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趙相明(Sang-Myung Cho),堀川浩甫(Kohsuke Horikawa) 한국해양공학회 1988 韓國海洋工學會誌 Vol.2 No.2
In order to consider the concept of the 'fitness for purpose' in fatigue design of offshore structure, fracture mechanics is applied to evaluate initial or weld defects.<br/> Generally, linear elastic fracture mechanics has been applied to estimate initial fatigue crack propagation rate as well as long fatigue crack propagation rate. But, initial fatigue crack propagation rate in elasto-plastic notch field may not be characterized by application of stress intensity factor range △K, because plastic effect due to stress concentration of notch may contribute to initial crack propagation. Therefore, to introduce the plastic effect into fatigue crack driving force, in this studty, the evaluating method of J -integral range △J, was developed for initial fatigue cracks in elasto-plastic notch field. The interpolation function for J -integral by Willson was modified for application to notch field. In calculation of △J obtained from the modified J -integral, stress gradient and crack closure behavior in the notch field were considered.<br/> The initial crack propagation rates in the notch fields of mild steels and high tensile strength steels were correlated to △J. As the result, it was cleared that the present △J is applicable to characterize the fatigue crack propagation rates in both the elastic and elasto-plastic notch fields.
아연도금강판에 대한 중첩펄스 MIG 용접에서의 파형제어와 기공 발생 특성
조상명,김기정,이병우,Cho Sang-Myung,Kim Ki-Jung,Lee Byung-Woo 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.1
Recently, application of arc welding to galvanized carbon steel sheet is on the increasing Ould in the fields of automobile and construction industries. In arc welding process, zinc is evaporated in weld pool, even under the appropriate welding condition and produce blowhole and/or pit. Zinc gas cause instability of arc and increase spatter and fume. This research is purposed to minimize the heat-input and the formation of porosities in the welded joint of the galvanized carbon steel sheet using variable polarity AC wave pulse MIG welding system. An appropriate welding condition which showed low spatter and good bead appearance was acquired by applying the AC pulse MIG welding machine to DC duplicated MIG welding with the solid wire. When oxygen gas was added to shield gas of MIG welding for galvanized steel sheet, arc length was increased and arc stability was improved. In the AC duplicated welding, the loss of galvanized layer was decreased as the amount of heat-input was decreased when the EN ratio was increased under the condition that average welding current was evenly set.
벤처 창업팀의 다양성이 창업 성과에 미치는 영향에 관한 연구
조성주 ( Sungju Cho ),이상명 ( Sang-myung Lee ) 한국중소기업학회 2020 中小企業硏究 Vol.42 No.1
지금까지 창업 성과에 관한 연구는 주로 창업자의 특성, 역량, 전략이 성과에 미치는 영향에 관한 연구들이 주를 이루고 있었다. 그러나 과학기술의 발달과 경영환경의 복잡성은 개인에 의한 창업보다 창업팀에 의한 창업을 활성화시키고 있다. 이에 따라 창업팀 특성이 창업 초기 기업에 미치는 영향에 대한 이론적이고 실제적인 연구의 필요성이 제기되었다. 본 연구는 벤처 창업팀의 다양성이 창업 성과에 미치는 영향을 확인하였다. 연구 모형을 검증하기 위해 전국 17개 지역, 18개 창조경제혁신센터 사업에 참여한 적이 있는 벤처 창업 기업 중 287명의 대표가 응답한 설문을 바탕으로 회귀분석을 통해 가설을 검정하였다. 분석 결과, 인구통계적 다양성에서는 성별 다양성만 비재무적 성과에 부정적 영향을 미쳤다. 정보 다양성은 경력 다양성이 재무적 성과에, 교육수준 다양성이 비재무적 성과에 긍정적 영향을 미쳤다. 또한 이전 공유경험이 높을수록 재무적 성과에 긍정적 영향을 미친 것으로 나타났다. 가치 다양성은 재무적, 비재무적 성과 모두에 부정적인 효과를 미쳤다. 이상의 연구 결과를 기반으로 연구의 시사점과 향후 연구 과제 등을 제시하였다. Many researchers conducted studies on the relationship between entrepreneur’s characteristic, capability, strategy and performance of new venture. However, the development of scientific technique and the complexity of the business environment have stimulated entrepreneurial teams rather than individuals. Therefore, the necessity of theoretical and practical study on the effect of the characteristics of an entrepreneurial team on the new venture companies was suggested. Initial research on entrepreneurial team diversity has primarily addressed the impact of demographic diversity on performance. In order to verify the research model of this study, 287 delegates of new venture companies that participated in the projects at the 18 Centers for Creative Economy & Innovation in 17 regions of the country conducted validity and reliability test based on the questionnaire to which they answered. The result shows that only gender diversity among demographic diversity affected non-financial performance. Information diversity influenced career diversity on financial performance and diversity in education on non-financial performance. Also, the higher the previous sharing experience, the better the financial performance. Value diversity has negative effect on both financial and non-financial performance. Based on the results, theoretical and practical implications are derived. Also suggested are methodological limitations and future research directions.
조상명,박정현,손민수,Cho, Sang Myung,Son, Min Su,Park, Jung Hyun 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.6
Pipe inside clad welding is mainly used to the flow pipe of sub-sea or chemical plant. For the inside clad welding to the medium pipe with the diameter of about 12", TIG welding is frequently applied with filler metal. In this case, the clad welding has the very broad weld area over $10m^2$. And, the non-destructive test (NDT) such as ultrasonic test (UT) or radiographic testing (RT) should be conducted on the broad weld area, and it costs very high due to the time-consuming work. Therefore, the present study investigated the variation of arc voltage to develop the in-line quality monitoring system for the pipe inside TIG cladding. The 4 experimental parameters (current, arc length, wire feed position, and shield gas flow rate) varied to observe the change of arc voltage and to establish the model for the monitoring. The arc voltage was decreased when the wire was fed to the backward eccentric position(over 2mm), and the shield gas flow rate was insufficient under 10L/min. In the case of the backward eccentric position over 2mm, the bead appearance was not good and the dilution ratio was increased due to deep penetration. When the shield gas flow rate was lower than 10L/min, the bead surface was oxidized.
열간단조 금형 육성용접부 내균열성 및 내열충격성 평가방법에 관한 연구
조상명,김성호,정연호,백승희,장종훈,박철규,우희철,정병호,Cho, Sang-Myung,Kim, Sung-Ho,Jung, Yun-Ho,Baek, Seung-Hui,Jang, Jong-Hun,Park, Chul-Gyu,Woo, Hee-Chul,Jung, Byong-Ho 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.3
Hardfacing is one of the frequently applying method to increase surface hardness in hot forging die. Recently, hardfacing receives great attention due to it's repair availability and low cost. In hot forging die, crack resistance and thermal shock resistance have been considered as major properties, However there are few studies for the assessment of these properties. So, it is necessary to establish the assessment method for crack resistance and thermal shock resistance in hardfacing for hot forging die. In this study, flux cored arc welding was applied to make hardfacing welds. Three point bending test was carried out to assess hardfacing weld's crack resistance, and high temperature bending test using salt bath was developed for thermal shock resistance. Consequently, it was possible to assess crack resistance and thermal shock resistance of hardfacing welds for hot forging die quantitatively.