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유봉준,박계순,임규찬,박종진 한국운동역학회 1999 한국운동역학회지 Vol.9 No.1
The study aimed to analyse and compare the various kinematic variables of Croise´ motion with A la seconde motion in order to provide improve-ment of understanding in the technique of ballet. And Fouett´ motion was divided into LSI(i.e., Leg-Stretching motion: A la seconde in French), LBI(i.e., Leg-Banding motion: Coupe´ in French), LS2 and LB2. To achieve of such the purpose, six ballerina were sampled as subjects with 5-year career at university and the motions were required to be performed as quickly and stably as possible. The motions were analysed using the DLT method of three-dimensional cinematography. The principal kinematic variables for comparative analysis between Croise´ and A la seconde were as such: spent time, c.o.g distance, angular velocity of both arms, lean angle, hip joint angle and height of c.o.g. As a result of analyzing the data, the following conclusions were drawn. 1. The overall duration of Croise´ is less than that of A la seconde, but there was no significant difference two motions. 2. C.O.G. distance in Croise´ in view of horizontal plane tend to be shorter than that in A la seconde, but there was no significant difference between two motions. 3. The angular velocity of right arm in Croise´ is larger than that in A la seconde only at LS. There was no significant difference in the angular velocity of left arm in two motions, but the angular velocity f left arm in A la seconde tend to be larger than that in Croise´both at LSI and at LS2. and the angular velocity of left arm un Croise´ tend to be larger than that in A la seconde both at LB1 at LB2. 4. There was no significant difference in the lean angle and right hip joint angle between two motions. But the lean angle of Croise´ tend to be larger than that of A la seconde and the right hip joint angle of Croise´ tend to be larger than that of A la seconde. The right knee joint angle of Croise´ was larger than that of A la seconde at LS1 which proved to be significant difference between two motions. At other factors, there was no significant difference, but the right knee joint angle of A la seconde tend to be larger than that of Croise´. 5. There was significant difference between two motion at all factors on the height of c.o.g.. The height of c.o.g. of Croise´ tend to be higher than that of A la seconde at LS1 and at LS2. Besides, the height of c.o.g. of A la seconde tend to be higher than that of Croise´ at LB1 and at LB2.
김정호,조성욱,유봉준 중앙대학교 생산공학연구소 1999 생산공학연구소 논문집 Vol.8 No.1
대형구조물의 용접시 잔류변형과 잔류응력은 구 구조물의 모양과 크기, 그리고 구속조건에 따라 크게 달라진다. 따라서, 대형구조물의 잔류응력에 대한 정확한 해석을 위해 용접 잔류응력 및 용접 잔류변형을 정확히 예측할 수 있는 적절한 유한요소해석 절차의구현이 필요하다. 본 연구에서는 용접 잔류응력과 변형률의 존재를 예측할 수 있는 열전달 해석 및 열탄소성 해석과 같은 적절한 유한요소해석 과정을 찾고자 한다. 해석을 위해 아크의 열원에 대한 가우시안 분포를 가정하고 용접부의 상변화에 대한 엔탈피모델을 선정한다. 그리고, 대형구조물의 열전달해석을 위해 Remeshing기법을 이용한 유한요소모델의 생성이 필요하다. 끝으로, 개발된 해석과정은 단순맞대기 용접에 대해 적용해 보았고, Remeshing 기법은 컴퓨터 자원에 대한 절약 측면에서 상당한 효과를 나타내었다. Welded structures experience changes in shape, size and constraint conditions after favirication due to internal residual stresses. For the accurate simulation of the typical welding procedure, transient heat transfer analysis as well as thermal-elasti-plastec analysis should be employed. In this paper, appropriate finite element analysis procedures that can predict welding residual stresses and strains are presented. Gaussian distribution of arc heat source is assumed andenthalpy model is employed for phase change of the welding zone. Finally for the purpose of applying the developed technique to large scale structrues, remeshing techniques by successive generation of finite element model are given for that transfer analysis. The developed analysis procedure are tested for the simple butt welding which gives reliable results. Remeshing techniques are also tested against the existing mesh pattern which showed considerable reduction in computational resources.
Alloy Wheel용 저압 주조 A356-T6 합금의 기계적 특성
유봉준 ( Bong Jun Yoo ),김정호 ( Jeong Ho Kim ),윤형석 ( Hyung Seok Yoon ),어순철 ( Soon Chul Ur ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.1
The mechanical properties of low-pressure die cast (LPDC) A356-T6 automotive road wheels are evaluated and correlated with their corresponding microstructures. In this study, two types of alloy wheels processed using different LPDC gating system are investigated. The yield stress, tensile stress, and elongation values tested at room temperature are correlated with the secondary den-drite arm spacing (SDAS) with respect to the gating system, and are also compared with similar studies. The SDAS and precipitatesare examined using optical microscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy. The phase infor-mation is also investigated using X-ray diffraction. Charpy impact tests are also performed from-100℃ to 200℃, and the fracture surfaces are examined using SEM. The impact energy is demonstrated to increase with increasing temperatures without exhibiting specific transition behaviors as in other nonferrous alloys. The fracture toughness is also evaluated using three point bend test with single-edged bend specimens. The obtained fracture toughness values are in good agreement with those in similar studies.
유봉준(Bongjun Yoo),배현우(Hyunwoo Bai) 한국자동차공학회 2015 한국자동차공학회 학술대회 및 전시회 Vol.2015 No.11
Under free vibration, the system oscillates at its natural frequencies which are dynamic characteristics of the structure specified by its stiffness and inertia properties. Modal analysis provides useful insight into the dynamic behavior of a structure. The vehicles are composed of many components which has their own natural frequencies. In case that the vehicle global mode is very close to a component’s mode in frequency, these 2 modes would be coupled and could cause a problem of noise and vibration. Especially when the component has considerable mass comparing to the total mass, the component mode can shift the vehicle global mode up or down. For this reason, we need to identify the vehicle global mode and the component modes and track their changes in the system. In this study, the component mode identification procedure is introduced. The battery system in the electric vehicle can be an example for this subject since the battery system is a large component which can influence the significant mode in the entire structure. This study shows the battery system’s mode which is identified and decoupled from the vehicle global mode to improve its performance.