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전자기력에 의한 연주 Slab 내의 교반유동에 관한 수치적 연구
이재헌,이성우,신영길,김희창 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.1
A Numerical study was performed for the two-dimensional turbulent stirring flow created by linear motor in a continuous casting system. A k-εturbulent model was applied to solve time-averaged turbulent momentum equations within the computation domain. Four different situations in a stirring system being consisted of two-dimensional slab of 1 m(width) × 0.2 m(height) have been investigated, that is : Model (A) : W =0.1 m and B_0=0.01 tesla, Model (B) : W =0.3 m and B_0=0.01 tesla, Model (C) : W =0.1 m and B_0=0.02 tesla, Model (D) : W =0.3 m and B_0=0.02 tesla, where W is the length of linear motor and B_0 is the magnetic flux applied on the motor-side-surface of the slab. The results shows that the flow characteristics depends mainly on the magnetude of B_0 not on W. The order of the magnitudes of turbulent intensity at four flow situations were almost same. However, the magnitude of turbulent viscosity became much less in case of greater B_0 than in smaller B_0. Therefore it is recommended that the stirrer with greater B_0 should be used to make finer stirring action.
A VSR Chart with Multi-state VSS and 2-state VSI Scheme
이재헌,박창순 한국품질경영학회 2004 품질경영학회지 Vol.32 No.4
Variable sampling interval (VSI) control charts vary the sampling interval according to value of the control statistic while the sample size is fixed. It is known that control charts with 2-state VSI scheme, which uses only two sampling intervals, give good statistical properties. Variable sample size (VSS) control charts vary the sample size according to value of the control statistic while the sampling interval is fixed. In the VSS scheme no optimal results are known for the number of sample sizes. It is also known that the variable sampling rate (VSR) control chart with 2-state VSS and 2-state VSI scheme leads to large improvements in performance over the fixed sampling rate (FSR) chart, but the optimal number of states for sample size is not known. In this paper, the VSR charts with multi-state VSS and 2-state VSI scheme are designed and compared to 2-state VSS and 2-state VSI scheme. The multi-state VSS scheme is considered to achieve an additional improvement by switching from the 2-state VSS scheme. On the other hand, the multi-state VSI scheme is not considered because the 2-state scheme is known to be optimal. The 3-state VSS scheme improves substantially the sensitivity of the chart especially for small and moderate mean shifts.
이재헌,이동선,정성균 서울産業大學校 2005 논문집 Vol.54 No.1
The shot peening process is well known technique for extending the durability of mechanical parts. We can expect the high cost and low fatigue life because the over peening process is applied in the industrial field. In this paper, the improvement of gear productivity was investigated by applying the optimum peening process. The experiment was accomplished for the SCM920 spur gear. Saturation curve and optimum peening condition were obtained by bending fatigue test. Experimental results show that the optimum peening time is between 6 minutes to 10 minutes. The improvement of productivity by optimum peening process was 36% higher than conventional process.
이재헌,이진원,이상렬 대한기계학회 1986 대한기계학회논문집 Vol.10 No.6
본 연구에서는 청정실 내부에 하나의 작업대가 유동을 방해하고 있으며, 출구 공기덕트가 2개이기 때문에 출구의 평균압력조건은 주어지나 출구속도의 경계조건이 간단히 기술되지 않는 청정실내에서 유동을 예측하고자 하였으며, 수치계산상의 구체 적인 방법을 논하였다. 그 결과로서 작업대 위치 및 각 출구에서의 압력조건에 따른 유동장의 형태 및 각 출구에서의 유출유량 비율등을 논하였다. The effect of placing a worktable in a vertical laminar flow clean room is invesgiated by a numerical simulation. The model clean room is assumed to be a rectangular square of 2m*2m, in which a worktable of 0.8m long and 0.1m thick is located at 0.7m above the floor. Major parameters are the horizontal position of the table and the inlet flow velocity. The flow is assumed to be laminar throughout the clean room. Navier-Stokes equations with the pressure terms are directly solved by the SIMPLE algorithm. Boundary conditions at the two exits are given in terms of pressure conditions. The flow pattern, pressure loss due to viscous friction, the ratio of flow rates through each exit and pressure imbalance at the exits are calculated. All of the flow characteristics are seen to vary substantially with the location of the table, but are quite insensitive to the inlet flow velocity(Reynolds number). As an example, the flow rate through each exit can very by as much as 30% depending on the location of the table.