Hull Elements Research Articles

Technology features of manufacturing samples made of composite materials and some of their tests results

Recently, there has been an upsurge in the development of additive technologies, and engineers and scientists are looking for new formulations with which to build relatively small parts and hull elements. For the construction of large objects entirely, for example, the hull of a small vessel, and even more so in mass production, it is necessary to maintain a balance of cost, quality, applicability of material, weight and strength characteristics. The most common material in small-scale shipbuilding of recent times is fibreglass based on polyester and epoxy resins. This material, with intensive use of the boat, has a service life of 15-20 years, and with proper care, this period can be extended. Cases made of glass-plastic have the necessary technical characteristics, both in the production of cases of complex geometry and in further operation. Attempts have already been made to create 3D printers in which polyester resins are used as a printing material, but the negative side of this equipment is that there is no reinforcement between the layers, which reduces the strength, and the layer thickness, which significantly increases the printing speed. Based on the experience gained, a material based on polyester resin was proposed, which has reinforcing fibres in its composition, thanks to which it has a pasty consistency, and retains its shape when applied and does not spread.

Effect of Corrosion-Induced Structural Degradation on the Ultimate Strength of a High-Tensile-Steel Ship Hull

Standard structural assessments of ship hulls include the evaluation of the elastic structural response. Elastic analysis neglects extreme and unpredicted loadings, which can produce catastrophic outcomes, such as the loss of the ship’s ultimate strength. Moreover, hull elements are considered unaffected by age-related degradation. Therefore, this study models and quantifies the effect of corrosion-induced structural degradation on the ultimate strength of a high-tensile-steel (HTS) cargo ship using progressive collapse and nonlinear finite element methods. Uniform and pitting corrosion are modeled through selected scenarios, which hull elements might encounter during exploitation, producing a total of 148 calculation models. The findings show that corrosion-induced degradation can significantly decrease the ultimate strength of the hull (up to 30% for the most severe scenarios assessed). Furthermore, ultimate strength decreases almost proportionally to the amount of wastage considered. It was found that stiffener corrosion has a significant effect on the total ultimate strength. This study’s aim is to emphasize the vast importance of including ultimate strength along with ageing effects in industry-standard structural assessments of large HTS ship structures, designed to last for several decades whilst exposed to excessive and unpredicted bending moments.

Reliability of river fleet vessels hull elements

Improving the process of fault detection of metal ship hull elements by using a probabilistic approach is considered in the paper. The most labor-intensive part of the defect detection report, namely, measurement and assessment of hull structures individual elements wear, accounting for more than 90 % of the total measurements, is reviewed. Defect detection of a ship hull means the examination, measurement and assessment of defects in each element of the ship hull in order to establish method and volumes of repairs that ensure its reliable operation until the next survey under specified operating conditions. The necessity of carrying out a preliminary calculation stage for defect detection is substantiated. It allows you to significantly reduce the number of measurements of hull structures elements, which will have a positive effect on reducing the cost of repair both due to a smaller number of measurements and the duration of repairs. It has been proved that using the probability approach to predict the residual thickness of individual elements also takes into account the effect on the total strength, which guarantees the reliability of the ship hull in operation. Tables to assess the technical condition of individual hull elements based on their level of wear have been developed, and a method for filling them has improved. The tables are made in two versions, namely, paper and electronic, the most convenient for a specific user — the designer of the defect detection report tables. A test example of using the electronic tables for assessing technical condition by wear level, which proves that the predicted residual thicknesses obtained by calculation will in all cases, be less, than similar ones obtained from measurements results, is carried out using a representative vessel. This proves the reliability and feasibility of using the preliminary defect detection stage, which is essentially an analogue of the concept of the zero stage in ship repair. Using the probability approach to determine the residual thicknesses will allow you not only to reduce the costs of defect detection of the hull itself, but also at early stages (before placing the ship on a slip or dock) to reduce the volume of hull structures repairs, and to choose the most appropriate and effective method of repair.

