Applied Mechanics and Materials Vol. 931

Abstract: This study evaluates and compares the corrosion resistance of zinc coatings deposited on mild steel using three different techniques: electroplating, TREFISSOUD Company hot-dip galvanization, and conventional hot-dip galvanization. Coated and uncoated samples were characterized by electrochemical polarization, microscopic analyses (optical microscopy and SEM), and X-ray diffraction (XRD). Electrochemical results demonstrated a significant decrease in corrosion current density (Icorr) for all zinc-coated specimens compared to bare steel, confirming the protective effect of the coatings. Among the coatings, hot-dip galvanization exhibited superior performance, with the TREFISSOUD Company method achieving the lowest corrosion current and the highest polarization resistance, indicating enhanced corrosion protection. Electroplated zinc, although thinner, provided adequate resistance in moderately aggressive environments. XRD analysis revealed zinc oxide (ZnO) and iron oxide (Fe₂O₃) as the main corrosion products. Their intensity was more pronounced in galvanized coatings than in electroplated zinc. Microscopic observations confirmed uniform and adherent coatings, with hot-dip galvanization producing thicker layers and stronger adhesion than electroplating. Overall, the findings demonstrate that hot-dip galvanization, particularly the TREFISSOUD Company method, provides the best long-term protection for mild steel exposed to harsh conditions. Electroplated zinc, while less durable, remains suitable for applications where a thinner, uniform coating is required. These results highlight the importance of selecting the coating method according to specific service conditions in industrial applications such as construction, pipelines, and marine environments. This study provides a new comparative analysis between conventional and TREFISSOUD company hot-dip galvanization methods, which has not been reported previously in the literature. The results highlight the distinctive performance of the TREFISSOUD Company process in improving coating uniformity, adhesion, and corrosion resistance. This novelty contributes to a better understanding of industrial zinc coating optimization for mild steel.

Abstract: This research integrates experimental testing and Machine Learning (ML) techniques to predict the weld quality of Tungsten Inert Gas (TIG) and Shielded Metal Arc Welding (SMAW). A balanced dataset comprising weld parameters and mechanical test results including tensile strength, impact energy, and bend test outcomes was compiled for mild steel and stainless steel specimens with thickness ranging from 6mm to 10mm. Experimental results revealed that TIG welding produced superior tensile strength (up to 572 MPa) and impact energy (up to 58J) compared to SMAW. A Random Forest classifier achieved 100% accuracy in classifying weld quality as Good or Defect, while linear Regression produced tensile strength with an R2 of 0.68, Mean Absolute Error (MAE) of 17.5 MPa, and Root Mean Squared Error (RMSE) of 20.27 MPa. These results confirm the viability of ML techniques as non-destructive tools for weld quality prediction and mechanical property estimation. The framework developed in this research contributes to intelligent welding process control and supports the transition toward efficient, data driven manufacturing.

Abstract: Earth has been used as a construction material for centuries, starting with sun-dried mud and straw bricks, which had limited strength and durability. This evolved into fired clay bricks, which enabled large-scale production. However, with the building industry now accounting for 35% of global energy consumption, there is an urgent need to reduce energy use, construction costs, and reliance on nonrenewable resources—particularly in energy-scarce developing nations. This study explores Unstabilized Earth Bricks (UEBs) as a sustainable alternative, requiring 98% less energy than conventional bricks. The addition of straw as an eco-friendly additive not only addresses the disposal of 200 million tons of agricultural straw waste but also improves brick strength. Tests on 230 mm x 100 mm x 90 mm bricks with 1% and 2% straw content showed increased compressive strength, though strength declined in recycled samples. Both straw-reinforced and recycled UEBs demonstrated high durability in wire brush tests, underscoring their potential as cost-effective, sustainable building materials. However, recycled clay bricks exhibited significantly lower strength and are less suitable for structural applications.

Abstract: This study evaluates the mechanical performance of cementitious composites reinforced with fiberglass at different concentrations (0.01%, 0.025%, 0.05%, and 0.1% w/w). Specimens were prepared and cured under standardized conditions to ensure statistical reliability and reproducibility. Axial and diametral compression tests demonstrated that fiberglass concentration significantly affects mechanical strength. The optimal content of 0.05% (w/w) achieved the best results, with axial and diametral strengths of 5.24 MPa and 0.52 MPa, respectively, attributed to uniform fiber dispersion and effective load transfer within the matrix. In contrast, higher concentrations (0.1% w/w) led to strength reduction due to fiber agglomeration, compromising structural integrity. These findings highlight fiberglass’s potential as a cost-effective reinforcement material that enhances concrete’s mechanical performance and durability. Moreover, the results provide practical insights for optimizing composite formulations in sustainable construction applications and suggest future research on durability and cost-benefit analysis.

Abstract: The increasing need for eco-friendly building materials has led to research into using natural fibres as reinforcement in concrete structures. This study investigates the flexural strength of kenaf fibre-reinforced concrete (KFRC) beams using both experimental and numerical analysis. Kenaf fibres are known for their excellent tensile strength and environmental friendliness. Four beam samples (A, B, C, and D) were tested. The samples had 100mm (control), 125 mm, 150 mm, and 175 mm shear spacing, respectively. Kenaf fibre was added to samples B, C, and D to determine its effect on flexural performance at an optimal content and length. The three-point bending test was conducted to evaluate key parameters such as flexural strength and deflection. Additionally, the imaging characterisation of kenaf fibre reinforced concrete and plain concrete using micro-and nanoparticles was examined and analysed using scanning electron microscopy. A finite element model was developed using Abaqus software to simulate the flexural behaviour of KFRC beams and validate the experimental results. The beam Samples A, B, C, and D have the flexural strength of 62 MPa, 72 MPa, 68 MPa, and 55 MPa, respectively and deflection values of 23.08 mm, 19.03 mm, 21.85 mm, and 31.25 mm, respectively. When comparing the flexural strength of samples B and C to that of the control sample, the results showed that the flexural strength rose by 10% and 4.6%, respectively. The flexural strength and deflection numerical models are 94% and 90%, respectively. The efficiency of the suggested model was confirmed by the numerical simulations, which demonstrated good agreement with experimental results. The potential of kenaf fibre as a workable substitute for shear reinforcement in environmentally friendly concrete constructions is highlighted by this study.

