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During operation, brake lining material rubs against the disc to generate heat. This heat could decrease the brake lining performance, such as the friction coefficient, specific wear rate, and interface temperature of the rubbing surfaces. The resulting wear debris is environmentally harmful and poses risks to human health. Therefore, this study aimed to replace the harmful material using eggshell particles as a filler in brake lining composite and enhance tribological properties. The brake lining samples were manufactured through three stages: cold compaction, hot compaction, and post-curing. The next step is the samples were subjected to a one-hour high-temperature exposure at 200°C, 300°C, 400°C, and 500°C. The results showed that the high-temperature exposure significantly affected the specific wear rate, friction coefficient, and interface temperature between the brake lining and disc. An interesting finding was that adding calcined eggshell particles in composite could improve the tribological properties up to 400°C. However, the best material’s performance resulted when the samples got an exposure temperature of 200°C. Doi: 10.28991/ESJ-2024-08-04-03 Full Text: PDF

This study presents a comprehensive analysis using the finite element method (FEM) to examine and evaluate the behavior of fuel carrier ship structure. Sandwich panels are effective structures for use in ship structures due to their lightweight yet robust nature. Sandwich panels used in ship structures have various core shapes, such as hexagonal, circular, and square, as needed. The sandwich panel structure can be widely implemented in ship construction, for example, on the deck, hull, and bulkhead of the ship’s cabin. Hydrogen is an alternative fuel that can replace fossil fuels. In this modern era, hydrogen is high valuable energy commodity, so accidents involving carrier ships could have significant consequences. Hydrogen is produced from liquefied natural gas (LNG), so if a leak occurs, for instance, in a storage tank or fuel tank, it has the potential to lead to accidents such as fires. Corrosion is a significant concern for the maritime industry, as it can jeopardize the structural integrity of these vessels and pose substantial safety and environmental risks. In this research, FEM was utilized to model and simulate the effects of corrosion on hydrogen carrier ships when exposed to fire, considering various environmental and operational factors. Through a systematic investigation, it is aimed to gain insights into the impact of corrosion on ship structural components during fires, such as hulls and storage tanks. The result of this study will contribute to improving corrosion and fire mitigation strategies, ensuring the safety and longevity of hydrogen and LNG carrier ships, and supporting the sustainable transportation of hydrogen to meet global energy demands. No research has been conducted on the structural behavior resulting from hydrogen fires and corrosion simultaneously. To achieve this, it is assumed to use the corrosion properties of steel in heavily traveled ship routes such as the Panama Canal Zone, Barent Sea, North Sea, and Suez Canal Zone. This study utilized an approach by modeling corrosion using shell thickness in Abaqus Quasi-Static and applying boundary conditions in the form of temperature increase up to 800°C and subsequent cooling back to the initial temperature. At the maximum temperature, the most significant mid-span displacement occurred in the circular core sandwich panel, with a value of 4 mm. The axial force in the structure was inversely proportional to the mid-span displacement. In the case of the circular core sandwich panel, the axial force was 96 kN. The most resilient core type was hexagonal because it experiences the least deformation when compared to circular and square cores.

Photovoltaic solar cells, known for their high efficiency and durability, offer a promising renewable energy solution. However, they are susceptible to weather conditions, have low energy density, and require regular maintenance. Elevated operating temperatures can diminish efficiency, power output, and voltage. This study explores the incorporation of fins into PV/T system collectors using Al2O3 nanofluid, validated through 3D computational fluid dynamics (CFD) simulations and laboratory experiments conducted in Surakarta, Indonesia. The research reveals that adding fins to the system reduces PV temperature by expanding the heat transfer area from the collector to the working fluid. Working fluid Water/Al2O3, at 0.6 % concentration, exhibits the highest electrical energy conversion rates at 13.39 %. Adding fins also improves thermal performance based on the working fluid used. The use of fins concentrates the heat transfer flow in the fluid. The PV/T-Fin system has more temperature color contour distribution than the PV/T system. The direction of flow distribution is based on the geometry of the fins added to the PV/T system collector. In addition, when the viscous effect decreases, the temperature decreases towards the center of the flow. This research was validated using Mean Absolute Percentage Error (MAPE), with the most significant error observed in PV/T thermal efficiency being 13.5 %. ANOVA was used to analyze the impact of additional fins and working fluid factors on the PV/T system. The results indicate no significant difference in electrical energy conversion between adding fins and the working fluid Water/Al2O3.

