ABSTRACT The aim of this study is to provide additional understanding of the evolution of local stress-strain state near crack-tip in a surface cracked pipe subjected to combined loading and its correlation with the near tip fields developed in small scale test specimens. This will help determine the range of applicability in predicting initiation and propagation of initial cracks. KEY WORDS: biaxial loading, CTOD, R curve, constraint INTRODUCTION Classical fracture mechanics relies upon monoparametric approach (J-integral or CTOD) to evaluate the severity of crack-like defects in metallic structures. This framework is well established for small-scale yielding conditions and its extension to large-scale deformation in defective pipes is somewhat unclear when the complexity of possible loading scenarios worsen. Recent studies (Minaar et al, 2007; Gioielli, 2007) have provided a methodology for measuring fracture response in large-scale testing girth weld pipes using a modified compliance method for X65 pipeline steel. Despite its effectiveness in predicting strain capacity in pressurized girth weld pipes under tension, a large costly experimental facility is required. Additionally, Igi (Igi et al, 2011) also performed both full-scale and small scale tests on X80 pipeline subjected to biaxial loading.
A Boussinesq-type model is developed for simulating wave and runup generated by sliding masses in the coastal region. A shock-capturing Boussinesq type model, which is originally designed for simulation of coastal water waves over fixed sea bottom, is extended to include the effect of time-varying bed. Landslide is then assumed as a rigid body without changing its shape during sliding. The governing equations are solved using a hybrid finite difference and finite volume method with shock-capturing ability. Moving shoreline is specially treated in the model. The resulting numerical model is particularly efficient and computationally robust. Numerous numerical experiments, including both 1DV and 2DH cases, are conducted for model validation and the computed results are compared against the analytical solution or experimental data.
Lim, Chang Hyuck (Korea Research Institute of Ship & Ocean Engineering) | Park, Ji Yong (Korea Research Institute of Ship & Ocean Engineering) | Choi, Jong Su (Korea Research Institute of Ship & Ocean Engineering) | Cheon, Ho Jeong (Korea Research Institute of Ship & Ocean Engineering) | Shin, Seung Ho (Korea Research Institute of Ship & Ocean Engineering)
The locations of structures will be identified using a sensor, and systems including the generator, PCS, hydraulic systems and grid-connected systems to be installed will be examined and controlled to generate the optimal amount of electricity using MPPT. First the locations of structures will be identified using DGPS and 6 Degrees Of Freedom; the temperature of hydraulic system and generators, the angle of pendulum, etc. will be measured and controlled; and the electrical signal from PCS will be monitored. To build an operation system to generate the optimal amount of electricity and prevent emergency situations, a flow chart will be made and a system for operating and controlling power plant will be designed. This energy can be harnessed by wave energy converters (WECs) to create electricity, with devices installed in deep water producing greater wave energy than those in shallow water. So, we focused on a floating-type wave activated body wave energy converter (WEC).
As an indispensable tool for ocean exploration, underwater vehicles have drawn the attention of the researchers in academia and i ndustry. Load-bearing structures are not the only installation base for each class of system equipment of submersible vehicles, but also excellent hydrodynamic properties must be guaranteed. The main loaded carrier structure of an underwater vehicle in lifting and recovery should meet the requirements of safety and have minimum weight at the same time. Previously metal materials have been used to make the structural framework. As a representative of new materials, composite materials have several excellent properties such as great strength and corrosion resistance. Therefore, composite materials for the carrier structure of underwater vehicles have obvious advantages.
Kim, Yoo-Chul (KRISO (Korea Research Institute of Ships & Ocean Engineering)) | Kim, Kwang-Soo (KRISO (Korea Research Institute of Ships & Ocean Engineering)) | Kim, Jin (KRISO (Korea Research Institute of Ships & Ocean Engineering)) | Kim, Yoonsik (KRISO (Korea Research Institute of Ships & Ocean Engineering)) | Van, Suak-Ho (KRISO (Korea Research Institute of Ships & Ocean Engineering)) | Jang, Young-Hun (Daewoo Shipbuilding & Marine Engineering Co., Ltd.)
