• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1893-1895
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• 2005

To measure electrical properties of semiconducting materials in power cable, we have investigated dielectric properties of EVA showed by changing the content of carbon black. The specimen was primarily kneaded in material samples of pellet form for 5 minutes on rollers ringing between $70[^{\circ}C]$ and $100[^{\circ}C]$. Then that was produced as sheets after pressing for 20 minutes at $180[^{\circ}C]$ with a pressure of 200[kg/cm]. The contents of conductive carbon black were 20, 30 and 40(wt%), respectively The dielectric properties of specimens were measured by dielectric thermal analyzer (CONCEPT 40, NOVOCONTROL). Measuring frequencies were 10, 60, 100, 1000, 10000, 100000, 1000000(Hz) and measuring temperatures were -40, -20, 20, $90[^{\circ}C]$. From above experimental result, permittivity was increased, while $tan{\delta}$ was decreased according to an increment of the content of carbon black.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.04a
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• pp.35-35
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• 1997

High$\cdot$speed steels (HSS) with a combination of good wear resistance and toughness are finding new, non-cutting applications such as rolls and rollers. In this paper, the research interests are focused on the microstructural evolution of a SMo-6W series high speed steel during HIPping and the effect of HIPping process parameters on its microstructure and properties. HIPping process variables includes; temperature, pressure and hold time. The microstructures of the HIPped HSS were examined by SEM, OM and X-ray diffraction whereas the properties measured were the relative density, hardness, and bend strength at room temperature. In HIPped materials, MC and M6C were the major carbides formed in a matrix of martensite. The effect of powder size on the microstructure and mechanical properties of HIPped materials was insignificant. However, HIPping temperature and hold time strongly affected the carbide size and distribution. The results show that at proper HIPping temperature and pressure conditions, the final products approach the full density ( > 99% RD). The particle boundaries were completely eliminated without an eminent microstructural coarsening. The bend strength was about 2.3 Gpa, which is superior to cast HSS. At excessive HIPping temperatures, rapid carbide coarsening occurred, thus deteriorating the mechanical properties of the P/M steels.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.236-237
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• 2005

To measure surface roughness and smoothness of semiconducting materials in power cable, we have investigated the formation and growth process of carbon black showed by changing the content of carbon black. The specimens were primarily kneaded in material samples of pellet form for 5 minutes on rollers ranging between 70[$^{\circ}C$] and 100[$^{\circ}C$]. Then they were produced as sheets after pressing for 20 minutes at 180[$^{\circ}C$] with a pressure of 200[kg/cm]. The contents of conductive carbon black were the variable, and their contents were 20, 30 and 40[wt%], respectively. The surface roughness and smoothness of specimens were measured by SEM and AFM. From SEM experimental result, carbon black in specimens formed matrix as a particles. Also we showed growth process of carbon black according to an increment of the content of carbon black. From AFM experimental result, surface roughness of specimens decreased according to an increment of the content of carbon black.

• Journal of Institute of Convergence Technology
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• v.6 no.1
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• pp.23-26
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• 2016

DC motor shafts have several defects such as double cut, deep scratch on surface, and defects in diameter and length. The deep scratches are due to collision among the other shafts. So the scratches are long and thin but their orientations are random. If the smallest enclosing box, i.e. oriented bounding box for a detective point group is found, then the size of the corresponding defect can be modeled as its diagonal length. This paper proposes an suface inspection algorithm for the DC motor shaft using the oriented bounding box. To evaluate the proposed algorithm, a test bed is made with a line scan CCD camera (4096 pixels/line) and two rollers mechanism to rotate the shaft. The experimental result on a pre-processed image with contrast streching algorithm, shows that the proposed algorithm sucessfully finds 150 surface defects and its computation time (0.291 msec) is enough fast for the requirement (4 seconds).

• International Journal of Naval Architecture and Ocean Engineering
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• v.3 no.3
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• pp.216-224
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• 2011

In This study develops a quasi-three dimensional numerical model of wave driven coastal currents with accounting the effects of the wave-current interaction and the surface rollers. In the wave model, the current effects on wave breaking and energy dissipation are taken into account as well as the wave diffraction effect. The surface roller associated with wave breaking was modeled based on a modification of the equations by Dally and Brown (1995) and Larson and Kraus (2002). Furthermore, the quasi-three dimensional model, which based on Navier-Stokes equations, was modified in association with the surface roller effect, and solved using frictional step method. The model was validated by data sets obtained during experiments on the Large Scale Sediment Transport Facility (LSTF) basin and the Hazaki Oceanographical Research Station (HORS). Then, a model test against detached breakwater was carried out to investigate the performance of the model around coastal structures. Finally, the model was applied to Akasaki port to verify the hydrodynamics around coastal structures. Good agreements between computations and measurements were obtained with regard to the cross-shore variation in waves and currents in nearshore and surf zone.

