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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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International Journal of Ocean System Engineering
Journal Basic Information
Journal DOI :
Korean Society of Ocean Engineers
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Volume & Issues
Volume 2, Issue 4 - Nov 2012
Volume 2, Issue 3 - Aug 2012
Volume 2, Issue 2 - May 2012
Volume 2, Issue 1 - Feb 2012
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An Improved Guidance Algorithm for Smooth Transition at Way-Points in 3D Space for Autonomous Underwater Vehicles
Subramanian, Saravanakumar ; Thondiyath, Asokan ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 139~150
DOI : 10.5574/IJOSE.2012.2.3.139
This paper presents an improved guidance algorithm for autonomous underwater vehicles (AUV) in 3D space for generating smoother vehicle turn during the course change at the way-points. The way-point guidance by the line-of-sight (LOS) method has been modified for correcting the reference angles to achieve minimal calculation and smoother transition at the way-points. The algorithm has two phases in which the first phase brings the vehicle to converge to a distance threshold point on the line segment connecting the first two way-points and the next phase generates an angular path with smoother transition at the way-points. Then the desired angles are calculated from the reference and correction angles. The path points are regularly parameterized in the spherical coordinates and mapped to the Cartesian coordinates. The proposed algorithm is found to be simple and can be used for real time implementation. The details of the algorithm and simulation results are presented.
Experimental Study on Impact Loads Acting on Free-falling Modified Wigley
Hong, Sa-Young ; Kim, Young-Shik ; Kyoung, Jo-Hyun ; Hong, Seok-Won ; Kim, Yong-Hwan ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 151~159
DOI : 10.5574/IJOSE.2012.2.3.151
The characteristics of an impact load and pressure were experimentally investigated. Drop tests were carried out using a modified Wigley with CB = 0.56. The vertical force, pressures, and vertical accelerations were measured. A 6-component load cell was used to measure the forces, piezo-electric sensors were used to capture the impact pressure, and strain-gauge type accelerometers were used to measure the vertical accelerations. A 50-kHz sampling rate was applied to capture the peak values. The repeatability of the measured data was confirmed and the basic characteristics of the impact load and pressure such as the linearity to the falling height were observed for all of the measurements. A simple formula was derived to extract the physical impact load from the measured force based on a simple mass-sensor-mass diagram, which was validated by comparing impact forces with existing data using the mathematical model of Faltinsen and Chezhian (2005). The effects of the elasticity of the model and change in acceleration during the water entry were investigated. It is interesting to observe that the impact loads occurred and reached peak values at the same time duration after water entry for all drop heights.
Variability of Fatigue Crack Initiation Life in Flux Cored Arc Welded API 2W Gr.50 Steel Joints
Sohn, Hye-Jeong ; Kim, Seon-Jin ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 160~169
DOI : 10.5574/IJOSE.2012.2.3.160
Flux Cored Arc Welding (FCAW) is a common practice to join thick plates such as the structural members of large scale offshore structures and very large container ships. The objective of this study was to investigate the mechanical properties and variability of the fatigue crack initiation life in the flux cored arc welded API 2W Gr.50 steel joints typically applied to offshore structures with a focus on the effect of the materials in fatigue crack growth life from the notch root of a compact tension specimen. Offshore structural steel (API 2W Gr.50) plates (60-mm thick) were used to fabricate multi-path flux core arc welded butt welded joints to clearly consider fatigue fractures at the weld zone from the notch. Fatigue tests were performed under a constant amplitude cyclic loading of R = 0.4. The mean fatigue crack initiation life of the HAZ specimen was the highest among the base metal (BM), weld metal (WM), and heat affected zone (HAZ). In addition, the coefficient of variation was the highest in the WMl specimen. The variability of the short fatigue crack growth rates from the notch tips in the WM and HAZ specimens was higher than in BM.
Model based Simulation of Container Loading/Unloading
Lee, Soon-Sup ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 170~175
DOI : 10.5574/IJOSE.2012.2.3.170
Currently, most logistics use containers. The construction of new port and high speed medium size container ship for the transportation of merchandise have become very important. The problem of ship stability is also important because of its direct influence on the loss of human life, ships, and merchandise. The stability of a container ship during its operation is not a large problem because it is well considered in the design process. However, the assessment of ship stability during container loading/unloading in port still depends on the expertise of experienced personnel. In this paper, a model based simulation system is introduced, which is able to assess ship stability during container loading/unloading, using ENVISION, a general purpose simulation system.
