轴向载荷作用下管状TY接头几何参数对应力集中系数的影响分析（英文）

In this paper, the influence of geometric parameters on the stress concentration factors due to three different types of axial loading on 81 TY tubular structures is studied. Our results reveal that, geometric parameters have a considerable impact on the variation of stress concentration factors on tubular TY-joints under axial loads. Thus, the highest stress concentration factor values are observed on the vertical brace than on the inclined one. The finite element results of the tubular structu...     

Dynamic anti-plane interaction between an impermeable crack and a circular cavity in an infinite piezoelectric medium

Wave propagation in an infinite elastic piezoelectric medium with a circular cavity and an impermeable crack subjected to steady-state anti-plane shearing was studied based on Green's function and the crack-division technique.Theoretical solutions were derived for the whole elastic displacement and electric potential field in the interaction between the circular cavity and the impermeable crack.Expressions were obtained on the dynamic stress concentration factor(DSCF) at the cavity's edge,the dynamic stress intensity factor(DSIF) and the dynamic electric displacement intensity factor(DEDIF) at the crack tip.Numerical solutions were performed and plotted with different incident wave numbers,parameters of piezoelectric materials and geometries of the structure.Finally,some of the calculation results were compared with the case of dynamic anti-plane interaction of a permeable crack and a circular cavity in an infinite piezoelectric medium.This paper can provide a valuable reference for the design of piezoelectric actuators and sensors widely used in marine structures.     

双平面焊接圆管截面DKT节点的中心撑杆鞍点及冠点位置的应力集中系数(英文)

A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions.The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors(SCFs) at the inner saddle,outer saddle,and crown positions on the central brace.Based on results of finite element(FE) analysis and through nonlinear regression analysis,a new set of SCF parametric equations was established for fatigue design purposes.An assessment study of equations was conducted against the experimental data and original SCF database.The satisfaction of acceptance criteria proposed by the UK Department of Energy(UK DoE) was also checked.Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties.It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results.Hence,it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints.Good results of equation assessment according to UK DoE acceptance criteria,high values of correlation coefficients,and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations.Therefore,the developed equations can be reliably used for fatigue design of offshore structures.     

Dynamic anti-plane interaction between an impermeable crack and a circular cavity in an infinite piezoelectric medium

Wave propagation in an infinite elastic piezoelectric medium with a circular cavity and an impermeable crack subjected to steady-state anti-plane shearing was studied based on Green＇s function and the crack-division technique. Theoretical solutions were derived for the whole elastic displacement and electric potential field in the interaction between the circular cavity and the impermeable crack. Expressions were obtained on the dynamic stress concentration factor （DSCF） at the cavity＇s edge, the dynamic stress intensity factor （DSIF） and the dynamic electric displacement intensity factor （DEDIF） at the crack tip. Numerical solutions were performed and plotted with different incident wave numbers, parameters of piezoelectric materials and geometries of the structure. Finally, some of the calculation results were compared with the case of dynamic anti-plane interaction of a permeable crack and a circular cavity in an infinite piezoelectric medium. This paper can provide a valuable reference for the design of piezoelectric actuators and sensors widely used in marine structures.     

不规则响应产生的非粘结柔性立管螺旋条带应力分析（英文）

A helical wire is a critical component of an unbonded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment–curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.     

The solution of minimum reliability arbitrary curved beam index for modified weak point of under pure bending

This paper is based on the fundamental loading model of pure bending and the analytical model of a circular beam element with arbitrary initial deflection. The L.W. Guo solution is modified and generalized according to the elastic theory, and the analytical solution for the stress of the beam element with arbitrary initial deflection under pure bending is derived. Using yield theory of edge strength, an expression for the safety margin of one point in the arbitrary curved beam under pure bending （ACPB） is built. This paper modifies the model for weak points of service structures and establishes a foundation for safe design and inspection of imperfect structures. Also, according to the theory of the method of advanced first-order second-moment（AFOSM） , this paper derives an expression for the reliability index of one point in ACPB. Lastly, it modifies the solution for weak points by solving the minimal reliability index.     

