• Title, Summary, Keyword: Residual Analysis

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Proposal of residual stress mitigation in nuclear safety-related austenitic stainless steel TP304 pipe bended by local induction heating process via elastic-plastic finite element analysis

  • Kim, Jong-Sung;Kim, Kyoung-Soo;Oh, Young-Jin;Oh, Chang-Young
    • Nuclear Engineering and Technology
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    • v.51 no.5
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    • pp.1451-1469
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    • 2019
  • This paper proposes a residual stress mitigation of a nuclear safety-related austenitic stainless steel TP304 pipe bended by local induction heating process via performing elastic-plastic finite element analysis. Residual stress distributions of the pipe bend were calculated by performing finite element analysis. Validity of the finite element analysis procedure was verified via comparing with temperature histories measured by using thermocouples, ultrasonic thickness measurement results, and residual stress measurement results by a hole-drilling method. Parametric finite element stress analysis was performed to investigate effects of the process and geometric shape variables on the residual stresses on inner surfaces of the pipe by applying the verified procedure. As a result of the parametric analysis, it was found that it is difficult to considerably reduce the inner surface residual stresses by changing the existing process and geometric shape variables. So, in order to mitigate the residual stresses, effect of an additional process such as cooling after the bending on the residual stresses was investigated. Finally, it was identified that the additional heating after the bending can significantly reduce the residual stresses while other variables have insignificant effect.

Statistical Analysis of Chlorine Residual in Korean Drinking Water (국내정수장의 잔류염소농도에 대한 조사연구)

  • Sohn, Jinsik;Kang, Hyosoon
    • Journal of Korean Society of Water and Wastewater
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    • v.20 no.2
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    • pp.281-287
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    • 2006
  • Maintaining adequate chlorine residual is crucial in water treatment facilities, Treatment technique, newly promulgated regulation, requires sufficient disinfection in order to control more resistant microorganisms such as Viruses and Giardia lamblia. Each water treatment plant should report various water qualities including chlorine residual and disinfection by-products, thus plenty of data has been generated. Even though statistical analysis using these data are forced to investigate the status and effect of water qualities in water facilities very few researches have been performed in korea. This study performed statistical analysis of chlorine residual during three years in Korean drinking water. The average chlorine residual concentrations were 0.701mg/L, 0.738mg/L, 0.763mg/L in 2002, 2003, 2004, respectively. Monthly variations of chlorine residual was not significant. ANOVA result showed that yearly variance of chlorine residual is different in only less than $5000m^3/day$ of water treatment capacity. The statistical analysis can help government to establish new regulation with scientific basis.

Numerical Analysis and Experimental Verification of Relaxation and Redistribution of Welding Residual Stresses (용접잔류응력의 이완과 재분포 해석 및 실험적 검증)

  • Song, Ha-Cheol;Jo, Young-Chun;Jang, Chang-Doo
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.6
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    • pp.84-90
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    • 2004
  • For the precise assessment of the effect of welding residual stresses on structural strength and fatigue crack growth behavior, new FE analysis algorithms for the estimation of residual stress relaxation due to external load and redistribution due to fatigue crack propagation were proposed in this paper. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis In the analysis of fatigue crack propagation, the applied SIF(Stress Intensity Factor) range was evaluated by $\frac{1}{4}$-point displacement extrapolation method, and the effect of welding residual stresses on crack propagation was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.

Assessment of Fatigue Crack Propagation Considering the Redistribution of Residual Stress due to Overload

  • Jang, Chang-Doo;Leem, Hyo-Kwan;Choi, Yeoung-Dal;Bang, Jun-Kee;So, Ha-Young
    • Journal of Ship and Ocean Technology
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    • v.11 no.2
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    • pp.26-33
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    • 2007
  • For the assessment of the retardation of fatigue crack propagation behavior due to overload, new FE analysis algorithms considering compressive residual stress redistribution near crack tip was proposed in this paper. The size of plastic zone near crack tip was obtained by elasto-plastic analysis and it was compared with Irwin's equation. The amount of residual stress redistribution was assessed by subsequent elasto-plastic analysis, and the difference of residual stress distributions between constant amplitude load and overload was obtained. In the analysis of fatigue crack propagation, the applied SIF range was evaluated by ASTM E647, and the effect of residual stresses on crack propagation was considered using the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.

