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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Ocean Engineering and Technology
Journal Basic Information
Journal DOI :
Korean Society of Ocean Engineers
Editor in Chief :
Volume & Issues
Volume 25, Issue 6 - Dec 2011
Volume 25, Issue 5 - Oct 2011
Volume 25, Issue 4 - Aug 2011
Volume 25, Issue 3 - Jun 2011
Volume 25, Issue 2 - Apr 2011
Volume 25, Issue 1 - Feb 2011
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Development of Digital Gas Metal Arc Welding System and Welding Current Control Using Self-tuning Fuzzy PID
Doan, Phuc Thinh ; Pratama, Pandu Sandi ; Kim, Suk-Yoel ; Kim, Hak-Kyeong ; Yeun, Hwang-Yeong ; Byun, Gi-Sig ; Kim, Sang-Bong ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 1~8
DOI : 10.5574/KSOE.2011.25.6.001
This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.
Extraction of Wave Energy Using the Coupled Heaving Motion of a Circular Cylinder and Linear Electric Generator
Cho, Il-Hyoung ; Kweon, Hyuck-Min ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 9~16
DOI : 10.5574/KSOE.2011.25.6.009
The feasibility of wave energy extraction from a heaving truncated cylinder and the corresponding response of the linear electric generator (LEG) composed of spring, magnet, and coil has been investigated in the frame of three-dimensional linear potential theory. The heaving motion of a circular cylinder is calculated by means of the matched eigenfunction expansion method. Further, the analytical results are validated by numerical results using the ANSYS AQWA commercial code. By the action of a heaving circular cylinder, the magnet suspended by a spring can slide vertically inside the heaving cylinder. The mechanical power is extracted from the magnet motion relative to the coil/stator which is attached to the cylinder. The coupled ODE of a heaving cylinder and LEG system in waves is derived to obtain the magnet motion relative to a cylinder. To maximize the relative motion of the magnet, both the buoy draft and the LEG system parameters (spring stiffness, damping) should be selected properly for generating the double resonance considering the peak frequency of the target spectrum.
Study on Motion Response Characteristics for Large Inclined State of Small Fishing Vessel in Beam Sea Condition
Park, Ro-Sik ; Kim, Seong-Gun ; Lee, Jin-Bok ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 17~22
DOI : 10.5574/KSOE.2011.25.6.017
This study conducted wide-tank experiments and numerical calculations for a vessel in various positions such as upright and inclined by 2 and 4 degrees, with the goal of investigating the motion amplitude response of a small damaged fishing boat subject to a beam sea. Numerical calculations were conducted based on the three-dimensional source distribution method. The good agreement of the numerical calculation and experimental results confirmed that the present calculation method can be efficiently used for the initial design of a small fishing boat. In addition, while the chine-line type has been frequently adopted to improve a ship's resistance performance in the design of a small fishing boat, it is considered that the possibility of a deterioration in rolling performance should be thoroughly considered.
On Propagation of Ship Induced Waves in 3-D Numerical Wave Basin with Non-Reflected Wave Generation System
Lee, Woo-Dong ; Hur, Dong-Soo ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 23~28
DOI : 10.5574/KSOE.2011.25.6.023
In this paper, a new generation method for ship induced waves is proposed using the fully non-linear 3-D numerical model with non-reflected wave generation system (LES-WASS-3D). A ship induced wave generated by the newly proposed method is examined in comparison with that obtained by an empirical formula. It is then shown that there is a good agreement in free surface the elevation between them. As a result, it is revealed that a ship induced wave in a 3-D numerical wave field can be simulated well using LES-WASS-3D.
Study of Wave Absorbing Effect of Submerged Breakwater
Lee, Hyun-Jin ; Shin, Moon-Seup ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 29~34
DOI : 10.5574/KSOE.2011.25.6.029
Various types of coastal structures have been constructed to prevent coastal disasters. Among these coastal structures, submerged breakwaters have been used more widely than all of the other coastal structures because of their excellent advantages in scenery effects, construction efficiency, and environmental benefits. This study investigated the potential of the horizontal plate submerged breakwater model. Usually, it is necessary for a submerged breakwater to minimize and compensate for the negative impacts on the marine environment and ecosystem caused by the marine construction. Thus, the prevention of coastal disasters was verified for this submerged breakwater model, regardless of its function as a fish reef. The purpose of this study was to investigate the hydraulic characteristics with changes in the crest width and porosity of a horizontal plate submerged breakwater and compare the results of this study with the results of other studies on permeable and impermeable submerged breakwaters.
