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T Prasanna S Kumar - One of the best experts on this subject based on the ideXlab platform.
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effect of geometric parameters on Strain Strain inhomogeneity and peak pressure in equal channel angular pressing a study based on 3d finite element analysis
Journal of Manufacturing Processes, 2015Co-Authors: Basavaraj V Patil, Uday Chakkingal, T Prasanna S KumarAbstract:Abstract Equal channel angular pressing (ECAP) is currently being widely investigated because of its potential to produce ultra-fine grained microstructures in metals and alloys. Considerable research has been reported on finite element analysis (FEA) of this process, assuming 2d Plane Strain condition. The 2d models do not give details of Strain distribution in the work-piece. Reports of all the researches are on effect of one-parameter-at-a-time. Combined effect of all geometric parameters is not reported. This paper aims in fulfilling the gap. In the present work 3D FEA of ECAP process was carried out for different combinations of channel angle, inner and outer corner radii. Results in terms of peak pressure, Strain and Strain inhomogeneity were obtained and analyzed by analysis of mean (ANOM). Main effects and interaction effect of all geometric parameters were quantified by analysis of variance (ANOVA). From the analysis it was found that the peak pressure is largely influenced by channel angle. To obtain desired Strain the most important factors are channel angle and outer corner radius. Outer corner radius has the largest influence followed by channel angle on the Strain inhomogeneity. There exists an optimum outer corner for which Strain inhomogeneity is minimum, which depends on the channel angle. Inner corner alone has no influence on the Strain inhomogeneity but its interaction with channel angle has some influence.
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study of channel angle influence on material flow and Strain inhomogeneity in equal channel angular pressing using 3d finite element simulation
Journal of Materials Processing Technology, 2009Co-Authors: Patil V Basavaraj, Uday Chakkingal, T Prasanna S KumarAbstract:Equal channel angular pressing (ECAP) is currently being widely investigated because of its potential to produce ultra-fine grained microstructures in metals and alloys. A sound knowledge of the plastic deformation and Strain distribution is necessary for understanding the relationships between Strain inhomogeneity and geometry of die. Considerable research has been reported on finite element analysis of this process, assuming 2d Plane Strain condition. The 2d models are not suitable due to the component geometry, especially for workpiece with cylindrical cross-section. In the present work 3D simulation of ECAP process was carried out, using ABAQUS/Standard software, for different channel angles for a Strain hardening aluminium alloy (AA6101). Strain inhomogeneity is presented and discussed for all cases. Pattern of variation of Strain along some selected radial lines in steady-state zone is presented.
Patil V Basavaraj - One of the best experts on this subject based on the ideXlab platform.
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study of channel angle influence on material flow and Strain inhomogeneity in equal channel angular pressing using 3d finite element simulation
Journal of Materials Processing Technology, 2009Co-Authors: Patil V Basavaraj, Uday Chakkingal, T Prasanna S KumarAbstract:Equal channel angular pressing (ECAP) is currently being widely investigated because of its potential to produce ultra-fine grained microstructures in metals and alloys. A sound knowledge of the plastic deformation and Strain distribution is necessary for understanding the relationships between Strain inhomogeneity and geometry of die. Considerable research has been reported on finite element analysis of this process, assuming 2d Plane Strain condition. The 2d models are not suitable due to the component geometry, especially for workpiece with cylindrical cross-section. In the present work 3D simulation of ECAP process was carried out, using ABAQUS/Standard software, for different channel angles for a Strain hardening aluminium alloy (AA6101). Strain inhomogeneity is presented and discussed for all cases. Pattern of variation of Strain along some selected radial lines in steady-state zone is presented.
Tomasz Wierzbicki - One of the best experts on this subject based on the ideXlab platform.
