• 소성∙가공
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• 제19권1호
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• pp.38-43
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• 2010

Electromagnetic forming (EMF) method is one of high-velocity forming processes, which uses electromagnetic Lorentz force. Advantages of this forming technique are summarized as improvement of formability, reduction in wrinkling, non-contact forming and applications of various forming process. In this study, the EMF apparatus is developed. It is designed to be stored in 10 capacitors connected in parallel, each with a capacitance of $50{\mu}F$ and maximum working voltage of 5kV. The system has capacitance of $500{\mu}F$ and maximum stored energy of 6.25kJ. And EMF experiments are carried out to verify the feasibility of the EMF apparatus, which has enough forming force from the results of EMF experiment. In addition, peak current carrying a forming coil is predicted from theoretical background, and verified the predicted value compared with experimental value using the current measurement equipment. Consequently, EMF apparatus developed in this study can be applied to various EMF researches for commercialization.

• 소성∙가공
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• 제17권1호
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• pp.35-45
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• 2008

Electromagnetic Forming (EMF) technology such as magnetic pulse forming, which is one of the high velocity forming methods, has been used for the joining and forming process in various industry fields. This method could be derived a series of deformation of sheet metal by using a strong magnetic field. In this study, numerical approach by finite element simulation of the electromagnetic forming process was presented. A transient electromagnetic finite element code was used to obtain the numerical model of the time-varying currents that are discharged through the coil in order to obtain the transient magnetic forces. Also, the body forces generated in electromagnetic field were used as the loading condition to analyze deformation of thin sheet metal workpiece using explicit dynamic finite element code. In this study, after finite element analysis for thin sheet metal forming process with free surface configuration was performed, analytical approach for a dimpled shape by using EMF was carried out. Furthermore, the simulated results of the dimpled shape by EMF were compared with that by a conventional solid tool in view of the deformed shape. From the results of finite element analysis, it is confirmed that the EMF process could be applied to thin sheet metal forming.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.387-390
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• 2008

Electromagnetic forming (EMF) technology, which is one of the high speed forming methods, has been used for the forming process in various industry fields. Numerical approach by finite element simulation of the EMF process is presented in this study. The implicit code is used to obtain the numerical model of the time-varying currents that are discharged through the coil in order to obtain the transient magnetic forces. In addition, the body forces generated in the workpiece are used as the loading condition to analyze deformation of thin sheet metal workpiece using explicit code. Numerical approach for a dimpled shape by EMF process is carried out and the simulated results of the dimpled shape by EMF are reviewed in view of the deformed shape and formability evaluation.

• 한국정밀공학회지
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• 제30권7호
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• pp.733-740
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• 2013

The high-velocity electromagnetic forming (EMF) process is based on the Lorentz force and the energy of the magnetic field. The advantages of EMF include improved formability, wrinkle reduction, and non-contact forming. In this study, numerical simulations were conducted to determine the practical parameters for the EMF process. A 2-D axis-symmetric electromagnetic model was used, based on a spiral-type forming coil. In the numerical simulation, an RLC circuit was coupled to the spiral coil to measure various design parameters, such as the system input current and the electromagnetic force. The simulation results show that even though the input peak current levels were at the same level in each case, the forming condition varied due to differences in the frequency of the input current. Thus, the electromagnetic forming force was affected by the input current frequency, which in turn, determined the magnitude of the current density and the magnetic flux density.

• 항공우주시스템공학회지
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• 제12권3호
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• pp.64-69
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• 2018

고속 전자기 성형 (EMF) 과정은 로렌츠 힘과 자기장의 에너지를 기반으로 한다. EMF의 장점은 향상된 성형성, 주름 감소 및 비접촉 성형 등이 있다. 본 연구에서는 전자기 성형을 통한 알루미늄 파이프의 온도에 따른 성형성을 분석하기 위해 전자기-구조 연동해석을 수행하였으며, 온도가 증가함에 따라 전기저항이 커지므로 인해 자속 밀도는 감소하고, 응력-변형률 곡선에서 온도가 높아질수록 유동 응력이 낮아지므로 변형량은 상대적으로 증가함을 확인할 수 있었다.