The present study provides the numerical simulations with the unsteady Reynolds Averaged Navier-Stokes (URANS) methods for the prediction of added resistance performance of hull forms advancing forward in regular waves. Two degrees of freedom motion (pitch and heave) are solved in the non-inertial reference frame in which the effects of the motions are considered as a body force source term in the governing equations. The relative translational and rotational velocities according to the motions of the hull are imposed at all the far-field boundaries. The computation of the added resistance and 2DOF motions were carried out for KVLCC2 and its modified hull form in which bow shape is sharpened with removing the bow-bulb under thirteen different regular head-wave conditions. The computational results showed good agreement with the experiments and the modified hull form is superior to the original KVLCC2 in added resistance performances.
To prevent or reduce the damage by unstable ductile fracture accidents of high-pressure gas pipelines, an evaluation model based on their physical phenomena is required. The authors developed a fluidstructure- fracture coupled model which is based on crack tip opening angle (CTOA) as a fracture criterion. In this model, the effect of dynamic strain field is calculated by a FE analysis and incorporated into the model. Critical CTOA is adopted as crack-velocity-independent material toughness corresponding to critical local strain. The results of calculations for several full-scale burst tests revealed practicability of the model compared with existing ones.
This paper presents the technical challenges of unbonded flexible risers in the high pressure and high temperature (HPHT) conditions with deepwater applications. Based on the structural characteristics of unbonded flexible risers, the key factors that have an impact on the stress and fatigue damage of unbonded flexible risers are discussed, and the potential failure modes at such HPHT and deepwater conditions are highlighted. It is proposed that developing the failure driver approach of the risk-based strategy to the systematically assessment of the failure modes, incorporated with the riser system condition monitoring and integrity management, will be an effective way to meet the technical challenges of the unbonded flexible risers in HPHT and deepwater operations.
Although development of offshore wind energy in China was started late compared with European countries, it has been growing quickly in recent years. Offshore wind foundation is very important for the safety and operation of offshore wind turbine. 8 piles with cap was initially adopted in Shanghai Donghai Bridge Offshore Wind Farm in China which is the first large offshore wind farm in Asia. Taking this wind farm as an example, the authors established a wind turbine-foundationseabed 3D numerical model. Deformation analysis for 8 piles with cap was carried out.
Goupee, Andrew J. (University of Maine) | Kimball, Richard W. (Maine Maritime Academy) | de Ridder, Erik-Jan (Maritime Research Institute Netherlands) | Helder, Joop (Maritime Research Institute Netherlands) | Robertson, Amy N. (National Renewable Energy Laboratory) | Jonkman, Jason M. (National Renewable Energy Laboratory)
In this paper, a calibrated blade-element/momentum theory aerodynamic model of the Maritime Research Institute Netherlands (MARIN) stock wind turbine is developed and documented. The model is created using open-source software and calibrated to closely emulate experimental data obtained by the DeepCwind Consortium using a genetic algorithm optimization routine. The provided model will be useful for those interested in validating floating wind turbine numerical simulators that rely on experiments utilizing the MARIN stock wind turbine—for example, the International Energy Agency Wind Task 30’s Offshore Code Comparison Collaboration Continued, with Correlation project.
Jahrsengene, G. (Norwegian University of Science and Technology(NTNU)) | Wenn, M. (Norwegian University of Science and Technology(NTNU)) | Karlsen, M. (Norwegian University of Science and Technology(NTNU)) | Westermann, I. (Statoil ASA) | Akselsen, O. M. (Norwegian University of Science and Technology(NTNU)) | Hjelen, J. (Norwegian University of Science and Technology(NTNU))
The present work involves quantification of retained austenite in a low carbon 9% nickel steel designed for storage of liquefied natural gases (LNG) at cryogenic temperatures. Investigations were carried out in a high resolution field emission scanning electron microscope (FESEM) using Electron Backscatter Diffraction (EBSD) measurements. Weld simulated steel was examined by this technique to determine which combination of heating cycles gave the highest amount of austenite in the resulting steel, the retained austenite being a very important parameter considering low temperature use. The as-received material was also investigated with respect to austenite content.