• Journal of Welding and Joining
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• 제28권1호
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• pp.77-85
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• 2010

Stainless steel sheets are widely used as the structure material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. Gas welding is very important and useful technology in fabrication of a railroad car and vehicles structure.However fatigue strength of the gas welded joints is considerably lower than parent metal due to stress concentration at the weld, fatigue strength evaluation of gas welded joints are very important to evaluate the reliability and durability of railroad cars and to establish a criterion of long life fatigue design. In this paper, $({\Delta}{\sigma}_a)_R-N_f$ curve were obtained by fatigue tests. Using these results, the accelerated life test(ALT) was conducted. From the experimental results, an acceleration model was derived and acceleration factors are estimated. So it is intended to obtain the useful information for the fatigue lifetime of plug and ring gas welded joints and data analysis by statistic reliability method, to save time and cost, and to develop optimum accelerated life prediction plans.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.980-985
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• 2008

Since its invention at TWI in 1991, Friction Stir Welding (FSW) has become a major joining process in the aerospace, railway and ship building industries especially in the fabrication of aluminium alloys. In an attempt to optimize the friction stir welding process of Al alloys for extrusion Aluminium carbody of HEMU-400X (Extrusion Aluminum 6xxx series), effects of joining parameters such as tool rotating speed, plunging depth and dwelling time on the weld joints properties were evaluated. Experimental tests were carried out for butt joined Al plates. A wide range of joining conditions could be applied to join Al alloys for Extrusion Aluminum 6xxx series without defects in the weld zone except for certain welding conditions with an insufficient heat input. The microstructures of welds have dynamic-recrystallized grain similar to stir zone in FSW weld. For sound joints without defects, at the rotation speed of 700 rpm with different welding speeds, the tensile strengths of the Stir Zone(SZ) were almost the same, 80% of those of the base metal. (JIS Z 2201)

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.118-120
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• 2004

Recently 9Cr-1Mo azzoy is used in the Nuclear power plant due to its special properties. This material has the merit of high-strength resistance and corrosion resistance. Therefore the demand for this alloy is dramatically increased in the Nuclear power, petro-chemical complex etc. Re various research has been conducted to improve the material properties of this alloy. In spite of this circumstance, detail research in the area of welding process of this alloy is yet to be expanded In this study the numerical non-linear heat transfer analysis of laser welding which may possibly replace the conventional SMAW fabrication of 9Cr-1Mo steel has been carried out.

• Journal of Welding and Joining
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• 제20권2호
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• pp.50-58
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• 2002

Residual stress is generated in the structures as a result of irregular elastic-plastic deformation during fabrication processes such as welding, heat treatment, and mechanical processing. There are several factors attributed to the origin of residual stresses, tensile or compressive. The stresses can be determined by destructive ways or nondestructive ways using X-ray or neutron diffraction. Although X-ray diffraction is a well established technique, it is practically limited to near-surface stresses. Neutrons penetrate easily into most materials and neutron diffraction permits non-destructive evaluation of lattice strain within the bulk of large specimens because the radiation is more deeply penetrating for metallic engineering components. This paper presented application of neutron diffraction technique to the residual stress measurement using 20 mm thick welded stainless steel plate($100{\times}100 \textrm{mm}^2$)

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2000년도 특별강연 및 춘계학술발표대회 개요집
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• pp.303-306
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• 2000

Quality estimation of the weld has been one of the important issues in RSW which is a main process of the sheep metal fabrication in auto-body industry, It was well known that among the various welding process variables, dynamic resistance has a close relation with nugget formation. With this variable, it is possible to estimate the weld quality in real time. In this study, a new quality estimation algorithm is developed with the primary dynamic resistance measured at welding machine timer. For this, feature recognition method of Hopfield neural network is used. Primary resistance patterns are vectorized and classified with five patterns. The network trained by these patterns recognizes the dynamic resistance pattern and estimates the weld quality Because the process variable monitored at the primary circuit is used, it is possible to apply this system to real time application without any consideration of electrode wear or shunt effect.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.68-68
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• 2009

최근에 자동차 차체 경량화를 목적으로 개발된 고장력강의 용접품질 향상을 위해 인버터 DC 점용접기가 많이 사용되어지고 있다. 본 연구에서는 국내에서 개발된 인버터 DC 용접기를 사용하여 자동차용 590MPa 고장력 냉연강판(CR, SPFC 590RA)과 아연 도금 강판 (GA- EZFFC 590RA)의 용접품질을 평가하였다. 용접에 사용된 기본 조건은 인장 전단 시험을 통하여 결정하였으며, 동저항, 압흔 자국과 너겟 지름, 인장강도와의 관계를 통계적 방법으로 분석하였으며, 이를 활용하여 고장력 강판의 동저항과 압흔 자국에 따라 너겟 지름과 용접강도를 예측하는 비파괴적 용접 품질 평가 방법을 제시하였다.

• 수산해양기술연구
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• 제36권4호
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• pp.322-328
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• 2000

남해안 연근해에서 조업하는 정치망 어선에 양망작업시 보조기계로 사용되는 캡스턴의 드럼에서 용접부 온도분포 및 구배를 해석한 결과의 주요 사항은 다음과 같다. 1. 용융부 근처는 냉각개시 1초 이내에 950$^{\circ}C$/sec, 10초 이내는 40$^{\circ}C$/see 정도의 급격한 냉각속도가 형성되었다. 2. 열영향부(HAZ)는 용접 후 1초가 경과할 때 370$^{\circ}C$/sec의 가열속도로 온도가 증가한 후, 이 후 25$^{\circ}C$/sec 냉각속도로 온도가 감소한다. 용접종료 10초 후 모재 내부에는 1.64$^{\circ}C$/mm, 40초가 지났을 때는 0.26$^{\circ}C$/mm 정도의 온도구배가 형성되었다. 3. 용접부 근처는 길이 방향을 따라 격심한 온도편차를 보이고 있으나 두께방향으로는 거의 나타나지 않는다. 이 결과는 향후 캡스턴 드럼의 용접부 최적설계시, 탄소성 열응력 및 열변형 거동을 해석하는 연구의 기초자료로 활용될 수 있을 것이다.

• 대한조선학회 특별논문집
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• 대한조선학회 2007년도 특별논문집
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• pp.118-127
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• 2007

SAW(Submerged Arc Welding) process is generally applied to a wide range of welding area in the fabrication of steel structure. This process has a good characteristic properties such as the high quality of welds and the high deposition rates, but in case of welding on a thick steel plate, it also has higher cold crack susceptibility than that of a thin steel plate. The purpose of this research is to find the main factor of crack generation and clarify the countermeasure for crack prevention, and then establish the optimum welding condition in a heavy thick steel plate. The results of this study are as follows, 1. The cause of crack generation is found the diffusible hydrogen penetrated into weld metal by decomposition of the remained moisture in SAW flux during welding. 2. For the removal of diffusible hydrogen, the raw materials of SAW flux are to be dehydrated at the high temperature in the initial manufacturing stage. 3. Mechanical properties of weld metal welded with the dehydrated SAW flux were evaluated very excellent, furthermore the weld metal has been proved to have low diffusible hydrogen content with 3.1ml /100g. 4. The weldability and quality welded with thick steel plates were improved by establishing the new optimum welding condition.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.240-241
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• 2003

The iron aluminides have been among the most widely studied intermetallics because of their low cost, low density, good wear resistance, ease of fabrication and resistance to oxidation and corrosion. In this study, weld overlay was performed with JIS-YGW11 and A14043 wire on the base metal.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.72.1-72
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• 1998