• Title/Summary/Keyword: Ductile Fracture Simulation

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Analysis of Tool Wear in Sheet Metal Shearing (판재 전단 가공에서 금형의 마멸 해석)

  • 고대철;김태형;김병민
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.805-810
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    • 1997
  • In this paper the technique to predict tool were theoretically in the sheet metal shearing process is suggested. The were in sheet metal tool affects the tolerances of final parts, metal flows and costs of processes. In order to predict the tool were the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. 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. Results obtained form finite element simulation such as node velocities and node forces are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the were rates on these points are accumulated during a process. It is assumed that the wear depth on the tool surface are linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is were is also discussed during the process.

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Application of cohesive zone model to large scale circumferential through-wall and 360° surface cracked pipes under static and dynamic loadings

  • Moon, Ji-Hee;Jang, Youn-Young;Huh, Nam-Su;Shim, Do-Jun;Park, Kyoungsoo
    • Nuclear Engineering and Technology
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    • v.53 no.3
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    • pp.974-987
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    • 2021
  • This paper presents ductile fracture simulation of full-scale cracked pipe for nuclear piping materials using the cohesive zone model (CZM). The main objective of this study is to investigate the applicability of CZM to predict ductile fracture of cracked pipes with various crack shapes and under quasi-static/dynamic loadings. The transferability of the traction-separation (T-S) curve from a small-scale specimen to a full-scale pipe is demonstrated by simulating small- and full-scale tests. T-S curves are calibrated by comparing experimental data of compact tension specimens with finite element analysis results. The calibrated T-S curves are utilized to predict the fracture behavior of cracked pipes. Three types of full-scale pipe tests are considered: pipe with circumferential through-wall crack under quasistatic/dynamic loadings, and with 360° internal surface crack under quasi-static loading. Computational results using the calibrated T-S curves show a good agreement with experimental data, demonstrating the transferability of the T-S curves from small-scale specimen.

Collision Simulation of a Floating Offshore Wind Turbine Considering Ductile Fracture and Hydrodynamics Using Hydrodynamic Plug-in HydroQus

  • Dong Ho Yoon;Joonmo Choung
    • Journal of Ocean Engineering and Technology
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    • v.37 no.3
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    • pp.111-121
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    • 2023
  • This paper intends to introduce the applicability of HydroQus to a problem of a tanker collision against a semi-submersible type floating offshore wind turbine (FOWT). HydroQus is a plug-in based on potential flow theory that generates interactive hydroforces in a commercial Finite element analysis (FEA) code Abaqus/Explicit. Frequency response analyses were conducted for a 10MW capacity FOWT to obtain hydrostatic and hydrodynamic constants. The tanker was modeled with rigid elements, while elastic-plastic elements were used for the FOWT. Mooring chains were modeled to implement station keeping ability of the FOWT. Two types of fracture models were considered: constant failure strain model and combined failure strain model HC-LN model composed of Hosford-Coulomb (HC) model & localized necking (LN) model. The damage extents were evaluated by hydroforces and failure strain models. The largest equivalent plastic strain observed in the cases where both restoring force and radiation force were considered. Stress triaxiality and damage indicator analysis showed that the application of HC-LN model was suitable. It could be stated that applications of suitable failure strain model and hydrodynamics into the collision simulations were of importance.

INFLUENCE OF INCLUSION ON INTERNAL DEFECT IN MULTI-STAGE EXTRUSION

  • Yoshida Y.;Fukaya Y.;Yukawa N.;Ishikawa T.;Ito K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2003.10b
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    • pp.51-54
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    • 2003
  • Internal defects such as chevron crack occasionally occur in the process of cold extrusion or cold drawing. It is known that the existence and property of inclusion greatly influences the generation of the internal crack. However, in the plastic working field, research about the effect of the inclusion on the fracture is not theoretically analyzed. This paper describes effects of the physical property of inclusion on the internal fracture generation in the process. Prediction of fracture was evaluated by critical damage value calculated by the equation of Cockcroft & Latham and its change by the inclusion physical property such as size and stiffness was investigated.

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Prediction of Tool Wear in Shearing Process by the Finite Element Method (유한요소법에 의한 전단가공 금형의 마멸예측)

  • Ko, Dae-Cheol;Kim, Byung-Min
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.1 s.94
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    • pp.174-181
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    • 1999
  • In this paper the technique to predict tool wear theoretically in shearing process is suggested. The tool wear in the process affects the tolerances of final pans, metal flows and costs of processes. In order to predict the tool wear the deformation of workpiece during the process is analyzed by using non-isothermal finite element program. 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. Results obtained from finite element simulation, such as nodal velocities and nodal forces, are transformed into sliding velocity and normal pressure on tool monitoring points respectively. The monitoring points are automatically generated and the wear rates on these points are accumulated during the process. It is assumed that the wear depth on the tool surface is linear function of the lot sizes based upon the known experimental results. The influence of clearance between die and punch upon tool wear is also discussed.

