Blount’s disease can potentially reduce the productivity of the next generation. An external fixation device, such as a hexapod, is required to manage this disease. However, a hexapod is still difficult to access at an affordable price. Gravity casting is an alternative manufacturing process that can potentially reduce the cost of a hexapod, especially its ring component. However, it might face issues related to surface quality and potential defects. Anodizing can enhance the surface protection and mechanical strength of components, but studies on the anodizing of cast surfaces remain limited. This study aims to determine the effects of current density (2, 2.5, and 3 A/dm2) and anodizing time (10, 15, and 20 minutes) on the hardness and characteristics of the oxide layer on hexapod ring surfaces made from re-cast aluminum 6061. The results indicate that anodizing at 2.5 A/dm2 for 20 minutes produces an oxide layer with the highest hardness value.
The results of experimental research on marine thermal power plants using a shell and tube heat exchanger made of copper-tin (Cu-Sn) alloy are the main focus of this study. This study uses a heat exchanger Scale Model measuring 60 mm wide x 1 meter long. The system operated using a closed cycle and Organic Rankin cycle. A simulation study has been carried out using Ansys CFD software to model new heat exchangers, namely models A and B. The interaction between ammonia and hot water produces thermodynamic values in the form of an evaporator outlet temperature of 28°C in models A and B 260C. The weakness of model B is that the turbulent flow is divided into left and right sides so that heat loss occurs in the flow corner area. The seawater inlet temperature of 29°C can heat the working fluid from the ammonia flow inlet from 5°C to 28°C, resulting in saturated steam reaching 5-6 bar.
The application of cooling towers in various industries has been widely used to meet needs. The main purpose of this study is to create an effective cooling tower in the water-cooling process by using the counter flow principle to meet the need to reduce the water temperature of the cooling system in transformers and holders of electric arc furnaces. The method used in the design and construction of the Cooling tower Mechanical draft Type Counter Flow tool includes the stages of planning, designing, making trials, and processing data. The planning stage involves gathering literature, searching for the best design, and determining the design plan. The design stage includes the design of the tool using Computer Aided Design (CAD) and the selection of materials to be used. The manufacturing stage involves assembling machine components into the desired design machine. Heat transfer analysis is also carried out to discover the heat transfer phenomenon. The test results show that the temperature data on the Thot, water cooling tower is 65,9 oC, Tcavity is 48 oC, Twater column is 28 oC, and Tcold is 26,8 oC. So that the design of the tool shows a decrease in temperature at each stage, including Tcavity is 21 oC, T water column is 20 oC, and T tank is 1,2 oC. The mini cooling tower achieved a high cooling range of 35,9 oC and a low approach of 3,2 oC. It can reduce the water temperature from the cooling process in the transformer and holder electric arc furnace. The design has released the hot water temperature from 65,9 oC to 26,8 oC. The design of the tool has succeeded in releasing heat as much as 61,4 kJ/s. Thus, the water from the cooling process can be effectively reused as a cooling medium, offering a practical and efficient solution for enhancing sustainability in small to medium-scale industrial cooling processes.
Flexible dual-fuel technology is becoming increasingly important in the marine market, where alternative fuels are receiving more attention due to increasing concerns over exhaust pollutant emissions generated by internal combustion engines, fluctuating fuel costs, crude oil depletion, and classification issuing specific rules or guidelines for propulsion systems applied to LNG carriers. Various solutions have been proposed, including the use of alternative fuels. LNG, as a fuel, has been proven and is a viable solution to replace fuel oil. Through this propulsion system technology, it can be more flexible and efficient in accommodating various shipping routes and operations. The study used Rhinoceros, Maxsurf Modeller, and Numeca Fine Marine to integrate the track plan. Calculations of speed and break BHP, and validation of speed-power predictions with HydroComp PropExpert for propeller-engine matching confirmed the selection of dual-fuel engines. Based on the gearbox configuration and LNG load capacity, a dual-fuel ME propulsion system is selected. For large loads, use high pressure, and for small loads, use low pressure with the advantages of better energy efficiency, lower initial cost, slim dimensions, and Tier III NOx standards.