Carbon-fiber-reinforced polymers (CFRPs) are a composite material popular for thin-walled structure applications because of their advantages over other materials. In this study, numerical simulation analysis based on the finite-element method to identify the tensile behavior of CFRP woven material has been carried out. The method used has been verified and validated using a benchmarking procedure with the results of previous research. Errors in the simulation results are less than 10%, indicating a valid method that can be used for further research. The stress–strain distribution of each layer, the effect of ply orientation on tensile strength, the comparison of failure criteria used, and the comparison of several types of reinforcements often used have been investigated. The results showed that the characteristics of each inner layer received tensile loading visualized in the form of stress strains. Choosing the right layer angle on CFRP woven can affect the performance and strength of the material. Failure criteria that are appropriate to specific application conditions are important. Puck criteria can be used for simple applications, which require only the analysis of the main stresses in the material. Tsai–Hill and Tsai–Wu criteria can provide more accurate predictions and are better suited for loading conditions and more complex material types. Carbon fiber has better characteristics when compared to S-glass and E-glass.

The research presented in this article consisted of analysis of the ship structural accidents at low temperatures and the effect of carbon percentage in various classifications of carbon steel, compared to the high tensile strength steel materials. The objective of this research was to fill the knowledge gap by expanding the understanding of the influence of low temperature, material, and structure on the axial compression test of tubes. The simulations as idealization of the compression test were conducted with variations in temperature, material carbon percentage, and geometry shape, using Finite Element Analysis (FEA). The results showed that at -100 °C, the material had the best ability to resist compression energy; high carbon steel had the highest strength at various carbon percentages, and the square geometry showed the best ability to absorb energy before failure.

Indonesian government are actively intensifying its efforts to achieve the ambitious target of attaining 23% renewable energy consumption for electricity supply. With Indonesia, its vast coastline and abundant wind resources, has enormous potential for developing offshore wind energy. As a result, floating offshore wind turbines (FOWTs) have become a promising solution to harness the wind energy potential in deeper waters. This paper aims to provide a comprehensive analysis of the trends and challenges associated with Floating Offshore Wind Turbines (FOWTs), especially in Indonesia. A study of existing FOWTs technologies in the world was done to compare all advantages and disadvantages and the implementation in Indonesia. Studies of floater technology based on numerical and experiments to optimization the suitable platform and also identify potential sites for wind energy generation. The last is determining transportation and installations FOWTs. The result revealed that there are 10 regions with wind speed potential exceeding 5 m/s, with three areas having the best average energy capacity potential. The FOWTs floater platform designs are suitable for the depth range of 50–80 m, namely spar, semisubmersible, and TLP. Both the logistics and installation of offshore wind turbines are influenced by various factors such as port locations, wind farm locations, and manufacturing facilities.

The paper presents finite element (FE) simulations of an unstiffened plate specimen punched by a rigid indenter, to study their fracture behaviors and energy dissipation mechanisms. Load-displacement curves from the numerical results are presented for various indenter radii i.e., 35, 50, 65, 80, and 95 mm. Moreover, the outcomes of this investigation should have relevance to estimating grounding scenarios in which the bottom sustains local penetration. The numerical analysis includes the benchmarking study that is based on experimental data to ensure that the current result has satisfactory accuracy. It is concluded that the indenter radii play an important role in the crushing resistance of the plate, especially having a significant influence on the maximum force. Compared with the 35 mm cone radii, the maximum force measured in the tests increased by 110.97 % in the 95 mm indenter radius. Furthermore, the energy absorption produced by the 95 mm cone radius has a higher value at 32.23 kJ compared to 10.1 kJ, which was obtained from a 35 mm cone radius. Discussions on the effects of indenter velocities are also included in this study.

