Surface Abrasion Research Articles

A depth-resolved quantitative evaluation method for non-carious cervical lesions treatment with optical coherence tomography

ObjectivesThe aim of this study is prognostic assessment of surface smoothness and the presence of internal bubbles after treatment of non-cancerous cervical lesions (NCCLs) using optical coherence tomography (OCT). MethodsAfter treatment with NCCLs, cross-sectional images of the lesion parts of the sample were non-invasively acquired and analyzed. The surface smoothness between tooth and resin, resin and cemento-enamel junction, and the presence bubble inside resin was confirmed. In addition, using an algorithm that distinguishes between resin and dental structure based on OCT cross-sectional images, we quantitatively analyzed the amount of resin used in treating NCCLs and acquired 3D images. ResultsThe inner structure of the resin in each sample was checked, and the presence of bubbles was confirmed. In addition, the resin sections were separated from the tomographic images acquired by OCT to visualize 3D images. The volume of resin used in the treatment part of each NCCLs samples was quantitatively analyzed as 3.7216 ∼ 14.889 mm3. ConclusionsOCT is able to measure not only the surface abrasion provided by existing intraoral scanner, but also the size and depth location of interal bubbles, which is distinctive advantage of our method. Based on our results, OCT is a significant tool for qualitative and quantitative analysis of dental NCCLs treatment before and after treatment. Clinical significanceThe study used OCT, a non-destructive diagnostic, to reveal the structure of the resin and the location and size of bubbles after NCCLs treatment. These findings could be golden standard in determining the prognosis of NCCLs treatment.

Development of a novel bulk metallic glass bonded single-layer diamond wheel

A novel manufacturing process was employed to develop a single-layer diamond wheel using bulk metallic glass (BMG) as the matrix and diamond particles as abrasives. BMG effectively prevented graphitisation and damage to the diamond abrasives because of its lower manufacturing temperature and avoidance of brazing flux. The Titanium (Ti) coating on the surface of diamond abrasives facilitated the formation of an interleaved dissolution-diffusion interface between the two constituents, creating mechanical occlusion at the BMG-diamond interface. The strong and tight bonding interface afforded a diamond abrasive joint strength of up to 112.59 N, with the main shear failure mode being transgranular fracture instead of pull-off failure. Furthermore, the manufactured BMG-bonded single-layer diamond wheel predominantly exhibited attritious wear instead of the exfoliation of abrasives when grinding Al2O3 ceramics. Compared with contemporary electroplated grinding wheels, the developed diamond wheel demonstrated a reduction in the normal and tangential grinding forces of 32.64% and 35.86%, respectively, and a 28.22% increase in the grinding ratio, making it an excellent candidate for grinding hard and brittle materials.

Microstructure, wear and corrosion resistances of Ni–ZrO2–CeO2 nanocoatings

This study focused on the fabrication of Ni, Ni–ZrO2 and Ni–ZrO2–CeO2 nanocoatings using ultrasonic pulse electrodeposition. The research delved into examining the surface morphology, microhardness, abrasion, and corrosion resistance of these coatings. The results indicated that the Ni coatings displayed coarse grains and an irregular structure. Among the three, the Ni–ZrO2–CeO2 nanocoatings exhibited the most dense, flat and fine microstructure among all three coatings, and the average diameters of Ni grains, ZrO2 and CeO2 nanoparticles were 68.6 nm, 21.1 nm and 23.4 nm, respectively. The Ni, Ni–ZrO2, and Ni–ZrO2–CeO2 nanocoatings displayed high micro-hardness values, measuring an average of 363.1 Hv, 421.6 Hv, and 543.8 Hv, respectively. Moreover, the friction coefficient of Ni–ZrO2–CeO2 nanocoatings was approximately 0.31. When exposed to a 3.5 wt% NaCl solution at room temperature, the Ni–ZrO2–CeO2 nanocoatings displayed minimal corrosion damage, exhibiting the lowest corrosion rate of 0.06 mm/year compared to the other coatings. The incorporation of ZrO2 and CeO2 nanoparticles in the Ni–ZrO2–CeO2 coating led to grain size reduction and a more uniform, compact microstructure, contributing to enhanced corrosion resistance when compared to both Ni and Ni–ZrO2 coatings.