• 소성∙가공
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• 제23권6호
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• pp.363-368
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• 2014

Electromagnetic forming(EMF) is one of the high-speed forming methods, and has been used to deform metal sheets. The advantages of electromagnetic forming are reduced wrinkling due to non-contact characteristic and fine formability because of the high speed impact. In the current study, we suggest the application of electromagnetic forming to emboss pattern shapes using electromagnetic forces with only one forming coil and one punch. The high impact of the sheet at speeds of 100~300m/s produces significant coining pressure. In the current paper, electromagnetic forming was applied to Al 1100-O sheets; with thickness of 1.27mm and an area of $40mm{\times}40mm$. Using a single spiral coil, totally different types of patterns were created. Four different patterns were successfully produced on the aluminum sheet. The length and depth of the patterns were measured by three-dimensional scanning. Comparisons to the die shape showed good agreement. The test results confirm that emboss pattern forming by EMF using a single die can be used to replace the costly conventional method.

• 소성∙가공
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• 제28권3호
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• pp.159-166
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• 2019

Electromagnetic forming (EMF) simulations consider 3-dimensionally coupled electromagnetic-mechanical phenomenon using LS-DYNA, therefore the calculation cost is normally expensive. In this study, a sensitivity analysis in regard to the simulation variables affecting the calculation time was carried out. The EMF experiments were conducted to form an elliptically protruding shape on a high-strength steel sheet, and it was predicted using LS-DYNA simulation. In this particular EMF simulation case, the effect of several simulation variables, viz., element size, contact condition, EM-time step interval, and re-calculation number of the EM matrices, on the shape of elliptical protrusion and the total calculation time was analyzed. As a result, reasonable values of the simulation variables between the simulation precision and calculation time were proposed, and the EMF experiments with respect to the charging voltages were successfully predicted.

• 소성∙가공
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• 제23권7호
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• pp.431-438
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• 2014

For electromagnetic forming(EMF) the most important feature is a forming coil which creates the electromagnetic force(Lorentz force), using current density and a magnetic field. Most previous papers have concentrated on the final configuration of the blank or the efficiency of EMF process. Studies focused on the design parameters affected by the forming coil performance have not been conducted. In order to design a suitable forming coil for an object, the current study uses LS-DYNA EM-Module to not only optimize the coil but also to examine the effect of coil performance. By this method a suitable forming coil was made and tested to determine whether or not good formability was achieved in a free bulge test Numerical analysis was also used. The workpiece was Al 1100-O with a thickness of 1.27mm and the coil was made from copper CW004A, which has good electrical conductivity and is suitable for electrical components.

• 소성∙가공
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• 제25권4호
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• pp.261-267
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• 2016

High-speed forming process is the forming technology that deforms the blank in a very short time, with the strain rate of the blank above 1000 s⁻¹. Among many high-speed forming processes, electromagnetic forming (EMF) employs the Lorentz force when deforms the blank. Because of the high strain rate, the formability of the blank can be improved. However, when the blank is formed into rather complex shapes, it is bounced from the die and the wrinkles are generated. Therefore, electrohydraulic forming (EHF) is suggested in this study to reduce the bouncing problem of the blank. EHF is a high-speed forming that uses high voltage discharge in liquid. The shockwave resulting from the electric discharge propagates to the blank and it deforms the blank into the die. In this study, two high-speed forming processes, EMF and EHF were compared numerically with trapezoidal middle block die. This comparison showed that EMF cannot deform the blank into the die because of the bouncing, while EHF can overcome the bouncing problem and deform the blank into the die shape successfully.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.313-317
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• 2009

Electromagnetic forming(EMF) is a high-velocity forming process which uses electromagnetic Lorentz force. Advantages of this forming technique are improved formability, reduction in wrinkling, non-contact forming and applications of various forming process. But the application of electromagnetic forming technique is still limited in industry. Thus for continuous research and development of technique based on experiments, develop the forming equipment and carry out the forming experiments for validation of forming equipment.