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압력과 온도 복합가속모형을 적용한 유압호스 조립체 수명특성 연구
이기천(Gi Chun Lee),김형의(Hyoung Eui Kim),조유희(You Hee Cho),김재훈(Jae Hoon Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.11
유압호스는 건설기계, 자동차, 항공기 등 각종 기계의 유압장치에서 동력을 전달하기 위한 배관으로 사용된다. 산업의 전분야에서 에너지를 전달하기 위한 배관의 한 종류로서 진동이나 충격 등으로부터 시스템을 보호하는 역할을 한다. 여러 가지 외부 환경 조건으로부터 시스템을 유지하기 위해서는 호스 조립체에서 온도와 압력 등의 외부 환경 조건에 대한 내성을 가지고 있어야만 한다. 본 연구에서는 기존에 호스 조립체에 대해 온도 또는 압력 중 한 가지 인자를 고려한 가속모형을 제시한 연구는 있었지만 두 가지 인자를 동시에 고려한 가속모형은 제시하지는 못하였으므로, 호스 조립체의 압력과 온도를 모두 고려한 복합가속 모형식을 제안하는 것을 목적으로 한다. Hydraulic hoses are used as pipelines for transferring power from hydraulic systems in various machineries such as construction equipments, automobiles, and aircraft. Hydraulic hoses protect the system from vibration or impacts, and they are being used to transfer energy in all segments of the industry. In order to protect the system from various external environmental conditions, hydraulic hose assemblies must be able to withstand a wide range of temperatures and pressures, as well as variations in other factors. In previous studies, an acceleration model for the hydraulic hose assembly was developed by taking into account only one of the acceleration factors (temperature or pressure). Therefore, the objective of this study is to develop a comprehensive acceleration model that takes both temperature and pressure into consideration.
이기천(Gi-Chun Lee),이용범(Young-Bum Lee),최병오(Byung Oh Choi) 한국신뢰성학회 2015 신뢰성응용연구 Vol.15 No.3
Track drive unit adopted in the small sized excavator generally have been used in the construction equipment under the 10 tons as the driving device with forwarding and reversing of excavator. It is required to study the accelerated life test applied by over torque and speed to test the durability life test reflected the many driving modes of small sized excavator and also need to equip the comprehensive performance and life test equipments to do the various performance tests. This study had analyzed the failure modes of the components, and calculated the equivalent loads investigated the used loads in the real field conditions and elicits the acceleration factor adopted in the inverse power model. Also, this study have considered the changes of the acceleration factor and the durability test time in the case of the rotary group and the bearing through analyzing the main failure modes. It was calculated the no failure test time about 2 samples and confidence level 90% and elicited the accelerated life time 720 hours.
이기천(Gi-Chun Lee),이용범(Yong-Bum Lee),남태연(Tae-Yeon Nam),양청광(Cheong-Gwang Yang),김성현(Sung-Hyun Kim),송은택(Eun-Taek Song),김상덕(Sang-Duck Kim),김재훈(Jae-Hoon Kim) 한국신뢰성학회 2021 신뢰성응용연구 Vol.21 No.4
Purpose: The screws used in agricultural machinery are worn by friction due to relative motion during prolonged high-pressure use. The wear can be categorized as abrasion and cohesion wear, which shorten the performance and life of agricultural machinery and eventually lead to failure. This study focused on determining the wear rate of the screw surface in dehydration machinery. Methods: We sought to select the optimal material by comparing and analyzing the wear characteristics of three types of materials: STS, SCM, and SNCM. The wear test was performed under variable load, dry, and wet conditions on a total of 3 samples using a pin-on-disk wear tester. The friction coefficient, amount of wear, and specific wear rate were obtained from the test results and compared for the three materials. Results: The friction surface was imaged using SEM. It was found that the specific wear rate of STS was the highest under all load conditions in both dry and wet environments. The specific abrasion rate of SCM was similar to that of SNCM in a dry environment but the lowest in a wet environment, revealing its excellent abrasion resistance. Conclusion: A material with high wear resistance was identified by analyzing the wear characteristics of three types of materials. Moreover, its use increased durability of the screw, a critical component in dewatering machines.
건설기계용 카운터웨이트 시험장비 및 가속수명시험법 개발
이기천(Gi-Chun Lee),이용범(Young-Bum Lee),최병오(Byung-Oh Choi),김도식(Do-Sik Kim),최종식(Jong-Sik Choi) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5
The counter weight is a heavy material installed in equipment to balance the center of gravity of construction machinery or special equipment. When the connection part of the counter weight, which is connected to the construction machinery such as the excavator or a fork lift, is broken to be separated, it can be very risky due to the loss of the center of gravity and its overturn. So, it is necessary to secure its reliability. However, to perform the life testing of the counter weight, it is required to have very large-sized exciter which simulates the vibration to the about 2-tons heavy material similar to that occurring in the real field. Firstly, the stress of the broken part of the counter weight is analyzed by failure analysis performed for the major components in this paper. Secondly, the field data acquired in the site was applied to the life test of the counter weight. Also, we developed the life test equipment, which is simulated real service condition with a rotational vibrator using the electric motor, to evaluate the reliability of the construction machineries even though the weight of the sample was heavy weight about 2 tons.
충격 압력을 받는 파워스티어링 시스템의 고압호스 수명 예측
이기천(Gi Chun Lee),김형의(Hyoung Eui Kim),박종원(Jong Won Park),이종황(Jong Hwang Lee),정원욱(Won Wook Jeong),임영한(Young Han Lim),황권태(Kwon Tae Hwang),이영신(Young-Shin Lee),김재훈(Jae Hoon Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.1
유압호스는 적용되는 압력에 따라서 저압, 중압, 고압으로 구분되어진다. 승용차의 파워스티어링 시스템은 저압부와 고압부 시스템으로 구분되어질 수 있다. 본 연구의 목적은 차량이 회전할 때 발생되는 충격압력이 고압호스부에 적용될 때 수명을 예측하는 것이다. 내부와 외부 조건을 조절하기 위해서 충격 압력과 작동유의 온도는 충격압력 시스템에서 제어되는 것이 필요하다. 충격압력 시험에서 압력과 작동유 온도만을 조절하여 얻은 결과는 고압호스의 수명을 예측하기 위한 조절형 가속수명시험을 적용하였으며, 또한 유한요소법으로 스웨이징부를 해석하였다. 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.