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용탕단조법으로 제조된 AZ91 Mg / Al Borate 휘스커 복합재료의 미세조직 및 기계적 특성
김광천,조영서,이성학,박익민 ( Kwang Chun Kim,Young Su Cho,Sung Hak Lee,Ik Min Park ) 한국주조공학회 1996 한국주조공학회지 Vol.16 No.6
N/A This study aims at investigating the correlation of microstructure and mechanical properties of the AZ91 Mg/Al borate whisker composites fabricated by squeeze casting technique with a variation of applied pressure. Microstructure observation and in-situ fracture tests were conducted on the composites to identify the microfracture process. Detailed microstructural analyses indicated that the grain refinement could be achieved with applied pressure and the little change in volume fraction on reinforcing whiskers could be carried out. It was also found clearly from in-situ observation of crack initiation and propagation that in the composite processed by the lower applied pressure, microcracks were initiated earily at whisker/matrix interfaces, thereby resulting in the drop in strength. In the composite processed by the higher applied pressure, on the other hand, planar slip lines were well developed in the matrix, and then propagated through whiskers without whisker/matrix decohesion. Thus, the effect of the applied pressure on microstructure and mechanical properties can be explained by grain refinement, increased amounts of reinforcements, and improvement of whisker/matrix interfacial strength as the applied pressure in increased.
심상철 ( Sang Chul Shim ),조중욱 ( Jung Wook Cho ),황상택 ( Sang Taek Hwang ),김광천 ( Kwang Chun Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 대한금속·재료학회지 Vol.46 No.10
The behavior of hydrogen in the steel making process was investigated. The relation between the composition of ladle slag and hydrogen concentration in molten steel was considered. The hydrogen distribution ratio between ladle slag and molten steel was increased with increasing basicity of the slag; it was about 20 when the basicity of slag was 15. Hydroxyl capacity measured from the hydrogen distribution ratio between slag and the molten steel was comparatively corresponding to the value of hydroxyl capacity measured by the equilibrium reaction of slag and H2O gas. However, it is considerably different from the value calculated by regular solution model. The influence of hydrogen on a sticking type breakout is considered. The effect of hydrogen and H2O gas on the crystallization behavior of mold powder was investigated by DHTT(Dual hot thermocouple technique). As a result, it was proved that mold powder could be crystallized by H2O gas in the atmosphere. Therefore, it is concluded that H2O gas in the atmosphere can be a possible cause of the sticking type breakout that occasionally occurs in the continuous casting process.
김광천,김동창 중앙대학교 의과대학 의과학연구소 1988 中央醫大誌 Vol.13 No.2
For the study of the physical growth and body flexibility in Korean adolescence male, the stature, span, body weight, standing-trunk flexion and trunk extension of 1182 cases ranging from 15 to 18 years of age were measured and the correlation coefficients were computed between those items. The results obtained were as follows: 1. The average statures by age were 162.08cm at age 15, 167.20cm at age 16, 168,54cm at age 17, 169.46cm at age 18 and the stature growth per year was 2.46cm. 2. The average spans by age were 161.86cm at age 15,167.66cm at age 16,160.82cm at age 17,169.32cm age 18 and the span growth per year was 2.49cm. 3. The average body weights by age were 51.76kg at age 15, 56.90kg at age 16, 59.52kg at age 17, 60.90kg at age 18 and the body weight increase per year was 3.05kg. 4. The averages of standing-trunk flexion by age were 10.08cm at age 15, 11.74cm at age 16, 12.26cm at age 17 and 49.52cm at age 18. 5. The averages of trunk extension by age were 48.86cm at age 15, 49.34cm at age 16, 49.48cm at age 17 and 49.52cm at age 18. 6. The correlation coefficients between stature and span were very high (over 0.8) in any age group, being especially higher in lower age. The correlation coefficients between stature and body weight, and span and body weight also were high in lower age but moderate value in higher age. 7. The correlation coefficients between standing-trunk 11e%ion and trunk extension were low value (under 0.31) in every age group, especially remarkable in 16 years of age. 8. The correlation coefficients between physical measurements and flexibilities were low (undo.0.32) or very low value (under 0.19). 9. The regression equations among all of the items in each age group are tabled for reference.