• Journal of Ocean Engineering and Technology
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• 제13권1호통권31호
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• pp.29-38
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• 1999

In this paper the forming simulation of circular bulge by using PAM-STAMP has been performed to estimate the sheet metal forning and the plastic deformation characteristic of circular bulge. The uniaxial tension tests adn bulge tests are carried out for studying the forming characteristics of materials, and also Moire experiment are carried out for measuring the radius of curvature of the bulge and the polar compressive thickness strain. In order to compare the simulation results with the experiment and Hills theory, the relationships between redius of curvature adn polar height of the bulge, between hydraulic pressure and polar height, and between polar compressive thickness strain and polar height, are used. According to this study, the results of simulation and Hills theory are good agreement to the experiment. So, the results of simulation by using PAM-STAMP and Hills theory will give engineers good information to assess the formagbility and plastic deformation characteristic of hydraulic circular bulge test.

• Journal of Biosystems Engineering
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• 제40권2호
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• pp.95-101
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• 2015

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

• Journal of Drive and Control
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• 제13권2호
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• pp.26-33
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• 2016

This paper describes of a mathematical and real experimental analysis for a walking robot which uses servo valve driven hydraulic actuator. Recently, many researchers are developing a walking robot based on hydraulic systems for the difficult and dangerous missions such as walking in the rough terrain and carrying a heavy load. In order to design and control a walking robot, the characteristics of the hydraulic actuators in the joint through the view point of walking such as controllability and backdrivability must be analyzed. A general mathematical model was used for analysis and proceeds to position and pressure changes characteristic of the input and backdrivability experiment. The result shows the actuator is a velocity source, had a high impedance, the output stiffness is high in contact with the rigid external force. So stand above the controller and instruments that complement the design characteristics can be seen the need to apply a hydraulic actuator in walking robot.

• Journal of Korea Water Resources Association
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• 제38권8호
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• pp.675-689
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• 2005

In this paper, it was analyzed the variation of hydraulic characteristics through changing discharge at main channel and lateral channel and state of hydraulic structure at the natural channel junction by experiment. The experimental area is chosen at the channel junction of Nam-Han river and Pyeongchang river. The scale of the experiment is 1/200 in horizontal, and 1/66.7 in vortical, so the distoration rate is 3. From the experiment, the reduction effect of the water level is $12\%$ in the case of removing intank dam, and $5\%$ at the hydro-electronic dam removing case. Furthermore, in the case of two hydraulic structures removing, the reduction effect of water level is $18\%$ at the channel junction. Also, the stagnation zone, which is cased diminution of the channel at the junction, is decreasing through removing the structures.

• The Journal of the Korea Contents Association
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• 제13권5호
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• pp.485-492
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• 2013

The point sand bars of Hahoi Village on Nakdong River have undergone considerable changes including fluvial and vegetation characteristics due to flood regulation by the dams constructed upstream. In this study, the numerical fluvial/sediment and water quality model, KU-RLMS, is applied to the aquatic area near Hahoi Village (middle/upper region of the Nakdong River) for clarifying the mechanisms of changes in hydraulic and aquatic characteristics. The fixed-bed hydraulic experiment was carried out for horizontal two-dimensional numerical model. The numerical simulation reveals that flow is accelerated near the left bank of Booyongdae downstream of the Hahoi Village area. Circulatory flow pattern was observed at the right bank downstream of Hahoi Village. The simulation was in good agreement with the hydraulic/physical experiment. For the discharge of design flood, at the area of circulatory flow pattern, the superelevation of about 1.0 m at the right bank was predicted compared to the left bank of high flow velocity, which is also in good agreement with hydraulic experiment.