Evaluation of Bearing Capacities of Large Size Non-welded Composite Piles by 3-Dimensional Numerical Analysis
Park, Jae-Hyun ; Kim, Sung-Ryul ; Le, Chi-Hung ; Chung, Moon-Kyung ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 35~41
DOI : 10.5574/KSOE.2011.25.6.035
Recently, as large structures, which should support large design loads have been constructed, the study on the large diameter composite pile becomes necessary. The large diameter composite pile has the diameter over 700mm and consists of two parts of the upper steel pipe pile and the lower PHC pile by a mechanical joint. In this research, to analyze the bearing capacity and the material strength of the composite pile, three dimensional numerical analyses were performed. First, the numerical modeling method was verified by comparing the calculated load-movement curves of the pile with those of the field pile load tests. Then, a total of twelve analyses were performed by varying pile diameter and loading direction for three pile types of PHC, steel pipe and composite piles. The results showed that the vertical and the horizontal load-movement curves of the composite pile were identical with those of the steel pipe pile and the horizontal material strength of the composite pile was 60-80% larger than that of the PHC pile.
Variation of Axial Tension-Compression Fatigue Characteristics by UNSM on Ti-6Al-4V
Suh, Chang-Min ; Cho, Sung-Am ; Pyoun, Young-Sik ; Suh, Min-Soo ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 42~48
DOI : 10.5574/KSOE.2011.25.6.042
The present study makes three original contributions to nanoskinned Ti-6Al-4V materials. The nanoskins were fabricated on Ti-6Al-4V material using various surface treatments: deep rolling (DR), laser shot peening (LSP), and ultrasonic nanocrystal surface modification (UNSM). These surface treatments are newly developed techniques and are becoming more popular in industrial fields. A fatigue strength comparison at up to 106 cycles was conducted on these nanoskinned Ti-6Al-4V materials. Fatigue tests were carried out using MTS under axial loading tension-compression fatigue (R = -1, RT, 5 Hz, sinusoidal wave). The analysis of the crack initiation patterns in the nanoskinned Ti-6Al-4V materials found an interior originating crack pattern and surface originating crack type. Microscopic observation was mainly used to investigate the fatigue fractured sites. These surface modification techniques have been widely adopted, primarily because of the robust grade of their mechanical properties. These are mainly the result of the formation of a large-scale, deep, and useful compressive residual stress, the formation of nanocrystals by the severe plastic deformation (SPD) at the subsurface layer, and the increase in surface hardness.
Variation of Rotating Bending Fatigue Characteristics by UNSM on Ti-6Al-4V
Suh, Chang-Min ; Pyoun, Young-Sik ; Suh, Min-Soo ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 49~55
DOI : 10.5574/KSOE.2011.25.6.049
In order to analyze feasibility of replacing a conventional 6-mm Ti bar with a 5-mm bar, a series of rotating bending fatigue tests were carried out on Ti-6Al-4V bars by strengthening the fatigue performance using a special technique called UNSM (Ultrasonic Nanocrystal Surface Modification). The results of S-N curves clearly showed that the performance of the 5-mm titanium specimen was similar to that of the 6-mm specimen when the UNSM treatment was applied. The 5-mm treated specimen converged with small scattering band into the linear line of the non-treated 6-mm one. Below the fatigue life of
cycles, the UNSM treatment did not show any significant superiority in the bending stress and fatigue life. However, over the fatigue life of
cycles, the effect of UNSM was superior for each fatigue life, and the bending stress became longer and higher than that of the untreated one. In the case of 6-mm Ti-bar with UNSM, the fatigue limit was about 592 MPa, and there was fatigue strength increase of about 30.7% at the fatigue life of
cycles compared to the untreated 6-mm bar. Therefore, the compressive residual stress made by the UNSM in Ti-6Al-4V increased the fatigue strength by more than 30%.
