The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Jeong Whan Yoon - One of the best experts on this subject based on the ideXlab platform.
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Orthotropic ductile Fracture Criterion based on linear transformation
Journal of Physics: Conference Series, 2017Co-Authors: Jeong Whan Yoon, Shunying Zhang, Tb StoughtonAbstract:Accurate modelling of orthotropic ductile Fracture is key to carry out reliable numerical prediction of rupture in plastic deformation of lightweight metals, such as ultra high strength steel, aluminum alloys, titanium alloys and magnesium alloys. Experiments are conducted for an aluminum alloy in shear, uniaxial tension, plane strain tension along the rolling direction, the diagonal direction and the transverse direction. Loading processes are recorded and Fracture strain is measured by analysis of deformation with digital image correlation. First, isotropic Fracture behavior is modeled by both linear model (Maximum Shear Stress (MSS) plus mean stress) and nonlinear model (Hosford yield function plus mean stress) considering different triaxiality conditions. It is observed that the mean stress model shows significant difference in the compression area compared to Mohr Coulomb-based normal stress model and a new isotropic model with the mean stress term shows a good correlation for AA 6k21. This approach is extended to an anisotropic ductile Fracture Criterion based on linear transformation. The anisotropic ductile Fracture Criterion is applied to model orthotropic Fracture strain in shear, uniaxial tension and plane strain tension. The predicted anisotropy in ductile Fracture is compared with experimental results for the verification of its accuracy. The comparison indicates that the proposed anisotropic ductile Fracture Criterion accurately models orthotropic ductile Fracture in various loading conditions in shear, uniaxial tension and plane strain tension.
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Prediction of Fracture initiation in square cup drawing of DP980 using an anisotropic ductile Fracture Criterion
Journal of Physics: Conference Series, 2017Co-Authors: Namsu Park, Hoon Huh, Jeong Whan YoonAbstract:This paper deals with the prediction of Fracture initiation in square cup drawing of DP980 steel sheet with the thickness of 1.2 mm. In an attempt to consider the influence of material anisotropy on the Fracture initiation, an uncoupled anisotropic ductile Fracture Criterion is developed based on the Lou - Huh ductile Fracture Criterion. Tensile tests are carried out at different loading directions of 0°, 45°, and 90° to the rolling direction of the sheet using various specimen geometries including pure shear, dog-bone, and flat grooved specimens so as to calibrate the parameters of the proposed Fracture Criterion. Equivalent plastic strain distribution on the specimen surface is computed using Digital Image Correlation (DIC) method until surface crack initiates. The proposed Fracture Criterion is implemented into the commercial finite element code ABAQUS/Explicit by developing the Vectorized User-defined MATerial (VUMAT) subroutine which features the non-associated flow rule. Simulation results of the square cup drawing test clearly show that the proposed Fracture Criterion is capable of predicting the Fracture initiation with sufficient accuracy considering the material anisotropy.
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Anisotropic ductile Fracture Criterion based on linear transformation
International Journal of Plasticity, 2017Co-Authors: Jeong Whan YoonAbstract:Abstract An anisotropic ductile Fracture Criterion is proposed for ductile Fracture of lightweight metals. The ductile Fracture Criterion couples effect of stress triaxiality on void growth, and assumes the shear linking-up of voids governed by the largest shear stress. The Criterion is developed based on an isotropic strain rate potential computed from an isotropic damage equivalent strain rate vector, which is mapped from the plastic strain rate vector by a forth order linear transformation tensor. The proposed anisotropic ductile Fracture Criterion is applied to depict anisotropic ductile Fracture of AA 6K21 in shear, uniaxial tension and plane strain tension along different loading directions, and the balanced biaxial tension. The predicted Fracture strain and Fracture locus are compared with experimental results for the verification of the proposed Criterion. The comparison demonstrates that the ductile Fracture Criterion properly models the anisotropy in ductile Fracture under shear, uniaxial tension, plane strain tension and balanced biaxial tension with high accuracy. It shows that the proposed anisotropic ductile Fracture Criterion can be utilized to predict the onset of ductile Fracture in plastic deformation and metal forming of lightweight metals with approximately proportional loading.
