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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.

Due to the escalating demand for liquefied natural gas (LNG) as a low-emission and environmentally friendly energy source, ISO tank containers have emerged as an innovative solution to facilitate efficient and cost-effective mass transportation. The 40 ft ISO tank container, which encompasses a pressure vessel structure, is a versatile intermodal unit that seamlessly integrates into sea and land transportation networks. The main objective of this study is to present a comprehensive analysis for assessing the various frame design scenarios of the 40 ft ISO tank container for mini LNG carrier operation. The assessment is conducted under the provisions outlined in ASME Section VIII Division I code, which governs the design standards for boilers and pressure vessels. The finite-element analysis (FEA) scrutinizes three different structural design alternatives: frame thickness, the addition of support plates, and the addition of saddle supports, which are subjected to various loading conditions: stacking, lifting, and racking load tests. The analysis offers a comparative assessment of the safety level provided by the ASME design guidance in contrast to the FEA judgments based on ISO standards. It can be found that stacking and longitudinal load tests are more critical operational load scenarios. Increasing the frame thickness of the LNG ISO tank is more practical in increasing structural weight savings than adding more saddle supports and support plates.

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.

A novel low-cost polyurethane (PU) elastomeric material reinforced with mat-form fiberglass for alternative ship material was developed. The hand lay-up technique was used to prepare samples with glass fiber contents of 0, 7, 9, 11, and 15% by weight. Several tests, including density, tensile, and hardness tests, have been conducted to investigate the effect of fiber content on the material properties of the developed materials. The test results found that only composites with 0% (PU) and 7% (PFg-7) fiberglass had met all Lloyd’s Register criteria. PFg-7 has a density of 1,098 kg/m3, a hardness of 66.15 shore-D, a tensile strength of 21.32 MPa, and an elongation at break of 47.06%, a higher hardness, elastic modulus, and yield strength than PU. PFg-15 achieved the highest density, hardness, tensile strength, elastic modulus, and yield strength, which were 1,228 kg/m3, 68.85 shore-D, 32.13, 2,176, and 30.89 MPa, respectively. The elastic modulus and yield strength of PFg-15 were 5.6 times and 3 times higher than those of PU but PFg-15 did not meet the elongation at break criteria. PFg-9, PFg-11, and PFg-15 showed brittle properties, as indicated by relatively high hardness, elastic modulus, and yield strength compared to the results from various references.

LNG ISO tank containers are a solution for bulk liquefied natural gas (LNG) delivery to the outer islands of Indonesia that are not connected to the gas pipeline network. The design of an ISO tank frame must consider two critical parameters, strength/rigidity and weight saving, which affect the operational performance of the distribution process. The current investigation aims to numerically optimize the design of the structural frame of a 40 ft LNG ISO tank for a mini LNG carrier operation using a topology optimization framework. Two design solutions are used in the topology optimization framework: reducing the strain energy and mass retained. Mass retained was selected as the objective function to be minimized, which was assumed to be 60–80%. The proposed frame design is tested using three operational loading scenarios, including racking, lifting, and stacking tests based on the ISO 1496 standard. The convergence mesh tests were initially evaluated to obtain the appropriate mesh density in the finite element analysis (FEA). The simulation findings show that the topology optimization method of the frame design resulted in an improved design, with an increase in the strength-to-weight saving ratio. A promising result from the optimization scenario demonstrates weight savings of about 18.4–37.3%, with experienced stress below the limit criteria. It is found that decreasing mass retained causes a significant stress increase in the structural frame and ISO corner castings, especially in the stacking load. The critical recommendation in the frame design of the LNG ISO tank can be improved by eliminating the saddle support and bottom frame and increasing the thickness of the vertical frame.

