• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.1-11
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• 2022

In this study, an electric resistance dual-spot welding process using a copper electrode inserted in a heating electrode is suggested for the spot welding of AZ31 magnesium sheets. This spot-welding process involves two heating methods for welding at the interfacial zone between the magnesium sheets, one of which is the heating method by thermal conduction from the heating electrode heated by the welding current induced to the steel electrode, and the other heating method uses the electric resistance between the contacted surfaces of the two sheets by the welding current induced to the copper electrode. This welding process includes the welding variables, such as the current induced in the heating electrode and the copper electrode, and the outer diameters of the heating electrode. This is because the heat conducted from the heating electrode can be maintained at a higher temperature in the welding zone, which has a slow cooling effect on the nugget of the melted metal after the welding step. The pressure exerted during the pressing of the magnesium sheets by the heating electrode can be increased around the nugget zone at the spot-welding zone. Thus, it not only reduces the warping effect of the elastoplastic deformation of sheets, but also the corona bond can make it less prone to cracking at the welded zone, thereby reducing the number of nuggets expelled out of the corona bond. In conclusion, it was known that an electric resistance dual spot welding process using the copper electrode inserted in the heating electrode can improve the welding properties in the electric resistance spot welding process of AZ31 magnesium sheets.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.279-280
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• 2007

In this study, it is investigated that the effect of material properties such as various temperature, forming speed and strain rates on formability and forming limits of Mg alloy sheet in square cup deep drawing. Since the sheet metal forming of Mg alloy is perform at elevated temperature, the effect of strain rates related with the forming temperature and forming speed is very important factor for formability and forming limits. Therefore, the investigation for process variables is necessary to improve formability and forming limits. Also, the effects of strain rate and thickness transformation were studied by the experimental and FE analysis using the square cup deep drawing. The temperature, forming speed, and strain rates were investigated. Forming of Mg alloy takes consider into temperature, proper forming speed and strain-rate the formed parts were good without defects fur forming limits.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.614-616
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• 2011

본 연구에서는 유한요소법과 변형률 의존성 연성파괴이론을 이용하여 드로잉 공정에서의 AZ31 마그네슘 합금 판재의 파단 발생을 예측 하였다. 다양한 온도에서의 사각컵 드로잉 실험을 수행하여, 각 온도조건에서의 파단깊이를 측정하였으며, 고온 인장시험을 통해 연성파괴상수를 온도 및 변형률 속도에 의존적인 값으로 표현하고, 실험과 동일하게 모사된 유한요소해석을 수행하였다. 해석결과 얻어진 각 요소의 온도 및 변형률 속도에 따른 연성파괴상수를 이용하여 파단발생을 예측하였으며, 실험결과와 검증하였다.

• Journal of Industrial Technology
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• v.30 no.A
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• pp.49-57
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• 2010

A forming limit diagram (FLD) defines the extent to which specific sheet material can be deformed by drawing, stretching or any combination of those two. To determine the forming limit curve (FLC) accurately, it is necessary to perform the tests under well-organized conditions. In this study, the influence of several geometric or process parameters such as the blank shape and dimensions, strain measuring equipments, test termination time, forming speed and lubricants on the FLC is investigated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.61-62
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• 2011

실리카 나노입자를 분산시킨 기능성 코팅 소재를 개발하였다. 본 기능성 코팅 소재는 마그내슘 판재에 적용하여 내스크래치 및 내부식성을 향상시키기 위한 것이다. 최근 마그네슘 판재는 스마트 폰 및 이동통신 기기의 외장재소재로 각광을 받고 있다. 그러나 표면의 기계적 강도가 약하고, 특히 수분에 의한 부식이 심각하여 사용에 많은 제한을 받고 있다. 본 연구에서는 실리카 나노입자가 분산된 유무기 하이브리드 코팅을 적용하여 기계적 강도 및 내부식성을 향상하고자 하였다. 분산하는 나노입자의 크기를 달리하여 코팅층으로부터 각각 다른 물리적 화학적 특성을 유도할 수 있었다. 각 코팅 층의 특성은 연필경도, 기판 휨 각도, 그리고 electrochemical impedance spectroscopy 등을 이용하여 평가하였고, 최종적으로 휴대폰 신뢰성 평가 기법을 적용하여 상용화 적용성도 평가하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.117-120
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• 2003

Warm deep drawing which is one of the new forming technologies to improve formability of sheet metal is applied to the cylindrical cup drawing of Mg-alloy sheet metal. In experiments the temperature of die and blank holder is varied from room temperature to $300^{\circ}C$, while the punch is cooled by circulation of coolant to increase the fracture strength of workpiece on the punch corner area. Test material chosen for experiments is AZ31 magnesium sheet metal. Teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ratio as well as thickness distributions of drawn cups are investigated and validity of warm deep drawing process is also discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.44-49
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• 2008

The characteristic of magnesium alloy is the most light in utility metal, the effect of electromagnetic wave interception, excellent specific strength and absorptiveness of vibration. Although magnesium alloy with above characteristic is a subject matter which is suitable in world-wide tendency of electrical component frame, sheet magnesium alloy is difficult to process. Therefore, forming analysis of sheet magnesium alloy and applying warm-working to process are indispensable. Among Finite element method, the static implicit finite element method is applied effectively to analyze sheet magnesium alloy stamping process, which include the forming stage. In this study, it was focused on the crack, wrinkling and spring back on sheet magnesium alloy stamping by the static implicit analysis. According to this study, the result of simulation will give engineers good information to access the forming technique on sheet magnesium alloy. And its application is being increased especially in the production of electrical component frame for the cost reduction, saving of defective ratio, and improvement of Productivity.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.385-388
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• 2005

The use of magnesium alloys meets the need of reducing weight of componests(especially in automotive and aerospace industry) keeping unmodified their mechanical properties. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this study, the authors aim to understand the process condition which can lead to a successful improvement in the formability of a magnesium alloy(AZ31). Experiment and simulations of deep drawing were doned at various warm temperature for the blank and tool(holde and die)while the punch was kept at room temperature by cooling wale. in order to confirm that the deep drawing performance of magnesium alloy can be considerably enhanced with using the local heating and cooling technique.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.47-47
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• 2008