Changes In Hardness Research Articles

Mechanical and surface characterisation of additively manufactured polyetheretherketone for the tribo test

Purpose The additive manufacturing process, such as fused filament fabrication based on material extrusion, fabricates the samples layer-by-layer. The various parameters in the process significantly affect the dimensions, structure and mechanical properties of the fabricated parts. The purpose of this paper is to investigate the surface and mechanical properties that can affect the contact characteristics with other materials during tribological tests. Design/methodology/approach The investigation of 3D-printed Polyetheretherketone (PEEK) includes the measurement of dimensions, microhardness, surface roughness, surface energy and tensile strength to define material characteristics. The crystallinity is measured using an X-ray diffractometer to understand the hardness behaviour. Findings The printing parameters affect its surface roughness, hardness and crystallinity. This change in parameters such as layer thickness and infill density impacts mechanical properties such as hardness and surface roughness, which will influence the contact mechanism with the counter body during any tribological test. The change in a single parameter during the sample fabrication and the change in the surface and mechanical properties are observed. Research limitations/implications The material cost plays an important role in conducting numerous destructive tests, which is a major limitation to conducting parameter optimisation by varying more parameters. The study is limited to the as-fabricated samples rather than finished samples and without any heat treatment. Achieving optimal parameters is integral to the success of additive manufacturing, ensuring the production of components with consistent performance. Practical implications The study aims at the application of 3D-printed PEEK for bush or journal bearings that can be directly used in practice. The mechanical properties discussed in this paper can fill the gap between theory and practice. Social implications The research provides all fundamental properties, including the printing parameters and their effect on the dimensions and surface structure, which are required to understand the material and its use. The results are consistent as at least four samples were tested for tribological behaviour. The conclusion is updated as per suggestions. Originality/value The study outlines the relationship between the change in layer thickness and infill density with changes in surface energy, surface roughness, hardness and tensile strength. The deformation and adhesion during the friction test depend on these properties.

Effect of Storage Temperature on Fruit Hardness and Anthocyanin Biosynthesis in Red Peeled Banana (Musa acuminata Hongmeiren)

Bananas (Musa spp.) are a popular tropical fruit grown worldwide and are typically harvested when 70% to 80% plump. Postharvest storage is crucial for maintaining fruit quality, with temperature playing a key role due to banana sensitivity to low temperatures. Red peeled bananas, such as the cultivar Hongmeiren, stand out for their unique red peel and pink pulp when ripe. These bananas offer nutritional benefits and are rich in anthocyanins compared with yellow bananas. This study focused on the hardness change, anthocyanin content, and the expression of related genes in red peeled bananas at different temperatures. Results showed that pulp hardness reached an edible state after 4 days at 19 and 25 °C, with stability thereafter. Storage time at 10 °C was longer and anthocyanin content remained stable across temperatures. Gene expression analysis indicated that genes including MaPAL, MaCHS, MaCHI, MaDFR, and MaANS related to anthocyanin synthesis were highly expressed at 10 °C, potentially preserving anthocyanin content and fruit appearance. Although higher anthocyanin content was observed at 19 and 25 °C, black spots appeared on the fruit peel after 8 days, affecting its quality. After 30 days of storage at 10 °C, a significant number of black spots appeared on the peel of the fruit, leading to a gradual loss of its nutritional value. This study indicates that red peeled bananas can be stored for longer periods while maintaining their appearance quality at 10 °C, as opposed to 19 and 25 °C. Hence, it is recommended to store red peeled bananas at low temperatures, especially following ethylene treatment or during periods of high temperatures.

