Crashworthiness assessment of thin-walled double bottom tanker: A variety of ship grounding incidents

This study addresses the issue of ship accidental grounding as an impact phenomenon,with the assumption that an interaction of its structure with the oceanic seabed(obstruction),idealized as rock topology,is capable of initiating a so-called hard ground scenario.This occurrence variation was considered by performing two main instances,encompassing raking and stranding,often experienced by oil/chemical tankers as thin-walled structures.In addition,a failure criterion was implemented on the structural geometry,in order to define its ultimate limit and possible damage,during interaction with the obstructions.Subsequently,the analysis results were compiled to assess structural crashworthiness as well as progressive failure of the double bottom part of the tanker,where energy criterion indicated the raking to be more destructive.Meanwhile,detailed observation of the failure sequence indicated the stranding to have successfully breached the inner bottom shell.

Investigation on structural component behaviours of double bottom arrangement under grounding accidents

Marine accidents have caused immense casualties on various parties in shipping and shipbuilding industries, including financial and structural losses. This situation makes ship accident becomes a critical subject in naval architecture and marine structures, as it needs continuous assessment and investigation to broaden insight and data of collision and grounding phenomena. The paper aims to investigate structural conditions of a ship arranged by double hull system under accidental scenario, namely ship grounding. Fundamental concept of structure-rock interaction in poweredhard grounding is adopted to design impact configuration for calculation using finite element(FE)simulation. Involved entities are defined as the structure represented by tanker vessel, and oceanic rock is deployed as the indenter in analysis. Calculation results indicate that the crashworthiness capability of structural part strengthened by longitudinal girder is higher than other selected locations on the structures against rock penetration. Localized flooding of storage oil may occur during raking damage is formed on structural part between two girders.

Study on Collision Between Two Ships Using Selected Parameters in Collision Simulation

In the present analysis, several parameters used in a numerical simulation are investigated in an integrated study to obtain their influence on the process and results of this simulation. The parameters studied are element formulation, friction coefficient, and material model. Numerical simulations using the non-linear finite element method are conducted to produce virtual experimental data for several collision scenarios. Pattern and size damages caused by collision in a real accident case are assumed as real experimental data, and these are used to validate the method. The element model study performed indicates that the Belytschko-Tsay element formulation should be recommended for use in virtual experiments. It is recommended that the real value of the friction coefficient for materials involved is applied in simulations. For the study of the material model, the application of materials with high yield strength is recommended for use in the side hull structure.

Investigation on Savonius turbine technology as harvesting instrument of non-fossil energy: Technical development and potential implementation

Environmental risk due to excessive residual emission is rising. Greenhouse effect, ice melting in the Arctic, reduction of air quality are several concerns which need immediate development and change. Energy harvesting equipment is one of the key solutions. Environment potential, e.g. water resource can be collaborated with mechanical equipment to harvest clean energy. Savonius turbine has been proposed and studied for this purpose and can be placed on several energy resources, i.e. water and wind. Still, real-world implementation of this technology is lacking,especially in tropical archipelago countries which have abundant water resources. In this work,assessment of Savonius turbine technology as instrument to harvest clean energy is conducted. A series of development on the turbine performance and technical modification is considered as reference to implement the technology in water and open air environments. It is noted that rotor design, operation depth and nozzle attachment are several key influencing factors.

Analysis of structural behavior during collision event accounting for bow and side structure interaction

The main goal of this study was to investigate the effects of selected ship collision parameter values on the characteristics of the absorbed energy in several ship collision scenarios. Non-linear simulations were performed using a finite element method （FEM） to obtain virtual experiment data. In the present research, the size of the side damage from a collision phenomenon were measured and used to verify the numerical configuration together with the calculation results using an empirical equation. Parameters in the external dynamics of a ship collision such as the location of the contact point and velocity of the striking ship were taken into consideration. The internal energy and deformation size on the side structure were discussed further in a comparative study. The effects of the selected parameters on several structural behaviors, namely energy, force, and damage extent were also observed and evaluated in this section. Stiffener on side hull was found to contribute significantly into resistance capability of the target ship against penetration of the striking bow. Remarkable force during penetration was observed to occur when inner shell was crushed as certain velocity was applied in the striking bow.

Micromechanical analysis on tensile properties prediction of discontinuous randomized zalacca fibre/high-density polyethylene composites under critical fibre length

In this research,the tensile properties'performance of compression moulded discontinuous randomized zalacca fibre/high-density polyethylene under critical fibre length was analysed by means of experimental method and micromechanical models.These investigations were used to verify the tensile properties models toward the effect of fibre length and volume fraction on the composites.The experimental results showed that the tensile properties of composites had significantly increased due to the enhancement of fibre length.On the contrary,a decline in the tensile properties was observed with the increase of volume fraction.A comparison was made between the available experimental results and the performances of Tsai-Pagano,Christensen and Cox-Krechel models in their prediction of composites elastic modulus.The results showed that the consideration of fibre's elastic anisotropy in the Cox-Krenchel model had yielded a good prediction of the composites modulus,nevertheless the models could not accurately predict the composites modulus for fibre length study.