OPTIMAL FAULT DETECTION OF RIVER SHIP HULLS

The issue of determining the reliability of the hulls of inland and river-sea-going vessels after a known number of years of operation under given condition is considered. It is accepted that fault detection of a ship’s hull is a survey, measurement and evaluation of defects in each element of the ship’s hull in order to establish the methods and scope of repairs that ensure its reliable operation until the next regular survey under specified operating conditions. It is shown that the volume of residual thicknesses can be significantly reduced using the statistical data on wear rates presented in the Rules of the Russian River Register. At the same time, the reduction in the scope of measuring the parameters of defects retains the probability of detecting all defects of the hull elements to the level of 0.95, and the probability of failure-free operation of the hull until the next survey, after the elimination of the identified defects will be at least 0.95. A form of table for processing the values of the residual thicknesses of all elements in the inspection report and instructions for filling it out are given. Explanations for using the results of measurements and calculations at determining the technical condition of certain elements in the group and the ship’s hull as a whole are given. The last column of the table indicates the method of eliminating the defect of an element and groups of elements, and in the conclusion of the inspection report, the method of repair and its scope for the entire hull of the ship providing a suitable assessment of the condition after repair are indicated. The main advantage of this paper, in difference from the previous studies of the authors in this area, is that user-friendly (the designer of the defect report tables) nomograms, which allow you to reduce the number of measurements of the residual thicknesses of hull structure elements in the online mode, have been created. The performed study, allowing you to reduce the number of measurements while guaranteeing the reliable operation of the ship’s hull, will let the shipowner to reduce the cost of repair work by reducing the number of days of ship standing on the slipway (in the dock). In addition, the ship repair company will be able to free up its production facilities for the purpose of their subsequent loading with other ship repair or shipbuilding orders, which will increase the efficiency of their activities.

Development of cathodic corrosion protection systems of nuclear ice breakers and arctic offshore structures

This article presents the results of the development and implementation of special ice-resistant anodes on nuclear icebreakers and offshore structures, capable of ensuring long-term effective cathodic corrosion protection systems under shock and abrasive effects of Arctic ice. The results of inspections of the hull and hull elements of the cathodic protection of the nuclear icebreaker “50 Let Pobedy” and the offshore ice-resistant platform “Prirazlomnaya” after their long-term operation are shown. Cathodic protection of the atomic icebreaker “Leader” has been described.

GPU-Based DEM Simulations of Global Ice Resistance on Ship Hull During Navigation in Level Ice

The ice resistance on a ship hull affects the safety of the hull structure and the ship maneuvering performance in ice-covered regions. In this paper, the discrete element method (DEM) is adopted to simulate the interaction between level ice and ship hull. The level ice is modeled with 3D bonded spherical elements considering the buoyancy and drag force of the water. The parallel bonding approach and the de-bonding criterion are adopted to model the freezing and breakage of level ice. The ship hull is constructed with rigid triangle elements. To improve computational efficiency, the GPU-based parallel computational algorithm was developed for the DEM simulations. During the interaction between the ship hull and level ice, the ice cover is broken into small blocks when the inter-particle stress approaches the bonding strength. The global ice resistance on the hull is calculated through the contacts between ice elements and hull elements during the navigation process. The influences of the ice thickness and navigation speed on the dynamic ice force are analyzed considering the breakage mechanism of ice cover. The Lindqvist and Riska formulas for the determination of ice resistance on ship hull are employed to validate the DEM simulation. The comparison of results of DEM, Lindqvist, and Riska formula show that the DEM result is between those the Lindqvist formula and Riska formula. Therefore the proposed DEM is an effective approach to determine the ice resistance on the ship hull. This work can be aided in the hull structure design and the navigation operation in ice-covered fields.

Corrosion behavior of novel AA1050/ZnO surface composite: A potential material for ship hull

Friction stir processing is one of the effective surface treatments which was employed to process the AA1050 sheets in bare and reinforced condition. The primary objective of the investigation was to expand the applications of AA1050 as a ship hull element in shipbuilding with the least corrosion rate to withstand the harsh marine environment. The base material processed with a rotational speed of 1200 rpm resulted in the highest corrosion rate of 0.173622 mpy. The formation of Al-Fe intermetallic phases was responsible for pitting corrosion. Further, processing by embedding zinc oxide with a rotational speed of 1000 rpm exhibited ~6.68 times improvement in corrosion resistance compared to as-received material. The corrosion rate was found to be 0.003390 mpy. The Al2O3 passive film hinders the initiation and propagation of pits. This study coins a novel composite material and future investigations are emphasized on the same lines.

