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Local compression에 의한 CTOD 시편내의 용접잔류응력 재분포
주성민,윤병현,장웅성,방한서,방희선,노찬승,Joo, Sung-Min,Yoon, Byung-Hyun,Chang, Woong-Seong,Bang, Han-Sur,Bang, Hee-Seon,Ro, Chan-Seung 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
When conducting CTOD test, especially in thick welded steel plate, fatigue pre-cracking occasionally failed to satisfy the requirements of standards thus making the test result invalid. Internally accumulated residual stress of test piece has been thought as one of the main reasons. The propagation of fatigue crack, started from the tip of machined notch, which might have propagated irregularly due to residual stress field. To overcome this kind of difficulty three methods to modify the residual stress are suggested in standard i.e. local compression, reverse bending and stepwise high-R ratio method. In this paper not only multi pass welding but also local pre-compressing process of thick steel plate has been simulated using finite element method for clarifying variation of internal welding residual stress. The simulated results show that welding residual stress is compressive in the middle section of the model and it is predominantly increased after machining the specimen. Comparing as-welded state all component of the welding residual stress changing to compressive in the tip of machine notch whereas residual stress of the outer area remain as tensile condition relatively. Analysis results also show that this irregular residual stress distribution is improved to be more uniformly by applying local compression.
주성민,방희선,한준의,김경학,안병호,Joo, Sung-Min,Bang, Hee-Seon,Han, Jun-Ui,Kim, Kyoung-Hak,Ahn, Byoung-Ho 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.4
Nowadays, the weight lightening of automotive is required as conserving the environment has become a major worldwide issue. To solve this issue, various researches for the use of light materials(Alalloy, Mgalloy)and ultra high strength steel as substitutes of the current structural material have been carried out. Application of laser stitch welding to the assembly of automotive produces improvement in strength, lightening of body, higher fuel efficiency, lower production cost as well as reduction in assemble line due to its fast welding speed, superior accessible and weld quality. This process overcomes the shortcomings of the current resistance spot welding such as high electricity consumption, electrode replacement, and economical, technical limitation in design and production method of automotives.
푸드 트럭의 지각된 서비스 품질이 고객만족과 재방문의도에 미치는 영향
주성민(Joo Sung Min) 한국외식경영학회 2018 외식경영연구 Vol.21 No.4
본 연구의 목적은 푸드 트럭의 서비스 품질이 고객만족과 재방문 의도에 미치는 영향을 분석하여 외식산업에서 경쟁적인 우위를 점할 수 있는 푸드 트럭의 효율적인 방안을 제안하는 것에 있다. 따라서 본 연구에서는 푸드 트럭을 이용한 경험이 있는 서울지역의 푸드 트럭 이용자를 대상으로 2018년 5월 1일부터 5월 31일 동안 총 250부의 설문지를 배포하였으나 그 중 불성실하게 응답한 설문지 27부를 제외한 223부의 설문지가 최종적으로 연구 자료로서 사용되었다. 본 연구의 수집된 자료는 IBM SPSS Statistics 23.0 통계패키지 프로그램을 이용하여 분석하였다. 그리고 사용한 분석방법은 다음과 같다. 빈도분석, 탐색적 요인분석, 신뢰도 분석, 회귀분석을 실시하였다. 가설 검증 결과 첫째, 푸드 트럭의 서비스 품질은 고객만족에 정(+)의 유의한 영향을 미치는 것으로 나타났으나 접점 서비스품질은 유의한 영향을 미치지 않는 것으로 조사되었다. 둘째, 푸드 트럭의 고객만족은 재방문에 정(+)의 유의한 영향을 미치는 것으로 나타났다. 셋째, 푸드 트럭의 서비스 품질은 재방문 의도에 정(+)의 유의한 영향을 미치는 것으로 나타났으나 접점 서비스품질은 유의한 영향을 미치지 않는 것으로 조사되었다. 이에 본 연구결과를 바탕으로 푸드 트럭을 이용하는 고객들의 기대를 만족시킬 수 있는 푸드 트럭 품질과 접점서비스품질의 전략적 방안에 대한 시사점이 제시되었다. The purpose of this study is to analyze the impact of food truck service quality on customer satisfaction and revisit intention and propose efficient measures for food truck that can have a competitive advantage in the food industry. Therefore, in this study, empirical data was users who had experience using food trucks in Seoul of Korea and total 223 completed during the period of May 1 to May 31, 2018. It includes frequency analysis to look at the demographic features of the sample and factor analysis to classify the customer satisfaction, service quality and revisit intention of food truck. The objectives of this research, therefore, are as follows: first, the quality of service of food truck will have positive and significant impacts to customer satisfaction, but that the quality of encounter services were not. Second, the customer satisfaction will have positive and significant impacts to the revisit intention. Third, the quality of service of food truck will have positive and significant impacts to the revisit intention, but that the quality of encounter services were not. The implications for the strategic measures of food truck quality and encounter service quality were suggested to customers.
