• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
• /
• pp.155-161
• /
• 2001

Currently knowledge of strain in welds has mainly been obtained from strain gaging method; that is directly attaching most of the material to the gage. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemistry, food instrument and electronic appliances.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
• /
• pp.763-768
• /
• 1998

방사성동위원소 생산용 표적을 중성자 조사하기 위해 하나로의 제반 특성을 고려하여 조사용기를 개발하였다 IP(Isotope Production), HTS(Hydraulic Transfer System) 조사공별로 내.외부용기를 제작하였으며 재료는 검증된 Al-1050을 사용하였다. 내부용기는 냉간용접(Cold Welding) 하고, 외부용기는 TIG(Tungsten Inert Gas) 또는 전자빔으로 용접한 후 He을 충진하고 밀봉하였다. 조사용기의 건전성을 입증하기 위해 기포누설시험, 내압시험, 가열시험, 침투탐상시험, He 누설시험을 수행하였다. 기포누설시험 결과 내부용기는 90% 이상이 3x$10^{-6}$atm.cc/sec 이하의 누설율을 보였고, 내압시험 결과 파단압력은 28kg/$\textrm{cm}^2$ 정도였다. 외부용기는 TIG 용접시 70%, 전자빔 용접시 90% 이상이 누설율 1x$10^{-8}$atm.cc/sec 이하였다. 개발된 조사용기를 사용하여 하나로에서 200여회 방사성동위원소를 생산하였으나 중성자 조사중 누출을 포함한 기타의 문제가 발생하지 않았다. 조사용기 개발에서 확립된 밀봉시험, 내압시험 및 가열시험 방법은 기체표적이나 내압이 발생하는 표적용기의 개발 및 시험에 응용할 수 있다.

• Journal of Welding and Joining
• /
• 제26권4호
• /
• pp.73-78
• /
• 2008

In this paper, research was the variation of microstructure and mechanical properties of clad(A4045/A3003) Al alloy sheet by gas tungsten arc welding. Tensile properties of the gas tungsten arc welding joint decreased because of the softened heat affected zone(HAZ). The hardness of HAZ was lower than that of base metal, because relieved the work hardening effect of the welding heat. Hardness distribution of the weld zone with the base metal appears similarly, but the hardness of HAZ decreased remarkably. The microstructure in the weld zone of A4045 clad layer was formed a coarse columner grains of Si-rich. In the case of large weld heat input, the Si of the A4045 were diffused and until A3003 weld zone they decreased the strength.

• 대한토목학회논문집
• /
• 제28권5A호
• /
• pp.665-672
• /
• 2008

본 연구에서는 교량이나 선박 등의 강구조물에서 널리 사용되고 있는 하중 전달형 십자형 필렛용접 시험편에 대해 피로시험을 실시하여, 용접 후처리 조건에 따른 피로강도를 분석하였다. 용접 후처리 방법으로는 Toe Grinding, TIG Dressing 및 Weld Profiling을 적용하였으며, 피로시험은 일정진폭 반복하중 하에서 실시하였다. 피로시험 결과 하중 전달형 십자형 필렛용접 시험편은 용접 후처리를 실시한 경우와 실시하지 않은 경우 모두에서 BS 피로설계기준의 F등급을 만족하는 결과를 나타내었다. 또한 용접 후처리 방법에 따른 피로강도의 향상 효과는 Toe Grinding, TIG Dressing, Weld Profiling 순서로 증가하는 것을 알 수 있었다.

• 조명전기설비학회논문지
• /
• 제22권6호
• /
• pp.26-33
• /
• 2008

본 연구에서는 일반적으로 용접기의 전원장치로 사용되어지는 풀-브리지 회로에 1개의 스위치와 1개의 무손실스너버 부분 공진 커패시터로 구성된 간단한 액티브 보조 부분 공진 스너버를 추가한 새로운 풀-브리지 소프트 스위칭 PWM DC-DC 컨버터를 제안하였다. 제안한 풀-브리지 소프트 스위칭 DC-DC 컨버터 회로는 각 액티브 스위치에 인가된 전압이 DC 버스 라인 전압의 1/2로 되기 때문에 AC 400(V)계 상용전원 라인에 적용할 경우에도 600(V)내압의 스위칭 소자(IGBT)가 적용 가능하며, 기존 회로의 DC버스 라인 스위치에 발생되는 도통 손실을 저감하여 고주파 변압기의 1차측의 전류가 2차측보다 작아지는 저 전압, 대전류 직류 출력을 얻어 수 있었다. 그리고 모든 영역에서 ZCS/ZVS 동작함으로써 저전압, 대전류 직류 출력의 스위칭 전원 장치에 있어 고주파, 고효율, 고출력을 실현할 수 있다. 이러한 모든 사항은 시뮬레이션과 실험 결과로부터 도출하였으며, 제안한 회로의 단점을 보완할 경우에는 차세대형 TIG MIG MAG 아크 용접기용 전원으로 용이할 것으로 판단된다.

