• Title/Summary/Keyword: Residual stress

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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.

Effect of welding residual stress on operating stress of nuclear turbine low pressure rotor

  • Tan, Long;Zhao, Liangyin;Zhao, Pengcheng;Wang, Lulu;Pan, Jiajing;Zhao, Xiuxiu
    • Nuclear Engineering and Technology
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    • v.52 no.8
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    • pp.1862-1870
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    • 2020
  • The purpose of this study is to investigate the effect of welding residual stress on operating stress in designing a nuclear turbine welded rotor. A two-dimensional axisymmetric finite element model is employed to calculate the residual stress before and after post weld heat treatment (PWHT), and then the superposition of residual stress after PWHT and operating stress at normal speed and overspeed were discussed. The investigated results show that operating stress can be affected significantly by welding residual stress, and the distribution trend of superposition stress at the weld area is mainly determined by welding residual stress. The superposition of residual stress and operating stress is linear superposition, and the hoop stress distribution of superposition stress is similar with the distribution of residual stress. With the increasing overspeed, the distribution pattern of the hoop superimposed stress remains almost unchanged, while the stress level increases.

Determination of Knoop Indentation Stress Conversion Factors for Measuring Equibiaxial Residual Stress (인장 및 압축 등방 잔류응력 측정을 위한 누프 압입시험의 응력환산계수 결정)

  • Jeong, Min Jae;Kim, Young-Cheon
    • Corrosion Science and Technology
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    • v.20 no.6
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    • pp.484-490
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    • 2021
  • Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.

A Study of the Development of the Stress Optic Law of Photoelastic Experiment Considering Residual Stress

  • Suh, Jae-guk;Hawong, Jai-sug;Shin, Dong-chul
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1674-1681
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    • 2003
  • Photoelastic experiment has two significant problems. The first problem is manufacturing a model specimen for complicated shapes of structures. The second problem is residual stress contained in the photoelastic model material. In this paper, the stress optic law that can be effectively used on photoelastic model materials with residual stress is developed. By using the stress optic law as developed in this research, we can obtain good results in photoelastic experiments using model material in which residual stress is contained. It is assured that the stress optic law developed in this research is useful. Therefore, it is suggested that the stress optic law considering residual stress can be applied to the photoelastic experiment for the stress analysis of the composite materials or bi-materials in which the residual stress is easily contained.

Prediction Model for Relaxation of Welding Residual Stress under Fatigue Loads (피로하중하 용접잔류응력 이완 추정모델)

  • 한승호;신병천
    • Journal of Welding and Joining
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    • v.20 no.3
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    • pp.84-90
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    • 2002
  • The strength and the life of welded components are affected extensively by the residual stresses distributed around their weldments not only under static loads, but also fatigue loads. The residual stress can be superimposed with externally applied loads, so that unexpected deformations and failures of members will be occurred. These residual stresses are not kept constant, but relaxed or redistributed during in service. Under static loads the relaxation takes place when the external stress superimposed with the residual stress exceeds locally the yield stress of material used. It is shown that under fatigue loads the residual stress is considerably relieved by the first or flew cycle loading, and then gradually relaxed with increasing loading cycles. In this study the phenomenon and mechanism of the stress relaxation by mechanical means were investigated and a model to predict quantitatively the residual stress relaxation for the case of static and fatigue loading condition was proposed.

A Study on Estimation of Residual Stress in Carburized Spur Gears and Its Effect on the Stress Intensity Factor (침탄치차의 잔류응력추정 및 잔류응력을 고려한 응력확대계수에 관한 연구)

  • 류성기
    • Journal of the Korean Society of Safety
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    • v.12 no.3
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    • pp.30-37
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    • 1997
  • This paper deals with the residual stress of carburized spur gears is calculated being on the assumption that the main cause of residual stress is the volume difference between case and core due to the martensitic transformation in cooling. A formula is proposed to estimated the residual stress from the hardness and the amount of retained austenite. The estimated residual stress is close to the stress measured by X-ray method. The estimated residual stress is applied to the analysis of the fracture mechanics of carburized spur gear teeth. The stress intensity factor due to the residual stress is demonstrated. The stress intensity factor is computed by the influence function method, and it is shown that the factor is decreased by the residual stress in Carburized gear tooth.

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Fatigue Strength Evaluation of IB-Type Spot Welded Lap Joint considered Residual Stress (잔류응력을 고려한 IB형 spot 용접이음재의 피로강도 평가)

  • 손일선
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1997.10a
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    • pp.127-131
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    • 1997
  • In systematic and orderly estimation of fatigue strength of the spot welded lap joints, because the influence of residual stress of fatigue crach initiation and growth is not negligible, there need to estimate fatigue strength considered residual stress at near spot weld part of the lap joints. Therefore, in this thesis, peformed stress distribution and residual stress analysis at near the spot weld part by F.E.M and X-ray diffraction method, and obtained the maximum principal stress considered residual stress at nugget edge by superposing residual stress at nugget edge by superposing their results. From the results obtained above, we could find that fatigue strength of the IB-type spot welded lap joints was rearranged by the maximum principal stress considered residual stress at nugget edge and was entirely low about 13 percents compare with that neglected residual stress.

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Prediction of Surface Residual Stress of Multi-pass Drawn Steel Wire Using Numerical Analysis (수치해석을 이용한 탄소강 다단 신선 와이어 표면 잔류응력 예측)

  • Lee, S.B.;Lee, I.K.;Jeong, M.S.;Kim, B.M.;Lee, S.K.
    • Transactions of Materials Processing
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    • v.26 no.3
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    • pp.162-167
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    • 2017
  • The tensile surface residual stress in the multi-pass drawn wire deteriorates the mechanical properties of the wire. Therefore, the evaluation of the residual stress is very important. Especially, the axial residual stress on the wire surface is the highest. Therefore, the objective of this study was to propose an axial surface residual stress prediction model of the multi-pass drawn steel wire. In order to achieve this objective, an elastoplastic finite element (FE) analysis was carried out to investigate the effect of semi-die angle and reduction ratio of the axial surface residual stress. By using the results of the FE analysis, a surface residual stress prediction model was proposed. In order to verify the effectiveness of the prediction model, the predicted residual stress was compared to that of a wire drawing experiment.

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.

Residual Stress Evolution during Leveling of Hot Rolled Cold Forming Purpose High Strength Coils and Camber Prediction (냉간 성형용 열연 고강도 강판의 교정 중 잔류음력 변화와 절단 후 camber 발생 거동 연구)

  • Park, K.C.;Ryu, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.10a
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    • pp.112-115
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    • 2007
  • 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 region with residual stress was expanded. The gradient of residual stress within plate was reduced during the leveling process. But the residual stress itself was not removed at the ranges of tested conditions. From the measured residual stress distribution within the plate, camber of plate cut to small width was predicted exactly within error range of experiment.

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