OPERATIONAL CONTROL OF THE STATE OF ANTI-CORROSION PROTECTIONAS A FACTOR IN THE SAFETY OF TECHNICAL OPERATION OF MARINE VESSELS

The technical operation of modern marine vessels is inevitably associated with the aggressive effects of electrochemical corrosion on hull structures and the ship as a whole. Corrosion processes have a destructive effect on hull elements, welded joints of metal structures, as a result of which there is a violation of water tightness, a decrease in the general and local strength of the hull, other operational characteristics of the vessel, reliability parameters of the hull structures and, as a result, a decrease in the safety of navigation and environmental safety, including at the points of basing ships and adjacent waters. This factor requires the introduction of special methods of corrosion protection, the main of which are the use of coatings and the use of electrochemical protection of ship hulls. Maintaining the integrity of coatings and a given level of hull electrochemical protection during the operation of the vessel involves the implementation of a set of interconnected engineering, technical and organizational measures, the basis of which is the operational control of the state of corrosion protection.

REALIZATION OF BASIC METHODS AND MODELS OF PROTECTION FOR LIGHT MASS CATEGORY COMBAT VEHICLES FROM KINETIC AMMUNITION

The protection of light mass combat vehicles from kinetic ammunition is formed as a complex task of determining the patterns of influence of design factors, characteristics of damage means and conditions of combat use on the ability to withstand small arms and low caliber automatic guns. Parameterized armored hulls models of light mass armored vehicles, which are located on the territory, which is also parameterized, has been developed. The weapon caliber and the type of ammunition are also taken into account as parameters that interact with armored hull elements. On this basis, the construction of three-dimensional tactical diagrams of armor-resistant is built. Characteristic influences of various parameters are determined on zone’s shape and size, from which the damage of light mass combat vehicles is possible. This gives an opportunity to substantiate the design parameters of the protective elements of these machines by the criterion of protection against the action of kinetic ammunition. In addition, the basis has created for the development of tactical techniques in order to minimize the likelihood of their destruction, taking into account the conditions of combat operations, including terrain.

COMPLEX MATHEMATICAL MODEL FOR PROTECTION ANALYSIS OF LIGHT MASS CATEGORY COMBAT VEHICLES FROM SMALL ARMS TAKING INTO ACCOUNT VEHICLE GEOMETRY, LOCATION RELIEF AND ADDITIONAL ARMOURING

A developed complex mathematical model is presented for 3D tactical diagrams constructing on the locality and the armored protection level estimation from small arms for light mass category combat vehicles. This model allows to calculate the bullet flight parameters depending on the range, on the bullet meeting angles with armored housing element, on the arrow position and the armored hull element position, as well as the breakthrough speed of hull armored elements, taking into account the additional armouring. The created mathematical model allows to solve the tasks of the safe zone estimation for light mass category combat vehicles, taking into account the actual hull geometry, location relief and armor-proofing of existing and projected light mass category combat vehicles, for a reasoned choice of protection methods from modern small arms, in particular with allowance for additional armoring.

Анализ взаимодействия конструкций наружного корпуса с гибкими связями

This paper investigates stress-strain state of hull with longitudinal and transverse stiffeners under compression due to flexible lines (straps). Architecturally, two hull variants have been studied: rectangular with roundings at bilges and cylindrical. The problem was solved as per well-known analytical expressions, whereas stress-strain parameters of “hullstrap” system, depending on strap stiffness and presence of “loose” contact with the strap and the plating, were updated in ANSYS and LS-DYNA software packages. The study yielded the following data: stress-strain parameters of plating taking into account longitudinal and transverse stiffeners; loading patterns for separate hull elements (plate, stiffener) depending on strap stiffness; and loading patterns for separate hull elements in case of “loose” contact with straps in the areas of finite length.

