• Journal of Welding and Joining
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• 제32권3호
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• pp.102-107
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• 2014

Boiler equipment in power plant is always being operated in harsh conditions and severely exposed to the extreme environment of high temperature. Therefore periodically the state of devices should be checked, diagnosed, and analyzed to ensure the reliability of the equipment. Traditionally, such a diagnosis is based one or two physical properties of the sample taken from the equipment like hardness, microstructure, etc.. However, to enhance the confidence of the diagnosis, it is necessary to synthesize those properties together. This paper is to propose such a synthetic procedure for SA213-T12(1Cr-0.5Mo) which was developed to be used in $565^{\circ}C$ below condition. Creep test and accelerated degradation test were performed simultaneously, and the physical properties such as microstructure, tensile strength, yield strength, hardness, and indentation properties were measured. This paper proposes a method of determining the remaining life by quantitative comparison. It will provide the basis of evaluating life assessment more objective and reliable.

• Journal of Welding and Joining
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• 제17권6호
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• pp.53-61
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• 1999

The use of thick plate in increasing in recent years due to the rapid expansion of chemical plants, nuclear plants, ships and other industrial plants. Welding is the most popular joining techniques employed in manufacturing industrial machineries and structures. Normally, Groove shapes are prepared according to appropriate rules and regulations such as KS, JIS, AWS, LR, DNV and etc. for various thicknesses of plate. However those groove angles tend to be too large. As a result of large groove angle, residual stress, deformation of material and strength reduction is obtained. Therefore, the reliability and safety of structures and machinery tend to be decreasing. Therefore, in this paper, theoretical as well as experimental study are carried out to find optimum groove shapes for T-welded joint of mild steel. The test specimen are made in same condition with simulation model. Welding residual stresses measurement by sectional cutting method. ⅰ) The mechanical difference for change the thickness of plate and groove angle are not appeared. ⅱ) In a mechanical point of view minimum preparation angle(40°) is more suitable than maximum groove angle(60℃). ⅲ) The measurement value and distribution of welding residual stresses are not effected largely by groove angle. It is mechanical restraint that mainly affect welding residual stresses distribution. In mechanical point of view minimum groove angle is more suitable than maximum groove angle. Therefore, it is appropriate to minimize the size of groove shape in strength and safety.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 1999년도 춘계 학술논문발표회 논문집
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• pp.201-206
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• 1999

The influence of surface preparation methods after plasma cutting on the quality of welding zone is investigated. For comparison. three types of welded specimens are prepared by machining(YM), plasma cutting with light regrinding(WPG) and without regrinding(WP), by using three kinds of materials, carbon steel(S45C), stainless steel(Type304) and aluminum alloy (6061-T6). Nondestructive examination, hardness test, microstructure examination, and fracture toughness test are performed. The results show that there is no appreciable reduction in hardness or fracture toughness in WP specimens. But a little difference in heat affected gone size is observed.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2011년도 추계학술논문집 2부
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• pp.478-480
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• 2011

The increasing interest in the hot cracking behavior of the high alloy metal weldment is placing stringent demands on the manufacturing techniques and performance requirements, and the manufacture employs the high quality and efficiency high alloy metal welding technology. This paper covers recent research trends of the hot cracking behavior of the high alloy metal weldment including the SCI-E analysis of published papers, research subjects and research institute analysis.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.293-295
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• 2004

For the evaluation of corrosion resistance, Al 6061-T6 alloy was welded by Friction Sti. Welding(FSW) and Gas Metal Arc Welding(GMAW) evaluated by Tafel method and immersion test. The Tafel and immersion test results indicated that GMA weld was severely attacked compared with those of friction stir weld. It may be mainly due to the galvanic corrosion mechanism act on the CMA weld.

• 비파괴검사학회지
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• 제13권2호
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• pp.11-19
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• 1993

원자력발전소의 주요 압력용기 용접부에 대한 초음파검사시 결함의 특성과 형태에 대한 정확한 분류는 원자력 발전소의 안전성을 확보하기 위한 결함평가에 중요한 요소이다. 본 연구에서 초음파검사에서 얻어진 결함신호를 digital signal processing 기법으로 처리하여 결함의 특성과 형태를 구분할 수 있는 feature vector를 추출하고 결함의 형태를 형상 인식법을 사용하여 분류 하였다. Training specimen(slit, hole)의 신호와 testing specimen(crack, slag)의 신호를 구분하기 위한 실험에서 사용된 통계적 pattern recognition algorithm은 minimum distance classifier와 maximum likelihood classifier이다. 이러한 형상 classifier를 이용하여 결함의 특성을 정량적으로 분류하여 결함 평가 능력을 향상시켰다.