集束塔式立管总体强度分析(英文)

Bundled hybrid offset riser (BHOR) global strength analysis, which is more complex than single line offset riser global strength analysis, was carried out in this paper. At first, the equivalent theory is used to deal with BHOR, and then its global strength in manifold cases was analyzed, along with the use of a three-dimensional nonlinear time domain finite element program. So the max bending stress, max circumferential stress, and max axial stress in the BHOR bundle main section (BMS) were obtained, and the values of these three stresses in each riser were obtained through the "stress distribution method". Finally, the Max Von Mises stress in each riser was given and a check was made whether or not they met the demand. This paper provides a reference for strength analysis of the bundled hybrid offset riser and some other bundled pipelines.     

17000载重吨油船结构疲劳分析的快速估算方法(英文)

Fatigue cracks and fatigue damage have been important issues for ships and offshore structures for a long time.However,in the last decade,with the introduction of higher tensile steel in hull structures and increasingly large ship dimensions,the greater attention should be paid to fatigue problems.Most research focuses on how to more easily access the fatigue strength of ships.Also,the major classification societies have already released their fatigue assessment notes.However,due to the complexity of factors influencing fatigue performances,such as wave load and pressure from cargo,the combination of different stress components,stress on concentration of local structure details,means stress,and the corrosive environments,there are different specifications with varying classification societies,leading to the different results from different fatigue assessment methods.This paper established the Det Norske Veritas(DNV) classification notes "fatigue assessment of ship structures" that explains the process of fatigue assessment and simplified methods.Finally,a fatigue analysis was performed by use data of a real ship and the reliability of the result was assessed.     

船用螺旋桨叶片应力的数值分析（英文）

In this study, a series of numerical calculations are carried out in ANSYS Workbench based on the unidirectional fluid–solid coupling theory. Using the DTMB 4119 propeller as the research object, a numerical simulation is set up to analyze the open water performance of the propeller, and the equivalent stress distribution of the propeller acting in the flow field and the axial strain of the blade are analyzed. The results show that FLUENT calculations can provide accurate and reliable calculations of the hydrodynamic load for the propeller structure. The maximum equivalent stress was observed in the blade near the hub, and the tip position of the blade had the largest stress. With the increase in speed, the stress and deformation showed a decreasing trend.     

Asymptotic field of mode Ⅱ dynamic growing crack in visco-elastic material

A mechanical model of visco-elastic material is established in order to investigate viscous effect in dynamic growing crack-tip field of mode Ⅱ. It is shown that in stable creep growing phase, elastic deformation and viscous deformation are equally dominant in the near-tip field, the stress and strain have the same singularity, namely, (σε) ∝r^-1/(n-1). The asymptotic solutions of separatied variables of stress, stain and displacement in crack-tip field are obtained by asymptotic analysis, and the results of numerical value of stress and strain in crack-tip field are obtained by shooting method. Through numerical calculation, it is shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M. By the asymptotic analysis to the crack-tip field, the fracture criterion of mode Ⅱ dynamic growing crack of visco-elastic materials is put forward from the point of view of strain.     

在海上航运中用于位置感知管理和控制系统的可重用C++类的开发(英文)

Location aware management and location based automation are fast upcoming technologies which are facilitated by availability of reliable, accurate, and cheap global positioning systems and location based services. This paper discusses the development of C++ classes, which may be used for development of software for location aware management and control, specifically in merchant shipping, so as to provide improved safety, increased automation, prevention of pollution and reducing the work burden of the crew. The GPS is used in conjunction with the regionally accessible nested global shorelines (RANGS) dataset for this purpose. The design of two main C++ classes named CShorelines and CGPSInput have been discussed. A control system mandatory on all oil-tankers above 150 GRT (and few other vessels) called ODMCS has been made location aware using the novel software developed and the results obtained have been critically examined and presented.     

