• Title/Summary/Keyword: ductile fracture simulation

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Simulation of the Forming Process of the Shielded Slot Plate for the Molten Carbonate Fuel Cell Using a Ductile Fracture Criterion (연성파괴조건을 사용한 용융탄산염 연료전지용 쉴디드 슬롯 플레이트의 성형 공정 유한요소 해석)

  • Lee, C.W.;Yang, D.Y.;Lee, S.R.;Kang, D.W.;Chang, I.G.;Lee, T.W.
    • Transactions of Materials Processing
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    • v.21 no.5
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    • pp.298-304
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    • 2012
  • The shielded slot plates for a molten carbonate fuel cell(MCFC) have a sheared corrugated trapezoidal pattern. In the FEM simulations for the production of the shielded slot plate, the user material subroutine VUMAT in the commercial FEM software ABAQUS was used to implement a ductile fracture criterion. The critical damage value for the ductile fracture criterion was determined by comparing the experimental results of the shearing process with the simulation results. Using the ductile fracture criterion, the FEM simulation of the three-dimensional forming process of the shielded slot plate was conducted. The effects of the shearing process on the forming process were examined through FEM simulation and experiments. The forming simulation of nine unit cells was conducted. Using the simulation results of the forming process, the deformed shape after springback was calculated. The experimental result shows good agreement with the simulation.

Ductile Fracture Behaviour under Mode I Loading Using Rousellier Ductile Damage Theory

  • Oh, Dong-Joon;Howard, I.C.;Yates, J.R.
    • Journal of Mechanical Science and Technology
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    • v.14 no.9
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    • pp.978-984
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    • 2000
  • The aim of this study is to investigate the ductile fracture behaviour under Mode I loading using SA533B pressure vessel steel. Experiments consist of the Round Notch Bar Test (RNB), Single Edge Crack Bending Test (SECB), and V-Notch Bar Test (VNB). Results from the RNB test were used to tune the damage modelling constant. The other tests were performed to acquire the J-resistance curves and to confirm the damage constants. Microstructural observation includes the measurement of crack profile to obtain the roughness parameter. Finally, simulation using Rousellier Ductile Damage Theory (RDDT) was carried out with 4-node quadrilateral element ($L_c=0.25\;mm$). For the crack advance, the failed element removal technique was adopted with a ${\beta}$ criterion. In conclusion, the predicted simulation using RDDT showed a good agreement with the experimental results. A trial using a roughness parameter was made for a new evaluation of J-resistance curve, which is more conservative than the conventional one.

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Ductile fracture simulation using phase field approach under higher order regime

  • Nitin Khandelwal;Ramachandra A. Murthy
    • Structural Engineering and Mechanics
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    • v.89 no.2
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    • pp.199-211
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    • 2024
  • The loading capacity of engineering structures/components reduces after the initiation and propagation of crack eventually leads to the final failure. Hence, it becomes essential to deal with the crack and its effects at the design and simulation stages itself, by detecting the prone area of the fracture. The phase-field (PF) method has been accepted widely in simulating fracture problems in complex geometries. However, most of the PF methods are formulated with second order continuity theoryinvolving C0 continuity. In the present study, PF method based on fourth-order (i.e., higher order) theory, maintaining C1 continuity has been proposed for ductile fracture simulation. The formulation includes fourth-order derivative terms of phase field variable, varying between 0 and 1. Applications of fourth-order PF theory to ductile fracture simulation resulted in novelty in this area. The proposed formulation is numerically solved using a two-dimensional finite element (FE) framework in 3-layered manner system. The solutions thus obtained from the proposed fourth order theory for different benchmark problems portray the improvement in the accuracy of the numerical results and are well matched with experimental results available in the literature. These results are also compared with second-order PF theory and a comparison study demonstrated the robustness of the proposed model in capturing ductile behaviour close to experimental observations.

Bursting Failure Prediction in Tube Hydroforming Process (튜브 액압성형 공정에서의 터짐 현상 예측)

  • Kim, Jeong;Lei, Liping;Kang, Sung-Jong;Kang, Beom-Soo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.6
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    • pp.160-169
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    • 2001
  • To predict busting failure in tubular hydroforming, the criteria for ductile fracture proposed by Oyane is combined with the finite element method. From the histories of stress and strain in each element obtained from finite element analysis, the fracture initiation site is predicted by mean of the criterion. The prediction by the ductile fracture criterion is applied to three hydroforming processes such as a tee extrusion, an automobile rear axle housing and lower am. For these products, the ductile fracture integral I is not only affected by the process parameters, but also by preforming processes. All the simulation results show the combination of the finite element analysis and the ductile fracture criteria is useful in the prediction of farming limit in hydroforming processes.

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Finite Element Based Multi-Scale Ductile Failure Simulation of Full-Scale Pipes with a Circumferential Crack in a Low Carbon Steel (유한요소기반 다중스케일 연성파손모사 기법을 이용한 원주방향 균열이 존재하는 탄소강 실배관의 파손예측 및 검증)

  • Han, Jae-Jun;Bae, Kyung-Dong;Kim, Yun-Jae;Kim, Jong-Hyun;Kim, Nak-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.7
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    • pp.727-734
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    • 2014
  • This paper describes multi-scale based ductile fracture simulation using finite element (FE) damage analysis. The maximum and crack initiation loads of cracked components were predicted using proposed virtual testing method. To apply the local approach criteria for ductile fracture, stress-modified fracture strain model was adopted as the damage criteria with modified calibration technique that only requires tensile and fracture toughness test data. Element-size-dependent critical damage model is also introduced to apply the proposed ductile fracture simulation to large-scale components. The results of the simulation were compared with those of the tests on SA333 Gr. 6 full-scale pipes at $288^{\circ}C$, performed by the Battelle Memorial Institute.