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prediction of Plane Strain fracture of ahss sheets with post initiation softening
International Journal of Solids and Structures, 2010Co-Authors: Tomasz WierzbickiAbstract:Abstract In this investigation, the three-parameter Modified Mohr–Coulomb (MMC) fracture model and the determination of the material parameters are briefly described. The formulation of the post-initiation behavior is proposed by defining both the explicit softening law and the incremental damage evolution law. As opposed to the existing attempts to simulate slant fracture with material weakening before crack formation, softening is assumed to occur only in the post-initiation range. The justification of this assumption can be provided by the interrupted fracture tests, for example, Spencer et al. (2002) . Element deletion with a gradual loss of strength is used to simulate crack propagation after fracture initiation. The main emphasis of the paper is the numerical prediction of slant fracture which is almost always observed in thin sheets. For that purpose, VUMAT subroutines of ABAQUS are coded with post-initiation behavior for both shell elements and Plane Strain elements. Fracture of flat-grooved tensile specimens cut from advanced high strength steel (AHSS) sheets are simulated by 2d Plane Strain element and shell element models.
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prediction of Plane Strain fracture of ahss sheets with post initiation softening
International Journal of Solids and Structures, 2010Co-Authors: Yaning Li, Tomasz WierzbickiAbstract:Abstract In this investigation, the three-parameter Modified Mohr–Coulomb (MMC) fracture model and the determination of the material parameters are briefly described. The formulation of the post-initiation behavior is proposed by defining both the explicit softening law and the incremental damage evolution law. As opposed to the existing attempts to simulate slant fracture with material weakening before crack formation, softening is assumed to occur only in the post-initiation range. The justification of this assumption can be provided by the interrupted fracture tests, for example, Spencer et al. (2002) . Element deletion with a gradual loss of strength is used to simulate crack propagation after fracture initiation. The main emphasis of the paper is the numerical prediction of slant fracture which is almost always observed in thin sheets. For that purpose, VUMAT subroutines of ABAQUS are coded with post-initiation behavior for both shell elements and Plane Strain elements. Fracture of flat-grooved tensile specimens cut from advanced high strength steel (AHSS) sheets are simulated by 2d Plane Strain element and shell element models.
R Narasimhan - One of the best experts on this subject based on the ideXlab platform.
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stationary crack tip fields in elastic plastic solids an overview of recent numerical simulations
Journal of Physics D, 2009Co-Authors: R Narasimhan, H Y Subramanya, S D Patil, Parag Tandaiya, U RamamurtyAbstract:In this paper, an overview of some recent numerical simulations of stationary crack tip fields in elastic-plastic solids is presented. First, asymptotic analyses carried out within the framework of 2d Plane Strain or Plane stress conditions in both pressure insensitive and pressure sensitive plastic solids are reviewed. This is followed by discussion of salient results obtained from recent computational studies. These pertain to 3D characteristics of elastic-plastic near-front fields under mixed mode loading, mechanics of fracture and simulation of near-tip shear banding process of amorphous alloys and influence of crack tip conStraint on the structure of near-tip fields in ductile single crystals. These results serve to illustrate several important features associated with stress and Strain distributions near the crack tip and provide the foundation for understanding the operative failure mechanisms. The paper concludes by highlighting some of the future prospects for this field of study.
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crack tip fields in a single edge notched aluminum single crystal specimen
Journal of Engineering Materials and Technology-transactions of The Asme, 2008Co-Authors: Swapnil D Patil, R Narasimhan, P Biswas, Raja K MishraAbstract:We report a combined experimental and computational study of a low conStraint aluminum single crystal fracture geometry and investigate the near-tip stress and Strain fields. To this end, a single edge notched tensile (SENT) specimen is considered. A notch, with a radius of 50 µm, is taken to lie in the (010) Plane and its front is aligned along the [101] direction. Experiments are conducted by subjecting the specimen to tensile loading using a special fixture inside a scanning electron microscope chamber. Both SEM micrographs and electron back-scattered diffraction (EBSD) maps are obtained from the near-tip region. The experiments are complemented by performing 3D and 2d Plane Strain finite element simulations within a continuum crystal plasticity framework assuming an isotropic hardening response characterized by the Pierce–Asaro–Needleman model. The simulations show a distinct slip band forming at about 55 deg with respect to the notch line corresponding to slip on (11-bar 1)[011] system, which corroborates well with experimental data. Furthermore, two kink bands occur at about 45 deg and 90 deg with respect to the notch line within which large rotations in the crystal orientation take place. These predictions are in good agreement with the EBSD observations. Finally, the near-tip angular variations of the 3D stress and plastic Strain fields in the low conStraint SENT fracture geometry are examined in detail.
