Mechanical Compression Tests Research Articles

Research on the Physical Properties of an Eco-Friendly Layered Geopolymer Composite

Building envelopes with natural fibers are the future of sustainable construction, combining ecology and energy efficiency. The geopolymer building envelope was reinforced with innovative composite bars and two types of natural insulation (coconut mats and flax/hemp non-woven fabrics) were used as the core material. A 10 mol sodium hydroxide solution with an aqueous sodium silicate solution was used for the alkaline activation of the geopolymers. The purpose of this study was to confirm the feasibility of producing geopolymer composites with insulating layers made of renewable materials, which would have compressive strengths like those of C25/30-grade concrete and thermal conductivity coefficients like those of lightweight concrete. This publication presents the results of physicochemical tests on the base materials (oxide (XRF) and mineral phase (XRD) analysis as well as morphology and EDS) and studies the physical (density measurements), mechanical (flexural and compressive strength tests) and insulating properties (thermal conductivity measurements) of the finished sandwich partitions. The composites achieved a flexural strength of 7 MPa, a compressive strength of up to 30 MPa and a decrease in the thermal conductivity coefficient of about 60%. The research demonstrates contribution to sustainable construction by developing geopolymer composites, offering both structural integrity and superior thermal insulation. This innovation not only reduces reliance on traditional, carbon-intensive materials but also promotes the use of eco-friendly resources, significantly lowering the carbon footprint of construction. The integration of natural fibers into geopolymer matrices addresses key environmental concerns, advancing a rapidly growing field that aligns with global efforts toward energy efficiency, waste reduction, and circular economy principles in building design.

Biocomposite Scaffolds Based on Chitosan Extraction from Shrimp Shell Waste for Cartilage Tissue Engineering Application.

Chitosan-based scaffolding possesses unique properties that make it highly suitable for tissue engineering applications. Chitosan is derived from deacetylating chitin, which is particularly abundant in the shells of crustaceans. This study aimed to extract chitosan from shrimp shell waste (Macrobrachium rosenbergii) and produce biocomposite scaffolds using the extracted chitosan for cartilage tissue engineering applications. Chitinous material from shrimp shell waste was deproteinized and deacetylated. The extracted chitosan was characterized and compared to commercial chitosan through various physicochemical analyses. The findings revealed that the extracted chitosan shares similar trends in the Fourier transform infrared spectroscopy spectrum, energy dispersive X-ray mapping, and X-ray diffraction pattern to commercial chitosan. Despite differences in the degree of deacetylation, these results underscore its comparable quality. The extracted chitosan was mixed with agarose, collagen, and gelatin to produce the blending biocomposite AG-CH-COL-GEL scaffold by freeze-drying method. Results showed AG-CH-COL-GEL scaffolds have a 3D interconnected porous structure with pore size 88-278 μm, high water uptake capacity (>90%), and degradation percentages in 21 days between 5.08% and 30.29%. Mechanical compression testing revealed that the elastic modulus of AG-CH-COL-GEL scaffolds ranged from 44.91 to 201.77 KPa. Moreover, AG-CH-COL-GEL scaffolds have shown significant potential in effectively inducing human chondrocyte proliferation and enhancing aggrecan gene expression. In conclusion, AG-CH-COL-GEL scaffolds emerge as promising candidates for cartilage tissue engineering with their optimal physical properties and excellent biocompatibility. This study highlights the potential of using waste-derived chitosan and opens new avenues for sustainable and effective tissue engineering solutions.