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Linear transformation based orthotropic shear ductile Fracture Criterion for lightweight metals
2017Co-Authors: Yanshan Lou, Jeong Whan YoonAbstract:Accurate modelling of orthotropic ductile Fracture is key to carry out reliable numerical prediction of rupture in plastic deformation of lightweight metals, such as ultra high strength steel, aluminum alloys, titanium alloys and magnesium alloys. Experiments are conducted for an aluminum alloy in shear, uniaxial tension, plane strain tension along rolling direction, diagonal direction and transverse direction as well as the balanced biaxial tension of the Nakajima test. Loading processes are recorded and Fracture strain is measured by analysis of deformation with digital image correlation. Fracture behavior is modelled by a shear ductile Fracture Criterion of DF2016 along different loading directions. It is observed that anisotropy in ductile Fracture cannot be correctly described by an isotropic ductile Fracture Criterion. Thus, an anisotropic ductile Fracture Criterion is proposed from a shear ductile Fracture Criterion of DF2014 based on linear transformation of the plastic strain vector into an isotr...
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A shear ductile Fracture Criterion for metal forming
Journal of Physics: Conference Series, 2016Co-Authors: Yanshan Lou, Jeong Whan YoonAbstract:In this paper, an uncoupled shear ductile Fracture Criterion is developed for prediction of ductile Fracture in sheet metal forming from shear to balanced biaxial tension. The ductile Fracture Criterion is calibrated by four tests of sheet metal: shear tests, uniaxial tension, plane strain tension and the Nakajima test. Specimens are designed for AA6082 T6 (t1.0) for the calibration of the proposed ductile Fracture Criterion. The calibrated ductile Fracture Criterion is then implemented into numerical simulation for the prediction of ductile Fracture of the aluminum alloy. For the purpose of comparison, onset of ductile Fracture is also estimated by MMC3, DF2012 and DF2014 criteria. The comparison indicates that the developed Criterion can accurately predict onset of ductile Fracture for all four loading conditions, but the other three criteria can only provide reasonable prediction for three tests. Accordingly, the newly developed ductile Fracture Criterion is suggested to be used in prediction of ductile Fracture for sheet metal forming in wide loading condition from shear to the balanced biaxial tension. Discussion on calibration of this ductile Fracture Criterion also indicates that the ductile Fracture Criterion can be employed in estimation of ductile Fracture for bulk metal forming processes with better predictability.
Yanshan Lou - One of the best experts on this subject based on the ideXlab platform.
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Prediction of ductile Fracture for Al6016-T4 with a ductile Fracture Criterion: Experiment and simulation:
International Journal of Damage Mechanics, 2019Co-Authors: Saijun Zhang, Zhaohui Shen, Chi Zhou, Yanshan LouAbstract:The key point in this paper is the prediction of the onset of ductile Fracture with a newly proposed ductile Fracture Criterion in various stress state ranging from shear to uniaxial tension. A ser...
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Linear transformation based orthotropic shear ductile Fracture Criterion for lightweight metals
2017Co-Authors: Yanshan Lou, Jeong Whan YoonAbstract:Accurate modelling of orthotropic ductile Fracture is key to carry out reliable numerical prediction of rupture in plastic deformation of lightweight metals, such as ultra high strength steel, aluminum alloys, titanium alloys and magnesium alloys. Experiments are conducted for an aluminum alloy in shear, uniaxial tension, plane strain tension along rolling direction, diagonal direction and transverse direction as well as the balanced biaxial tension of the Nakajima test. Loading processes are recorded and Fracture strain is measured by analysis of deformation with digital image correlation. Fracture behavior is modelled by a shear ductile Fracture Criterion of DF2016 along different loading directions. It is observed that anisotropy in ductile Fracture cannot be correctly described by an isotropic ductile Fracture Criterion. Thus, an anisotropic ductile Fracture Criterion is proposed from a shear ductile Fracture Criterion of DF2014 based on linear transformation of the plastic strain vector into an isotr...
