Rapid Consolidation of WC‑ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.9

Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4was fabricated by spark plasma sintering at 1400 ℃ ata constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried outfor 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. Itwas observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents,and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact wasfound to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical propertiesof the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to thepresence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zirconfrom a transgranular to a ductile component (fcc) where the crack tips could be absorbed.

Influence of Phase Composition in TiAlSiN Hard Coatings on the Evolution of Structure and Mechanical Properties

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.3

The aim of this study is to investigate the structural evolution and mechanical properties of TiAlSiN coatings when processedby the arc ion plating method. To form a hard coating, Ti, Al, and Si powders were mechanically alloyed by planetary ballmilling; the powders were then densely compacted during a rapid sintering process into a ternary system coating, i.e. TiAlSi. The evolution of the structural phase from a powder to a compact material is dominated considerably by phase states suchas a supersaturated solid solution or intermetallic compounds. In the case of coating layers, the factors that determine thestructural evolution are associated with the phase stability of the nano-crystalline structure that in turn is associated withthe Ti/Al composition ratio. Motivated by this, we performed experiments to investigate the distribution of microstructures;the material’s binding energy, quantitative properties, transformation of crystal structure, and distribution of amorphous/crystalline were all recorded. In particular, the relationship between the physical and chemical properties during the coatingprocess is considered to be the dominant factor controlling the orientation and morphology of that zone (1, T, and 2). TheTiAlSiN coating layer was found to have hardness above 45 GPa and an adhesion above 100 N. In other words, understandingthe evolution and structure of TiAlSin helped us to produce a material with excellent properties that can be used as a hardcoating. Specifically, these properties were induced by a grain refinement of the nano-crystalline structure that correspondsto an increase in the silicon nitride contents.

Effect of Mechanical Alloying on the Microstructural Evolution of Al60Cr30Si10 Alloys Processed by Spark Plasma Sintering

Jeong‑Han Lee,Ik‑Hyun Oh,Jun‑Ho Jang,Ju‑Hun Kim,Sung‑Kil Hong,Hyun‑Kuk Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

In this study, Al, Cr and Si fine powders were alloyed by planetary ball milling to investigate their microstructural evolution,following their mechanical alloying behavior. The formation of Al(Cr) supersaturated solid solution by the Cr grainsembedded in Al-matrix, which contributed substitutional structure is discussed in relation to their structural evolution inaccordance with the distortion of a crystal lattice. The compacts of Al–Cr–Si alloys were prepared by rapid sintering withina short time by dense consolidation above the density of 99.9% as the formation of intermetallics, except in the case of thedistribution of single-phases induced by the Al-melting. The formation behavior of intermetallics was dominated by dependenceon the structures of the milled-powder and subsequent sintering temperature. To estimate the consolidated behaviorsof compacts, various approaches derived from TEM and XRD analysis were taken to obtain microstructural evidences ofthe inter-diffusion, following the presence of thermally stable intermetallics.

과도 절삭에서의 절삭 공정 시뮬레이션

고정훈,조동우,윤원수,김주한 한국공작기계학회 2001 한국공작기계학회 춘계학술대회논문집 Vol.2001 No.-

In most of the existing mechanistic models, the cutting process simulation is often restricted to a single path machining operation under a fixed cutting condition. Complex cutting processes such as die or mold manufacturing, however, are performed under two- or three-dimensional multiple tool paths. Since the tool paths in CNC machining are composed of line and arc segments, transient cuts are frequently occured due to the multiple paths. Even in steady cuts, the width of cut is varied with each segment. In this regard, this paper deals with the development of process simulation system for transient cuts, where continuously changing cutting configuration is computed, and then the cutting forces are predicted.

분자역학적 방법을 이용한 부산시내 대형건물 냉각탑수의 레지오넬라균의 형별 분류

김정만,정석훈,서대영,박은희,송은주,최재철,이은엽,장철훈 대한임상미샐물학회 2004 Annals of clinical microbiology Vol.7 No.1

강교량의 수요·공급 변동률과 낙찰율 변동 관계 추정모델

이정훈,김경주 중앙대학교 기술과학연구소 2003 기술과학연구소 논문집 Vol.33 No.-

1997년 외환위기(IMF)이후 강교량 발주물량은 감소하였으며, 반면 강교량 관련 제작업체의 수는 증가하였다. 이는 강교량의 수요와 공급의 불균형으로 이어져 강교량 하도급단가 하락에 영향을 미치게 되었다. 이러한 요인을 수요와 공급 측면에서 조사 분석하였으며 이를 위해 연도별 하도급단가 변화추이와 공급측면에서의 철강재설치공사업체의 등록추이, 수요측면에서의 교량용 강재소비량, 물가지수와의 관계를 각각 비교하여 이러한 요인들이 강교량 하도급 단가에 미치는 영향과 이들의 상관관계를 조사 및 분석하였다. 그 결과 강교량의 수요와 공급의 불균형은 강교량 하도급단가의 변화에 영향을 미치는 것으로 나타났다. After the Korean economic crisis in 1997, steel bridge contract quality was reduced while the number of factories related to the steel bridge production was increased. It led to the imbalance of the steel bridge supply &emand and affected to the steel bridge subcontract price. This study investigated the dffect contract price in aspect of supply &emand. For this purpose, annual subcontract price change, steel bridge production factory’ number, quantity of steel bridge construction, and the price index were compared respectively and the effect of these components to the subcontract price of steel bridge was analyzed. Analysis shows, the imbalance on supply &emand the steel bridge affects to the subcontract price change.