Investigation of the mechanical and Thermal properties of functionally graded iron aluminide

Iron aluminide is used in many industrial applications such as valve of piston; In this work, the mechanical and thermal properties of samples made of functionally graded materials (FGMs) were studied. These specimens were manufactured by powder metallurgy, consisting of different chemical composition layers of (40–50) at% aluminum. The specimens consist of: single layers (B1, B2, B3) consisting of (40, 45, and 50) at% of aluminum and the rest of iron; FGMs (double-layer) (B4, B5, B6); and FGMs (three-layer) (B7). All results of FGM were compared with its constituent layers in all tests, including the x-ray diffraction examination, and they all showed the same phases with differences in intensity (Fe3Al, FeAl, Al13Fe4, FeAl2, Fe2Al5). From the mechanical compression test, the yield point, ultimate stress, and Young’s modulus results indicated that the FGMs have an average value compared with the layer that contained them. Thermal test: FGMs have the lowest values of thermal conductivity and thermal diffusivity compared with single-layer specimens. The specific heat of FGMs has the highest value. Thermal conductivity was recorded to range from 8.08 to 6.376 W mK−1 for single and FGM specimens, respectively; thermal diffusivity from 4.6 to 0.72 mm2 S−1; and specific heat from 1.77 to 8.84 MJ/m3K.

Mechanical, Thermal, and Sound Properties of Bamboo‐Powder‐Filled Polyurethane Composites

AbstractBamboo, which is called “green gold” because of its sustainability characteristics, has many wonderful properties that make it environmentally friendly. In this study, polyurethane (PU) composites used in the automotive industry were produced by adding different amounts of bamboo powders (1, 2.5, 5, 7.5, 10 and 15%, w/v) to PU foams. In this regard, density, light and stereomicroscopic analysis, thermal conductivity, spectroscopic analysis, and mechanical (compression) test have been performed. Further, sound absorption analysis and contact angle analysis have been carried out. Optical and stereomicroscopes showed average pore sizes with range of 258–482 µm. As the bamboo powder increased, the contact angle values decreased from 129 ° to 88 °. Compression force deflection values of the samples declined from 1850 to 360 g/cm2. Similar to the mechanical properties, the thermal conductivities of the PU foams decreased. However, in regards to FT‐IR, no chemical reactions were observed between PU matrix and bamboo powder. The sound absorption test results showed that bamboo powder filled PU foams are sound absorption materials and that rigid PU foam with 2.5% (w/v) (PU‐2.5) bamboo powder sample had better sound absorption properties than the bamboo‐powder‐unfilled rigid PU foam (PU‐0), with an average sound absorption coefficient value of 0.86 at 6300 Hz and 0.71 in the range of 1600–6300 Hz.

Mechanical Assessment of Denture Polymers Processing Technologies.

Removable prostheses have seen a fundamental change recently because of advances in polymer materials, allowing improved durability and performance. Despite these advancements, notable differences still occur amongst various polymer materials and processing technologies, requiring a thorough grasp of their mechanical, physical, and therapeutic implications. The compressive strength of dentures manufactured using various technologies will be investigated. Traditional, injection molding, and additive and subtractive CAD/CAM processing techniques, all utilizing Polymethyl methacrylate (PMMA) as the main material, were used to construct complete dentures. The specimens underwent a compressive mechanical test, which reveals the differences in compressive strength. All the specimens broke under the influence of a certain force, rather than yielding through flow, as is characteristic for plastic materials. For each specimen, the maximum force (N) was recorded, as well as the breaking energy. The mean force required to break the dentures for each processing technology is as follows: 4.54 kN for traditional packing-press technique, 17.92 kN for the injection molding technique, 1.51 kN for the additive CAD/CAM dentures, and 5.9 kN for the subtractive CAD/CAM dentures. The best results were obtained in the case of the thermoplastic injection system and the worst results were recorded in the case of 3D printed samples. Another important aspect depicted is the standard deviation for each group, which reveal a relatively unstable property for the thermoplastic injected dentures. Good results here in terms of absolute property and stability of the property can be conferred to CAD/CAM milled group.