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A shear ductile Fracture Criterion for metal forming
Journal of Physics: Conference Series, 2016Co-Authors: Yanshan Lou, Jeong Whan YoonAbstract:In this paper, an uncoupled shear ductile Fracture Criterion is developed for prediction of ductile Fracture in sheet metal forming from shear to balanced biaxial tension. The ductile Fracture Criterion is calibrated by four tests of sheet metal: shear tests, uniaxial tension, plane strain tension and the Nakajima test. Specimens are designed for AA6082 T6 (t1.0) for the calibration of the proposed ductile Fracture Criterion. The calibrated ductile Fracture Criterion is then implemented into numerical simulation for the prediction of ductile Fracture of the aluminum alloy. For the purpose of comparison, onset of ductile Fracture is also estimated by MMC3, DF2012 and DF2014 criteria. The comparison indicates that the developed Criterion can accurately predict onset of ductile Fracture for all four loading conditions, but the other three criteria can only provide reasonable prediction for three tests. Accordingly, the newly developed ductile Fracture Criterion is suggested to be used in prediction of ductile Fracture for sheet metal forming in wide loading condition from shear to the balanced biaxial tension. Discussion on calibration of this ductile Fracture Criterion also indicates that the ductile Fracture Criterion can be employed in estimation of ductile Fracture for bulk metal forming processes with better predictability.
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new ductile Fracture Criterion for prediction of Fracture forming limit diagrams of sheet metals
International Journal of Solids and Structures, 2012Co-Authors: Yanshan Lou, S. J. Lim, Hoon Huh, Keunhwan PackAbstract:Abstract A ductile Fracture Criterion is newly proposed to model Fracture behavior of sheet metals for nucleation, growth and shear coalescence of voids during plastic deformation. In the new ductile Fracture Criterion, void nucleation is described as a function of the equivalent plastic strain, void growth is a function of the stress triaxiality and void coalescence is controlled by the normalized maximal shear stress. The new ductile Fracture Criterion is applied to construct a Fracture forming limit diagram (FFLD) of a dual phase steel sheets of DP780 (1.0t). The FFLD is approximated using both the reverse engineering method and circle grid analysis (CGA) since DP780 fails with slight thickness reduction from the analysis of the Fracture surface. Predicted FFLDs are compared to experimental results to validate the performance of the new Criterion in the intermediate stress triaxiality between 1/3 and 2/3. The new Criterion is also applied to construct the Fracture locus of Al 2024-T351 ( Bao and Wierzbicki, 2004 ) to validate the performance of the new Criterion in the low and negative stress triaxiality. The Fracture locus constructed by the new Criterion are close to the experimental data points for all these two materials in a wide stress range from the uniaxial compression to the balanced biaxial tension. The new ductile Fracture Criterion is recommended to be utilized in finite element analysis to predict the onset of ductile Fracture of sheet metals.
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Formability Prediction of Advanced High Strength Steel with a New Ductile Fracture Criterion
2011Co-Authors: Yanshan Lou, S. J. Lim, Jeehyang Huh, Hoon HuhAbstract:A ductile Fracture Criterion is newly proposed to accurately predict forming limit diagrams (FLD) of sheet metals. The new ductile Fracture Criterion is based on the effect of the non‐dimensional stress triaxiality, the stress concentration factor and the effective plastic strain on the nucleation, growth and coalescence of voids. The new ductile Fracture Criterion has been applied to estimate the formability of four kind advanced high strength steels (AHSS): DP780, DP980, TRIP590, and TWIP980. FLDs predicted are compared with experimental results and those predicted by other ductile Fracture criteria. The comparison demonstrates that FLDs predicted by the new ductile Fracture Criterion are in better agreement with experimental FLDs than those predicted by other ductile Fracture criteria. The better agreement of FLDs predicted by the new ductile Fracture Criterion is because conventional ductile Fracture criteria were proposed for Fracture prediction in bulk metal forming while the new one is proposed to predict the onset of Fracture in sheet metal forming processes.
