Anchor Chain Research Articles

Morphological evolution and mechanical properties of an “anchor chain” nanodomain structure of a reactive amphiphilic triblock copolymer in epoxy resin

A epoxy-reactive poly(3,4-epoxycyclohexylmethyl methacrylate)-block-poly(dimethylsiloxane)-block-poly(3,4-epoxycyclohexylmethyl methacrylate) (PMETHB-b-PDMS-b-PMETHB) triblock can self-assemble in epoxy resin to form “anchor-chain” nanodomains.

Numerical investigations of the effect of strain softening on the behaviour of embedded mooring chains

Mooring systems typically consist of an anchor and a mooring line and chain that connect the anchor to the floating infrastructure. When the anchor connection point (the ‘padeye’) is below the seabed surface, the interaction between the chain and the seabed will affect the amount of load transferred to the anchor and the load angle at the padeye. Reliable methods are needed therefore to assess these aspects in order to determine appropriate anchor design.Available solutions for the interaction between soil and chain generally ignore any reduction in the undrained shear strength of the soil as it is remoulded under the large strains associated with tensioning of the anchor chain. This is an unconservative assumption for anchor design, hence providing motivation for the study presented here. The system behaviour and the interaction of short chain segments with the seabed have been studied using a coupled Eulerian-Lagrangian (CEL) approach. The findings have led to two new design approaches that encapsulate how remoulding of the soil (which affects sliding resistance more than bearing resistance) affects the chain system response. Calculations using these methods captured the modelled chain system response well. Both the global chain analyses and the proposed design approaches suggest that approximately the entire chain load at the seabed surface (the ‘mudline’) is likely to be transferred to the anchor padeye, challenging conventional design practice.

Loading performance of fish and OMNI-Max anchors in crust-over-soft clays

This paper reports the results from three-dimensional dynamic finite element analysis undertaken to provide insight into the behaviour of the fish and OMNI-max dynamically installed anchors during loading in crust-over-soft clay sediments. Particular attention was focused on the situations where the anchor is embedded to a shallow depth during dynamic installation due to the strong crust layer. Large deformation finite element analyses were carried out using the coupled Eulerian-Lagrangian approach, incoporating the anchor chain effect. Parametric analyses were undertaken varying the initial embedment depth, anchor shape, loading angle, strength ratio between the top and bottom layers. The tracked anchor trajectory confirmed that the diving potential of the fish and OMNI-Max anchors were enhanced by the presence of the crust layer as that somewhat restircted the upward movement. This will be beneficial for many hydrocarbon active regions with layered seabed sediments where the anchor embedment depths during dynamic installation are expected to be low.

Design and research on optimization of single point mooring system

In this paper, we establish a statics model to analyze the force balance of the buoys, four steel pipes and steel buckets, and we derive the relationship between the inclination angle of steel pipes and steel buckets and the draught depth and wind speed, which is solved by moment in mechanics. Next, by applying the catenary curve’s equation to per unit of anchor chain, we can obtain the vertical height of anchor chain, thus the total depth of sea water can be obtained. Finally, the variable step search algorithm is used to search the draught depth, and we can obtain each parameter of the optimization result.

Getting external load characteristics of the axle-box generator

This article addresses the problem of supplying freight railcars. It is about the axle-box generator. The generator uses to power the on-board electronics. The design feature consists in the fact that the generator is installed to the generator’s axle-box and, as a result, it has increased requirements for the weight and size indications. The generator was designed with an external rotor due to the limited space, since the rotor acts as an inductor. The inductor is made of permanent magnets. The stator is made of laminated electrical steel in the six-pointed star form. The winding is made of copper conductor with a cross-sectional area of 0.2 mm2. Characteristics are presented in the form of waveforms and graphs. During the experiment, a number of oscillograms were taken and harmonics were counted. Voltage were also measured at different loads and rotation speeds. The obtained power at an average speed of 30 km/h was 4 W, and at a speed of 80 km/h it was 6.3 W. The method for determining the parameters of the anchor chain equivalent circuit is given.

