Gi-Chun Lee

System Design and Performance Test of Hydraulic Intensifier

. 얻을 수 있었다. Abstract: Components such as pressure vessel, hydraulic hose assembly, accumulator, hydraulic cylinder, hydraulic valve, pipe, etc., are tested under the impulse-pressure conditions prescribed in ISO and SAE standards. The impulse pressure test machine needs to have a high pressure, a precise control system and a long life. It should satisfy the requirements for fabrication of the impulse tester to generate ultra high pressure in the hydraulic system. In the impulse tester, a servo-valve control system is adopted; although the control application is convenient, it is expensive owing to the cost of developing the system. The type of the control system determines the pressure wave, which affects the components that are tested. In this study, the manufacturing process and the intensifier system design related to the flow, pressure, and the increasing rate of pressure are investigated. The results indicate the ultra high pressure waves in the system.

Life Prediction for High Pressure Hose of Power Steering System by Impulse Pressure Test

The hydraulic hose can be divided with the low pressure, the medium pressure, and the high pressure hose according to the applied pressure. The power steering system in a passenger car can be divided with the high pressure and the low pressure hose. This study deals with the life prediction for high pressure hose to be given impulse pressure which was generated in turning the car. To adjust with external and internal condition, impulse pressure and oil temperature need to be controlled with impulse test system. The result, which is only controlled with the pressure and oil temperature, adapted Calibrated Accelerated Life Test(CALT) method to predict the life of the high pressure hose and analyzed the swagging part by finite element method during the impulse test.

A Study of the Variation in Intensifier Performance Characteristics Varying with Pressure and Temperature

An ultra high- pressure system generally consists of a hydraulic power unit, an oil supply unit, an electrical power supply device, and an electrical control device. The hydraulic power unit supplies the hydraulic power to the intensifier to create generate ultra high pressure. The intensifier amplifies increases the pressure using the oil supplied from by the hydraulic power unit. The electrical supply devices and control devices maintain are provided for the electric motors, valves, and sensors. In this study, instead of a flow-control device, a pressure-control type device was mounted on a manifold block in the hydraulic power unit instead of the flow-control type. A servo valve was fitted in the intensifier, and the performance characteristics of the intensifier varied according to the variations of in the pressure cycle and with the temperature of the operating oil in the hydraulic power unit.

A Study on Fracture Characteristic of Ceramic Dome Using Shock Tube

Fracture characteristics for plate and dome shapes of glass filled ceramics using shock tube were carried out. Glass filled ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role as separated membrane between combustion and external air, and needs the frangible characteristics that the particles of fractured glass filled ceramics should not affect the internal components of combustion. The objectives of this study are to evaluate the fracture pressures for various thicknesses and diameters of shock impact area. Also fracture phenomena of separated membrane using a shock tube compare with analytical method. The experimental apparatus consists of a driver, a driven section and a dump tank. The used material is glass filled ceramic made from Corning company. Specimens have the thickness of 3, 4.5 and 6mm. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.

Development of the Accelerated Life Test Method & Life Test Equipment for the Counterweight of the Construction Machinery

A large-sized exciter that vibrates a two-ton component is required to simulate the field operating conditions of a counterweight of an excavator. However, it is difficult for a small-medium sized company to obtain a large exciter for the life test of a counterweight which is an equivalent counterbalancing weight that balances a load. Therefore, in this study, we developed life test equipment for evaluating the reliability of construction machinery weighing about two tons. It simulates the field operating conditions using rotational vibrators consisting of electric motors. A failure analysis of the counterweight was also performed for the major components. Field data acquired from various sites were applied to the life test design of the counterweight. Finally, a zero-failure qualification test based on the accelerated life test was designed, and there was no failure during the test, which guarantees a life of 10,000 hours.

Anti-obesity effects of Phyllostachys pubescens and Scutellaria baicalensis complex

Anti-obesity drugs that have been developed so far have limited efficacies and considerable adverse effects affecting tolerability and safety. Therefore, most anti-obesity durgs have been withdrawn. We tried to develop an anti-obesity agent by combinations from herbs that are used in food ingredients as well as in traditional medicines. In our study, the ethanolic extracts from Bamboo (Phyllostachys pubescens) leaf (BL) and Scutellaria baicalensis (SB) and their 1:1 combination (BLSB) was evaluated on high fat diet induced obese mice. BLSB group showed significant reductions in body weight gain and fat weights of liver and epididymal adipose tissue compared to BL or SB alone as well as control. Total-cholesterol and LDL-cholesterol levels significantly decreased, and HDL-cholesterol level increased. In liver tissue, macrovesicular steaotisis was remarkably improved and its fat cell size was also significantly decreased. We have further investigated the anti-obesity effects by various combinations of the BL and SB as follows: BS31, BS21, BS11, BS12, and BS13 were formulated by mixing B and S at a ratio of 3:1, 2:1, 1:1, 1:2, and 1:3. All of these combinations in obesity mice reduced body weight, lipid accumulation in liver and adipose tissue as well as adipocyte size, compared to the high fat diet control mice. Among these combinations, the 2:1 combination (BS21) showed a remarkably effect. These results suggest that the combination preparations of bamboo leaf and S. baicalensis, especially their 2:1 combination, have anti-obesity effects with synergistic effect compared to bamboo leaf or S. baicalesis.

Low Cycle Fatigue Behavior of Cobalt-Base Superalloy ECY768 at Elevated Temperature

Abstract : The Co-base super heat resisting alloy ECY768 is employed in gas turbine because of its high temperature strength and oxidation resistance. The prediction of fatigue life for superalloy is important for improving the efficiency. In this paper, low cycle fatigue tests are performed as variables of total strain range and temperature. The relations between strain energy density and number of cycle to failure are examined in order to predict the low cycle fatigue life of ECY768 super alloy. The lives predicted by strain energy methods are found to coincide with experimental data and results obtained from the Coffin-Manson method. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature. Key Words : low cycle fatigue, co-based superalloy, strain energy method, elevated temperature