This study aims to analyze the maintenance of the main propulsion fuel oil system for tugboats using both qualitative and quantitative methods. The focus is on evaluating the reliability of the system and identifying potential areas for improvement. The research employs a combination of expert interviews, industry standards, and statistical analysis to provide a comprehensive overview of the maintenance practices in place. The goal is to enhance the overall performance and longevity of the main propulsion fuel oil system in tugboats. The study uses data on the operational time, failure time and frequency, the number of vessels served, and fuel system diagrams to analyze the system's reliability. Qualitative methods such as Failure Mode and Effect Analysis (FMEA) and Fault Tree Analysis (FTA) were used, as well as quantitative methods such as Overall Equipment Effectiveness (OEE), Markovian Decision Process (MDP), and reliability methods. The study found that the FO Purifier component was the critical component with a Risk Priority Number (RPN) of 294. The average value of OEE was 47%, lower than the standard of 85%. The MDP analysis showed a probability of 0.08 for mild damage and 0.46 for moderate to severe damage under steady-state conditions. The FO Purifier component had the lowest Mean Time to Failure (MTTF) value of 1658.50 hours. The study provides a graph of the reliability function against time, and recommends maintenance actions based on the MTTF and MDP.

Along with developing high-speed craft technology, the planing hull is growing with modifications for better performance. One such technology is stepped hull, both single and double. Planing hull with steps allows the boat to run at a relatively low drag-lift ratio with lower frictional resistance due to reduced wetted area. In this study, the hull was modified with variations in the position of the double steps, which aimed to determine the effect of the first and second step positions on the total resistance, dynamic trim, and dynamic sinkage generated by computational fluid dynamics (CFD). Based on the analysis results, variations in the position of the stepped can change the hull performance. Shortening the distance between the two steps and moving both rearwards toward the transom can lower the total resistance. The dynamic trim and dynamic sinkage decreased as the position of the two steps was shifted further forward. An equation created in a non-dimensional form relates the positions of two steps to the desired results of total resistance, dynamic trim, and dynamic sinkage, namely: {(x1-x2)/L + (x1x2)/(LB)} × Fr∇, where x1 is distance the first step from transom, x2 is the distance of the second step, L is the length of the boat, B is the beam of the boat, and Fr∇ is the volume Froude number.

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.

Investigation of hydrodynamic interaction between the vessel and the seabed when entering shallow water is considered one of the most critical considerations of inland waterway transport. There are many investigations into the behavior of ships in restricted waters, such as ships traveling in different forms of canal cross-sections. The present study aims to evaluate the hydrodynamic interaction of the 750 DWT Perintis Ship moving through the different canal types to determine the relative effects of limiting the width and depth cross section on the ship's resistance. Two different canals with different cross sections, including canal bank and rectangular canal, were evaluated to investigate the influence of canal width (Wb), depth ratio (hw/T), and blockage ratio function (As/Ac). The Computational Fluid Dynamic (CFD) method with Reynolds-averaged Navier–Stokes (RANS) solver and turbulent model 𝑘−𝜀 were used to predict the total resistance of the ship. The proposed numerical simulation was initially validated with an experimental towing tank test in the error range of 0.11-7.74%. The results indicated similar phenomena were found both in rectangular and canal banks. The case with a shallower (lower hw/T) and a narrower (lower Bc/Bs) canal dimension has a higher resistance value. Backflow and subsidence of free surface became significant around the ship's hull in more restricted water, changing the ship's hydrodynamic characteristics and increasing resistance. It can be found that the higher the blockage ratio (mb), the higher the total resistance value in both canal types, which proved that ships with higher speeds were more sensitive to changes in waterway restrictions.

The need for wood in the ship building industry continues to grow every year. An alternative raw material is needed to replace wood at a more affordable price, namely, bamboo laminated boards. However, bamboo has a weak connection between its segments, with a maximum length between components of less than 40 cm. To reduce these weaknesses, the connection between bamboo segments with laminated boards is carried out as follows: scarf joint, butt joint, finger joint, desk joint, and tongue and groove joint. The study aims to determine the connection’s effect on each connection variation’s strength. Tensile tests and bending tests were carried out on the test specimens. The average results obtained were quite varied for the tensile test, which were in the range of 81.36–118.62 MPa, while the results of buckling test were in the range of 395.28–475.89 MPa. This study revealed that the connection of the specimen with seven layers had a value of 118.62 MPa in the tensile strength test and 475.89 MPa in the buckling strength test, while 3 layers finger joint samples with the lowest buckling tensile strength value had a value of 81.36 MPa tensile strength and 395.28 MPa bending strength.

