熱變形이 軟鋼의 破壞靭性에 미치는 影響

鄭世喜,金台永,金洙鏞 전북대학교 공업기술연구소 1983 工學硏究 Vol.13 No.-

연성파괴 해석을 위한 비선형 유한요소 모델의 개발 -소형 컴퓨터를 위한 -

정세희,조규종 대한기계학회 1986 대한기계학회논문집 Vol.10 No.1

본 연구에서는 선단요소 해법의 방법을 토대로 소형컴퓨터를 위한 비선형 유한요소의 개발을 시도한 것이다. 주로 참조한 선단요소 해법의 프로그램은 Hinton과 Owen이 작성한 프로그램이며 원판메모리를 최대로 활용하여, 활동변수를 최소화 시키므로써, 실제 소형컴퓨터인 HP-3000II(512KB) 컴퓨터에서 총 자유도가 1000정도 되는 유한요소까지는, 해석이 가능하도록 만들어지게 되었다. 이와같이 완성된 프로그램의 응용성과 신뢰성을 검토해 보기 위해서 표준 CT 시편의 유한요소 를 작성하여(124 element, 428 node, 941 freedom) 크랙선단에 형성되는 소성역의 형상과 소성변형 크기를 수치적으로 추적하여 본 결과, 실험결과와 매우 잘 일치함을 볼 수 있어서 프로그램의 신뢰성을 확인 할 수 있었다. 이때 실험은 SUS-304스테인 레스강단의 소성역을 형성시킨다음, 재결정 방법에 의해 소성역의 형상과 크기를 가시 화 및 정량화 하여서 계산결과와 비교 하였다. In this paper, the frontal method based elastic-plastic F.E.M. program for mini-computer was developed. Since, the executable source program size was restricted by the system core memory size on the mini-computer, the active variables were memorized by the element base and the nonactive varables were memorized to the external disc file. The active variables of the finally developed program were reduced enough to execute about 1,000 freedom finite element on the mini-computer on which available variables were restricted as 32,767 integers. A modified CT fracture test specimen was examined to test the developed program. The calculated results were compared with experimental results concerning on the crack tip plastic deformation zone. Recrystallization technique was adopted to visualize the intensive plastic deformation regions. The Von-Mises criterion based calculation results were well agreed with the experimental results in the intensive plastic region which was over than 2% offset strain. The F.E.M. results using the developed program were well agreed with the theoritical plastic boundary which was calculated by the stress intensity factor as r$_{p}$=(K$_{1}$$^{2}$/2.pi..sigma.$_{y}$$^{2}$).f(.theta.).).).

高溫에서 疲損勞傷이 Stainless Steel의 破壞靭性에 미치는 影響에 關한 硏究

鄭世喜,林載奎,李宗基 전북대학교 1982 論文集 Vol.24 No.-

The latest industrial machinery is usually used under the severe conditions such as high temperature, high pressure and high load because it needs the best efficiency. The austenitic stainless steels(SUS 316) are well suited for high temperature and high pressure service because of their creep resistance and high ductility. In this paper, in order to investigate the variation of fracture toughness of the specimens given repeat stress at 450℃, decreasing temperture of ductility, instrumented charpy impact test was carried out from-150℃ to 100℃. The results are summerized as follows ; 1. The fatigue life at 450℃ is reduced by 70 percent than that at room temperature. 2. When the specimens are damaged by the fatigue at 35kg/㎟ and at cyclic numbers with the same ratio on N_f, the difference between 450℃ and room temperature in hardness increasing ratio is 7%, and 5% at 30kg/㎟ 3. The maximum distance of work hardened zone by the fatigue damage at room temperature is larger than at 450℃. It means that the plastic deformation occurs easily because the yielding stress is lower at room temperature than at 450℃. 4. The fracture energy(E_f) decreases with the increase of nominal stress and rate of damage.

鋼 熔着金屬의 熱變形脆化에 關한 硏究

鄭世喜,金台永,林載奎,鄭熙敦,朴昌彦 全北大學校 1984 論文集 Vol.26 No.-

The susceptibility of weld metal(AWS, F76-EH14) on hot straining embrittlement has been examined. The sharp notch was machined on the weld metal of 1st bead and on coarse-grained HAZ transformed by next pass. After machining the notch, these specimens were bended at 250℃ to receive the hot straining embrittlement and they were done COD fracture toughness test by the three point bending, and then the change of plastic zone at notch tip was evaluated by microhardness test. The obtained results are summarized as follows. 1. Fracture toughness of weld metal was greater than that of base metal. 2. Fracture toughness of the coarse-grained HAZ was similar to that of weld metal. 3. Hardness of weld metal reheated by next pass was lower than that of weld metal owing to the effect of heat treatment. 4. Plastic deformation of the coarse-grained HAZ was less than that of weld metal.