Wavelet-Based Time-Domain Solutions for Common-Mode Currents on Open-Form Conductors Modeled With Band-Limited Scattering Parameters

One of the technical challenges of future naval surface combatants in utilizing medium-voltage dc distribution systems is common-mode coupling and galvanic isolation for managing faults and personal safety. The behavioral modeling reported in this paper is computationally efficient to be used in modeling distributed common-mode currents and potentials throughout the open-form conductor, which in this case is the ship structure. Physics-based modeling is used to form a multiport S-parameter behavioral model of the ship structure that complements the S-parameter models of parasitic paths to grounded equipment enclosures and cables sheaths. A time-domain common-mode conduction example is presented to illustrate the workflow that converts physics-based models of elementary hull elements into a complete S-parameter behavioral model of an arbitrary hull structure with power cables running along it. Because of the measurement and the simulation bandwidth limitation, the frequency domain model based on S-Parameters is band-limited. A novel approach for reconstructing the system impulse response in the time domain from its band-limited S-parameter model is introduced using continuous wavelet transform utilizing fast Fourier transform.

STRESS-STRAIN STATE SIMULATION OF WELDED PLATE

Background. The most important task in choosing the shape of the structural elements of the ship’s hull is to ensure sufficient strength with a small mass. In recent years, great progress has been made in shipbuilding thanks to the use of modern welding methods for connecting parts and components. Ships hulls have become much lighter than when using riveted joints due to the transition to welding. A welded joint can provide optimum corrosion resistance, strength and economy of manufacture. However, it must be remembered that any metal, including stainless steels, may undergo certain changes during welding. Therefore, it is necessary to exercise a reasonable degree of caution during the welding process. In recent years, simulation has become a very popular method for studying processes and phenomena. In addition to mathematical methods, more and more often, authors from all over the world are starting to use simulation modeling as the main research method and compare the results with theoretical or experimental ones. There are many software products that allow you to create geometric models of objects of varying complexity. One such program is SolidWorks, which was chosen to create the geometric models in this study.Objective. Therefore, the purpose of this work is to conduct geometrical modeling (construction of three-dimensional models) and simulation (study of the object by its model) of a metal plate with a weld. Also, a liquid-construction interaction analysis will be carried out to determine the stress-strain state of the metal plate (ship’s hull element) with welds of different geometric shapes in the cross-section.Results. In this work, a three-dimensional model of the ship’s hull element with welded seams was built. To determine the vector fields of the velocity of water flow and its pressure in the ANSYS software package, a simulation of the load on the hull element was carried out using its constructed geometric model. The analysis of the obtained results made it possible to determine the stress-strain state of the ship’s hull element.Conclusions. Three forms of welds are considered, namely: V-shaped, Y-shaped and X-shaped. It is shown that at a flow rate of 5m/s the minimum load is less than at least three times for the X-shaped (double-sided) weld. The maximum loads within the hull element of the ship are almost the same. It is shown that the smallest stress within the welds (without considering the plate) arises when using an X-shaped weld. In further research it is planned to investigate the effect of loads from the water stream on the damaged weld seams.

An Improved Numerical Computation of Hull Pressure Fluctuations Due to Unsteady Sheet Cavitation of a Propeller

