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북한의 물적 자원 동원 가능 여부 검토를 통한 사회기반시설 피해 복구 발전 방안
이성학(Sunghak Lee),최미경(Mikyoung Choi),박영준(Youngjun Park) 육군사관학교 화랑대연구소 2018 한국군사학논집 Vol.74 No.2
The restoration of SOC(Social Overhead Capital) in North Korea is crucial for the success of stabilizing operations. In particular, a legal review is needed to mobilize local resources in the North to secure the resources needed to recover the SOC. Therefore, considering the domestic law and international law, the mobilization of material resources in the North is available for restoration of infrastructure in North Korea, but the mobilization of material resources in North Korea is not available in the North. Without the use of material resources in North Korea, I proposed measures to recover the SOC in North Korea. One is to preponderated the mobilization plans for military in Ministry of Land, Infrastructure and Transport. The second was the need for the cooperation of the Joint Cooperation Agency, a coordinating organization for the government, to assist in the restoration of SOC damage.
고망간 Twinning Induced Plasticity 강의 인장 특성에 미치는 변형률 속도와 온도의 영향
이정훈,이성학,신상용,Lee, Junghoon,Lee, Sunghak,Shin, Sang Yong 한국재료학회 2017 한국재료학회지 Vol.27 No.12
Four types of high Mn TWIP(Twinning Induced Plasticity) steels were fabricated by varying the Mn and Al content, and the tensile properties were measured at various strain rates and temperatures. An examination of the tensile properties at room temperature revealed an increase in strength with increasing strain rate because mobile dislocations interacted rapidly with the dislocations in localized regions, whereas elongation and the number of serrations decreased. The strength decreased with increasing temperature, whereas the elongation increased. A martensitic transformation occurred in the 18Mn, 22Mn and 18Mn1.6Al steels tested at $-196^{\circ}C$ due to a decrease in the stacking fault energies with decreasing temperature. An examination of the tensile properties at $-196^{\circ}C$ showed that the strength of the non-Al added high Mn TWIP steels was high, whereas the elongation was low because of the martensitic transformation and brittle fracture mode. Although a martensitic transformation did not occur in the 18Mn1.9Al steel, the strength increased with decreasing temperature because many twins formed in the early stages of the tensile test and interacted rapidly with the dislocations.
군 구조개혁에 따른 통합부대의 건축물 공유 및 합병 방안에 관한 연구
박영준(Park, Young Jun),이성학(Lee, Sunghak),최원정(Choi, Wonjoung),장창수(Jang, Changsu),김흥빈(Kim, Heungbin),손기영(Son, Kiyoung) 대한건축학회 2017 대한건축학회논문집 Vol.33 No.8
This study suggests the installment plan for the sharing and merging facilities of the unified troops according to the military structure reform. For this purpose, the intensive survey to reflect the opinions of various respondents such as enlisted and executive groups was conducted with the questionnaire which is composed with 13 statements associated with the sharing and merging facilities. The descriptive statistics and analysis of variance were used to identify the general pros and cons as well as difference of opinions between two groups, the executive and enlisted groups. According to the statistical analysis, even though there are a few inconsistent views concerning preference, two groups coincide in opinions for and against sharing and merging facilities without the repair facilities. The current defense military facility criteria have not been used dominantly in the determination to the architectural requirements of the armed forces because it did not reflect the actual demand of the field forces. Furthermore, the system to manage this architectural requirement has been invented to the permanent division units in conformity, so that its serviceability are not flexible in estimating architectural requirement of the unified troops. The outcomes of this study, which reflects the field claims, would be used as a basic data to assess the architectural requirements of the sharing and merging facilities in the unified troops.