改正商法上의 監事의 職務權限

鄭世喜 東亞大學校 敎育大學院 1984 敎育大學院 論文集 Vol.10 No.-

Der geanderte Teil des Handelsgesetzes legt sein Schwergewicht auf einen Teil der allgemeinen Bestimmungen und auf das Gesellschaftsgesetz, er ist ein extensiver Umfang, der etwa 150 Paragraphen enthalt. Unter den Paragraphen ist die Befugnisverteilung in einer Organisation, deren Aufgabe die Aktivierung der Aktiengesellshaftserwaltung ist, besonders von Bedeutung. Die im alten Handelsgesetz anerkannten Uberwachungsrechte der Geschftsfuhrung des Vorstandes wuden nicht ganz wirkungsvoll sondern nur formell ausgefuhrt, und in der Aktiengesellschaft trat ein "pathologisches Phanomen" ein. So kann man die Verstarkung der Befugnis des Aufsichtsrates als eine Maβnahme zur Beseitigung dieses "pathologischen Phanomens" verstehen. Aber das neue Handelsgesetz mag wohl viele Probleme zur Ausubung der beiden hervorbringen, weil in ihm sowohl die Uberwachungsrechte der Geschaftsfuhrung des Aufsichtsrates als auch die der Geschaftsfuhrung des Vorstandes anerkannt werden. Man interpretiert das Gesetz:die der Geschaftsfuhrung des Vorstandes anerkannt werden. Man interpretiert das Geset: die Uberwachung der Geschaftsfuhrung des Aufsichtsrates ist die Uberwachung der Gesetzmaβigkeit und der Gultigkeit. Trotz solcher Interpretation ist dieses Gesetz eine deutliche Doppelkompetenz:Wenn selbst die obengenannte Gultigkeit in die Uberwachung der Geschaftsfurung des Aufsichtsrates eingeschlossen wird, bleibt dies als eine unumstrittene Wiederholung. So stoβen die beiden Kompetenzen bei ihre3n Ausubungen zusammen. Bei der Uberprufung verschiedener Bestimmungen uber die Rechte und Pflichten des Aufsichtsrates tauchen viele Fragen auf, Z.B. ob die Uberwachung der Geschaftsfuhrung durch den Aufsichtsrat tatsachlich wirkungsvoll ist. 1)Trotz der Unterschiede zwischen unserem und dem japanischen Unternehmungsklima nahm man das im jahre 1974 geanderte japanische Handelsgesetz kritiklos auf. 2)Wenn die Uberwachung der Geschaftsfuhrung von dem Vorstand nicht ideal ausgefuhrt wurde, muβte man das Vorstandssystem wesentlich reformieren, um den Vorstand gut funktionieren zu lassen. Geradezu ist das der Fehler, daβman die Probleme nicht durch diesen Verbesserungsprozeβsondern durch die (Erteilung der) Uberwachungsrechte des Aufsichtsrates ohne Muhe zu losen versucht. 3)Und dies bedeutet eine Verachtung des Wesensunterschieds zwischen dem Vorstand und dem Aufichtsrat, wenn man die Aufsichtsratsmitgleder, die in der Geschaftsfuhrung gerde als Auβenseiter angeshen werden, die Geschaftsfuhrung des Vorstandes Aufsicht fuhren laβt. 4)Zum Schluβ:Unter dem Anfsichtsratsystem wird zwar der hohe Rang des Aufsichtsrates gesichert, aber der Aufsichtsrat hat im Vergleich zu dem Vorstand doch schwachere Macht. Daβman den Aufsichtsrat zu allen Uberwachungsrechte befugt, bedeutet deshalb nichts, ja man kann davon kaum eine beachtliche Wirkung erwarten.

閉鎖會社의 立法에 관한 硏究

鄭世喜 동아대학교 경영대학 1992 經營硏究 Vol.- No.6

The factual setting in which close corporations are formed and operated differs substantially from that in which publicly held corporations function. Yet close corporations in Korea are subject to the general corporation law and the securities exchange law, statutes designed for publicly held corporations. The issuance of securities, the internal organization, and the day-to-day operation of close corporation are thus subject to rules designed for another game. This article will propose rules designed expressly for close corporations. The concept of a close corporation law is not new. More than 100 years ago, Germany developed such a law which has been imitated by a number of countries including France and Japan. Great Britain has special statutes governing private companies. There are also a number of American statutes which contain special provisions for close corporations. All of these laws are designed to deal with the same problem : how to permit a small group of businessmen to obtain the benefits of limited liability quickly and at a reasonable cost, thus encouraging small business and facilitating joint ventures by large enterprise without at the same time exposing the public at large to the danger of stock swindles. The proposed close corporation law set forth in this article is designed to be an integral part of Korea s existing corporation law and the law regulating securities. It presupposes the continued existence of the general corporation law and of the securities exchange law. It is thus important to consider the justification for the continued existence of present statutory provisions, which are complementary to the proposed close corporation law.

