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Fe-18Mn TWIP강의 Pre-strain에 따른 저주기 피로 수명 예측 모델 연구
김용우(Y. W. Kim),이종수(C. S. Lee) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.10
The influence of pre-strain in low-cycle fatigue behavior of Fe-18Mn-0.05Al-0.6C TWIP steel was studied by conducting axial strain-controlled tests. As-received plates were deformed by rolling with reduction ratios of 10 and 30%, respectively. A triangular waveform with a constant frequency of 1 Hz was employed for low cycle fatigue test at the strain amplitudes in the range of ±0.4~±0.6 pct. The results showed that low-cycle fatigue life was strongly dependent on the amount of pre-strain as well as the strain amplitude. Increasing the amount of prestrain, the number of reversals to failure was significantly decreased at high strain amplitudes, but the effect was negilgible at low strain amplitudes. A new model for predicting fatigue life of pre-strained body has been devised adding a correction term of ΔEpre-strain to the energy-based fatigue damage parameter.
벤젠 확산 화염을 이용한 플러렌(C<SUB>60</SUB>)의 전구 물질인 PAHs 합성
김용우(Y. W. Kim),이교우(G.-W. Lee),황정호(J. Hwang),정종수(J. Jrung),최만수(M. Choi) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
Carbon molecules with closed-cage structures are called fullerenes (C<SUB>60</SUB>, C<SUB>70</SUB>), whose synthesis has been recently studied with low pressure benzene/argon/oxygen flames. The formation of fullerenes is known as molecular weight growth processes of PAHs (polycyclic aromatic hydrocarbon). Thus investigation of the formation of PAHs is directly related with the formation of fullerenes and is important to determine optimal experimental conditions. This paper presents preliminary results of PAHs measurements performed in a low pressure benzene/argon/oxygen normal co-flow laminar diffusion flame. Through the central tube of the burner, benzene vapors carried by argon is injected. The benzene vapors are made in a temperature-controlled bubbler. The burner is located in a chamber, equipped with a sampling system for direct collection of condensible species from the flame, and exhausted to a vacuum pump. Samples of condensibles are analyzed by HPLC (High Performance Liquid Chromatogram) to determine the yields of PAHs and to confirm the existence of fullerenes.