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밀링 에너지 변화에 따른 TiC 분말의 미세화 거동에 관한 정량적 연구
홍성모,박은광,김경열,박진주,이민구,이창규,이진규,권영순,Hong, Sung-Mo,Park, Eun-Kwang,Kim, Kyeong-Yeol,Park, Jin-Ju,Lee, Min-Ku,Rhee, Chang-Kyu,Lee, Jin-Kyu,Kwon, Young-Soon 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.1
This study investigated refinement behaviors of TiC powders produced under different impact energy conditions using a mechanical milling process. The initial coarse TiC powders with an average diameter of 9.3 ${\mu}m$ were milled for 5, 20, 60 and 120 mins through the conventional low energy mechanical milling (LEMM, 22G) and specially designed high energy mechanical milling (HEMM, 65G). TiC powders with angular shape became spherical one and their sizes decreased as the milling time increased, irrespective of milling energy. Based upon the FE-SEM and BET results of milled powders, it was found initial coarse TiC powders readily became much finer near 100 nm within 60 min under HEMM, while their sizes were over 200 nm under LEMM, despite the long milling time of up to 120 min. Particularly, ultra-fine TiC powders with an average diameter of 77 nm were fabricated within 60 min in the presence of toluene under HEMM.
기계적 밀링 공정에 의해 제조된 Al-B<sub>4</sub>C 복합분말의 밀링 거동 연구
홍성모,박진주,박은광,이민구,이창규,김주명,이진규,Hong, Sung-Mo,Park, Jin-Ju,Park, Eun-Kwang,Lee, Min-Ku,Rhee, Chang-Kyu,Kim, Ju-Myoung,Lee, Jin-Kyu 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.4
In the present work, Al-$B_4C$ composite powders were fabricated using a mechanical milling process and its milling behaviors and mechanical properties as functions of $B_4C$ sizes ( $100{\mu}m$, 500 nm and 50 nm) and concentrations (1, 3 and 10 wt.%) were investigated. For achieving it, composite powders and their compacts were fabricated using a planetary ball mill machine and magnetic pulse compaction technology. Al-$B_4C$ composite powders represent the most uniform dispersion at a milling speed of 200 rpm and a milling time of 240 minutes. Also, the smaller $B_4C$ particles were presented, the more excellent compositing characteristics are exhibited. In particular, in the case of the 50 nm $B_4C$ added compact, it showed the highest values of compaction density and hardness compared with the conditions of $100{\mu}m$ and 500 nm additions, leading to the enhancement its mechanical properties.
박만호(Park Man-Ho),문제우(Mun Je-U),김성일(Kim Sung-Il),홍성모(Hong Seong-Mo),김종태(Kim Jong-Tae) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
Mo-Am arch bridge is only the long-span bridge (with 125m span) in the Kyong-Bu high-speed line in service, while other bridges are PSC box girder bridges and steel composite bridges with span lengths of 25~50m. However, in foreign high-speed lines, special cable-supported bridges like cable-stayed bridges and extradosed bridges are being adopted in earnest with technical specifications. The cable supported bridge is recognized as one of the indices of technology in civil engineering field, and thus it is being adpoted with a sense of rivalry in countries with advanced technology in railway engineering. In this paper, to apply the top-level cable-supported bridge technology to the domestic high-speed line up to 400㎞/h by establishing the technical specifications on cable-supported bridges including span length, the requirements for securing the dynamic stability and running safety of high speed train are analyzed through case studies for domestic and foreign cases.
오스테나이트계 304 스테인리스강의 케비테이션 기포 및 고체 입자 동시 충격 손상의 정량적 고찰
홍성모 ( Sung Mo Hong ),박진주 ( Jin Ju Park ),이민구 ( Min Ku Lee ),이창규 ( Chang Kyu Rhee ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.10
In the present work, the impact loads and their effects on the surface damage under the simultaneous cavitation bubble and solid particle collapses in the sea water have been quantitatively investigated for the austenitic 304 stainless steel by using a vibratory cavitation test device. To do this, angular SiO2 solid particles with an average size of 150 μm were dispersed into the test liquid, and the measured impact amplitudes were converted into the impact loads by a steel ball drop test. The maximum impact load was determined to be 28.2 N in the absence of solid particles, but increased to 33.7 N in the presence of solid particles. In addition, the critical impact loads, Lcrit, required to generate pits with sizes greater than 3 μm were measured to be 19.6 N and 16.6 N, respectively, for the cavitation bubble collapse and solid particle collapse. As a result of the cavitation erosion test, the incubation time and erosion rate were 1.2 times lower and 1.5 times higher, respectively, by a solid particle collapse compared to those only by the cavitation bubble collapse, indicating a drastic decrease in a resistance to cavitation erosion by the solid particle collapse.