Abstract: Indonesia lies within the Pacific Ring of Fire and is therefore prone to seismic activity. Consequently, it is important to adopt structural designs capable of resisting earthquake loads. This study evaluates high-damping rubber bearings (HDRBs) designed per SNI 1726:2019 (Chapter 12) by comparing a base-isolated design with the existing fixed-base configuration of the Mulya Medika Hospital, Samarinda. Nonlinear pushover analyses were performed in ETABS 2022 to obtain base shear, global displacement, interstory drift, P–Δ stability, and performance level. The fixed-base model produced a base shear of 4902,41 kN, while the base-isolated model produced 3753,87 kN, an absolute reduction of 23,4%. Maximum roof displacement in Y direction increased from 28,70 mm (fixed) to 42,04 mm (isolated), whereas maximum interstory drift in Y direction decreased from 27,76 mm to 10,29 mm, indicating that isolators concentrate deformation at the base while reducing relative deformation of the superstructure. Computed P–Δ stability coefficients remain below allowable limits for both models (0,0435 fixed; 0,0863 isolated), confirming negligible second-order instability. Overall, HDRBs reduce seismic demand on the superstructure and improve the structure’s performance toward Immediate Occupancy (IO).

Abstract: Climate change and rising global temperatures—up to 1.17°C over the past two decades—have intensified the need for energy-efficient building systems. The building sector contributes approximately 25% of global energy use and CO₂ emissions, with HVAC systems alone accounting for nearly 50% of a building’s total energy consumption. Despite this, limited research addresses HVAC performance optimization specific to high-occupancy spaces like theater buildings, which face unique thermal and airflow challenges. This study aims to design and evaluate a high-performance HVAC system for a theater building by analyzing thermal loads and optimizing duct sizing to enhance energy efficiency and occupant comfort. Using Panasonic’s simulation software, we conducted a comprehensive thermal load analysis across four zones of a theater facility. The results revealed peak cooling loads at 18:00 WIB, with Zone A requiring 66,882 W, Zone B 56,376 W, Zone C 62,492 W, and Zone D 34,291 W. The system was designed to maintain indoor conditions at 22°C and 65% relative humidity, with an airflow supply temperature of 12.8°C. The largest duct sizing was determined to be 90×60 in (equivalent to 79.8 in in diameter) in Zone A. The findings offer actionable insights for HVAC system design in large enclosed public spaces. By integrating detailed thermal load assessment and duct optimization, this study contributes to the development of more sustainable and energy-efficient building practices, supporting broader green building initiatives.

Abstract: Sodium borohydride (NaBH₄) has several advantages as a hydrogen storage material compared to other hydrogen storage materials, such as metal hydrides, porous carbon, or other complex compounds. These advantages include a high storage capacity, the ability to release hydrogen under mild conditions, good chemical and thermal stability, and being non-toxic and environmentally friendly. These advantages make NaBH₄ the leading choice for hydrogen storage. In some of our previous investigations, we have studied the electrochemical release of hydrogen from NaBH₄, resulting in the formation of NaBO₂. The next problem is how to recover NaBO₂ to convert it back into NaBH₄. The method developed in this study is an electrochemical method with advantages in process control and scalability. This paper aims to convert NaBO₂ back into NaBH₄ electrochemically. The electrosynthesis of NaBH₄ from NaBO₂ was carried out in a two-chamber electrochemical cell separated by a bipolar membrane. The power supply controlled the current. The current used varied from 0.5 to 2 A. The concentration of NaBH₄ formed was analyzed using the iodate titration method. The formation of NaBH₄ occurs in the cathode chamber. The concentration of NaBH₄ increases with increasing electrolysis time. In general, the reaction rate of NaBH₄ formation increases at a current of 2 A. Meanwhile, the reaction rate of NaBH₄ formation at currents of 0.5 A and 1 A is almost the same. The greater the current used, the faster the NaBO₂ reduction process in the cathode chamber. The integral analysis method calculates the reaction order by integrating the reaction rate equation. The reaction orders tested are zero order, 1^st order, and 2^nd order. The best curve-matching results are shown in the second-order reaction rate equation. At a current of 2 A, the comparison curve between the data and the equation still indicates a relatively low fit. However, the second-order reaction rate equation gives the best results. The reaction rate constant is between 0.0406 and 0.0472 L mol^-1s^-1.

Abstract: Lithium-ion batteries are the preferred choice for electric vehicles (EVs) due to their high energy density, low self-discharge, thermal stability, and long cycle life. Morphology of materials is essential in assessing the effectiveness of lithium-ion battery cathodes. One effective way to evaluate cathode quality is by examining its precursor (NMC-811) morphology using SEM. Samples were taken every 20 minutes over 2 hours, revealing that longer reaction times improve the homogeneity and semi-spherical shape of the NMC-811 precursor, with increased particle density and a reduced average diameter. NMC-811 was synthesized by a calcination process at temperatures of 450°C, 600°C, and 700°C, and sintering temperatures of 800°C and 900°C. SEM analysis revealed that higher calcination temperatures resulted in a more homogeneous particle structure, with variations in holding time having minimal impact on particle shape.