АНАЛИЗ ПРОИЗВОДИТЕЛЬНОСТИ ХМЕЛЕСУШИЛКИ С ЧАСТИЧНОЙ РЕКУПЕРАЦИЕЙ ТЕПЛОВОЙ ЭНЕРГИИ

Drying is an integral part of the technological process of commercial hop production. Depending on the production volume and the level of automation of the process, there are several ways to dry hop cones, including convective, microwave and sublimation. At the same time, dryers have different ratios of quality and productivity. Reducing energy costs for drying hops is an important area in the development of hop growing. In this regard, modernization and analysis of the productivity of hop dryers is a pressing issue in the current conditions of rising production costs. The aim of the research is to analyze the productivity of the MXS-25 hop dryer, modernized by installing a heat pump in the air circulation circuit and having adjustable heat recovery. The air temperature in the drying chamber was successfully controlled in the range of 60 ± 2 ° C. The preheating time required to achieve the air temperature was approximately 0.5 hours, which corresponds to approximately 5% of the total hop drying time. Comparison of the measured and calculated energy consumption values showed that the experimental values were in the range of 10.2 kWh to 11.5 kWh, averaging approximately 10.85 kWh during the experiment. Accordingly, the calculated values were in the range of 8.9 kWh and 10.2 kWh, averaging 9.55 kWh. A series of experiments comparing the drying performance using partial recovery showed that with an increase in the ambient temperature to 24 °C, the maximum relative moisture separation rate reached 6.23 kg/(kWh) with a bypass ratio of 0.86, which was higher than that of 5.54 kg/(kWh) for drying with full recovery. The partial heat recovery system is superior to the full recovery system in terms of energy efficiency and increased hop drying performance.

Evaluating mechanical performance of coconut fibre reinforced polymer composites with variable fibre content

The rapid growth of composite materials, leveraging natural ingredients such as dried fruit, rice husk, wheat husk, straw, and hemp fibres, has expanded their applications and market presence. Among these, coconut fibre stands out due to its high tensile strength, making it a promising reinforcement for polymer composites. However, increasing the coconut fibre content can reduce the cohesion and some properties of the composites. This study investigates the impact of the weight percentage of coconut fibres on the mechanical properties of coconut fibre-reinforced composites. Various composites were prepared with different weight percentages of coconut fibre, and their mechanical properties were evaluated using tensile tests with a Universal Testing Machine Instron 8872 and hardness tests with a Digital Shore Scale “D” Durometer. The results indicate significant changes in tensile strength, tensile strain, and hardness corresponding to the weight percentage of coconut fibre. This research highlights the importance of optimizing fibre content to achieve balanced mechanical properties in coconut fibre-reinforced composites.

The Hardness Change Due to High-Speed Impact on A36 Steel on Penetration Testing of School Barrier Systems

Impact Doors and Windows are increasingly on demand for safety and security. They already existed, standardized in in continual improvement.

The Morphometric and Hydrological Analysis of the Largest Valley Basin in the Western Plateau of Iraq

The study was carried out to see whether it would be possible to use remote sensing and Geographic Information System (GIS) to create a morphometric geodatabase for the largest valley basin in the western Plateau (Houran Valley), Iraq. ArcGIS V.10.8 measured morphological or hydrological features using a digital elevation model (DEM). These properties are considered a crucial database for planning for dry or wet river basins and valleys, saving time, money, and resources compared to extensive regional research. A quantitative investigation of the morphological characteristics determined that the longitudinal drain density was 0.1698 km/Km2, indicative of both high soil permeability and an arid to semi-arid desert environment. The basin is in an early geomorphological stage, and the linear structures determined the design of its drainage network according to the circulation ratio of 0.08566. area's geological structure has considerable changes in hardness, as indicated by the elongation ratio of 0.112, which would facilitate the use of water in the process of the area's sustainable development.

Precipitation strengthening behavior of Custom 455 stainless steel during tempering at 420 °C

After solid solution at 850 °C, the Custom 455 was aged at 420 °C for different times. The hardness changes were measured using a Vickers hardness tester, and the microstructure and composition of the second phase were studied using atom probe tomography (APT) and high-resolution transmission electron microscopy (HRTEM). The APT results indicate that in the early stage of aging, Cu atoms first segregate and attract Ti to form CuTi clusters; As the aging time increases, Ti atoms in CuTi clusters attract Ni and form CuTiNi clusters, resulting in a rapid increase in sample hardness; Subsequently, CuNiTi clusters grew and gradually separated into Cu-rich and NiTi-rich particles; As the aging time further increases, some NiTi-rich particles grow into rod-shaped Ni3Ti precipitates, while others have Si atoms and grow into spherical G phase particles. The orientation relationship between Cu-rich phase, Ni3Ti phase, and G phase is: [100]M//[0–11]Cu//[-12–10]Ni3Ti//[100]G, (011)M//(111)Cu//(0004)Ni3Ti//(022)G. The formation of the Cu-rich, Ni3Ti, and G phase resulted in a hardness peak of 538 HV after 16 h of aging. Subsequently, the decrease in hardness caused by the coarsening of the Cu-rich and Ni3Ti particles was offset by the newly formed G phase, resulting in a slow decrease in hardness.