원전 해수 펌프 임펠러 합금의 케비테이션 피로 손상 해석
홍성모(Sung-Mo Hong),이민구(Min-Ku Lee),김광호(Gwang-Ho Kim),이창규(Chang-Kyu Rhee) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.1
In this study, the fatigue properties on the cavitation damage of the flame quenched 8.8Al-bronze (8.8Al-4.5Ni-4.5Fe-Cu) as well as the current nuclear pump impeller materials (8.8Al-bronze, STS316 and SR50A) has been investigated using an ultrasonic vibratory cavitation test. For this the impact loads of cavitation bubbles generated by ultrasonic vibratory device quantitatively evaluated and simultaneously the cavitation erosion experiments have been carried out. The fatigue analysis on the cavitation damage of the materials has been made from the determined impact load distribution (e.g. impact load, bubble count) and erosion parameters (e.g. incubation period, MDPR). According to Miner's law, the determined exponents b of the F?N relation (FbㆍN = Constant) at the incubation stage (N: the number of fracture cycle) were 5.62, 4.16, 6.25 and 8.1 for the 8.8Al-bronze, flame quenched one, STS316 and SR50A alloys. respectively. At the steady state period, the exponents b of the F?N' curve (N': the number of cycle required for 1 ㎛ increment of MDP) were determined as 6.32, 5, 7.14 and 7.76 for the 8.8Al-bronze, flame quenched one, STS316, and SR50A alloys, respectively.
화염급냉 표면처리된 Cu-9AI-4.5Ni-4.5Fe 합금의 β' 마르텐사이트 형성에 의한 케비테이션 침식 저항성 향상에 관한 연구
홍성모(Sung-Mo Hong),이민구(Min-Ku Lee),김광호(Gwang-Ho Kim),김경호(Kyeong-Ho Kim),김흥회(Whung-Whoe Kim),홍순익(Sun-Ig Hong) 한국표면공학회 2004 한국표면공학회지 Vol.37 No.4
Cavitation erosion properties of the Cu-9AI-4.5Ni-4.5Fe alloys (Al-bronze) surface-modified by flame quenching process have been investigated. After flame quenching at above T p, the surfaces of AI-bronze with α + κ structure have been changed into the α + β’ martensite phases by the eutectoid reaction of α + κ→β followed by the martensite transformation of β→’. As a result of cavitation test, the measured incubation time and erosion rate of the α + β’ alloy was 1.2 times higher and 1.5 times lower, respectively, compared to those of the conventional α + κ alloys, showing a remarkable increase of cavitation resistance with the formation of β martensite. This is attributed to a preferential erosion of the κ precipitates that show the lowest resistance among the α, κ, β’ phases under cavitation loading.
B<sub>4</sub>C 함량에 따른 6061 Al-B<sub>4</sub>C 복합분말의 소결 특성 연구
박진주,홍성모,김경열,이민구,이창규,이원혁,이양규,Park, Jin-Ju,Hong, Sung-Mo,Kim, Kyoung-Yeol,Lee, Min-Ku,Rhee, Chang-Kyu,Rhee, Won-Hyuk,Lee, Yang Kyu 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.3
In the present work, 6061 Al-$B_4C$ sintered composites containing different $B_4C$ contents were fabricated and their characteristic were investigated as a function of sintering temperature. For this, composite powders and their compacts with $B_4C$ various contents from 0 to 40 wt.% were fabricated using a planetary ball milling equipment and cold isostatic pressing, respectively, and then they were sintered in the temperature ranges of 580 to $660^{\circ}C$. Above sintering temperature of $640^{\circ}C$, real density was decreased due to the occurrence of sweat phenomena. In addition, it was realized that sinterability of 6061Al-$B_4C$ composite material was lowered with increasing $B_4C$ content, resulting in the decrease in its real density and at the same time in the increment of porosity.
레이저 클래딩법을 이용한 AISI 316L 스테인리스강 내 Y<sub>2</sub>O<sub>3</sub>입자의 분산거동
박은광,홍성모,박진주,이민구,이창규,설경원,이양규,Park, Eun-Kwang,Hong, Sung-Mo,Park, Jin-Ju,Lee, Min-Ku,Rhee, Chang-Kyu,Seol, Kyeong-Won,Lee, Yang-Kyu 한국분말야금학회 2013 한국분말재료학회지 (KPMI) Vol.20 No.4
The present work investigated the dispersion behavior of $Y_2O_3$ particles into AISI 316L SS manufactured using laser cladding technology. The starting particles were produced by high energy ball milling in 10 min for prealloying, which has a trapping effect and homogeneous dispersion of $Y_2O_3$ particles, followed by laser cladding using $CO_2$ laser source. The phase and crystal structures of the cladded alloys were examined by XRD, and the cross section was characterized using SEM. The detailed microstructure was also studied through FE-TEM. The results clearly indicated that as the amount of $Y_2O_3$ increased, micro-sized defects consisted of coarse $Y_2O_3$ were increased. It was also revealed that homogeneously distributed spherical precipitates were amorphous silicon oxides containing yttrium. This study represents much to a new technology for the manufacture and maintenance of ODS alloys.