Spar-type floating offshore wind turbine has been massively developed considering its design simplicity and stability to withstand the wave-induced motion. However, the variation of the local sea level and the readiness of supporting production facilities demand the spar design to adapt in a viable way. Considering this, the present article investigated how the slenderness (length over diameter ratio) and the roundness of cross section influence the hydrodynamic characteristics, which are the crucial parameters of floater performances. The OC3-Hywind spar-type floating platform was adapted as the reference model. The length of the reference floater was then varied with a ratio of 1.5, 2, 2.5, and 3 and the diameter was proportionally scaled to obtain constant buoyancy. The number of the sides which indicated the roundness of the cross section was varied to be 4, 6, 8, 10, 12, 14, and infinity (cylindrical shape). The analysis was conducted using potential flow theory in a boundary element method solver through an open-source code NEMOH. Initially, panel convergence was conducted and compared with the experimental results of the reference model to obtain the appropriate simulation settings before being used for the case configuration analysis. Results stated that the roundness effect with sides greater than 16 had little effect on dynamic characteristics. Meanwhile, the spar with the largest diameter was more stable against the translational motion.

Natural gas is the cleanest energy source compared to other fossil fuels. When the temperature is between −160 ºC to −164 ºC at atmospheric pressure, natural gas will be in liquid form, commonly called Liquefied Natural Gas (LNG). Currently, the demand for the availability of natural gas is increasing rapidly. However, not all countries have natural gas reserves. In this case, ships transport Liquefied Natural Gas (LNG) between continents and oceans to meet global needs. Since the Northern Sea Route (NSR) was opened, the route has become an alternative route where ships can save fuel because the distance is closer than the standard route (through the Suez Canal). However, because this route is in the Arctic region, which has a harsh environment, the ship may experience a structural failure, resulting in an accident and possibly causing material, human or other casualties. This paper employed the finite element method to observe the materials used as raw materials for the structure of natural gas shipping vessels. High tensile steel grade AH 32 was tested for tensile using numerical analysis. The temperature varied from room to shallow temperature (−160 ºC). Besides that, the mesh sizes used were 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, and 10 mm to produce outcomes that are most similar to earlier research assessed via experimental testing. The result obtained was that the mechanical properties of AH 32 steel will change significantly at shallow temperatures, which can be observed from the engineering stress–strain graph. High tensile steel grade AH 32 becomes very brittle at −160 ºC. Besides that, the necking phenomenon, as in the experimental test, can also be observed through numerical analysis.

Ocean thermal energy conversion (OTEC) is a floating platform that generates electricity from seawater heat. The cold water pipe (CWP) used in OTEC has a length of 1,000 m and a diameter of 10 m, making it susceptible to bending loads from ocean currents. To find suitable geometry and material for the CWP, the finite element method was used to model the real-world geometry. In the D/t variation, lower ratios (increased thickness) result in higher critical moments, maximum stress, strain, and displacement. D/t 50 was chosen for the CWP. In the L/D variation, the critical moment’s impact on L/D ratio was minimal, while reducing L/D (shorter pipe) increased strain, and larger L/D geometries had higher displacements. L/D 10 was selected as it balanced critical moments and reduced the number of stiffeners needed. For diameter size variation, larger diameters increased critical moment and strain, but smaller diameters (larger L/D ratios) also showed high strain due to necking at two points. A diameter of 12 m was chosen for its exceptionally high critical moment. Steel was selected as the suitable material due to its higher critical moment and maximum stress, despite its higher weight and lower maximum strain than composites. Capital shape imperfections had a minimal effect on the CWP’s structure as they were localized.