Corrosion Resistance of Cold Rolled Steel coated Organic/inorganic Hybrid Coating Solution According to Heat Treatment Temperature
Nam, Ki-Woo ; Kim, Jung-Ryang ; Choi, Chang-Min ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 56~59
DOI : 10.5574/KSOE.2011.25.6.056
The demand for cold rolled steel (CR) for structural members is gradually increasing. If no surface treatment (coating for corrosion resistance) for CR is conducted, its use is very limited because CR is vulnerable to corrosion. Therefore, we need to develop a coating solution to provide high corrosion resistance for CR. In this study, an organic/inorganic coating solution with Si and Ti (Si polysilicate 7 wt.% + Urethane 13 wt.% + Ti amorphous 0.5 wt.%; LR-0727(1)) was used to evaluate the corrosion resistance of CR under a salt spray test. The specimens with the LR-0727(1) coating were heat treated in a drying oven at
for 5 min. The corrosion resistance was investigated using a salt spray test of 7 h. In addition, an adhesive test was conducted. Rust showed under a heat treatment of
, but no vestiges were found over
. The specimens with heat treatment at
or more did not experience delamination. From these results, it is considered that the temperature limit for optimum heat treatment is
considering energy efficiency.
Influence of Treatment Temperature on Surface Characteristics during Low Temperature Plasma Carburizing and DLC duplex treatment of AISI316L Stainless Steel
Lee, In-Sup ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 60~65
DOI : 10.5574/KSOE.2011.25.6.060
A low temperature plasma carburizing process was performed on AISI 316L austenitic stainless steel to achieve an enhancement of the surface hardness without degradation of its corrosion resistance. Attempts were made to investigate the influence of the processing temperatures on the surface hardened layer during low temperature plasma carburizing in order to obtain the optimum processing conditions. The expanded austenite (
) phase, which contains a high saturation of carbon (S phase), was formed on all of the treated surfaces. Precipitates of chromium carbides were detected in the hardened layer (C-enriched layer) only for the specimen treated at
. The hardened layer thickness of
increased up to about
with increasing treatment temperature. The surface hardness reached about 900
, which is about 4 times higher than that of the untreated sample (250
). A minor loss in corrosion resistance was observed for the specimens treated at temperatures of
compared with untreated austenitic stainless steel. In particular, the precipitation of chromium carbides at
led to a significant decrease in the corrosion resistance. A diamond-like carbon (DLC) film coating was applied to improve the wear and friction properties of the S phase layer. The DLC film showed a low and stable friction coefficient value of about 0.1 compared with that of the carburized surface (about 0.45). The hardness and corrosion resistance of the S phase layer were further improved by the application of such a DLC film.
Study on Residual Stress Distribution in Thick Plate Welded Material Using Indentation Equipment
Huh, Sun-Chul ; Kim, Gwi-Nam ; Lee, Jong-Seok ; Park, Cheol-Hong ; Park, Joun-Sung ; Park, Won-Jo ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 66~71
DOI : 10.5574/KSOE.2011.25.6.066
Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.
VHCF Characteristics of A7075-T651 under Pressure Variation by Shot Peening Treatment
Suh, Chang-Min ; Kim, Cheol ; Kim, Tae-Joon ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 72~79
DOI : 10.5574/KSOE.2011.25.6.072
In this paper, the fatigue characteristics of shot peened A7075-T651 alloy were compared with those of the specimens without the shot peening. The multi-spindle and single-spindle rotating bending fatigue testing machines were employed for the evaluation. Shot peening (SP) with various pressure (5 psi, 10 psi, 15 psi, 25 psi and 35 psi) were used in this test. In order to investigate the effect of the applied pressure during the SP, we carried out the surface roughness test, compressive residual stress test, hardness test, tensile test, VHCF (Very high cycle fatigue) test and SEM observation. SP induced the formation of remarkable compressive residual stress from the surface to certain depth of sample by means of the plastic deformation. The surface hardness and the fatigue characteristics of the specimens were also modified by the SP. According to the S-N curves, fatigue lives of shot peended sample with 25 psi measures 50 times higher than that of the untreated sample. The fatigue lives of shot peened sample with 15 psi and 35 psi measure approximately 10 times higher than that of the untreated ones.
