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The effect of initial stress induced during the steel manufacturing process on the welding residual stress in multi-pass butt welding

  • Park, Jeong-ung;An, Gyubaek;Woo, Wanchuck
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.2
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    • pp.129-140
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    • 2018
  • A residual stress generated in the steel structure is broadly categorized into initial residual stress during manufacturing steel material, welding residual stress caused by welding, and heat treatment residual stress by heat treatment. Initial residual stresses induced during the manufacturing process is combined with welding residual stress or heat treatment residual stress, and remained as a final residual stress. Because such final residual stress affects the safety and strength of the structure, it is of utmost importance to measure or predict the magnitude of residual stress, and to apply this point on the design of the structure. In this study, the initial residual stress of steel structures having thicknesses of 25 mm and 70 mm during manufacturing was measured in order to investigate initial residual stress (hereinafter, referred to as initial stress). In addition, thermal elastic plastic FEM analysis was performed with this initial condition, and the effect of initial stress on the welding residual stress was investigated. Further, the reliability of the FE analysis result, considering the initial stress and welding residual stress for the steel structures having two thicknesses, was validated by comparing it with the measured results. In the vicinity of the weld joint, the initial stress is released and finally controlled by the weld residual stress. On the other hand, the farther away from the weld joint, the greater the influence of the initial stress. The range in which the initial stress affects the weld residual stress was not changed by the initial stress. However, in the region where the initial stress occurs in the compressive stress, the magnitude of the weld residual compressive stress varies with the compression or tension of the initial stress. The effect of initial stress on the maximum compression residual stress was far larger when initial stress was considered in case of a thickness of 25 mm with a value of 180 MPa, while in case of thickness at 70 mm, it was 200 MPa. The increase in compressive residual stress is almost the same as the initial stress. However, if initial stress was tensile, there was no significant change in the maximum compression residual stress.

Redistribution of Welding Residual Stress and its Effects on Fatigue Crack Propagation (피로균열이 진전할 때 용접잔류응력의 재분포와 그 영향)

  • 이용복;조남익
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.155-162
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    • 1995
  • Redistribution of residual stress and its effects during fatigue crack propagates from tensile residual stress region in weldment are investigated. Tests are performed by using welded CCT specimens of structual rolling steel (SS400) and it makes fatigue crack propagate from tensile residual stress region. For this study tension-tension loading type is selected by external loading condition and magnetizing stress indicator is used correctly to measure redistribution of residual stress according to fatigue crack growth and number of loading cycles. From this result, it is proved that redistribution of residual stress is mainly consist of residual stress released by fatigue crack growth. When fatigue crack propagates from tensile residual stress region residual stress are redistributed and it makes fatigue crack growth rate largely increase. Fatigue crack growth rate is low in case of redistributed residual stress compare with initial distributed residual stress.

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The Effect of residual stress for fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Jo, Seong-Gyu;Yang, Yeong-Su
    • Proceedings of the Korean Society of Laser Processing Conference
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    • pp.3-8
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    • 2006
  • The integrity of laser welded structures is decided with fracture strength and fatigue strength. This study presents fracture behavior considering residual stress in the laser welding. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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The Effect of residual stress on fracture behavior in the laser weldment (레이저용접부의 파괴에 미치는 잔류응력의 영향)

  • Cho, Sung-Kyu;Yang, Young-Soo;Noh, Young-Jin
    • Laser Solutions
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    • v.11 no.2
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    • pp.1-7
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    • 2008
  • The integrity of laser welded structures is decided in fracture strength and fatigue strength. This study made an effort to understand the fracture behavior considering residual stress. Experiments are conducted and analyses are performed to explore the influence of residual stress on fracture behavior of bead-on laser welded compact specimen. Fracture experiments are performed using ASTM 1820. The performed analyses included thermo-elasto-plastic analyses for residual stress and subsequent J-integral calculation. A modified J integral is calculated in the presence of residual stresses. The J-integral is path-independent for combination of residual stress field and stress due to mechanical loading. The results indicates that the tensile residual stress near crack front bring the low fracture load while the compressive residual stress bring the high fracture load compared to no residual stress specimen. These results quantitatively understand the influence of residual stress on fracture behavior.

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Residual Stress Evolution during Leveling of Hot Rolled High Strength Coils and Camber Prediction by Residual Stress Distribution (냉간 성형용 열연 고강도 강판의 교정 중 잔류응력 변화와 절단 후 캠버 발생 예측)

  • Park, K.C.;Ryu, J.H.
    • Transactions of Materials Processing
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    • v.17 no.2
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    • pp.107-112
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    • 2008
  • In order to investigate the residual stress evolution during the leveling process of hot rolled high strength coils for cold forming, the in-plane residual stress of plate sampled at SPM, rough leveler and finish leveler were measured by cutting method. Residual stress was localized near the edge of plate. As the thickness of plate was increased, the size of residual stress region was expanded. The gradient of residual stress within the plate was reduced during the leveling process. But the residual stress itself was not removed completely within the ranges of tested conditions. The exact camber of cut plate was able to be predicted by the measurement of residual stress distribution after leveling of the plate.