Ti3C2Tx-UHMWPE Nanocomposites-Towards an Enhanced Wear-Resistance of Biomedical Implants.

There is an urgent need to enhance the mechanical and biotribological performance of polymeric materials utilized in biomedical devices such as load-bearing artificial joints, notably ultrahigh molecular weight polyethylene (UHMWPE). While two-dimensional (2D) materials like graphene, graphene oxide (GO), reduced GO, or hexagonal boron nitride (h-BN) have shown promise as reinforcement phases in polymer matrix composites (PMCs), the potential of MXenes, known for their chemical inertness, mechanical robustness, and wear-resistance, remains largely unexplored in biotribology. This study aims to address this gap by fabricating Ti3C2Tx-UHMWPE nanocomposites using compression molding. Primary objectives include enhancements in mechanical properties, biocompatibility, and biotribological performance, particularly in terms of friction and wear resistance in cobalt chromium alloy pin-on-UHMWPE disk experiments lubricated by artificial synovial fluid. Thereby, no substantial changes in the indentation hardness or the elastic modulus are observed, while the analysis of the resulting wettability and surface tension as well as indirect and direct invitro evaluation do not point towards cytotoxicity. Most importantly, Ti3C2Tx-reinforced PMCs substantially reduce friction and wear by up to 19% and 44%, respectively, which was attributed to the formation of an easy-to-shear transfer film.

Transcriptome analysis reveals regulatory mechanism of postharvest softening in kiwiberry

BackgroundKiwiberry is an emerging edible fruit with market potential owing to its advantages of small size, thin and hairless skin, and sweet taste. However, kiwiberry is highly susceptible to softening after harvest, which poses a challenge for storage and transport. To reveal the underlying cause of kiwiberry softening, it is essential to investigate the characteristics of postharvest fruit and the molecular mechanisms that affect changes in fruit firmness.ResultsMorphological observations and analysis of physical parameters showed that the skin of kiwiberry did not change markedly from the 1st to the 7th day after harvest, while the colour of the inner pericarp gradually turned yellow. By the 9th day of room temperature storage, the kiwiberries began to rot. The hardness decreased rapidly from the 1st to the 5th day postharvest, reaching the low level on the 5th day. The starch and pectin contents of kiwiberry showed a downward trend with increasing storage time. Transcriptome sequencing and weighted gene co-expression network analysis identified 29 key genes associated with the changes in the hardness of kiwiberry after harvest. Gene Ontology enrichment analysis indicated that these 29 genes are mainly involved in pectin metabolism, starch synthesis, starch decomposition, and starch metabolism. In addition, three transcription factors, AGL31, HAT14, and ALC, were identified to be strongly positively correlated with the 29 genes that affect the hardness changes of kiwiberry after harvest, and 28 of the 29 key genes were predicted to be regulated by HAT14.ConclusionsThese results reveal the changes in morphological characteristics and physiological indicators during the postharvest ripening and softening of kiwiberry stored under room temperature conditions. Transcriptome analysis identified 29 key genes and three transcription factors that affect the firmness changes of postharvest kiwiberry. The results of this study thus provide insight into the transcriptional regulatory mechanism of kiwiberry softening during storage to improve the postharvest quality.

Multi-objective development of novel egg free cakes using quinoa protein and its quality attributes

