• Title/Summary/Keyword: plastic equivalent strain

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Sensitivity Analysis of Strain on Notches under Cyclic Loading to 2-D Finite Element Density in Elasto-Plastic Finite Element Analysis (탄소성 유한요소해석시 2차원 유한요소 밀도에 대한 반복하중이 작용하는 노치부의 변형률의 민감도 분석)

  • Jong-Sung Kim;Hyun-Su Jang
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.17 no.1
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    • pp.1-7
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    • 2021
  • This paper presents sensitivity analysis results of strain on notches under cycling loading to 2-D finite element density considering plasticity. Cylindrical notched specimens having some stress concentrations were modeled with 2-D axisymmetrical finite element having various finite element densities. Elasto-plastic finite element analysis was performed for the various finite element models subjected to cycling loading considering plasticity. The finite element analysis results were compared to investigate sensitivity of the finite element analysis variables such as von-Mises effective stress, accumulated equivalent plastic strain, and equivalent plastic strain to 2-D finite element density. As a result of the comparison, it was found that the accumulated equivalent plastic strain is more sensitive than the others whereas the von-Mises effective stress is much less sensitive.

Finite Element Simulation of Fracture Toughness Test (파괴인성시험의 유한요소 시뮬레이션)

  • Chu, Seok Jae;Liu, Conghao
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.4
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    • pp.491-496
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    • 2013
  • Finite element simulations of tensile tests were performed to determine the equivalent stress - equivalent plastic strain curves, critical equivalent stresses, and critical equivalent plastic strains. Then, the curves were used as inputs to finite element simulations of fracture toughness tests to determine the plane strain fracture toughness. The critical COD was taken as the COD when the equivalent plastic strain at the crack tip reached a critical value, and it was used as a crack growth criterion. The relationship between the critical COD and the critical equivalent plastic strain or the reduction of area was found. The relationship between the plane strain fracture toughness and the product of the critical equivalent stress and the critical equivalent plastic strain was also found.

Effect of Geometrical Discontinuity on Ductile Fracture Initiation Behavior under Static Leading

  • An, G.B.;Ohata, M.;Toyoda, M.
    • International Journal of Korean Welding Society
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    • v.3 no.1
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    • pp.51-56
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    • 2003
  • It is important to evaluate the fracture initiation behaviors of steel structure. It has been well known that the ductile cracking of steel would be accelerated by triaxial stress state. Recently, the characteristics of critical crack initiation of steels are quantitatively estimated using the two-parameters, that is, equivalent plastic strain and stress triaxiality, criterion. This study is paid to the fundamental clarification of the effect of notch radius, which can elevate plastic constraint due to heterogeneous plastic straining on critical condition to initiate ductile crack using two-parameters. Hense, the crack initiation testing were conducted under static loading using round bar specimens with circumferential notch. To evaluate the stress/strain state in the specimens was used thermal elastic-plastic FE-analysis. The result showed that equivalent plastic strain to initiate ductile crack expressed as a function of stress triaxiality obtained from the homogeneous specimens with circumferential notched under static loading. And it was evaluated that by using this two-parameters criterion, the critical crack initiation of homogeneous specimens under static loading.

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EFFECT OF STRENGTH MISMATCH AND DYNAMIC LOADING ON THE DUCTILE CRACK INITIATION FROM NOTCH ROOT

  • An, Gyn-Baek;Yoshida, Satoshi;Ohata, Mitsuru;Toyoda, Masao
    • Proceedings of the KWS Conference
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    • 2002.10a
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    • pp.145-150
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    • 2002
  • It has been well known that ductile fracture of steels is accelerated by triaxial stresses. The characteristics of ductile crack initiation in steels are evaluated quantitatively using two-parameters criterion based on equivalent plastic strain and stress triaxiality. It has been demonstrated by authors using round-bar specimens with circumferential notch in single tension that the critical strain to initiate ductile crack from specimen center depends considerably on stress triaxiality, but surface cracking of notch root is in accordance with constant strain condition. In order to evaluate the stress/strain state in the specimens, especially under dynamic loading, a thermal, elastic-plastic, dynamic finite element (FE) analysis considering the temperature rise due to plastic deformation has been carried out. This study provides the fundamental clarification of the effect of strength mismatching, which can elevate plastic constraint due to heterogeneous plastic straining, loading mode and loading rate on critical condition to initiate ductile crack from notch root using equivalent plastic strain and stress triaxiality based on the two-parameter criterion obtained on homogeneous specimens under static tension. The critical condition to initiate ductile crack from notch root for strength mismatched bend specimens under both static and dynamic loading would be almost the same as that for homogeneous tensile specimens with circumferential sharp notch under static loading.

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Impact Analysis According to Material of Hand Phone (휴대폰 재질에 따른 충격 해석)

  • Cho, Jae-Ung;Min, Byoung-Sang;Han, Moon-Sik
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.8 no.2
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    • pp.69-75
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    • 2009
  • This study is analyzed by impact simulation according to material property at terminal case of hand phone. Maximum equivalent stress or strain at plastic is 40 times as great as that at magnesium alloy. And the next greatest stress or strain is shown at aluminium alloy. The value of maximum equivalent stress is shown as 6.5 Mpa in case of plastic, magnesium alloy and aluminium alloy. Maximum shear strain at plastic is 40 times as great as that at magnesium alloy. And the next greatest strain is shown at aluminium alloy. The value of deformation or strain at magnesium alloy and aluminium alloy is not different.