Cylindrical shell structures are ubiquitous and essential supporting structures in various engineering applications. The aim of this research work is to provide a comprehensive overview of the behavior of cylindrical shell structures under different loading conditions, including external pressure, axial compression, and bending moment. The study found that the behavior of cylindrical shells was affected by their geometry, including diameter, length, thickness, and imperfections. These factors should be carefully considered in the design and analysis of cylindrical shells. Additionally, stiffeners and sandwich structures can be applied to improve the structural performance of cylindrical shells under different loading conditions. The work also highlighted the latest research trends in the field, such as the use of advanced materials, and numerical simulations to improve the understanding and design of cylindrical shell structures. Overall, this study has provided a valuable resource for engineers and researchers working on cylindrical shell structures, helping them to design and analyze the cylindrical shell structures more efficiently and effectively.

Safety Impact resistance is defined as the ability of a material to absorb impact energy through a controlled failure mechanism. The greater the energy absorption by the crash safety structure, the greater the safety in preventing deformation of the main structure due to impact. Based on the data provided by Statista, in 2020 there were 2,395 people died in road accidents in Italy, that number is still high, so we need vehicle components that are able to protect us from the effects of collisions so that the passengers can be protected. In this study, numerical validation, mesh convergence studies, and multiple load case studies were performed to investigate crash resistance of crashworthiness structure under axial loading. Numerical validation results showed that the similarity between this study and the reference reaches 95%. A deviation of 5% occurred due to different input material properties. The results showed that the concave hexagons as filling elements had greater energy absorption capacity than conventional hollow tubes, and the more concave hexagonal structures, the better the energy absorption. Oblique compression was performed in this study, and as a result, the sample had good impact resistance at low angles and no effect at high angles like 20�. Therefore, this research aims to improve multi-cell structures for the energy absorption

Antiballistics are used as personal protective equipment required by military and police personnel. They have been mentioned frequently in recent decades due to the increasing cases of war. Several studies have reviewed the development of antiballistic technology. However, there needs to be more discussion on and systematic reviews of the current milestones of antiballistic materials, testing, and procedures. In addition, compared to other fields, antiballistic studies are rarely carried out by public researchers because research on weapons is still a sensitive topic. Researchers who want to discuss antiballistics must cooperate with the country's defense and security agencies. This article aims to present a summary on and the development of scientific research on the theoretical concept of impact, the experimental approach for ballistic tests on advanced materials, the idealization of ballistic tests in computational mechanic simulations, and milestones of technical apparatus for ballistic performance measurement, over a period of more than 500 years. Thus, this analysis makes an excellent contribution to the field of antiballistics. This article review is based on hundreds of international journals and websites that are still active and can be accounted for legally. The results show that research related to antiballistics will continue to grow yearly.

Pitting corrosion is the most common, dangerous, and destructive corrosion type in marine and offshore structures. This type of corrosion can reduce the strength of the ship plate, so investigating it using several numerical grounding scenarios is needed to determine the significant degradation of the strength of the structural plate. In this study, a finite element study was used to evaluate the influence of pitting corrosion location on the strength of the bottom plate ship in grounding simulation. This study simulated 14 scenarios using different pitting positions on the bottom plate. Finite element using explicit dynamic simulation in LS Dyna software was employed to evaluate the strength of the bottom plate on the ship. The output parameters, such as reaction force and plate deformation, were assessed to compare the grounding simulation results. The simulation indicates that the location of pitting corrosion will affect stress concentration, crack initiation, reaction force, and penetrating position when the crack nucleates. The result shows the critical position of the pit, which is located near the stress concentration ring (nearly 100 mm from the center of the plates) in the plain plates.