This study explores the potential of utilizing quinoa protein as an egg substitute in bakery products for customers with health, culture/religion, or dietary restrictions. Quinoa protein was prepared from quinoa seed by alkaline solubilization followed by isoelectric precipitation and drying. Four different formulations of egg-free cakes were prepared by incorporating quinoa protein in egg equivalents of 50 g (Formulation 1), 75 g (Formulation 2), 100 g (Formulation 3), and 150 g (Formulation 4). The research involved Fourier-transform infrared spectroscopy and revealed such functional properties as proximate composition, physical properties, color, texture, microstructure, and sensory characteristics for the batters and the cakes. The incorporation of different quinoa protein concentrations significantly (p < 0.05) affected all the functional properties of the batters and the cakes. Such variables as crude protein and ash increased while moisture and fat contents decreased. The baking loss went down as the share of quinoa protein went up. The structural analysis showed an increase in gumminess and chewiness accompanied by a decrease in cohesiveness and elasticity. The analysis also revealed hardness and non-uniform changes. The lightness (L*) and yellowness (b*) of the cake surface and crumb decreased while the redness (a*) increased. The cakes prepared according to Formulation 4 with the greatest share of quinoa protein had a high nutritional value with reasonable concentrations of essential amino acids in general and a high level of lysine in particular. The same sample also received the highest score for overall sensory properties. The sensory assessment proved that quinoa protein could meet consumer expectations of egg-free cakes.

Effect of Carbide Precipitation on Hardness and Wear Resistance of H13 Steel

The carbide precipitation of H13 steel and its effect on hardness and friction and wear resistance are investigated by microstructure observation, phase analysis, and mechanical property test. Results show that the tempering hardness is mainly related to the content of secondary carbides. After solution treatment in the temperature range of 1040–1070 °C, quenching and tempering, with the increase of the solution temperature, the content of secondary carbides and hardness of H13 steel in the tempering microstructure increase first and then decrease, and both reach the maximum value when the solution temperature is 1060 °C. The change of hardness is consistent with that of the content of secondary carbides. When the solution temperature is 1040 °C, the wear mass loss of the tempered H13 steel is the least, which is 4.63 mg, indicating that its wear resistance is the best, and this is caused by the presence of more undissolved carbides in the tempering microstructure. With the increase of the solution temperature, the wear mass loss increases gradually, and the wear resistance decreases, which is mainly related to the content decrease of undissolved and secondary carbides and the content increase of residual austenite.

Thermal features and its effect on the properties of AISI 4140 fabricated by conventional and extreme high-speed laser material deposition

The extreme high-speed laser material deposition (EHLA) process has the potential to enable additive manufacturing for mass production by overcoming the limitations of slow scanning speed in conventional laser material deposition (LMD) processes. Thermal features are the key factors to link process and properties. A sound understanding of process-thermal-property relationships is essential for performance control and process optimization of a deposited component. In this study, we studied the thermal characteristics within a single layer and among layers for continuous processing using the numerical method, and reveal the mechanism of microstructure and hardness changes of AISI 4140 material formed by EHLA and LMD processes through the analysis of thermal properties and temperature history results. The grain size and hardness evolution for both processes during single-layer cladding and continuous forming processes were investigated. The results revealed that the grain refinement effect in continuous LMD processing is stronger than that in EHLA process (from 30.0 μm for single layer to 3.2 μm for multi layers vs. from 18.6 μm for single layer to 2.2 μm for multi layers). Similar hardness values were obtained by LMD and EHLA processes, with mean values of 511 HV and 472 HV, respectively. The yield and tensile strengths of EHLA were superior to the conventional cast material, but inferior to those of the conventional material quenched and tempered at lower temperatures. The enhanced tensile results of EHLA process were found similar to those prepared through conventional method with quench and tempering at 600 °C.

Peri-implant Hard and Soft Tissue Changes around Nonsubmerged and Submerged Implants Under Different Loading Conditions: A Split-mouth Randomized Clinical Trial

Peri-implant Hard and Soft Tissue Changes around Nonsubmerged and Submerged Implants Under Different Loading Conditions: A Split-mouth Randomized Clinical Trial

Microstructure-thermal transport property correlation after cold/cryo rolling deformation of alloy D9

ABSTRACT Plastic deformation alters the microstructure of a material due to the formation of twins, high density of dislocations and strain-induced phases and grain refinement. Such microstructural modifications can affect thermal transport properties of a material. In this work, variation in thermal diffusivity (TD) was investigated in cold worked (CW) and cryo rolled (CR) alloy D9 (ASTM designation A771/UNS S38660), using laser flash analyser after 20–80% thickness reduction. Deformed samples were characterised using XRD and microscopy techniques for structure and microstructure modifications besides correlating with the change in hardness. Temperature dependence of thermal diffusivity was measured from room temperature up to 1273 K. Microstructural features confirmed the formation of deformation-induced martensite in CR specimen. This was accompanied by up to 172% increase in hardness in 80% CR compared to annealed specimen. The dislocation density estimated from XRD structural profile showed an increase with the percentage of deformation. For all specimens, thermal diffusivity showed an increasing trend with temperature but decreased with deformation. The reduction in thermal diffusivity was non-negligible beyond 40% thickness reduction for all deformed specimen and was substantial specifically for CR alloy D9.