Numerical Study of Mobilized Friction along Embedded Catenary Mooring Chains

Understanding the soil resistance along an embedded anchor chain is imperative for efficient and economic design of an overall mooring system as it determines the magnitude and direction of the load at the padeye of the anchor. The tensioning process of an embedded chain for catenary moorings was modeled using a coupled Eulerian–Lagrangian (CEL) finite-element approach simulating the large deformations of the chain as it cuts through the soil to form an inverse catenary. The analyses reveal that the configuration of the embedded chain and the relationship between tension and chain angle at the padeye show excellent agreement with previously published analytical predictions. However, the ratio of the tension at the padeye to that at the mudline obtained from CEL is significantly higher than the theoretical values, mainly due to partial mobilization of the frictional soil resistance along the length of the chain. The CEL results indicate that the partial mobilization is a result of the combined-loading effect during failure of the soil around the embedded chain as it cuts through the seabed, in contrast with the conventional assumption that the ultimate frictional and normal soil resistances are mobilized simultaneously. A new design approach is proposed for calculating the local equivalent coefficient of friction based on the yield locus for a deeply embedded chain and the normality rule.

Research and development of on-line measuring device for anchor chain length

In order to realize the automatic online measurement of the anchor chain length, this paper proposes a measuring device with simple structure and high measurement accuracy. According to the structural characteristics of the existing anchor chain tensile testing machine, the structure spliced with AL plates is designed and it has good mechanical properties. The measurement method combining the laser ranging sensor, the laser sensor and the magnetic grid sensor realizes the on-line measurement of the anchor chain length and effectively improves the measurement accuracy. The platform has been successfully installed in Zhoushan, China.

Multi-sensor Data Fusion for Online Quality Assurance in Flash Welding

Abstract The flash welding process is a mainstream to manufacture anchor chains in the shipbuilding industry. However, traditional quality control approaches only use the tension test of the whole chain. This cannot adequately guarantee the quality of each anchor chain. Also, the incurred cost of post-build repair is far more than production. There is an urgent need to design and develop new quality control methods for real-time monitoring and control of flash welding processes. In this investigation, we firstly develop a data acquisition and control system to collect sensor data pertinent to process dynamics (i.e., electrode-position and electric-current profiles) and monitor the flash welding process in real time. Then a novel spatiotemporal warping approach is proposed to quantify the dissimilarity of electric-current and electrode-position signals collected in the flash welding process. Further, we embed the resulted warping matrix into feature vectors in the low-dimensional space that preserves the dissimilarity distances. Finally, Dirichlet Process (DP) models are proposed to cluster embedded features (coordinates in low-dimensional space). Experimental results demonstrated that the proposed methodology not only effectively reveals the directional differences among flash welding profiles, but also significantly outperforms traditional clustering algorithms such as the K-means approach, i.e., 13.25%, 1.67% and 12.33% increases in the prediction performance with the use of electric-current, electrode-position and combination recordings, respectively.

Numerical study of a well boat operating at a fish farm in current

Dynamic response of a well boat operating at a fish farm in current is investigated numerically. An objective is to determine the operational conditions of the well boat. In terms of the fish farm, a realistic set-up (with single cage) is considered, including a floating collar, an elastic sinker tube, a flexible-closed net cage and a complex mooring system. A time-domain solution is used to find the steady configuration and response. Transverse viscous current loads are estimated using the cross-flow principle. The drag coefficients are obtained empirically by considering cross-sectional details, free surface and three-dimensional (3D) flow effects. The drag force is experimentally validated. The effect of the ship wake on the net loading is also assessed.The most critical scenario with the well boat placed at the weather side of the fish farm is analyzed in detail. Critical response variables for operational limits are the maximum anchor-line tensions and floater stresses. Numerical results show that the anchor loads will increase more than 40% in small current velocities and up to 90% in high current velocities due to the viscous current loads on the boat. There is also a strong increase of the floating collar deformations and stresses when the well boat is in contact with the floating collar.A sensitivity analysis has been carried out to identify the physical parameters affecting the anchor loads and the maximum stress in the floating collar. From our studies, the anchor loads are more sensitive to current direction, bottom weight system, sinker tube depth and mooring line properties (pretension load, anchor chain weight, etc.) and less sensitive to other parameters such as floating collar stiffness and cross-sectional drag coefficients of the well boat. The shading effect of the well boat on the fish-farm inflow has been examined and appeared not negligible with 4% to 10% reduction of the anchor loads for the studied current conditions. The maximum stress in the floating collar is sensitive to well-boat loads related parameters (current direction, cross-sectional drag coefficient) and pretension load in the anchor line; not so sensitive to net loading related parameters such as sinker tube depth and sinker tube weight.Lastly, the operational conditions of the well boat at the fish farm were discussed. Numerical results show that the maximum stresses in the floating collar should be of major concern. The loads in the mooring lines are moderate compared with the corresponding breaking limits.