A phenomenon known as the greenhouse effect happens when solar radiation is trapped and heats the planet. This effect is useful for drying agricultural materials. One of the natural sugar substitutes that is dried during production is stevia rebaudiana. This research aims to determine the effect of air flow rate in drying using a solar greenhouse dryer on the water content and drying rate of stevia leaves. The Variable of the air flow rate used are 155 cm/s, 135 cm/s, natural and will be dried for 1, 2, 3, 4, 5, and 6 hours in the Solar Dryer Greenhouse. The stevia's water content was measured with a thermogravimetric. The results showed drying stevia using the Greenhouse Solar Dryer with an air flow rate of 155 cm/s produced the best drying performance with a decrease in the water content of stevia leaves of 89.7% and the highest drying rate of 21.3 kg H2O/kg solids.
Selection and treatment of materials in the aerospace, marine, transportation, and manufacturing industries are crucial for achieving efficient configurations. Aluminum is one of the materials widely used in these industries due to its lightweight, corrosion resistance, and good electrical conductivity properties. Aluminum alloys 2024-T3 and 7075 are often used in aircraft component manufacturing due to their strength and excellent corrosion resistance. The commonly used joining method is riveting, but there are also other methods such as friction spot stir welding (FSSW). In this study, joining was performed using rivets and followed by the FSSW process on aluminum plates of types 2024 and 7075. The objective of this research is to investigate the mechanical strength of rivet joints combined with the FSSW process on plates with different types. A literature review on aluminum, alloys 2024-T3 and 7075-T6, as well as the riveting and FSSW joining methods, was also conducted. The experimental method involved joining the two types of plates using rivets and subsequently performing the FSSW process. The results of this research are expected to provide a better understanding of the mechanical strength of rivet and FSSW joints on aluminum plates with different types.
Tobacco stalk waste is an agricultural residue with high potential for development as a renewable energy source through a thermochemical conversion process. This study aims to evaluate the effect of varying pyrolysis temperature on the physical and chemical characteristics of biochar produced from tobacco stalk, in order to determine the optimum temperature for producing the best quality product. The method used was a closed pyrolysis process in a stainless-steel reactor at three temperature variations: 290, 390, and 490°C for 60 minutes. The pyrolyzed biochar was analyzed using proximate analysis, calorific value testing, and chemical functional group characterization using Fourier transform infrared spectroscopy. The results showed that higher pyrolysis temperatures consistently decreased moisture and volatile matter content, while increasing the bound carbon content and calorific value of the biochar. At 490°C, the best biochar characteristics were obtained with a bound carbon content of 56.25%, a moisture content of 4.5%, volatile matter of 24.3%, and the highest calorific value reaching 5521.90 cal/g. Chemical structure analysis also indicated the formation of more stable functional groups at higher temperatures, indicating a more advanced level of carbonization. These findings indicate that within the investigated temperature range (290–490°C), 490°C yielded the biochar with the most favorable characteristics for solid fuel applications, specifically regarding fixed carbon content and calorific value. While 490°C represents the peak performance in this study, it serves as a critical operational point for achieving advanced carbonization in tobacco stalk waste. This research provides an important contribution to the development of efficient tropical biomass processing technologies. It expands the database of thermal and chemical characteristics of agricultural waste-based biochar, which has been understudied to date.
The increasing demand for sustainable solid fuels has driven the development of biochar briquettes based on coconut shells and teak leaves with tapioca starch as a binder. This study evaluated the effect of the mixing ratio of coconut shell and teak leaf biochar (50:40, 60:30, and 70:20; 10% binder) on the physical, thermal, and mechanical properties of briquettes carbonized at 450 °C for 3 hours and characterized by moisture content, ash content, calorific value, density, and impact resistance index (IRI). The results showed that an increase in the fraction of coconut shell biochar reduced the moisture content (6.124–5.616%) and ash content (13.916–11.100%), and increased the calorific value (6050.36–6557.90 cal g⁻¹), density (14.712–16.347 kg m⁻³), and IRI (95.866–96.536%). The best composition was obtained with 70% coconut shell biochar, 20% teak leaf biochar, and 10% binder, which produced high-quality briquettes with the potential to be used as renewable solid fuel from agricultural and forestry waste.
