• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.338-344
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• 2022

Roll moment usually is ignored when analyzing the maneuverability of surface ships. However, it is well known that the influence of roll moment on maneuverability is significant for ships with small metacentric height such as container ships, passenger ships, etc. In this study, a pure roll test is performed to determine the hydrodynamic derivatives with respect to roll motion as added mass and damping. The target ship is an autonomous surface ship designed to carry containers with a small drift and large freeboard. The commercial code of STAR CCM+ software is applied as a specialized tool in naval hydrodynamic based on RANS equation for simulating the pure roll of the ship. The numerical uncertainty analysis is conducted to verify the numerical accuracy. By distinguishing the in-phase and out-of-phase from hydrodynamic forces and moments due to roll motion, added mass derivatives and damping derivatives relative to roll angular velocity are obtained.

• Journal of Navigation and Port Research
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• v.45 no.1
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• pp.16-25
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• 2021

Hydrodynamic coefficients should be accurately estimated to predict the maneuverability of underwater vehicles. Various captive model tests have been performed as part of estimation methods for these coefficients. Estimating hydrodynamic coefficients related to roll motion is important because underwater vehicles are sensitive to changes of roll moment. In this research, a pure roll motion equipment was newly designed to simply estimate hydrodynamic coefficients with respect to roll motion. Roll motion was implemented through a brief mechanical mechanism. The principle of operation, application process, and system identification of the equipment are described. An analysis method of the pure roll test is also suggested. Repeated tests of the newly equipment were carried out to check its reproducibility.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.169-173
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• 2001

This study presents the results of decoupling of free decay roll test data by discrete wavelet transform. Free roll decay test was performed to decide the coefficients of damping terms in equation of motion. During the experiment, a slight yaw motion was found while the model was in the free roll decay motion. Discrete wavelet transform was applied to the signal to extract the pure roll motion. The results were compared to those of the Fourier transform. DWT was able to decouple the two signals efficiently while the Fourier transform was not.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.540-541
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• 2006

SUS316L stainless steel, commercial pure Titanium and Ti-6Al-4V alloy powders applied by Mechanical Milling (MM) process are sintered by Hot Roll Sintering (HRS) process. Microstructure and mechanical properties of those HRS materials is investigated. The microstructures of materials produced by HRS process consist of fine grains and work-hardened structure, that is, the hybrid microstructure. Tensile test of the HRS material demonstrated the good mechanical properties. These results show that the HRS process is very effective to the improvement of mechanical properties in the SUS316L stainless steel, commercial pure Titanium and Ti-6Al-4V alloy.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.555-559
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• 2005

An oxygen free copper severely-deformed by eight cycles (an equivalent strain of $\~6.4$) of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $300^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $150^{\circ}C$, however above $200^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. Tensile strength and hardness of the copper decreased slightly with the annealing temperature up to $150^{\circ}C$, however they dropped largely above $200^{\circ}C$. Annealing characteristics of the copper were compared with those of a commercially pure aluminum processed by ARB and subsequently annealed.

• Journal of Environmental Science International
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• v.13 no.4
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• pp.421-427
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• 2004

With the help of mechanical mixing method such as Banbury mixer and open 2 roll mill, ethylene propylene diene terpolymer (EPDM) was blended with the chloroprene rubber (CR) then mechanical properties and ozone resistance test of blends were subsequently investigated. It was noted that the hardness increased with an increasing of CR contents. Generally the hardness was increased with heat aging time most likely due to the post cure. In ozone resistance test of blend, after 8 hours a portion of fine crack is obtained for pure CR. It is confirmed that ozone resistance is greatly improved by addition of 25wt% EPDM to CR.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.73-77
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• 2001

This study examined blends of styrene butadiene rubber(SBR) and chloroprene rubber(CR) prepared from an open 2-roll mill following the conventional polymer blend method for a wide range of the blend composition. Rubber vulcanizates were manufactured by hot press and then mechanical properties, heat and ozone resistance of the specimens were examined. Due to the post cure during the aging test, hardness of vulcanizates was increased. It was found that the undesirable characteristics of heat and ozone resistance of pure SBR was significantly improved through the blending of SBR with CR.