Enhancing mechanical performance in SLS-printed PA12-slate composites through amino-silane treatment of mineral waste

The SLS additive manufacturing industry enables the development of products for diverse applications with distinct properties due to its excellent surface finish and ability to create varied part geometries, but it consumes high-performance materials with high acquisition costs. An extensive quarrying of stone leads to the accumulation of mineral residues, posing environmental hazards by contaminating soil and water when disposed of in landfills. The primary objective of the study was to incorporate mineral waste into the SLS technique and investigate the influence of its addition, along with a silane-based chemical treatment, on the mechanical performance of polymer-mineral composites (PA12-slate). Additionally, the feasibility of producing a highly loaded printed prototype, employing 50 wt% of mineral waste, was examined. Samples of PA12, PA12 blended with 50 wt% slate waste, and slate waste treated with silane underwent fabrication via selective laser sintering (SLS) and subsequent mechanical characterization, including tensile, flexural, and compressive tests. Additionally, the samples underwent accelerated aging using a QUV weathering tester, followed by mechanical characterization. The geometric accuracy, stability, and processing feasibility of these formulations were evaluated through SLS-printed composite prototypes utilizing PA12_50Sla_Si. It was found that the addition of 50% of slate to the PA12 presented mechanical properties decreasing compared to the printed PA12 only. However, an increase was verified when using silane-induced mineral bonding. The incorporation of mineral agents and silane enhanced the resistance of PA12 to aging. However, after aging, both tensile and flexural strength decreased across all printed samples. Nonetheless, this study showcased the feasibility of producing complex PA12-slate waste specimens containing up to 50 wt% of mineral waste using the SLS printing technique. Therefore, SLS presents itself as a viable means of adding value to this mineral waste.

Design of magnetic kappa-carrageenan-collagen bioinks for 3D bioprinting

Bioprinting approaches are of great promise for tissue engineering applications as they allow the fabrication of constructs able to mimic native tissues’ mechanical and topographical features. Additional control over cells fate can be enhanced using stimuli-responsive materials, requiring the development of novel bioinks for this purpose. In this study, bioinks comprising κ-carrageenan, collagen, and magnetic nanoparticles were designed for 3D bioprinting applications. The characterization of this material was performed, where mechanical compressive tests yielded Young’s moduli ranging from 8.25 to 18.4 kPa. Rheological assessments also revealed the shear-thinning behavior of the bioinks and a temperature-dependent gelation. The capability of these bioinks to produce 3D constructs by extrusion bioprinting was established through the printability evaluation and the development of complex structures, supporting the viability and proliferation of mesenchymal stromal cells (MSCs). Finally, as proof-of-concept, it was observed that the secretome of bioprinted MSCs stimulated with an external magnetic field of 80 mT was able to increase the number of tubes formed by human umbilical vein endothelial cells.

Formation of Zwitterionic and Self-Healable Hydrogels via Amino-yne Click Chemistry for Development of Cellular Scaffold and Tumor Spheroid Phantom for MRI.

In situ-forming biocompatible hydrogels have great potential in various medical applications. Here, we introduce a pH-responsive, self-healable, and biocompatible hydrogel for cell scaffolds and the development of a tumor spheroid phantom for magnetic resonance imaging. The hydrogel (pMAD) was synthesized via amino-yne click chemistry between poly(2-methacryloyloxyethyl phosphorylcholine-co-2-aminoethylmethacrylamide) and dialkyne polyethylene glycol. Rheology analysis, compressive mechanical testing, and gravimetric analysis were employed to investigate the gelation time, mechanical properties, equilibrium swelling, and degradability of pMAD hydrogels. The reversible enamine and imine bond mechanisms leading to the sol-to-gel transition in acidic conditions (pH ≤ 5) were observed. The pMAD hydrogel demonstrated potential as a cellular scaffold, exhibiting high viability and NIH-3T3 fibroblast cell encapsulation under mild conditions (37 °C, pH 7.4). Additionally, the pMAD hydrogel also demonstrated the capability for in vitro magnetic resonance imaging of glioblastoma tumor spheroids based on the chemical exchange saturation transfer effect. Given its advantages, the pMAD hydrogel emerges as a promising material for diverse biomedical applications, including cell carriers, bioimaging, and therapeutic agent delivery.

