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조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2006 한국생산제조시스템학회 학술발표대회 논문집 Vol.2006 No.5
This study is results of single-and two-spot resistance spot welding for spec steel. Test specimens were welded horizontally or vertically according to the rolling direction of base metal in two-spot welding. About whole occasions, measured acoustic emission(AE) signals are analyzed. As the results, in the case of two-spot welding, horizontal type increased elongation more than vertical type in tensile-shear test. Therefore, could know that it is profitable structurally that consider direction(or arrangement) of nugget of according to direction, if secondary process attains since resistance spot welding.
조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),조진호(Jin-Ho Cho),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2005 한국생산제조시스템학회 학술발표대회 논문집 Vol.2005 No.10
This study is result of single resistance spot welding for SPCC steel. About cross tensile specimen and tensile-shear specimen, enforced resistance spot welding and tension test. Then, about whole occasions, measured acoustic emission (AE) signals are analyzed. As the result, AE response signals that occur at resistance spot welding con tinned that is divide to 5-area. Also, fracture pattern of test specimens appeared 3 cases - shear fracture by welding shortage, tear fracture by good welding, and plug fracture by excessive welding. From getting AE data confirmed that AE techniques can be used usefully in quality control in resistance spot welding. Therefore, it is possible to estimate quality of resistance spot welding at real time if utilize this effectively.
조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2006 한국공작기계학회 춘계학술대회논문집 Vol.2006 No.-
This study is results of single-and two-spot resistance spot welding for spec steel. Test specimens were welded horizontally or vertically according to the rolling direction of base metal in two-spot welding. About whole occasions, measured acoustic emission(AE) signals are analyzed. As the results, in the case of two-spot welding, horizontal type increased elongation more than vertical type in tensile-shear test. Therefore, could know that it is profitable structurally that consider direction(or arrangement) of nugget of according to direction, if secondary process attains since resistance spot welding.
조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),조진호(Jin-Ho Cho),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2005 한국공작기계학회 추계학술대회논문집 Vol.2005 No.-
This study is result of single resistance spot welding for SPCC steel. About cross tensile specimen and tensile-shear specimen, enforced resistance spot welding and tension test. Then, about whole occasions, measured acoustic emission (AE) signals are analyzed. As the result, AE response signals that occur at resistance spot welding con tinned that is divide to 5-area. Also, fracture pattern of test specimens appeared 3 cases - shear fracture by welding shortage, tear fracture by good welding, and plug fracture by excessive welding. From getting AE data confirmed that AE techniques can be used usefully in quality control in resistance spot welding. Therefore, it is possible to estimate quality of resistance spot welding at real time if utilize this effectively.
조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),조진호(Jin-Ho Cho),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2006 한국생산제조학회지 Vol.15 No.4
In this paper, for the purpose of investigation the acoustic emission(AE) behaviors during resistance spot welding process and tension test of SPCC steels. As the results present the resistance spot welding method that can get suitable welding qualities or structural integrity estimating method. The resistance spot welding process consists of several stages: set-down of the electrodes; squeeze; current flow; forging; hold time; and lift-off. Various types of AE signals are produced during each of these stages. For tensile-shear test and cross tensile test in resistance spot welded specimens, fracture patterns are produced: tear fracture; shear fracture; and plug fracture. Tensile-shear specimens strength appeared higher than cross tensile specimens one. In case of tensile-shear specimen happened tear fracture that crack happens in most lower plate. Also, in case of cross tensile specimens, upper plate and lower plate are detached perfect fracture was exposed increases a little as acting force is lower than ordinary welding condition. Therefore, the structure which is combined by resistance spot welding confirmed that welding design must attain so that shear stress may can interact mainly.
음향방출법에 의한 저항 점용접부의 파괴특성에 대한 연구
조대희(Dae-Hee Jo),이장규(Zhang-Kyu Rhee),박성완(Sung-Oan Park),김봉각(Bong-Gag Kim),우창기(Chang-Ki Woo) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.2
In this paper, the acoustic emission(AE) behaviors were investigated with single- and 2-spot resistance spot welded SPCC specimens. Test specimens were welded horizontally and/or vertically according to the rolling direction of base metal in 2-spot welding. In the case of 2-spot welding, when tensile-shear test has below amplitudes: crack initiation 50~60㏈; tear fracture 40~50㏈. And when cross tensile test has below amplitudes: early stage 75~85㏈; yielding point 65~75㏈; post yielding 40~60㏈; plug fracture 70~80㏈ or 90~100㏈. Also, from the b-value that is slope of AE amplitude, we knew that there are lots of low amplitudes if b-value is big(i.e., tensile-shear specimen→tear fracture or shear fracture), and there are lots of high amplitudes if b-value is small(i.e., cross tensile specimen→plug fracture). As the results of fracture mechanism analyses through AE amplitude distributions, change of the b-value represented fracture patterns of materials. Correspondingly, low amplitude signals appeared in crack initiation, and high amplitude signals appeared in base metal fracture. We confirmed that these amplitude distributions represented the change or degradation of materials.
김진환(Kim Jin Hwan),조대희(Jo Dae Hee),이상진(Lee Sang Jin) 경찰대학 경찰학연구편집위원회 2013 경찰학연구 Vol.13 No.3
The article 28 of ‘The Act on Promotion of Information and Communications Network Utilization and Information Protection etc.’ and the article 29 of ‘The Act of Protection of Personal Information’ require to meet minimal stadards to prevent private information extrusion. The acts also stipulate that the violator shall be punished by imprisonment with prison labor for not more than two years or by a fine not exceeding 20 million won. Although there are articles about criminal punishment, we have few cases found guilty due to vagueness of description. Additionally, we could have an emotional discomfort to charge the victim of data leakage criminally. Nobody predict development of technology and security as to legislate them. Law enforcement also has technical difficulties to prove a violation of minimal caution duty and to interpret a law. In this research, I suggest more specific range of ‘private information’, ‘establishment and operation of information security equipment’, ‘intention’, and ‘cause-and-effect relationship’ by considering information security market analysis and intrepretion of law and judicial precedent review. Additionally, this research formulate a model of private and public joint investigation group to overcome manpower shortage of law enforcement and to secure evidence for civil action.
원공결함을 갖는 SM45C 인장시험편의 강도해석과 음향방출에 관한 사례연구
우창기(Chang-Ki Woo),이장규(Zhang-Kyu Rhee),조대희(Dae-Hee Jo) 한국생산제조학회 2007 한국생산제조시스템학회 학술발표대회 논문집 Vol.2007 No.5
This study was analyzed about load-deflection curve of SM45C metallic coupons through AE (acoustic emission) techniques mainly. Coupons that artificial defect does not exist were tested according to the speed of crosshead. First, yielding point of SM45C steel did not appear definitely compares to mild steel. So normalized all above cases to know tendency, and confirmed possibility of accelerated life test of isotropic materials. And next, coupons with differs size of circular hole defect were tested in the equal cross head speed at 5 ㎜/min. Generally AE counts appeared continually before fracture over whole unlike example of mild steel. As a result, classified 3 classes by AE amplitude & signal strength as a function of time here for signal analysis with a circular hole defect 7.5 ㎜ and analyzed. Is judged that need addition research that consider subsequentness width-ratio for searching examination of correct fracture mechanisms for this part.