Design of Hexagonal Fitting Nut Preform Considering Ductile Fracture (연성파괴를 고려한 6각 피팅너트 예비성형체 설계)

  • Park T. J.;Kim D. J.;Kim B. M.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2001.05a
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    • pp.197-200
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    • 2001
  • In the multi-stage former, manufacture of hexagonal fitting nut was generated in a defective products about $70{\~}80\%$. Defective products reduced in a product stiffness and increased a product cost. Defects for manufacturing hexagonal fitting nut caused in a increase of ductile fracture value. So in the study, a preform designed to reduce ductile fracture value and designed preform verified through the finite element simulation. In conclusion, Ductile fracture value reduced if A round dimension of preform reduced and a part of opposition angle contributed in Plenty a volume.

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Finite Element Simulation of Sheet Metal Shearing by the Element Kill Method (요소제거기법에 의한 판재 전단가공의 유한요소 시뮬레이션)

  • Ko, Dae-Cheol;Kim, Chul;Kim, Byung-Min;Choi, Jae-Chan
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.11
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    • pp.114-123
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    • 1996
  • The major objective of the present paper is to estabilish analytical technique in order to closely understand and analyze the actual shearing process. First of all, isothermal and non-isothermal FE-simulation of the shearing process are carried out using finite element software DEFORM. Based on preliminary simulation using DEFORM, the finite element program to analyze two dimensional shearing process is developed. The ductile fracture criterion and the element kill method are also used to estimate if and where a fracture will occur and to investigate the features of the sheared surface in shearing process. It can be seen that the developed program combined with the ductile fracture criterion and element kill method has enabled the achievement of FE-simulation from initial stage to final stage of shearing process. The effects of punch-die clearance on shearing process are also investigated. In order to verify the effectiveness of the proposed technique the simulation results are compared with the known expermental data. It is found that the results of the present work are in close agreement with the published experimental results.

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Ductile cracking simulation procedure for welded joints under monotonic tension

  • Jia, Liang-Jiu;Ikai, Toyoki;Kang, Lan;Ge, Hanbin;Kato, Tomoya
    • Structural Engineering and Mechanics
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    • v.60 no.1
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    • pp.51-69
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    • 2016
  • A large number of welded steel moment-resisting framed (SMRF) structures failed due to brittle fracture induced by ductile fracture at beam-to-column connections during 1994 Northridge earthquake and 1995 Kobe (Hyogoken-Nanbu) earthquake. Extensive research efforts have been devoted to clarifying the mechanism of the observed failures and corresponding countermeasures to ensure more ductile design of welded SMRF structures, while limited research on the failure analysis of the ductile cracking was conducted due to lack of computational capacity and proper theoretical models. As the first step to solve this complicated problem, this paper aims to establish a straightforward procedure to simulate ductile cracking of welded joints under monotonic tension. There are two difficulties in achieving the aim of this study, including measurement of true stress-true strain data and ductile fracture parameters of different subzones in a welded joint, such as weld deposit, heat affected zone and the boundary between the two. Butt joints are employed in this study for their simple configuration. Both experimental and numerical studies on two types of butt joints are conducted. The validity of the proposed procedure is proved by comparison between the experimental and numerical results.

Development of an Aluminum Liner using Multi-drawing and Ironing Processes based on the Ductile Fracture Criterion (연성파괴에 기반한 다단 디프드로잉 및 아이어닝 공정에 의한 알루미늄 라이너 개발)

  • Yun, Y.W.;Kang, S.H.;Yun, C.K.;Lee, J.H.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.10a
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    • pp.403-407
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    • 2009
  • In this work, finite element investigations were carried out to manufacture a seamless aluminum liner without crack generation using four-stage deep drawing followed by two-stage ironing process. In order to predict the crack generation during the liner manufacturing process, the Normalize Cockroft-Latham(NCL) which is one of ductile fracture criteria was adopted. In addition, the tensile tests were carried out to obtain the critical value of NCL by comparing the experimental and FE simulation results. From this, various case studies based on FE simulation were carried to obtain the optimum die designs which can prevent the crack generation during ironing processes. Finally, the aluminum liner was successfully made using obtained die designs so that requirements were met in terms of thickness and height of the liner.

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ON THE TREATMENT OF DUCTILE FRACTURE BY THE LOCAL APPROACH CONCEPT IN CONTINUUM DAMAGE MECHANICS : THEORY AND EXAMPLE

  • Kim, Seoung-Jo;Kim, Jin-Hee;Kim, Wie-Dae
    • Journal of Theoretical and Applied Mechanics
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    • v.2 no.1
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    • pp.31-50
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    • 1996
  • In this paper, a finite element analysis based on the local approach concept to fracture in the continuum damage mechanics is performed to analyze ductile fracture in two dimensional quasi-static state. First an isotropic damage model based on the generalized concept of effective stress is proposed for structural materials in the context of large deformation. In this model, the stiffness degradation is taken as a measure of damage and so, the fracture phenomenon can be explained as the critical deterioration of stiffness at a material point. The modified Riks' continuation technique is used to solve incremental iterative equations. Crack propagation is achieved by removing critically damaged elements. The mesh size sensitivity analysis and the simulation of the well known shearing mode failure in plane strain state are carried out to verify the present formulation. As numerical examples, an edge cracked plate and the specimen with a circular hole under plane stress are taken. Load-displacement curves and successively fractured shapes are shown. From the results, it can be concluded that the proposed model based on the local approach concept in the continuum damage mechanics may be stated as a reasonable tool to explain ductile fracture initiation and crack propagation.