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a numerical investigation of loss of crack tip conStraint in a dynamically loaded ductile specimen
Journal of The Mechanics and Physics of Solids, 2000Co-Authors: Sumit Basu, R NarasimhanAbstract:The objectives of this paper are to study the applicability of a two-parameter (J-Q) characterisation of the elastic-plastic crack tip fields in a dynamically loaded ductile specimen and to ascertain the e€ect of loading rate J on the triaxiality parameter Q. To this end, 2d (Plane Strain) large deformation finite element analyses of a single edge notched specimen (SEN(T)) subjected to a tensile stress pulse are conducted. The material is assumed to obey the $J_2$ flow theory of plasticity with small elastic Strains and both rate independent and rate dependent behaviour are considered. The results demonstrate that even a deeply cracked SEN(T) specimen which maintains high triaxiality under quasi-static loading can exhibit progressive loss of triaxiality as the loading rate increases. Since this behaviour is observed for both rate independent and rate dependent case, it is attributed to inertial e€ects. The above phenomenon can satisfactorily explain retarded micro-void growth rates near a notch tip, and strong elevation in the dynamic fracture toughness at high loading rates, which have been reported in recent computational and experimental studies.
Raja K Mishra - One of the best experts on this subject based on the ideXlab platform.
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microstructure based finite element analysis of Strain localization behavior in aa5754 aluminum sheet
Acta Materialia, 2008Co-Authors: Mukesh Jain, David Wilkinson, Raja K MishraAbstract:A finite element (FE) analysis incorporating particles and grain structure is used to study the localization behavior of direct chill cast (DC) and strip cast (CC) AA5754 alloy sheet. A two-dimensional (2d) Plane stress FE model is used to simulate deformation of a sample under uniaxial tension prior to necking. A 2d Plane Strain model is then used to simulate the post-necking behavior, up to fracture. The Plane stress model shows that the Strain required for the initiation of necking is similar in both materials, determined predominately by grain-level inhomogeneity, with constituent particles altering the localization path and localization Strains, but only weakly. The Plane Strain model shows more through-thickness thinning during post-necking deformation of DC sheets compared with CC sheets. The CC material is also prone to shear-type failure, while the DC material exhibits a cup–cone-type failure. These differences arise from the microstructural difference between the two samples, where CC sheets contain more intermetallic particles in stringers compared with the DC sheets. This two-stage model is validated by experimental data which show similar limit Strains in the DC and CC sheets but quite different fracture Strains and fracture surface geometries.
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crack tip fields in a single edge notched aluminum single crystal specimen
Journal of Engineering Materials and Technology-transactions of The Asme, 2008Co-Authors: Swapnil D Patil, R Narasimhan, P Biswas, Raja K MishraAbstract:We report a combined experimental and computational study of a low conStraint aluminum single crystal fracture geometry and investigate the near-tip stress and Strain fields. To this end, a single edge notched tensile (SENT) specimen is considered. A notch, with a radius of 50 µm, is taken to lie in the (010) Plane and its front is aligned along the [101] direction. Experiments are conducted by subjecting the specimen to tensile loading using a special fixture inside a scanning electron microscope chamber. Both SEM micrographs and electron back-scattered diffraction (EBSD) maps are obtained from the near-tip region. The experiments are complemented by performing 3D and 2d Plane Strain finite element simulations within a continuum crystal plasticity framework assuming an isotropic hardening response characterized by the Pierce–Asaro–Needleman model. The simulations show a distinct slip band forming at about 55 deg with respect to the notch line corresponding to slip on (11-bar 1)[011] system, which corroborates well with experimental data. Furthermore, two kink bands occur at about 45 deg and 90 deg with respect to the notch line within which large rotations in the crystal orientation take place. These predictions are in good agreement with the EBSD observations. Finally, the near-tip angular variations of the 3D stress and plastic Strain fields in the low conStraint SENT fracture geometry are examined in detail.