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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
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Korean Society of Ocean Engineers
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Volume 1, Issue 2 - Dec 1987
Volume 1, Issue 1 - Jul 1987
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On the Wave Loads on a Large Volume Offshore Structure
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 33~38
The first order mation responses of a floating structure and the hydrodynamic forces in regular waves are obtained by means of the linear potential theory. The first order potential is obtained directly from the numerical solution of the improved Green integral equation which is characterized by the combined surface distribution of sources and normal doublets. The mean second order wave drift force is also calculated by means of the near field method. It seems that the present method gives more accurate numerical results than other methods and the agreement between numerical and experimental results appears to be satisfactory.
Fatigue Analysis for Transportation of Harmony Jacket
Kim, D. Y. ;
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 39~48
The Motion Characteristics of a Marine Riser in Regular Wave Condition
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 49~56
The dynamic behaviour of a marine riser was studied theoretically and experimentally. In linear analysis, the natural frequencies and mode shapes of the riser were obtained from the experiment and they were found to be in good agreement with theoretical results by using a simple asymptotic formula. In nonlinear ananlysis including viscous drag and large displacement, a numerical-perturbation technique based on the derived linear asymptotic solutions is used to predict the displacements and stresses of the riser in harmonic motion. These results were also compared with experimental data and found to be in general in good agreement.
Dynamic Analysis of Guyed Tower Subjected to Random Waves
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 57~64
Methods of nonlinear stochastic analysis of guyed towers are studied in this paper. Two different kinds of nonlinearities are considered. They are the nonlinear restoring force from the guying system and the nonlinear hydrodynamic force. Analyses are carried out mainly in the frequency domain using linearization techniques. Two methods for the linearization of the nonlinear stiffness are presented, in which the effects of the steady offset and the oscillating component of the structural motion can be adequately analyzed. those two methods are the equivalent linearization method and the average stiffness method. The linearization of the nonlinear drag force is also carried out considering the effect of steady current as well as oscillatory wave motions. Example analyses are performed for guyed tower in 300m water. Transfer functions and the expected maximum values of the deck displacement and the bending moment near the middle of the tower are calculated. Numerical results show that both of the frequency domain methods presented in this paper predict the responses of the sturcture very reasonably compared with those by the time integration method utilzing the random simulations wave particla motions.
Induced steady flow around two oscillating circular cylinders
Suh, Y. K. ;
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 65~72
The Development of an Early Production System off the Coast of Korea
Yu, Byung-Kun ;
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 73~83
An Experimental Study on the Beach Nourshment Method of HAE UN DAE Beach
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 84~93
A beach nourishment method can be used as one of the beach erosion protection methods which may keep coastal environments whithout constructing coastal structures on the HAE UN DAE beach. The beach nourishmens is affected by a natural condition and artificial condition;a natural condition includes conditions of bottom slope, diameter of bottom materials and waves, and artificial conditions include deposit position, method, diameter and quantity of the nourishing sand. It has accomplished to obtain the deposit position and the best diameter of the nourishing sand from a two-dimensional hydraulic model test, which simulates the erosional HAE UN DAE beach. In this study, the protection of the beach erosion can be maximized when the nourishing sand of 3.3mm in diameter, which is about 5.5.times of the bottom materials in diameter, is deposited layerly in front of the breaker zone which has a water depth of 4.6m.
Application of Fracture Mechanics Method to Ottshore Structural Crack Instability Analysis
Rhee, H. C. ;
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 94~103
A Basic Study on Growth Characteristics of the Small Surface Crack in 21/4 Cr-1 Mo Steel
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 104~110
Fatigue tests by axial loading (R = 0.05) were carried out to investigate fatigue crack growth characteristics of small surface cracks in 2 1/4 Cr-1 Mo steel at room temperature by using flat specimens with a small artificial pit. All the data of the fatigue crack growth rate obtained in the present test are determined as a function of the stress intensity factor range about a semi-elliptical crack, so that the application of linear fracture mechanics to the surface fatigue crack growth and to the fatigue crack growth into depth, and all the data obtained from tests were discussed in comparison with the data of Type 304 stainless steel and two type of mild steel under the same test conditions. The obtained results are as follows: 1)When the cycle ratios are same, surface fatigue crack length and its depth are almost same and fall within a narrow scatter band in spite of different stress levels. 2)Relations of the surface fatigue crack growth rate (da/dN) and fatigue crack growth rate into depth (db/dN) to its stress intensity factor range (
) can be plotted as a straight line at log-log diagram without dependence of stress level and coincide with the data of part-through crack in various steels.