Composites are becoming materials of the future. Composite applications have become popular in the air as airframes in the aerospace industry to the deepest seas in the form of underwater pipes. A sandwich structure is a composite with cores with low-density material pinned by a stiff facing. In this article, the sandwich material used is a Nomex-Aramid honeycomb as the core and carbon fiber composite as the facing sandwich structure. The main goal of this study is to obtain the characteristics of the sandwich structure, Nomex-Aramid carbon fiber, and study the effect of core variation on the overall strength of the sandwich structure. Numerical simulation testing was carried out to determine the characteristics of the sandwich structure. The loadings carried out were mainly three-point bending, tensile, compression, and torsional tests. In addition, this study also compared the geometry of cores and several materials to study the effect of core properties on the overall strength of the materials. The authors used the finite element method with ABAQUS. A mesh convergence study was also conducted in this article. The results of the numerical simulation showed that the structure sandwich had a major drawback in the local strength caused by the size of the cells used. In addition, the geometric shape and type of the core material also affected the strength of the sandwich structure.

An inspection is the most important step for the manufacturers producing their cars. This ensures the seamless compatibility of each car part, as even minor errors can lead to user discomfort during operation. To achieve that goal, the utilization of inspection tools, such as a checking fixture is essential. In this research, we will study the structure analysis of a checking fixture with Ansys software. This study aims to examine the structural strength by analyzing the impact of various design variations on the overall strength outcomes. The requirement for checking fixture is that it must meet the datum tolerance of the car with value of ± 2mm. Due to that factor, a rigid checking fixture is needed for inspecting the part without experiencing significant deformation. In static loading, the result of the first variation frame has a stress of 5.71 MPa and deformation of 0.051 mm, the second variation frame has a stress of 6.16 MPa and deformation of 0.049 mm and the third variation frame has a stress of 5.63 MPa and deformation 0.042 mm. In terms of weight, the first variation structure has 2470.48 kg, the second variation structure has 2179.93 kg and the third variation structure has 2210 kg. The second variation frame has the highest stress but it has the lightest weight, and the third variation frame has lower stress and deformation but it has a heavier weight than the second variation model. The study results that the second variation model is superior because it has the lightest weight while the three designs have small stress and deformation that still satisfy the requirement of the fixture.

This article aims to investigate the structural behavior of beam–column joints subjected to axial force. The geometry used is the addition of a number of beam connections to the column, and the differences in the numbers of beams used are 1, 2, 4, and 4, denoted as V1, V2, V3, and V4, respectively.

The use of technology in everyday life is unavoidable, considering that technological advancement occurs very quickly. The current era is also known as industry 4.0. In the industry 4.0 era, there is a convergence between the industrial world and information technology. The use of modern machines in the industry makes it possible for business actors to digitize their production facilities and open up new business opportunities. One of the developments in information technology that is being widely used in its implementation is machine learning (ML) technology and its branches such as computer vision and image recognition. In this work, we propose a customized convolutional neural network-based ML model to perform image classification technique for Indonesian herb image dataset, along with the detailed review and discussion of the methods and results. In this work, we use the transfer learning method to adopt the opensource pre-trained model, namely, Xception, developed by Google.

The environment is a very important topic today as well as in the future. One source of air pollution that has the potential to harm health is the wear particles released by vehicle braking systems. If these wear particles come from hazardous materials, they could destroy human health and the environment. Based on these conditions, exploring more environmentally friendly materials to substitute hazardous materials as friction materials is necessary. In this study, brake linings were prepared from bamboo fiber and eggshell (ES) particles with various pre-treatment conditions. The composition of the material frictions consisted of phenolic resin, bamboo fiber, bamboo particles, ES particles, zinc, alumina, and graphite in the following: 35% phenolic resin, 10% graphite, 10% bamboo fiber, 10% alumina powder, 5% zinc powder, and 30% bamboo particles and ESs. This study focused on observing the mechanical and tribological behavior of friction materials when using ES particles as fillers. There are three stages to manufacturing friction material: a cold press, a hot press, and heat treatment. The optimization of the characteristics of ESs as organic brake linings was carried out using the Taguchi method and analyzed using data envelopment analysis-based ranking (DEAR). An interesting finding from this study was that when ES particles were calcined at 900°C for 120 min, the ES particle size was 200 mesh, and the ES volume fraction at 25% resulted in the most optimal brake lining performance. Calcination at 900°C for 120 min completely changed the CaCO3 phase to CaO. This study also shows that calcined ES particles have the potential to be developed as friction materials for environmentally friendly two-wheeled vehicles in the future. The produced brake linings exhibited hardness, a coefficient of friction, and specific wear rates of 92.82 HR, 0.32, and 4.43 × 10−6 mm3·N−1·m−1, respectively.

