Quasi-Static Flooding Analysis Method of a Damaged Ship Considering Oil Spill and Cargo Load

When a ship is damaged at sea, it is important to predict its behavior as well as whether it is to sink or not. If the ship comes to an equilibrium, the equilibrium position and time should be estimated; otherwise, the time to sink should be estimated. Furthermore, flooding analysis should be carried out not only during the design stage of the ship for preventive reasons, but also after an accident for a better investigation of its causes. In addition, flooding analysis methods that can provide predictions in case of an accident are of particular importance, as there is no time for the required calculations in an emergency. For this purpose, a quasi-static flooding analysis method for the damaged ship in the time domain is proposed in this study. There are a number of studies in which the equilibrium position and time were estimated by flooding analysis. However, most of them have not considered the air pressure effect in fully flooded compartments, and the method of determining the fluid volume in these compartments was not accurate. In the present study, the virtual vent and accumulator method are used to calculate the reference pressure in the fully flooded compartments, and the compartment shape is considered by using polyhedral integration. Also, spilled oil and solid cargo items from the damaged ship are taken into account for realistic flooding analysis. Finally, the damage stability criteria were checked not only in the final state, but also during the entire time of the flooding, as the intermediate states can be more hazardous than the final state. To validate the feasibility of the proposed method, it was applied to a naval ship, which is considerably more stringent for damage stability. As a result, we checked the availability of this study.

Effect of Preheating on Hot Cracking Susceptibility in Pulsed Laser Welding of Invar Alloy

Hot cracking is a serious problem in welding of Invar alloy. The weld hot cracking susceptibility of Invar was evaluated using pulsed laser welding on fish-bone sheet experiment. The pulse wave consisted of preheating pulse and welding pulse. Hot cracks that formed along the grain boundary propagated from the weld upper surface to the inside. The experiments show that adding a preheating pulse can effectively reduce the hot cracking susceptibility of Invar alloy. Finite Element Modeling (FEM) calculations and experimental measurement results show that the welding temperature gradient and cooling rate decrease with increasing preheating pulse duration. However, as the preheating pulse duration increases, the hot cracking susceptibility of the Invar alloy does not decrease all the time, but decreases first and then increases. This is because the increase of heat input leads to the increase of shrinkage plastic strain when the preheating pulse duration increases. The maximum tensile strength of the butt welded joint of the Invar alloy was 467.3 MPa, which is 92.3% of the base metal when the preheating pulse duration is 3 ms.

Predicting Ship Maintenance and Repair Labor with Artificial Neural Networks

Ship maintenance and repair work cost estimation is often regarded as an “Art,” which may contribute to the financial success or distress of a shipyard. Regarded as experts by senior management, estimators are among the most valued resources, and nonetheless, human. Over time, estimators learn from mistakes, and get better with tenure at sharpening assessments. When estimators retire without having groomed an apprentice, shipyards may be at risk of losing a lot of know-how, all at once. These shipyards may well find very costly to experience, for a while, estimating skills stepping back on the learning curve. Yet, even shipyards relying on less advanced information technology may have unwittingly accumulated a lot of valuable data relevant to ship maintenance and repair works. These shipyards may overlook how easily accessible knowledge can be turned into a competitive advantage through predictive analytics. Not only can this data be literally mined, but machine learning algorithms, such as Artificial Neural Networks (ANN), can now process it for a speedy and preliminary estimate through faster and cheaper computing power. To be clear, the purpose is not to replace the human estimator but to help the expert quickly assess, when times are busy, whether to bid or not on a specific project opportunity. In the absence of The Master Estimator, an Apprentice may also look for a quick and cheap sanity check of the prepared estimate before submitting a bid. The study carried out in this article is based on all ship maintenance and repair data recorded at a single North American shipyard over the last 19 years since the current information systems were implemented. This raw data extract with all directly paid hours logged daily by workers on 1277 ship maintenance and repair projects was screened through advanced data cleansing. To enrich the cleansed data tables, additional independent variables were subsequently collected internally and externally to develop a training–testing data set. The final 657 projects represent 136 vessels regrouped in eight types, for which 28 other independent variables were all made available for training up to testing simple ANN models. The scope of this article is limited to the estimation of the direct labor required to complete ship maintenance and repair projects on a specific type of vessels for which workforce planning and tactical pricing was deemed the most relevant to keep the business afloat.