Microstructural constituents in compositionally graded NiCrFeSiBC hardfacing alloy/316L SS additive manufactured deposits

Ni-Cr-Fe-Si-B-C hardfacing alloys (D50) provide excellent resistance to abrasive and adhesive wear, high temperature oxidation and corrosion. These alloys are candidate materials for hardface coatings on in-reactor components of fast breeder reactors. Conventionally these deposits are made on steels through the welding route. Due to high fluidity of the molten alloy, generation of residual stress and significant dilution of the deposit, achieving crack free deposits is often a very difficult and time consuming task. To address such issues arising out of conventional fabrication routes, compositionally graded coatings have been tried through laser additive manufacturing. A 3 layered compositionally graded deposit (D50/50D50-50SS/SS) was made on 316 L SS build plate and the phase constituents and possible correlation with micro hardness was analyzed. Uppermost D50 layer consisted of γ-Ni, γ-Ni + Ni3B and γ-Ni + Cr5B3 eutectics, CrB, Cr7C3, Cr23C6, Cr3C2 and Ni3Si precipitates. The middle layer consisted of γ-(Ni,Fe), γ-(Ni,Fe)+Cr5B3, Cr5B3, Cr3C2, Cr7C3,Cr23C6 and Ni3Si. The SS layer closest to the build plate had γ-Fe, Cr3C2 and Cr7C3 precipitates. Corresponding to the variation in microstructure a gradual change in hardness also can be seen starting from the top layer to SS build plate: 580 ± 35 HV0.1, 532 ± 17 HV0.1, 348 ± 21 HV0.1 and 230 ± 10 HV0.1, which is promising.

Effect of High-Pressure Processing Treatment on the Physicochemical Properties and Volatile Flavor of Mercenaria mercenaria Meat.

High-pressure processing (HPP) technology can significantly improve the texture and flavor of Mercenaria mercenaria. This study aimed to investigate the effect of HPP treatment with varying levels of pressure (100, 200, 300, 400, 500, and 600 MPa) and a holding time of 8 min at 20 °C on the physicochemical properties and volatile flavors of M. mercenaria. The significant changes in hardness, resilience, and water holding capacity occurred with increasing pressure (p < 0.05), resulting in improved meat quality. Scanning electron microscopy (SEM) was utilized to observe the decomposition of muscle fibers in M. mercenaria due to varying pressures, which explains the differences in texture of M. mercenaria. Different pressure treatments also had an influence on the volatile flavor of M. mercenaria, and the quantities of low-molecular-weight aldehydes (hexanal, heptanal, and nonanal) with a fishy taste decreased dramatically following 400 and 500 MPa HPP treatments. Furthermore, the level of 2-Methylbutyraldehyde, which is related to sweetness, increased significantly following 400 MPa HPP treatment. The study found that 400 MPa HPP treatment resulted in minor nutrient losses and enhanced sensory quality. The results of this study provide a theoretical basis for the application of HPP treatment to M. mercenaria.

Experiments on High-Temperature Irradiation of Li2ZrO3/MgLi2ZrO4 Ceramics by He2+ Ions

The key objective of this study is to determine the effect of interphase boundaries, the formation of which is caused by the variation of Li2ZrO3/MgLi2ZrO4 phases in lithium-containing ceramics based on lithium metazirconate, on the resistance to near-surface layer destruction processes associated with irradiation with He2+ ions. During the observation of the deformation effects that have an adverse impact on the volumetric swelling of the near-surface layers of ceramics, the thermal expansion factor caused by high-temperature irradiation was considered, simulating conditions as close as possible to the operating conditions of these materials as blankets for tritium propagation. During the studies conducted, it was established that an elevation in the contribution of MgLi2ZrO4 in the composition of ceramics leads to a rise in resistance to deformation swelling caused by structural distortions of the crystal lattice, due to a decrease in the effect of thermal expansion, alongside the presence of interphase boundaries. The established dependencies of the change in the hardness of the near-surface layer of the studied ceramics made it possible to establish the kinetics of softening caused by the deformation distortion of the crystalline structure, as well as to determine the relationship between volumetric swelling and softening (change in hardness) and a decrease in crack resistance (change in the value of resistance to single compression).

