A review of the effect of a/W ratio on fracture toughness (Ⅲ)——theoretical analysis

In partⅠandⅡof this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment.     

A review of the effect of a/ W ratio on fracture toughness （Ⅲ） ——theoretical analysis

In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment.     

A review of the effect of a/W ratio on fracture toughness (I) —experimental investigation in EPFM

1INTRODUCTION Crackopeningdisplacement(COD)andtheJ in tegralastwoimportantfracture characterizingparame tersinelastic plasticfracturemechanics,arealready welldevelopedandusedinindustrialapplications.However,deeplycrackedstandardlaboratory specimenwhichhasahighlevelofconstraintmaynot alwaysberepresentativeofthosefoundinstructural components.Structuralcomponentsoftenexhibitcom parativelyshallowandsurface breaking,andtheplas ticflowassociatedwiththemreachesthesurfaceofthe component.Inthisca…     

A review of the Effect of a/W ratio on fracture toughness (II)—experimental investigation in LEFM

1 INTRODUCTIONThe linear elastic fracture mechanics provides auseful means of determining a material’s toughness.However, deeply cracked standard laboratory speci-mens those have high level of constraint may not alwaysbe representative of those found in structural compo-nents. Structural components often exhibit compara-tively shallowand surface-breaking.We have previously shown that shallow crackshave greater COD andJ-integral values at initiationthan deeply cracked specimens in EPFM…     

A review of the effect of a／W ratio on fracture toughness （Ⅰ）—experimental investigation in EPFM

Many experimental investigations have previously been performed and recently done on different shipbuilding structural steels where the specimens size and crack depth/specimen width (a/W) were varied. A series of interesting results have been gained. It is worthwhile to have a review on the effect of a/W ratio on fracture toughness, and further theoretical analysis is necessary. In this paper, experimental work in elasticplastic fracture mechanics (EPFM) was discussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J _i and δ₁ values increased with decreasing a/W when a/W<0.3 for three-point bend specimens and that shallow crack specimens which have less constrained flow field give markedly higher values of toughness than deeply notched specimens. However, for a/W>0.3, the toughness was found to be independent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stress is lower than that from standard deeply cracked bend specimen which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structure defects especially if initiation values of COD/J-integral are used.     

A review of the Effect of α/W ratio on fracture toughness （Ⅱ） experimental investigation in LEFM

In part I of this series, experimental investigation in EPFM （elastic-plastic fracture mechanics） had been discussed. In this paper, experimental investigation in LEFM （ linear elastic fracture mechanics） is given. Fracture toughness tests had been carried out on three different strength steels, using both through-cracked specimens with different α/W ratio and semi-elliptical cracked specimens with variable crack size and shape. Results show that the fracture toughness KIC increases with decreasing α/W when α/W 〈 0.3 for three-point-bend specimens, and that for α/W 〉 0.3, it is independent of α/W. Shallow crack specimens, both through-cracked and surface-cracked, gave markedly higher values than deeply notched specimens. However, the effect of crack shape on fracture toughness is negligible. Results also show that the LEFM approach to fracture is not tenable for design stresses where αc is often very small, far less than 2.5 （ KIC/σy）^2.     

A sensitivity analysis of a hull’s local characteristic parameters on ship resistance performance

Simulation-based design hull form optimization has become one of the most effective ways to develop energy-saving ships. However, the traditional method is time consuming and inefficient, so it is difficult to apply it to practical engineering. One of the reasons for this difficulty is that there are numerous parameters for expressing the hull form, making it difficult to find the optimal solution within a short amount of time. Therefore, this paper presents a sensitivity analysis method based on radial basis function and partial least squares regression neural network with uniform design for sampling, to study the sensitivity of local hull parameters of a class of container ships on wave-making resistance performance, and to reduce the number of dimensions in the design space. According to the results of sensitivity analysis, the parameters that are of negligible influence on the objective function can be removed from the optimization model. Comparison of results of the original model and the simplified model shows that the presented sensitivity analysis method can effectively reduce the dimension of the design space so that the time consumed to achieve the optimum is decreased.     

Research on the influence of action between fin and anti-rolling tank on the integrated stabilization effect

Through analyzing the roll model of the integrated system of fin and anti-rolling tank, this paper uses binomial equation to simplify the module and check how the approximate parameters simulate the original function. Based on the simplified module, the influence of fin and anti-rolling tank on the coefficient items of the roll module is discussed, and the influencing factors between fin and anti-rolling tank are analysed. And through simulation, the influence of action between fin and anti-rolling tank on the static characteristics, and the integrated stabilization effect, are analyzed.     