Exploring the Potential of Sr2+ for Improving the Post-Hardening Strength and Durability Characteristics of Cement Paste Composites

This study investigates the effects of strontium ions on enhancing the post-hardening strength and durability characteristics of hydrated cement composites, exploring their potential use as a rehabilitation method for aging concrete structures. A 30% strontium nitrate solution served as the source of strontium ions. Cement paste specimens with a water-to-cement ratio of 0.5, cured for 28 days, were submerged in the 30% strontium nitrate solution to facilitate strontium ion penetration. Compressive and flexural strength tests were conducted on the specimens and compared to those cured in deionized water. Moreover, the durability performance, including surface abrasion resistance, water sorptivity, and porosity, was examined. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffractometry (XRD) analyses were also carried out to investigate the microscopic morphology and chemical characteristics of the specimens. Results indicated that the strontium-treated specimens exhibited notable enhancements in both compressive and flexural strengths, especially in flexural strength. The specimens also demonstrated improved surface abrasion resistance, decreased water absorption, and a marked reduction in porosity. SEM analysis revealed a densified microstructure in the strontium-treated cement paste specimens, and EDS and XRD analyses showed changes in their morphology and chemical compositions and structures, indicating the formation of new types of hydrates. Accordingly, this study suggests that the strontium ion treatment method has significant potential for the maintenance and restoration of aging cementitious materials.

Polypropylene-Rendered Antiviral by Three-Dimensionally Surface-Grafted Poly(N-benzyl-4-vinylpyridinium bromide).

To inhibit viral infection, it is necessary for the surface of polypropylene (PP), a polymer of significant industrial relevance, to possess biocidal properties. However, due to its low surface energy, PP weakly interacts with other organic molecules. The biocidal effects of quaternary ammonium compounds (QACs) have inspired the development of nonwoven PP fibers with surface-bound quaternary ammonium (QA). Despite this advancement, there is limited knowledge regarding the durability of these coatings against scratching and abrasion. It is hypothesized that the durability could be improved if the thickness of the coating layer were controlled and increased. We herein functionalized PP with three-dimensionally surface-grafted poly(N-benzyl-4-vinylpyridinium bromide) (PBVP) by a simple and rapid method involving graft polymerization and benzylation and examined the influence of different factors on the antiviral effect of the resulting plastic by using a plaque assay. The thickness of the PBVP coating, surface roughness, and amount of QACs, which jointly determine biocidal activity, could be controlled by adjusting the duration and intensity of the ultraviolet irradiation used for grafting. The best-performing sample reduced the viral infection titer of an enveloped model virus (bacteriophage ϕ6) by approximately 5 orders of magnitude after 60 min of contact and retained its antiviral activity after surface polishing-simulated scratching and abrasion, which indicated the localization of QACs across the coating interior. Our method may expand the scope of application to resin plates as well as fibers of PP. Given that the developed approach is not limited to PP and may be applied to other low-surface-energy olefinic polymers such as polyethylene and polybutene, our work paves the way for the fabrication of a wide range of biocidal surfaces for use in diverse environments, helping to prevent viral infection.

Morphology of Microchips in the Surface Finishing Process Utilizing Abrasive Films.

In this study, the surface of new lapping films was analyzed, and the lapping finishing process was applied to RG7 tin bronze alloy. The research focused on examining lapping films with electrocorundum grains of nominal sizes 30, 12, and 9 μm, commonly used for achieving smooth surfaces. The manufacturing process involves placing abrasive grains and binder onto a polyester tape, resulting in a heterogeneous distribution of abrasive grains. The study investigates the impact of this random distribution on the performance of lapping films during material removal. Scanning electron microscopy was used to analyze the surface structure of abrasive films, revealing distinctive structures formed by the specific aggregation of abrasive grains. This study explores the influence of different nominal grain sizes on surface finish and aims to optimize lapping processes for diverse applications. The research also delves into microchip analysis, examining the products of the lapping film finishing process. Microchips were observed directly on the abrasive tool surface, revealing insights into their morphology and distribution. The chip segmentation frequency was determined, and they amounted to approximately 0.8 to 3 MHz; these are very high frequencies, which are unique for known chip-forming processes.