A Study on the Residual Stress Distribution of Pure Titanium Welding Material (순수티타늄 용접재의 잔류응력분포에 관한 연구)

  • Choi Byung-ki;Chang Kyung-chun
    • Journal of the Korean Society of Safety
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    • v.19 no.4
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    • pp.8-13
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    • 2004
  • The purpose of this paper is to investigate the welding residual stress distribution according to the constraint or non-constraint welding condition with titanium commonly using power station, aircraft, and ship. The measuring method of the residual stress was applied stress release rating method with strain gages and a potable strain meter. The x direction residual stress generally showed the tensile residual stress in case of res03int welding. On the other hand, the x direction residual stress under non-restraint welding were changed tensile stress into compressive stress on 15mm away from welding bead center. Also, the y direction residual stress generally showed the tensile residual stress in case of non-restraint welding and the y direction residual stress under restraint welding were changed tensile stress into compressive stress about 60mm away from welding bead center.

An Analysis of the Redistribution of Residual Stress Due to Crack Propagation Initially Through Residual Tensile Stress Field by Finite Element Method (인장잔류응력장으로부터 피로균열이 전파하는 경우 잔류응력의 재분포거동에 대한 해석적 검토)

  • 김응준;박응준;유승현
    • Journal of Welding and Joining
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    • v.21 no.7
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    • pp.71-77
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    • 2003
  • In this study, an investigation based on the superposition principle to predict residual stress redistribution caused by crack propagation itself initially through residual tensile stress field was performed by finite element method. The tendency in residual stress redistribution caused by crack propagation recognized both from the analytical results and experimental result was the residual stress concentration consecutively occurred in the vicinity of crack tip even the situation that the crack propagated to the region initially residual compressive stress existed. The software for the analysis is ABAQUS, which is a general purpose finite element package. The analytical method that attempt to take the plastic deformation at the crack tip due to tensile residual stress into the consideration of residual stress redistribution caused by crack propagation was proposed. The plastic zone size at the tip of fatigue crack and redistributed residual stresses were calculated by finite element method on the bases of the concept of Dugdale model. Comparing these analytical results with experimental results, it is verified that the residual stress redistribution caused by crack propagation can be predicted by finite element method with the proposed analytical method.

Regression Diagnostic Using Residual Plots

  • Oh, Kwang-Sik
    • Communications for Statistical Applications and Methods
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    • v.8 no.2
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    • pp.311-317
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    • 2001
  • It is necessary to check the linearity of selected covariates in regression diagnostics. There are various graphical methods using residual plots such as partial residual plots, augmented partial residual plots and combining conditional expectation and residual plots. In this paper, we propose the modified pseudolikelihood ratio test statistics based on these residual plots to test linearity of selected covariate. These test statistics which measure the distance between the nonparametric and parametric models are derived as a ratio of quadratic forms. The approximate distribution of these statistics is calculated numerically by using three moments. The power comparison of these statistics is given.

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Rejecting Outliers by Maximum Modified Normed Residual

  • Kim, Soon Kwi
    • Journal of the Korean Society for Quality Management
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    • v.13 no.2
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    • pp.56-60
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    • 1985
  • One may be particularly interested in identifying which are the genuinely exceptional observations, in order to create a new insight into the phenomena under study. To detect outliers, many statistics have been proposed such as the maximum normed residual (MNR), a statistic equivalent to the maximum normed residual C. Daniel proposed, studentized residual, standardized residual, and so on. This paper gives a procedure for calculating critical values of the maximum modified normed residual and the distribution of the modified normed residual.

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The Effects of Geometrical Shape and Post Weld Treatment on Welding Residual Stress Distribution of Weldment in Multi-pass Welded Pipe (다층용접배관의 용접부 잔류음력분포에 대한 기하학적형상과 용접후처리의 영향)

  • 김철한;조선영;김복기;배동호
    • Journal of Welding and Joining
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    • v.19 no.1
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    • pp.49-57
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    • 2001
  • In this study, the residual stress fields of multi-pass welded were analyzed by FEA under various geometrical conditions. In order to estimate the effects of pipe geometries on residual stress distribution, welding processes of each model were performed under the same heat cycles. And then, the influence of cutting off the weld bead on the residual stress redistribution was also estimated. From the results, in the range of t/D=0.05, axial residual stresses on the outer surface of the welded pipe were linearly decreased with pipe diameter increase. On the other hand, hoop residual stresses were not influenced by them. And both axial and hoop residual stresses on the outer surface of the welded pipe were increased with pipe diameter increase. But, when t/D was smaller than 0.05, they were converged in the nearly same value. The maximum residual stresses were generated at around HAZ. It in therefore necessary to consider them in welding design, strength evaluation, and analysis of fracture characteristics.

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