An operating propeller is the main source of vibration on the ship hull, especially on the stern. In this article, an improved numerical scheme is presented to predict the pressure fluctuations on the ship hull due to the unsteady sheet cavitation of a propeller. The calculated results are compared with the published results and experimental data carried out in the hydrodynamics and cavitation tunnel of Hamburgische Schiffbau-Versuchsanstalt to verify the improvement. The present method is based on a two-cycle iterating scheme which satisfies the boundary integral equation in time domain. The hull pressure fluctuations calculated by the first-cycle iterations are treated as the initial values for the second-cycle iterations. The solid angles of the elements will deviate from the standard value, .5, as the dramatic variation in geometry appears, and accumulate numerical errors in the calculating process. During the second-cycle iterations, a filter based on the solid angles on hull elements is proposed to minimize the iterating error. A container ship is treated as the computing sample in this study, and evidence is offered regarding the 16% improvement achieved by the present method. 1. Introduction A propeller operating in a nonuniform wake field in the ocean is one of the prime sources of vibration and noise affecting the ship. The prediction of hull pressure fluctuations caused by propellers is an important consideration for many vessels and worthy of being researched. Hull pressure fluctuation caused by the marine propeller has been widely investigated since the 1980s. Huse and Guoqiang (1982) developed a semi-empirical prediction method, in which the cavitation volume on the propeller blade surface can be estimated using experimental data. Breslin et al. (1982) proposed a model based on the potential flow theory, which simulates the ship hull by means of a simple panel method and the propeller by means of a lifting surface vortex lattice method. Kinns and Bloor (2004) used an acoustic boundary element (BE) model to simplify the problem of hull vibration excitation due to propeller sources and dipoles. The convergence of results for a cruise liner model was demonstrated with different element distributions. Kehr and Kao (2004) derived the incident blade rate pressure induced by unsteady sheet cavitation (monopole) and unsteady forces (dipole) of an operating propeller, for calculating the hull pressure fluctuations. Brouwer (2005) applied a stationary set of rings of monopole and dipole sources in the frequency domain to solve the propeller-induced noise and vibrations. Lee et al. (2006) integrated computational fluid dynamics (CFD) and the finite difference method for the computation of propeller-induced hull vibration. It was recommended that the phase difference of the propeller-induced pressure should be considered for preventing overprediction. Kao and Kehr (2006) developed a time domain iteration method to calculate the hull pressure fluctuations induced by the operating propeller. The phase difference is included in the iterating scheme, and the computation is robustly convergent. Seol and Moon (2009) derived the governing equation of pressure fluctuation induced by sheet cavitation according to the Ffowcs Williams approach. In the study by van Wijngaarden (2011), a potential flow boundary element method (BEM) with measured hull pressure data as input was applied to solve the hull pressure fluctuations, and the model experiments were also carried out. It was concluded that the computed hull pressure fluctuations due to non-cavitating propellers is reasonably accurate compared with the experimental data. Kehr and Kao (2011) calculated the pressure fluctuations on ship hull due to propeller sheet cavitation by using the method presented in Kao and Kehr (2006). The numerical result is higher than the experimental data provided by the hydrodynamics and cavitation tunnel (HYKAT) of HSVA (Wiemer 1999) by approximately 27%. The pressure fluctuations on ship stern induced by cavitating propellers were solved by Kanemaru and Ando (2011) with a surface panel method. The maximum amplitude appears in the first blade frequency and overestimates the experimental data by about 30%. Kim et al. (2012) predicted the hull pressure fluctuations induced by marine propeller sheet cavitation, and the Doppler effect was considered at the same time. Wei and Wang (2013) employed CFD to simulate the propulsion of a submarine. The finite element method and BEM were then combined to solve the submarine's structure and acoustic responses under the propeller excitations. The matched-field inversion technique applied in Lee et al. (2014) uses the fluctuating hull pressure field measured by receivers and the acoustic field calculated by BEM to define the sheet cavitation noise, source strengths, source positions, and number of sources. The equivalent source model for the propeller can result in more accurately extrapolated hull pressure distribution. In Wei et al. (2016), the unsteady forces of a submarine propeller were predicted by CFD, and the hull pressure fluctuations due to the non-cavitation propeller were calculated by the method proposed in Kao and Kehr (2006).

Ultimate strength of cracked ship structural elements and systems: A review

Abstract Many ships around the world are getting older. As the ships grow older, more defects such as cracks will come up exposing the ship hull structure to structural failures. Although many investigations have been carried out on the ultimate strength of cracked ship structural elements, there is a gap in design phase of a ship hull structure accurately considering such defects. In particular, available manuscripts by the regulatory bodies simply deal with the repair methods rather than practical design codes and guidelines. Many researchers have employed different methods to investigate ultimate strength of cracked ship structural elements to understand effects of various parameters. But as there is not a benchmark study to be referenced as a standard, sometimes contrasts are observed in the investigations. This paper presents a detailed review on the effects of different crack parameters such as crack length, crack location, crack orientation and gap size, plate thickness, aspect ratio, boundary conditions on the ultimate strength of ship hull elements in a comparative manner to be used as a reference for future investigations.

