Crashworthiness performance of the designed concave hexagonal structures as filler element in cylindrical shell in multiple load cases

Safety Impact resistance is defined as the ability of a material to absorb impact energy through 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. In this study, numerical validation, mesh convergence studies and multiple load case studies were performed to investigate crash resistance under axial loading. Numerical validation results show that the similarity between this study and the reference reaches 95%. A deviation of 5% occurs due to different input material properties. The results show that the concave hexagons as filling elements have 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 has good impact resistance at low angles and no effect at high angles like 20°

Crashworthiness performance of the designed concave hexagonal structures as filler element in cylindrical shell in multiple load cases

Safety Impact resistance is defined as the ability of a material to absorb impact energy through 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. In this study, numerical validation, mesh convergence studies and multiple load case studies were performed to investigate crash resistance under axial loading. Numerical validation results show that the similarity between this study and the reference reaches 95%. A deviation of 5% occurs due to different input material properties. The results show that the concave hexagons as filling elements have 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 has good impact resistance at low angles and no effect at high angles like 20°

Design of the Bengawan Unmanned Vehicle (UV) Roboboat: Mandakini Neo

Mandakini Neo is an autonomous vehicle that was designed and built by the students of the Universitas Sebelas Maret, which was included in the Bengawan Unmanned Vehicle (UV) Roboboat Team to compete in the annual international Roboboat competition of 2021. This competition requires participants to complete several missions; one of the main missions is to move through two gates made from four poles using full automatic navigation, in order to continue on with the other missions. To complete the course, we used Pixhawk and GPS to allow the ship to run automatically, while minimizing the ship’s movement tolerance. The use of Mission Planner software for monitoring, and also for color and shape image processing to help with the reading of objects, along with a sensor fitted on the ship, allowed the mission to be completed. Mandakini Neo was made with the capacity, speed, and comfort of the ship in mind, as well as the ship’s hydrodynamic performance, stability, volume, structural integrity, and construction cost. Following its development we conducted tests of stability, maneuverability, and seakeeping in order to achieve the smallest possible resistance rate; for this purpose, we used the Savitsky method. The manufacture of the ship also required the choosing of the material, the use of the sensor, and also selection of an appropriate system. Finally, the design that we developed was a ship with a catamaran hull type, for which the dimensions had already been calculated, and the proper materials decided, and simple electrical components were able to be obtained for the sensor and the system

Consequence Analysis of Accidental LNG Release on the Collided Structure of 500 cbm LNG Bunkering Ship

The growing demand for liquefied natural gas (LNG)-fueled ships necessitates the establishment of an LNG bunkering facility. Ship-to-ship (STS) is one of the most practical forms of LNG bunkering systems. Although there are benefits to the LNG bunkering of ships, risk and safety issues are a concern due to the volatile cargo. Ship collision could result in accidental LNG release. The purpose of this study was to build LNG leakage scenarios, establish critical zones based on gas concentrations, and estimate the temperature reduction in a bunkering ship’s structure resulting from the use of cryogenic fluid. The condition of a target ship’s structure, both intact and when damaged due to collision, was considered. Leak size, leak direction, leak position, release rate, and reservoir pressure were included as leak parameters, and environmental parameters, such as the wind direction, wind speed, and ambient temperature, were also included. The release duration was set based on the shutdown duration of the emergency shutdown valve (ESD). A total of 72 leakage scenarios were generated for the main CFD analysis. Convergence tests were conducted to determine the appropriate grid and iteration numbers for a computational fluid dynamics (CFD) simulation. The gas dispersion characteristics and the cryogenic flow impact on the LNG bunkering ship’s structure are discussed through a parametric study

Determination of cryogenic temperature loads for finite-element model of LNG bunkering ship under LNG release accident

The rising demand for liquefied natural gas (LNG)-fueled ships requires the LNG bunkering facility that partially uses a ship-to-ship operation. The bunkering process of LNG fuel may have a greater risk due to LNG volatility. The cryogenic temperature of LNG poses a threat to the personnel and structural embrittlement to ships. Therefore, cryogenic spill protection optimization was introduced concerning the structural strength analysis using finite element (FE) by utilizing cryogenic temperature loads provided by the computational fluid dynamics (CFD) model of an LNG release. This study aims to build a platform for transferring the temperature load profile from CFD to FE software accurately. The CFD model usually uses a structured Cartesian grid, and the FE method adopts an unstructured tetrahedral or hexahedral mesh. As a result, both configurations store results at different positions, and it is not preferred for the load profile to be transferred directly. The error will be greater due to the variance of positions. Random Forest, a machine learning method, has been employed that uses a regression technique to deal with a continuous variable. An accurate load profile for the FE model can be obtained by adopting decision tree learning in Random Forest. The procedure for determining the temperature load profile is presented in this article

Effect of pitting corrosion position to the strength of ship bottom plate in grounding incident

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

Comparative Evaluation of Design Variations in Prototype Fast Boats: A Hydrodynamic Characteristic-Based Approach

As one of the world's largest archipelagic nations, Indonesia is tasked with the crucial responsibility of supervising and protecting its territorial waters from threats such as illegal fishing and damage to coral reefs. The effective and efficient execution of this task relies heavily on the use of fast patrol boats. Consequently, the need to investigate the hydrodynamic characteristics of these boats’ hulls is paramount. This study is primarily focused on the analysis and design of fast patrol boat hull prototypes. Our objective is to ascertain a practical design methodology that yields the optimal shape and size of the boat's hull. The adopted research methodology involved the design and analysis of eleven hull prototypes, evaluated based on resistance, stability, and seakeeping criteria. Five models were adapted from the reference ship, with a deadweight tonnage (DWT) variation of 2-3.5 tons. Three models employed the regression method with a block coefficient (CB) variation of 0.45-0.46, while the remaining three models utilized the scaling method, derived from the reference ship with the lowest resistance. The models in both the regression and scaling methods applied the primary size derived from the linear regression results of the five reference vessels. From the analysis, it was found that models developed using the regression method demonstrated superior hydrodynamic characteristics, denoted by consistently higher total values. This research provides valuable insights for the development of efficient fast patrol boats, which is crucial for the effective management of Indonesia's expansive maritime territory