The effect of plastic constraint on the initiation of ductile tears in shipbuilding structural steels

In this paper, the effect of plastic constraint on the initiation of ductile tears in four different shipbuilding structural steels has been experimentally studied by measuring the J-integral and crack opening displacement COD at initiation in three-point bend specimens with deep and shallow notches. Experimental results of seven groups of different strength alloy steels show that both Si and Ji values of ductile tear from the shallow crack specimens which have less constraint flow field are significantly higher than those of deeply notched specimens. Slip-line-field analysis shows that, for shallow crack, the hydrostatic stress is lower than that from standard deeply cracked bend specimen, which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structural defects, especially if initiation values of COD and J-integral are used.     

Westward moving waves or eddies (Storms) on the Subtropical/Azores Front near 32.5°N? Interpretation of the Eulerian currents and temperature records at moorings 155 (35.5°W) and 156 (34.4°W)

Three Argos buoy-years of Lagrangian data in westward-moving cyclonic eddies, or Storms, near 32.5°N, together with hydrographic measurements, have shown that Storms move westward at nearly 3 km day⁻¹. Water in eddies can be trapped and moved westward by advection within the eddy or by phase propagation of the eddy pattern, so we cannot say that the flow field (or Eulerian mean) is 3 km day⁻¹ westward. Two moorings (155 and 156) deployed in the Storm Corridor have provided a further 8 instrument-years of Eulerian data. The temperature and current records confirmed that two Storms a year passed each mooring over the 2-year measurement period. As expected, there is a lag of 1.3 month at mooring 155 (which is 102 km to the west of mooring 156) with respect to conditions at mooring 156. The progressive vector diagrams (PVDs) derived from the current meter records exhibit fairly regular X (east or zonal) and Y (north or meridional) displacement scales that repeat with semi-annual periodicity (SAP). The dominant current signal is the north component of the SAP, which reaches an amplitude of 18 cm s⁻¹ for the upper layer or near surface current record (242-m depth). The geostrophic north component values derived from altimetry were in good agreement with the upper layer current meter measurements. The large north component amplitude was not interpreted as evidence for Rossby Waves but rather due to the passage of nine eddies (eight complete) of alternate sign (cyclonic, anticyclonic) passing the mooring rigs during the 2-year deployment period. The Y scale shows that the near surface characteristic or mean maximum azimuthal speed is about 35 cm s⁻¹ for cyclonic eddies or Storms, and that this value is reduced to 4 cm s⁻¹ at 1400-m depth. The residual or mean Eulerian currents range from 8 cm s⁻¹ for the upper layer currents to 1 cm s⁻¹ for the deeper currents at 1400-m depth and are predominantly westward. Simple theoretical considerations and idealised numerical simulations show that the mean westward Eulerian current depends markedly on whether the eddy centres pass to the north or south of the rigs. This raises the question as to what do we mean by Eulerian residual currents, even for relatively long records (2 years). It is shown that the strong near surface westward current (6 km day⁻¹) measured at mooring 155 is largely due to a westward-moving eddy field with variable centre offsets. The magnitude of the near surface east–west component of flow was estimated as eastward at 2 cm s⁻¹. The north–south component of mean flow was southward at 2 cm s⁻¹. The deeper records gave a weak westward flow of 1 cm s⁻¹ but did not show a significant southward component for the mean Eulerian flow field. 7.4 float-years of Lagrangian ALACE data in the Subtropical Front region near 740 dbar gave mean east–west flows that were <0.5 cm s⁻¹. Overall, it is shown that the eddy structures propagate westward mainly by phase propagation (i.e. a westward-moving pattern with no westward advection for the current meter to measure), though plane Rossby Wave dynamics appeared inappropriate. Theoretical and modeling considerations show that a speed of 3-km day⁻¹ westward is too large a value for the self-advection of eddies due to the beta effect.     

Does the political and economic context influence the success of a transport project? An analysis of transport public-private partnerships

The construction and provision of infrastructure services such as transport nowadays is often based on a partnership between three main actors: public sector, private sector and multilateral lenders, under a framework of Public-Private Partnerships (PPPs). This type of partnership has been employed in a wide range of projects in the transport sector and in various contexts in developing and developed countries. Given this observation, the objective of this paper is to examine how countries’ economic and political characteristics contribute to the success of PPPs in transport investments. Special focus in the analysis is given to how the perception of corruption and democratic accountability may influence the success of a PPP project in different transport sectors. We examine a database with 856 transport PPP projects using a generalized linear model in the form of a logit model in order to evaluate the transport database covering data from 72 countries, classified in six regions. The study highlights the importance of national experience. Not only does national macroeconomic experience appear to have a relevant role, but so also does its past experience (either positive or negative) of transport PPP projects. An interesting finding from the analysis is the importance of the rest of the world’s perception of a country’s level of corruption and democratic accountability for the final outcome of a PPP project.     