Priority Assessment of Key Factors of IMO-MSC/Circular.834 for Ship Engine Room Safety and Efficiency Based on Human Aspects

International Maritime Organization (IMO) has published technical circular (MSC/Circular. 834) including nonmandatory guidelines with five main criteria about engine room layout, design, and arrangement. The purpose of this study is to present the most important priority criteria of seafarers about engine room design according to the criteria from IMO MSC/Circular.834 guidelines. Since there are no obligations, the priority and importance of these criteria are not clearly emphasized. Therefore, the determination of seafarers’ priorities for arrangement in terms of safety and efficiency become important to make decision. For this, fuzzy Analytic Hierarchy Process (AHP) technique, which is one of the most used fuzzy Multiple Criteria Decision Making (MCDM)methods is employed. Introduction Maritime transportation, known for oldest and widespread transportation around the world, with 11 billion tons weight and 80% rate of world trade volume (UNCTAD 2019). Maritime transportation has many components and one of the most important and effective parts of these components are ships and seafarers. Because of the difficulty of ship conditions, ships should be present optimum working conditions for seafarers in order to achieve effective and safe operations on board. At the present time, there are previous studies about the difficulty of working studies on board. It is a scientific and cultural fact that seafarers are under higher risk of working conditions comparing to other jobs (Bloor et al. 2000; Havold 2005; Hetherington et al. 2006; Mallam et al. 2015). Due to this reason, International Maritime Organization (IMO) has made various regulations for years in order to improve seafarers’ safety and efficiency on board. One of the goals of these regulations is to design optimum working conditions on board for seafarers. Based on complex structure and having various danger conditions, engine room design is considerable to ensure safety and efficiency for engine room department seafarers.

Influence of Tubercle Modifications on the Performance of Marine Vertical Axis Propellers

Even though past efforts in computational fluid dynamics (CFD) simulations have shown great progress in the implementation of tubercles into aero-foils and turbines blades, incorporating these tubercles into marine vertical axis propellers is still comparatively less well understood. In general, the performance of marine propellers is highly related to the pressure and velocity distributions over the propeller blades. Since the presence of tubercles’ serrations in the blade leading edge can vary these distributions over the blade, the performance of the propellers can be enhanced. In this article, tubercle modifications are investigated in marine vertical axis propellers through the use of CFD simulation. To achieve this purpose, a complete procedure of CFD simulation using ANSYS FLUENT 16 is proposed. Obtained CFD results are validated using direct comparison with the previous analytical studies. Obtained performance characteristics of the modified vertical axis propeller are assessed against the available characteristics of the baseline one. The CFD results are found in a good agreement with the analytical ones. Moreover, the results demonstrate the improvement of the obtained performance of the modified vertical axis propeller compared to the baseline one in terms of increased thrust coefficient and higher efficiency over the considered range of advance ratio. Introduction Shallow waters, rivers, and seas; the presence of obstacles; the complexity of water routes; and the territorial orography require the availability of effective maneuverability to enhance marine propulsion compared to the traditional rudder-propeller system (Pasetto1 2013). In this context, the vertical axis propellers (VAP) can be a real and valid alternative to the rudder-propeller system (Chen 2007), allowing the ships to navigate in an effective way also in the difficult routing and in shallow water conditions (Carlton 2007). The VAP provides the ability to sail vessels in all sea conditions effectively. It maintains the ability to direct the thrust to 360° and, consequently, provides a better performance in terms of maneuverability, stop and crash maneuvers and higher efficiency. It is therefore necessary for all kinds of vessels requiring high level of maneuverability in congested waterways to be equipped with VAPs for ease, safety, and immediate response.

Study on Optimal Design of a Folding-Type Hatch Cover Considering Material Selection

Most shipyard companies maintain efficiency in all aspects of their business to survive. One of these aspects is ship production costs and their reduction. This study proposes a solution to this problem using an optimization method. A hatch cover composed of plates and stiffeners was selected as a case study. In this study, the mass and material cost of the hatch cover was optimized as an objective function using the Pareto approach with developed optimization methods. Plate thickness t, stiffener shape s, and plate material type m were selected as the design variables in this study along with some constraints. To estimate the optimal plate thickness, an expression of stress equations was Developed using an optimization technique. Furthermore, stiffener shape and plate material type selection were optimized using a genetic algorithm (GA). The results show that the optimization method is effective to decrease the mass and material cost of a hatch cover. Introduction The demand for new shipbuilding has decreased because of the effect of the economic crisis that hit almost every country in the world. Shipyard companies must think innovatively and creatively to survive under the pressure of this crisis by evaluating various studies and improvising new methods to achieve efficiency. One of the studies that has been performed examines the methods to reduce the fabrication cost of ship structures to stay profitable through the optimization of work hours, workflow production systems, and structural design.