The shipping industry is the primary and most significant mode of international cargo transportation. The ship must comply with strict rules regarding reducing greenhouse gas (GHG) emissions as a dominant transportation mode. Liquified Natural Gas (LNG) is the primary alternative fuel option for several shipping companies. In essence, many studies recommend LNG as a transitional and alternative fuel because its emission characteristics are cleaner than other fossil fuels. Several previous investigations have been carried out to develop an action plan for integrating the use of LNG as a ship fuel. However, there have been few discussions on the estimation of GHG emission reduction and the economic efficiency of a representative LNG-fuelled ship. The recent progress on LNG-fuelled ships is systematically reviewed to summarize the pathways and highlight the core technological concepts, technical issues, current LNG-fuelled ship applications, and future outlooks regarding integrating LNG energy resources into ship power systems to measure GHG emission reductions and cost savings estimations. The report will discuss the current development in the maritime sector and the effects of the macroeconomic scale. The result reveals that future research on ship-based LNG energy systems will probably concentrate on integrating new energy source generating strategies with existing ship power systems to improve energy efficiency. Several potential research areas for future outlook were also discussed to anticipate future challenges.

Wind energy is the third-largest renewable energy source after hydro and solar energy, so it has great potential in increasing renewable energy as a percentage of national energy. However, wind energy installation is only at 0.25% of the existing potential; so, it still needs to be developed. One of the development efforts is to optimize the wind turbine rotor design. Savonius rotors are among the most popular rotors to convert wind energy into electrical energy. The Savonius turbine is a simple structure, easy to modify to upgrade Savonius performance, and can be operated at low velocity. Phase-shift angles of 0°, 30°, 60°, and 90° were utilized in this study on a two-stage Savonius wind turbine. This study was carried out using Solver CFX utilizing the Computational Fluid Dynamic technique on the ANSYS Student version software. An SST (shear stress transport) turbulence model with steady-state turbulence was used. The purpose of this study was to assess the influence of PSA on the performance of the Savonius two-stage turbine. Factorial design analysis was used in conjunction with the CFD approach. The results indicated that PSA influenced the Savonius turbine’s performance, with 30° being the optimal PSA. Simultaneously, the Cpmaxmay be obtained using 0.29. The factorial design study with two components revealed that the Phase-Shift Angle had a considerable effect on rotor performance, and the two factors (TSR and PSA) had an interaction.

Solar energy may be transformed into several types of energy, including electrical energy. Solar cell efficiency is low because some of the thermal energy that solar panels collect is not used. A solar panel’s relative efficiency and heat transmission decrease as it heats up. By collecting thermal energy and cooling it, photovoltaic systems may operate more efficiently. In this study, a thermal photovoltaic collector (PVT) system with a working fluid is used to cool PV panels. Laboratory-scale testing and simulation using the ANSYS Software were applied in the analysis. The simulation outcomes confirm the experimental values. Nanofluid serves as the working fluid because it has strong heat transmission qualities and has the characteristics of titanium dioxide (TiO 2). Average PV operating temperatures may be reduced by using TiO 2-based PVT systems. This can be explained by the fact that the fluid makes it easier for heat to be transferred. In comparison to PV-ground cells, photovoltaic solar cells now have a 2.11% higher efficiency. When utilizing TiO 2-based PVT systems, an average photovoltaic temperature of 58.5 °C is generated, with a 13.04% photovoltaic efficiency.