Zhai Jiang-bo - One of the best experts on this subject based on the ideXlab platform.
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Prediction of the forming limit of sheet metals based on Oyane ductile Fracture Criterion
Materials Science and Technology, 2009Co-Authors: Zhai Jiang-boAbstract:Oyane ductile Fracture Criterion was introduced into numerical simulation to predict the forming limit of sheet metals.Material constants in the Criterion were obtained by testing the Fracture strains of uniaxial tensile and plan strain stretching.The forming limit was predicted by applying the values of stress and strain of each time step obtained from numerical simulation to the ductile Fracture Criterion.The results indicate that the combination of ductile Fracture Criterion and numerical simulation can successfully predict the forming limit diagram of sheet metals.
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Prediction of sheet metal forming limit diagram by applying ductile Fracture Criterion
Forging and Stamping Technology, 2007Co-Authors: Zhai Jiang-boAbstract:To predict the forming limit diagrams(FLD) of sheet metals,Oyan ductile Fracture Criterion was introduced into numerical simulation.The influence of normal anisotropic coefficient on the item in different strains of the Criterion were discussed and material constants in the Criterion were obtained by testing the Fracture strains of uniaxial tensile and plan strain stretching.The forming limit was predicted in the male punch bulging test by substituting the values of stress and strain of every time step obtained from numerical simulation into ductile Fracture Criterion.Oyan ductile Fracture Criterion was applied to predict the FLD of A5182-O and SPCC.The results indicate that the combination of ductile Fracture Criterion and numerical simulation can successfully predict the forming limit diagram of sheet metals.
Hoon Huh - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Fracture initiation in square cup drawing of DP980 using an anisotropic ductile Fracture Criterion
Journal of Physics: Conference Series, 2017Co-Authors: Namsu Park, Hoon Huh, Jeong Whan YoonAbstract:This paper deals with the prediction of Fracture initiation in square cup drawing of DP980 steel sheet with the thickness of 1.2 mm. In an attempt to consider the influence of material anisotropy on the Fracture initiation, an uncoupled anisotropic ductile Fracture Criterion is developed based on the Lou - Huh ductile Fracture Criterion. Tensile tests are carried out at different loading directions of 0°, 45°, and 90° to the rolling direction of the sheet using various specimen geometries including pure shear, dog-bone, and flat grooved specimens so as to calibrate the parameters of the proposed Fracture Criterion. Equivalent plastic strain distribution on the specimen surface is computed using Digital Image Correlation (DIC) method until surface crack initiates. The proposed Fracture Criterion is implemented into the commercial finite element code ABAQUS/Explicit by developing the Vectorized User-defined MATerial (VUMAT) subroutine which features the non-associated flow rule. Simulation results of the square cup drawing test clearly show that the proposed Fracture Criterion is capable of predicting the Fracture initiation with sufficient accuracy considering the material anisotropy.
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new ductile Fracture Criterion for prediction of Fracture forming limit diagrams of sheet metals
International Journal of Solids and Structures, 2012Co-Authors: Yanshan Lou, S. J. Lim, Hoon Huh, Keunhwan PackAbstract:Abstract A ductile Fracture Criterion is newly proposed to model Fracture behavior of sheet metals for nucleation, growth and shear coalescence of voids during plastic deformation. In the new ductile Fracture Criterion, void nucleation is described as a function of the equivalent plastic strain, void growth is a function of the stress triaxiality and void coalescence is controlled by the normalized maximal shear stress. The new ductile Fracture Criterion is applied to construct a Fracture forming limit diagram (FFLD) of a dual phase steel sheets of DP780 (1.0t). The FFLD is approximated using both the reverse engineering method and circle grid analysis (CGA) since DP780 fails with slight thickness reduction from the analysis of the Fracture surface. Predicted FFLDs are compared to experimental results to validate the performance of the new Criterion in the intermediate stress triaxiality between 1/3 and 2/3. The new Criterion is also applied to construct the Fracture locus of Al 2024-T351 ( Bao and Wierzbicki, 2004 ) to validate the performance of the new Criterion in the low and negative stress triaxiality. The Fracture locus constructed by the new Criterion are close to the experimental data points for all these two materials in a wide stress range from the uniaxial compression to the balanced biaxial tension. The new ductile Fracture Criterion is recommended to be utilized in finite element analysis to predict the onset of ductile Fracture of sheet metals.
