Teknomekanik

The impact of exponentially varying viscosity on magnetized tangent hyperbolic nanofluid over a nonlinear stretching sheet with PHF and PMF conditions

2025-05-09T11:57:21+00:00

This article aims to explore the characteristics of tangent hyperbolic nanofluid flow over a nonlinear exponentially stretching sheet with suction or injection embedded in a Darcy porous medium. We consider a non-Newtonian magnetohydrodynamic fluid with prescribed surface temperature and temperature-dependent viscosity, relevant to applications in aerospace, automotive and marine engineering, electronic cooling, solar-energy systems, and filtration. Given its fundamental importance, the study of prescribed exponential order heat flux (PHF) and prescribed mass flux (PMF) of hyperbolic tangent nanofluid became a key in research aimed at improving the efficiency and performance of these systems. The partial differential equations are converted into ODES by using transformation procedure. The system of transformed equations is numerically solved by Chebyshev spectral method. Graphical results illustrate the impact of key parameters on concentration, velocity, and temperature profiles, while tabulated data report the local Nusselt number, Sherwood number, and skin friction coefficient. Our results show that increasing both the power-law index and the variable-viscosity parameter reduces the fluid’s velocity while elevating its temperature and concentration. The comparative analysis confirms a high degree of agreement with previous studies. This research holds significant importance as it focuses on the extensive utilization of tangent hyperbolic nanofluids in cooling electronic components that produce substantial heat during their operation.

Evaluation and characterization of charcoal briquettes using damar binder for sustainable energy

2025-03-20T22:00:50+00:00

Palm kernel shells have great potential as biomass and renewable energy sources. Its utilization has not been maximized which is only directly burned which causes air pollution. The accumulation of solid waste in the crude palm oil processing industry negatively impacts the environment. The research aims to determine the characteristics and quality of charcoal briquettes with palm kernel shell carbonization. The main findings of this study are the calorific value, water content, volatile matter, ash content, and fixed carbon in palm kernel shell charcoal briquettes with damar binder. The experimental research method was carried out by carbonizing the raw materials of palm kernel shell briquettes, applying various concentrations of damar binder mixtures. The technical parameters of briquette making were 10 MPa pressure, 60 mesh size, and different carbonization temperatures by furnace. The calorific and proximate were empirically measured by using a bomb calorimeter. This research produced palm kernel shell charcoal briquettes with a calorific value of 30.72 MJ/kg at a carbonization temperature of 500^oC and concentration of 85%:15%, a moisture content of 5.18%, volatile matter of 32.72%, ash content of 2.81%, and fixed carbon of 57.90%. Palm kernel shell charcoal briquetting technology is potentially a recommended alternative solid fuel. Consequently, developing renewable energy that is environmentally friendly leads to achieve sustainable energy security. By utilizing waste, the negative impacts on the environment can be overcome and energy needs are also resolved.

Characteristics of sisal-epoxy composite boards with sodium chloride-treated fibers at different treatment temperatures

2025-05-24T06:52:19+00:00

The growing environmental concerns associated with synthetic fibers have led to the increased adoption of bio-fibers as reinforcements in polymer composites. Sodium chloride (NaCl) is explored as a fiber treatment agent to enhance the adhesion between fibers and the matrix. The study aims to evaluate the effects of NaCl treatment on the characteristics of sisal fiber-epoxy composite boards. A completely randomized design was applied with three factors: treatment temperature (25 °C and 100 °C), NaCl concentration (1, 3, and 5 wt%), and composite board density (0.40, 0.60, and 0.80 g/cm³). Sisal fibers were soaked in NaCl solutions for one hour, rinsed, dried, and manually blended with epoxy at a ratio of 80:20 wt%. Composite board properties were observed according to the standards of JIS-A-5908, Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). Results indicated that increasing the NaCl concentration and treatment temperature significantly improved the properties of the composite board. The optimal parameters (5wt% NaCl, 100 °C, 0.80g/cm³) yielded a modulus of elasticity of 4.59±0.26 GPa, modulus of rupture of 18.88±0.03 MPa, and internal bond strength of 3.92±0.18 MPa, representing increases of 200.32%, 130.65%, and 218.70%, respectively. Thickness swelling decreased to 2.13±0.43% (48.14%) and water absorption to 8.95±0.05% (32.25%). These findings confirm that NaCl treatment is an eco-friendly method to enhance the mechanical strength and moisture resistance of biofiber composites. It also supports the development of high-performance composite boards.

High-pressure adsorption isothermal on a novel microporous material from polyethylene terephthalate plastic waste in carbon dioxide capture applications

2025-05-09T11:58:46+00:00

Carbon capture is a vital strategy for mitigating climate change by reducing industrial CO₂ emissions. Adsorption technology using microporous material shows significant promise. However, significant challenges persist in developing cost-effective and sustainable adsorbents. This study addresses this issue by simultaneously enabling CO₂ adsorption and plastic waste utilization through activated carbon derived from polyethylene terephthalate (PET). It was evaluated under isothermal conditions (27°C, 35°C, and 45°C) at pressures up to 3500 kPa. The maximum CO₂ adsorption capacity was 0.21313 kg/kg at 27°C and 3504.39 kPa, demonstrating the effectiveness of PET-derived activated carbon in capturing CO₂. The Toth isotherm model exhibited a strong fit with experimental data, with an R² of more than 99%. The Clausius-Clapeyron equation yielded an adsorption heat of 2223.66 kJ/kg using the Toth fitting, and the Chakraborty-Saha-Koyama model yielded a heat of 2383.65 kJ/kg, confirming strong adsorption potential. These results underline PET waste as a viable precursor for sustainable carbon capture adsorbents. Furthermore, the results provide essential data for developing numerical models to optimize adsorption-based carbon capture technologies.