Response and fatigue assessment of high speed aluminium hulls using short-term wireless hull monitoring

This paper proposes a wireless hull monitoring system that is quick to install as a short-term monitoring solution. Hull measurements have the potential to increase the accuracy of ship response predictions at a lower cost than computer simulation or towing tank models. The performance of the wireless monitoring system is validated on the all-aluminium United States Coast Guard Response Boat-Medium. The system is designed to measure ship motions and hull strain responses during high-speed operations and in harsh weather conditions. An analytical framework is developed to extract sea states from inertial measurements recorded at the ship centre-of-gravity and in a bow compartment. To assess the fatigue life of the hull during harsh weather operations, response amplitude operators (RAOs) are empirically derived to map sea states to root mean square accelerations and strain cycles measured from a high-stress hull element. A RAO that maps sea state to consumed fatigue in the hull, so termed a consumed fatigue operator (CFO), is presented which can assist in the management of an asset over its life cycle. The study reveals reliable hull monitoring during a one-week sea trial. RAO and CFO fit to hull response data are proven to provide accurate estimates.

Estimating the strength of welded hull elements of a submersible based on the micromechanical model of temporal dependences of acoustic-emission parameters

A nondestructive technique for evaluating the strength of hull elements of submersibles is described. The technique is based on the micromechanical model of temporal dependences of the parameters of acoustic emission that is registered under an original novel technique of loading of a cylindrical hull section. The technique is also suitable for assessing the information value of resource-related acoustic-emission diagnostic indicators.

Laser Doppler Vibrometer Based Examination of the Efficiency of Introducing Artificial Delaminations into Composite Shells

Abstract During its operation, the laminate shell of the watercraft hull can be exposed to local stability losses caused by the appearance and development of delaminations. The sources of these delaminations are discontinuities, created both in the production process and as a result of bumps of foreign bodies into the hull in operation. In the environment of fatigue loads acting on the hull, the delaminations propagate and lead to the loss of load capacity of the hull structure. There is a need to improve diagnostic systems used in Structural Health Monitoring (SHM) of laminate hull elements to detect and monitor the development of the delaminations. Effective diagnostic systems used for delamination assessment base on expert systems. Along with other tools, the expert diagnostic advisory systems make use of the non-destructive examination method which consists in generating elastic waves in the hull shell structure and observing their changes by comparing the recorded signal with damage patterns collected in the expert system database. This system requires introducing certain patterns to its knowledge base, based on the results of experimental examinations performed on specimens with implemented artificial delaminations. The article presents the results of the examination oriented on assessing the delaminations artificially generated in the structure of glass- and carbon-epoxy laminates by introducing local non-adhesive layers with the aid of thin polyethylene film, teflon insert, or thin layer of polyvinyl alcohol. The efficiency of each method was assessed using laser vibrometry. The effect of the depth of delamination position in the laminate on the efficiency of the applied method is documented as well.

Interaction of breaking waves with plates: The effect of hull cavitation

The cavitation aspect of the transient interaction of a vessel hull with extreme breaking waves is considered. The authors show that the elastic deformation of thin hull elements by a short water-wave pressure pulse can be accompanied by hull cavitation. The effect of this cavitation is important if the duration of loading by the water pressure is less than the period of the fundamental frequency of the hull element oscillation, and is shown to increase the magnitude of the loading.

Discrete element modeling of ice loads on ship hulls in broken ice fields

Ice loads on a ship hull affect the safety of the hull structure and the ship maneuvering performance in ice-covered regions. A discrete element method (DEM) is used to simulate the interaction between drifting ice floes and a moving ship. The pancake ice floes are modelled with three-dimensional (3-D) dilated disk elements considering the buoyancy, drag force and additional mass induced by the current. The ship hull is modelled with 3D disks with overlaps. Ice loads on the ship hull are determined through the contact detection between ice floe element and ship hull element and the contact force calculation. The influences of different ice conditions (current velocities and directions, ice thicknesses, concentrations and ice floe sizes) and ship speeds are also examined on the dynamic ice force. The simulated results are compared qualitatively well with the existing field data and other numerical results. This work can be helpful in the ship structure design and the navigation security in ice-covered fields.