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Thermal design criteria for long-term durability of ceramic catalyst substrates
백석흠,조석수 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.10
The automotive industry has traditionally used ceramic honeycomb substrates as catalyst carriers. The long-term durability of a passenger car’s converter is assessed by examining the thermal stresses resulting from the temperature variations experienced under various driving conditions. These thermal stresses constitute the majority of the total stress that the ceramic catalyst substrate experiences while in service. The radial and axial temperature distributions were measured, and the thermal stress was calculated by using the thermal expansion coefficient according to the measured temperature. The threshold stress was determined from the fatigue constant, the required lifetime and the duration of the short term strength tests. The radial temperature variation was higher than the axial temperature variation,and the axial stress was higher than the radial stress because the thermal stress is dependent on the elastic modulus. The radial and axial stresses exist below the threshold thermal stress over the entire engine speed range.
Reliability design of preventive maintenance scheduling for cumulative fatigue damage
백석흠,조석수,김현수,주원식 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.5
As the cumulative running times of a locomotive truck increases, degradation such as fatigue, wear, and deterioration occur. Particularly the container train and uncovered freight train, their maintenance cost during their lifetime is three times more than the manufacturing cost. Generally, for the freight train, corrective maintenance to repair a bad part after a breakdown is not adapted; however, preventive maintenance that fixes a bad part before a breakdown is. Therefore, it is important and necessary to establish a system of optimal preventive maintenance and exact maintenance period. This study attempts to propose a preventive maintenance procedure that predicts a repair period using reliability function and instantaneous failure rate based on fatigue test and load history data. Additionally, this method is applied to the end beam of an uncovered freight train, which is the brake part, and its usefulness is examined and analyzed.
Optimization of process parameters for recycling of mill scale using Taguchi experimenal design
백석흠,홍순혁,조석수,장득열,주원식 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.10
The present work submits an investigation about the optimum process parameters and quality improvement of mill scale recycling. With increasing concerns on environmental issues, the recycling of materials of all types has become an important issue. In this paper, an optimization method is developed to improve quality in mill scale recycling. The optimum configuration of process parameters to achieve high metallization efficiency was determined by experiments. The Taguchi method, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA) and rsponse surface optimization are employed to find the main effects and to determine their optimum process parameters. The significant process parameters were identified and their effects on mill scale recycling were studied. Finally, a confirmation experiment with the optimal levels of the process parameters was carried out to demonstrate the effectiveness of the Taguchi method.
백석흠(Seok Heum Baek),윤정환(Jeong Hwan Yoon),정우성(Woo Sung Jung),하형수(Hyeong Soo Ha),정성식(Sung Sik Chung),염정국(Jeong Kuk Yeom) 대한기계학회 2014 大韓機械學會論文集B Vol.38 No.2
본 연구에서는 바이오디젤연료 혼합비변화에 대한 디젤엔진의 배기특성에 대해 조사하였다. 실험에 사용된 연료는 경유와 바이오디젤(폐식용유) 혼합연료 BD3, BD5, BD20, BD50 및 BD100을 사용하였으며, 실험변수로서 분사압력(ΔPinj)을 400bar, 600bar, 800bar, 1000bar 및 1200bar로 설정하였다. 분사압력과 바이오디젤 혼합연료 혼합비에 따른 정량적인 NOx와 Soot의 배기특성 해석을 위하여 통계학에 기초한 피어슨 상관계수와 스피어만 상관계수의 개념을 도입하였다. 본 연구의 결과로서 실험 조건 전체에 대한 피어슨 상관계수는 -0.732, 스피어만 상관계수는 -0.724로 NOx와 Soot 발생의 상관관계가 선형적이다. 특히 분사압력 800bar 조건에서 피어슨 상관계수가 -0.089으로 NOx와 Soot 배출량 상관관계가 0에 가깝기 때문에, 바이오디젤 연료 혼합비 제어를 통한 NOx와 Soot의 동시저감이 가능하다고 판단된다. In this study, the characteristics of exhaust gas as a function of the biodiesel mixing ratio were investigated. Diesel and waste oil were used for preparing mixed fuel, and the ratios of the mixed fuel were varied in the BD3~BD100 range. The injection pressures(ΔPinj) was considered as an experimental variable and was set to 400 bar, 600 bar, 800 bar, 1000 bar, and 1200 bar. Furthermore, for quantitatively analyzing the characteristics of exhaust gas(NOx and Soot), the concepts of Pearson correlation coefficient and Spearman rank-order correlation coefficient based on statistics were introduced. Consequently, it was found that the correlation of the emission of NOx and Soot is linear, and the Pearson and Spearman coefficients are -0.732 and -0.724, respectively, under all analysis conditions. Especially, for the injection pressure of 800 bar, a simultaneous reduction in NOx and Soot emission is possible by controlling the biodiesel mixing ratio. This is because the correlation coefficients of NOx and Soot emissions were nearly 0, as the Pearson correlation coefficient was -0.089.
백석흠(Seok-Heum Baek),김강민(Kang-Min Kim),조석수(Seok-Swoo Cho),이경영(Kyoung-Young Lee),홍순혁(Soon-Hyeok Hong),장득열(Deuk-Yul Jang),주원식(Won-Sik Joo) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-
Compromise decision support problems are used to model engineering decisions involving multiple trade-offs. These methods typically rely on a summation of weighted attributes to accomplish trade-offs among competing objectives. This paper gives an interpretation of the decision parameters as governing both the relative importance of the attributes and the degree of compensation between them. The approach utilizes a mathematical decision model, the compromise decision support problem, which is a multi-objective formulation based on mathematical programming and goal programming. Examples are included to illustrate the effect of fatigue reliability design on the optimization process.