3D printed hetero-layered composite scaffold with engineered superficial zone promotes osteogenic differentiation of pre-osteoblast MC3T3-E1 cells

In bone tissue engineering, a new design of composite scaffold with various compositions by incorporating both natural and synthetic cues via dual nozzle 3D printing technique could efficiently accelerate the cell differentiation to osteogenic lineage. Based on the hypothesis that a biomimetic scaffold per se can supply the vital cues to provoke bone formation, 3D printed poly(ε-caprolactone) (PCL) scaffold loaded with synthetic hydroxyapatite (HAs) decorated on graphene oxide (GO) sheets (GO@HAs), was developed. To further improve its osteogenic potential, the upper and lower layer/s of scaffolds were 3D printed using another ink containing PCL and naturally allograft HA (HAa). The FE-SEM images of the 3D printed scaffolds revealed a highly regular architecture, demonstrating the successful printability of the developed materials. The compressive mechanical test confirmed the drastic role of GO@HAs on the enhancement of Young's modulus and mechanical strength of the PCL scaffold. Moreover, existence of HAa on the upper and lower sections of scaffold interestingly improved the cellular behavior of the 3D printed scaffold without having an adverse effect on mechanical features. The experimental results indicated that such engineered scaffold significantly facilitated the cell attachment and evoked higher levels of pre-osteoblast MC3T3-E1 differentiation than PCL/GO@HAs scaffold as demonstrated by alizarin red staining, ALP activity and osteo-related gene expression. Taken together, these results indicate that such fascinating scaffold comprising both mechanical and biological cues has a high potency for inducing bone repair and also open new avenues for future advancements in the realm of bone tissue engineering exploration.

Mechanical recycling of foam from end-of-life mattresses by AIR-LAY process for the production of new mattresses with a fully circular approach

A novel method for the recycling of end-of-life mattresses foam, using an AIR-LAY process which employs a bi-component fiber as a binder for the polyurethane foam, have been developed and optimized. This method permits to obtain materials with the same density of the starting foam (25 kg/m3) and with a significantly lower density with respect to that obtainable with the rebonding process (above 70 kg/m3) that uses isocyanates to bond the foam particles. The obtained recycled foams have been tested by mechanical compression and recovery tests showing that compression values of 3.7 KPa, similar to that of the mattress foam (3.0 KPa), can be achieved using 20 % of bi-component fibers as binders and a density of 35 kg/m3. On the contrary, only 3 times stiffer and denser materials can be obtained using the rebonding technology, thus making them not suitable for application in mattresses. On the basis of the results of the optimization tests a set of mattresses containing a layer of the recycled foams have been prepared. The results of the tests on the prepared mattresses have shown that they have the same compression behavior, recovery time and durability (after 30,000 cycles of compression) of a standard mattress without the recycled layer, thus proving that a fully circular approach in the recycling of the foam of the mattresses is possible using the AIR-LAY process.

Experimental study on failure mode and fracture evolution characteristics of red shale in Kaiyang Phosphorus mining area

In order to study the failure mode and fracture evolution characteristics of red shale in Kaiyang Phosphorus mining area, conventional triaxial compression mechanical tests of red shale with different bedding dip angles were carried out by using DSTD-1000 electro-hydraulic servo rock mechanics experiment system. Based on the laboratory test results, the conventional triaxial particle flow simulation of red shale samples with different bedding dip angles was carried out using discrete element PFC2D. The results show that: (1) the failure mode of red shale is controlled by bedrock when the bedding dip angle is 0° and 60° ~ 90°. When the bedding dip angle is 15° ~ 45°, the rock failure mode is controlled by bedding. The compressive strength of rock is the minimum when the bedding dip angle is 30°and the maximum at 0°, which is about 2 times of the minimum. (2) In the failure process of red shale, the cracks with different bedding dip angles show slow growth stage, accelerated growth stage and stable stage with axial strain. The whole failure process is dominated by tensile cracks, accompanied by a few shear cracks. (3) The type of displacement field varies with the bedding dip angle: tensile failure and shear failure are the main displacement field types at 15° ~ 45°, and mixed failure is often the main mode at 60° ~ 90°and 0°. The research results provide the basis and reference for the safety control of red shale roadway.

