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Compositional Variants of Cu-rich Precipitate in Thermally Aged Ferritic Steel

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Acta Metallurgica Sinica(English Letters) 2018年第5期31卷 465-470页

作者： Qingdong Liu Yihua Chen Chuanwei Li Jianfeng Gu Institute of Materials Modification and Modelling School of Materials Science and Engineering Shanghai Jiao Tong University collaborative innovation center for advanced ship and Deep-Sea exploration Shanghai Jiao Tong University Scholl of Nuclear Science and Engineering Shanghai Jiao Tong University

Atom probe tomography was utilized to investigate Cu precipitation in a high-strength low-alloy steel isothermally aged at 500℃ for 1, 4, 16, and 64 h after water-quenching from 900℃. With prolonged aging time, the Curich precipitates（CRPs） increased in size and decreased in number density, and gradually evolved from spheroidal to elliptical in morphology. The small CRPs were rich in a high amount of Fe and a certain amount of Ni and Mn at their early nucleation stage. The large CRPs with increased size due to extensive aging contained less Fe and more Cu at their later growth stage. Additionally, Ni and Mn were both readily to segregate at the CRP/matrix heterophase interfaces, and Mn was higher in content than Ni in the precipitate interior especially when the CRPs were large in size.

关键词： High-strength low-alloy steel Thermal aging Cu-rich precipitate Atom probe tomography

Stationary phase and practical numerical evaluation of ship waves in shallow water

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Journal of Hydrodynamics 2017年第5期29卷 817-824页

作者：张晨亮王金宝朱怡 Francis Noblesse Marine Design and Research Institute of China Shanghai 20011China School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China collaborative innovation center for advanced ship and Deep-Sea exploration Shanghai 200240China

A simple and highly-efficient method for numerically evaluating the waves created by a ship that travels at a constant speed in calm water, of large depth or of uniform depth, is given. The method, inspired by Kelvin＇s classical stationary-phase analysis, is suited for evaluating far-field as well as near-field waves. More generally, the method can be applied to a broad class of integrals with integrands that contain a rapidly oscillatory trigonometric function with a phase function whose first derivative（and possibly also higher derivatives） vanishes at one or several points, commonly called points of stationary phase, with the range of integration.

关键词： ship waves fourier integral numerical evaluation stationary phase

Numerical simulation of plate rigid restraint cracking tests based on cohesive element model

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China Welding 2016年第2期25卷 14-20页

作者： Shi Chu Wang Yang Luo Yu State Key Laboratory of Ocean Engineering and Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong University Shanghai 20003

Cohesive element is developed from the Dugdal-Barenblatt model in the field of fracture mechanics. The mechanical constitutive relation of cohesive element can be artificially assumed depending on the specific applications. It has been successfully applied in the study of crystal plasticity/brittle fracture process and decohesion between delaminations. In this paper, tensile experiments of large steel plate with different length of pre-existing cracks are conducted. Based on commercial software ABAQUS, cohesive element is adopted to simulate the tensile tests, and appropriate parameter values are obtained by fitting displacement-force curves. Using these parameters, a numerical method is presented by applying cohesive element to thermo-elastic-plastic finite element method （TEP-FEM） to simulate plate rigid restraint cracking （PRRC） tests. By changing constitutive relation of cohesive element, dimensions of the model and welding conditions, the influence of welding restraint intensity and welding conditions on the crack propagation are discussed, respectively. Three types of welding cold cracking are simulated. Significant influence of welding cold cracking on resistant stress in welding line is captured by this numerical method.