With the increased emphasis on the use of recyclable bio-based materials and further understanding of the mechanical properties of laminated bamboo, the development of a new generation of low-cost bamboo-based composites for ship structure has generated a significant interest. Laminated bamboo composites comprising Apus bamboo (Gigantochloa apus) and Waru fiber at different layer orientations were investigated to obtain the mechanical characteristics. The influence of different laminate directions was studied through several methods of mechanical testing, including impact tests using ASTM D256, bending tests using ASTM D7264, and tensile tests using ASTM D3039. Results showed that material strength properties could be improved by using on-axis direction (0°). The bamboo composites with unidirectional (0°) laminate direction exhibited superior mechanical properties to bidirectional laminate directions (45°/−45° and 0°/90°). The addition of Waru fiber improved the mechanical properties of the currently developed material; that is, bending strength increased by about 3.17–14.18% and tensile strength was in the range of 4.88–20.28%. Only those composites with 0° and 0°/90° layer orientations fulfilled the Indonesian Bureau Classification strength threshold.

With the increased emphasis on the need to use recyclable bio-based materials and a better understanding of the mechanical properties of laminated bamboo, there is currently a great deal of interest in developing a new generation of low-cost bamboo-based composites for use in fishing vessels. Laminated bamboo composites (LBCs) comprised of Apus bamboo (Gigantochloa apus) and fibreglass mats were investigated to obtain the mechanical characteristics. The LBC with 45°/−45° cross-fibre directions combined with chopped strand mat fibreglass was developed under different layers and mass fractions with the same composite thickness. The influence of different numbers of laminated bamboo layers (3–7 layers) on several mechanical testings, including impact tests using ASTM D256, bending tests using ASTM D7264, tensile tests using ASTM D3039, V-notched beam test using ASTM D7078, and lap shear tests using ASTM D5868 standard, were carried out. The result showed that the strategy in improving the strength properties of LBCs could be achieved by using a thinner bamboo lamina with a higher number of bamboo layers. It was found that bamboo composites with 7 layers with a higher epoxy mass matrix had superior mechanical properties than those with 3 and 5 layers at the same thickness. Another finding revealed that adding fibreglass mat to current LBCs improved mechanical properties compared to previous research, explicitly bending strength increased by about 4.02–7.56% and tensile strength in the range of 12.44–17.73%. It can be found that only specimen with 7 layers fulfils the Indonesian Bureau Classification’s bending and tensile strength threshold.

The development of the global economy has led to a rise in ship traffic. As a result, the risk of accidents, such as collisions between ships and grounding, has also increased. Different failure criteria to capture these accidents have been introduced by researchers. Therefore, the purpose of this study was to determine the essential distinction between these failure criteria. The simulations suggest that failure criteria based on the maximum stress result in a slightly higher rupture strain value, greater crack propagation, and higher internal energy than those based on the maximum strain. Furthermore, using a larger mesh size compared with the size of the test specimen appears to greatly affect the validity of the simulation results.

Energy-saving and emission reduction are crucial since shipping activity due to the global maritime trade has increased exponentially. Several agreements have been engaged to optimize ship energy efficiency composed of ship design and shipping operation planning. However, most up-to-date studies focused on speed and route optimization. The interaction analysis between speed and route efficiency below varied environmental conditions is limited. To attain energy and cost efficiency, a study of cavitation on the propeller that considers the ocean environmental condition will be discussed in this work. Although researchers have previously observed cavitation phenomena, the predictability of simulations is not yet such that problems can be eliminated. Since the multiphase flow of water and vapor is sensitive to environmental conditions, it leads to varying observation accuracy. Thus, the current paper proposes a new performance indicator of the ship propeller under cavitation predicted by computational fluid dynamics (CFD). CFD-based simulation to observe the propeller cavitation was used to model the Zwart cavitation and Kunz cavitation models under two turbulence models of K−ε at different flow conditions and operating environments. Initial validation tests between experimental and numerical simulation show good agreement with a mean error of 4.7% in the Zwart model and 3.7% in the Kunz model, where the k−ε turbulence model provides an almost higher relative error. It is revealed from the result that the increase in temperature causes the rise in the cavitation problem. It is revealed from the result that the increase of temperature causes the increase in cavitation problem.

