기계적 합금화한 Al-Ti 시료에서 미소상 피이크의 소멸현상과 ${Al_3}Ti$ 형성에 관한 연구

김진곤,김혜성,김병희,Kim, Jin-Gon,Kim, Hye-Seong,Kim, Byeong-Hui 한국재료학회 2001 한국재료학회지 Vol.11 No.12

The refining process and solubility of Ti in Al matrix during mechanical alloying (MA) were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM) as functions of alloy composition, milling time and ball to powder ratio (BPR). Mechanical alloyed samples were annealed for investigating their stability and the formation behavior of$Al_3Ti$in the temperature range from$200{\circ}C$to$600{\circ}C$. It is observed from present experimental that disappearance of Ti peaks in mechanically alloyed Al-10wt%Ti is not simply attributable to the dissolution of Ti into Al, but associated mainly with extreme refining and/or heavy straining of Ti particles The annealing of the mechanically alloyed Al-Ti powders show differences in aluminide formation behavior when Ti content in Al is equal to or less than l0wt% and higher than l5wt%Ti. When Ti-content in Al is equal to or less than l0wt%, the MA powders transform directly to a global equilibrium state forming $DO_{22}- type\;Al_3$Ti above$400{\circ}C$. In the Al-Ti samples with equal to or higher than l5wt%Ti, transitional phases of cubic$Al_3Ti$and tetragonal $Al_{24}Ti_8$ are formed above$400{\circ}C$. They are stable only below$500{\circ}C$, and, $DO_{22}-type\;Al_3Ti$ becomes dominant aluminide at temperature higher than$ 600{\circ}C$.

곡선보의 자유진동해석을 위한 고차 혼합요소

김진곤,박용국,Kim Jin-Gon,Park Yong-Kuk 한국전산구조공학회 2006 한국전산구조공학회논문집 Vol.19 No.2

In this study, we propose a new efficient 2-noded hybrid-mixed element for curved beam vibrationshaving a uniform and non-uniform cross section. The present element considering transverse shear strain is based on Hellinger-Reissner variational principle and introduces additional nodeless degrees for displacement field interpolation in order to enhance the numerical performance. The stress parameters are eliminated by the stationary condition and then the nodeless degrees are condensed out by the Guyan reduction. In the performance evaluation process of the present field-consistent higher-order element, we carefully examine the effects of field consistency and the role of higher-order interpolation functions on the hybrid-mixed formulation. Several benchmark tests confirm e superior behavior of the present hybrid-mixed element for curved beam vibrations. 본 연구에서는 균일단면 뿐만 아니라 불균일 단면을 갖는 곡선보의 동적해석을 효과적으로 수행할 수 있는 새로운 2절점 곡선보 요소를 제안하였다. 전단변형률을 고려한 본 요소는 Hellinger-Reissner 변분이론에 바탕하여 유한요소정식화를 수행하였다. 또한, 변위장에 대해 무절점 자유도를 추가적으로 도입하여 요소의 수치적 성능을 크게 향상시켰다. 계산의 효율성을 위해, 요소정식화의 최종단계에서 정치조건으로부터 응력매개변수들을 제거하고, 동적축약을 통하여 무절점 자유도 성분들 또한 최종적인 유한요소방정식에서 제거되어 일반적인 변위기저 요소와 같은 자유도를 가지는 유한요소방정식을 얻을 수 있다. 몇 가지 수치예제들에 대한 해석을 통하여, 무절점 자유도와 변위장에 일치하는 적절한 응력매개변수가 혼합요소의 수치적 거동에 미치는 영향을 분석하였으며, 본 연구에서 제안된 2절점 혼합요소가 곡선보의 동적해석에서 매우 정확하고 효율적임을 확인할 수 있었다.

휴대용 단말기의 낙하충격해석 및 실험적 검증

김진곤,이준영,이신영,Kim, Jin-Gon,Lee, Jun-Yeong,Lee, Sin-Yeong 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.4

In this paper, the drop/impact simulation for a mobile phone has been carried out with the explicit code LS-DYNA and its validation has been experimentally verified. The small size of this kind of electronics products makes it time-consuming, and difficult to conduct drop tests to detect the failure mechanism and identify their drop behaviors. Strict drop/impact performance criteria of such hand held electronic products as mobile phones play an important role in their design because these products must withstand both normal and unexpected shock. Usually, the product durability on drop impact depends on designers experience. The present reliable methodology of drop/impact simulation provides an efficient and powerful vehicle to improve the design quality and reduce the design period.

두 절점 혼합 곡선 보요소의 보간함수 선정

김진곤,Kim, Jin-Gon 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.12

In this paper, we propose a new efficient hybrid-mixed C(sup)0 curved beam element with the optimal interpolation functions determined from numerical tests, which gives very accurate locking-free two-node curved beam element. In the element level, the stress parameters are eliminated from the stationary condition and the nodeless degrees of freedom are also removed by static condensation so that a standard six-by-six stiffness matrix is finally obtained. The numeri cal benchmark problems show that the element with cubic displacement functions and quadratic stress functions is the most efficient.

