• Title/Summary/Keyword: Welding Residual Stress

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A Study on the Analysis for Welding Residual Stress of Preflex Beam (PREFLEX BEAM 제작시의 용접부 역학적 특성에 관한 연구)

  • 방한서;주성민;안해영
    • Journal of Ocean Engineering and Technology
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    • v.17 no.6
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    • pp.65-71
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    • 2003
  • Since the preflex beam is fabricated through welding, the pre-compressive stresses that should occur over the concrete pier are diminished by the welding residual stresses. Therefore welding residual stresses must be relieved during the fabrication. Therefore, the analysis and examination of the accurate welding residual stress distribution characteristics are necessary. In this study, accurate distribution of welding residual stress of the preflex beam is analyzed by the finite element method, using 2 dimensional and 3 dimensional elements. Further, the thermo-mechanical behavior of the preflex beam is also studied. After the finite element analysis, real distribution of welding residual stress is measured using the sectioning method, and then is compared with the simulation results. The distribution of welding residual stress by finite analysis agreed well with the experimental results.

A Quantitative Estimation of Welding Residual Stress Relaxation for Fatigue Strength Analysis (피로강도해석을 위한 용접잔류응력 이완의 정량적 평가)

  • Han, Seung-Ho;Lee, Tak-Kee;Shin, Byung-Chun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.2018-2025
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    • 2002
  • It is well known that the strength and the fatigue life of welded steel components are affected extensively by welding residual stresses distributed around their weldments under not only monotonic but also cyclic loads. The externally applied loads are to be superimposed with the welding residual stresses, so that unexpected deformations and failures of the components might occur. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under monotonic loads the relaxation takes place when the sum of external and welding residual stress exceeds locally the yield stress of material used. By the way, it is shown that under cyclic loads the welding residual stress is considerably relieved by the first or the early cycles of loads, and then gradually relaxed with increasing loading cycles. Although many investigations in this field have been carried out, the phenomenon and mechanism of the stress relaxation are still not clear, and there are few comprehensive models to predict amount of relaxed welding residual stress. In this study, the characteristics of the welding residual stress relaxation under monotonic and cyclic loads were investigated, and a model to predict quantitatively amount of welding residual stress relaxation was proposed.

Fatigue Life Evaluation Based on Welding Residual Stress Relaxation and Notch Strain Approach for Cruciform Welded Joint (용접잔류응력 이완 및 노치변형률법을 적용한 십자형 필렛용접 이음부의 피로수명 평가)

  • Han, Jeong-Woo;Han, Seung-Ho;Shin, Byung-Chun;Kim, Jae-Hoon
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1103-1108
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    • 2003
  • The fatigue strength of welded joint is influenced by the welding residual stress which is relaxed depending on local stress distributed in vicinity of stress raisers, eg. under cut, overlap and blow hole. To evaluate its fatigue life the geometry of the stress raisers and the welding residual stress should be taken into account. The several methods based on notch strain approach have been proposed in order to consider the two factors above mentioned. These methods, however, have shown considerable differences between analytical and experimental results. It is due to the fact that the amount of the relaxed welding residual stress evaluated by the cyclic stress-strain relationship do not correspond with that occurred in reality. In this paper the residual stress relaxation model based on experimental results was used in order to reduce the discrepancy of the estimated amount of the relaxed welding residual stress. Under an assumption of the superimposition of the relaxed welding residual stress and the local stress, a modified notch strain approach was proposed and verified to the cruciform welded joint.

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A Study on the Welding Residual Stress Analysis of the Spot Welding Point (전기저항 점용접부의 용접잔류응력 해석에 관한 연구)

  • 손일선;배동호
    • Proceedings of the KWS Conference
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    • 1999.05a
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    • pp.233-236
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    • 1999
  • The welding residual stress should be considered in fatigue stress analysis because it develope during the process of the electric resistance spot welding and it causes bad affect on the fatigue crack initiation and growth at nugget edge of spot welded points. Therefore the accurate estimation of residual stress is crucial. In this study, nonlinear finite element analysis on welding residual stress generated during the process of the spot welding was conducted, and their results were compared with the experimental data measured by X-ray diffraction method. From the results, it was found that welding residual stress existed as tension in the nugget center and as compression around the nugget edge.

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Assessment of Round Robin Analyses Results on Welding Residual Stress Prediction in a Nuclear Power Plant Nozzle (원전 노즐 용접부 잔류응력 예측을 위한 Round Robin 해석 결과 분석)

  • Song, Tae-Kwang;Bae, Hong-Yeol;Kim, Yun-Jae;Lee, Kyoung-Soo;Park, Chi-Yong;Yang, Jun-Seog;Huh, Nam-Su;Kim, Jong-Wook;Park, June-Soo;Song, Min-Sup;Lee, Seung-Gun;Kim, Jong-Sung;Yu, Seung-Cheon;Chang, Yoon-Suk
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.1
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    • pp.72-81
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    • 2009
  • This paper provides simulational round robin test results for welding residual stress prediction of safety/relief nozzle. To quantify the welding variables and define the recommendation for prediction and determination of welding residual stress, 6 partners in 5 institutes participated in round robin test. It is concluded that compressive axial and hoop residual stress occurs in dissimilar metal weld and pre-existing residual stress distribution in dissimilar metal weld was affected by similar metal weld due to short length of safe end. Although the reason for the deviation among the results was not pursued further, the effect of several key elements of FE analyses on welding residual stress was investigated in this paper.