• The Journal of Engineering Geology
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• 제13권3호
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• pp.281-292
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• 2003

We setup a continuous measurement system for electrical conductivity of fluid in a model borehole and verified the basic environments in electrical conductivity measurement for estimating hydraulic constants. The experiment was made by monitoring the conductivity change within the hole using NaCI solution of different salinities and incoming formation fluid using distilled water. The experiment was made under the state of constant flow rate by maintaining balance between inflow and outflow. Conductivity variation features were observed by controlling salinity contrasts and temperature differences between fluid within the hole and incoming formation fluid. flow rate and the location of inlet and outlet. The results of the experiment show well the role of each affecting factor on the conductivity distribution. and suggest appropriate environments for conductivity measurements. It is considered that the basis of the conductivity measurement for henceforward laboratory model and/or in-situ borehole experiment has been prepared.

• Transactions of The Korea Fluid Power Systems Society
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• 제4권3호
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• pp.7-12
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• 2007

This paper presents an energy saving hydrostatic pressure exchanger for sea water desalination equipment. In a reverse osmosis(RO) system for desalinating sea water, more than 70 percent of the supplied sea water, brines which were impassable through RO membrane are bypassed, resulting in high energy losses. In this paper, a hydrostatic pressure exchanger consisting of an embedded water hydraulic piston motor and a water hydraulic piston pump was proposed and investigated in order to recover the energy of the bypassed brines. The pressurized brines are supplied to the embedded water hydraulic piston motor as power sources and the water hydraulic piston pump is driven by the output torque of the embedded water hydraulic piston motor as well as electric motor. Consequently, the energy of the bypassed brines can be recovered. To examine the electric energy saving characteristics of the hydrostatic pressure exchanger, a simulation model was constructed using commercial software and experiments were conducted. Through the results of simulation and experiment, the feasibility of the electric energy saving effect of the proposed hydrostatic pressure exchanger was investigated.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제18권7호
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• pp.14-21
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• 2019

Large-diameter hydraulic devices such as the hydraulic reservoir in aircraft that serves to balance the hydraulic pressure in the various hydraulic devices in the cabin and to store hydraulic oil are operated by the internal piston systems. However, since this operates in an environment with high temperature and humidity, it may cause the inner surface to flake during its operation. Therefore, an anodizing surface treatment is applied to improve the corrosion resistance, abrasion resistance, and smooth operation. However, anodizing increases the surface roughness. Accordingly, the polishing process that improves the surface roughness after anodizing is important. However, the existing polishing process is performed manually, which results in an inefficient process. Therefore, in this study, we selected the optimum polishing conditions for effective polishing using the experimental design to improve the polishing process for the $Al_2O_3$ film that forms after anodization. Through experiments, we confirmed that the surface uniformity after polishing was superior as the feed rate was slower when the same polishing time had been applied.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1157-1161
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• 2003

A novel actuator with built-in the displacement and the thrust control function is presented in this paper. This actuator is a kind of compact hydraulic cylinder system which consists of a hydraulic cylinder, a spool, a sleeve, a mechanical feedback mechanism and a stepping motor. The displacement and thrust is in proportion to the rotational angle of stepping motor by the mechanical feedback. In order to investigate characteristics of this actuator, simulation study and preliminary experiments are conducted. Through the preliminary experiment this actuator is very effective in the control for displacement and thrust. Also, it became obvious that the stability of system can be adjusted by using the restrictor with the effect of velocity feedback. Furthermore, this paper explained that a flexible compliance control could be realized by adjusting the feedback weighting in the actuator.

• Journal of Biosystems Engineering
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• 제24권5호
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• pp.383-390
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• 1999

When a tractor travels slope lands, problems of operator safety and the reduction of job efficiency usually occur. Therefore, maintaining the tractor body being horizontal is critical to improve the security of traveling and the job performance. An experiment was made in a soil bin using the experimental model system built and equipped with a leveling control system. Adaptability of the control system was tested and investigated by analyzing system response in time and frequency domains. Control response time of hydraulic cylinder with 10lpm flow rate on a step input of 10$^{\circ}$slope was about 0.42sec. And it showed a linearly increasing trend without any hunching state. A steady state error of 0.6$^{\circ}$occurred but it was negligible. The hydraulic control system showed a little phase differences within the range of 0.4Hz input frequency. The experimental model showed that implementation of the proposed tractor control system to on slope lands tractor was feasible.