The asymptotic field of a dynamically growing crack in a viscoelastic materia

A mechanical model of a fracturing viscoelastic material was developed to investigate viscous effects in a dynamically growing crack-tip field. It was shown that in the stable creep-growing phase,elastic deformation and viscous deformation are equally dominant in the near-tip field,and stress and strain have the same singularity,namely,(σ,ε ) ∝ r?1 /( n?1) . The asymptotic solution of separating variables of stress,stain and displacement in the crack-tip field was obtained by asymptotic analysis,and the resulting numerical value of stress and strain in the crack-tip field was obtained by the shooting method and the boundary condition of a mode I crack. Through numerical calculation,it was shown that the near-tip fields are mainly governed by the creep exponent n and Mach number M . When n →∞,the asymptotic solution of a viscoelastic material can be degenerated into that of Freund's elastic-ideally plastic material by analyzing basic equations.     

Finite element simplified fatigue analysis method for a non-tubular joint of an offshore jacket platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analysis, post-process stress results for acquiring the stress range, and perform fatigue evaluation. The analysis results indicate that the extreme stress range is within the allowable stress range and meets the requirements of DNV code. That means the simplified fatigue analysis method is effective and can be used in fatigue design for the non-tubular joint structure of an offshore jacket.     

Research on vibration characteristics of L-shaped plate using a mobility power flow approach

L-shaped plates have become an important focuses in structural vibration research. To determine their vibration characteristics, this paper applied a mobility power flow method. Firstly, the L-shaped plate was divided into two substructures to simplify analysis. The coupled bending moment was then deduced by applying a continuous vibration property on the common edge. Next, the response on any point of the plate and the input and transmitted power flow formulas were calculated. Numerical simulations showed the distribution of the coupled bending moment and the response of the whole structure. The validity of this method was verified by the SEA approach.     

Numerical simulation of the anti-shock performance of a gear case

Both sea battles and testing of ship in underwater explosions reveal unacceptably poor anti-shock performance of important shipboard equipment. Anti-shock performance of shipboard equipment is a significant factor determining fighting strength and survivability. The anti-shock performance of a shipboard gear case based on BV043/85 was investigated using numerical simulation. A geometric model of the gear case was built using MDT software and meshed in HyperMesh software, and then the finite element model of the gear case was formed. Using ABAQUS software, the anti-shock performance of the gear case was simulated. First, shock response of typical regions of gear case was determined. Next, some generalizations were made about the anti-shock performance of the gear case by analyzing the Mises stress of typical regions varied with shock inputs. Third, weak regions were determined from simulation results. The threshold values of shock resistance of the gear case at different impulse widths were obtained through interpolating the numerical simulation results selected from the most dangerous spot. This research provides a basis for further optimization of the design of gear cases.     

Ship resistance in random ice field of small ice floes made of the substitute material北大核心CSCD

［Objectives］This study focuses on the feasibility of a ship resistance model test in an ice field of small ice floes made of substitute material in order to reveal the resistance components and thereby provide technical support for the design of ice-going ships. ［Methods ］ Ship resistance test in ice floes made of polypropylene (PP) instead of natural refrigerated ice is conducted. By adjusting the sizes, shapes, numbers of ice floes, the random ice field with a given concentration is generated. The geometric phase transition theory predicts that there exists a critical concentration which divides the random ice field into discrete phase (concentration is less than critical value) and connected phase (concentration is greater than critical value). ［Results］The main components of ice resistance in the discrete phase are open water resistance and ship-ice collision resistance, while ice resistance in the connected phase includes ice friction resistance, open water friction resistance and collision resistance. If the fractal dimension of the random ice field is used to redefine the ice resistance coefficient, it is nearly constant in the trial range (speed 0.3–0.9 m/s) when the concentration is smaller than the critical value. When the concentration is greater than the critical value, the ice friction resistance is inversely proportional to speed. ［Conclusions］Polypropylene can replace frozen ice in the prediction of ice resistance. The pure ice resistance of an ice field is divided into two components: ice resistance arising from collision and ice friction resistance arising from accumulation. © 2022 Journal of Clinical Hepatology. All rights reserved.     