Material-extrusion based additive manufacturing of BaTiO3 ceramics: from filament production to sintered properties

Material extrusion (MEX) of thermoplastic filaments represents one of the most widely adopted additive manufacturing (AM) technologies. Unlike vat photopolymerization and powder-bed fusion methods that require high energy sources such as UV light and lasers, this fabrication method can be adapted for the fabrication of ceramics by using ceramic loaded filaments as feedstock, yet still employing relatively cheap equipment meant for polymeric materials with little adaptation of the process parameters; this potentially enables a broader diffusion of AM ceramic components. In this work, composite filaments with various weight fractions (60 – 80 wt%) of BaTiO3 were fabricated and characterized by electron microscopy, compressive mechanical testing, rheometry and thermogravimetric analysis to ensure a smooth and reliable printing process. After optimizing the printing parameters, the dense and porous printed samples were carefully debinded and sintered to obtain dense (∼ 92 %) and defect-free ceramic bodies. The sintered samples were characterized for phase development, microstructure, and pore size distribution. Careful observations reveal a particular range of pore size (0.1 – 5 µm), which originates from the binder burn out process. The dielectric and ferroelectric properties of the fabricated samples were in good agreement with those reported in previous literature. This work provides a foundation for rapid prototyping of functional electro ceramics into reliable products with desired functional properties.

Mechanical Characteristics Testing and Parameter Optimization of Rapeseed Blanket Seedling Conveying for Transplanters

Rapeseed blanket seedling transplanters have developed rapidly due to their high efficiency and adaptability to the soil in many areas of China. However, during the transplanter’s longitudinal seedling conveying process, seedling blanket compression leads to inaccurate conveying and thus declined seedling picking performance. In this paper, a mechanical compression test was carried out on rapeseed seedling blankets. The longitudinal compression force of the rapeseed seedling blanket on a transplanter was calculated through mechanical analysis. A compression model of the rapeseed seedling blanket was established to determine how the blanket’s mechanical characteristics and the device’s structural parameters affect blanket compression. In addition, with the index of longitudinal compression Y1, the coefficient of variation in the longitudinal seedling conveying distance Y2, and the qualified-block-cutting rate Y3, the interactive influence between the seedling tray tilt angle A, the seedling blanket moisture content B, and the seedling blanket thickness C were analyzed using response surface analysis. Aiming to reduce blanket compression and enhance the accuracy of longitudinal seedling conveying and block-cutting quality, the optimized results show that the predicted optimal parameters were a 50.14° seedling tray tilt angle, a 71.86% seedling blanket moisture content, and a 22.13 mm seedling blanket thickness. Using these optimized parameters, the transplanter achieved a blanket longitudinal compression of 18.17 mm, a coefficient of variation in the longitudinal seedling conveying distance of 1.142, and a qualified-block-cutting rate of 90%. Subsequently, a validation test was performed, revealing a high degree of conformity between the optimization model and the experimental data. Thus, the predicted optimal parameters can provide significantly reduced compression and a high seedling conveying performance. The results of this study provide theoretical and empirical support for the optimized design and operation of mechanized rapeseed blanket seedling transplanting.