Development of Residual Stress Analysis Procedure for Fitness-For-Service Assessment of Welded Structure (용접 구조물의 사용중 적합성 평가를 위한 잔류응력 해석절차 개발)

  • Kim, Jong-Sung;Jin, Tae-Eun;P. Dong;M. Prager
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.5
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    • pp.713-723
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    • 2003
  • In this study, a state of art review of existing residual stress analysis techniques and representative solutions is presented in order to develope the residual stress analysis procedure for fitness-for-service (FFS) assessment of welded structure. Critical issues associated with existing residual stress solutions and their treatments in performing FFS are discussed. It should be recognized that detailed residual stress evolution is an extremely complicated phenomenon that typically involves material-specific ther-momechanical/metallurgical response, welding process physics, and structural interactions within a component being welded. As a result, computational procedures can vary significantly from highly complicated numerical techniques intended only to elucidate a small part of the process physics to cost-effective procedures that are deemed adequate for capturing some of the important features in a final residual stress distribution. Residual stress analysis procedure for FFS purposes belongs to the latter category. With this in mind, both residual stress analysis techniques and their adequacy for FFS are assessed based on both literature data and analyses performed in this investigation.

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.

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.

Analysis of residual stress redistribution of weldment due to cutting (절단에 따른 용접부 잔류응력 재분포 해석)

  • Yang, Seung-Yong;Goo, Byeong-Choon;Choi, Sung-Kyu
    • Proceedings of the KSME Conference
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    • pp.1074-1079
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    • 2003
  • In this paper, we conducted finite element analysis to investigate the residual stress redistributions of weldment due to cutting. To evaluate the effect of the residual stress on the fatigue behavior of weldment, test specimens are commonly cut from the weldment, but the distributions of the residual stress in the cut specimen should be different from those in the original weldment. Our work is to evaluate the difference between the residual stresses before and after weldment-cutting to understand the effect of cutting on the residual stress. Transient heat analysis, elastic-plastic mechanical analysis and element removal technique are used to simulate the welding and cutting procedures on the commercial finite element code ABAQUS.

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Evaluation of the Residual Stress of Thin Film Based on the Nanoindentation and Finite Element Analysis. (유한요소해석과 나노인덴테이션을 활용한 박막의 잔류응력 평가)

  • 황병원;김영석;박준원
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.355-358
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    • 2003
  • To estimate the residual stresses in the thin film and surface coatings, combined method based on nanoindentation and finite element (FE) analysis was developed. A simple equation for estimating the residual stress was composed of the hardness and the parameters which can be driven from the nanoindentation loading and unloading behaviors. FE analysis on the nanoindentation procedure under the various residual stress levels was performed to determine the parameters that included in the equation. The equation showed a good coincidence between the estimated residual stresses and those for the FE analysis. Thus the proposed method was considered as a useful method for estimating the residual stresses in the thin film without stress free specimen.

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An Evaluation of Residual Stress Redistribution in the Welding Residual Stress Field Caused by Fatigue Crack Propagation by Finite Element Method (용접잔류응력장에서 피로균열의 전파에 따른 잔류응력 재분포에 대한 해석적 평가)

  • Park, Eung-Joon;Kim, Eung-Joon
    • Journal of Welding and Joining
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    • v.26 no.6
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    • pp.92-96
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    • 2008
  • An investigation was performed to predict residual stress redistribution for the crack propagation initially through tensile residual stress field. The analytical method, which is based on Dugdale model by finite element analysis using elastic analysis method considering the superposition principle, was proposed to estimate the redistribution of residual stress caused by crack propagation. The various aspect of distribution of residual stress caused by crack propagation was examined based on the configuration change of specimen. The analysis results show that the aspect of redistribution of residual stress caused by crack propagation depends on the width of the specimen provided that the initial distribution of residual stress is identical.