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티타늄 합금의 연마제 워터 제트 절단에 의한 절단표면 특성
정남용,진윤호,Chung Nam-Yong,Jin Yun-Ho 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.1
Abrasive waterjet (AWJ) can provide a more effective means for precision of difficult -to-machining materials such as ceramics and titanium alloys. The present study is focused on the surface roughness of abrasive waterjet cut surfaces. This paper investigated theoretical and experimental surface characteristics associated with abrasive waterjet cutting of titanium alloy Gr2. It is shown that the proper variations of several cutting parameters such as waterjet cutting pressure, cutting speed and cutting depth improve the roughness and characteristics on specimen surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of titanium alloy Gr2, the optimal cutting conditions to improve the surface roughness and precision were proposed and discussed.
정남용,박철희,Chung, Nam-Yong,Park, Cheol-Hee 한국자동차공학회 2007 한국 자동차공학회논문집 Vol.15 No.4
In this paper, an evaluation method of fracture toughness on interface cracks was investigated in friction welded dissimilar materials with interfacial edge cracks. To establish a reasonable strength evaluation method and fracture criterion, it is necessary to analyze stress intensity factor under the load and residual stress condition on friction welded interface between dissimilar materials. The friction welded specimens with an edged crack were prepared for analysis of stress intensity by using the boundary element method (BEM) and the fracture toughness. A quantitative fracture criterion for friction welded STS 304/SM 45C with interface crack is suggested by using stress intensity factor, F and the results of fracture toughness experiment.
Al/ Epoxy 이종 접합체에 대한 계면강도의 평가방법
정남용,Chung, Nam-Yong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.11
The application of bonded dissimilar materials to industries as automobiles, aircraft, rolling stocks, electronic devices and engineering structures is increasing gradually because these materials, compared to the homogeneous materials, have many advantages for material properties. In spite of such wide applications of bonded dissimilar materials, the evaluation method of quantitative strength considering the stress singularities for its bonded interface has not been established clearly. In this paper, the stress singularity for Bctors and the stress intensity factors were analyzed by boundary element method(BEM) for the scarf joints of Al/Epoxy with and without a crack, respectively. From static fracture experiments of the bonded scarf joints, a fracture criterion and a evaluation method of interface strength in bonded dissimilar materials were proposed and discussed.
반도체 패키지의 층간박리 파괴역학인자 해석 및 균열진전경로 예측
정남용,박철희,Chung, Nam-Yong,Park, Cheol-Hee 한국생산제조학회 2009 한국생산제조학회지 Vol.26 No.3
This paper presents a method of calculating the stress intensity factor (K) and crack propagation direction (${\theta}_0$) at the crack-tip that is associated with delamination in the large scale integration(LSI) package. To establish a reasonable strength evaluation method and life prediction, it is necessary to assess fracture parameters under various fracture conditions. Therefore, we conducted quantitative stress singularity analysis considering thermal stress simulating the changes of crack length (a), (h) and (v) in delamination using the 2-dimensional elastic boundary element method (BEM), and from these results predicted crack propagation direction and path.
SUH35/SUH3 마찰용접 접합계면에 대한 잔류응력 특이성의 해석
정남용(Nam yong Chung),박철희(Chul Hee Park),이대영(Dae young Lee) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_2
With increasing use of SUH35/SUH3 dissimilar materials for automotive engine valve, it is required that stress singularities on an interface for friction welded dissimilar materials analyzed to establish strength evaluation. The stress singularity index(λ) and stress singularities factor(Γ) were calculated from using the results of stress analysis to consider residual stress and loads. The stress singularities on variations for shapes and thickness of welded flashes were analyzed and discussed. This paper suggested that the strength evaluation by using the stress singularity factors as fracture parameters, considering the stress singularity on an interface edge of friction welded dissimilar materials will be useful.
마찰용접에 의한 이종재 접합계면에 대한 응력특이성 해석
정남용(Nam Yong Chung),박철희(Chul Hee Part) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, the stress singularity on interface of dissimilar materials by friction welding was investigated by using 2-dimensional elastic boundary element method. It is required that stress distributions and stress singularities at an interface for friction welded dissimilar materials analize to establish strength evalution. The stress singularity index() and the stress singularity factor were calculated front the results of stress analysis. The stress singularities on variations for shapes and thickness of friction welded flashes were analized and discussed. This paper suggested that the strength evalution by using the stress singularity factors as fracture parameters, considering the stress singularity at an interface edge of friction welded dissimilar materials will be very useful.
응력특이성을 고려한 SUH35/SUH3 마찰용접재의 강도평가
정남용(Nam Yong Chung),박철희(Chul Hee Park) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
Recently, application of friction welded SUH35/SUH3 is increasing in the manufacturing process of automotive engine valves . For securing its reliability and a reasonable strength evaluation method, it is necessary to assess stress singularity under the residual stress condition on the friction welded interface between dissimilar materials. In this paper, strength evaluation method of friction welded materials was investigated by boundary element method and static tensile testing. An advanced method of quantitative strength evaluation for SUH35/SUH3 friction welded material is to be suggested by establishing fracture criterion by using stress singularity factors.
대구ㆍ경북지역 초등학교 교사들의 농업문해 수준에 관한 연구
정남용(Chung Nam Yong) 한국실과교육학회 1998 한국실과교육학회지 Vol.11 No.1
The purpose of this study was to assess the knowledge of issues related to agriculture of elementary school teachers in TaeguㆍKyoungbuk area. This study was conducted to determine if selected demographic characteristics were predictive of greater agricultural knowledge. The sample for this study consisted of 304 elementary school teachers including 202 teachers in Taegu area and 201 teachers in Kyoungbuk area. Descriptive statistics were computed to compare the knowledge and attitude scores. Null hypotheses were tested using a t-test and a stepwise linear regression with an a priori alpha level of .05. The following conclusions were drawn from this study. 1. Elementary school teachers in Taegu area are more knowledgeable about agriculture than elementary school teachers in Kyoungbuk area. 2. Elementary school teachers who are living in a larger population area, have taken a agriculture course in high school, have been a member of 4-H, have experience on growing plants, and have been reading newspapers.