보수용접부 폭에 따른 용접잔류응력의 변화 및 재분배 거동 평가

박치용(Chi-Yong Park),이휘승(Hwee-Sueng Lee),허남수(Nam-Su Huh) 대한기계학회 2014 大韓機械學會論文集A Vol.38 No.2

본 논문에서는 보수용접부 폭 변화에 따른 이종금속 맞대기 용접부(Dissimilar metal butt weld) 용접잔류응력의 분포 및 동종금속용접/기계적 하중에 의한 재분배 거동을 평가하였다. 이를 위해 5가지 다른 보수용접부 폭을 고려한 상세 2차원 유한요소 열해석 및 응력해석을 수행하였다. 유한요소해석 결과를 바탕으로 보수용접에 의한 용접잔류응력 분포를 평가하였으며, 동종금속용접 및 기계적 하중에 의한 응력 재분배 특성을 평가하였다. 보수용접에 의해 배관 내면에서는 큰 인장 용접잔류응력이 축방향과 원주방향에 대해 발생하는 것으로 나타났으며 보수용접부 폭이 특정값 이상이 되면 용접잔류응력 분포가 변하는 것으로 나타났다. 그러나 동종금속용접과 기계적 하중을 고려하면 인장잔류응력값이 크게 감소하였으며 그 경향은 보수용접부 폭에 무관한 것으로 나타났다. In this study, we investigated the variations in welding residual stresses in dissimilar metal butt weld due to width of repair welding and re-distribution behaviors resulting from similar metal welding (SMW) and mechanical loading. To this end, detailed two-dimensional axi-symmetric finite element (FE) analyses were performed considering five different repair welding widths. Based on the FE results, we first evaluated the welding residual stress distributions in repair welding. We then investigated the re-distribution behaviors of the residual stresses due to SMW and mechanical loads. It is revealed that large tensile welding residual stresses take place in the inner surface and that its distribution is affected, provided repair welding width is larger than certain value. The welding residual stresses resulting from repair welding are remarkably reduced due to SMW and mechanical loading, regardless of the width of the repair welding.

평강판 용접시 용접조건에 따른 각변형에 대한 연구

백영창(Young-Chang Baek) 산업기술교육훈련학회 2011 산업기술연구논문지 (JITR) Vol.16 No.2

It is important for us to gain further Knowledge concerning on the several deformation with welding condition of weld structures. Weld shrinkage is due to complex action with many factors, may theoritical or semi-empirical equations about weld shrinkage have been applied with limitatlon because of the problem of precision as well as much difficulties In practical field application. The deformation of the several shrinkage for the butt joint CO2 gas arc welding of plates is investigated in this paper. The facts revealed in this study are as follows. Weld heat input is propertional to the butt Joint welding. The angular distortion in butt joint welding of the t6 plate is about 0.86°, and the t9 plate is about 1.05°. The angular distortion at a near by welding line(with 20-30mm welding line) has been a curve of few shrinkage, and more than with in 30mm welding 1ine were to change by straight. With the restraint angular distortion was reduced from 5% to 15% that of free Joint.

Submerged Arc Welding에서 용접조건에 따른 인장성 연구

백영창(Young-Chang Baek) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.4

Weldments according to the welding conditions on changes in tensile strength is important to acquire more knowledge. Structural discontinuities such as joints and in part due to repeated loading and fatigue crack growth are more likely to crash, accident welding conditions depending on the skill of welders according to the strength of welds is true that a lot of factors that reduce a lot of research on this progress and form, but the geometry and load conditions due to the combined effects, including a lot of issues still remain to be solved in this study, the following facts. Weld butt weld material in the form 25V/340A 3.2t 4.5t is good and the tensile strength and tensile resistance, both in terms of bead formation 30V/320A condition was most excellent. Welding lap welding material in the form of 3.2t and 4.5t 31V/310A considered the most suitable 32V/320A the tensile strength and the bead width and the optimum conditions were determined to be appropriate. In lap welding gap 0, 0.5, 1mm in crease in tensile strength lowered significantly shape the gap so that there is no way to weld in a pressurized state optimum welding conditions can be viewed as substrate according to the thickness of the two kinds of Welded tensile strength in the thickness of the smaller side is the best way to weld.