A novel method for exploring the wear resistance characteristics of ethylene propylene diene monomers‐polyamide elastomers with nano‐graphite

AbstractHansen solubility parameter theory and rheological laws were employed to investigate the microscopic cross‐linked network structure of the wear‐resistant elastomer based on ethylene propylene diene monomers (EPDM)‐polyamide elastomers (PAE)/graphite. With the condition of the same carbon black content, the wear volume of EPDM‐PAE increased after added wax powder and decreased by adding five percent graphite. The role of microscopic cross‐linked network on the wear‐resistant properties was specifically characterized by a highly linear synergistic relationship between wear volume and cross‐link density. The motion ability of micro chain segments has been characterized by the frequency sweep and the influence of the filler network has been represented by the strain sweep. Scanning electron microscope was used to characterize the micro filling structure, while stereomicroscope view was used to explore the wear interface. It was noteworthy that the graphite network layer formed on the abrasive surface on top of the abrasive grit wear transformed the wear mechanism into composite wear. This work was an innovative perspective to study rubber‐plastic/solid lubricant‐based wear‐resistant elastomers, based on microscopic network structures, which could help to obtain new wear‐resistant elastomers with specific properties.

Influence of key parameters on the performance of RAP-inclusive geopolymer concrete pavements: An approach integrating sensitivity analysis

The current study investigates the integration of Reclaimed Asphalt pavement (RAP) aggregates into geopolymer concrete, thereby providing a promising avenue for reinforcing sustainability in rigid pavement systems. Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) based geopolymer mixes were designed to accentuate the performance with regards to varying molarity of NaOH (10 M-16 M), aggregate replacement levels (0%−100%) and curing periods. The experimental findings revealed a significant decrease in 28 days of compressive and flexural strength within 14 M-100% RAP mixes (57.6% and 39.7%, respectively). Nevertheless, GPC mixes incorporating 50% coarse RAP successfully met the prescribed strength criteria, making them suitable for Pavement Quality Concrete (PQC) applications. Additionally, the assessment of porosity and Water Absorption (WA) revealed a noticeable decrease with an increase in molarity as well as RAP fractions in the mix. Long-term performance was further assessed through resistance to surface abrasion, showing a maximum abrasive depth of 0.302 mm for 10 M-100%RAP mixes, thus affirming the durability of the RAP-GPC system. Rapid Chloride Penetration Test (RCPT) additionally demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance to chloride ingress. Subsequently, the microstructural analysis and the study of solid-state NMR aided in comprehending the matrix behaviour, potentially linked to the performance of the mixes. The experimentally obtained compressive strength results were further statistically analysed through the Sensitivity Analysis (SA) approach, thereby providing a comprehensive understanding of the interplay between various strength-affecting parameters.

Machine Learning Aided Optimization of Non-Metallic Seals in Downhole Tools

Machine learning-based optimization analysis is conducted to improve the performance and reliability of non-metallic seals that undergo dynamic loading. Non-metallic seals, mostly made from elastomeric materials such as rubber, are widely used in the oil and gas industry due to their combination of hyper-elastic behavior and lack of plastic deformation under pressure and temperature cycles. However, these elastomeric materials could soften at elevated temperatures or during cyclic loading which makes them more prone to extrude from the seal region. For simple seals such as O-rings, thermoplastic anti-extrusion backup rings can be used to resist rubber extrusion. For more complex molded or bonded seals subject to cyclic loads and temperature cycles, minimizing the rubber damage and maintaining the seal integrity becomes more challenging as there may be inadequate room for backup rings. Additionally, the rubber may also experience repeated long stroke lengths during service which can cause surface abrasion. Non-metallic seals are extensively used in Sand Control Tools, a class of completion equipment. In the development of these molded and bonded seals, advanced optimization analysis techniques are important to make the seal design sufficiently robust to meet the stringent requirements of industry codes and regulations. Machine learning-based optimization analysis allows for increasing the seal performance and reliability. The Mullins effect is included in the elastomeric material model to capture the material softening effects under cyclic loading. Machine learning-based optimization starts with a feasible design space that is defined based on the controlling design parameters related to the geometry of the seal. Comprehensive Finite Element Analysis is performed on each design sample under the target cyclic load and temperature cycles. The key response parameters of the non-metallic seal are selected as the principal strain and the contact stress in the rubber which together indicate the damage and seal-ability states of the design. A Performance Objective Index is defined as a function of the key response parameters. The FEA results covering the entire design space provide the simulation-driven training data to build the surrogate model using multi-layer neural networks. The optimum design solution is found from the surrogate model which correlates the Performance Objective Index to the design parameters. The results of this study reveal that the performance of the seal is greatly affected by the ratio of the elastomeric seal volume to the gland volume into which the seal is molded. As opposed to the base design, the optimum design shows a solid performance with no signs of extrusion when the principal strain of the rubber is kept below the elongation limit throughout the load cycles, and when sufficient contact stress is developed to maintain the seal.

