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남승훈,김시천,전승범 ( S . H . Nahm,S . C . Kim,S . B . Jeon ) 한국열처리공학회 1995 熱處理工學會誌 Vol.8 No.4
Information of change of hardness values during applying load is needed often to control the quality of metal products efficiently, but the relation between applied stress and hardness has not been established. In this paper the theoretical relation between the rebound hardness and stress was examined briefly and the experiment was performed with some materials. Materials used in test were mild steel(SB41), 7-3 brass and copper, which were widely used in the commercial plants. Hardness was measured during stress applied using the Equo-Tip hardness tester as a kind of rebound hardness tester. Hardness values decreased as tensile stress increased, the decreasing rate was effected by the Young`s modulus of each material, and the rebound hardness values showed linear relationship with the applied stress in elastic region.
CNG 저장용기용 저합금강의 인장 특성에 미치는 고압 수소가스의 영향
이해무(H. M. Lee),정인현(I. H. Jeong),박종서(J. S. Park),남승훈(S. H. Nahm),한정옥(J. O. Han),이영철(Y. C. Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Natural gas that can be produced from coal or biomass is known as “synthetic natural gas” or “substitute natural gas” (SNG). SNG could be a major driver for energy security. SNG production could diversify energy options and reduce natural gas imports. Also, HCNG (or H₂CNG), a mixture of CNG(compressed natural gas) and 4-9 percent hydrogen by energy, is expected to be used as a fuel gas for internal combustion engines and home appliances due to extremely low emissions and increases in thermal efficiency. However, mechanical properties can be deteriorated by hydrogen contained in SNG or HCNG. It is necessary, therefore, to investigate the effect of hydrogen on the mechanical properties of materials used for the existing natural gas infrastructure so that SNG or HCNG can be transported and distributed safely and reliably. In this study, the effect of highly pressurized hydrogen gas on tensile properties of a low alloy steel used for CNG storage vessels was investigated using so-called hollow tensile specimen technique.
CNG 저장용기용 저합금강의 인장 특성에 미치는 고압 수소가스의 영향
이해무(H. M. Lee),정인현(I. H. Jeong),박종서(J. S. Park),남승훈(S. H. Nahm),한정옥(J. O. Han),이영철(Y. C. Lee) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.8
대체천연가스(SNG)는 에너지 안보 차원에서 에너지 수급 안정화 방안의 하나로 많은 관심을 받고 있다. 또한 HCNG (또는 H₂CNG)는 배기가스 내의 유해 성분을 현저히 줄이고 열효율도 높일 수 있어서 내연기관이나 가정용 연료로 사용될 것으로 기대되고 있다. 그러나 SNG나 HCNG에 포함되어 있는 수소는 재료에 침투하여 그 재료의 역학적 특성을 크게 저하시키는 것으로 알려져 있다. 따라서 SNG나 HCNG를 안전하고 효율적으로 수송ㆍ공급하려면 이를 위해 운용되는 인프라의 안전성과 신뢰성 확보가 선결되어야 한다. 본 연구에서는 중공 시험편을 이용한 인장시험법을 통하여 CNG 저장용기용 저합금강이 나타내는 고압 수소 분위기에서의 인장 특성 변화에 대하여 조사하였다. SNG (synthetic natural gas or substitute natural gas) could contribute greatly toward energy security. In addition, HCNG (or H₂CNG) is expected to be used as a fuel gas for internal combustion engines and home appliances because it has extremely low emissions and high thermal efficiency. However, the hydrogen contained in SNG or HCNG can deteriorate the mechanical properties of the materials used in existing natural gas infrastructure. Therefore, it is necessary to investigate the effect of hydrogen on the mechanical properties of such materials so that SNG or HCNG can be transported and distributed safely and reliably. In this study, the effect of highly pressurized hydrogen gas on the tensile properties of a low-alloy steel used for manufacturing CNG storage vessels was investigated using the so-called hollow tensile specimen technique.
남승훈,전승범,김종집 ( S . H . Nahm,S . B . Jeon,J . J . Kim ) 한국열처리공학회 1990 熱處理工學會誌 Vol.3 No.2
For the accurate measurements of hardness in a material, it is necessary to have a thorough understanding of the effects of test variables on the accuracy of hardness value. For the rebound hardness test, major test variables are the radius of hammer ball tip, type of backing materials, size and roughness of the specimen. In this study, effects of these variables on Equo-Tip hardness value were investigated. Hardness measurements were carried out using WC balls with various sizes of worn-ot zone. The sample materials chosen for the experiments were commercial standard hardness blocks and SM45C steel bars subjected to either normalization or quench and temper treatments. As backing materials, aluminum, steel and rubber plates were used in all the experiments. Experimental results show that for the accurate measurements of Equo-tip hardness, it is necessary to use the hammer ball with a worn-out zone parameter of less than 0.23, and the recommended minimum thickness and width of the specimen are 25㎜ and 70㎜, respectively. Further for the surface preparation, the specimens need to be polished with an emery paper of No. 400 or finer, and for the backing matrials, it is recommended to use steels or rubbers.