• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.4
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• pp.56-61
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• 2000

Cognition and control of grinding trouble occurring during the grinding process are classified into a quantitative knowledge which depends on experimental data and qualitative knowledge which relies on skilful engineers. Grinding operations include a large number of functional parameters, since there are several ways of coping with grinding trouble. One is the qualitative method which depends on empirical knowledge utilizing the skilful experts from the workship, the other is the quantitative method which utilizes the experimental data obtained by a sensor. But, they are all difficult to accomplish from the grinding trouble-shooting system. The reason is that grinding troubles are now easily controlled in the quantitative method, and therefore, trouble-shooting has mainly relied on the knowledge of skilful engineers. Thus, there is an important issue of how a grinding trouble-shooting system can be designed and what knowledge is utilized among the large amount of grinding trouble information. In this paper, basic strategy to develop the grinding database of rule-based model, which is strongly depended upon experience and intuition , is described.

• Composites Research
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• v.30 no.3
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• pp.193-201
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• 2017

Molecular dynamics simulation and the Mori-Tanaka micromechanics study are performed to investigate the effect of the covalent grafting between CNT and polyester on the mechanical behavior and load transfer of nanocomposites. The transversely isotropic stress-strain curves are determined through the tension and shear simulations according to the covalent grafting. Also, isotropic properties of randomly dispersed nanocomposites are obtained by orientation averaging the transversely isotropic stiffness matrix. By addressing the grafting, the transverse Young's modulus and shear moduli of the nanocomposites are improved, while the longitudinal Young's modulus decreases due to the degradation of the grafted CNT.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.62-68
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• 2012

Geometry of a screw fabricated by a turning process determined by the shape of the tool, feed rate of the tool and rotation speed of the spindle. Therefore, computing the exact geometry of the screw is very important to perform a simulation on machining or an evaluation of the workpice quality. In this paper, a new mathematical geometry model of the 3 dimensional screw is fabricated by turning process introduced for the exact geometry computation. Becasue model has a parametric formulation, it is easy to process for a CAD geometry or apply for a machining simulation. Also, it can be applied to process planning because it gives precise machined geometry on whole the 3 dimensional surface of the screw. This paper introduces a new parametric model of a geometry for screw fabricated by turning process. As an application, a simulation software for the 3 dimensional screw surface is developed and evaluated for several manufacturing parameters.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.604-607
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• 2005

In the electro-discharge machining the machining performance is closely related to the characteristics of discharge which can be identified from electrical behavior in gap between workpiece and electrode. Therefore, the accurate prediction of electrical behavior in electro-discharge machining (EDM) is useful to process control and optimization. However, any simulation model fur prediction of electrical behavior in EDM process has never been reported until now. In this study, a simulation model is developed to analyze the electrical behavior of electro-discharge plasma which significantly influences electrical behavior in EDM process. For the purpose of this the fundamentals of electro-discharge mechanism such as inception, propagation, formation of plasma channel and termination are investigated to accurately predict the cycle of discharge plasma in EDM. As a result, a mathematical model of electro-discharge plasma is constructed with considering the fundamentals of electro-discharge plasma. Consequently, it is demonstrated that the developed model can predict the electrical behavior of plasma such as electron density in various conditions.

• Proceedings of the KIEE Conference
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• summer
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• pp.375-377
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• 2004

22.9kV급 가공배전선에서의 뇌격현상은 직접측정이 어렵기 때문에 지금까지 절연협조수준의 도출은 수치적인 모의해석과정에서 얻어진 과전압강도를 근거로 하고 있다. 대표적인 모델에 대해서 만이라도 실측자료를 확보할 수 있다면 해석과정의 정확도를 높이는 중요한 전기가 될 수 있다. 이러한 가공배전선로의 뇌격현상을 측정하기 위한 상용설비를 이용한 경제적 측정시스템을 구성하였다. 접지회로에서 발생하는 과전압으로 인한 인명뿐 아니라 계측설비의 안전성도 확보하고 과 경제성확보를 위하여 전주 중간에 장시간용 UPS 및 파형측정설비를 2중 차폐함 안에 넣어 1점 접지상태가 되도록 고정하고 측정point에 HV divider 및 로고스키코일을 설치하여 한 지점에서의 측정회로를 구성하였다. 전체적으로 뇌격전류 주입 위치에서부터 3지점을 선정하여 측정설비를 설치하고 경제적인 Rs485 multi-drop 회로를 구성하여 통신망을 확보하였다. 직렬통신망에는 뇌격시험 시 발생하는 과전압에 대한 보호회로로서 간단한 수동식 개폐회로를 구성하였다. 측정파형을 전체적으로 전송받는 속도가 약간 늦기는 하나 간단한 data acquisition program을 사용하여 전체 측정회로를 가동시킬 수 있었다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.9
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• pp.36-43
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• 2019