关键词： crack propagation cohesive element thermal-elastic-plastic finite element method plate rigid restraint cracking test

Synthetic Effects of Frequency and Duty Ratio on Growth Characteristics, Energy Consumption and Corrosion Properties of Microarc Oxidized Coating Formed on Ti6Al4V

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Acta Metallurgica Sinica(English Letters) 2018年第10期31卷 1109-1120页

作者： Tong Zhou Zhen-Bo Qin Qin Luo Qi Zhang Bin Shen Wen-Bin Hu Lei Liu State Key Laboratory of Metal Matrix Composites School of Material Science and Engineering Shanghai Jiao Tong University School of Material Science and Engineering Tianjin University collaborative innovation center for advanced ship and Deep-Sea exploration Shanghai Jiao Tong University

The synthetic effects of frequency and duty ratio on growth characteristics and corrosion properties of coating on Ti6Al4V fabricated by microarc oxidation are investigated comprehensively. Under the condition of uniform cumulating time of positive impulse width, the essence of altering frequency and duty ratio to determine the formation of coating is to vary the duration and interval time of positive pulse. The growth of coating is mainly controlled by duration time of positive pulse and hardly correlated to the interval time of positive pulse, while both duration and interval time of positive pulse have few influences on the morphology and phase structures of coating. The dynamic current is related to positive impulse width and the ratio of positive pulse on-time to pulse off-time. Regardless of uniform duration or interval time of positive pulse, the energy dissipation presents a descending tendency. The relationship between energy consumption and anticorrosion performance is contradictory, and obtaining excellent corrosion ratio and frequency can be designed purposefully to realize the resistance is bound to sacrifice lots of energy. The duty optimal process.

关键词： Microarc oxidation Titanium alloy Frequency Duty ratio

Experimental Study on ship-Bank Interaction of Very Large Crude Carrier in Shallow Water

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Journal of Shanghai Jiaotong university(Science) 2018年第6期23卷 730-739页

作者： LIU Han MA Ning GU Xiechong State Key Laboratory of Ocean Engineering Collaborative Innovation Center for Advanced Ship and Deep-Sea ExplorationSchool of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

In order to assess the influence of ship-bank interaction on ship manoeuvring motion, planar motion mechanism(PMM) tests on a scale model of the KRISO very large crude carrier(KVLCC2) are conducted in different water depths in circulating water channel(CWC). The asymmetric hydrodynamic derivatives are defined to characterize the bank effect, and they are measured through the straight towing test with varying lateral displacements. The linear and nonlinear hydrodynamic derivatives are determined from the test data of the Fourier integral and mathematical regression model. The rudder and heading angles required at equilibrium conditions in different ship-bank distances are calculated by the manoeuvring model. The directional stability with varying ship-bank distances is studied in terms of eigenvalue analysis. Analysis based on the test results shows that the KVLCC2 model ship appears inherently unstable for keeping course in deep and shallow water conditions. When the ship-bank distance decreases, the increasing ship-bank interaction can dramatically affect some parameters of the criteria for course keeping.

关键词： ship-bank interaction shallow water planar motion mechanism (PMM) asymmetric hydrodynamic derivatives

Numerical Wave Tank Based on A Conserved Wave-Absorbing Method

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China Ocean Engineering 2016年第1期30卷 137-148页

作者：扈喆唐文勇薛鸿祥张晓莹 State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University Shanghai 200240 China collaborative innovation center for advanced ship andDeep-Sea exploration Shanghai 200240 China Bureau Veritas Marine (China) Co. Ltd Shanghai 200011 China

Recently the numerical wave tank has become a widely-used tool to study waves as well as wave-structure interactions, and the wave-absorbing method is very important as its effect on the quality of waves generated. The relaxation method and the derived momentum source method are often utilized, however, the damping weight is constant during calculation and repeated trials are required to obtain an acceptable wave-absorbing effect. To address the abovementioned issues, a conserved wave-absorbing method is developed. The damping weight is determined by solving the mass conservation equation of the absorbing region at every time step. Based on this method, a two-dimensional numerical wave tank is established by using the VB language to simulate various waves by which the validation of this method is evaluated.

