• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.377-380
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• 2005

In this study, the experiments of warm deep drawing were done with heated die, and with heated die and cooled punch in order to investigate the formability of ZA31 magnesium sheet alloy of warm deep drawing. For this, warm deep drawing experiments were executed under various temperature, punch velocity and blankholder force. The results of warm deep drawing with heated die showed that fracture occurred punch part at punch velocity of 75mm/min and punch stroke of 10mm under temperature of $100^{\circ}C\~250^{\circ}C$, but did not occure under temperature of $275^{\circ}C\~400^{\circ}C$. And fracture at punch stroke of 25mm did not occurre at punch part under punch velocity of 30mm/min and $250^{\circ}C$, but occured under punch velocity of 75 and 125 mm/min. Also the results of warm deep drawing with heated die and cooled punch showed that the temperature happening maximum height under punch velocity of 10-100mm/min was $225-250^{\circ}C$. And necking occurred at punch shoulder under $20\~150^{\circ}C$, but at die wall under $200\~300^{\circ}C$.

• 소성∙가공
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• 제15권2호
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• pp.148-152
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• 2006

In this study, the experiments of warm deep drawing were done with heated die, and with heated die, and blankholder, and cooled punch in order to investigate the formability of AZ31 magnesium alloy sheet in warm deep drawing. For this, warm deep drawing experiments were executed under various temperatures and punch velocities. The results of warm deep drawing with heated die showed that fracture occurred around the punch part at punch velocity of 75mm/min and punch stroke of 10mm under temperature range of 373-523K, but did not occur under temperature range of 548-673K even punch stroke of 25mm. And fracture at the punch stroke of 25mm and the temperature of 523K did not occur under the punch velocity of 30mm/min, but occurred under punch velocity of 75 and 125mm/min. Also warm deep drawing with heated die and blankholder, and cooled punch showed that the temperature range happening maximum height under punch velocity of 10-100mm/min was around 498-523K. Finally, with heating and cooling technique necking of AZ31 magnesium alloy occurred at punch shoulder part under the temperature range of 293-423K, but at die wall part under the temperature range of 473-573K.

• 대한기계학회논문집A
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• 제22권2호
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• pp.380-390
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• 1998

In the present work a finite element formulation using dynamic explicit time integration scheme is used for numerical analysis of auto-body panel stamping processes. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and direct trial-and-error method. In this work, for economic analysis the faster punch velocity and the mass scaling method are introduced. To investigate the effects of punch velocity and mass scaling, the various values of punch velocity and the various mass scalings are used for numerical analysis. Computations are carried out for analysis of complicated auto-body panel stamping processes such as forming of an oil pan and a fuel tank.

• 한국운동역학회지
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• 제17권4호
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• pp.201-208
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• 2007

The purpose of this study is to compare 4 different body punch types(type 1: a punch using a shoulder, type 2: a punch using a waist, type 3: a punch using lower extremities, and type 4: a punch with elbows by your side at chest level) in horseback-riding stance and establish suitable teaching theory and method, which would be a useful reference to Taekwondo instructors on the spot(in Taekwondo dojangs all around Korea). Five exhibition players from Korean national Taekwondo exhibition team participated in this study. Each participant was asked to perform the four different types of punches and their kinematic and kinetic data were recorded with 7 vicon cameras(125Hz) and two force plates(AMTI, 1200Hz). We analyzed displacement, time, resultant center of body mass trajectory, velocity, trunk angular velocity, and ground reaction force(GRF) from each body segment in body punch and the result. I performed 1-way ANOVA(RM) for average values of each player after standardization and statistical significance was set as p<.05. was as the following ; First, they showed a tendency to take the body punch posture with the biggest motion at a shoulder and on descending order a waist and a knee. Second, a mean time for each body punch on ascending order 0.46sec. for type 2, 0.49sec for type 3, 0.50sec. for type 4, and 0.56sec. for type 1. Third, a mean resultant center of body mass trajectory for each body punch the longest 4.07cm for type 3 and the shortest 2.458cm for type 1. Fourth, a mean of maximal velocity of a fist strike was the fastest 5.99m/s for type 3, 5.93m/s for type 4, 5.67m/s for type 2, and 5.01m/s for type 1 on the descending order. Fifth, a mean of maximal trunk angular velocity of the fastest 495.6deg./sec. for type 4 and 337.7deg./sec. for type 1 on the descending order. Sixth, strongest value was type 3, 2 for anterior-posterior ground reaction force(left -54.89N, right 60.58N), type 4 for medial-lateral GRF(left 83.59N, right -80.12N), and type 3 for vertical GRF(left 341.79N, right 426.11N).

