• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.181-186
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• 2002

Laser welding application for car body manufacturing has many advantages in the stiffness and the lightness of vehicle, the productivity of assembly line, and the degree of freedom in design. This presentation will express the innovation of car body manufacturing including parameter optimization, process modeling, and system integration. In this application the investment for systems was cut down dramatically by real time switching over the laser path between two welding stations. Points of technical discussion are as follows: optimization of parameters such as laser power, robot speed and trajectory, compact and useful design of jig & fixture to assure welding quality for 3 sheet-layer zinc-coated steel, system integration between 4kW Nd:YAG laser device and the other systems, on-line real time welding quality monitoring system, perfect safety standards for high power laser, minimization of consumption costs such as arc lamp, protective glass for optic, etc. Laser welding has found a place on Hyundai's production plant in conjunction with the startup of mass production of new sports car, and this production system is the result of a collaboration of its engineers. Outer side sheets are joined to inner side sheets by 122 stitch welds totally. And the length is about 2.4meter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.887.1_888.1
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• 2009

This paper proposes a core loss analysis method to obtain high accuracy prediction by using Multi-curve representing magnetic properties of a electrical steel in Finite Element Analysis (FEA). Generally, the magnetic prosperities of the electrical steel are measured by Epstein Method based on the international standards that are not good sufficient to predict motor performances. The method only aims to grade products in steel companies The magnetic properties of actual stator core is highly different to those given by steel companies due to the fact that stacking effect, shearing stress, nature anisotropy of electrical steels are not taken into account. In this paper, the magnetic properties are variously measured by three measuring devices, and then the several BH curves and BW curves obtained are used to analyze the core loss of a IPM. The BH curve in the high magnetic field are extrapolated using the mathematical formulation with the maximum saturation magnetic polarization measured

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1993년도 제45차 추계 학술대회 연제집
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• pp.97-98
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• 1993

• 산업경영시스템학회지
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• 제44권4호
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• pp.12-22
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• 2021

This article suggests the machine learning model, i.e., classifier, for predicting the production quality of free-machining 303-series stainless steel(STS303) small rolling wire rods according to the operating condition of the manufacturing process. For the development of the classifier, manufacturing data for 37 operating variables were collected from the manufacturing execution system(MES) of Company S, and the 12 types of derived variables were generated based on literature review and interviews with field experts. This research was performed with data preprocessing, exploratory data analysis, feature selection, machine learning modeling, and the evaluation of alternative models. In the preprocessing stage, missing values and outliers are removed, and oversampling using SMOTE(Synthetic oversampling technique) to resolve data imbalance. Features are selected by variable importance of LASSO(Least absolute shrinkage and selection operator) regression, extreme gradient boosting(XGBoost), and random forest models. Finally, logistic regression, support vector machine(SVM), random forest, and XGBoost are developed as a classifier to predict the adequate or defective products with new operating conditions. The optimal hyper-parameters for each model are investigated by the grid search and random search methods based on k-fold cross-validation. As a result of the experiment, XGBoost showed relatively high predictive performance compared to other models with an accuracy of 0.9929, specificity of 0.9372, F₁-score of 0.9963, and logarithmic loss of 0.0209. The classifier developed in this study is expected to improve productivity by enabling effective management of the manufacturing process for the STS303 small rolling wire rods.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.960-964
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• 2005

Digital Virtual Manufacturing is a technology to facilitate effective product developments and agile productions by digital models representing the physical and logical schema and the behavior of real manufacturing systems including products, process, manufacturing resources and plants. A digital virtual factory as a well-designed and integrated environment is essential for successful applications of this technology. In this research, we constructed a sophisticated digital virtual factory of the shipbuilding company's section steel shop by 3-D CAD and virtual manufacturing simulation. This digital virtual factory can be applied for diverse engineering activities in design, manufacturing and control of the real factory.