UNSM Surface Technology for Manufacturing and Remanufacturing Torsion Bars for Crawler Vehicles
Suh, Chang-Min ; Pyoun, Young-Sik ; Cho, In-Ho ; Baek, Un-Bong ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 80~85
DOI : 10.5574/KSOE.2011.25.6.080
The Ultrasonic Nanocrystal Surface Modification (UNSM) technology improves the fatigue life of a torsion bar by inducing compressive residual stress on the surface layer. The UNSM is applied to replace the presetting method and shot peening technology. The torsion bar must be changed periodically because of a lack of durability and a phenomenon related to the stress relaxation. The torsion fatigue test specimens were made of DIN17221 material, and the results showed that the fatigue life was 5 times more than under durability test conditions. A comparison test between the commercial vehicles' presetting method and shot peened torsion bar and the UNSM torsion bar showed that the UNSM could replace the presetting method and shot peening.
Analysis of Structural Characteristics of HDPE Pipe for Manganese Lifting Test
Lee, Jae-Hwan ; Yoon, Chi-Ho ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 86~90
DOI : 10.5574/KSOE.2011.25.6.086
The mining of imitated manganese noodles in 1000 m of seawater is planned for 2012. Thus, it is necessary to prepare the lifting pipes to be used for the test. Because of storage and expense constraints, flexible and economic HDPE pipe is being considered, making it necessary to test the structural safety. Material, pressure-chamber tests and finite element analysis of HDPE pipe for the 1000-m depth were performed. The tangential stiffness of HDPE was obtained through tension and three-point bending material tests and used for a structural analysis. FEA results show that the current sample pipe segment is safe for 1000 m of water pressure, and the stress result is also within the safe value. From the current results, the HDPE pipe seems to be acceptable only for the currently suggested constraints. However, more numerical and pressure tests need to be considered by applying additional physical conditions such as gravitational and hydrodynamic loads, external and internal fluid pressure, axial force induced ship motion, and heavy pump pressure to determine future usage.
Friction Welding and AE Characteristics of Magnesium Alloy for Lightweight Ocean Vehicle
Kong, Yu-Sik ; Lee, Jin-Kyung ; Kang, Dae-Min ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 91~96
DOI : 10.5574/KSOE.2011.25.6.091
In this paper, friction welded joints were constructed to investigate the mechanical properties of welded 15-mm diameter solid bars of Mg alloy (AZ31B). The main friction welding parameters were selected to endure reliable quality welds on the basis of visual examination, tensile tests, impact energy test, Vickers hardness surveys of the bonds in the area and heat affected zone (HAZ), and macrostructure investigations. The study reached the following conclusions. The tensile strength of the friction welded materials (271 MPa) was increased to about 100% of the AZ31B base metal (274 MPa) under the condition of a heating time of 1 s. The metal loss increased lineally with an increase in the heating time. The following optimal friction welding conditions were determined: rotating speed (n) = 2000 rpm, heating pressure (HP) = 35 MPa, upsetting pressure (UP) = 70 MPa, heating time (HT) = 1 s, and upsetting time (UT) = 5 s, for a metal loss (Mo) of 10.2 mm. The hardness distribution of the base metal (BM) showed HV55. All of the BM parts showed levels of hardness that were approximately similar to friction welded materials. The weld interface of the friction welded parts was strongly mixed, which showed a well-combined structure of macro-particles without particle growth or any defects. In addition, an acoustic emission (AE) technique was applied to derive the optimum condition for friction welding the Mg alloy nondestructively. The AE count and energy parameters were useful for evaluating the relationship between the tensile strength and AE parameters based on the friction welding conditions.
