• Journal of Welding and Joining
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• 제1권2호
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• pp.45-52
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• 1983

Many pressure vessels for the hot H$\sub$2//H$\sub$2/S service are made of 2+1/4Cr-1Mo steel with austenitic stainless steel overlay to combat agressive corrosion due to hydrogen sulfide. Hydrogen dissolves in to materials during operation, and sometimes gives rise to unfore-seeable damages. Appropriate precautions must, therefore, be taken to avoid the hydrogen induced damages in the design, fabrication and operation stage of such reactor vessels. Recently, hydrogeninduced cracking (or Disbonding) was found at the interface between base metal and stainless weld overlay of a desulfurizing reactor. Since the stainless steel overlay weld metal is subjected to thermal and internal-pressure loads in reactor operation, it is desirable for the overlay weld metal to have high strength and ductility from the stand point of structural safety. In section III of ASME Boiler and Pressure Vessel Code, Post-Weld Heat Treatment(PWHT) of more than one hour per inch at over 1100.deg. F(593.deg. C) is required for the weld joints of low alloy pressure vessel steels. This heat treatment to relieve stresses in the welded joint during construction of the pressure vessel is considered to cause sensitization of the overlay weld metal. The present study was carried out to make clear the diffusion of carbon migration by PWHT in dissimilar metal welded joint. The main conclusion reached from this study are as follows: 1) The theoretical analysis for diffusion of carbon in stainless steel overlay weld metal does not agree with Fick's 2nd law but the general law of molecular diffusion phenomenon by thermodynamic chemical potential. 2) In the stainless steel overlay welded joint, the PWHT at 720.deg. C for 10 hours causes a diffusion of carbon atoms from ferritic steel into austenitic steel according to the theoretical analysis for carbon migration and its experiment. 3) In case of PWHT at 720.deg. C for 10 hours, the micro-hardness of stainless steel weld metal in bonded zone increase very highly in the carburized layer with remarkable hardening than that of weld metal.

• 한국도로학회논문집
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• 제13권1호
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• pp.207-221
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• 2011

국내 고속도로의 60% 이상이 시멘트 콘크리트 포장으로 건설되었으며, 그 중 공용년수가 20년이 넘어선 구간이 절반 이상에 달하고 있다. 노후화된 시멘트 콘크리트 포장의 보수 보강은 국내의 도로 교통여건상 우회도로가 준비되기 어렵기 때문에 조기 교통개방이 요구되며 현재까지는 주로 아스팔트 덧씌우기가 사용되고 있다. 반면에 아스팔트 포장은 조기파손과 잦은 보수 때문에 보수 보강에 대한 비용이 크다. 현 시점에서 아스팔트 덧씌우기가 국내에서 가장 많이 사용되고 있는 현실을 감안할 때, 아스팔트 덧씌우기의 수명에 미치는 영향인자가 무엇인지 검토할 필요가 있다. 따라서 아스팔트 덧씌우기 공법의 성능에 영향을 미치는 인자에 대해 조사할 필요가 있으나, 국내의 경우 아스팔트 덧씌우기의 공용 중 파손상태에 대한 자료가 체계적으로 구축되어있지 않다. 본 연구에서는 아스팔트 덧씌우기 수명과 영향인자간의 상관성을 비교하기 위해 다양한 파손자료를 구축하고 있는 미국의 LTPP data를 이용하여 노후화 된 시멘트 콘크리트 포장의 아스팔트 덧씌우기에 대해 조기파손을 방지하고, 효율적인 보수 보강을 위해서 아스팔트 덧씌우기 구간의 수명에 미치는 영향인자에 대해서 통계분석을 수행하였다.

• 대한기계학회논문집A
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• 제32권10호
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• pp.873-881
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• 2008

Weld overlay is one of the residual stress mitigation methods which arrest crack initiation and crack growth. Therefore weld overlay can be applied to the region where cracking is likely to be. An overlay weld used in this manner is termed a preemptive weld overlay(PWOL). In pressurized water reactor(PWR) dissimilar metal weld is susceptible region for primary water stress corrosion cracking(PWSCC). In order to examine the effect of PWOL on residual stress mitigation, PWOL was applied to a specific dissimilar metal weld of Kori nuclear power plant by finite element analysis method. As a result, strong compressive residual stress was made in PWSCC susceptible region and PWOL was proved effective preemptive repair method for weldment.

