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와이블-역승법을 이용한 기계류부품의 가속시험 방법 개발
이근호(Geunho LEE),김형의(HyoungEui KIM),강보식(BoSik KANG) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
This study was performed to develop the accelerated life test method using Weibull-IPL(Invcrse Power Law) model for mechanical components. Weibull-IPL model is concerned with determining the assurance life with confidence level and the accelerated life test time. From the relation of weibull distribution factors and confidence limit. the testing times on the no number of failure acceptance criteria are determined. The mechanical components generally represent wear and fatigue characteristics as a failure mode. IPL based on the cumulative damage theory is applied effectively the mechanical components to reduce the testing time and to achieve the accelerating test conditions. As the actual application example. accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% confidence level for one test sample. According to IPL, because test time can be shorten in case increase test load. test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equiva1ent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7.
정규홍(Gyuhong Jung),김형의(Hyoungeui Kim),이근호(Geunho Lee) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
HMT is a type of continuously variable transmission which has split power path characteristics with gear train and hydro static unit. The benefit of improved fuel economy and high power capacity enables it to be a promising application for large vehicles. This paper presents the analysis results including velocity, static torque and dynamic model of the HMT that is developed for city buses. The speeds of gear shafts, the static clutch torque and split power ratio for each mode are detailed here. Also, the dynamic simulation result for mode shift characteristics shows that little shift shock is observed because of the synchronized rotation speed in clutch.
정규홍(Gyuhong Jung),김형의(Hyoungeui Kim),김종기(Jongki Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Efficiency analysis of the developing HMT was performed by the solution of simultaneous equations derived from the kinematic and static torque relations considering the efficiency of gear and hydraulic units. The analysis results show that the overall HMT efficiency largely depends on the amount of power delivered by HSU and it could be improved for the HMT designed with more number of shift modes.
차량도어 래치스프링의 형태모수 수정을 이용한 보증수명 추정
이근호(Geunho Lee),김형의(Hyoungeui Kim),김도식(Dosik Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This study was performed to develop the assurance life prediction method using modification of shape parameter for the latch spring of vehicle door. The shape parameter f3 is one of main parameter with scale parameter, number of sample, confidence level, to determine the predicted assurance life and testing time. The proposed the modification of shape parameter is an approach to verify the life prediction procedures based on the life testing data and to improve the reliability assessment on the statistical distribution. The latch spring generally represent fatigue and fracture characteristics as a failure mode. Firstly, life distribution of latch spring was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (B?) 300,000 cycles and 95 % confidence level for 60 test samples with value of shape parameter 2.07 from reference data. Secondly, after the life test until to acquire all sample failure, the value of shape parameter 2.26 can be obtained by analyzing the using MINITAB. Finally, the assurance life of latch spring could be predicted by the relation of mean life and the scale parameter which is achieved also from the analysis of sample failure data.
시내버스용 기계-유압식 무단변속기(CVT)의 설계기술 연구
이근호(Geunho Lee),김형의(Hyoungeui Kim),김도식(Dopsik Kim),정동수(Dongsu Jeong) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Hydro-mechanical type CVT(Continuous Variable Transmission) developed for heavy and high power propulsion vehicle changes the speed by regulating the swash plate on the hydraulic pump & motor as variator. Therefore it is possible to generate high torque at low speed and to obtain the high power density as characteristics of hydraulic variator. To reduce the disadvantages of hydraulic pump & motor like as low efficiency and noisy problem, some parts of power could transfer by gear train. In this study, the application vehicle of hydro-mechanical type CVT is the city bus showing frequent stops and requiring the safe and smooth drivability because of standing passengers. The advantages of hydro-mechanical type CVT for city bus are the reduction of harmful exhaust gas by control the diesel engine as a constant at optimal operating speed and the offer the safe and comfortable drivability without shifting impact. Thus. the purpose of this study is proposed the direction of concept design that is essentially necessary for development of transmission and optimal methodology about design parameters and factors.<br/>
[동력전달계부문] HSU의 유량손실을 고려한 정유압 기계식 변속기의 동력특성해석
성덕환(Dukhwan Sung),이근호(Geunho Lee),김형의(Hyoungeui Kim),김현수(Hyunsoo Kim) 한국자동차공학회 2001 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2001 No.11_2
An improved hydro-static unit(HSU) model is proposed by considering the flow loss in order to analyze the power flow characteristics of a hydro-mechanical transmission(HMT) and a network analysis algorithm is presented to determine the torque and speed of each element of the HMT. To calculate the torque and flow loss of a pump and a motor in HSU, an effort and flow concept is introduced, which can be used to establish a torque and speed matrix in the network analysis. It is found from the network analysis that magnitude of the HSU stroke increases to maintain the same output speed in order to compensate the flow loss in the HSU and the efficiency of the HMT shows the lowest value in the 1st speed since the HSU has the largest flow loss in the 1 st speed and the flow loss decreases as the speed ratio upshifts.