• 소성∙가공
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• 제4권4호
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• pp.345-352
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• 1995

Warm deep drawing for optimum forming conditions to give the maximum drawing depth is investigated and compared with the results from experiments performed at room temperature. Experiments which draw square cups of STS 304 stainless steel sheet under the constant lubrication condition of teflon film are made both in a crank and hydraulic press for two kinds of specimens. The maximum drawing depth at warm forming condition reaches 1.4 times the drawing depth at room temperature in a crank press, whereas 1.6 times in a hydraulic press, and also more uniform distribution of thickness in case of warm deep drawn cup is observed. The effects of other factors on formability, such as forming temperature, speed of press and cooling of punch are examined and discussed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.178-185
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• 1995

Warm deep drawing for optimum forming conditions to give the maximum drawing depth is investigated and compared with the results at room temperature. Experiments which draw square cups of STS 304 stainless steel sheet under the constant lubrication condition of teflon film made both in a crank and hydrqulic press for two kinds of specimens . The maximum drawing depth at warm forming condition reaches 1.4 times the drawing depth at room temperature in a crank press, whereas 1.6 times in a hydrqulic press, and also more uniform distribution of thickness in case of warm deep drawn cup is observed. The effects of other factors on formability , such as forming temperature, speed of press and cooling of punch are examinnied and discussed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.337-340
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• 2008

Magnesium alloy is expected to be widely used for mobile electronic appliances as well as automobile parts for its lightweight and EMI-shielding characteristics. In the present investigation, a Note-PC upper case made of magnesium alloy AZ31 sheet was developed by using the press forming technology at elevated temperature. Considering the press forming process and the formability of magnesium alloy sheet, the case shape and the press die was designed. The optimum forming condition was experimentally examined. Then the as-received magnesium alloy sheet was press-formed into the designed case shape under the optimum forming condition.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1994년도 박판성형기술의 진보
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• pp.69-78
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• 1994

A rotating disk is introduced to be applied to the deep drawing press. Several characteristics are summarized to see the basics of deep drawing of sheet metal in terms of load-stroke relationship and formability. Many conventional drawing presses, which are mostly link-type presses, are also shown to be compared with the rotating disk-type press. Performances of the new press are kinematically analyzed it terms of load-main gear angle relationship, stroke-gear angle relationship, and slide velocity-gear angle relationship and they are compared with those of conventional types', e. g. crank press and so on. The comparison show kinematically better performance of rotating disk-type press than that of conventional ones. Also, the new press are proven to be one of the best press for mass production in terms of cycle time. Applicability of the rotating disk press to deep drawing and cold forging work is introduced. The new press is described in terms of economy such that the cost of new press would be much lower than those of conventional types'.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1312-1316
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• 2007

Strip casted and rolled magnesium sheet is become exiting material for car manufacturer, due to its better formability and specific strength compare with conventional extruded sheet. TWB technology was attractive for car body designer, because it saves the weight of the car without strength loss. In this study, the laser welding performance of magnesium sheet was investigated for Mg TWB panel manufacturing. The material was strip casted and rolled magnesium alloy sheet contains 3 wt% Al and 1 wt% Zn (AZ31). Lamp pumped Nd:YAG laser of 2kW was used and its laser light was delivered by optical fiber of 0.6mm core diameter to material surface with focusing optics of 200mm focal length for TWB welding. The microstructure of weld bead was investigated to check internal defects such as inclusion, porosity and cracks. Also mechanical properties and formability were evaluated for press forming of car body. For the results, there was no crack but inclusion or porosity on weld at some conditions.The tensile strength of weld was over 95% of base metal. Inner and outer panel of engine hood were press formed and assembled at elevated temperature.

