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Ni기 초내열합금의 액상확산접합부 생성상의 금속조직학적 검토
김대업 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.1
The metallurgical study of microconstituents in transient liquid phase bonded joints of Ni-base single crystal superalloys, CMSX-2 and CMSX-4 was investigated employing MBF-80 insert metal. TLP bonding of specimens was carried out at 1,373~1,523K for 0~19.6ks in vacuum. Three types of microconstituents ; needle-like constituent, dot-like constituent and abnormal shape constituent were formed in the bonded interlayer during TLP bonding operation. All these microconstituents were identified as boride. Microconstituents contain a large percentage of Cr in the early stage of bonding. As increasing the holding time, the amount of Cr was decreased and the amount of W, Co and Re were increased. From the analysis results of electron diffraction pattern by TEM, composition of elements in microconstituents were into MBlongrightarrowM$_{5}$B$_3$longrightarrowM$_2$B type with the increased in holding time. It can be explained by the fact that the relative amount of boron in microconstituents was decreased when the holding time was increased.d.
액상확산접합한 Ni기 단결정 초내열합금의 크리프 파단 및 피로특성
김대업 대한용접접합학회 2001 대한용접·접합학회지 Vol.19 No.1
The creep-rupture and low cycle fatigue properties of transient liquid phase bonded joints of Ni-base single crystal superalloy, CMSX-2 was investigated using MBF-80 insert metal. The (100) orientation of bonded specimen was aligned perpendicular to the joint interface. CMSX-2 was bonded at 1523K for 1.8ks in vacuum, optimum bonding condition. The creep rupture strength and rupture lives of the joints were the almost identical to ones of the base metal. SEM observation of the fracture surfaces of joints after creep rupture test revealed that the fracture surfaces classified three types of region, ductile fracture surface, cleavage fracture surface and interfacial fracture surface. The low cycle fatigue properties of the joints were also the same level as those of base metal. The elongation and reduction of area values of joints were comparable to those of base metal while fell down on creep rupture condition of high temperature.
김대업,강정윤 대한용접접합학회 2000 대한용접·접합학회지 Vol.18 No.3
Single crystallization behavior ad high temperature tensile properties of TLP bonded joints of Ni-base single crystal superalloy, CMSX-2 were investigated using MBF-80 and F-24 insert metals. CMSX-2 was bonded at 1523~1548K for 1.5~1.8ks in vacuum. The (100) orientation of bonded specimen was aligned perpendicular to the joint interface. Crystallographic orientation analyzed points over the bonded region possessed the almost same orientation across the joint interface and misorientation $\Delta^{\theta}$ was negligibly small in as-bonded and post-bond heat-treated situations. It was confirmed that single crystallization could be readily achieved during TLP bonding. The tensile strengths of all joints at elevated temperatures were equal to or greater than those of base metal the range of testing temperature between 923K and 1173K. The elongation and reduction of area in values were almost the same as those of base metal. SEM observation of the fracture surfaces of joints after tensile test revealed that the fracture surface indicated the similar morphologies each other, and that the fracture of joints occurred in the base metal in any cases.
승용차용 히터 코어 및 증발기의 성능 개선을 위한 메타모델 기반 최적화 연구
김대업,서왕벽 한국기계기술학회 2020 한국기계기술학회지 Vol.22 No.3
In this study, optimizations were carried out for a heater core and an evaporator installed in a passenger car. The main geometric parameters of each component were selected as design variables, and the main performances examined were the outlet temperature and the pressure drop. In addition, the sensitivity analysis was performed to grasp the dominant design variable. The thermal flow analysis for each component was performed using the commercial program STAR CCM+. On the other hand, EasyDesign, a commercial program based on DOE and metamodel-based optimization, was used as an optimization tool. The optimized performances of the heater core were compared with performance target, and finally, the improved designs of the heater and the evaporator were presented.
Protection Switching Methods for Point-to-Multipoint Connections in Packet Transport Networks
김대업,류정동,이종현,김병철,이재용 한국전자통신연구원 2016 ETRI Journal Vol.38 No.1
In this paper, we discuss the issues of providing protection for point-to-multipoint connections in both Ethernet and MPLS-TP-based packet transport networks. We introduce two types of per-leaf protection—linear and ring. Neither of the two types requires that modifications to existing standards be made. Their performances can be improved by a collective signal fail mechanism proposed in this paper. In addition, two schemes—tree protection and hybrid protection—are newly proposed to reduce the service recovery time when a single failure leads to multiple signal fail events, which in turn places a significant amount of processing burden upon a root node. The behavior of the tree protection protocol is designed with minimal modifications to existing standards. The hybrid protection scheme is devised to maximize the benefits of per-leaf protection and tree protection. To observe how well each scheme achieves an efficient traffic recovery, we evaluate their performances using a test bed as well as computer simulation based on the formulae found in this paper.
김대업,엄현서,정광하,박흥복 한국정보통신학회 2001 한국정보통신학회논문지 Vol.5 No.3
현재 국내의 산업 자동화 관련의 온실 환경 제어 시스템은 노동 집약적 시설에 타이머를 이용하여 각 장치를 제어하는 on/off식 제어반으로 구성되어 있다. 그러나 이러한 시스템은 야간이나 원격지에 있을 경우에는 온실의 상태 파악이 어렵다. 따라서, 본 논문에서는 기존의 on/off식 제어 방식을 액정 패널로 수동 제어를 하고, 컴퓨터로 수통 및 자동 제어 상황을 모니터링할 수 있는 시스템을 개발하였다. 또한, 재배 작물에 대한 관련 정보를 DB로 구축하여 사용자에게 정보 획득의 편의성을 제공하도록 한다. At present, environmental control system of greenhouses related with industrial automation in the korea is composed of on/off-type control machine using a timer in facilities requiring intensive labor. This system, however, makes it difficult for us to find out any status of environmental control system in greenhouses when we are situated in a remote area or at midnight. In this paper we improved a system to monitor status for manual and automatic control by means of PC by replacing an existing on/off-type controller with a display panel, It also attempts to implement DB for information on corps and to provide a user with the efficiency of getting information for plants.