The effects of 3.5% NaCl solution on the corrosion fatigue crack propagation characteristics of SS41 steel
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 111~119
The corrosion fatigue crack propagation characteristics of SS41 steel in 3.5% NaCl solution have been evaluated for loading frequencies of 1Hz and 0.2Hz. A sine wave loading profile was used for fatigue testing. Each test was carried out at a constant stress ratio, R(0.1). The main results are summarized as follows; 1. Fatigue crack propagation rate was higher in 3.5% NaCl solution than in air, higher in the base metal than in the weld metal, and higher at f =0.2Hz than at f =1Hz. 2. The crack closure level of the base metal was not influenced by cyclic frequencies, but that of the weld metal was much influenced. 3. When the crack closure effect was eliminated in the evaluation of crack propagation characteristics by using
, the envirommental influence was distinctly observed. At the base metal, crack propagation rate was enhanced by the hydrogen embrittlement, and the weld metal was reduced by the crac closure. 4. There was clearly observed hydrogen embrittlement and severely corroded aspect at fracture surface of lower frequency than that of higher frequency, and at that of base metal than that of the weld metal.
Effect of Welding Heat Input on Mechanical Properties of Underwater Welded Joints of KR Grade A-1 Steel Plates
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 120~126
In this paper, the optimizing investigation of characteristics of underwater welding by a gravity type arc welding process is experimentally carried out by using the .phi. 4mm ilmenite type of domestic coated welding electrodes for welding the domestic marine structural steel plates of 8mm thickness in order to develop the underwater welding techniques in practical use, resulting in the quantitative analysis possibility for the relationship between the mechanical propernical properties of underwater welded joint HAZ and the welding heat input.
Evaluation of Fracture Toughness on High Frequency Electric Resistance Welded API 5LB Steel Pipe
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 127~137
The evaluation of the elastic-plastic fracture toughness
was performed on the center of weld metal(CWM), the heat affected zone (HAZ) and the base metal (BM) of API 5LB steel pipes welded by the high frequency electric resistance welding. The
was evaluated by the JSME R-Curve and JSME SZW methods using the smooth and side-grooved specimens. The results are as follows; (1) The
values by the SZW method are overestimated as compared with those by the R-curve method, because the micro-crack is formed as SZW increase with the deformation at SZ after initiation of the ductile crack. (2) The everage of
values by the the R-curve and the SZW methods in side-grooved specimens tended to decrease in comparison with smooth specimens 9.42% at CWM, 4.2% at HAZ, 23.2% at BM, respectively. (3) The boundary of the fatigue pre-crack, stretched zone, and dimple regions appeared more clearly in side-grooved specimens, for the slight change of SZW in the direction of the plate thickness, as compared with smooth specimens.
The Relationship between Welding Conditions and Ultrasonic Reflection Coefficients of Dissimilar Metals Friction Welded Joints
Journal of Ocean Engineering and Technology, volume 1, issue 1, 1987, Pages 138~143
Friction welding has emerged as a reliable process for high-production commercial applications with significant economic and technical advantages. But nondestructive test in friction weld was not clearly developed. Therefore the experimental verification is necessary in order to understand the characteristcs of the pulse echo effects according to various change in welding conditions. This paper presents an attempt to determine the relationship between the varios welding conditions and the coefficients of reflection using the ultrasonic pulse echo method in dissibilar metals friction weld. The new approach of calculating the coefficients of reflection based on measured amplitudes of the echoes is applied in this paper. These coefficients provides a single quantitative measurement which involves both acoustic energy reflected at the welded interface as well as transmitted across the interface. As a result, it was known that the quantitave relationship between welding conditions and the coefficients of reflection using the ultrasonic pulse echo exists in dissimilar metals friction weld.