Turning, a main machining process, is a widespread process in metal cutting industries. Many researchers have investigated the effects of process parameters on the machining process. In the turning process, input variables including cutting speed, feed, and depth of cut are generally used. Surface roughness and electric current consumption are used as output variables in this study. We construct a simulation model for the turning process using a neural network, which predicts the output values based on input values. In the neural network, obtaining the appropriate set of weights, which is called training, is crucial. In general, back propagation (BP) is widely used for training. In this study, techniques such as ant colony optimization (ACO) and particle swarm optimization (PSO) as well as BP were used to obtain the weights in the neural network. Particularly, two combined techniques of ACO_BP and PSO_BP were utilized for training the neural network. Finally, the performances of the two techniques are compared with each other.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.371-377
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• 2002

근래 정보 시스템의 흐름은 생산 분야의 관리뿐만 아니라, 고객과의 관계를 중시하는 CRM(Costumer Relation Management)과 공급업체와의 협업 관계를 유지하는 eProcurement시스템에 초점을 맞추고 있다. 즉, 기존에는 단위 생산 시스템의 관리에 중점을 두었지만 최근에는 그 외부 요소들에 대한 관리의 중요성을 인식하게 되었고 이를 통징하여 공급망 관리(SCM Supply Chain Management)라고 한다. 본 논문에서는 공급망 관리에서 필요한 생산 계획수립 문제에 대해서 살펴본다. 특히 고객과의 관계에서 중요한 기능인 납기 회답을 지원하는 생산 계획 수립의 실행 주기에 대해서 살펴본다. 첫째, 단위 생산 시스템에서 사용하는 작업지시(Work Order)와 구매 지시(Purchase Order)를 생성하는 정규계획 모델에 대해서 설명한다. 정규계획 모델에서 필요로 하는 정적 정보와 동적 정보의 수집 및 계획의 실행을 담당하는 ERP 시스템과의 관계에 대해서 정의하고 정규계획 모델의 운영 주기를 정의한다. 둘째, 정규계획 모델과 상호 협조하면서 납기 회답을 지원하는 납기회답 모델의 설계에 대해서 살펴본다. 정규계획 모델과 달라지는 입력 부분의 정의와 정규계획 모델과의 상호 관계를 정의한다. 다음으로, 정해진 납기를 지키기 위해서 정규계획 모델에서 고려래야 하는 요소에 대해서 알아본다. 가장 중요한 것으로 작업 부하와 생산 용량을 고려한 계획 일자(PST)와 고객 납기와 제조 공정 LT를 고려한 계획 일자(LPST)중 최소값을 원자재의 납기 일자로 사용하는 것을 제안한다. 동시에 신규 구매 지시 계획을 생성하기보다는 기존에 발생된 구매 지시의 우선적 사용과 기존 구매 지시의 납기 일자를 고객 납기에 가장 잘 맞출 수 있도록 변경하는 방안을 제시한다. 이렇게 함으로써 최대한 고객 납기를 만족하도록 계획을 수립할 수 있게 된다. 본 논문에서 제시하는 계획 모델을 사용함으로써 고객 주문에 대한 대응력을 높일 수 있고, 계획의 투명성으로 인한 전체 공급망의Bullwhip effect를 감소시킬 수 있는 장점이 있다. 동시에 이것은 향후 e-Business 시스템 구축을 위한 기본 인프라 역할을 수행할 수 있게 된다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.209-212
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• 2007

Rubber compounds have high viscoelastic property. One of the viscoelastic behaviors during profile extrusion is the swelling of extrudate. In this study, die swell of rubber compounds at the capillary die have been investigated through an experiment and computer simulation. They have been performed using fluidity tester in experiment and commercial CFD code, Polyflow in computer simulation. Die swell of rubber compounds for relaxation time at several modes under same conditions with the experiment were predicted using non-linear differential viscoelastic model, Phan-Thien-Tanner (PTT) model. The simulation was analyzed compared with the experiment. Viscoelastic behaviors for pressure, velocity and shear rate distribution were analyzed at the capillary die. It is concluded that the PTT model successfully represented the amount of the optimal die swell of rubber compounds for relaxation time at different modes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.42-45
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• 2008

Recently, aluminum is widely used to reduce the vehicle weight. Aluminum curved extruded products are used for the design of automotive frame parts. This study focuses on the determination of process condition fur automotive bumper beam with various curvatures. In this study, a curvature prediction model has been proposed considering the geometric relationship and the characteristic of the curvature extrusion equipment. Using the proposed model and FE analysis, the appropriated process condition was determined to produce the bumper beam. Finally, curvature extrusion experiment was carried out to verify the effectiveness of the proposed curvature prediction model and the process condition.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.259-262
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• 2009

The influence of pre-strain in low-cycle fatigue behavior of Fe-18Mn-0.05Al-0.6C TWIP steel was studied by conducting axial strain-controlled tests. As-received plates were deformed by rolling with reduction ratios of 10 and 30%, respectively. A triangular waveform with a constant frequency of 1 Hz was employed for low cycle fatigue test at the strain amplitudes in the range of ${\pm}0.4{\sim}{\pm}0.6$ pct. The results showed that low-cycle fatigue life was strongly dependent on the amount of pre-strain as well as the strain amplitude. Increasing the amount of prestrain, the number of reversals to failure was significantly decreased at high strain amplitudes, but the effect was negilgible at low strain amplitudes. A new model for predicting fatigue life of pre-strained body has been devised adding a correction term of ${\Delta}E_{pre-strain}$ to the energy-based fatigue damage parameter.