• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.161-168
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• 2010

A series of fatigue tests have been performed on the non-load carrying fillet welded joints in order to quantitatively assess the fatigue characteristics due to the grindings and TIG(Tungsten Inert Gas) welding treatments. From the results of fatigue tests, it has been shown that the fatigue strengths at $2{\times}106$ load cycles were improved in the case of the grinding sand TIG welding treatments, and we could know that it is satisfying fatigue strength prescribed in fatigue design standard in general. Besides, from the results of fracture mechanics approaches, the geometric shape correction factors were the most dominant factors in the initial fatigue crack growth, but as the fatigue crack develops, the finite plate correction factor were became the most dominant factor, and the fatigue life on non-load carrying fillet welded joints could be relatively exactly estimated by using the relations between fatigue crack growth rate and stress intensity factor obtained from finite element analysis and existing proposed formulae.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.165-167
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• 2004

마찰교반접합(FSW, Friction Stir Welding)은 영국 TWI에 의해 1991년에 개발되어 특허가 출원된 후 90년대 중반부터 산업에 적용되었으며, 짧은 시간동안에 실용화가 이루어졌다. 이 기술이 적용되기 전, Al 합금의 접합은 MIG(Metal Inert Gas)나 TIG(Tungsgten Inert Gas)와 같은 접합이 주로 이용되어 왔으나, 이들 접합기술은 접합부의 표면문제, 변형, 결함 등으로 인하여 Al 합금의 구조물 적용에 큰 문제점이 야기되어왔다. (중략)

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.39-41
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• 2004

This study is to optimize the condition of pulse parameters using the response surface method in micro pulse TIG welding of pleated type metallic filter. The input parameters used were pulse current, base current, pulse duty, frequency and welding speed and the hydraulic pressure was used as the output parameter. The central composite design was designed using second order regression model, As the results, the optimal welding condition to manufacture the pleated type metallic filter was obtained.

• Journal of Welding and Joining
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• v.28 no.6
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• pp.21-27
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• 2010

Due to excellent weld quality, orbital welding with TIG is widely applied to pipe welding. But concave back bead is formed easily in overhead and inclined-up position of butt orbital welding. It is difficult to find a paper to overcome this problem. In this study, in order to make convex back bead in overhead and inclined-up position of pipe 5G welding, control method of molten pool was actively investigated. Melt run welds were conducted on thickness 4.0mm SS400 with overhead and inclined-up position and was observed the variation of bead shape after welding with the bead former developed. The height of back bead showed the trend of increase as the distance from molten pool to the bead former was decreased. Also, there is no trend in the bead width of front and back as welding position was changed or the distance from molten pool to the bead former was decreased.

• Journal of Welding and Joining
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• v.29 no.3
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• pp.51-57
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• 2011

Bead shape control with gas force process has been developed to overcome the concave back bead in pipe orbital welding. However, It is impossible to make a convex back bead using the existing gas nozzle, because it has high gas-consuming and low gas force. The purpose of this paper, to develop optimum shape of nozzle which to reduce the consumption of gas, maximizing the shield gas force with low cost and high productivity coincide the Green welding. In this paper venturi-type nozzle was designed by using the Venturi meter and compared velocity, pressure, arc shape in the flat position with existing CP-nozzle. As a result, Venturi-type nozzle's maximum velocity and pressure was improved at the same flow rate. Also heat input was increased by the arc contraction in the flat position.

• Fire Science and Engineering
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• v.26 no.3
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• pp.60-66
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• 2012

In this study, it was evaluated the fire risk during welding cutting tasks. Welding-cutting machines are representatively used at construction sites. Inverter AC/DC TIG welding macnine and inverter air plasma cutting machine were used in experiments. Temperature of spreaded cinders was measured using a thermal camera. Cinder sizes and spread range were measured according to the height and input current. It was also evaluated the fire risk during welding-cutting process, when flammable materials were located around the working area. There were used hay, dust fence, urethane foam, vinyl, paper and oil as flammable materials. Temperature of spreaded cinders was reached at about $450^{\circ}C$. Cinders were spread approximately 4.7 m, when a worker carried out cutting process at 2.5 m height. The possibility of a fire is very high, when flammable materials were located around the working area.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.106-111
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• 2014

Welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength. In this paper, TIG welding technique was performed to investigate the joint characteristics of AISI321 steel. For its evaluation, the orthogonal array method and variance analysis were applied with three factors of electric current, travel speed and argon gas and also three levels of each factor to tensile tests for optimum design. From the results, the increaser weld speed the narrower bead width and the lower weld penetration. The increaser electric current the brighter argon gas and the wider bead width. Also weld speed influenced most on the tensile strength and presumption range of tensile strength at optimal condition from reliability 95% was estimated to $635.02{\pm}14.64$. In addition the increaser weld speed and electric current the fracture occurred around bead vicinity.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.515-519
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• 2011

Structural tests for the mixing head of a 75tonf class thrust chamber were performed to verify structural stability. The mixing head of a thrust chamber is loaded by high pressure with regeneratively cooled fuel and cryogenic liquid oxygen(LOx) as well as it transfers thrust load generated by liquid rocket engine. Therefore structural stability of mixing head is a very important factor to work without any plastic deformation or structural failure. In this study, two mixing heads were manufactured using different welding methods, Tungsten Inert Gas(TIG) welding and Electron Beam Welding(EBW) and evaluated a structural stability. The results of structural tests showed that the mixing head assembled by EBW can withstand the applied design load without any structural failures and be structurally more stable than that of TIG welding.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.81-89
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• 2018

Austenitic stainless steels have excellent corrosion resistance, durability and fire resistance. Especially, since STS304L among austenitic types is a low-carbon variation of STS304 and has excellent intergranular corrosion resistance, it can often be used under the welded condition without heat treatment after field welding. This paper investigated ultimate behaviors such as ultimate strength and weld metal fracture mechanism of STS304L fillet-welded connections with TIG(tungsten inert gas) welding through test results. Main variables of specimens are weld length and welding direction against loading. Fracture of specimens are classified into three modes(tensile fracture, shear fracture and block shear fracture). Ultimate strengths were compared according to the welding direction and weld length and TFW series with transverse fillet weld had the highest strength compared with other types(LFW series with longitudinal fillet weld and FW series with all round weld). It is known that current design specifications such as KBC 2016 and AISC2010 underestimated the strength of TFW and LFW specimens and provided unconservative estimates for FW specimens. Finally, strength equations were proposed considering material properties of STS 304L material.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.476-479
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• 2011

티타늄 합금은 높은 내부식성, 우수한 피로 수명과 무게비에 비해 높은 강도를 가진다는 우수성으로 인해 항공기 부품과 화학 공업 분야등에 다양하게 사용되고 있다. 이번 연구에서는 Ti-3Al-2.5V 합금 TIG 용접부에 대하여 용접부 인성과 기계적 성질에 영향을 주는 가장 중요한 인자인 용접 입열에 대한 영향을 평가하고자 하였다. 이에 입열조건에 대한 용접부에 대한 강도, 충격 인성과 노치 인성을 평가하였으며 적정 입열 조건에서 강도와 인성이 우수한 용접부를 얻을 수 있다는 것을 확인하였다.