Simulation of Mixed Self-Assembled Monolayers on Gold: Effect of Terminal Alkyl Anchor Chain and Monolayer Composition

Self-assembling monolayers provide a reproducible synthetic microenvironment for tethering lipid bilayers to incorporate proteins and lay the ground for numerous applications in nanotechnology and biomedical engineering. Although the structure of single-component monolayers is well investigated, there is far less insight into the molecular behavior at the interface of mixed monolayers at different mole fractions. Here, we present and apply a novel procedure to simulate and analyze multicomponent self-assemblies of alkanethiols over a wide range of mole concentrations of anchoring compounds. In particular, the structural features of monolayers consisting of a matrix compound and either a short (C8) or a long (C16) anchor compound on Au(111)-like surfaces were investigated first using coarse-grained and subsequently full-atomistic molecular dynamics simulations. Different scenarios of spatial distributions (random vs clustering) of anchoring molecules on flat surfaces were probed. The results of the simulations are in excellent agreement with the experimental data from ellipsometry and infrared reflection absorption spectroscopy. For short anchoring molecules, a random spatial distribution in the matrix is obtained. At low, experimentally relevant anchor compound mole fractions < 0.1, only for long-chain (C16)-terminal alkyls, phase segregation and self-association of the anchoring molecules can be observed, which are also seen in experiment.

Numerical Investigation of Large Nonpowered Ships Anchor Chain Mooring Force in Extreme Offshore Environment

Nonpowered vessles can’t self-propelled and initiative resist wind and stream. Single point buoy mooring system is one of effective ways for nonpowered vessle to mooring in extreme offshore environment. Based on wind, flow and wave model, the bow anchor mooring force model can be achieved. Through compared with physical model test data, the scientificity and rationality of the mathematical anchor chain mooring force model of single point buoy is verified. Then the design of nonpowered vessle buoy engineering is analyzed by the means of single point buoy mooring system mathematical model.

Numerical investigations of the effects of different design angles on the motion behaviour of drag anchors

The factors that may influence the motion behaviour of drag anchors include drag velocity, shape and density of the drag anchor, length of the anchor line, etc. This paper presents a coupled Eulerian-Lagrangian (CEL) model of both an anchor and its chains to simulate the installing processes of drag anchors. The comprehensive anchor behaviours including the variations of anchor trajectory, movement direction, drag angle and drag force at the shackle of drag anchors with various design angles are presented. The numerical results agree well with both existing FE results and theoretical solutions. Fitting equations describing the anchor motion behaviours are proposed. The effects of the values of the bearing capacity factor and the ratio between tangential and normal soil resistances of the anchor chains, when deriving theoretical solution of drag forces, are discussed. The influence of the friction coefficient of the chains is also analysed.

Analysis of AISI 304 Tensile Strength as an Anchor Chain of Mooring System

The background of this research is the use of mild steel (i.e., St37) as anchor chain that works on the corrosive environment of seawater which is possible to decrease its tensile strength. The longer soaked in seawater, the more significant the lowering of its tensile strength. Anchor chain needs to be designed by considering its tensile strength and corrosion resistance, so it’s able to support mooring system well. The primary purpose of this research is obtaining the decreasing of stainless steel 304 (AISI 304) tensile strength which is corroded by seawater as anchor chain of the mooring system. It is also essential to obtain the lifetime of AISI304 and St37 as anchor chain with the same load, the corrosion rate of AISI 304, and St 37 in seawater. The method which was employed in this research is an experiment with four pieces of stainless steel AISI 304, and of St 37 corrosion testing samples, six pieces of stainless steel 304, and six pieces of St 37 for tensile testing samples. The result of this research shows that seawater caused stainless steel AISI 304 as anchor chain has decreased of tensile strength about 1.68 % during four weeks. Also, it indicates that AISI 304 as anchor chain has a lifetime about 130 times longer than St 37. Further, we found that the corrosion rate of stainless steel 304 in seawater is 0.2042 mpy in outstanding category, while the St 37 samples reached up to 27.0247 mpy ranked as fair category. This result recommends that AISI 304 more excellence than St 37 as anchor chain of the mooring system.

