용접입열량에 따른 CO₂용접부의 기계적 특성에 관한 연구

국정한,성호현 한국기술교육대학교 2001 論文集 Vol.8 No.1

ABSTRACT In this study, we investigate the welding characteristics, mechanical properties, stress intensity, fracture strength, and microstructure in the fusion zone of SS400 steels which were welded at four different heat inputs(10, 15, 20, and 25 KJ/cm) using either the flux cored wire (FCW) or solid wire (SW) in the CO2 welding system. Based on arc's stability, spatter, thinned-slag detachment, and bead apperance results, the mechanical properties of the FCW were much better than those of the SW. They decreased as heat increased. The increase of heat input and notch depth result in a decrease of the impact energy.

이종재료 접합부 선단의 크랙 전파 거동

국정한,성호현,송일규 한국기술교육대학교 1997 論文集 Vol.4 No.1

In this study, the crack behavior around the bonded dissimilar materials is analyzed by using by Finite Element Method(FEM) in case that it approaches or passes through the bonded line perpendicularly. The analysis criterion is based on the energy(△U) when the crack progresses or passes through the bonded line. The variables are the width of dissimilar material and distance from the crack tip to the bonded line. Values of E(Young's modulus), V(Poisson's ratio) and △U(Energy) for base material are different from those(E', V', △U') for dissimilar material. The outcome of this study is obtained by comparing △U with △U'

SS400강 용접부의 파괴인성치에 관한 연구

국정한,송일규,김봉중,오세용,성호현 한국기술교육대학교 1999 論文集 Vol.6 No.1

In this work, we studied the mechanical properties, structure and the stress intensity factor of the welded areas which were annealed from 500。C to 900。C with an interval of 100。C. The main results are as follow. 1. The as-welded specimen showed the highest tensile strength and yield point. The tensile strength and the yield point decrease as the annealing temperature increased from 500。C to 900。C, and they became smaller in the order of deposited metal, heat affected zone and base metal. 2. The hardness was maximum at about 9 mm from the welding center line, and it decreased drastically in the heat affected zone located between 9∼15mm from the center line. 3. The elongation decreased in the order of base metal, the fusion zone and heat affected zone while it increased as annealing temperature increased. 4. The stress intensity factor(S. I. F.) declined as the length of notch increased and it became smaller in the order of fusion zone, base metal and heat affected zone. This is because fracture toughness is affected by brittlization at heat affected zone as well as the initiation and propagation of cracks.

고온에서 회전하는 터빈엔진 디스크의 응력해석

황수철,국정한,조재웅,하영민 한국공작기계학회 1995 한국생산제조학회지 Vol.4 No.4

This study includes thermal plasticity analyses for a turbine rotor with the simple geometry and the boundary conditions. When centrifugal or thermal stress are applied at the high temperarture material of engine blade, stress distributions in material σ_rr, σ_θθ, τ_rθ. Mises stress) are analyzed by computer simulation(ABAQUS) as followings; 1. The maximum stress at the radial direction (σ_rr) is applied at the upper middle part of spline hole. 2. The maximum stress at the tangential direction (σ_θθ) is applied at the upper right boundary of spline hole. 3. The maximum shear stress (τrθ) in (-) direction is applied at the upper middle part of spline hole. 4. The maximum Mises stress is applied at the upper right boundary of spline hole. This stress is due to the critical stress by which rotor can be fractured according to elapsed time.

C++를 이용한 통신 시뮬레이터의 설계 및 구현

이광휘,정상국,안정희,김한경,이종근 國立 昌原大學校 精報通信硏究所 1998 精報通信論文集 Vol.2 No.-

In this paper, we are designed and implemented communication simulator, for two systems which communicates in peer-to-peer and simulating for protocol, to verify the interwork not yet designed system Peerl and now being operated Peer2. To begin with, after the investigation in Interworking Standard in Interface Control Document and check the satisfied requirements in each system, the environment of simulator is set up. We examine Interworking Standard in FSM representation. And in protocol design, partial steps follows necessary procedure of protocol engineering. Simulator is implemented in C++ and, to interwork two systems smoothly, the whole system will be merged. Finally, a design and implementation of simulator is completed by confirming simulation results of simulator and Interworking Standard coincide.