Effect of Quenching Heat-treatment on Mechanical Properties and Microstructure of Modified C95600 Bronze
Lee, Sung-Yul ; Moon, Kyung-Man ; Oh, Jae-Hwan ; Shin, Dong-Il ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 97~104
DOI : 10.5574/KSOE.2011.25.6.097
Modified C95600 bronze contains Fe component of 0.7 weight percentage besides Cu-7Al-2.5Si composition. The shape of centrifugal cast is a circular pipe with thick wall. Specimens machined from the centrifugal cast were quenched in oil after isothermal holding at a given heat treatment temperature in the range of
. Mechanical properties and structural morphology are depended on the quenching heat treatment temperature regardless of isothermal holding time. Tensile strength or Brinell hardness is increased with increasing heat treatment temperature. The microstructure caused by quenching contains mixing phases of
which martensite of
phase has been transformed from
phase. Effect of isothermal holding temperature on mechanical properties in case of quenching heat treatment attributes to the change of volume fraction of
on the structural morphology. Mechanical characteristics of specimen, initially quenched from
, and then tempered at
, does not show an obvious softening indication, because disappearance of
during tempering process can be compensated by precipitation of brittle phase
Deformation Characteristics of Intermittent Fillet Welding
Lee, Joo-Sung ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 105~109
DOI : 10.5574/KSOE.2011.25.6.105
As is well appreciated, welding is the most important fundamental process in manufacturing marine structures. However, weld-induced deformation is inevitable because of the non-uniform distribution of temperature during welding. The deformation caused by welding is one of the principal obstacles in enhancing the productivity in the manufacturing procedure for marine structures. This should be much more seriously considered in the case of the thin blocks found in a ship with multi-deck structures. This paper is concerned with the deformation control of thin panel blocks by applying intermittent welding to fillet welding. In order to investigate the quantitative effect of the intermittent welding, a thermo elasto-plastic analysis was carried out with various welding pitches and plate thicknesses. Welding tests were also carried out to show the validity of the present thermo-elasto-plastic analysis. Numerical analysis results showed good agreement with those of the welding tests. As far as the present numerical results are concerned, it has been seen that a more than 50% reduction in angular distortion can be achieved by applying the intermittent welding because of the low heat input.
Long-term Consolidation Characteristics of Busan Clay considering OC or NC States
Kim, Yun-Tae ; Jo, Sang-Chan ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 110~115
DOI : 10.5574/KSOE.2011.25.6.110
Numerouslong-term consolidation and secondary compression settlements may occur in Busan clay, which is astructured soft clay and consists of a thick clay deposit. As a surcharge load is applied to soils, soils experience different stress paths with depth. Therefore, it is necessary to study the long-term consolidation behavior of Busan clay considering stress conditions such as OC or NC states. In this study, a series of long-term consolidation tests were performed to investigate the consolidation characteristics of Busan clay for 20 days. The undisturbed clay samples were taken from 3 sites located in the Nakdong River estuary. The results showed that the creep rate of the Busan clay gradually decreased with time, which indicated that the secondary compression settlement decreased with time. In addition, the experimental results for 3 samples showed that the ratios were about 0.0363 and 0.051, respectively.
Development of Realtime Simulator for Multibody Dynamics Analysis of Wheeled Vehicle on Soft Soil
Hong, Sup ; Kim, Hyung-Woo ; Cho, Yun-Sung ; Cho, Hui-Je ; Jung, Ji-Hyun ; Bae, Dae-Sung ;
Journal of Ocean Engineering and Technology, volume 25, issue 6, 2011, Pages 116~122
DOI : 10.5574/KSOE.2011.25.6.116
A realtime simulator using an explicit integration method is introduced to improve the solving performance for the dynamic analysis of a wheeled vehicle. Because a full vehicle system has many parts, the development of a numerical technique for multiple d.o.f. and ground contacts has been required to achieve a realtime dynamics analysis. This study proposes an efficient realtime solving technique that considers the wheeled vehicle dynamics behavior with full degrees of freedom and wheel contact with soft ground such as sand or undersea ground. A combat vehicle was developed to verify this method, and its dynamics results are compared with commercial programs using implicit integration methods. The combat vehicle consists of a chassis, double wishbone type front and rear suspension, and drive train. Some cases of vehicle dynamics analysis are carried out to verify the realtime ratio.