• Transactions of Materials Processing
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• v.31 no.6
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• pp.384-393
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• 2022

The flow forming process consists of a split process, a divide process, and a forming process. The split process is a forming process in which rollers radially permeate a simple disc-shaped forging material and split it in both directions to form a top-bottom bidirectional cup. It is advantageous for post-processing to deepen the forming depth in the split process but this characteristic causes the failure near the edge of the mandrel during the actual process. The split process was analyzed using Rigid Plastic FEM, and the stress analysis of the mandrel was conducted to find the cause of the failure. It was found that the failure occurred due to fatigue accumulation damage caused by repeated residual stress.

• Design & Manufacturing
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• v.15 no.4
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• pp.8-13
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• 2021

A plastic roller for opening and closing the safety door of the injection molding machine was molded. The dimensional change of the measurement position of the roller was studied when the cooling time was applied differently among the molding conditions, and when the temperature of the coolant applied for mold cooling was also applied differently. Cooling times of 300 seconds and 400 seconds, hot and low-temperature coolant were applied. When the low-temperature coolant was applied, the measuring point of the roller shrank by 0.03 mm. However, when the high-temperature coolant was applied, the measuring point shrank by 0.3 mm. It was found that the application of low-temperature coolant among coolants was more suitable for the reference dimension of the molded article compared to the application of high-temperature coolant. Among the cooling water applied for the molding of plastic rollers, when high-temperature coolant is applied, the shrinkage rate measured immediately after ejection was smaller than when low-temperature coolant is applied. However, it was found that post shrinkage, which occurs over time, occurs much larger when high-temperature coolant is applied.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.28-33
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• 2022

The heating roller of an actual pulse output device (POD) production facility is composed of a steel roller and a rubber roller. The time to reach a specific temperature and the temperature distribution on the roller surface were analyzed and compared according to the change in the number of cartridge heaters inside the heating roller. In this analysis, a steady-state thermal analysis of a steel roller was performed for the cases of a 5-cartridge heater and 9-cartridge heater. Finite element analysis was applied with reference to the surface temperature data of the heating roller during operation and the calorific value of the cartridge heater. Using the 9-cartridge heater, faster target temperature achievement and more uniform temperature distribution were confirmed than for the 5-cartridge heater.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.162-169
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• 2000

This study was carried out to develop a continuously variable-speed transmission(CVT) for agricultural tractor. A full-toroidal CVT mechanism with four discs and six rollers was selected as a device for changing speed ratio continuously. In the step of system layout design, the sizes of roller cylinders and end-load cylinder, which were critical factors for controlling the variator, were designed. Also the control pressure range was designed to limit the contact pressure of variator. In order to make the maximum speed of vehicle as 30km/h, the planetary gear and the six pairs of gears were designed. Also the hydraulic clutch, silent chain, hydraulic manifold and electronic controller were designed. After the design, a prototype with CVT controller was developed and tested. The speed of vehicle was changed continuously to the speed set by driver and the settling time was about 0.52 second at the step-response test (reduction ratio of variator 2.0 to 1.0), which was acceptable as a response time for working with tractor.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.74-84
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• 2023

This paper is the result of a comparative analysis of crew members' workloads using the EMG and OWAS methods according to the fishing process before and after the improvement of the operating system of the experimental vessel, with the aim of improving operational efficiency and safety work of coastal improved stow net fishing vessels. The target crew members were three people with at least five years of experience on board the same fishing vessel as the experimental vessel. After improving the operating system, such as installing a power block crane and two capstans, change the location of the ball-roller, the time required for setting and hauling work decreased (p < .01), and the evaluation results by OWAS showed that the overall workload for setting and hauling net work decreased. The results of muscle activity analysis showed a decrease in lashing anchor work (p < .01) in the case of hauling net and in anchor dropping work in the case of setting net (p < .001). It is judged that the use of ball rollers in net handling has been reduced; consequently, work safety has been improved.