• 국제지역연구
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• 제22권4호
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• pp.77-98
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• 2018

본 논문의 목적은 제조업, 특히 철강기업의 공급망 경쟁력 확보를 위한 최적의 메커니즘 사례를 연구함으로서 그 시사점을 찾고자 하는 것이다. 이를 위해 본 논문에서는 국내 대표 글로벌 철강그룹의 계열사를 대상으로 그 사례를 살펴보았다. 지금까지의 기업 전략연구는 주로 대형 그룹사의 모기업을 중심으로 이루어져 왔으나, 이번에는 대그룹 계열사에 대한 전략적 한계점과 특성을 고려하여 ser-M기반에서 공급망관리 메커니즘을 다루도록 하며, 이를 통해 글로벌 철강업체 및 대기업 계열사에 적절한 메커니즘을 탐색해보고자 한다. 연구결과, 대기업 그룹의 계열사는 그룹 모기업의 필요에 의해 건립되는 경우가 많아 모기업(S) 중심의 메커니즘이 작동되기 쉽다. 따라서 계열사 입장에서 통제 가능한 내부 자원(R)을 최대한 활용하는 메커니즘이 적합한 것으로 나타났다. 본 논문의 ser-M기반 공급망 메커니즘 연구는 글로벌 철강 제조업 공급망 사례를 중심으로 메커니즘을 살펴보았다는데 의미가 있으며, 또한 국내 대표그룹 계열사에 대한 사례연구란 점에서 그 의의를 찾을 수 있다.

• 한국추진공학회지
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• 제25권5호
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• pp.53-64
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• 2021

SpaceX사는 Falcon 9으로 발사체 비용을 혁신적으로 낮추었으며 로켓의 1단 재사용을 실용화하였다. 현재는 완전 재사용이 가능하고 탑재량이 가장 큰 Starship 시스템을 개발 중이며 이로 인해 더욱 저렴한 비용의 발사와 임무의 다양화가 가능하다. 이를 위해 최초로 메탄 연료를 사용하는 전유동 다단 연소 싸이클을 사용하는 Raptor 엔진을 완성하였다. 그리고 완전 재사용을 위해 스테인리스강 탱크, 하강 중 배면낙하 및 역추진과 같은 거의 사용되지 않는 기술들을 함께 적용하여 다수의 시제기를 제작 및 시험하고 있다. 여기서는 Starship 시스템의 제원, 임무, 설계 특징에 대해 알아보았다. 또한 Raptor 엔진과 매우 빠르게 제작된 초기 13 기의 Starship 시제기 개발 과정에 대해서도 알아보았다.

• Journal of Welding and Joining
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• 제22권6호
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• pp.30-35
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• 2004

Laser welding is obviously an attractive method to join small, thin parts such as small stainless steel tubes, but it is very sensitive to the joint clearance and tolerance, and this makes laser welding difficult to obtain consistent welding qualities over time. Recently, Plasma Augmented Laser Welding(PALW) is being developed to solve these problems. In this study, plasma arc welding(PAW) was introduced to join conventional V-grooved butt joint of thin stainless steel strips using single laser heat source in manufacturing small stainless steel tubes. The effect of the welding speed enhancement is investigated by the experiments. Effects of welding directions, distance between the heat sources and intensity of arc heat source on the optimal welding speed was investigated. Through this research, it was confirmed that PALW process has higher welding speed and robustness than laser welding process.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.103-109
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• 2014

This paper represents the s-cam manufacturing process with the high-carbon steel like S45C using laser welding system. Laser welding of the high-carbon steel is generally difficult because of hardening of the weld zone. Also, existing s-cam manufacturing process, electric resistance welding system, have some problems like increase of production and development cost. To solve those problems, we are introduced the laser welding system with the pre-heating system for precision welding of s-cam with separated shaft and cam part. S-cam manufactured with optimum laser welding conditions is verified the performance like tensile strength, torsional strength and fatigue test. Strength and fatigue test results are described.

• 한국자동차공학회논문집
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• 제18권2호
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• pp.61-66
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• 2010

A virtual manufacturing system that is composed of JMatPro, a material modeler and $DEFORM^{TM}$-HT, a finite element package is applied to the hot press forming process: high temperature material properties for each phase such as flow stress, elastic modulus, Poisson's ratio, thermal expansion coefficient, in addition to TTT curve are predicted by JMatPro and taken into $DEFORM^{TM}$-HT to predict the material behavior considering phase transformation and heat transfer simultaneously. In order to verify the accuracy of computation, the residual stress and the springback were compared with the experimental measurements. Both the predicted and measured principal residual stresses and amount of springback were in good agreement. It was also found that the residual stresses generated from hot press forming are not negligible as it has been generally assumed, although the springback deformation is quite small.