The thermal expansion can lead to the high stress on the pipe. The problem can be overcome using expansion loops in a certain length depending on the material’s elastic modulus, diameter, the amount of expansion, and the pipe’s allowable stresses. Currently, there is no exact definition for the dimension of expansion loops design both for loop width (W) and loop footing height (H) sizes. In this study, expansion loops were investigated with using ratio of width and height (W/H) variations to understand pipe stress occurring on the expansion loops and the expansion loops’ safety factor. Relationship between non dimensional stress on the expansion loop pipe was studied numerically by finite element software on several working temperatures of 400oF, 500oF, 600oF, and 700oF. It can be found that stress occurring on the pipes increases as the increases of W/H of the expansion loops and results in a lower safety factor. The safety factor of the expansion loops pipe has a value of 1 when the ratio of loop width and loop footing height (W/H) value was 1.2 for a 16-inch diameter pipe. Stress occurring on the pipe increases with the increase of the working temperature. Expansion loops pipe designed for 400oF can still work well to handle thermal extension pipe occurring on 500oF.

Thin-walled structures, which generally consist of unstiffened and stiffened plates, are widely used in engineering as one of the core features of any product or construction. Due to environmental conditions and working operation, the components of the structure unavoidably become subject to various types of loading. Deformation patterns and overall behaviour are expected to be varied, as different materials are considered in the structures. In this situation, assessments are required to quantify the responses and determine the relationships between the structural behaviour and structural parameters. In this work, we attempt to obtain the behaviour data of unstiffened and stiffened plates as components of thin-walled structures. The material class – i.e. low- and medium-carbon steels – and loading parameters (i.e. type and angle) are taken as the main inputs in the finite element analysis. A geometrical design is adopted based on the side hull structure of a medium-sized tanker, for which two plate types, unstiffened and stiffened, are used. The results indicate that increasing the loading angle reduces the force experienced by the plate, while the greater the loading direction angle is, the greater the total displacement value will be. In terms of the plate design, the stiffener is observed to reduce the force expansion during the loading of the stiffened plate.

The assessment of a ship's ability to withstand environmental loads is very crucial. This research focuses on the strength assessment of 600 TEU container ship hulls against hydrostatic and hydrodynamic loads using finite element-based software. Parameter changes in the material types, hull thickness, and ship drafts were performed to compare the structural responses using deformation, strain, and von Mises stress criteria. All of the materials tested were acceptable, where the ASTM A131 Grade AH36 and ASTM A131 Grade AH32 materials have the lowest deformation values and strains. The simulation results regarding plate thickness variation, deformation, strain, and von Mises stress values were smaller as the thickness of the ship structure increased. Moreover, from the draft variation, the structural response due to environmental load was better as the draft of the ship increased.

This work aims to investigate the mechanical behavior of steel-plated structures under a raking incident and to quantify the effect of the mesh size in nonlinear finite element (NLFE) analysis. To conveniently comprehend nonlinear phenomena, i.e., the grounding which takes place in this work, a series of theoretical contact formulations was defined. In the main analysis, raking, which is a part of the grounding scenario, was strictly assumed as contact between a tanker, which was assumed to have thin-walled steel, and a seabed rock in the form of a solid obstruction. Designed raking scenarios were calculated using the FE method by using the nonlinear phenomena of the material behavior in the calculation. The findings of this work indicated that the possibility of expanding the recommended mesh size in FE simulation should be evaluated by quantifying the behavior of structural responses, such as energy, the force damage pattern, and acceleration, subjected to a variety of applied meshing techniques. The results concluded that a notable difference occurred when the mesh size was more than 132 mm (ratio 11 based on the plate dimension in this work), and this size is strictly recommended to be used for calculation of the element length-to-thickness (ELT) ratio. Assessment in time simulation showed that applying larger mesh sizes will reduce the simulation time but increase the maximum values of the crashworthiness parameters, i.e., energy, force, acceleration, and displacement.