• Journal of Welding and Joining
• /
• 제34권1호
• /
• pp.54-58
• /
• 2016

In this research paper, suggest method of generate same bead as an actual measurement data in virtual welding conditions, exploit morphology information of the bead that acquired through robot welding. It has many multiple risk factors to Beginners welding training, by we make possible to train welding in virtual reality, we can reduce welding training risk and welding material to exploit bead visualization algorithm that we suggest so it will be expected to achieve educational, environmental and economical effect. The proposed method is acquire data to each case performing robot welding by set the voltage, current, working angle, process angle, speed and arc length of welding condition value. As Welding condition value is most important thing in decide bead form, we would selected one of baseline each item and then acquired metal followed another factors change. Welding type is FCAW, SMAW and TIG. When welding trainee perform the training, it's difficult to save all of changed information into database likewise working angle, process angle, speed and arc length. So not saving data into database are applying the method to infer the form of bead using a neural network algorithm. The way of bead's visualization is applying the spline algorithm. To accurately represent Morphological information of the bead, requires much of morphological information, so it can occur problem to save into database that is why we using the spline algorithm. By applying the spline algorithm, it can make simplified data and generate accurate bead shape. Through the research paper, the shape of bead generated by the virtual reality was able to improve the accuracy when compared using the form of bead generated by the robot welding to using the morphological information of the bead generated through the robot welding. By express the accurate shape of bead and so can reduce the difference of the actual welding training and virtual welding, it was confirmed that it can be performed safety and high effective virtual welding education.

• Journal of Welding and Joining
• /
• 제31권4호
• /
• pp.73-79
• /
• 2013

Burr grinding, Tungsten Inert Gas (TIG) dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, by improving the bead shape, and by creating the compressive residual stress. In this study, a new post-weld treatment method improving the weld bead shape and metal structure at the welding zone using Friction Stir Processing (FSP), a welding process, is proposed to enhance fatigue life. For that, a pin-shaped tool and processing condition employing Friction Stir Processing (FSP) is established through experiments. Experimental results revealed that fatigue life is improved by around 50% compared to as-welded fatigue specimens by reducing the stress concentration at the weld toe and by generating a metal structure finer than that of flux-cored arc welding (FCAW).

• Journal of Welding and Joining
• /
• 제5권1호
• /
• pp.42-56
• /
• 1987

Fatigue Fracture behaviors of the TIG-welded aluminum alloys, such as Al 2024-T4, A1 5050-0 and Al 7075-T7 were investigated when a crack propagated from tensile residual stress region and compressive residual stress region. The experimental values were compared with the values expected by the Forman equation. The experimental results are summarized as the following: (1) In case of fatigue crack propagation from residual stress region, the values predicted by Forman equation were Found to exactly corresponded to the experimental values. (2) When the stress intensityfactors affected by compressive residual stress, Kres, were greater than the stress intensity factors by minimum applied stresses. Kmin, the Forman equation was found to be improper to be applied directly, but the equation appeared to be proper, if the stress ratio was modified to zero. (3) The experimental results confirmed that residual stress was relaxed by repeated tensile loading and the relaxing trend was greater in case of compressive residual stress than that of tensile residual stress.

• Journal of Welding and Joining
• /
• 제5권4호
• /
• pp.12-21
• /
• 1987

To investigate the suitability of nitrogen gas as an internal purging gas, various properties of GTA welded joints of duplex, 316L stainless steel, Cu-Ni alloy pipe using nitrogen purging gas were evaluated with reference to onew purged with argon gas. Mechanical properties evaluated by the tensile, bending test, and hardness value of welded joints with nitrogen gas purging did not show any difference those with argon gas. General and local corrosion rates of each welded joint prepared by nitrogen gas purging also showed no difference with those prepared by argon gas. Based on the present test results it is confirmed that nitrogen is a suitable purging gas for GTA welding of stainless steels and nonferrous piping systems, which can be used at lower cost instead of argon.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 1998년도 특별강연 및 춘계학술발표 개요집
• /
• pp.150-154
• /
• 1998

The purpose of this paper is to investigate optimum welding conditions of STS 304 thin sheet by GTA welding and control 6 $\delta$--fenite which is harmful in mechanical processing, corrosion problem and can be formed brittle a phase in using long term at high temperature. One series of automatic welds was made using argon plus 10, 20, 30 % nitrogen to ensure a fully austenite deposit. Results obtained were summarized as follows: 1) 6 $\sigma$ferrite content in the weld metals is influenced largely by the nitrogen content. 2) Additions of nitrogen to the shielding gas can significantly reduce the amount of retained delta ferrite and result in an increase in hot cracking. 3) Bead width was increased when Ar + $N_2$ shielding gas was used and travel speed was increased. 4) Ar+$N_2$ shielding gas made weld metal ductile and reduce 6 -$\delta$-ferrite.