• 소성∙가공
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• 제18권7호
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• pp.565-571
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• 2009

This paper is concerned with the analysis on the surface stress profiles of perfectly plastic material in backward extrusion process. Due to heavy surface expansion appeared usually in the backward extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the analyses have focused to reveal the surface conditions at the contact boundary for various punch shapes in terms of surface expansion, contact pressure, and relative movement between punch and workpiece which consists of sliding velocity and distance, respectively. Punch geometries adopted in the analysis include concave, hemispherical, pointed and ICFG recommended shapes. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward extrusion process under different punch geometries. The simulation results are summarized in terms of surface expansion, contact pressure, sliding velocity and sliding distance at different reduction in height, deformation patterns, and load-stroke relationship, respectively.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1497-1502
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• 2013

수소를 친환경적 에너지원으로 사용하는 경우, 수소 압력용기용 강재의 수소취화 평가 및 안전성에 대한 신뢰성이 확보되어야 한다. 본 연구에서는, in-situ SP 시험법을 적용하여 수소 저장용기로 사용이 검토되고 있는 SA372 강재의 가스 수소취화 거동을 평가하였다. 표면가공 조건을 달리한 시험편을 사용하여 대기압, 고압 수소가스 압력하에서 펀치속도를 달리한 SP 시험을 통해 가스수소 취화 거동을 조사하였다. 그 결과, SA372 강은 가스수소 압력하에서 현저한 수소취화 거동을 나타내었다. 이때 펀치속도에 따른 영향도 명확하게 나타나, 펀치속도가 낮을수록 현저한 수소취화를 나타내 낮은 SP 에너지 값을 나타내었다. 또한 SP 시험 후 파면양상 관찰결과도 펀치속도에 따른 수소취화 거동을 명확하게 나타내었다. 본 가압수소 시험조건에서는 시험편 표면조건의 영향은 명확하게 볼 수 없었다.

• 한국군사과학기술학회지
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• 제6권1호
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• pp.68-80
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• 2003

The backward extrusion process of titanium alloy with large length to diameter ratio was simulated for different punch and die shape. The process variables such as initial billet shape, interface friction, contacting time and punch velocity were investigated and compared with experimental results. To make more effectively titanium alloy cup shape forging products with vertical wall, a modified die design which can reduce forging load, prevent sticking with punch and minimize material loss was suggested.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.761-765
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• 1996

This paper describes the forging of circular tooth profiled gears as a series of development of simulator for non-axisymmetric parts that being used at the pump pulley, timing belt pulley etc. in automobiles. The half pitch of gear is divided into 6 deformation regious and kinematically admissible velocity fields for those regions are proposed. The neutral surface is introduced torepresent inner flow of material during forging operation with flat punch and, for each step, it is assumed as a circle. The upper bound solutions obtained from the suggested kinematically admissible velocity fields are in good agreement with experimental results and they are useful to predict the capacity of forging press for forging of circular gears.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.234-237
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• 2007

Deep drawing of magnesium alloy sheet is conducted at elevated temperatures($200{\sim}300^{\circ}C$) to improve the press formability because of low formability at room temperature. Then magnesium alloy sheet formability is known to be very sensitive to the strain rate. In this paper, we conducted warm deep drawing tests of magnesium alloy AZ31 sheet for various punch velocities. We examined the forming velocity effect on the deep drawing formability and the correlation with the tensile test result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.144-149
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• 1996

In this paper, the clamping type forging of helical gears has been investigated. Clamping type forging is an operation in which the product is constrained to extrude sideways through an orifice in the container wall. Punch is cylindrical shaped. The punch compresses a cylindrical billet placed in a die insert. As a consequence the material flows in a direction perpendicular to that of punch movement. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle, friction factor and initial height of billet on the forging of helical gears.