금속고화체용 STS304-Zr 합금의 미세조직과 파괴거동에 미치는 열처리의 영향
김종우,장선아,한승엽,박환서,이정훈,이성학,권용재,이정구,신상용,Kim, Jongwoo,Jang, Seon Ah,Han, Seung Youb,Park, Hwan Seo,Lee, Junghoon,Lee, Sunghak,Kwon, Yongjai,Lee, Jung Gu,Shin, Sang Yong 한국재료학회 2018 한국재료학회지 Vol.28 No.3
Three kinds of STS304-Zr alloys were fabricated by varying the Zr content, and their microstructure and fracture properties were analyzed. Moreover, we performed heat treatment to improve their properties and studied their microstructure and fracture properties. The microstructure of the STS304-Zr alloys before and after the heat treatment process consisted of ${\alpha}-Fe$ and intermetallics: Zr(Cr, Ni, Fe)2 and Zr6Fe23. The volume fraction of the intermetallics increased with an increasing Zr content. The 11Zr specimen exhibited the lowest hardness and fine dimples and cleavage facets in a fractured surface. The 15Zr specimen had high hardness and fine cleavage facets. The 19Zr specimen had the highest hardness and large cleavage facets. After the heat treatment process, the intermetallics were spheroidized and their volume fraction increased. In addition, the specimens after the heat treatment process, the Laves phase (Zr(Cr, Ni, Fe) 2) decreased, the Zr6Fe23 phase increased and the Ni concentration in the intermetallics decreased. The hardness of all the specimens after the heat treatment process decreased because of the dislocations and residual stresses in ${\alpha}-Fe$, and the fine lamellar shaped eutectic microstructures changed into large ${\alpha}-Fe$ and spheroidized intermetallics. The cleavage facet size increased because of the decomposition of the fine lamellar-shaped eutectic microstructures and the increase in spheroidized intermetallics.
오진근(Jinkeun Oh),김낙준(Nack J. Kim),이성학(Sunghak Lee),이의휘(Eui W. Lee) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8
The effects of microstructural factors on high-cycle fatigue properties of welded regions of an investment cast Ti-6AI-4V alloy were investigated in this study. High-cycle fatigue were conducted for the welded regions, which were processed by two different welding methods, i.e. tungsten inert gas (TIG) welding and electron beam (EB) welding, and then the test data were analyzed in relation with microstructures, tensile properties, and fatigue fracture mode. The base metal was composed of a Widmanstatten structure, which was then transformed to a basket-weave structure having thin a platelets after welding and annealing. The high-cycle fatigue results indicated that fatigue strength of the EB weld was lower than that of the base metal or the TIG weld because of the existence of coarse micropores formed during welding, although it had highest yield strength.
탄도충격을 받은 2층 육성용접 장갑판재의 균열생성 및 전파거동 연구
이성학,추성훈,백응율 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.7
The objective of this study is to investigate microstructural characteristics of a two-layer hardfaced armor plate after ballistic impact. In order to deaelop the newly-designed armor plate, high hardness, hypereutectic high Cr white iron and ductile SUS 309 stainless steel were hardfaced nn an HY l00 steel plate using self-shielding flux cored arc welding method. This hardfaced plate was ballistically impacted, and metallurgical observations of the area near the perforated region were conducted. The high Cr white iron hardfaced layer was obseved to block effectively a fast traveling prajectile, although microcracks were initiated at coarse primary carbides of the high Cr hardfaced layer, and propagated to form longer cracks However, very few cracks were found in the stainless steel hardfaced layer, which tended to hinder the propagating crack. These foundings suggest that ballistic performance of the multi-layered armor plates fabricated by hardfacing technique might be improved.
Ti-6Al-4V 합금의 동적변형특성과 탄도충격성능 : 1. 초고속 폭발충격 특성 1. Ultra-high-speed Exploding Properties
이유환,이동근,이성학,이종수,최준홍,허선무 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.10
The effects of microstructural morphology on ultra-high-speed exploding properties of Ti-6Al-4V alloy were investigated in this study. Exploding bridge wire (EBW) test was conducted on equiaxed and bimodal microstructures, which were processed by different heat treatments. From the test, moving velocity of free surface vs time profiles were obtained to measure strength at Hugoniot elastic limit (HEL) and spall strength and to subsequently predict ballistic mass efficiency. The EBW results indicated that impact resistance of the bimodal microstructure was better than that of the equiaxed microstructure when the measured strength at HEL and spall strength were considered. It was also learned from the observation of fractured EBW specimens that fracture occurred by the initiation and propagation of long cracks in the equiaxed microstructure, whereas a number of microcracks were formed and connected each other in a zig-zag pattern to reduce the driving force for crack propagation in the bimodal microstructure. Since the EBW test helped experimentally estimate ultra-high-speed deformation and fracture behavior, it could be effectively used for the prediction of ballistic impact performance.