Design of Single-Point Mooring System with Moored Buoy

The single-point mooring system is currently under a wide range of applications in marine engineering, marine observation, marine farming and other engineering fields. So this paper intends to investigate into the singlepoint mooring system with moored buoy that is made up of a buoy, four steel pipes, a steel drum, a heavy ball, an anchor chain and an anchor. The aim here is to design a single-point mooring system mentioned above, which can be used off shore. Namely, the following parameter values have to be determined: the type and length of chain, the mass of compact ball, such that do not only both the buoy draught and the moving range, but also the vertical angle of steel drum reach as small as possible. For the above purpose, firstly, analyse each component of this system by means of the static force method. Secondly, establish a mathematical model to calculate under the different wind speeds all the important parameters, including the vertical tilt angle of the steel drum, the horizontal tilt angle of each steel pipe, the buoy draught, the buoy moving range and the chain shape. Thirdly, on the basis of the above work, a multi-objective programming model is established to obtain the design schemes in the diverse environmental conditions involving wind speed, seawater velocity and sea depth. Finally, by simulation it has turned out that these design schemes obtained above are reasonable and applicable. Therefore, they have definite theoretical significance and practical values.

Failure analysis of a failed anchor chain link

Abstract The failure of a metal chain link with stud during an anchoring operation of a ship is examined. Visual observation, optical and scanning electron microscopy analyses of the fracture surfaces in combination with hardness and tensile tests are used to establish the cause of failure. The chemical element composition, tensile strength, yield strength and elongation of the base metal of the chain link are within the recommended design values. However, cross-sectional microstructure examination revealed that the fracture occurred along the flash butt weld and initiated from a pre-existing edge radial crack on the outer surface which had been painted over. The presence of inclusions near the outer surface, decarburized boundaries of the inclusions and a decarburized thin strip along the entire weldment had resulted in weldment strength reduction and subsequent initiation of the surface crack. The main cause of the chain link failure is improper flash welding and heat treatment resulting in localised carbide segregations and embrittlement, leading to initiation of surface crack and consequent overload of the remaining net-section area of the chain. There was no evidence of fatigue crack growth. Better inspection and maintenance would have led to early detection of the surface crack during any the periodic non-destructive testing.

Reliability assessment of drag embedment anchors in clay for catenary mooring systems

Drag embedment anchors are attractive anchoring solutions, which are widely used for temporary and permanent station keeping of floating structures. The number of floating facility incidents related to mooring system failure continues to raise concerns in the industry in general. This necessitates the reliability assessment of mooring components and their contribution to system integrity. The reliability of drag embedment anchors as a key component of popular mooring systems has never been explored before due to the high complexity of anchor-soil interaction and extensive inherent uncertainties. In this paper, the reliability of drag anchors for catenary mooring lines was investigated with attention to the seabed condition and environmental loads. The probabilistic modelling of anchor capacity was conducted using plastic yield loci to characterize the fluke-soil interaction and failure states. The embedded profile and the frictional capacity of the anchor chain at the seabed were also considered in the calculation of ultimate holding capacity. The uncertainties of the environmental loads, metocean variables, and consequently the stress distribution throughout the catenary lines were accounted for using the response surface method. First order reliability method (FORM) was used through an iterative procedure to obtain the probabilistic failures. The results show an acceptable level of reliability for these anchor families and reveal its sensitivity to key components of anchor geometry.

Analysis of dynamic response of a restraining system for a powerless advancing ship based on the Kane method

Following general explanations of the working principles of different existing retardation systems to restrain an advancing powerless ship the principles of a new overhead retardation system are presented. A two dimensional simplified model of the activated overhead system is formulated based on Huston’s interpretation of the Kane methodology. Reduced Kane equations are used in the actual simulation, once initial conditions and mechanical analysis of constituent elements have been formulated. Having presented the computational process the various velocity, motion and joint constraint force characteristics of the anchor, the ship and the other elements are monitored in the time domain for the duration of the retardation process. Validation of the Kane based method is established utilising the conservation law and the Lagrangian based formulation of the retardation system within the ADAMS software. The results indicate that a peak value of constraint will occur because of the sudden movement of anchor and this peak is affected significantly by initial ship speed. Variation in anchor chain, overall cable length and its horizontal projected length has little influence upon retardation system performance, whilst the changes of sea bed friction, anchor mass, water depth, initial ship velocity and ship mass will make retardation behaviour different.