The use of HDPE geocells for drainage channel coating to replace reinforced concrete structures

Typically water conduction channels are lined with reinforced concrete structures. Often, such alternatives consume high construction costs and percentages of total investments destined for water infrastructure and maintenance. In this context, the function of engineering is to seek alternatives that allow, in a responsible and safe manner, to replace typical reinforced concrete structures, focusing on technical and economic aspects. Thus, the use of High Density Polyethylene (HDPE) geocells filled with concrete, to line channels, is intended to facilitate and accelerate the installation of this system, providing a good result, mainly due to its constructive simplicity. In addition, the technology in HDPE geocells is sufficiently stable to withstand the external forces generated on the fluid conduction structures, thus dispensing with the use of steel reinforcement, in addition to formwork, expansion joints, etc. Thus, some of the main analyzes used to demonstrate the effectiveness of the use of HDPE geocells filled with concrete for lining channels will be presented, as: resistance to extraction with cell confinement, shear stress, surface abrasion, stability due to under pressure and excessive deformations. Finally, the main benefits that these structures present in relation to conventional ones are listed, and a comparison addressing productivity, installation and costs, sustaining their success through executed cases, as well as successful cases applied to different requests in Latin America.

Prediction of abrasive wear and surface hardness of printed parts by SLA technology

In the present study, a prediction of hardness deterioration and abrasive wear was performed through a neural network using artificial intelligence on a material printed in SLA. This article aims to predict the mechanical properties, wear resistance and surface hardness of parts manufactured by SLA stereolithography printing. A full factorial DOE was used to associate the peculiar parameters (print orientation, cure time, layer height) to perform experiments. The mechanical properties were evaluated according to ASTM regulations, with the objective of obtaining feeding data and validation of the predictions of the Taber Wear Index and hardness using an artificial neural network. The experimental results are in good agreement with the measured data with satisfactory prediction errors with a mean square error (MSE) of 0.01 corresponding to abrasive wear using the clear resin and a mean absolute error (MSE) of 0.09 with an R2 of 0.756, the prediction with the neural network with a mean square error (MSE) of 2.47 corresponding to abrasive wear using the tough resin and a mean absolute error (MSE) of 14.3 with an R2 of 0.97. It was shown that the accuracy of the prediction is reasonable, and the network has the potential to be improved if the experimental database for training the network could be expanded. Therefore, wear and hardness mechanical properties can be predicted appropriately with an ANN.

Comparison of the Surface Abrasion Produced by Two Different Bristle Materials – An In vitro Pilot Study

Abstract Introduction: Gingival, periodontal diseases and dental caries are the most prevalent diseases of the oral cavity. Plaque is the main cause of these dental diseases. Plaque control is of prime importance for the maintenance of oral and dental health. The toothbrush is used very commonly for plaque control. A variety of toothbrushes are available, which are used for plaque removal. Toothbrushes cause abrasion and are significant in the development of tooth wear. This study aimed to compare the abrasion caused by a commercially available nylon bristle toothbrush to a biobased carbon-based bristle toothbrush. Materials and Methods: Acrylic plates were used to assess the abrasion caused by the nylon bristles and biobased carbon bristles. The surface roughness (Ra) was evaluated on a device, and the values were compared to each other. Results: Brushing with the biobased carbon bristle toothbrush was less abrasive than when nylon bristles were used. The nylon bristles showed a higher Ra value as compared to biobased carbon bristles. Conclusion: The biobased carbon bristles are less abrasive, but studies are required to compare the plaque removal capacity of such biobased carbon bristle toothbrushes.