Fe - 30Al - 5Cr 합금의 미세조직 및 DO3 - B2 천이온도에 미치는 Ti , Hf 및 Zr 의 첨가효과
김성수(Sung Su Kim),주성민(Sung Min Joo),오선훈(Seon Hun Oh),김관휴(Kwan Hyu Kim),최답천(Dap Chun Choi) 한국주조공학회 2001 한국주조공학회지 Vol.21 No.1
The changes in the microstructures and D0₃↔ B2 transition temperature were investigated for Fe-30at.%Al-5at.%Cr alloy with the ordered D0₃structure when Ti, Hf and Zr were added respectively. The addition of Cr has no effect on the microstructure. However, as the amount of Ti addition increased, the grain size became smaller. Addition of Ti+Hf, Ti+Zr and Ti+Hf+Zr also showed the similar effect. When 20at.% of Ti was added, the second phase precipitates on the substrate. The addition of Cr, Hf and Zr alone has no effect on D0₃↔ B2 transition temperature. However, as the amount of Ti addition increased by 5, 10, 15 and 20at.%, the transition temperatures showed 929, 930, 960 and 930℃ respectively.
손용운,주성민,정헌생,Sohn Yong-Un,Joo Sung-Min,Chung Hun-Saeng 한국재료학회 2004 한국재료학회지 Vol.14 No.5
$Si_3$$N_4$ ceramics have been identified as one of the promising structural ceramics. This study has been carried out to investigate of the synthetic behaviors of $Si_3$$N_4$ derived from domestic silica-stone by direct nitriding method. The silicon nitridation reaction has been studied in the temperature range of $1300~1550^{\circ}C$. Below the $1400^{\circ}C$, the nitriding rate was measured to be 16%. For the temperatures higher than the $1400^{\circ}C$, $\beta$-$Si_3$$N_4$ phase was formed mainly, and the nitriding rate showed above 98%. With the increasing of sample weight of silicon powder, the nitriding rate and $\beta$-$Si_3$$N_4$ phase increased at $1400^{\circ}C$ for 2 hours. The shape and particle size of$ Si_3$$N_4$ powder synthesized at $1400^{\circ}C$ for 2 hours showed the irregular angular-type and 10 $\mu\textrm{m}$, respectively.
반응소결법에 의해 제조된 Fe-Al 합금 예비성형체의 특성에 미치는 제인자의 영향
주형곤,박성혁,주성민,최답천 ( Hyung Gon Joo,Sung Hyuk Park,Sung Min Joo,Dap Chun Choi ) 한국주조공학회 1997 한국주조공학회지 Vol.17 No.1
N/A The main aim of the present study is to investigate the effects of several processing parameters on the characteristics of Fe-Al alloy preform manufactured by reactive sintering process. The processing parameters include preform composition of 25, 40, 50, 60 and 75at.%Al, compacting pressure of 10, 20 and 30㎏/㎠, and mean Al particle size of 29, 66 and 187㎛. Mean Fe particle size was 39㎛. The density of preform processed under same compacting pressure was not affected by changing Al composition. The preform with Al compositions of 25, 40, 50 and 60at.%Al swelled after reactive sintering process, thus having lower density than the green compacts. The preform with Al compositions of 75at.%Al, however, shrinked after reactive sintering process, thus having higher density than the green compacts. Ignition temperature increased with increasing compacting pressure, and increased with increasing Al composition at the fixed compacting pressure. And adiabatic temperature decreased with increasing compacting pressure at the fixed Al composition, and increased with increasing Al composition at the fixed compacting pressure. The size of compound particles increased with increasing Al composition. Especially, The size of compound particles increased largely in the case of 75at.%Al. It was observed that 50at.%Al preform have three dimentional network structure having a homogeneous and fine decreasing Al particle size.
자동차용 강판의 MAG 용접시 최적용접조건 선정에 관한 연구
방한서,방희선,주성민,노찬승,성보람,석한길,Bang, Han-Sur,Bang, Hee-Seon,Joo, Sung-Min,Ro, Chan-Seung,Sung, Bo-Ram,Suk, Han-Gil 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3
The optimization of the welding parameters was studied to maximize the weldability and minimize the amount of spatter in the MAG welding of automotive steel sheets under different shielding gas composition ratio. JS-EFSC, JS-SPHC steel plates and Ar mixture gases were used as a substrate and shielding gas for welding respectively. The five welding parameters were selected through preliminary experiments and their effects on the weldability were analyzed. Experiments were performed using the Taguchi experimental method. As results, appropriate range for welding could be achieved. Amount of spatter in 80%Ar+20%$CO_2$ shielding gas was 20% of that of $CO_2$welding. Therefore, in terms of high productivity and welding cost, Ar mixture gas(80%Ar+20%$CO_2$) was recommended as a shielding gas for application of MAG process, indicating the low spatter and good weld quality.