基于悬链线方程的系泊系统状态分析

根据调整锚链的型号、长度和重物球的质量，确定浮标的吃水深度和游动区域及钢桶的倾斜角度的极小值。本文分为两个部分对系泊系统的设计作系统的研究。首先，在考虑单一参数变化的情况下，运用隔离法依次对传输节点的各个结构进行受力分析，其中，锚链可近似看成一条悬链线，利用泰勒级数展开进行公式处理。其次，在综合考虑风力、水流力和水深的情况下，由力和力矩的平衡条件建立模型，确定出锚链型号、长度、重物球的质量，并分析求解不同参数变化下钢桶、钢管的倾角，锚链形状，浮标的吃水深度和游动区域。最后，运用MATLAB对各个非线性方程组编写算法以及提供图形描述，并对整个模型进行了合理性检验与客观的优缺点评价，以及在其他领域的推广使用，并提出了在受力分析上的改进，提高了模型的实用性与现实性。 According to adjusting the type and length of the anchor chain model, and mass of the ball, the draft depth and moving area and the minimum value of the inclined angle of the buoy are determined. This article is divided into two parts to make a systematic study on the design of mooring system. Firstly, in the case of single parameter change, using the method of isolation to make the force analysis towards each structure of the transmission node in turn, the anchor chain can be regarded as a catenary, and Taylor series expansion is used for formula processing. Secondly, in the comprehensive consideration of the balance conditions of wind, drag force and water depth, the balance conditions of force and torque are established to determine the type of anchor chain model, length and weight of the ball, and analyze the tilt angle of steel drum and steel pipe, anchor’s shape, and draft depth and moving area of buoy under different parameters. Finally, using MATLAB to write algorithm of each nonlinear equations and provide graphic description, and has carried on the reasonable test and objective advantages and disadvantages evaluation about whole model, and the promotion in other areas, and has put forward the improvement on stress analysis, improve the practicability and reality of the model.

基于非线性有限元方法的单点系泊系统的优化设计研究

本文基于静力学原理，对系泊系统中的六个大部件进行了局部与整体的受力分析。列出了一系列物理学方程。并最终推导出了系泊系统的非线性微分方程模型。方程采用迭代法进行求解。根据锚链的结构，采用有限元方法中对应的结构方法。运用了非线性有限元方法进行计算，得出系泊系统的锚链方程。计算出锚链系统无抬升角限制的边界条件。对锚链进行了受力分析。使锚不会被轻易拖移，并且使钢桶尽量保持竖直的条件。找到了在风力、水流力的影响下，钢桶、钢管的倾斜角度、锚链形状、浮标的吃水深度和游动区域，以确保使系统稳定的条件。 Based on the principle of statics, this paper analyzes the force analysis of six large parts in mooring system. A series of equations of physics are listed. Finally, we derive the nonlinear differential equation model about mooring system, which is solved by iterative method. According to the structure of anchor chain, the corresponding structure method of finite element method is adopted. By using the nonlinear finite element method, this paper obtains the anchor chain equation of mooring system. To calculate the mooring system without lifting angle limit boundary condition, we analyze the stress of anchor, which cannot be dragged easily, and we try to keep the condition of vertical steel drum. We find the influence of wind power, water power, steel pipe, angle, shape, anchor buoy and draught of the swimming area, to ensure the stable condition of the system.

Friction Surfacing Of Aluminium on Steel: An Experimental Approach

Friction surfacing is a solid-state technology for producing metallic coating. Application of friction surfacing is reported for short run includes repair of steam turbine blades, which has very high replacement cost. In addition to deposition of hard metal to increase wear and corrosion resistance of agriculture and oil components, repair of anchor chains, repair of surface defects and worn areas on rail tracks reported so far.During present investigation consumable rod of aluminium 6351 T6 of various diameters like 8mm, 12mm, 16mm & 22mm were investigated for 6mm thick steel substrate. It was found metallic coating produced using 22mm rod is excellent based on visual appearance. Additionally ring forms at the end of the rod after deposition was also recorded. Temperatures were measured using data logger on advancing and retreating sides. Pick temperature reported on advancing side (421 °C) is higher than retreating side (375 °C). Finally sample subjected to Vickers macro hardness measurements.Experimental work explores the commercial viability of the process in the field of corrosion protection area.