As one of the most dangerous defects in the sandwich panel, debonding could significantly degrade load carrying capacity and affect dynamic behaviour. The present work dealt with debonding detection of the rectangular clamped hybrid sandwich plate by using ABAQUS software. The influence of various damage ratios on the linear and nonlinear dynamic responses has been studied. The finite element model was initially validated by comparing the modal response with the experimental test. Rectangular debonding was detected by comparing dynamic responses of free and forced vibrations between intact and debonded models. A wide range of driving frequency excitation corresponding to transient and harmonic concentrated loads was implemented to highlight nonlinear behaviour in the intermittent contact in the debonded models. The results showed that debonding existence contributed to the natural frequency reduction and modes shape change. The numerical results revealed that debonding affected both the steady-state and impulse responses of the debonded models. Using the obtained responses, it was detected that the contact in the debonded region altered the dynamic global response of the debonded models. The finding provided the potential debonding diagnostic in ship structure using vibration-based structural health monitoring.

As one of the coastal structures, breakwaters are built to protect the coastal area against waves. The current application of breakwaters is usually conventional breakwaters, such as the rubble mound type. Climate change, which causes tidal variations, sea level height, and unsuitable soil conditions that cause large structural loads, can be solved more economically by employing floating breakwater. In this study, numerical simulations will be conducted by exploring the optimum floating breakwater notched shapes from the Christensen experiment. The comparison of three proposed floating breakwater models, such as square notch (SQ), circular notch (CN), and triangular notch (VN), is compared with standard pontoon (RG) to optimize the transmission coefficient value is analyzed. Numerical simulations are conducted using Computational Fluid Dynamics (CFD) based on the VOF method with Flow 3D Software. Compared to the experimental study, the RG model's validation shows a good result with an error rate of 8.5%. The comparative results of the floating breakwater models are found that the smaller the transmission coefficient value, the more optimal the model. The SQ structure has the smallest transmission coefficient of 0.6248. It can be summarized that the SQ model is the most optimal floating breakwater structure.

The blade is the most critical part of turbine design because it is used to convert kinetic to mechanical energy. In general, the blade types used for ocean wind turbines are taper and taperless blades, like those operated at Ciheras Coastline. Previous research has been analyzed the type of airfoil used in designing taper blades for ocean wind turbines using NACA 4412, which was selected as the optimal foil configuration at sea wind speeds of 12 m/s. In this study, the comparison of taper and taperless blade designs using NACA 4412 at a wind speed of 12 m/s is analyzed. The comparative study with previous research has been carried out and resulted in the same graphical patterns and performance results. In this study, the focus is on investigating the performance coefficient of power, mechanical power, and electrical power. The final result shows that taper blade designs are highly recommended for use in ocean wind turbines compared to taperless blades. In general, the performance produced by taper blades is more significant than taperless blades at relatively high wind speeds. The maximum performance coefficient of power, mechanical power, and electrical power generated by the taper blades in sequent are 0.47, 1535 watts, and 786 watts, while the taperless blades have 0.44, 1437 watts, and 736 watts.

The conversion of Landing Craft Tank into Livestock Carrier as an alternative solution was conducted by performing technical and economic assessments. The conversion analysis of LCT vessels to Livestock Carrier was achieved by performing layout rearrangement, stability test, seakeeping, and resistance test to measure the technical change occurring due to the modification. The economic added-value analysis was conducted by calculating the payback period to determine the estimated time needed to recover the cost of an investment. The result showed that the conversion of LCT ships has a good technical assessment. The intact and damage stability performance qualifies the standard criteria given by the IMO standard. The motion result qualifies the standard according to the type of vessel in terms of heave, pitch, and roll motions. Moreover, the resistance of the Livestock Carrier is reduced due to a decrease in displacement and draft. In terms of economic assessment, the Livestock Carrier conversion project qualifies for investment projects and improves the use-value and economy of a business segment.