Rear-end collisions between passenger vehicles and heavy trucks frequently result in high fatality rates due to underride events, in which the smaller vehicle slides beneath the truck. This underscores the need for improved passive safety systems, particularly the Rear Underrun Protection Device (RUPD), which serves to absorb impact energy. However, many existing RUPD designs only meet minimum regulatory requirements without optimizing energy absorption performance. This study aims to analyze and compare the influence of varying material types and structural configurations of the energy absorption box on the RUPD’s energy absorption capability. The evaluation focuses on deformation, stress distribution, and absorbed energy under impact loading conditions. The methodology involves three-dimensional modeling using SolidWorks and finite element method (FEM) simulations in Ansys. Materials including ASTM A36 steel, AISI 1020 steel, and Aluminum 2024 are combined with honeycomb structural variations. Simulations are conducted in accordance with UN ECE R.58 standards. Furthermore, the Simple Additive Weighting (SAW) method is applied to determine the optimal design. The results indicate that both material selection and structural configuration significantly affect energy absorption performance, with the honeycomb structure using filler with Aluminum 2024 demonstrating superior capability. This study contributes to the development of more effective RUPD designs aimed at enhancing road safety.
The increasing demand for reliable motorcycle braking systems requires accurate performance evaluation under controlled conditions, where a brake testing device plays an important role and its structural integrity becomes a key factor in ensuring safe and stable operation. The design and structural evaluation of a motorcycle disc brake testing device are conducted using the Finite Element Method (FEM), focusing on the main components including the frame, load actuator, and load holder under static loading conditions. The structure is constructed using ASTM A36 steel to provide adequate strength and stiffness, while mechanical components such as the electric motor, brake disc, and shaft are simplified as equivalent loads to reduce computational complexity without compromising realistic working conditions. The simulation results show that the maximum von Mises stresses on the frame, load actuator, and load holder are 42.92 MPa, 56.02 MPa, and 68.18 MPa, respectively, which are below the material yield strength of 250 MPa, with maximum displacements within acceptable limits and safety factors greater than 3, indicating that the structure is safe and reliable for operation.
Creep is a time-dependent deformation in which failure can occur in years. The probabilistic assessment was a typical method for predicting creep deformation. The prediction was conducted by extrapolating the short-time creep laboratory test to the long-time data. A small deviation of extrapolation data was expected. Hence, a large number of creep tests were needed, since deviations in material properties cannot be avoided, especially in welded materials. In this study, the creep strain rate of Gr-91 steel was compared among the base metal (BM), weld joint (WJ), and heat-affected zone (HAZ). Welded steel was manufactured by the tungsten inert gas welding method. The creep test was conducted for each of the BM, WJ, and HAZ specimens using a lever-arm-type creep machine, following ASTM E139. The homologous creep temperature was set at 570 °C for a series of constant load ranges from 250 to 160 MPa. The strain-time curves of BM, WJ, and HAZ were generated after the specimens were fractured. The trend line of the creep strain rate is then determined using Norton’s equation. The creep mechanism of BM, WJ, and HAZ was investigated based on the creep exponent and strain hardening coefficient obtained from Norton’s equation.