• 소성∙가공
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• 제15권3호
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• pp.232-240
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• 2006

Magnesium alloys are expected to be widely used fur the parts of structural and electronic appliances due to their lightweight and EMI shielding characteristics. While the die casting has been mainly used to manufacture the parts from the magnesium alloys, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. However, the magnesium alloy has low formability at room temperature and therefore, in many cases, forming at elevated temperatures is necessary to obtain the required material flow without failure. In the present study, square cup deep drawing tests using the magnesium alloy AZ31 sheet were experimentally conducted at various elevated temperatures as well as room temperature, and the corresponding finite-element simulations, which calculated the damage evolution based on the Oyane's criterion, were conducted using the stress-strain relations from the tensile tests at various temperatures. The formability predictability by the finite-element analysis was investigated by comparing the predicted damage distributions over the deformed AZ31 sheet at elevated temperatures with the corresponding experimental deformations with failures.

• 대한기계학회논문집A
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• 제37권4호
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• pp.529-535
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• 2013

알루미늄 확장 금속망 심재와 스테인리스강 면재를 에폭시 수지로 접합하여 제조되는 새로운 박판샌드위치 판재의 제조방법을 제시하고 이의 굽힘 거동을 조사하였다. 강도 및 강성도에 대한 이론해를 제시하고 실험을 통하여 프레스 성형성과 굽힘강도 증대효과 등을 평가하였다. 제시된 제조방법과 재료조합에서 삼점굽힘 하중 작용 시 면재-심재 접착부 분리 현상보다 면재의 항복이 훨씬 조기에 발생하여 본 샌드위치 판재의 우수성을 확인하였다. 샌드위치 판재의 강성도 및 면재 항복이 발생하는 하중과 접착부 분리 하중 등에 대하여 유도된 이론식이 실험 결과와 비교적 잘 일치하였다. 동일한 무게를 갖는 균질 판재와 비교하여 강도와 강성도면에서 월등하고 프레스 성형성도 우수할 것으로 평가되었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.149-153
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• 2008

Since magnesium alloy sheets have been employed in industrial field which requires the light weight and thin engineering components, most of researches have been focused on the formability of magnesium ahoy sheet. In warm press forming of magnesium alloy sheet, it is important to control the sheet temperature by heating the sheet in closed die. When forming a commercial AZ31 magnesium alloy sheets which are 0.5mm and 1.0mm thick, respectively, time arriving at target temperature and temperature variation in magnesium alloy sheet have been investigated. Sheet metals were mostly formed in simple shapes such as circular or rectangular. Few studies about forming of complex shapes were reported. Thus, the formability of magnesium alloy sheet for complex shapes is investigated. The process variable for a double sink shape deep drawing with circular and rectangular shape was investigated by varying temperature, velocities, and clearances. Accordingly, temperature, velocities, and clearances suitable for forming were suggested through investigating the thickness variation of the product.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 추계학술대회 논문집
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• pp.186-189
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• 2008

The flex plate, an automotive part which mounts to the automotive engine to transfer torque to transmission, should have considerable hardness and shape accuracy. As a way to produce the flex plate, the hot press forming technology which takes advantages of high formability at elevated temperature, enhanced strength and shape stability was introduced. Therefore, as one of major process parameters the heat treatment condition should be determined to obtain appropriate hardness in the range of manufacturer's specifications. In this study, two heat treatments, austempering and quenching and tempering (QT), were compared as feasible conditions fur the hot press forming of high-carbon tool steel and the hardness and toughness after heat treatments were evaluated. The study showed that both heat treatments resulted in improved hardness but only quenching and tempering showed practicable range of toughness.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1355-1360
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• 2007

The use of high strength steels are gradually increasing to reduce the weight of automobile to improve the environmental problems and collision safety. To encounter the traditional disadvantages of high strength steels like as a poor formability and high springback, hot press forming has been developed. By this method, the strength of steel sheet is increased about three times of original one through die quenching process. In order to the design of hot press forming tools by using numerical simulation, the knowledge of mechanical and microstructural characteristics are required. This study show the mechanical and microstructural characteristics of a high strength boron-alloyed steel according to the various quenching conditions.