• Journal of Welding and Joining
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• 제31권4호
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• pp.62-66
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• 2013

Overlay welding is carried out to improve the corrosion resistance, wear resistance and heat resistance on the surface of the chemical plant and steelmaking plant structures. In overlay welding, control of the bead size and the temperature distribution of weldment are particularly important because that is directly connected to the improvement of quality and productivity. The aim of this study is to model the welding heat source that is very useful to analyze the bead size and temperature distribution of weldment. To find the welding heat source model, numerical analyses are performed by using FE software MSC-marc.

• 한국자동차공학회논문집
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• 제18권1호
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• pp.66-73
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• 2010

This work was focused on the material parameter extraction for the isothermal cyclic deformation analysis for which Chaboche(Combined Nonlinear Isotropic and Kinematic Hardening) and Overlay(Multi Linear Hardening) models are normally used. In this study all the parameters were driven especially based on Overlay theories. A simple method is suggested to find out best material parameters for the cyclic deformation analysis prior to the isothermal LCF(Low Cycle Fatigue) analysis. The parameter extraction was done using 400 series stainless steel data which were published in the reference papers. For simple and quick review of the parameters extracted by suggested method, 1D FORTRAN program was developed, and this program could reduce the time for checking the material data tremendously. For the application to FE code ABAQUS user subroutine for the material models was developed by means of UMAT(User Material Subroutine), and the stabilized hysteresis loops obtained by the numerical analysis were in good harmony with test results.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2006년도 춘계학술발표대회
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• pp.1037-1040
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• 2006

This paper presents an efficient overlay multicast routing protocol (ROMP) and its architecture. ROMP using GPS and region map stands on the basis of scalable 2-tiered multicast architecture and maintains a global overlay multicast tree through reactive fashion. With this approach, the coarse-grain location-awareness for an efficient overlay multicasting and the determination of hot-spot area for efficient data delivery are feasible. The simulation results show that the localized control packets of ROMP prevent the overlay control packets from squandering the physical network resources.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2007년도 한국컴퓨터종합학술대회논문집 Vol.34 No.1 (D)
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• pp.183-188
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• 2007

Peer-to-Peer (P2P) overlay networks have drawn much research interest in the past few years because they provide a good substrate for large-scale applications in the Internet. In this paper, we introduce the use of anycast, a new "one-to-one-of-many" communication method in the Internet, to solve the following common problems of P2P overlay networks: load-balancing, topology-awareness, system partitioning, and multi-overlay interconnection. We also give an analysis of the features and limitations of the recently deployed anycast infrastructures in the Internet for supporting P2P overlay networks.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.401-403
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• 2006

When RF overlay technology is used in EPON-based optical access network, there coexist the directly modulated 1310-nm upstream data, the directly modulated 1490-nm downstream data, and the amplitude-modulated l550-nm downstream broadcast signal based on RF overlay technology. In this paper, we analyze the spectrum of 8B/10B IDLE line code signal and the SRS effect of l490-nm IDLE line code signal on 1550-nm signal. From the result of analysis, we propose a new technique that can be used to improve the CNR of the broadcast signal, which is based on self synchronous scramble method.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.829-841
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• 2014

The main purpose of this study is to determine the effect of overlay on the crack propagation. In order to simplify the problem, a cement concrete pavement is modeled as an elastic plate on Winkler foundation. To derive the singular integral equations, the Fourier transform and dislocation density function are used. Lobatto-Chebyshev integration formula, as a numerical method, is used to solve the singular integral equations. The numerical solution of stress intensity factor at the crack tip is derived. In order to examine the effect of overlay for resisting crack propagation, numerical analyses are carried out for a cement concrete pavement with an embedded crack and a concrete pavement with an asphalt overlay. Results show the significant factors that influence the crack propagation.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.100-102
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• 2006