Effects of electrical and mechanical properties of Ba0.92Ca0.08Zr0.05Ti0.95O3 ceramics with lanthanum dopants

Element doping is one of the important approaches to improve the performance of lead-free piezoelectric ceramics. In this study, Ba0·92Ca0·08Zr0·05Ti0·95O3-xLa (BCZT-xLa) piezoelectric ceramics were prepared by sol–gel method. The effects of La3+ contents on the phase structure, mechanical properties, and electrical properties of BCZT-xLa ceramics were investigated. Results showed that La3+ could affect the properties of ceramics by adjusting the concentration of oxygen vacancies and microstructure. When the La3+ contents were 0.008, the ceramics showed the best performance (the maximum permittivity was 8736.27, the remnant polarisation was 9.69 μC/cm2 and the coercive field was 3.44 kV/cm). The influences of Vickers hardness on ceramics were investigated using various La3+ contents. The lattice energy and oxygen vacancies were the main factors for the change in Vickers hardness. With an increment of x, the Vickers hardness values decreased from 6.271 GPa to 1.438 GPa. This study could provide a reference for BCZT piezoelectric ceramics doped with rare earth elements.

N-[(1RS)-Camphan-2-ylidene]-4-ethoxyaniline and its reduction product as stabilizers of nitrile butadiene rubbers

Objectives. To investigate the protective efficacy of unreduced and reduced forms of the condensation product of D,L-camphor and p-ethoxyaniline in nitrile butadiene rubber formulations when compared with the conventional stabilizer N-isopropyl-N′-phenyl- p-phenylenediamine aged under laboratory and in situ climatic conditions in the tropics.Methods. The thermostabilizing effect of the condensation product of D,L-camphor and p-ethoxyaniline was evaluated by means of infrared spectroscopy using the dynamics of changes in the absorption bands of carbonyl and hydroxyl groups. The features of rubber vulcanization were studied by means of rotorless rheometry. Changes in the physical and mechanical properties of rubbers and degree of cross-linking were evaluated after thermo-oxidative aging in laboratory conditions. They also took into account the results of longterm exposure of samples in undeformed and deformed state in a tropical climate, taking into account meteorological data of the Can Gio climatic testing station.Results. It was found for the first time that condensation products of D,L-camphor and p-ethoxyaniline exhibit a stabilizing effect in formulations of rubbers based on polar nitrile butadiene rubber.Conclusions. According to the results of laboratory and in situ tests, the study established that the use of N-[(1RS,2RS)-camphan-2-yl]- 4-ethoxyaniline (reduced form) as an antifatigue agent is preferable. This is due to the presence of a mobile hydrogen atom at the nitrogen atom. The protective effect is manifested in terms of the better preservation of elastic-strength properties of rubbers with less change in hardness.

Study on the UV aging resistance of ZnO‐modified epoxy resin by experiments and MD simulation

AbstractThis study investigates the impact of zinc oxide nanoparticles on epoxy resin systems and the ultraviolet (UV) aging resistance of modified epoxy resin composites using molecular dynamics (MD) simulations and experimental methods. Initially, various epoxy resin cross‐linking models are established through MD simulations to understand the influence of different nano ZnO contents on resin modification, further validated by experiments. Subsequently, the UV radiation resistance of nano ZnO–epoxy resin composites is assessed by subjecting them to high‐intensity UV radiation equivalent to 3 years of natural environmental conditions, analyzing changes in tensile properties, impact performance, hardness, and glass transition temperature of epoxy resin before and after UV radiation exposure. The findings suggest that the addition of nano zinc oxide reduces the impact of UV radiation on epoxy resin, with optimal UV radiation resistance observed at a nano zinc oxide mass fraction of 0.3 wt%.