SATISFACTION LEVEL ANALYSIS OF AUTOCAD ONLINE TRAINING PARTICIPANTS FOR COMMUNITY SERVICE AFFECTED BY COVID-19 USING KIRKPATRICK LEVEL I METHOD. Online AutoCAD training is an activity to learn modelling techniques using AutoCAD software for participants affected by Covid-19. Online AutoCAD training was held to increase people's productivity during the pandemic, increase knowledge, and develop modelling ability using AutoCAD software. The number of participants registered to join this program was 49 participants from open recruitment which consisted of 59% male participants and 41% female participants. The program ran for four meetings online, each session 1.5 hours with a system of introduction, learning, assignments, and exams. The service team also provides free facilitators, facilities, presenters and materials (F2PM) for training participants. So, to find out participants' satisfaction, it is necessary to conduct an evaluation at the end of the training. The review was carried out by means of an online survey to the participants, then processed qualitatively with the Kirkpatrick Level I method. The final result of the participant evaluation of the facilitator was considered acceptable (59%), the facilities were considered excellent (67%), the presenters were considered very good (56 %), and the material is considered very good (59%). In the future, evaluation data on the level of participant satisfaction can be used as a recommendation and motivation to organize advanced training.

Indonesia is the largest archipelagic country and has the potential to become the world’s maritime axis. Two-thirds of Indonesia’s territory is ocean, with a total coastline of 54,716 km. Therefore, Indonesia must have solid systems and tools to overcome the various threats in the maritime sector. One of the technologies that can be developed to protect Indonesia’s naval territory is fast patrol boats. Indonesia requires efficient patrol boats that can optimally monitor the large Indonesian sea area and various potential threats in the maritime sector. Thus, research on the hydrodynamic criteria for the hull design of patrol boats is fundamental. In this study, we aimed to evaluate the design method based on hydrodynamic characteristics to obtain the primary dimensions and shape of the ship’s hull. We designed and analysed 11 ship models in terms of the following criteria: the resistance, stability, and seakeeping performance. The 11 models included five reference models of patrol boats with varying dimensions and block coefficients between 0.42 and 0.53, three ship models with the regression method with the exact dimensions and block coefficients between 0.45 and 0.46, and three ship models with the scale method with the exact measurements and block coefficients between 0.43 and 0.45. According to the analysis results, the regression method had better total hydrodynamic criteria and greater similarity to the reference vessel. With a shorter processing time, the regression method was more efficient than the scaling method and reference ship.

Underwater welding has proven to be a successful method of joining two similar or dissimilar metals and takes place underwater. This technique is frequently used for maintenance purposes, such as repairing piping systems, ships, and other marine structures. This study investigates the effect of different water flow types on an underwater weld’s physical and mechanical properties of welded bead on the A36 steel plate. The SMAW method with an E7018 electrode is used for welding A36 steel in saltwater. In this simulation, underwater welding is performed using three types of flow (without flow, non-uniform flow with a baffle plate, and non-uniform flow without a baffle plate) to compare metallography, hardness, tensile, impact, and bending testing results. The findings revealed that the saltwater flow caused more porosity defects. Moreover, the highest penetration depth was observed in specimens with the non-uniform flow with a baffle plate. The heat energy is concentrated due to droplets accumulating in the weld area. The microstructure of welding metals such as acicular ferrite and ferrite with the second phase grows as the water flow becomes non-uniform. Furthermore, as the rate and variability of the water flow increased, the value of the mechanical properties of the specimens increased relatively.

The impact attenuator is a safety vehicle system designed to absorb the kinetic energy from a collision that is converted into deformation and ensures the deceleration level acting on the human body remains low. In this paper, we propose that the impact attenuator be fabricated with used cans, which are easy to obtain. Compared to fabricating cylinders through machining and other production processes using new material, the application of used cans may reduce production costs by approximately IDR 500,000 (USD 34.50) for one attenuator structure, while the attenuator still meets the weight criterion, i.e., it has to be light to improve acceleration and fuel efficiency. As a type of metal waste product, food cans are often fabricated from aluminum and other metal alloys. These products are widely used in our lives; if they are not recycled, they can potentially pollute the environment as waste. Given these problems and considering the use of environmentally friendly materials, lightweight used cans were chosen as materials for the proposed impact attenuator design. In the initial study, the verification and validation tests of the impact attenuator shell and used cans show good agreement between the numerical and experimental impact tests. The proposed impact attenuator design under the predetermined parameters showed that used cans of aluminum 6063 series can be recommended as an alternative material in this system.