Atomic surface achieved through a novel cross-scale model from macroscale to nanoscale.

Chemical mechanical polishing (CMP) is widely used to achieve an atomic surface globally, yet its cross-scale polishing mechanisms are elusive. Moreover, traditional CMP normally employs toxic and corrosive slurries, resulting in potential pollution to the environment. To overcome these challenges, a novel cross-scale model from the millimeter to nanometer scale is proposed, which was confirmed by a newly developed green CMP process. The developed CMP slurry consisted of hydrogen peroxide, sodium carbonate, sodium hydroxycellulose, and silica. Prior to CMP, fused silica was polished by a ceria slurry. After CMP, the surface roughness (Sa) was 0.126 nm, the material-removal rate was 88.3 nm min-1, and the thickness of the damaged layer was 8.8 nm. The proposed model was built by fibers, through integrating Eulerian and Lagrangian models and reactive force field-molecular dynamics. The results predicted by the model were in good agreement with those of CMP experimentally. A model for large-sized fibers revealed that a direct contact area of 11.12% was obtained for a non-woven polishing pad during the CMP experiments. Another model constructed via combining Eulerian and Lagrangian functions showed that the stress at the intersections of the fibers varied mainly from 0.1 to 0.01 MPa and was higher than the stress at other parts. An increase in viscosity led to a decrease in the areas with low stress, demonstrating that viscosity enhanced the stress and facilitated the removal of material. At the microscale and nanoscale, the stress of the abrasive surface exposed to the workpiece changed from 2.21 to 6.43 GPa. Stress at the interface contributed to the formation of bridging bonds, further promoting the removal of material. With increasing the compressive stress, the material-removal form was transformed from a single atom to molecular chains. The proposed model and developed green CMP offer new insights to understand the cross-scale polishing mechanism, as well as for designing and manufacturing novel polishing slurries, pads, and setups.

Milling or grinding for manufacturing of an Alloy 718 gas turbine component? – A comparison of surface integrity and productivity

Milling is traditionally the most used machining method when manufacturing complex gas turbine components. In particular those made from nickel-based superalloys. However, for larger free form surfaces, grinding may be an efficient alternative that could be used throughout the complete manufacturing route, from roughing to finishing. Hence, in this work the two processing methods has been compared in regard to surface integrity and productivity.Machining tests have been performed on case plates of heat-treated Alloy 718 using best practise setting for roughing and finishing with grinding and milling. The surface integrity of the work pieces was evaluated regarding surface topography, residual stresses, and deformation. This comparison showed that the main advantage with grinding is the ability to switch between roughing and finishing by just altering the depth of cut. Further, grinding offers lower surface roughness, compressive residual stresses, and significantly lower degree of deformation.From a productivity perspective, deep grinding may offer high material removal rates and ability to machine several work pieces in the same setup. However, grinding is limited to simpler free form geometries and may result in minor surface damages and abrasive surface residue. For selection of machining strategy, advantages and drawbacks shown in this work need to be considered for the application at hand in respect to productivity, surface integrity and requirements on fatigue life.

KİMYASAL BİLEŞİMLERİ YARDIMIYLA GERÇEK MERMERLERİN AŞINMA DİRENCİ KESTİRİMİ: YENİ BİR YAKLAŞIM

Natural stones are the widely used building materials in civil engineering and architectural projects. Surface abrasion resistance determination of natural stones is one of the important issues considered in flooring projects. This mechanical property is determined by performing standardized laboratory tests. In recent years, however, there has been considerable interest in its determination by means of indirect methods using the physical, mechanical, and mineralogical properties of stone materials. As a new approach, the present work was undertaken to investigate the potential usability of chemical compositions of true marbles as a guide to predict their Wide Wheel Abrasion (WWA) and Böhme Abrasion (BA) test values. By performing multiple linear regression analyses, statistically significant regression models with high prediction accuracies were derived (p-values < 0.05; R2 ═ 0.98­0.99). In the established prediction models MgO, SiO2, CaO, and (CaO/SiO2) ratio were determined as the most significant predictor variables. These models may be updated by inclusion of data from further studies on other types of marbles.

