Kawabata, Tomoya (The University of Tokyo) | Namegawa, Tetsuya (The University of Tokyo) | Kaneko, Masahito (Kobe Steel, Ltd.) | Shimada, Yusuke (Nippon Steel and Sumitomo Metal Corporation) | Tajika, Hisakazu (JFE Steel Corporation) | Shibanuma, Kazuki (The University of Tokyo) | Aihara, Shuji (The University of Tokyo)
Run-arrest behavior of brittle crack in steel has been investigated since a lot of severe accidents by brittle failure. In order to evaluate arrest toughness of materials, various test methods were developed. In 2014, arrest toughness evaluation standard which determined the test method of temperature gradient type ESSO test was established through activities in the Japan Welding Engineering Society. However simplified test method is desired because ESSO test requires large specimen and large test rig. In this study, common material is evaluated by newly suggested small test, "press-notched bend
Veldman, Arthur E. P. (University of Groningen) | Luppes, Roel (University of Groningen) | van der Heiden, Henri J. L. (University of Groningen) | van der Plas, Peter (University of Groningen) | Helder, Joop (MARIN) | Bunnik, Tim (MARIN)
To study extreme hydrodynamic wave impact in offshore and coastal engineering, the VOF-based CFD simulation tool ComFLOW is being developed. Recently, much attention has been paid to turbulence modeling and local grid refinement. In particular, a blend of a QRmodel and a regularization model has been designed. The QR-model belongs to a class of modern eddy-viscosity models, where the amount of turbulent eddy viscosity is kept minimal. For validation, experiments have been carried out at MARIN.
Since a closed-loop system of biodiesel fuel (BDF) production and utilization is supposed to implement in Ha Long Bay, Viet Nam, the research on Inclusive Impact Index of Biodiesel Production and Cruise Ship Utilization was created to assess and evaluate impacts on environment, energy balance and economics of some parts in BDF production and utilization chain. In this paper, Triple I light and Triple I light star, a simple-form Triple I, were used to evaluate the BDF production from Jatropha curcas oil and waste cooking oil, and their application in ship cruising in Ha Long Bay.
Li, Hui (Wuhan University of Technology) | Langxiong-Gan, _ (Hubei Key Laboratory of Inland Navigation Technology) | Jingxian-Liu, _ (Wuhan University of Technology) | Yuanzhou-Zheng, _ (Hubei Key Laboratory of Inland Navigation Technology) | Xiaobo-Zhao, _ (Wuhan University of Technology) | Limin-Deng, _ (Hubei Key Laboratory of Inland Navigation Technology)
To reduce the structural damage from ship collisions and improve the energy absorption capacity of ships, a ship-ship collision model was established to simulate the process of collision. The initial kinetic energy of collision ship transforms into plastic deformation energy absorption, the remaining kinetic energy and the energy absorption of a fluid medium of a collided ship take up a negligible proportion so it can be disregarded. Based on the law of conservation of energy and using the collision of ship’s bow and another ship’s side as an example, the effects of collisions at different speeds including 10kts and 15kts at the same angles 45°, 60° and 90°, respectively and from different angles at the same speed on the structural damage of ship collision areas are discussed. In addition, an appropriate collision state is defined so as to be beneficial for navigators who must reduce the losses from collision in cases of inevitable collision by steering based on simulations and display of the nonlinear dynamic responses using the finite element analysis program DYTRAN. When structural damage of the bow is small, the structural damage of the side is very big; the bow is regarded as a rigid body and the side is regarded as a deformation body. Simulation results indicate that the speed and angle have an effect on the energy absorption of a ship; different speeds and angles can lead to different degrees of structural damage. This research provides an empirical foundation for the control of speed and angle and also provides a reference for maritime collision investigations.
Sumi, Hiroyuki (JFE Steel Corporation) | Kitani, Yasushi (JFE Steel Corporation) | Kodama, Toshifumi (JFE Steel Corporation) | Matsui, Yutaka (JFE Steel Corporation) | Suzuki, Takeshi (JFE Steel Corporation) | Sakashita, Shigeto (JFE Steel Corporation) | Kumazawa, Shintaro (JFE Steel Corporation)
The laser welding process for manufacturing pipe was advanced from the conventional single-beam welding method using one high power CO2 laser to a twin-beam laser welding method using two high power fiber lasers arranged in tandem on the weld seam. Using the newlydeveloped welding process, a trial product of laser welded 13% Cr steel pipe was manufactured. It was confirmed that the trial pipe has strength equivalent to API-X80 grade, excellent toughness and CO2 corrosion resistance approximately equal to that of seamless 13% Cr pipe.
Shaposhnikov, Valery (Krylov State Research Centre) | Aleksandrov, Anatolii (Krylov State Research Centre) | Platonov, Viktor (Krylov State Research Centre) | Litonov, Oleg (Krylov State Research Centre) | Appolonov, Evgeny (St.Petersburg State Marine Technical University) | Demeshko, Gennady (St.Petersburg State Marine Technical University)
At the present time Russian and foreign normative documents consider loads caused by moving ice fields as dynamic loads on offshore fixed structures. Design loads are presented in the form of contact pressure functions versus ice field speed, ice thickness and physical-mechanical properties, contact area. These functions are obtained based on processing results of multiple full scale tests and model experimental studies.
