• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2000.04a
• /
• pp.48-48
• /
• 2000

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 1997.10a
• /
• pp.39-39
• /
• 1997

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2001.05a
• /
• pp.40-40
• /
• 2001

• Proceedings of the Materials Research Society of Korea Conference
• /
• 1999.05a
• /
• pp.122-122
• /
• 1999

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.1245-1246
• /
• 2011

• Korean Journal of Materials Research
• /
• v.2 no.5
• /
• pp.343-352
• /
• 1992

The high temperature deformation behavior of microalloyed hot forging steels has been examined as a function of the temperature, the strain rate, and the alloying element by using high temperature compression test. The high temperature deformation mechanism, which was obtained by analyzing the flow stress-strain curve and microstructure, could be considered to dynamic recrystallization. The peak stress of Nb-V-Mo steel was more increased and the dynamic recrystallization of Nb-V-Mo steel was faster than those of Nb-V steel. The peak stress of 1.2Mn-0.09Nb steel was more increased and the dynamic recrystallization of 1.2Mn-0.09Nb was delayed a little bit than those of 1.0Mn-0.05Nb. The peak stress of C-Nb-V steel was more increased and the dynamic recrystallization of C-Nb-V steel was delayed than those of C-steel. The constitutive equation of high temperature deformation had a power law type. The grain size of dynamic recrystallization was refined as the Zener-Hollomon parameter was increased. The relation of the dynamic recrystallization grain size and Zener-Hollomon parameter could be quantified to power law.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.26-29
• /
• 2008

Recently, the hydroforming of high strength aluminum tubes has many studies and applications in manufacturing industry, especially in automotive industry. But high strength aluminum tube has limited expansion capability at most 15% at normal temperature. New manufacturing process, called hot air forming, is introduced to apply aluminum tube to the automotive sub frame components which have complex shape and require high expansion ratio about 40%. The process is carried out at the elevated temperature above $500^{\circ}C$, so numerous material properties and process parameters related to high temperature should be investigated and determined to get a sound product. In this paper, the hot air forming process of automotive sub frame was investigated. The effect of the forming parameters such as the temperature of tool, axial feeding and gas pressure are analyzes by using explicit finite element method.

• Resources Recycling
• /
• v.3 no.1
• /
• pp.25-31
• /
• 1994

This paper was focused to optimize hot extrusion condition of Mg machined chips and scraps as fundamental basic research for the recycle of Mg alloy. We have been performed to extrude at $300~380^{\circ}C$ temperature range under the extrusion ratio of 25:1 after cold-pressing AZ91 Mg machined chips and scraps. AZ91 Mg ingots was used as reference materials. Microstructure observation showed that the extruded machined chips were perfectly bonded and extruded materials became fine grain size($20\mu\textrm{m}$) by recrystallization during hot extrusion. The specimens extruded from the machined chips, scraps and Mg ingot indicated tensile strength of 330MPa and the elongation of 10% at room temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.03b
• /
• pp.265-268
• /
• 1999

열간 박판 압연공정에서의 압연하중 압연동력을 실시간으로 계산할 수 있는 모델식을 유한요소 해석결과들을 이용하여 개발하였다 압연하중 압연동력값 결정에 비교적 큰 영향을 주는 인자들로는 형상계수 압하률, 률직경 률속도 스트립 입측온도, 탄소함량, 마찰계수들은 이론적으로 계산이 가능한 무마찰의 균일 평면 변형유 압축공정의 금형하중(F、) 동력 (P、)식을 도입함으로써 내삽모델식에서 제외시킬수 있었다 쿨롱마찰계수($\mu$) 0.3 일 경우의 유한요소해석 결과 데이터들을 내삽법(interpolation)을 통해서 다항식 형태로 {{{{ {F } over {F、 } }}}}, {{{{ { {P }_{f } } over { {P }_{d } } }}}}, {{{{ { {P }_{d } } over { {P }^{、 } } }}}} 식들을 구하였다 마찰계수에 따른{{{{ {F } over {F、 } }}}} {{{{ {P } over { {P }^{、 } } }}}}값의 변화는 형상계수에 따라 기울기가 결정되는 직선 형태로 나타내어짐을 유한요소해석 결과로부터 관찰 할 수 있었다. 이와같이 구한 압연하중 압연동력 모델식의 유효성을 검증하기 위해 무작위로 추출한 실제공정들에서 모델식으로 계산한 압연하중 압연동력 값들을 유한요소해석결과와 서로 비교해 보았다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.3
• /
• pp.816-824
• /
• 1996

The densification behaviors of copper powder under high temperature processing were investigated. Experimental data were obtained for copper powder under hot isostatic pressing, hot pressing and uniaxial compression. Finite element calculations from the constitutive models by McMeeking and co-workers were compared with the experimental data, The agreements between experimental data and theoretical calculations are reasonably good when hydrostatic stress is dominant, but not as good then deviatoric stress increases.