关键词： conservation wave absorption weight numerical wave tank waves

Numerical study of vibrations of a vertical tension riser excited at the top end

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Journal of Ocean Engineering and Science 2017年第4期2卷 268-278页

作者： Bowen Fu Decheng Wan State Key Laboratory of Ocean Engineering School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityCollaborative Innovation Center for Advanced Ship and Deep-Sea ExplorationShanghai 200240China

This paper presents numerical simulations of vortex-induced vibrations of a vertical riser which is sinusoidally excited at its top end in both one and two directions in still water.A computational fluid dynamics method based on the strip theory is *** riser’s responses to both top-end and two-end excitations are carefully *** low reduced velocity cases,the in-line vibrations consist of three components,the low-frequency oscillation,the first-natural-frequency vibration during the riser reversal,and the second-natural-frequency vibration due to vortex *** sheared oscillatory flow along the span causes low-frequency oscillations in higher modes in the in-line direction,thus forming‘X’shaped,‘II’shaped,and‘O’shaped trajectories at various positions along the span when the riser is excited at its top end in one *** the presence of excitations in the other direction,more complex trajectories appear.

关键词： Vortex-induced vibration Oscillatory flow Riser Platform motion Viv-FOAM-SJTU solver

Experimental Investigation into the Effect of Roll Amplitude on Roll Damping

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Journal of Shanghai Jiaotong university(Science) 2019年第6期24卷 732-738页

作者： HANG Xiaohui GU Xiechong MA Ning WANG Yifan WU Zeren State Key Laboratory of Ocean Engineering collaborative innovation center for advanced ship and Deep-Sea exploration School of Naval Architecture Ocean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

An in-house large eddy simulation(LES)code has been developed in the previous *** order to validate the code for simulation of roll motion,effect of roll amplitude on forced roll damping is experimentally investigated in a circulating water channel at Shanghai Jiao Tong University(SJTU).KRISO very large crude carrier 2(KVLCC2)is taken as a target ship,and a model with a scale of 1:128.77 is *** are carried out for the ship model at shallow draft with frequencies around its natural roll frequency,where natural roll frequency is attained via free roll *** forced roll tests with roll amplitudes ranging from 1?to 4?are performed experimentally,and three forced roll motions are simulated with the in-house LES code for middle section of the ship *** between the computed roll damping coefficients and the ones from forced roll tests are quite *** means of particle image velocimetry(PIV),velocity fields in the vicinity of the ship model,and generation and evolution of vortices near the ship bilge are measured in *** is shown that roll amplitude has a significant effect on the vortex behavior,and therefore on the magnitude of roll damping *** experimental and numerical investigation into roll motions with large amplitudes is planned.

关键词： roll damping forced rolling ship model test particle image velocimetry(PIV) velocity field

Basic models of farfield ship waves in shallow water

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Journal of Ocean Engineering and Science 2018年第2期3卷 109-126页

作者： Yi Zhu Jaiyi He Huiyu Wu Wei Li Francis Noblesse State Key Laboratory of Ocean Engineering School of Naval ArchitectureOcean&Civil EngineeringCollaborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai Jiao Tong UniversityShanghaiChina

Basic models of the farfield waves created by a monohull ship or a catamaran that travels at a constant speed in calm water of uniform finite depth are considered.A classical basic model is the 1-point ship model introduced by Kelvin in 1887 for deep water and extended to uniform finite water depth by Havelock in *** basic model is the 2-point ship model,which considers the two dominant waves created by the bow and the stern of a monohull ship or by the twin bows of a catamaran,and therefore accounts for main wave interference *** 2-point ship models contain information that cannot be found in the classical patterns for the 1-point ship model commonly used since *** particular,whereas Havelock’s classical wave patterns for the 1-point model only depend on the Froude number based on the water depth,the farfield waves for the 2-point models of a monohull ship or a catamaran also depend on the Froude number associated with the length of the monohull ship or the spacing between the twin hulls of the ***,the‘apparent wake angles’associated with the highest waves that result from constructive wave interferences can greatly differ from the cusp or asymptote angles of Havelock’s wave patterns.

关键词： Farfield ship waves Shallow water ship models Wave interferences