10Be surface exposure dating of glacier fluctuations on the eastern slope of Mount Geladandong, central Tibetan Plateau

Moraine complexes formed by multiple glaciations are well-preserved in the Mount Geladandong area, the largest center of current glaciation in the Tanggula Mountains in western China. Studies of these glacial landforms provide insights into past glacier changes and contribute to understanding palaeoclimate and palaeoenvironment in the central Tibetan Plateau (TP). Here we report on 10Be surface exposure dating of thirteen rock samples collected from a sequence of glacial landforms associated with the Gangjiaquba Glacier. Based on the dating results, historical records (topographical maps) and morphological relationships, clear Little Ice Age (LIA) landforms are identified, and other landforms are tentatively assigned Neoglacial and global Last Glacial Maximum (LGMG) ages. Dating results for samples from modern glacial landforms demonstrate that the boulders were not affected by nuclide inheritance, and that 10Be surface exposure dating may be used to constrain glacier fluctuations during the past century in high-altitude areas that have high 10Be production rates. A comparison of the ages of a glacially polished surface and adjacent glacial deposits indicates that subglacial erosion by abrasion of the rock surface was insufficient to remove cosmogenic nuclide inventories. Thus the apparent exposure age on the polished surface includes inheritance and over-estimates the actual age for the exposure of this surface. Samples from hummocky moraine have wide age spreads, indicating long-lasting surface instability after deposition of this landform. Successive reduction in glacial extent in the Mount Geladandong area since the LGMG reflects temperature and precipitation changes over this timeframe in the central TP, with climate forcing for glacial advances correlated with cooling signals in the North Atlantic that may have been transmitted to this area by the westerlies.

In Vitro Assessment of Different Toothbrush Designs on Enamel Surface Abrasion: A Profilometric Study.

The purpose of this study was to evaluate the impact of three different toothbrush designs on enamel surface abrasion. Sixty intact freshly extracted maxillary central incisors were considered for the study. All of the extracted teeth's surfaces were severely trimmed, leaving only the labial surface intact. In the trial, a conventional teeth-whitening dentifrice slurry was utilized. A brushing model was created to deliver uniform force in unidirectional motion. Dontrix Gauge was used to control the tension of the spring. The force was kept constant at 180 ± 20 g. The mounted enamel samples were separated into three groups (20 samples each) at random: group A: toothbrushes have a flat trim bristle design, group B: toothbrushes have a zigzag pattern, and group C: toothbrushes have a bi-level bristle design. For 2 weeks, each sample was brushed twice daily for 2 minutes. A profilometer was used to measure the average surface roughness. After toothbrushing, the maximum mean surface roughness score was found in zigzag pattern group (2.10 ± 0.23), followed by bi-level bristle design group (2.06 ± 0.12) and the least was in the flat trim bristle design group (1.96 ± 0.09). There was a significant difference between the different toothbrush bristle pattern groups (p < 0.001). On conclusion, the results of this study showed that, in comparison to toothbrushes with zigzag patterns and bi-level bristle designs, flat trim toothbrush bristle designs cause the least amount of surface abrasion and are relatively safe to use. Toothbrushing with toothpaste contributes significantly to dental abrasion. A variety of parameters, including toothpaste abrasivity and concentration, brushing frequency, brushing length, brushing force, and toothbrush bristle stiffness, have the potential to influence the abrasion process of dental hard tissue.

Nanoemulsion-integrated gelatin/bacterial cellulose nanofibril-based multifunctional film: Fabrication, characterization, and application

