60 mix, further supporting its mechanical consistency. The 30:70 composition showed irregular and erratic behaviour, with values ranging from 11.596 to 25.765 MPa, indicating poor dispersion and increased brittleness. To complement the development of the materials, deep learning techniques were employed for real-time defect detection in the manufactured tiles. Utilizing the YOLOv8 (You Only Look Once version 8) algorithm, this study implemented an automated, vision-based surface monitoring system capable of identifying surface deterioration and defects. A dataset comprising over 100 annotated images was prepared, featuring various surface defects such as cracks, craters, glaze detachment, and tile lacunae, alongside defect-free samples. The integration of machine learning not only enhances quality control in the production process but also offers a scalable solution for defect detection in large-scale manufacturing environments. This research demonstrates a dual approach to material innovation and intelligent defect detection to improve the performance and quality assurance of composite tiles, contributing to sustainable construction practices. Full article