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유한요소해석을 이용한 다층 FCA 맞대기 용접부의 횡 방향 잔류응력 평가에 관한 연구
신상범,이동주,박동환,Shin, Sang-Beom,Lee, Dong-Ju,Park, Dong-Hwan 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.4
The purpose of this study is to evaluate the residual stresses at the multi-pass FCA weldment using the finite element analysis (FEA). In order to do it, an H-type specimen was selected as a test specimen. The variable used was in-plane restraint intensity. The temperature distribution at the multi-pass FCA butt weldment was evaluated in accordance with the relevant guidance recommended by the KWJS. The effective conductivity for the weld metal corresponding to each welding pass was introduced to control the maximum temperature below the vaporization temperature of weld metal. The heat flux caused by welding arc was assumed to be applied to the weld metal corresponding to welding pass. With heat transfer analysis results, the distribution of transverse residual stresses was evaluated using the thermo-mechanical analysis and compared with the measured results by XRD and uniaxial strain gage. In thermo-mechanical analysis, the plastic strain resetting at the temperature above melting temperature of $1450^{\circ}C$ was considered and the weld metal and base metal was assumed to be bilinear kinematics hardening continuum. According to the comparison between FEA and experiment, transverse residual stresses at the multi-pass FCA butt weldment obtained by FEA had a good agreement with the measured results, regardless of in-plane rigidity. Based on the results, it was concluded that thermo-mechanical FE analysis based on temperature distribution calculated in accordance with the KWJS’s guidance could be used as a tool to predict the distribution of residual stress of the multi-pass FCA butt weldment.
다층 양면 개선 맞대기 용접부의 각 변형 예측에 관한 연구
신상범,윤중근,Shin, Sang-Beom,Youn, Joong-Geun 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.1
The purpose of this study is to establish the predictive method of angular distortion of the double-sided multi-pass butt weldment achieve it, the behavior of angular distortion in the butt weldment were investigated using comprehensive finite element analyses and experiments. The angular distortion in the multi-pass butt weldment strongly depends on the welding heat input(Q) and the effective bending rigidity of the weld throat. The effective bending rigidity of the first welding pass on the backing side was defined as the function of dimensionless parameter(k) and a bending rigidity of bead-on-plate weldment. Based on the results, the predictive equation for angular distortion of multi-pass butt weldment was proposed and verified by experiments.
박판 패널 용접부의 용접 기법에 따른 좌굴 변형에 관한 연구
신상범,이동주,이주성,Shin, Sang-Beom,Lee, Dong-Ju,Lee, Joo-Sung 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.3
The purpose of this study is to propose the proper fillet welding process for preventing the buckling distortion in thin panel welded structure. In order to do it, a heat input model for laser hybrid welding process was developed using FEA and experiment. The principal factors controlling the angular distortion and longitudinal shrinkage force caused by FCA and laser hybrid welding were identified as the welding heat input and weld rigidity using FEA. The predictive equations of angular distortion and longitudinal shrinkage force for each welding process were formulated as a function of the principal factors proposed. With the predictive equations, the buckling distortion at the thin panel welded structure with welding process was evaluated and compared using nonlinear buckling analysis and STEM(simplified thermo elastic method). Based on the results, the best way to prevent the buckling distortion at the given welded panel structures was identified as an intermittent FCA welding.
대형 컨테이너선의 해치 코밍 FCA 맞대기 용접부의 횡 방향 잔류응력 예측에 관한 연구
신상범,이동주,이주성,Shin, Sang-Beom,Lee, Dong-Ju,Lee, Joo-Sung 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.4
The purpose of this study is to establish a predictive equation of transverse residual stress at the thick FCA butt weldment of large container vessel. The variables used were restraint degree, yield strength of base material, thickness of weldment and welding heat input. Restraint degree at the thick weldment of container ship having the various welding sequence was calculated using FEA. From the result, the H-type specimen was designed to reproduce the level of restraint degree at the actual weldment of containership. Based on the results, the predictive equations of the mean value and the distribution of transverse residual stress at each location of the weldment were established using dimensional analysis and multiple-regression method. The predictive equations were verified by comparing with those measured by XRD in the actual weldment of the ship.
Crude Oil Tanker 선저부 보강재 필렛 용접부 각장 설계에 관한 연구
강봉국,신상범,박동환,Kang, Bong-Gook,Shin, Sang-Beom,Park, Dong-Hwan 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.1
The purpose of this study is to determine the proper fillet weld size for the stiffeners on hull bottom plate of crude oil tanker. To achieve it, the effective notch stress and hot spot stress of the fillet weld with leg length specified in the rule were evaluated by using comprehensive FE analyses. Based on the results, the fatigue damages at each location of weld were calculated. Meanwhile the transitional behavior of initial welding distortion in the hull bottom plate under the design conditions was investigated by using a non-linear FEA. Welding distortion and residual stress introduced during fabrication process were considered as initial imperfections. According to FE analysis results, if the fillet leg length satisfies the design criteria of the classification society, the concern on the root failure at the fillet welds in the bottom hull plate during the design life can be negligible. In addition, considering the transitional behavior of the distortion during the service life, the fillet leg length should be minimized.
상 변태를 고려한 HY-100강 용접부의 수축 및 잔류응력 예측에 관한 연구
이희태,신상범,Lee, Hee-Tae,Shin, Sang-Beom 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.1
For high performance and structural stability, application of high strength steel has continuously increased. However, the change of the base metal gives rise to problems with the accuracy management of the welded structure. It is attributed to the martensite phase transformation of the high strength low alloy steel weldment. The purpose of this study is to establish the predictive equation of transverse shrinkage and residual stress for the HY-100 weldment. In order to do it, high speed quenching dilatometer tests were performed to define a coefficient of thermal expansion(CTE) at the heating and cooling stage of HY-100 with various cooling rates. Uncoupled thermal-mechanical finite element(FE) models with CTE were proposed to evaluate the effect of the martensite phase transformation on transverse shrinkage and residual stresses at the weldment. FEA results were verified by comparing with experimental results. Based on the results of extensive FEA and experiments, the predictive equation of transverse shrinkage and longitudinal shrinkage force at the HY-100 weldment were formulated as the function of welding heat input/in-plane rigidity and welding heat input respectively.
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.