STATE OF WASHINGTON OFFICE OF THE GOVERNOR Message from the Governor

I am pleased to send my best wishes to the China Ocean Shipping Company (COSCO) as it celebrates 20 years of friendship and successful trade relations between the United States and the People's Republic of China on this 20th anniversary of the maiden voyage of the vessel M.V. LIULINHAI. Much has happened in the 20 years since U.S. trade with China was reinstated in 1979, and China has grown to become an important partner in Washington's Asia-Pacific trade relationship. Washington's status as the most trade-dependent state in the nation and our geographic location on the edge of the Pacific Rim dictate that     

采用微气泡缩减高速船拖曳阻力(英文)

Ship hull form of the underwater area strongly influences the resistance of the ship.The major factor in ship resistance is skin friction resistance.Bulbous bows,polymer paint,water repellent paint(highly water-repellent wall),air injection,and specific roughness have been used by researchers as an attempt to obtain the resistance reduction and operation efficiency of ships.Micro-bubble injection is a promising technique for lowering frictional resistance.The injected air bubbles are supposed to somehow modify the energy inside the turbulent boundary layer and thereby lower the skin friction.The purpose of this study was to identify the effect of injected micro bubbles on a navy fast patrol boat(FPB) 57 m type model with the following main dimensions:L=2 450 mm,B=400 mm,and T=190 mm.The influence of the location of micro bubble injection and bubble velocity was also investigated.The ship model was pulled by an electric motor whose speed could be varied and adjusted.The ship model resistance was precisely measured by a load cell transducer.Comparison of ship resistance with and without micro-bubble injection was shown on a graph as a function of the drag coefficient and Froude number.It was shown that micro bubble injection behind the mid-ship is the best location to achieve the most effective drag reduction,and the drag reduction caused by the micro-bubbles can reach 6%-9%.     

A three-dimensional, wave-current coupled, sediment transport model for POM

In the high-energy environment of coastal seas and estuaries,strong sediment resuspension/ deposition events are driven by surface waves,tides,winds and buoyancy driven currents.In recent years,A POM based three-dimensional,wave-current coupled,sediment transport model has been developed by the University of New South Wales.This paper presents several examples of the model applications to study sediment dynamics in the environments where forcings such as waves,tides,and winds are equally important to affect sediment fluxes and distributions.Firstly,the sediment transport model coupled to the Yellow Sea general circulation model and a third generation wave model SWAN was implemented in the Yellow Sea to study the dynamics of the sediment transport and resuspension in the northern Jiangsu shoal-wate(rNJSW).The sediment distributions and fluxes and their inter-annual variability were studied by realistic numerical simulations.The study found that the surface waves played a dominant role over the tides to form the turbidity maxima along the muddy coast of NJSW. Secondly,the sediment transport model was used to explore the effect of suspended sediment-induced stratification in the bottom boundary laye(rBBL).The model uses a re-parameterized bottom drag coefficient Cd that incorporates a linear stability function of flux Richardson number Rf.The study has shown that the sediment induced stratification in the BBL reduces the vertical eddy viscosity and bottom shear stress in comparison with the model prediction in a neutrally stratified BBL.In response to these apparent reductions,the tidal current shear is increased and sediments are abnormally concentrated within a thin wall layer that is overlain by a thicker layer with much smaller concentration.The formation of this fluid-mud layer near the seabed has led to a significant reduction in the total sediment transport.This study contributes to the understanding of formations of tidal flats along the coasts of turbid seas and estuaries.     

基于实验结果的小尺寸焊接试件的两相疲劳寿命预测（英文）

The study aims to calibrate parameters of two-phase fatigue prediction model based on the results of the small-scale fatigue test experiments for zero stress ratio and without residual stresses, and then to investigate their applicability for different stress ratios and in the presence of residual stresses. Total fatigue life using the two-phase model consists of crack initiation phase, calculated by strain-life approach, and crack propagation phase, calculated by fracture mechanic’s approach. C...