熔接이음의 胞性破壤에 미치는 疲勞의 影響

鄭世喜 全北大學校 1971 論文集 Vol.13 No.-

It is practical importance of cyclic stressing on brittle fracture of welded joints, since many welded steel structures are subjected to cyclic stresses and are used under the conditions where brittle failure may occur. To examine the influence, the strain at the welded joints under cyclic stressing was measured by the Cu electroplating method. After the cyclic strain at the position where fatigue crack might occur was determined, the tensile fracture behaviour of the fatigued specimens was examined between room temperature and -196℃ by the photoelastic coating technique. The reduction of fracture strength and the rise of ductile-brittle transition temperature referred to the magnitude of cyclic strain were studied and discussed. The experiment shows that the fatigue crack has an effect on brittle fracture,

高張力鋼熱影響部 微視組織의 類別

鄭世喜,金台永,李聖哲 全北大學校 1979 論文集 Vol.21 No.-

The assessment of the toe HAZ fracture toughness is one of the most troublesome problems to resolve because the fracture toughness depends to a large extent upon microstructural gradients such as variations of the microstructure and the grain size in the HAZ and because such microstructural characteristics are directly influenced by the thermal cycle during welding. The aim of the present study is to classify metallurgically the distribution of the constituents of microstructure in the HAZ by measuring Vickers microhardness. The metallurgical observation and microhardness measurement for the toe HAZ of 60㎏/㎟ low alloy steel, which was submerged are welded as bead-on-plate, were carried out. The experimental results were summarized as follows; There is a linear relationship between the ratio of hardness Hv/(Hv)_M (Hv:Vickers hardness, (Hv)_M : Vickers hardness of 100% martensite) and the area percentage of their structural constituents, and it is independent on chemical composition of materials. It was concluded, consequently, that the transformation behavior for the structure of other 60㎏/㎟ low alloy steel in the HAZ and the ratio of mixture of structural constituents in its every position can be quantitatively classified by the ratio of microhardness Hv/(Hv)_M.

1930-1990년대 영화 의상에 나타난 젠더 정체성(II)- 제 3의 성(the third sex)을 중심으로 -

정세희,양숙희 대한가정학회 2002 Human Ecology Research Vol.40 No.6

The third sex implying a mismatch between sex and gender has been regarded as an extreme socio-cultural violation. In its earlier version, such a violation was expressed by cross-dressing; Women?s cross-dressing was thought to invoke eroticism, while men?s cross-dressing was considered comic or delinquent. However, as feminism developed more with the homosexual identity expressed openly, the third sex began to be visual. Thus, in 1990?s, some homosexual movies began to develop to be pluralized enough to suggest the third sex and thereby, change the negative sex into a positive one. In this study, such a pluralization is discussed in terms of invisibility, dichotomy and androgyny.The cross-dressing movies show females in male attire or males in female attire to reflect the third sex. The cross-dressing may be divided into men?s playful cross-dressing, women?s political cross-dressing and homosexuals? cross-dressing or ?drag?.Gender identity is not an attribute fixed by some physical characteristics, but it tends to be changed or expanded by some social factors over time. In short, it may be a flexible, plural, individual and self-introspective attribute. Movies present diverse types of gender identities, and in particular, the movie costumes specify them. In other words, the costumes may be model means expressing the gender identities, and the gender identities shown in the movies tend to be imitated, re-created or assumed by the audience.주제어(Key Words): 젠더(gender), 제 3의 성(the third sex), 크로스드레싱(cross-dressing), 드랙(drag)

二重 Norch 先端에서 塑性變形拳動에 관한 硏究

鄭世喜,林載奎,金貴子 全北大學校 1986 論文集 Vol.28 No.-

The fracture toughness of elasto-plastic materials was directly affected by the size, shape of plastic zone which are great important parameter in large scale fracture mechanics. This paper is to observe the influences of the interference of notches on plastic deformation at notch tip of double notch. Specimens were tested by four point bending, and then the shape of the plastic deformation could be visualized with the technique of recrystallization. Beside, numerical method for the analysis of the plastic zone with a F.E.M. (Finite Element Method) were used. The obtained results are summarized as follows: 1) The behavior of plastic zone on double notch was different from single notch. 2) When the plastic zone was saturated at a limitation on the middle between the notches, the behavior of the plastic deformation of double notched specimen was similar to that of the single notch. 3) Maximum equivalent plastic strain was shown at the tips of both single and double notch. 4) The evaluated model of plastic zone by F.E.M. corresponded to the results of the experiment.