http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
논문 : Al 첨가 TWIP강에서의 지연파괴에 대한 변형유기 마르텐사이트 변태의 영향
김영우 ( Young Woo Kim ),강남현 ( Nam Hyun Kang ),박영도 ( Young Do Park ),최일동 ( Il Dong Choi ),김교성 ( Gyo Sung Kim ),김성규 ( Sung Kyu Kim ),조경목 ( Kyung Mox Cho ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 대한금속·재료학회지 Vol.46 No.12
For the advanced high strength steels (AHSS), high-manganese TWIP (twinning induced plasticity) steels exhibit high tensile strength (800-1000 MPa) and high elongation (50-60%). However, the TWIP steels need to be understood of delayed fracture following the cup drawing test. Among the factors to cause delayed fracture, i.e, martensite transformation, hydrogen embrittlement and residual stress, the effects of martensite transformation (γ→ε or γ→α`) were investigated on the delayed fracture phenomenon. Microstructural phase analysis was conducted for cold rolled (20, 60, 80% reduction ratio) steels and tensile deformed (20, 40, 60% strain) steels. For the Al-added TWIP steels, no martensite phase was found in the cold rolled and tensile deformed specimen. But, the TWIP steels with no Al addition indicated the martensite transformation. The cup drawing specimens showed the martensite transformation irrespective of the Aladdition to the TWIP steel. However, the TWIP steel with no Al exhibited the larger amount of martensite than the case of the TWIP steel with Al addition. For the reason, it was possible to conclude that the Al addition suppressed the martensite transformation in TWIP steels, therefore preventing the delayed fracture effectively. However, it was interesting to note that the mechanism of delayed fracture should be incorporated with hydrogen embrittlement and/or residual stress as well as the martensite transformation.
열간프레스성형에서의 변형 측정장치 개발 및 기계적 거동의 물성화
유동훈(Donghoon Yoo),석동윤(Dong-Yoon Seok),김돈건(Dongun Kim),안강환(Kanghwan Ahn),손현성(Hyun-Sung Son),김교성(Gyo-Sung Kim),정관수(Kwansoo Chung) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
As a way to improve the safety of automotive and to reduce the weight of vehicles, new forming technologies and advanced materials are in high demand in the automotive industry. However, the advanced strength steel has inferior formability and large springback. In order to overcome such drawbacks, the hot press forming process (HPF) has been being applied for forming of automotive sheet parts. In this work, new equipment was suggested to measure unlimited displacement range compared to previous one which was able to measure only up to 10mm displacement range. The external extensometer connected with grips by wire was applied to equipment so that total strain range was measured up to failure also in high temperature. And the finite element analysis was conducted to characterize the mechanical properties of the HPF steel. Finally, the flow curves were represented by utilizing the Johnson-Cook type equation both in uniform and post-uniform deformation regions.