Enhanced Energy Absorption with Bioinspired Composite Triply Periodic Minimal Surface Gyroid Lattices Fabricated via Fused Filament Fabrication (FFF)

Bio-inspired gyroid triply periodic minimum surface (TPMS) lattice structures have been the focus of research in automotive engineering because they can absorb a lot of energy and have wider plateau ranges. The main challenge is determining the optimal energy absorption capacity and accurately capturing plastic plateau areas using finite element analysis (FEA). Using nTop’s Boolean subtraction method, this study combined walled TPMS gyroid structures with a normal TPMS gyroid lattice. This made a composite TPMS gyroid lattice (CTG) with relative densities ranging from 14% to 54%. Using ideaMaker 4.2.3 (3DRaise Pro 2) software and the fused deposition modeling (FDM) Raise3D Pro 2 3D printer to print polylactic acid (PLA) bioplastics in 1.75 mm filament made it possible to slice computer-aided design (CAD) models and fabricate 36 lattice samples precisely using a layer-by-layer technique. Shimadzu 100 kN testing equipment was utilized for the mechanical compression experiments. The finite element approach validates the results of mechanical compression testing. Further, a composite CTG was examined using a field emission scanning electron microscope (FE-SEM) before and after compression testing. The composite TPMS gyroid lattice showed potential as shock absorbers for vehicles with relative densities of 33%, 38%, and 54%. The Gibson–Ashby model showed that the composite TPMS gyroid lattice deformed mainly by bending, and the size effect was seen when the relative densities were less than 15%. The lattice’s relative density had a significant impact on its ability to absorb energy. The research also explored the use of these innovative foam-like composite TPMS gyroid lattices in high-speed crash box scenarios to potentially enhance vehicle safety and performance. The structures have tremendous potential to improve vehicle safety by acting as advanced shock absorbers, which are particularly effective at higher relative densities.

Meniscal repair with additive manufacture of bioresorbable polymer: From physicochemical characterization to implantation of 3D printed poly (L-co-D, L lactide-co-trimethylene carbonate) with autologous stem cells in rabbits.

Three-dimensional (3D) structures are actually the state-of-the-art technique to create porous scaffolds for tissue engineering. Since regeneration in cartilage tissue is limited due to intrinsic cellular properties this study aims to develop and characterize three-dimensional porous scaffolds of poly (L-co-D, L lactide-co-trimethylene carbonate), PLDLA-TMC, obtained by 3D fiber deposition technique. The PLDLA-TMC terpolymer scaffolds (70:30), were obtained and characterized by scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, thermal gravimetric analysis, compression mechanical testing and study on in vitro degradation, which showed its amorphous characteristics, cylindrical geometry, and interconnected pores. The in vitro degradation study showed significant loss of mechanical properties compatible with a decrease in molar mass, accompanied by changes in morphology. The histocompatibility association of mesenchymal stem cells from rabbit's bone marrow, and PLDLA-TMC scaffolds, were evaluated in the meniscus regeneration, proving the potential of cell culture at in vivo tissue regeneration. Nine New Zealand rabbits underwent total medial meniscectomy, yielding three treatments: implantation of the seeded PLDLA-TMC scaffold, implantation of the unseeded PLDLA-TMC and negative control (defect without any implant). After 24weeks, the results revealed the presence of fibrocartilage in the animals treated with polymer. However, the regeneration obtained with the seeded PLDLA-TMC scaffolds with mesenchymal stem cells had become intimal to mature fibrocartilaginous tissue of normal meniscus both macroscopically and histologically. This study demonstrated the effectiveness of the PLDLA-TMC scaffold in meniscus regeneration and the potential of mesenchymal stem cells in tissue engineering, without the use of growth factors. It is concluded that bioresorbable polymers represent a promising alternative for tissue regeneration.