Microstructural and mechanical properties of 17-4PH stainless steel fabricated via material extrusion 3D printing

2025-05-17T11:55:43+00:00

This study investigates the microstructural and mechanical properties of metal 3D printing products fabricated using material extrusion technology. It focuses on the critical post-processing stages: printing, washing, and sintering. A Markforged 3D printing system and 17-4 PH stainless steel material were utilized to assess the effect of printing orientation and sintering conditions on microstructural and mechanical properties of the final product. The results demonstrate that printing orientation and sintering conditions critically govern the microstructural and mechanical properties of the final product. During sintering, the microstructure undergoes significant phase transformation and densification, while micropores and shrinkage voids emerge due to capillary stresses during binder removal. Furthermore, the mechanical properties are significantly influenced by the combined effects of printing orientation and sintering conditions. Optimizing deposition parameters (printing orientations and sintering conditions) substantially enhances the mechanical performance of the final printed product.

Durability performances of ferronickel slag aggregate and seawater concrete

2025-05-12T04:56:20+00:00

The rising demand for concrete in the building sector has resulted in the exhaustion of natural sand and freshwater supplies, leading to the pursuit of sustainable substitutes. Coastal areas have plentiful ferronickel slag (SL) and seawater (SW), which can be used to manufacture concrete. Nevertheless, the possibility of corrosion to steel reinforcement raises concerns that require further research. This investigation examines the mechanical and durability performance of concrete that incorporates SL as a partial replacement for fine aggregate and SW as a mixing component. The objective is to optimize SL content to improve compressive strength, resistance to chloride ions, and overall durability. Experimental results show that replacing 25% of the aggregate with SL yields the best combination of workability, strength, and durability, significantly enhancing compressive strength, decreasing porosity, and lessening chloride ion penetration, as evidenced by the Rapid Chloride Penetration Test (RCPT). Although seawater promotes early-age hydration and strength development, its extended use slightly diminishes compressive strength due to salt-induced micro-cracking. However, SL counters these effects, making SW–SL mixture a feasible and sustainable option for concrete production in coastal and resource-limited areas. A significant relationship between RCPT and compressive strength underscores the important role of SL in densifying the matrix and improving impermeability. The concrete mixture with 25% SL exhibits the lowest abrasion weight loss at 28 and 120 days, showing improved durability. This study highlights the potential of using SL and seawater to create eco-friendly and high-performance concrete for harsh environments.

Natural fiber substitution in glass fiber-reinforced plastics: A Tensile properties simulation

2025-02-07T08:47:43+00:00

Glass fiber-reinforced polymer composite materials, commonly used for industrial axial flow fan blades due to their high strength-to-weight ratio, are environmentally criticized for their non-biodegradability. This concern has prompted the investigation of eco-friendly alternatives, such as sisal and kenaf as natural fibers. Although they generally have lower mechanical properties than synthetic fibers, they offer advantages in terms of biodegradability, cost, and density. This study aims to evaluate the feasibility of partially substituting glass fiber with unidirectional natural fibers kenaf and sisal in a 14-layer GFRP axial fan blade through numerical simulation. The research employed a finite element method (FEM) to simulate tensile testing in accordance with ASTM D-638 standards. Several hybrid layer configurations were analyzed, focusing on the number and position of natural fiber layers replacing glass fiber, particularly the glass roving (GR) layers. The simulation investigated how these substitutions influence the overall tensile stress and elastic modulus of the composite blade structure. The findings suggest that this substitution does not significantly affect tensile characteristics but substantially improves the biodegradability of the composite, resulting in a more environmentally friendly material without compromising mechanical performance.

Design, simulation, and static testing of an eco-friendly prosthetic foot using ramie-PLA composite

2025-06-01T04:44:46+00:00

This study developed a sustainable lower-limb prosthetic prototype using biodegradable ramie fiber-reinforced PLA composite as its primary material. The design specifically addresses the needs of individuals with limb amputation while prioritizing environmental sustainability. PLA-based composites for structural biomedical applications—particularly those in lower-limb prosthetics—must meet rigorous mechanical and fatigue performance requirements under repetitive loading. This study investigates the development of a transtibial prosthetic foot prototype using a quasi-isotropic lay-up prepreg ramie-PLA composite fabricated via the hot press method. Material characterization was conducted per ASTM standards, and the design was evaluated using the Finite Element Method (FEM). The prototype underwent static testing according to ISO 22675 with a user load criterion. The laminate exhibited an ultimate tensile strength of 48.36 ± 0.95 MPa, an elastic modulus of 4.125 ± 0.25 GPa, and a flexural strength of 62.06 ± 3.43 MPa. FEM results showed that all normal and shear stresses during heel strike (17.78 MPa and 1.71 MPa) and toe-off (12.38 MPa and 5.69 MPa) phases remained below fatigue limits. Experimental static stresses were heel strike (12.72 MPa) and toe-off (20.09 MPa), both within safe operational limits. These findings highlight the structural viability and environmental sustainability of ramie-PLA composites, positioning them as a promising material for next-generation prosthetic foot development.