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 필릿용접구조물의 좌굴변형에 관한 연구

추환수,조상명,Chu, Hwan-Su,Cho, Sang-Myung 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.3

The structures distorted by welding have to be corrected. Since the correcting work needs a lot of costs and time, it is very important to minimize the buckling distortion due to welding of thin plate structure. Therefore the aim of this study is to investigate the effect of single bead on plate welding and fillet welding on the buckling distortion. In the single bead on plate welding, it was found that the welding speed and welding sequence were the most dominant factors on distortion. In the fillet welding, there were four typical buckling modes observed, and the welding sequence was the most influential factor on the buckling distortion. However typical distortion measuring method is not considered for the distortion correcting process costs of each buckling modes, therefore, in this study, the measuring method is developed to classify the buckling modes for torsion of specimen and buckling distortion depend on nodal point for the bead on plate welding specimen and fillet welds.

Trail Rolling Method for Control of Buckling Distortion in AA5083 GMA Butt Weldment

DONG-JU LEE,SANG-BEOM SHIN 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.6

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

용접 각 변형량 해석해를 이용한 용접 공정변수 최적화에 관한 연구

이세환 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.7

Welding distortion is a current issue in many industrial parts, especially for heavy industry such as shipbuilding, plant industry. The welding process has many processing parameters influencing welding angular distortion such as heat input power, welding speed, gas flow rate, plate thickness and the welded material properties, etc. In this work, the conventional local minimization concept was applied to find a set of optimum welding process parameters, consisted of welding speed, plate thickness and heat input, for a minimum angular distortion. An analytic solution for welding angular distortion, which is based on laminated plate theory, was also applied to investigate and optimize the welding process parameters. The optimized process parameters and the angular distortion for various parametric conditions could be easily found by using the local minimum concept.

용접 변형을 고려한 변형 조립체의 공차해석 모델링

최우영(Wooyoung Choi),정현(Hyun Chung) (사)한국CDE학회 2013 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2013 No.1

Welding is the primary joining process in manufacturing marine structures. As a way to improve the dimensional quality of products in shipyard during the production process, the welding distortion and their estimation have been studied rigorously. The welding distortion accounts for major geometrical variations in the intermediate products in shipbuilding processes and greatly affects the downstream assembly processes. The residual stresses, caused by the non-nominally shaped intermediate products, affect the magnitude of welding distortions as well. In previous research, an initial variation and welding distortion of the nominal parts are described as a linear superposition by the modified method of influence coefficient. However this research neglects the effects of the welding variations and residual stress to the final assembly spring-back deviation shape and only considers the mean deviation of welding distortion. This paper suggests a compliant assembly theory which includes the welding deformation using method of influence coefficient. The proposed model is based on the sources of variation and sensitivity matrix, which effectively represent the patterns of welding distortion of non-nominal plate parts. This suggested model is validated using the experimental data of thin plate welding.

튜브 용접부의 용접변형 및 잔류응력에 관한 연구

진형국,신상범,이동주,박동환,Jin, Hyung-Kook,Shin, Sang-Beom,Lee, Dong-Ju,Park, Dong-Hwan 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.5

The purpose of this study is to evaluate the distortion and the residual stress of GTA tubular welds between tube and head. In order to do it, the heat input model for GTA welding process was first developed by experiment and FE analyses. The welding distortion and the residual stress distribution of the tubular welds according to welding pass and various restraint degrees were evaluated by using FEA with the heat input model. From FEA results, it was found that the residual stress and the radial distortion at the weld toe of tube part decrease with a decrease in the number of welding pass. However, the maximum residual stresses in each direction of tubular welds are almost constant regardless of the external restraint degree. It was mainly due to the high internal restraint of the welds.

Review on Mitigation of Welding-Induced Distortion Based on FEM Analysis

Chunbiao Wu,Jae-Woong Kim 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.1

Welding distortion is an unavoidable issue due to localized expansion and contraction during the heating and cooling cycles, and has a negative effect on the fabrication process. However, mitigating weld distortion to meet product requirements is a challenging task, because welding shrinkage can’t be prevented, only controlled. This paper provides a comprehensive literature review of various techniques to reduce and optimize the deformation induced by welding in the design stage and manufacturing process. Finite element numerical analysis methods are usually employed to predict welding distortion, and can cost less than actual experiments. The review of these approaches is useful to fully understand the main mechanisms used to mitigate weldinginduced distortion, and for choosing the most suitable method to minimize deformation based on realistic fabrication requirements.

용접각변형에 미치는 용접길이의 영향

박정웅,이해우,Park Jeong-Ung,Lee Hae-Woo 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.4

To estimate welding deformation for large steel structures, either experiment result with small specimen or analysis result of FEM with small numerical model is used. Consequently, it is important to decide the welding length of specimen and numerical model not to have an effect on welding deformation for accurate estimation of whole welding deformation. This study experimentally clarifies the effect of welding length on angular distortion due to welding by varying welding length of specimens, but fixing width and thickness of specimens on V-groove butt welding, fillet welding and bead on plate welding. As a resell the critical welding length on fillet welding and on bead on plate welding is over 500mm and on V-groove butt welding is over 1,000mm.

Investigations on welding residual stress and distortion in a cylinder assembly by means of a 3D finite element method and experiments

Hui-Jun Yi,Jong-Yun Kim,Jin-Ho Yoon,Sung-Soo Kang 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.12

In the present work, both experimental and numerical simulation methods are used to investigate the characteristics of welding distortion and residual stress distribution. A 3D thermo-mechanical Finite Element Analysis (FEA) method is used to predict the welding distortion and residual stress of cylinder-shaped multi-pass layer weldments. Each weld pass is performed using a quarter-circle balanced welding procedure. To investigate the influence of deposition sequence and welding heat input on the welding distortion and residual stress, a continuous welding procedure is also calculated. The corresponding FEA models considered a moving heat source, the deposition sequence, and temperature-dependent thermal and mechanical properties. The results predicted by 3D FEA model are generally in good agreement with the measurements. Finally, the numerical and experimental results suggest that both deposition sequence and heat input affect welding distortion and residual stress distribution. Furthermore, the 3D thermal-mechanical FEA method can predict cylinder-type welding distortion.

Application of welding simulation to block joints in shipbuilding and assessment of welding-induced residual stresses and distortions

Fricke, Wolfgang,Zacke, Sonja The Society of Naval Architects of Korea 2014 International Journal of Naval Architecture and Oc Vol.6 No.2

During ship design, welding-induced distortions are roughly estimated as a function of the size of the component as well as the welding process and residual stresses are assumed to be locally in the range of the yield stress. Existing welding simulation methods are very complex and time-consuming and therefore not applicable to large structures like ships. Simplified methods for the estimation of welding effects were and still are subject of several research projects, but mostly concerning smaller structures. The main goal of this paper is the application of a multi-layer welding simulation to the block joint of a ship structure. When welding block joints, high constraints occur due to the ship structure which are assumed to result in accordingly high residual stresses. Constraints measured during construction were realized in a test plant for small-scale welding specimens in order to investigate their and other effects on the residual stresses. Associated welding simulations were successfully performed with fine-mesh finite element models. Further analyses showed that a courser mesh was also able to reproduce the welding-induced reaction forces and hence the residual stresses after some calibration. Based on the coarse modeling it was possible to perform the welding simulation at a block joint in order to investigate the influence of the resulting residual stresses on the behavior of the real structure, showing quite interesting stress distributions. Finally it is discussed whether smaller and idealized models of definite areas of the block joint can be used to achieve the same results offering possibilities to consider residual stresses in the design process.