A game theory analysis of port specialization—implications to the Chinese port industry

The fast growth of the Chinese economy and its international seaborne trade has escalated the demand for high-quality and efficient port services. “Decentralization” of the port management regime has given local government greater freedom in port development and operational decision-making. However, major port capacity expansion in coastal areas, coupled with the slowing down of both the economy and trade growth over recent years, has led to overcapacity and excessive competition. Although both port specialization and government regulations are called for to address these issues, few studies have investigated the formation mechanism and economic implications of port specialization. This paper uses alternative duopoly games, namely a Stackelberg game and a simultaneous game, to model port competition, where ports provide differentiated services in the sectors of containerized cargo and dry-bulk cargo. Our analytical results reveal that inter-port competition can lead to port specialization in the following three ways. A port can specialize in a type of cargo (1) for which there is relatively high demand, (2) where it has established capacity first, or (3) for services which require prohibitively high capacity costs. Also, it is seen that overcapacity is likely if strategic port decisions are made simultaneously instead of sequentially. These results suggest that if there is a clear market leader, policy intervention may not be necessary. However, if no port has clear market power, then government coordination and intervention may be needed in order to prevent overcapacity and to encourage specialization.     

Allision risk analysis of offshore petroleum installations on the Norwegian Continental Shelf—an empirical study of vessel traffic patterns

The Norwegian Petroleum Safety Authority (PSA) requires offshore petroleum operators on the Norwegian Continental Shelf (NCS) to perform risk assessments of impacts (allisions) between passing ships and offshore installations. These risk assessments provide a basis for defining the allision accidental load that the installation shall be designed for. Even though the risk of allision is small, the potential consequences can be catastrophic. In a worst-case scenario, an allision may result in the total loss of an installation. The ageing industry standard allision risk model, COLLIDE, calculates the risk of impacts between passing (non-field-related) ships and installations based on Automatic Identification System (AIS) data. Both the COLLIDE risk model and a new Bayesian allision risk model currently under development are highly sensitive to variations in vessels’ passing distances, especially close proximity passings. Allision risk assessments are typically performed during the design and development phase of an installation, which means that historical AIS data are used “as is”, disregarding future changes to the traffic pattern when the new installation is placed on a location. This article presents an empirical study of one of the most important variables used to calculate the risk of allision from passing vessels, namely passing distance. The study shows that merchant vessels alter course to achieve a safe passing distance to new surface offshore petroleum installations. This indicates that the results of current allision risk assessments are overly conservative.     

Build the First LargestBridge of China and Create a Constructionof Fine Quality of the Century——A briefaccount of theconstruction of the infrastructure of the main bridgeof Jiangyin Yangtze River Highway Bridgc

国家主席江泽民题写桥名并出席通车仪式的“江阴大桥”是主跨为1385m,一跨过长江,中国第一、世界第四的钢悬索特大公路桥。本文综述了中港二航局在承建大桥下部结构(A标、B标)的施工中,根据工程规模大、合同期短、技术含量高、地质条件复杂、施工难度大等特点,运用系统工程原理,健全质量保证体系,坚持技术领先,优化要素配置,精心雕塑中国第一大桥,取得单位工程质量评比全优的佳绩。     

The concept of “shipowner” under new maritime labor law (MLC, 2006): does the shipowner own the ship? (comparative analysis of national law of Denmark,Finland, Germany,Norway, and the United Kingdom)

The identification of the responsible shipowner is essential for seafarers in order to claim payments and compensation in respect of their employment on board a ship. Often this may be difficult because of corporate arrangements and the many intermediaries traditionally involved in ship operation. The Maritime Labour Convention 2006 (MLC, 2006), adopted by the International Labour Conference (ILC) 94th (Maritime) Session in 2006, entered into force on August 2013; it significantly affects the shipowner’s responsibility in respect to seafarers’ employment. Taking into account the mentioned issue, the article examines the concept of “shipowner” under the MLC, 2006 and presents comparative analysis of the relevant national law implementing the MLC, 2006 in Denmark, Finland, Germany, Norway, and the United Kingdom.     

Numerical analysis of cavitating propeller and pressure fluctuation on ship stern using a simple surface panel method “SQCM”

This paper presents a calculation method for the pressure fluctuation induced by a cavitating propeller. This method consists of two steps: the first step is the calculation of propeller sheet cavitation, and the second step is the calculation of pressure fluctuation on the ship stern. It is for practicality that we divide the method into two steps but do not calculate these steps simultaneously. This method is based on a simple surface panel method “SQCM” which satisfies the Kutta condition easily. The SQCM consists of Hess and Smith type source panels on the propeller or cavity surface and discrete vortices on the camber surface according to Lan’s QCM (quasi-continuous vortex lattice method). In the first step, the cavity shape is solved by the boundary condition based on the free streamline theory. In order to get the accurate cavity shape near the tip of the propeller blade, the cross flow component is taken into consideration on the boundary condition. In the second step, we calculate the cavitating propeller and the hull surface flow simultaneously so as to calculate the pressure fluctuation including the interaction between the propeller and the hull. At that time, the cavity shape is changed at each time step using the calculated cavity shape gotten by the first step. Qualitative agreements are obtained between the calculated results and the experimental data regarding cavity shape, cavity volume and low order frequency components of the pressure fluctuation induced by the cavitating propeller.