The change of insert chips in the CNC Turning Surface Finishing process has led to mismatched turning parameters and a deterioration in the surface roughness quality of the Ring Synchronizer Outer. As a result, it is necessary to optimize the cutting parameters to maintain surface roughness quality and improve process time efficiency. A process capability index analysis (Cp and Cpk) was conducted to ensure process stability under mass production conditions. This study adopts a quantitative and experimental research method. The research activities include calculating three CNC Turning Surface Finishing parameters, conducting CNC Turning process trials, measuring surface roughness, and calculating the Cp and Cpk values. The independent variable in this study is the feed rate (mm/rev), while the dependent variable is surface roughness, represented by the Ra (average roughness) value in micrometers (μm). The results of the CNC Turning Surface Finishing tests for the three parameters are as follows: Parameter 1 (n = 2000 rpm and f = 0.04 mm/rev) produced a Ra value of 0.284 μm (very smooth), with a cutting time of 2.44 seconds, Cp = 27.59, and Cpk = 4.90. Parameter 2 (n = 2000 rpm and f = 0.07 mm/rev) resulted in a Ra of 0.547 μm (smoother), cutting time of 1.39 seconds, Cp = 20.51, and Cpk = 7.01. Parameter 3 (n = 2000 rpm and f = 0.10 mm/rev) achieved a Ra of 0.803 μm (smooth and within standard), with a cutting time of 0.975 seconds, Cp = 20.77, and Cpk = 10.29. Based on these results, it can be concluded that Parameter 3 is the most suitable and time-efficient configuration.
The growing demand for sustainable materials has increased interest in natural fibers as eco-friendly reinforcements. Doyo fiber (Curculigo latifolia) from East Kalimantan remains insufficiently characterized despite its ecological potential. This study investigates the effect of alkali treatment concentration and immersion time on the mechanical and structural properties of doyo fibers. Fibers were treated using NaOH solutions (5–10%) and analyzed through tensile testing, Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). Untreated fibers exhibited the highest tensile strength (176.83 MPa), while moderate treatment (5% NaOH for 90 min) preserved comparable strength (171.52 MPa) with improved surface activation. Aggressive treatment (10% NaOH) reduced tensile strength below 110 MPa due to cellulose degradation. These results demonstrate that alkali treatment requires careful optimization to balance performance enhancement and structural integrity.
The performance of photovoltaic (PV) systems in tropical regions such as Indonesia is strongly influenced by the panel tilt angle, which determines the amount of solar radiation captured. An inappropriate orientation can cause substantial energy losses and reduce overall system efficiency. This study experimentally investigates the optimal tilt angle for a 100 Wp monocrystalline solar panel to maximize power generation in Cilacap, Indonesia (7.6252° S, 109.1134° E). The experiment was conducted in November 2024 under clear sky conditions, with hourly measurements of solar irradiance, and electrical power output at three tilt angles: 30°, 45°, and 60°. The results show that the 30° tilt angle consistently produced the highest performance, reaching a maximum power output of 194.5 W and an efficiency of 19.5% under peak solar irradiance of 1030 W/m² at 11:00 WIB. In contrast, the 60° configuration exhibited the lowest output, particularly during the afternoon period. It is concluded that a fixed tilt angle of 30° provides the most effective configuration for photovoltaic installations in Cilacap, aligning with the solar geometry of tropical regions.
Hydrogen production through alkaline water electrolysis is a promising pathway for clean energy generation, yet its efficiency is often limited by gas bubble accumulation on electrode surfaces. This study explores the use of a natural surfactant derived from Sapindus rarak (lerak) as a green additive to improve hydrogen evolution reaction (HER) performance. Experimental results show that the natural surfactant-enhanced system achieved a 135% increase in cumulative hydrogen yield over 10 minutes. Mechanistically, the natural surfactant lowered the surface tension, reduced bubble nucleation size, and promoted faster detachment from the electrode surface, thereby preserving catalytic activity. Compared to synthetic surfactants like sodium lauryl sulfate, Sapindus rarak offers advantages in natural degradability, environmental safety, and regional availability. This study demonstrates that natural plant-based surfactants can serve as effective, eco-friendly enhancers in electrochemical hydrogen production. The results provide a foundation for integrating natural surfactants into scalable and sustainable green hydrogen systems.
Conventional manual wheelchairs are widely used for indoor mobility; however, their operation is limited by the user’s ability to generate propulsion force, which affects travel range and the level of independence. This study presents the design and development of a portable drive system equipped with a quick-release mechanism, enabling fast installation and removal without permanent modification to the wheelchair. The proposed system employs a 120 W DC motor and a 24 V, 4.5 Ah battery. The research methods include mechanical and electrical power requirement calculations, CAD-based design, finite element analysis (FEA) for structural strength verification, and prototype fabrication. Simulation results indicate that the structure can support an 80 kg load with a safety factor of 1.23. The prototype achieves a maximum speed of approximately 15 km/h, with an operating time of about 1 hour at maximum load. The proposed quick-release portable drive system is expected to enhance user mobility and independence, thereby improving comfort and accessibility in everyday use.