Multiscale characterization of additively manufactured PMMA: the influence of sterilization

PurposePolymethyl methacrylate (PMMA) is a remarkable biocompatible material for bone cement and regeneration. It is also considered 3D printable but requires in-depth process–structure–properties studies. This study aims to elucidate the mechanistic effects of processing parameters and sterilization on PMMA-based implants.Design/methodology/approachThe approach comprised manufacturing samples with different raster angle orientations to capitalize on the influence of the filament alignment with the loading direction. One sample set was sterilized using an autoclave, while another was kept as a reference. The samples underwent a comprehensive characterization regimen of mechanical tension, compression and flexural testing. Thermal and microscale mechanical properties were also analyzed to explore the extent of the appreciated modifications as a function of processing conditions.FindingsThermal and microscale mechanical properties remained almost unaltered, whereas the mesoscale mechanical behavior varied from the as-printed to the after-autoclaving specimens. Although the mechanical behavior reported a pronounced dependence on the printing orientation, sterilization had minimal effects on the properties of 3D printed PMMA structures. Nonetheless, notable changes in appearance were attributed, and heat reversed as a response to thermally driven conformational rearrangements of the molecules.Originality/valueThis research further deepens the viability of 3D printed PMMA for biomedical applications, contributing to the overall comprehension of the polymer and the thermal processes associated with its implementation in biomedical applications, including personalized implants.

Characteristics of Damage to Brown Rice Kernels under Single and Continuous Mechanical Compression Conditions.

During the rice milling process, single and continuous compression occurs between brown rice and the processing parts. When the external load exceeds the yield limit of brown rice, brown rice kernels are damaged; with an increase in compression deformation or the extent of compression, the amount of damage to the kernels expands and accumulates, ultimately leading to the fracture and breakage of kernels. In order to investigate the mechanical compression damage characteristics of brown rice kernels under real-world working conditions, this study constructs an elastic-plastic compression model and a continuous damage model of brown rice kernels based on Hertz theory and continuous damage theory; the accuracy of this model is verified through experiments, and the relevant processing critical parameters are calculated. In this study, three varieties of brown rice kernels are taken as the research object, and mechanical compression tests are carried out using a texture apparatus; finally, the test data are analysed and calculated by combining them with the theoretical model to obtain the relevant critical parameters of damage. The results of the single compression crushing test of brown rice kernels showed that the maximum destructive forces Fc in the single compression of Hunan Early indica 45, Hunan Glutinous 28, and Southern Japonica 518 kernels were 134.77 ± 11.20 N, 115.64 ± 4.35 N, and 115.84 ± 5.89 N, respectively; the maximum crushing deformations αc in the single compression crushing test were 0.51 ± 0.04 mm, 0.43 ± 0.01 mm, and 0.48 ± 0.17 mm, respectively; and the critical average deformations αs of elasticity-plasticity deformation were 0.224 mm, 0.267 mm, and 0.280 mm, respectively. The results of the continuous compression crushing test of brown rice kernels showed that the critical deformations αd of successive compression damage formation were 0.224 mm, 0.267 mm, and 0.280 mm, and the deformation ratios δ of compression damage were 12.24%, 14.35%, and 12.84%. From the test results, it can be seen that the continuous application of compression load does not result in the crushing of kernels if the compression deformation is less than αd during mechanical compression. The continuous application of compressive loads can lead to fragmentation of the kernels if the compressive deformation exceeds αd; the larger the compression variant, the less compression is required for crushing. If the compression deformation exceeds αc, then a single compressive load can directly fragment the kernels. Therefore, the load employed during rice milling should be based on the variety of brown rice used in order to prevent brown rice deformation, which should be less than αd, and the maximum load should not exceed Fc. The results of this study provide a theoretical reference for the structure and parameter optimisation of a rice milling machine.