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Formability Prediction of Advanced High Strength Steel with a New Ductile Fracture Criterion
2011Co-Authors: Yanshan Lou, S. J. Lim, Jeehyang Huh, Hoon HuhAbstract:A ductile Fracture Criterion is newly proposed to accurately predict forming limit diagrams (FLD) of sheet metals. The new ductile Fracture Criterion is based on the effect of the non‐dimensional stress triaxiality, the stress concentration factor and the effective plastic strain on the nucleation, growth and coalescence of voids. The new ductile Fracture Criterion has been applied to estimate the formability of four kind advanced high strength steels (AHSS): DP780, DP980, TRIP590, and TWIP980. FLDs predicted are compared with experimental results and those predicted by other ductile Fracture criteria. The comparison demonstrates that FLDs predicted by the new ductile Fracture Criterion are in better agreement with experimental FLDs than those predicted by other ductile Fracture criteria. The better agreement of FLDs predicted by the new ductile Fracture Criterion is because conventional ductile Fracture criteria were proposed for Fracture prediction in bulk metal forming while the new one is proposed to predict the onset of Fracture in sheet metal forming processes.
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Prediction of Fracture in hub-hole expanding process using a new ductile Fracture Criterion
Journal of Materials Processing Technology, 2007Co-Authors: Js Lee, Hoon Huh, H.k. Kim, Soo Ho ParkAbstract:Abstract A hole expansion process is an important process in producing a hub-hole in a wheel disc of a vehicle. In this process, the main parameter is the formability of a material, which is expressed as the hole expansion ratio. As the hole is expanded during the process, a crack tends to occur in the upper edge of a hole. Since prediction of the forming limit by hole expansion experiments needs tremendous time and effort, an appropriate Fracture Criterion has to be developed for finite element analysis to define the forming limit of materials. This paper newly proposes a modified ductile Fracture Criterion to consider the deformation characteristics of a material accurately in a hole expansion process. In order to verify the validity of the proposed Criterion, the hole expansion process of a hub-hole is studied by finite element analysis with ABAQUS/standard considering several ductile Fracture criteria. The Fracture mode and hole expanding ratio are compared with respect to the various facture criteria. While existing criteria do not predict the Fracture mode or hole expansion ratio adequately and show deviation from experimental results of hole expansion, the newly proposed Fracture Criterion predicts the Fracture mode and the hole expanding ratio accurately.
Youngsuk Kim - One of the best experts on this subject based on the ideXlab platform.
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uncoupled ductile Fracture Criterion considering secondary void band behaviors for failure prediction in sheet metal forming
International Journal of Mechanical Sciences, 2020Co-Authors: Hung Quach, Jinjae Kim, Ductoan Nguyen, Youngsuk KimAbstract:Abstract A new phenomenological ductile Fracture Criterion that is proposed. The proposed model is associated with the micro mechanisms of void nucleation, void growth, and evolution of void coalescence. The secondary voids band and rotation of voids effect are considered in the new ductile Fracture Criterion. A series of upsetting test results of aluminum 2024-T351 and TRIP RA-K40/70 steel are used to construct and compare the accuracy of Fracture locus proposed by new ductile Fracture Criterion, Modified Mohr-Coulomb Criterion and extend Lou-Huh Criterion. The Fracture locus constructed using the proposed Criterion is close to the experimental data points over a wide stress state range from uniaxial compression to balanced biaxial tension. Then, a series of upsetting tests and square cup drawing tests are conducted with Al6014-T4 to evaluate the accuracy of the proposed Criterion. All results indicate that the proposed ductile Fracture Criterion can be utilized for predicting initial Fracture in sheet metal forming.