• Journal of Advanced Marine Engineering and Technology
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• 제17권4호
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• pp.100-106
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• 1993

A study on optimizing the friction welding of copper(C1100) to aluminium(A1050) for developing the electrical sleeve was experimentally carried out and also on real-time nondestructive evaluation of the friction weld quality (strength) was accomplished by acoustic emission technique. The results obtained are summarized as the following ; 1) The heating upset $U_1$(mm) or total upset U(mm) tends to increase according to the increase of heating time $t_1$(sec). The relations between $U_1$ and $t_1$ or U and $t_1$are computed as follows when n=2000rpm, $P_1$=4, $P_2$=8kgf/$mm^2$, and $t_2$=6sec. U=1.6$e^{0.39t_1}$ $U_1$=3.65$e^{0.25t_1}$. 2) It was notified that the proper welding conditions by considering on both strength with more than 100% joint effieciency and toughness are heating time of 1.5-2.25 sec under n=200rpm, $P_1$=4, $P_2$=8kgf/$mm^2$, $t_2$=6sec. 3) It was confirmed that both AE total counts(N, counts) and the weld tensile strength (${\sigma}$, kgf/$mm^2$) of the welded joints increase as the increase of heating time, respectively, the relations between N and $t_1$, ${\sigma}$ and $t_1$ are computed from data points by regression analysis using the least square method as follows in case of the above proper condition ; N=50108+23917(ln $t_1$)${\sigma}$$=11.85+2.06(ln $t_1$). 4) Both empirical and calcularated equations of relationship between .sigma. and N are very coincident with a high reliability, as the following in case of the above proper welding condition ; Calculated : ${\sigma}$=0.00008N+7.5 Empirical :${\sigma}$= $8.17e^{0.0000072N}$. 5) It was confirmed that the real-time nondestructive weld strength evaluation for friction welding of copper(C1100) to aluminium(A1050) could be possible by acoustic emission technique.

• 한국강구조학회 논문집
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• 제30권1호
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• pp.13-23
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• 2018

단면을 자유롭게 제작할 수 있는 Built-up H형강(BH)의 사용이 점점 증대하고 있다. 본 연구는 BH의 규격화를 위한 기초연구로 SM490, SM520 강재의 항복강도, 인장강도, 연신율, 샤르피 흡수에너지 등의 소재특성을 확인하였다. 또한 single-SAW 및 tandem-SAW를 활용하여 6개의 BH 공시체를 제작하였으며, 공시체에서 매크로시험편, T바 인장실험체를 채취하여 용접성능을 확인하였다. 소재특성시험 결과 국내산 SM490, SM520 강재의 특성은 모두 KS를 만족하였으며, 용접성능실험 결과 BH의 용접부는 충분한 용접성능을 갖추었다고 판단할 수 있다. 따라서 본 연구에서 사용된 국내산 SM490, SM520 강재는 BH의 소재로 적합한 것으로 판단되며, single-SAW, tandem-SAW는 충분한 용접성능을 발휘하는 것으로 사료된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.830-835
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• 2007

In this paper, stress analyses using shell and solid elements on weld zone of railway bogie frame were performed. To calculate stress distribution on weld zone, a coupling model using shell and solid elements was suggested. For this purpose, we performed specimen analyses on T-type solid and shell model of T-type panels which were modeled using shell elements, solid elements and coupled elements, respectively. The result showed that the stress concentration at weld zone was occurred in solid model, but it didn't occur in shell model. And the stress distribution of coupled model was similar to that of solid model. Also, we applied the coupled modeling method on the analysis on weld zone of bogie frame. The stress distribution of coupled model showed much higher compared to that of shell only model. Therefore, the coupled model method is highly recommended for the stress analysis in weld zone of bogie frame.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.1058-1062
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• 1996

The assessments of weld defects by fracture mechanics are performed for design of welded Joints. In general, butt, T-type, and L-type welded joint are useful for welding structure. When linear weld defects are in welded joint, stress intensity factors for each joints are calculated by finite element method. Analysis results are shown for the fracture modes and characteristics of joint types. And they are founded for the weaken order of welded joints being T-type, butt, L-type.