The paper considers modern approaches for calculation of loads under dynamic offshore fixed structure interaction with drifting ice fields and ice formations. Effects of structural shell plating and framing compliance, as well as structural dynamical characteristics as a whole on ice load values are considered.
Bekker, Alexander T. (Far Eastern Federal University) | Tsimbelman, Nikita Ya. (Far Eastern Federal University) | Chernova, Tatiana I. (Far Eastern Federal University) | Bruss, Vadim D. (Far Eastern Federal University) | Bilgin, Ömer (University of Dayton, School of Engineering)
Thin metal or reinforced concrete shells with granular infill structures are considered in this article. These structures are massive and they are used as support for the construction of berthing quays, piers, artificial islands, shore protection, and other structures of coastal infrastructure. It is more convenient to use the thin shell structures during the development of the Arctic shelf, because it is possible to install them from the ice side. In addition, it is possible to enhance the technology and install thin shells with infill on deeper solid foundation layers. A mathematical model for the stresses on a compressible foundation soil in front of a thin cylindrical shell with infill due to the eccentric loading is developed. A modeling and experimental determination of the interface strength of the contact surface between the infill and the inner surface of the shell is proposed. The details of the construction stages and testing of the physical model used for the experiments are discussed. The effects of the interface friction on the shell behavior and on the foundation stresses in front of the wall are investigated. The influence of parameters affecting the interaction between the soil infill and the inner surface of the shell material is determined. It is based on a comparison of experimental results with calculations performed using the proposed mathematical model. The obtained parameters and proposed methods can be used in numerical simulations using the finite element method to analyze and design the thin shell structures with soil infill. The findings of the study and proposed methods can also be applied to the thin shell structures used in other facilities such as hydraulic, industrial, civil, and transportation.
Dynamic compaction is known as one of the most cost-effective soil improvement techniques. In this method the soil at the ground surface or at a relatively deep depth is compacted by repeatedly dropping heavy weights on the ground. Since its introduction, dynamic compaction has exhibited its versatility and simplicity of use in different types of civil engineering projects, including building structures, container terminals, highways, airports, dockyards, and harbours. However, despite the abundance of experimental data and field observation reports, few numerical approaches have been established in the literature to effectively deal with soil behaviour under dynamic compaction. This is mainly due to the dependence of soil dynamic response on variations in the moisture content. Therefore, to achieve a comprehensive understanding of dynamic compaction the soil should be modelled as a three-phase porous medium. The presence of a non-wetting and a wetting phase, together with the existence of inertia forces in each phase, makes the solution of the coupled dynamic system computationally demanding. Moreover, large deformations often take place during dynamic compaction; hence the infinitesimal strain theory cannot be employed for higher impact loads. In this paper a finite element approach is introduced to numerically simulate the problem of dynamic compaction under the framework of unsaturated soil mechanics. The governing equations are derived based upon the overall momentum balance of the mixture, the mass balance of the liquid phase, and the mass balance of the gas phase. Phase changes and chemical reactions are not considered. Among other important parameters, the effect of the degree of saturation on the soil response will be addressed.
In general, the underwater observation of facilities in offshore areas like offshore structure and dam is conducted by human operation. However, the observation by human has some difficulties such as high cost, safety of workers in severe environmental conditions. Therefore there is a growing need for unmanned underwater observation vehicles. In this research the authors developed a high-mobility unmanned underwater observation vehicle for sea exploration. Because the developed vehicle is designed small-scale and lightweight, the vehicle is easy to carry around. The super-luminosity LEDs mounted in vehicle are much brighter than a halogen lamp, and assist in taking distinct images.
The vortex-induced motion (VIM) of semi-submersible platforms becomes an important issue with the recent development of deep draft semi-submersible platforms. As a result of the increased draft, the semi-submersibles are susceptible to coherent vortex shedding, and the platform VIM increases significantly. The VIM of semi-submersibles is more complex than those of spars and mono-column hulls due to the wake interaction of vortices shed from multiple columns. In general, the vortex-induced motion of deep draft semi-submersible platform is characterized mainly by three degree-of-freedom motions with surge (in-line), sway (transverse), and yaw motions. In the present study, numerical simulations are performed for a semi-submersible with four square columns subjected to a current at a 45 degree incidence angle. Calculations were performed using the Finite-Analytic Navier-Stokes (FANS) code in conjunction with a moving overset grid approach to accommodate the relative motions between the semi-submersible hull, wake, and background grid blocks. Simulations are performed both for the full scale and the 1:70 model platforms to check the validity of the Froude scaling law. Various current speeds corresponding to different reduced velocities are simulated. Motion responses and the flow fields for both the model and full scale platforms are studied. Comparisons are made with experimental data to demonstrate the capability of the present CFD approach.