Experimental study of the effect of slotted blades on the Savonius wind turbine performance

This study investigates the effect of Reynolds number on the performance of Savonius wind turbine with slotted blades.The turbine performance investigation was based on the torque coefficient(Ct),power coefficient(Cp),and tip speed ratio(TSR).The experiment used two number of blade configuration,blade overlap ratio of 10%,12.5%and 20%,slotted position of 15%,20%,25%and 35%,and also slotted gap width of 3 mm,5 mm,7 mm,and 9 mm.The wind speed carried out in this experiment are 5.94 m/s,6.46 m/s,6.99 m/s,and 7.27 m/s,which are generated from the fan blowers as a wind source.The Savonius turbine with 10%overlap ratio shows the best performance.The highest Cp obtained is 0.138 by the variation of a 3 mm gap with Re of 1.44×10^(4) and 0.526 TSR.

Assessment of the stiffened panel performance in the OTEC seawater tank design:Parametric study and sensitivity analysis

Ocean thermal energy conversion(OTEC)is a process of generating electricity by exploiting the temperature difference between warm surface seawater and cold deep seawater.Due to the high static and dynamic pressures that are caused by seawater circulation,the stiffened panel that constitutes a seawater tank may undergo a reduction in ultimate strength.The current paper investigates the design of stiffening systems for OTEC seawater tanks by examining the effects of stiffening parameters such as stiffener sizes and span-over-bay ratio for the applied combined loadings of lateral and transverse pressure by fluid motion and axial compression due to global bending moment.The ultimate strength calculation was conducted by using the non-linear finite element method via the commercial software known as ABAQUS.The stress and deformation distribution due to pressure loads was computed in the first step and then brought to the second step,in which the axial compression was applied.The effects of pressure on the ultimate strength of the stiffener were investigated for representative stiffened panels,and the significance of the stiffener parameters was assessed by using the sensitivity analysis method.As a result,the ultimate strength was reduced by approximately 1.5%for the span-over-bay ratio of 3 and by 7%for the span-over-bay ratio of 6.

Investigation of Agave cantala-based composite fibers as prosthetic socket materials accounting for a variety of alkali and microcrystalline cellulose treatments

This study was aimed to determine the mechanical strength of composites made from Agave cantala with an unsaturated polyester matrix and microcrystalline cellulose.Cantala fiber(CF)was treated with 6%Na OH with immersion times of 0 h(UF),3 h(AK3),6 h(AK6),9 h(AK9),and12 h(AK12).Thermogravimetric analysis(TGA)analysis shows that treated CF has higher thermal stability than CF without treatment.Cantala fiber was tested by X-ray diffraction.After alkali treatment with a 6-h soaking,it had a crystallinity index of 73.65%.Scanning electron microscopy(SEM)showed that the fibers were cleaner after alkali treatment because hemicellulose,wax,and other impurities were removed.Examination of the contact angle and surface energy showed that treated CF has smaller contact angles and greater surface energy.

Exploring the potential of graphene materials in marine and shipping industries-A technical review for prospective application on ship operation and material-structure aspects

Advance development of materials technology introduces graphene as a powerful material for various applications in any branch of engineering and industries.Marine and shipping are one of the projected industries which are affected by graphene improvement.The conventional approach of technical manufactures and processes on ship and maritime environments,such as water treatment,oil separation and evacuation,is proven to be developed into more practical ways by utilizing characteristics and properties of graphene-based material.This work is addressed to study graphene as an engineering material in which structural arrangement,mechanical strength,electrical conductivity,and permeability of the material are discussed.Instrumental and cycle applications related to ship operations are defined to be an initial milestone to assess dedicated works in graphene and ship.Potential and future projections based on the works are linked with existing challenges and problems on boards,such as free surface effects and materials coating.Several works showed that graphene-based baffle has the potential to replace the current baffle style in oil tankers and liquid carriers.The electrical conductivity of the graphene is also useful for structural coating for ships that can operate in extremely cold regions,e.g.,the Arctic and Antartica.

Crashworthiness assessment of thin-walled double bottom tanker: Influences of seabed to structural damage and damage-energy formulae for grounding damage calculations

This work presents results of numerical analyses with focus on structural performance accounting for seabed topology,and investigation of energy formulae for application in calculation of grounding damage.Study in this work is divided into three stages,i.e.finite element method(FEM)verification using laboratory experiment,numerical calculation of ship grounding using FEM,and comparison of the FEM results with empirical formulae of damage-energy calculation.Fundamental formula of Minorsky is considered with other improvement expression,such as Woisin and Zhang.Investigation suggested that the recent-developed expression produces the closest estimation to the verified FEM results.On the other hand,fundamental formulae of Minorsky is the farthest compared to the FEM,which indicates constant value in the expression needs to be more specific as improved in the Woisin formula.