The current requirements of food safety regulations and the environmental impact stemming from plastic packaging can only be addressed by developing suitable bio-nanocomposite films. Therefore, this study is dedicated to the fabrication of multifunctional film composed of gelatin, bacterial cellulose nanofibrils (BCNF), and black pepper essential oil nanoemulsion (BPEONE) and application for duck meat preservation. BCNF was prepared through ultrasonication of cellulose derived from Komagataeibacter xylinus. BPEONE observed spherical morphology with a diameter ranging from 83.7 to 118 nm. A film matrix containing a higher gelatin proportion than BCNF was more effective in trapping BPEONE. However, increasing the BPEONE fraction showed more surface abrasion and voids in the film morphology. A flexible film with good interaction, crystallinity, and greater thermal stability (421 °C) was developed. Nevertheless, film hydrophobicity (118.89°) declined, resulting in a notable effect on water solubility, swelling, and water vapor permeability. Moreover, the film had improved antibacterial and antioxidant activities, coupled with controlled release characteristics. Consequently, the developed film effectively retarded the lipid oxidation, inhibited microbial growth, and extended the shelf life of duck meat at refrigeration (4 °C) by 3 days, and made the film a promising alternative in the realm of bio-active packaging technology.

Effect of aggregate type on the elastic modulus and compressive behavior of concrete: A case study in Colombia

The modulus of elasticity Ec, the specified compressive strength fc', the measured concrete strength, fcr', and the axial strain of the concrete at peak strength εc0 are key parameters for the analysis, design, and construction of reinforced concrete (RC) structures. These parameters require precise laboratory control, which makes routine testing and consistent reporting in the literature challenging. Therefore, in some developing countries, numerical modeling for RC structural analysis relies on results or equations proposed by international building codes as reference values, ignoring the mechanical contribution of locally available materials. This study used five gravel sources from different mineralogical origins in Colombia to evaluate the mechanical properties of twenty concrete mixtures at four water-cement ratios (0.60, 0.55, 0.49, 0.35). Analyses and comparisons of aggregate properties, including mineralogical origins, unit weight, aggregate surface, absorption, and Los Angeles Abrasion Loss (LAAL), are conducted in relation to Ec, fcr', and εc0 and are contrasted against existing literature. Two groups of concrete were defined as normal and high-strength (NS- and HS-concrete), and compressive stress-strain curves were recorded during the tests of 220 cylinders, from which Ec, fcr', and εc0 were obtained. A statistical analysis was conducted to study the main effects and interactions of the aggregate type and water-cement ratio on the modulus of elasticity. It was found that the aggregate type had a significant impact on Ec with no interaction with the water-cement ratio. It led to the development of new expressions to account for the different available aggregates, potentially improving future local building code provisions for Ec. Values of fcr' ranged from 20 MPa to 95 MPa, with the corresponding Ec / √fcr' ratio varying from 4870 to 6140 MPa for the NS-group, while being approximately 25% smaller, on average, for the HS-group. The greatest Ec values are produced by an igneous aggregate type exhibiting the lowest LAAL, while a metamorphic aggregate with 40% LAAL produces the lowest Ec values. However, both aggregates had 100% fractured faces, resulting in the highest fcr' values at 56 days (42 ≤ fcr' ≤ 44 MPa), with the fractured faces of the aggregate being the critical parameter for compressive strength. The εc0 results showed negligible median variations among the aggregate types, except for the aggregate with a smooth surface with fewer fractured faces. Median εc0 values are 0.0019 and 0.0026 for the NS- and HS-group, respectively.

The fatigue life and fractures of austenitic steel AISI 304 after the chemical-thermal treatment

The service life of components is related to surface abrasion, corrosion effects, as well as the occurrence of fatigue cracks. These effects begin to spread from the surface of the components and therefore it is very important to properly influence the mechanical properties of the materials to increase the service life. In chemical-thermal treatment, the resistance of the surface layer is increased by saturating the surface of the components with suitably selected chemical elements. This affects the change in structure and mechanical properties.The article will be focused on the analysis of fatigue and fracture mechanisms of samples made of austenitic steel AISI 304, which will be subjected to a dynamic test, especially the three-point bending test. Samples for tests will be used in two states, after chemical-thermal treatment and in the initial state for comparison. Plasma nitriding will be chosen as the chemical-thermal treatment. Plasma nitriding technology has been commercially used in industrial production to improve the fatigue, anti-corrosion and tribological properties of steels.The aim of the paper is to compare the microstructural changes that took place during the nitriding process and fractographic analysis of fracture surfaces of samples that will be subjected to a three-point cyclic fatigue load. Fractography should determine the crack initiation site, the mechanism of crack formation and propagation, and the type of fracture.