In order to meet the escalating demand in the shipbuilding business, suitable materials with enhanced qualities are required to maximize ship cargo while reducing fuel consumption. Aluminum (Al) and its alloys are competing contenders for use in a variety of complicated ship structures. The major challenge to enhancing joint quality and performance is the quest for a viable and efficient FSW parameter. The main focus of this study was to critically explore the effect of the tool pin profile and the preheat temperature used during the friction stir welding of AA 5052-H32 on its mechanical properties and weld microstructure characteristics. There are three pin profile variations, including samples that were cylindrical, samples with two flat sides, and samples with three flat sides, all of which were investigated in different preheat temperatures (150–300 °C). The results that were obtained during macrographic observation showed that tunnel defects were visible in the cylindrical and two-flat-sided pin profile designs. During observations of the microstructure, it was observed that the grain size became finer and smaller in the weld nugget compared to in the heat affected zone (HAZ) and thermo-mechanically affected zone (TMAZ) regions due to dynamic recrystallization. However, at the 300 °C preheat variation, the grain size appeared to be larger due to the slower cooling rate, causing a decrease in the mechanical properties of the samples. The results of the physical tests determined that the preheat temperature caused an increase in the mechanical properties until 250 °C, at which point the three-flat-sided pin profile tool demonstrated superior mechanical properties compared to the tools with a cylindrical design; a 12.2% tensile strength increase, a 15.3% and 9.4% face and root bending increase, and an 11.2% hardness increase were observed.

Along with developing high-speed craft technology, the planing hull is growing with modifications for better performance. One such technology is stepped hull, both single and double. Planing hull with steps allows the boat to run at a relatively low drag-lift ratio with lower frictional resistance due to reduced wetted area. In this study, the hull was modified with variations in the position of the double steps, which aimed to determine the effect of the first and second step positions on the total resistance, dynamic trim, and dynamic sinkage generated by computational fluid dynamics (CFD). Based on the analysis results, variations in the position of the stepped can change the hull performance. Shortening the distance between the two steps and moving both rearwards toward the transom can lower the total resistance. The dynamic trim and dynamic sinkage decreased as the position of the two steps was shifted further forward. An equation created in a non-dimensional form relates the positions of two steps to the desired results of total resistance, dynamic trim, and dynamic sinkage, namely: {(x1-x2)/L + (x1x2)/(LB)} × Fr∇, where x1 is distance the first step from transom, x2 is the distance of the second step, L is the length of the boat, B is the beam of the boat, and Fr∇ is the volume Froude number. [ABSTRACT FROM AUTHOR]

The development of human civilization over the last decade has reached a landmark as Industry 4.0 has been widely introduced. Several aspects of industry and manufacturing activities are changing due to the Internet of Things (IoT), location detection technologies, and advanced human–machine interfaces. To enact industrial affairs under those specifications, a sensor is required to transform physical events into numerical information. The use of sensors in marine applications also appears in research and studies, in which the sensor is used for both monitoring the phenomena of a designated subject and data acquisition. Achievements in quantifying complex phenomena in critical maritime designs are fascinating subjects to discuss regarding their development and current states, which may be reliable references for further research on developing sensors and related measurement analysis tools in marine, shipbuilding, and shipping fields. This comprehensive review covers several discussion topics, including the origins and development of sensor technology, applied sensor engineering in logistic and shipping activities, the hydrodynamic characterization of designed hulls, the monitoring of advanced machinery performance, Arctic-based field observations, the detection of vibration-based damage to offshore structures, corrosion control and monitoring, and the measurement of explosions on critical maritime infrastructures.