ATOS 80 고장력강의 용접 패스에 따른 용접부 방사선검사에 관한 연구

백정환(Jung-Hwan Baek),최병기(Byung-Ky Choi) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.6

In constructing all kinds of equipment and steel structure, parts with discontinuities such as weld defects formed in the welded structure can generate fatigue cracks that results in damage or accidents. In this study, weld zones are investigated with X-rays and the latent images are put on film. Weld zone defects can be verified by developing the film. As weld defects are investigated by radiographic testing and correlated with the welding condition, more appropriate welding conditions can be found. According to the result of X-ray radiographic inspection of butt welding ATOS 80 high-strength steel with a thickness of 12 ㎜, the best conditions for welding without creating weld defects are 4 weld-passes, a protective gas of 20% CO₂ and 80% Ar, a protective gas flow of 20L/min, a welding current of 200A, an arc voltage of 24V, a welding speed of 14.4 ㎝/min, a welding rod angle of 50°, a welding gap of 5 ㎜ with a ceramic base, and sand pre-heating to 160° Celsius prior to welding.

용접변형의 고정도 예측을 위한 지배인자의 정당성 검증

이재익,장경호,김유철,Lee, Jae-Yik,Chang, Kyong-Ho,Kim, You-Chul 대한용접접합학회 2013 대한용접·접합학회지 Vol.31 No.5

The legitimacy of dominating factor in the high accuracy prediction of welding distortion was investigated for butt welding and fillet welding. When out-of-plane distortion was measured by the experiment objecting to butt welding, if tack welding was easily performed, the position of a neutral axis was variously changed by the irregularity. Then, there have been a case that out-of-plane distortion was generated in the unexpected direction. This case should be especially noted. New model for the experiment was proposed so as to solve this problem. As it was elucidated by the case of fillet welding, it was verified that the analysis should be carried out with satisfying the yield condition (especially at high temperature above 700 degree Celsius) and with closely simulating the penetration shape (heat input in weld metal) in order to solve the proposition that is the high accuracy prediction of welding distortion. It was confirmed that residual stress is highly predicted because welding distortion is highly predicted, too.

박판 Al MIG 용접용 AC펄스 전류 파형의 설계 및 출력특성

조상명,김태진,이창주,임성룡,공현상,김기정 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.2

Since new types of vehicles or structures made from thin aluminum alloy are under rapid development and some products are already on the market, welding of aluminium sheet is increasing. MIG(Metal Inert Gas), MIG-Pulse, TIG(Tungsten Inert Gas) welding are the typical Ai welding. MIG welding has the advantage of high speed, but it is difficult to apply to the thin plate, because of bum-through by the high heat input and spatter. MIG-Pulse welding can weld without spatter and burn-through, but when the gap exists at the welding joint, there is quite a possibility of bum-through. TIG welding is difficult to weld at a high speed. AC Pulse welding alternates between DCEP(Direct Current Electrode Positive) and DCEN(Direct Current Electrode Negative). DCEN is higher wire melting rate than DCEP, while lower temperature of droplet than DCEP. In AC Pulse welding, far fixed welding current, wire melting rate increases as the EN ratio increases. For fixed wire feed rate, welding current decreases as the EN ratio increases. Because of these features, the temperature of droplet, the depth of penetration, the width of bead decrease and the reinforcement height increases as EN ratio increases, and these are able to weld at a high speed, lower heat input. It is the purpose of this study that design of AC pulse current waveform for MIG welding of Al sheet and estimation of output characteristic.