GPS를 이용한 버스안내시스템 개발에 관한 연구

김주현,정영훈 안양대학교 산업기술연구소 2001 自然科學硏究 Vol.8 No.-

최근 ITS의 활성화와 기술의 발달로 인해 실시간 교통자료를 수집하여 동적정보를 생성하는 것이 가능하게 되었다. 이에 본 연구는 정적정보인 노선안내 뿐 만 아니라 동적정보인 도착예정시간, 최단 여행시간 경로를 제공할 수 있는 버스안내시스템을 개발하는 것이 목적이며, GPS를 이용한 버스안내시스템을 개발하였다. GPS를 이용하여 버스의 통행자료를 실시간으로 수집하고, 이를 토대로 통행시간을 예측하며 출발지로부터 목적지까지의 최단여행시간 경로를 제공할 수 있다. 예측의 경우, 요일별, 시간대별의 패턴데이터를 이용하며 본 연구에서 제안한 예측기법을 통해 통행시간을 예측하고 적용 및 검증은 단일노선에 대하여 링크 통행시간 예측의 검증과 복합경로 네트워크에서 최단여행시간경로에 대해 검증을 실시하였다. 링크통행시간 예측의 검증 결과 시간의 흐름에 따라 변하하는 통행시간에 대하여 가장 최근 통행시간에 가중치를 두고 반영하는 본 연구의 예측기법이 표준평균법이나 이동평균법에 비하여 신뢰성있는 예측결과를 나타내었다. Recently it is possible to make dynamic information through the coolection of real-time traffic data because of the development of equipment and the activation of ITS(Intelligent Transport System). The purpose of this research is to develop the Bus Information System which offer not only the route guidance on static information but also the research planned time, shortest path of journey time on dynamic information and developed Bus Information System using Global Positioning System(GPS). This System is able to offer the shortest path of travel time from origin to destination because the trip data of bus collect by real time and base on travel time predict using GPS. In predict case, it is to use pattern data by days and time and then predict travel time of future through proposed predict method on this research. Inverification result of link travel time, the method predictionn of this research which reflected recently weighting travel time according to stream of time for travel time have appeared the credibility than method of standard average or method of moving average.

대기 중 휘발성 유기화합물의 Advanced Technology에 대한 실험비교

최금찬,안병주,김석택,김찬훈,정창훈,서정민,유수영 동아대학교 환경문제연구소 2000 硏究報告 Vol.23 No.1

Nowaday, Advanced technology has been applied to organic destruction technologies that are alternatives to incineration. Plasma, photolysis, and Photocatalytic oxidation processes are an emerging advanced technologies for the abatement of volatile organic compounds(VOCs) in atmospheric pressure air streams, so we has been used these technologies for destruction of VOCs. TCE, Benzene, Toluene, and Xylene were selected as objective materials. We have been studied each process and found many types of reaction parameters which effect on treatment efficiency. So combination processes, which are plasma-photocatalytic oxidation process and photolysis-photocatalytic oxidation process, have been used to increase destruction efficiency. Analysis of above materials and byproducts was carried out by GC-FID.

강선 이음형 PC 보-기둥 내부 접합부의 구조적 거동에 관한 실험적 연구

하상수,김승훈,문정호,이리형,임주혁 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)

In this study, new moment-resisting precast concrete beam-column joint is proposed for moderate seismic regions. it is attempt to devise connection detail which makes workability improve and confirm effective stress transfer in the region of connection. It has the connection details which help working process simplified and construction cost reduced. as replace 9.3㎜, 7strand for reinforcement. Fore specimens for partial tension test and three specimens for beam-column interior joint test were producted. An experimental study was carried out to investigate the joint behavior subjected to reverse cyclic loading and constant axial compressive load. The test variables was transverse reinforcement in joint. Structural performance of joint is evaluated on the basis of connection strength, stiffness, energy dissipation, and drift capacity. Based on the test results, the precast connection is capable of matching or exceeding the performance of the monolithic connection and thereby provides the sufficient moment-resisting behavior to be applicable for moderate seismic regions.

측정오차와 외란을 고려한 유도전동기의 강인한 속도제어에 관한 연구

蔡英茂,尹炳道,金燦起,鄭憲主 충주대 산업과학기술연구소 1995 産業科學論文集 Vol.3 No.-

It is difficult to control industrial drive systems because of load disturbance, parameter variation and measurement noise. So a theorem is required to have robustness for the measurement noise and disturbance. This paper is among the researches of solving these problems. Sliding mode state observer is robust for measurement noise, modeling-error and load disturbance. The pole of sliding mode state observer can be placed at (0,0) in Z-plane for fast response. This method is, namely, deadbeat control. One side, sliding mode state observer output is discontinuous on a switching hyperplance, that causes harmful effects such as current harmonics and speed oscillation. In this paper, also the reducing method of the chattering of sliding mode state observer output is proposed. In this paper, the method of designing a robust sliding mode state observer taking account of the ability of disturbance and noise attenuation is proposed. Also, the proposed control system is digitally implemented with TMS320C31.