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Ingot-Breakdown Design of Tower Flange Material for Offshore Wind Turbine (해상풍력발전용 타워플랜지 소재의 잉고트 파쇄공정설계)

  • Yoo, G.Y.;Kang, N.H.;Kim, J.H.;Hong, J.K.;Lee, C.S.;Lee, J.M.;Kim, N.Y.;Yeom, J.T.
    • Transactions of Materials Processing
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    • v.21 no.7
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    • pp.412-419
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    • 2012
  • The ingot-breakdown scheme of a tower flange material (low-alloy steel) for offshore wind turbine was investigated using finite element (FE) simulations and experimental analyses. Based on compression test results of the low-alloy steel, a deformation processing map was generated using the superposition approach between the dynamic materials model (DMM) and Ziegler's instability criterion. The deformation processing map allowed determination of the optimum process conditions for the tower flange material. Within the FE simulations of the ingot breakdown process, the Cockcroft-Latham criterion, which considers ductile fracture, was used to predict the possibility of forming defects during the hot working process. In general, the critical value for the ductile fracture of steel is 0.74. During the ingot-breakdown under optimum process conditions, the actual tower flange forgings exhibited a relatively uniform shape without any forming defects.

Development of Hot and Cold Forging Process for Manufacturing a Hub of Dual Clutch Transmission (변속기용 허브 부품 제조를 위한 열간 및 냉간 복합단조 공정 개발)

  • Jo, A.R.;Jeong, M.S.;Lee, S.K.;Cho, Y.J.;Hwang, S.K.
    • Transactions of Materials Processing
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    • v.28 no.6
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    • pp.321-327
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    • 2019
  • In this study, a hot and cold forging process was investigated to produce a complex-shaped hub of dual clutch transmission with low material loss and high productivity. The process was designed by the commercial finite element (FE) analysis program, DEFORM-2D (hot forging) and 3D (cold forging). And, the material flow and ductile fracture characteristics were studied to check the surface crack initiation of the specimen. The simulation results indicated that the proposed process could manufacture the complex-shaped hub with no surface crack and high-efficiency compared to the conventional machining process. For verification the numerical results, the hub of the SCM440 was fabricated by the proposed process and the mechanical properties and microstructure evolution were studied. It was demonstrated that the suggested hot and cold forging process might be useful in producing the key components of the automobile industry as a high-efficiency and environmentally friendly process.

Prevention of Internal Defects of Cold Extruded Planetary Gears (냉간 압출된 유성기어의 내부결함 방지)

  • Lee, J.-H.;Choi, J.;Lee, Y.-S.;Choi, S.-H.
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.12
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    • pp.168-173
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    • 1999
  • It is investigated that internal defect of planetary gear which consists of two gears with different number of teeth on both side. The internal defect, central burst, begin to form at the place of adiabatic shear band which usually has maximum ductile fracture value during the forming operation, forward and backward extrusion. It makes the plastic forming of planetary gear difficult. The prediction of defect to minimize the cost to produce the planetary gear. The finite element simulation code DEFORM is applied to analyze the defects. In the analysis, the toothed gears are assumed as axisymmetric cylinders whose diameters are equal to those of pitch circles of the each gears. Experiments were carried out with the SCM415 alloy steel as billet material and AIDA 630-ton knuckle-joint press. The calculated results and experimental inspections are compared to design a die and blank without defects and the results are useful to predict the internal defect.

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Ductile Failure Simulation of Tensile Plates with Multiple Through-Wall Cracks Based on Damage Mechanics (유한요소 손상 해석을 이용한 다중 관통균열 인장시편의 연성 파괴 시뮬레이션)

  • Jeon, Jun-Young;Kim, Nak-Hyun;Oh, Chang-Sik;Kim, Yun-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.245-252
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    • 2012
  • This paper proposes a simple numerical method, based on the stress-modified fracture strain-damage model with the stress-reduction technique, for predicting the failure behaviors of ductile plates with multiple through-wall cracks. This technique is implemented using the user-defined subroutines provided in ABAQUS. For validation, the results simulated using the proposed method are compared with published experimental data of Japanese researchers.

The investigation of rock cutting simulation based on discrete element method

  • Zhu, Xiaohua;Liu, Weiji;Lv, Yanxin
    • Geomechanics and Engineering
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    • v.13 no.6
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    • pp.977-995
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    • 2017
  • It is well accepted that rock failure mechanism influence the cutting efficiency and determination of optimum cutting parameters. In this paper, an attempt was made to research the factors that affect the failure mechanism based on discrete element method (DEM). The influences of cutting depth, hydrostatic pressure, cutting velocity, back rake angle and joint set on failure mechanism in rock-cutting are researched by PFC2D. The results show that: the ductile failure occurs at shallow cutting depths, the brittle failure occurs as the depth of cut increases beyond a threshold value. The mean cutting forces have a linear related to the cutting depth if the cutting action is dominated by the ductile mode, however, the mean cutting forces are deviate from the linear relationship while the cutting action is dominated by the brittle mode. The failure mechanism changes from brittle mode with larger chips under atmospheric conditions, to ductile mode with crushed chips under hydrostatic conditions. As the cutting velocity increases, a grow number of micro-cracks are initiated around the cutter and the volume of the chipped fragmentation is decreasing correspondingly. The crack initiates and propagates parallel to the free surface with a smaller rake angle, but with the rake angle increases, the direction of crack initiation and propagation is changed to towards the intact rock. The existence of joint set have significant influence on crack initiation and propagation, it makes the crack prone to propagate along the joint.