Nondestructive Testing of Residual Stress on the Welded Part of Butt-welded A36 Plates Using Electronic Speckle Pattern Interferometry

Kyeongsuk Kim,정현철 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.1

Most manufacturing processes, including welding, create residual stresses. Residualstresses can reduce material strength and cause fractures. For estimating the reliabilityand aging of a welded structure, residual stresses should be evaluated as precisely aspossible. Optical techniques such as holographic interferometry, electronic speckle patterninterferometry (ESPI), Moire interferometry, and shearography are noncontact means ofmeasuring residual stresses. Among optical techniques, ESPI is typically used as anondestructive measurement technique of in-plane displacement, such as stress andstrain, and out-of-plane displacement, such as vibration and bending. In this study, ESPIwas used to measure the residual stress on the welded part of butt-welded American Societyfor Testing and Materials (ASTM) A36 specimens with CO2 welding. Four types ofspecimens, base metal specimen (BSP), tensile specimen including welded part (TSP),compression specimen including welded part (CSP), and annealed tensile specimenincluding welded part (ATSP), were tested. BSP was used to obtain the elastic modulus of abase metal. TSP and CSP were used to compare residual stresses under tensile andcompressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase mapimages obtained by ESPI. The results confirmed that residual stresses of welded parts canbe measured by ESPI.

플래시버트 용접과 연속열간압연법으로 제조된 철근의 기계적 성질과 미세조직에 미치는 합금원소의 영향

김기원,조승재,강정윤,Kim, Ki-Won,Cho, Seung-Jae,Kang, Chung-Yum 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3

Flash butt welding is applied in many industries. New technology was developed recently for joining billets which called "EBROS (Endless Bar Rolling System)". After reheating billets in furnace, two billets were joined using flash butt welding. The objective of this study was to investigate the effect of alloying elements on mechanical properties of flash butt welded zone of hot rolled steel bar. The tensile properties on welded zone of Fe-Mn steel and Fe-Mn-V steel were dropped as compared with non-welded zone. Fe-Mn-Nb steel was opposed to the former. It was found that the white band at the welded zone had high ferrite volume fraction and large ferrite grain size. The vertical white band between flash butt welded billets was transformed into an arrowhead it of steel bar. According to this band, softening has been appeared. There was a interesting phenomenon with HAZ of Fe-Mn-Nb Steel, 40nm scale of particles were observed and hardness of HAZ was higher than non-welded zone.

Nondestructive Testing of Residual Stress on the Welded Part of Butt-welded A36 Plates Using Electronic Speckle Pattern Interferometry

Kim, Kyeongsuk,Jung, Hyunchul Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.1

Most manufacturing processes, including welding, create residual stresses. Residual stresses can reduce material strength and cause fractures. For estimating the reliability and aging of a welded structure, residual stresses should be evaluated as precisely as possible. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry (ESPI), Moire interferometry, and shearography are noncontact means of measuring residual stresses. Among optical techniques, ESPI is typically used as a nondestructive measurement technique of in-plane displacement, such as stress and strain, and out-of-plane displacement, such as vibration and bending. In this study, ESPI was used to measure the residual stress on the welded part of butt-welded American Society for Testing and Materials (ASTM) A36 specimens with $CO_2$ welding. Four types of specimens, base metal specimen (BSP), tensile specimen including welded part (TSP), compression specimen including welded part (CSP), and annealed tensile specimen including welded part (ATSP), were tested. BSP was used to obtain the elastic modulus of a base metal. TSP and CSP were used to compare residual stresses under tensile and compressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase map images obtained by ESPI. The results confirmed that residual stresses of welded parts can be measured by ESPI.

스틸 프레스 어퍼암 용접 구조에 따른 암 성능 영향도 비교

오상훈(Sanghoon Oh),박민수(Minsoo Park) 한국자동차공학회 2022 한국자동차공학회 부문종합 학술대회 Vol.2022 No.6

In the case of rear wheel suspension arms, the method of forming a high-strength steel panel and applying overlap welding is the most used. But looking at the recent trend of competitors, there are increasing cases of applying butt welding to the joint. In general, butt welding is known to be disadvantageous in terms of productivity compared to overlap welding. In order to understand the reason for applying butt welding, the rear wheel upper arm of the existing overlap welding structure was converted to a butt welding structure. After the design change, comparison was made in terms of the main performance of the arm and the assembly of the module. As a result of the study, when butt welding was applied to the steel press upper arm, it was confirmed that the axial stiffness, stress, and buckling force performance were superior under the same weight condition compared to the overlap welding structure. And it was found that there is also an advantage that the left and right suspension arms can be commonized.