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Welding Deformation Analysis of Plates Using the Inherent Strain-based Equivalent Load Method (고유변형률 기반 등가하중법을 이용한 판의 용접변형 해석)

  • Lee, Joo-Sung
    • Journal of Welding and Joining
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    • v.28 no.2
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    • pp.39-46
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    • 2010
  • IIn this study, used is the equivalent loading method based on the inherent strain to predict the welding deformation of panel members. Equivalent loads are computed from the inherent strain distribution around weld line, and then applied for the linear finite element analysis. Thermal deformation of panel members can be, of course, carried out through the rigorous thermal elasto-plastic analysis procedure but it is not practical in applying to predicting the welding deformation of large structures such as blocks found in a ship structure from view of computing time. The present equivalent load approach has been applied to flat plate model to verify the present approach, and to several curved plate models having the curvature in the welding direction to investigate the effect of the longitudinal curvature upon the weld-induced deformation. The results are compared with those by thermal elasto-plastic analysis. As far as the present results are concerned, it can be said that the present approach shows good agreement with the results by welding experiment and the rigorous thermal elasto-plastic analysis. The present approach has been also applied to predict the welding deformation of panel block as for application illustration to practical model.

Friction Stir Welding Analysis Based on Equivalent Strain Method using Neural Networks

  • Kang, Sung-Wook;Jang, Beom-Seon
    • Journal of Ocean Engineering and Technology
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    • v.28 no.5
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    • pp.452-465
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    • 2014
  • The application of friction stir welding (FSW) technology has been extended to all industries, including shipbuilding. A heat transfer analysis evaluates the weldability of a welded work piece, and elasto-plastic analysis predicts the residual stress and deformation after welding. A thermal elasto-plastic analysis based on the heat transfer analysis results is most frequently used today. However, its application to large objects such as offshore structures and hulls is impractical owing to its long computational time. This paper proposes a new method, namely an equivalent strain method using the inherent strain, to overcome the disadvantages of the extended analysis time. In the present study, a residual stress analysis of FSW was performed using this equivalent strain method. Additionally, in order to reflect the external constraints in FSW, the reaction force was predicted using a neural network, Finally, the approach was verified by comparing the experimental results and thermal elasto-plastic analysis results for the calculated residual stress distribution.

Precise dynamic finite element elastic-plastic seismic analysis considering welds for nuclear power plants

  • Kim, Jong-Sung;Jang, Hyun-Su
    • Nuclear Engineering and Technology
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    • v.54 no.7
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    • pp.2550-2563
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    • 2022
  • This study performed a precise dynamic finite element time history elastic-plastic seismic analysis considering the welds, which have been not considered in design stage, on the nuclear components subjected to severe seismic loadings such as beyond-design basis earthquakes for sustainable nuclear power plants. First, the dynamic finite element elastic-plastic seismic analysis was performed for a general design practice that does not take into account the welds of the pressurizer surge line system, one of safety class I components in nuclear power plants, and then the reference values for the accumulated equivalent plastic strain, equivalent plastic strain, and von Mises effective stress were set. Second, the dynamic finite element elastic-plastic seismic analyses were performed for the case of considering only the mechanical strength over-mismatch of the welds as well as for the case of considering both the strength over-mismatch and welding residual strain. Third, the effects of the strength over-mismatch and welding residual strain were analyzed by comparing the finite element analysis results with the reference values. As a result of the comparison, it was found that not considering the strength over-mismatch may lead to conservative assessment results, whereas not considering the welding residual strain may be non-conservative.

A Study on the Cutting characteristics of a plastic sheet including Friction (마찰을 고려한 플라스틱 시트의 절단특성에 관한 연구)

  • Han Joohyun;Kim Dohyun;Kim Chungkyun
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2004.11a
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    • pp.245-248
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    • 2004
  • The press cutter is productive equipment that practically manufactures materials such as fabrics, papers, films, leathers, rubbers etc. into the desired shapes using cutting method. Plate cutting process is one of the primary energy absorbing mechanisms in a grounding or collision event. The cutting mechanism is complicated and involves plastic flow of plate in the vicinity of the tip, friction between wedge and plate, deformation of plate. In this paper, we studied the effect of friction between cutter and plastic sheet for producing precise and superior products. The press cutter is analyzed numerically using MARC finite element program according to the variation of friction coefficients. The FEM results showed that normal stress, equivalent cauchy stress, normal total strain, equivalent total strain are good when friction coefficient is 0.0 and shear stress, shear total strain are good when friction coefficient is 0.8.

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Deformation behaviours of SS304 tubes in pulsating hydroforming processes

  • Yang, Lianfa;Wang, Ninghua;He, Yulin
    • Structural Engineering and Mechanics
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    • v.60 no.1
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    • pp.91-110
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    • 2016
  • Tube hydroforming (THF) under pulsating hydraulic pressures is a novel technique that applies pulsating hydraulic pressures that are periodically increased to deform tubular materials. The deformation behaviours of tubes in pulsating THF may differ compared to those in conventional non-pulsating THF due to the pulsating hydraulic pressures. The equivalent stress-strain relationship of metal materials is an ideal way to describe the deformation behaviours of the materials in plastic deformation. In this paper, the equivalent stress-strain relationships of SS304 tubes in pulsating hydroforming are determined based on experiments and simulation of free hydraulic bulging (FHB), and compared with those of SS304 tubes in non-pulsating THF and uniaxial tensile tests (UTT). The effect of the pulsation parameters, including amplitude and frequency, on the equivalent stress-strain relationships is investigated to reveal the plastic deformation behaviours of tubes in pulsating hydroforming. The results show that the deformation behaviours of tubes in pulsating hydroforming can be well described by the equivalent stress-stain relationship obtained by the proposed method. The amplitude and frequency of pulsating hydraulic pressure have distinct effects on the equivalent stress-strain relationships-the equivalent stress becomes augmented and the formability is enhanced with the increase of the pulsation amplitude and frequency.