Design of Risk Prediction Assessment for Ship-Integrated Electric Propulsion System

A design of risk prediction assessment is proposed to improve the safety and economy of ship-integrated electric propulsion system(SIEPS). Firstly, the article puts forward a multihidden Markov model (MHMM)–Viterbi algorithm to predict fault state probabilities of each component in the continuous time points in the future. Secondly, according to the influence of dynamic ocean condition, the fault states of the components of SIEPS are predicted by using the MHMM–Viterbi algorithm. Thirdly, the risk assessment system of network topology of SIEPS is designed, and power flow analysis under the abnormal condition is repeatedly calculated by using the MonteCarlo simulation. Finally, the article takes a SIEPS as an example and the risk prediction assessment results is given. Introduction With the establishment of increasingly stringent standards by the International Maritime Organization in terms of ship emissions and the increasing scarcity of petroleum resources, electric propulsion systems are gradually replacing internal combustion engines, which will become the future direction of ship power development. Electric propulsion ships do have many advantages such as high efficiency, high automation, environmental protection, energy saving, and emission reduction. However, ship-integrated electric propulsion system(SIEPS) is also the soft underbelly of electric propulsion ships. First of all, the complexity of the external environment factors such as high humidity and high salinity of ships (especially marine vessels) under long-term operating conditions, and the coupling of electromagnetic, thermal, and vibration signals of SIEPS will increase the failure rate of electrical equipment, thereby increasing the risk of SIEPS. Secondly, for electric propulsion ships, the SIEPS risk is likely to lead to chain failure of important systems such as power, control, navigation, resulting in the ship. Equipment and even personnel cause irreparable damage, causing fatal damage to electric propulsion ships. Therefore, in order to improve the safety, reliability, and economy of electric propulsion ships, it is necessary to carry out research on relevant technologies for SIEPS risk assessment (Wen et al. 2012; Guangfu et al. 2013).

Evolution in Design Methodology for Complex Electric Ships

Modern ships are highly complex technological systems and have a long and resource-intensive development cycle. Moreover, the final design must comply with many specific technical and regulatory requirements while constraining the capital and operational expenditures. Decisions made during the early stages of design have a large impact on ship functionality and determine the overall configuration of the ship; the advanced computational resources available today can be used to change the traditional approach to ship design, significantly improving the data available for these early-stage decisions. Moreover, the new methodologies can improve the ability to assess the impact of innovative technologies such as those inherent in the complete electrification of ships, and can simultaneously allow visualization of a three-dimensional (3D) virtual prototype of the designs. In this article, a methodological approach is presented that exemplifies these advantages.

Influence of Ship Design Complexity on Ship Design Competitiveness

Complexity is discussed in design literature mainly through its negative and in some cases positive consequences. This article critically reviews and elaborates the effects of complexity on competitiveness in ship design, its directionality, and magnitude. The article introduces a model for the measurement of ship design complexity and ship design competitiveness based on predefined factors. Archival data of 100 ship design projects from eight different Norwegian designers are used as case study. Multivariate data analysis techniques are employed to study the research model. The results show a significant correlation between complexity and competitiveness in ship design, where the magnitude and directionality of influence vary among different complexity factors. Our findings provide a basis for enhancing complexity management in ship design. Introduction Continual technology improvements and market volatility with its associated uncertainties have a significant impact on and partly change ship design customers’ expectations. To be successful in such a market, not only does it require the development of competitive products but also the accompanying work processes and the organization or firm framing the development of the vessel solution are involved. Ulstein and Brett (2015) define ship design competitiveness in terms of doing the right thing (effectiveness), doing the right thing right (efficiency), and with the right resources (efficacy) to cover product, process, and firm aspects of competitiveness. To improve their success, ship design companies typically tend to focus on the introduction of new technologies, and, in some cases, extra functional capabilities, which have led to large and complex vessels over the years. To a lesser extent, ship designers have put emphasis on the overall needs of customers. Securing a higher overall performance yield of the ship design solution than peer vessels out in the market is not a common practice among ship designers; they rather focus on a typical and traditional subset of performances. The implications and the consequences of such strategies in ship design have led to a growing need for a new set of design tools and project-making skills, a more extensive design process with different disciplines involved, and many iterations in the design development process.

Design and Experiment of Inerter-Rubber Vibration Isolator Based on Parallel Inerter-Spring-Damper System

Since an inerter has been widely used in the field of vibration isolation, the combination of the inerter and the rubber part inevitably becomes a trend. In this work, a parallel inerter-spring-damper system (II-ISD) was introduced and analyzed for its performance on vibration isolation. Then, the optimal inertance-mass ratio and the frequency ratio at the minimum transmissibility were obtained. Based on the II-ISD system, an integrated vibration isolator was designed where the rubber part paralleled to the inerter, which was named as the inerter-rubber vibration isolator (IR). Then, its mechanical properties were simulated, and the mathematical model was established by considering the vibration isolation performance and the service life. Afterward, it was optimized by a programmed multi-objective genetic algorithm, and the optimal design parameters of IR were got finally. The experimental prototype of IR was processed, and its performance experiment was performed on the Mechanical Testing System (MTS) test bed. Experimental results show that the theoretical model of IR based on the II-ISD system is accurate; the resonant peak of IR is clearly lower than that of the rubber vibration isolator; the natural frequency decreases obviously. This work provides a design method for the serial product development, which has a practical engineering significance.