Numerical Study on Floating-Body Motions in Finite Depth
Kim, Tae-Young ; Kim, Yong-Hwan ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 176~184
DOI : 10.5574/IJOSE.2012.2.3.176
Installing floating structures in a coastal area requires careful observation of the finite-depth effect. In this paper, a Rankine panel method that includes the finite-depth effect is developed in the time domain. The bottom boundary condition is satisfied by directly distributing Rankine panels on the bottom surface. A stepwise analysis is performed for the radiation diffraction problems and consequently freely-floating motion responses over different water depths. The hydrodynamic properties of two test hulls, a Series 60 and a floating barge, are compared to the results from another computation program for validation purposes. The results for both hulls change remarkably as the water depth becomes shallower. The important features of the results are addressed and the effects of a finite depth are discussed.
Progress of Composite Fabrication Technologies with the Use of Machinery
Choi, Byung-Keun ; Kim, Yun-Hae ; Ha, Jin-Cheol ; Lee, Jin-Woo ; Park, Jun-Mu ; Park, Soo-Jeong ; Moon, Kyung-Man ; Chung, Won-Jee ; Kim, Man-Soo ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 185~194
DOI : 10.5574/IJOSE.2012.2.3.185
A Macroscopic combination of two or more distinct materials is commonly referred to as a "Composite Material", having been designed mechanically and chemically superior in function and characteristic than its individual constituent materials. Composite materials are used not only for aerospace and military, but also heavily used in boat/ship building and general composite industries which we are seeing increasingly more. Regardless of the various applications for composite materials, the industry is still limited and requires better fabrication technology and methodology in order to expand and grow. An example of this is that the majority of fabrication facilities nearby still use an antiquated wet lay-up process where fabrication still requires manual hand labor in a 3D environment impeding productivity of composite product design advancement. As an expert in the advanced composites field, I have developed fabrication skills with the use of machinery based on my past composite experience. In autumn 2011, the Korea government confirmed to fund my project. It is the development of a composite sanding machine. I began development of this semi-robotic prototype beginning in 2009. It has possibilities of replacing or augmenting the exhaustive and difficult jobs performed by human hands, such as sanding, grinding, blasting, and polishing in most often, very awkward conditions, and is also will boost productivity, improve surface quality, cut abrasive costs, eliminate vibration injuries, and protect workers from exposure to dust and airborne contamination. Ease of control and operation of the equipment in or outside of the sanding room is a key benefit to end-users. It will prove to be much more economical than normal robotics and minimize errors that commonly occur in factories. The key components and their technologies are a 360 degree rotational shoulder and a wrist that is controlled under PLC controller and joystick manual mode. Development on both of the key modules is complete and are now operational. The Korean government fund boosted my development and I expect to complete full scale development no later than 3rd quarter 2012. Even with the advantages of composite materials, there is still the need to repair or to maintain composite products with a higher level of technology. I have learned many composite repair skills on composite airframe since many composite fabrication skills including repair, requires training for non aerospace applications. The wind energy market is now requiring much larger blades in order to generate more electrical energy for wind farms. One single blade is commonly 50 meters or longer now. When a wind blade becomes damaged from external forces, on-site repair is required on the columns even under strong wind and freezing temperature conditions. In order to correctly obtain polymerization, the repair must be performed on the damaged area within a very limited time. The use of pre-impregnated glass fabric and heating silicone pad and a hot bonder acting precise heating control are surely required.
New Analytical Method with Curvature Based Kinematic Deflection Curve Theory
Tayyar, Gokhan Tansel ;
International Journal of Ocean System Engineering, volume 2, issue 3, 2012, Pages 195~199
DOI : 10.5574/IJOSE.2012.2.3.195
This paper reports a new analytical method to calculate the planar displacement of structures. The cross-sections were assumed to remain in plane and the deflection curve was evaluated using the curvature values geometrically, despite being solved with differential equations. The deflection curve was parameterized with the arc-length of the curvature values, and was taken as an assembly of chains of circular arcs. Fast and accurate solutions of complex deflections can be obtained easily. This paper includes a comparison of the nonlinear displacements of an elastic tapered cantilever beam with a uniform moment distribution among the proposed analytical method, numerical method of the theory and large deflection FEM solutions.