Prediction of Welding Residual Stress of Dissimilar Metal Weld of Nozzle using Finite Element Analyses (유한요소해석을 이용한 노즐 이종금속용접부의 용접잔류응력 예측)

  • Huh, Nam-Su;Kim, Jong-Wook;Choi, Suhn;Kim, Tae-Wan
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.83-84
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    • 2008
  • The primary water stress corrosion cracking (PWSCC) of dissimilar metal weld based on Alloy 82/182 is one of major issues in material degradation of nuclear components. It is well known that the crack initiation and growth due to PWSCC is influenced by material's susceptibility to PWSCC and distribution of welding residual stress. Therefore, modeling the welding residual stress is of interest in understanding crack formation and growth in dissimilar metal weld. Currently in Korea, a numerical round robin study is undertaken to provide guidance on the welding residual stress analysis of dissimilar metal weld. As a part of this effort, the present paper investigates distribution of welding resisual stress of a ferritic low alloy steel nozzle with dissimilar metal weld using Alloy 82/182. Two-dimensional thermo-mechanical finite element analyses are carried out to simulate multi-pass welding process on the basis of the detailed design and fabrication data. The present results are compared with those from other participants, and more works incorporating physical measurements are going to be performed to quantify the uncertainties relating to modelling assumptions.

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Fatigue Life Estimation of Welded Components Considering Welding Residual Stress Relaxation and Its Mean Stress Effect (잔류응력 이완 및 이의 평균응력 효과를 고려한 용접부 피로수명 평가)

  • Han, Seung-Ho;Han, Jeong-Woo;Shin, Byung-Chun;Kim, Jae-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.1
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    • pp.175-182
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    • 2003
  • The fatigue life of welded joints is sensitive to welding residual stress and complexity of their geometric shapes. To predict the fatigue life more reasonably. the effects of welding residual stress and its relaxation on their fatigue strengths should be considered quantitatively, which are often regarded to be equivalent to the effects of mean stresses by external loads. The hot-spot stress concept should be also adopted which can reduce the dependence of fatigue strengths for various welding details. Considering the factors mentioned above, a fatigue life prediction model using the modified Goodman's diagram was proposed. In this model, an equivalent stress was introduced which is composed of the mean stress based on the hot-spot stress concept and the relaxed welding residual stress. From the verification of the proposed model to real welding details, it is proved that this model can be applied to predict reasonably their fatigue lives.

Welding Residual Stress Measurement by Barkhausen Noise Method (Barkhausen noise를 이용한 용접 잔류응력 측정)

  • Lee, S.S.;Ahn, B.Y.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.10 no.1
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    • pp.91-95
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    • 1990
  • Welding residual stress was measured by Barkhausen noise method. The calibration experiment was done for the quantitative analysis. The specimen for the calibration experiment must has the same thermo-mechanical history as the actual material to be tested. The Barkhausen noise were analysed by the pulse-height distribution. The results show that the distribution and magnitude of welding residual stress from Barkhausen noise method are in good agreement with those from blind hole method.

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Welding Residual Stress Measurement by Ultrasonic Method (초음파를 이용한 용접잔류응력 측정기술)

  • Lee, S.S.;Ahn, B.Y.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.9 no.2
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    • pp.61-66
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    • 1989
  • Welding residual stress was measured by ultrasonic birefringence technique. Acoustoelastic constant was taken by averaging the values in the literature. The initial birefringence from prefered orientation of grains was measured. The EMAT transducers were used to remove couplant effect. The results show that the distribution and magnitude of welding residual stress from ultrasonic measurement are in good agreements with those from semi destructive hole drilling measurement.

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An Assessment on the Ultimate Strength of Welding Joint by the Effect of External Force (外力의 效果를 고려한 熔接部의 最終强度에 대한 評價)

  • Bang, Han-Seo;Cha, Yong-Hun;O, U-Seok
    • Journal of Ocean Engineering and Technology
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    • v.9 no.2
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    • pp.20-29
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    • 1995
  • When structures are constructed by welding, structural elements are always accompained by welding residual stress and deformation. Therefore, when the rigidity and strength of the welded structures is considered, it is very important to have sufficient information about the effect of initial deflection and welding residual stress on them. In this paper, the square plates with welding residual stress under compression are dealt with; First, heat conduction and thermal elastic-plastic problems are analyzed by finite element method using 4-node isoparametric elements for assessment on the ultimate strength of welding joint. Later, the ultimate strength of welding joint is assessed by examining the effect of changed type of loading. The specimens are 500{\times}$500mm(a/b=1) and 750{\times}$500mm(a/b=1.5) rectangular plates of whichthicknesses is 9.0mm and simply supported plates getting axiul load in each direction.

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