TiAIN 코팅 평 엔드밀의 성능평가에 관한 기초 연구

유중학,국정한,김문기 한국공작기계학회 2001 한국생산제조학회지 Vol.10 No.5

The purpose of this study is an evaluation of flat end mills to develop appropriate tools for the high speed machining. First of all, several flat end mills which are produced by different markers are selected to analyze the performances of the tools. Experimental works are also executed to measure cutting force, tool wear and surface roughness for different cutting conditions. And then the results are compared and analyzed for developing optimal cutting tool in the high speed condition.

복합 재료 접합부의 크랙 전파 거동

김영배,국정한 韓國技術敎育大學校 1995 論文集 Vol.2 No.1

Recently, with the increasing use of reinforced composite materials as structure components, the study on fracture strength of composite materials has received wide attention. The stress intensity factor at the tip of the crack, and the stress of crack tip between the matrix and reinforced material are discussed. From the results it was concluded that : Variation of stress intensity factor is increased as the elastic modulus rate between base material and composite material is increased. And the crack propagation rate decreased or increased according to the position of composite material.

소성변형 부위에서의 피로크랙전파

성호현,송일규,국정한 한국기술교육대학교 1998 論文集 Vol.5 No.1

In this study, the behavior of a fatigue crack propagation near the expanded hole was investigated in terms of the plastic deformation and position of hole with respect to the propagating crack tip. The results of this study are summarized as follows. 1. The crack propagation rate is high when the crack tip approaches the hole but the retardation effect becomes prolonged when the crack tip is at the very vicinity of the hole. 2. The proper expansion of the hole seemed to play an important role for the retardation of the fatigue crack propagation rate. It is found that 5% of plastic deformation in mild steel show the best effect of the fatigue crack retardation.

이종 재료 접합부의 응력확대계수

김문기,국정한,유중학,성호현 韓國技術敎育大學校 1996 論文集 Vol.3 No.1

In this study, fracture aspects for dissimilar materials welded by right and left or up and down in symmetry are examined by using Finite Element Method(FEM) in case that holes exist at up and down in symmetry for the center of crack, and the results of this study are as follows ; 1. When the strength(E₁) of a material with a center crack is lower than that (E₂) of the dissimilar material which is welded by right and left in symmetry, the crack propagation rate decreases by about 25%, while it increases by about 20% when the E₁ is higher than E₂. 2. When the E₁ is lower than the E₂ which is welded by up and down in symmetry, the crack propagation rate decreases by about 25% while it increases by about 75% when the E₁ is higher than the E₂. 3. The value of K₁/K?? is constant up to 2.0 in which is the ratio (a/R) between crack length and hole radius, and the value is decreased or increased a little above 2.0. It is regarded that a phenomenon of crack closure is applied according to the welded type of dissimilar material. In addition, It is noticed that retardation effect of crack propagation is changed greatly according to the distributed position of dissimilar material.

홍삼 엑기스를 함유한 분말주의 제조 및 평가

이사원,최한곤,박정일,김종국 영남대학교 약품개발연구소 2000 영남대학교 약품개발연구소 연구업적집 Vol.10 No.-

To develop a dry alcohol containing red ginseng extract, dry alcohols composed of ethanol, water, dextrin and sodium lauryl sulfate were prepared using spray dryer, and their ethanol contents and encapsulation efficiencies were deter-mined. An optimal dry alcohol containing red ginseng extract was chosen and the feeling for its oral administration was eval-uated. Dextrin at dextrin/water weight ratios below 1.6/1 and ethanol at ethanol/water weight ratios below 1/1 remarkably increased both the ethanol contents and encapsulation efficiencies of dry alcohols. However, dextrin at dextrin/ water weight ratios above 1.6/1 and ethanol at ethanol/water weight ratio above 1/1 slightly decreased the both parameters. It might be due to the low solubility of dextrin in ethanol and limited diffusion coefficient of ethanol to the dextrin shell. Furthermore, 0.5%(w/w) sodium lauryl sulfate gave the maximum ethanol content of dry alcohol. The more increased amounts of red ginseng extract were added, the more increased amounts of ginsenoside Rb1 but the more decreased amounts of ethanol were encap-sulated in dry alcohols. A dry alcohol containing red ginseng extract was prepared with dextrin/ethanol/water(1/1/1, w/w/w) mixed solution, in which 0.5%(w/w) sodium lauryl sulfate and 20%(w/w) red ginseng extract were dissolved. It contained the ethanol contents of 31.17±1.33%(w/w) and ginsengoside Rb1 of 243.0±7.0㎍/g. It gave the moderate taste of red ginseng extract at its oral administration with or without water. Thus, the dry alcohol containing red ginseng extract can be further developed as a more convenient dosage form for red ginseng extract.