화재 모델에 관한 연구

김진곤,Kim, Jin-Gon 한국화재보험협회 1988 방재기술 Vol.4 No.-

자동차 배출가스 후처리 장치 특허동향(III)

김진곤,최성배,Kim Jin-Gon,Choi Sungbae 한국자동차공학회 2005 오토저널 Vol.27 No.3

볼트결합부가 있는 구조물의 유한요소 모델링 및 실험적 검증

김진곤,박성수,최석환,Kim, Jin-Gon,Park, Seong-Su,Choe, Seok-Hwan 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.6

A reliable and practical finite element modeling technique to estimate the behavior of complex structures with bolted joints is important for engineeres in the industry. Accordingly, we have examined several simplified modeling techinques which do not require the use of special elements such as a gap eloement. The dynamic and static erxperiments have confirmed that the technique to model the bolted joints with eight-noded three dimensional elemnts which fill the bolt space gdives most satisfactory results.

효율적인 C⁰ 적층 곡선보 요소의 개발

김진곤,강상욱,Kim, Jin-Gon,Kang, Sang-Wook 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.4

In this study, we present a new highly accurate two-dimensional curved composite beam element. The present element, which is based on the Hellinger-Reissner variational principle and classical lamination theory, employs consistent stress parameters corresponding to cubic displacement polynomials with additional nodeless degrees to resolve the numerical difficulties due to the spurious constraints. The stress parameters are eliminated and the nodeless degrees are condensed out to obtain the (9x9) element stiffness matrix. It should be noted that the stacking sequences without transverse deformation to the load plane makes a two dimensional analysis of curved composite beams practically useful . Several numerical examples confirm the superior locking-free behavior of the present higher-order laminated curved beam element.

완화된 평형조건을 만족하는 응력함수를 가지는 3절점 혼합 곡선보요소

김진곤,Kim, Jin-Gon 한국전산구조공학회 2008 한국전산구조공학회논문집 Vol.21 No.2

본 연구에서는 완화된 평형조건을 만족하는 응력함수를 가지는 새로운 3절점 혼합요소를 제안하였다. 전단변형률을 고려한 본 요소는 Hellinger-Reissner 변분이론에 바탕하여 유한요소정식화를 수행하였다. 응력함수는 강체변형모드를 제거하고, 장일치(field consistency) 개념을 이용하여 곡선보의 극한거동에서 가성구속조건들을 억제할 수 있도록 선정하였다. 또한, 3절점 곡선보의 혼합정식화에서 강체변형모드를 제거하면서 동시에 평형방정식을 완전하게 만족하는 응력함수와 응력매개변수를 선정하는 것은 매우 어렵기 때문에 완화된 평형조건을 만족할 수 있는 응력함수를 도입하였다. 해석결과를 통하여, 제안된 3절점 혼합 곡선보요소가 곡선보의 해석에서 세장비와 곡률에 상관없이 매우 빠른 수렴성과 안정적인 거동을 나타냄을 확인할 수 있었으며, 응력분포 계산에 있어서도 기존 혼합요소보다 뛰어난 성능을 보여주었다. In this study, we propose a new three-node hybrid-mixed curved beam element with the relaxed-equiribrium stress functions for static analysis. The proposed element considering shear deformation is based on the Hellinger-Reissner variational principle. The stress functions are carefully chosen from three important considerations: (i) all the kinematic deformation modes must be suppressed, and (ii) the spurious constraints must be removed in the limiting behaviors via the field-consistency, and (iii) the relaxed equilibrium conditions could be incorporated because it might be impossible to select the stress functions and parameters to fully satisfy both the equiribrium conditions and the suppression of kinematic deformation modes in the three-node curved beam hybrid-mixed formulation. Numerical examples confirm the superior and stable behavior of the proposed element regardless of slenderness ratio and curvature. Besides, the proposed element shows the outstanding performance in predicting the stress resultant distributions.

mXm 분할표에서의 합치도 H

김진곤,박미희,박용규,Kim, Jin-Gon,Park, Mi-Hee,Park, Yong-Gyu 한국통계학회 2009 Communications for statistical applications and me Vol.16 No.5

평정자간 일치 정도를 나타내는 측도로 주로 사용되는 k의 문제점을 해결하기 위해 박미희와 박용규(2007)는 $2{\times}2$ 분할표에서 새로운 합치도 H를 제안하였다. 본 연구에서는 이를 확장하여 $m{\times}m$ 분할표에 대한 합치도 H와 그 분산을 구한다. 또한 k의 역설과 주변분포와의 관계를 증명하고, $3{\times}3$ 분할표 예제를 이용하여 기존의 합치도들과 비교한다. A measure of agreement H in$2{\times}2$ contingency table was proposed by Park and Park (2007) to resolve the two paradoxes of k. In this study, we generalize H to where the number of categories is greater than two and derive its asymptotic large-sample variance. We also explain the relationships between k's paradoxes and marginal distributions. Using some examples of $3{\times}3$ contingency tables, the behaviors of H and other measures of agreement are compared.