This study aims to investigate the effect of the Minimum Quantity Lubrication (MQL) method using wasted cooking oil and depth of cut on surface roughness in the turning process of AISI 1020 steel. The tests were conducted on a manual lathe machine with a spindle speed of 800 rpm, a cutting length of 100 mm, and depth of cut values of 0.2 mm, 0.4 mm, and 0.6 mm. The independent variables used were MQL with wasted cooking oil and depth of cut, while the dependent variable observed was surface roughness. The test results show that the lowest surface roughness (Ra) value of 1.423 µm was obtained at a depth of cut of 0.2 mm with MQL. Conversely, the highest surface roughness value of 3.515 µm was recorded at a depth of cut of 0.6 mm without MQL. Increasing the depth of cut resulted in an increase in surface roughness. However, the application of the MQL method with wasted cooking oil can reduce surface roughness compared to the turning process without MQL. Therefore, the combination of wasted cooking oil as an MQL lubricant and optimal depth of cut can improve surface quality and support the principles of green manufacturing by utilizing wasted cooking oil, which helps reduce the environmental impact of industrial waste.
Aluminium 6061 material is often used in the shipbuilding industry, especially as a construction frame on ships. GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) are widely used in welding aluminium alloy materials. This research aims to determine and analyse the effect of V, X, and U groove variations welded using GMAW and GTAW on tensile strength of a 6061 aluminium alloy. The results of this study obtained the highest tensile stress value from the X groove GMAW welding of 149.22 MPa with a strain of 8.60%. The lowest tensile stress value was obtained from the U groove GTAW welding of 105.09 MPa with a strain of 3.18%. In general, the tensile strength value of GMAW welding is better than GTAW welding. Macro photo observations of GMAW welding show a small amount of porosity welding defects at the base of the weld, while GTAW welding shows a more amount of porosity welding defects at the base of the weld.
PT XYZ is a company engaged in manufacturing, one of the products made is a Guide Vane for Hydroelectric Power Plants. The production process is carried out based on the terms of reference that has been made. The terms of reference do not have detailed information about the work steps, so that production activities are fully charged to the machine operator which has the potential for process errors and workpiece results. The way to improve the manufacturing process is to create process planning documentation, with the aim of simplifying the work process and calculating cost estimates. Documentation is made using the EMCO process planning method. Process planning is done on CNC milling machines and lathes. The results of the process planning made resulted in four processes with a total time of 2422,68 minutes. The process time obtained results in an estimated production cost of making a directional blade of Rp. 17.753.473,37 per piece.
Rapid advancements in science and technology have increased the demand for renewable and high-performance composite materials. Sugarcane bagasse, an agricultural waste, has potential as a natural fiber reinforcement in composite materials. This study investigates the use of sugarcane bagasse fibers with epoxy and polyester resin matrices for manufacturing the handle reclining component of the Toyota Kijang Kapsul. Molds were successfully fabricated using Silicon Rubber RTV-52 with a catalyst ratio of 1:25, producing precise molds suitable for composite fabrication. Compression testing revealed that epoxy-based composites achieved an average maximum compressive load of 10,673.49 N, approximately 28% higher than polyester-based composites, which averaged 8,332.83 N. Epoxy composites also showed more consistent performance across specimens. Structural analysis using ANSYS indicated that composite handles exhibited lower deformation, higher equivalent stress, and greater safety factors d to plastic counterparts. The handle reclining parts produced from epoxy resin and sugarcane bagasse fibers with a 25:75 fiber-to-resin ratio successfully replicated the original part's appearance and demonstrated superior mechanical performance. This study contributes to the development of cost-effective, environmentally friendly composite materials with practical applications in the automotive industry.
