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PublicationEffect of blade number on the energy dissipation and centrifugal pump performance based on the entropy generation theory and fluid–structure interaction(Springer, 2023)Fluid–structure interactions may impact the precision and reliability of the unsteady flow and rotor deflection investigation in the centrifugal pump. The energy transfer between fluid and solid could disregard due to ignorance of fluid–structure interaction. This study numerically examines a centrifugal pump’s unsteady flow and structural characteristics under varied blade numbers. The entropy generation is computed and simulated numerically, considering the distributions of energy loss in the flow field. ANSYS Fluent and Workbench were employed to simulate the centrifugal pump. The elastic structural dynamic equation is used to predict the structure reaction. The shear stress transport k–ω turbulence model was conducted to simulate the fluid domain. The findings indicated that the head and shaft power increased with the increasing blade numbers at the hydraulic performance. The impeller with seven blades reached the maximum efficiency (78.7%), with an increase of 0.27% relative to the original model. Increasing the number of blades reduces pressure fluctuations at the pump output, and the impeller with nine blades shows a minimum value in pressure amplitude (4960.79 Pa). However, it increases the entropy generation (1.42 W/K) of the centrifugal pump. Variations in blade number affect the distribution and the fluctuation of the equivalent stress and the total deformation. The model with a nine blade exhibited minimum values of equivalent stress and total deformation with 5.74 MPa and 0.046 mm, respectively. This work may improve centrifugal pump operating stability by understanding how blade number affects pump flow and structural behavior and visualizing internal energy loss.
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PublicationPhysico-mechanical and microstructural evolution of sintered pressed geopolymer: dual effects of aging period and sintering temperature(Elsevier, 2024-08-09)Ceramics are highly valued for their exceptional thermal resistance and ability to withstand high temperatures. This study investigated the production of ceramic-like pressed geopolymer, focusing on the effects of aging period and sintering temperature. The results showed that the 7-day pressed geopolymer achieved the highest compressive (134.7 MPa) and flexural (34.9 MPa) strengths after sintering at 1000°C, with a density retention of 93.7 %, a mass loss of 7.9 %, and a thermal shrinkage of 1.4 %. Microstructural analysis at 1000°C showed a dense ceramic-like structure with nepheline formation. Phase analysis of the 7-day pressed geopolymer revealed a decrease in the amorphous phase as temperature increased, with nepheline formed at 800°C (26.0 %) and maximized at 1000°C (61.0 %). This work offers an optimal aging period and sintering temperature to maximize the mechanical strength and nepheline crystal formation, making them perfect for fire-resistant panels and precast construction products.
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PublicationEffects of heat input and preheating temperature on the microstructure and hardness of repairing the heat-affected zone of thermite welded rail head surface(UPI, 2024-09)The heat-affected zone (HAZ) of a thermite weld contains softer parts that are weak and need to be modified for best rail performance. This study examines how welding heat inputs of FCAW, and preheating temperatures affect the microstructure and hardness of its weld metal and HAZ after repairing the weak area of thermite welded rail. To improve the weak area’s microstructure and hardness without degrading the original thermite-welded rail, a groove was carved from the center of the HAZ on the rail head and filled using flux-cored arc welding. The investigation used two welding currents and preheating temperatures referred to as FCAW 1 and FCAW 2. The optical and electron microscopic characterization of the pearlite microstructure and interlamellar spacing were carried out. Additionally, micro-Vickers hardness testing is done. The typical hardness of the HAZ in FCAW 1 was 410 HV, whereas, in FCAW 2, it was 340 HV. The interlamellar spacings of HAZ in FCAW 1 and FCAW 2 are 80 and 105 nm, respectively. The faster cooling made pearlite interlamellar spacing finer. The decrease in lamellar spacing leads to an increase in hardness. For thermite welded rail head surface HAZ repair, greater heat input and preheating temperature with slow cooling rate work.
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PublicationCorrelative investigation on dielectric-mechanical-morphological characteristic for kenaf-glass-hybrid fibers reinforced epoxy composite(Semarak Ilmu Publishing, 2024)In recent years, there are many applications where synthetic fibers and natural fibers are used as reinforcing materials in composites, such as the automotive and aerospace industries, the medical industry, and the construction industry. While these hybrid fibers effectively enhance mechanical and electrical properties, research into electrical characteristics remains inadequate and is an ongoing endeavor. In this work, synthetic woven glass fibers and natural woven kenaf fibers were used to fabricate composite materials by vacuum infusion technique. The dielectric properties of three different substrates, glass fibers, kenaf fibers and glass/kenaf fibers reinforced epoxy composites were investigated at 0° orientation. The ENA Network Analyzer was used to measure dielectric properties in a wide microwave frequency range. The substrates were single-joint overlapped with an adhesive and then mechanically tested. The shear strength of the joint as a function of strain, was tested using a Shimadzu universal testing machine. Visual inspections were performed to determine the failure modes of the composites. The dielectric constant and loss factor of the glass fiber composite were the highest, while the kenaf fiber composite had the lowest value. When a small amount of glass fibers is incorporated into kenaf fibers, which is called a hybrid composite, the polarization increases and the mechanical strength also increases compared to the kenaf fiber composite. Scanning electron microscopy (SEM) of the fractured tensile tests was performed to understand the nature of the interfaces between glass, kenaf and matrix. The kenaf/matrix interface was heterogeneous but exhibited voids, resulting in low dielectric properties and mechanical strength. By inserting a small amount of glass fibers, the hybrid with kenaf fibers improve the dielectric constant by 20.7% and the dielectric loss factor by 27% compared with the kenaf fiber composite. The results also show that the composites exhibit a correlation between the dielectric properties, tensile strength, and the morphological nature of the interfaces.
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PublicationImpact of chilled air nozzle types on surface integrity in drilling of aluminum alloy 1050(Semarak Ilmu Publishing, 2024-07)Using cutting fluid in the machining process for Aluminum Alloy 1050 is advantageous as it helps mitigate the effects of temperature generated during cutting. It can shorten tool life and impair the quality of machine parts. Despite its benefits, cutting fluids has several disadvantages, such as high expenses, potential environmental harm, and user health risks. This research evaluates the effects of green cutting conditions, particularly nozzle types, on the metallurgical properties of the material. Their impacts on tool wear, X-Ray Diffractometer (XRD) pattern, Full Width at Half Maximum (FWHM), crystallite size, and hardness during the drilling process were investigated. The findings indicate that using chilled air with dual nozzles for cooling and lubrication is highly effective, resulting in less tool wear and a relatively purer crystalline structure of the material compared to other conditions. These results emphasize the importance of controlling cutting conditions, especially nozzle types, to produce high-quality parts with improved metallurgical properties.