Vanillin/fungal-derived carboxy methyl chitosan/polyvinyl alcohol hydrogels prepared by freeze-thawing for wound dressing applications

In this study, we developed hydrogels using polyvinyl alcohol (PVA), vanillin (V), and a fungus-derived carboxymethyl chitosan (FC) using a freeze-thaw-based method. These hydrogels were strengthened by bonding, including Schiff's base bonding between V and FC and hydrogen bonding between PVA, FC, and V. The physiological properties of these PFCV hydrogels were characterized by FTIR, TGA, compressive mechanical testing, and rheology and water contact angle measurements. FTIR spectra confirmed the effective integration of FC and V into the PVA network. TGA results showed that FC and V enhanced the thermal stability of PFCV hydrogels. Mechanical tests showed increasing the amount of V reduced mechanical properties but did not alter the elastic character of hydrogels. SEM images displayed a well-interconnected porous structure with excellent swelling capacity. In addition, we examined biological properties using cell-based in vitro studies and performed antibacterial assessments to assess suitability for potential wound dressing applications. Prestoblue™ and live/dead cell analysis strongly supported skin fibroblast attachment and viability, DPPH assays indicated substantial antioxidant activity, and PFCV hydrogels showed enhanced antibacterial effects against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). In summary, incorporating V and FC into PVA hydrogels appears to be attractive for wound dressing applications.

Investigating the high-impact deformation behavior of induced-nano precipitation hardened in718 alloy

Superalloys are the preferred materials for modern high-rotational complex components due to their exceptional ability to maintain critical properties such as strength, oxidation/corrosion resistance, even under extreme temperatures and dynamic impacts. This study investigates the dynamic impact response of nanoprecipitation-hardened 718 alloy (NPH-718 alloy) under various loading conditions. The wrought nickel-based NPH-718 alloy was transformed into a nanostructured state through a precise heat treatment process involving controlled cooling rates (28℃∙s‒1 to 30℃∙s‒1). A mechanical compression test, leading to failure, was employed to assess the alloy's ability to withstand dynamic impacts. The compressive dynamic behavior of the alloy at high strain rates (4000 s‒1 to 7500 s‒1) and temperatures ranging from ‒180℃ to 750℃ was evaluated using a custom-built direct impact Hopkinson pressure bar apparatus. The flow data obtained for NPH-718 alloy exhibited sensitivity to thermally activated processes. Consequently, as the temperature increased at a constant high loading rate, both flow stress and adiabatic effect increased. Conversely, at a constant deformation temperature, the flow characteristics exhibited an increase as the loading rate decreased. This study establishes key trends in the flow stress, adiabatic effect, temperature, and the strain rate sensitivities of NPH-718 alloy, offering valuable insights for design and performance evaluation purposes. It underscores the significant influence of temperature and strain rate on the flow behavior of NPH-718 alloy, further solidifying its reliability in demanding applications.

Evaluation of the technical properties of reactive-MgO cements produced by solar calcination of magnesite in a fluidized bed reactor

Magnesium oxide (MgO)-based cements display very interesting technical properties and environmentally-friendly features. The novel idea investigated in this study is to synthesize MgO cements, using as raw material natural magnesite calcined in fluidized bed heated by concentrated solar energy. Calcination was performed in a lab-scale system equipped with a concentrated solar simulator, operated under different process conditions. The most reactive MgO was mixed with 3% by weight of MgCO3 (nucleation agent) and four different solutions containing magnesium acetate or chloride. The binders were hydrated in air or 20% CO2 atmosphere (accelerated carbonation conditions) until 28 days. X-ray diffraction, differential-thermal and mercury intrusion porosimetry analyses, and compressive mechanical strength tests, were performed on the hydrated systems. Solar calcination produced a highly reactive MgO. The performance of the cement pastes improved at higher curing times, and when using magnesium acetate as hydration agent, as also witnessed by the application of a kinetic model. Accelerated carbonation conditions further enhanced the mechanical properties of the cements thanks to the formation of nesquehonite, allowing to reach a mechanical strength comparable to that of ordinary Portland cements class 32.5. The achieved outcomes encourage the production of low-CO2 magnesite cements from solar calcined magnesite, boosting the green aspect of the entire process.