The Experts below are selected from a list of 8340 Experts worldwide ranked by ideXlab platform
Frederic Barlat - One of the best experts on this subject based on the ideXlab platform.
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an effective computational algorithm for rate independent Crystal Plasticity based on a single Crystal yield surface with an application to tube hydroforming
International Journal of Plasticity, 2007Co-Authors: A Zamiri, Farhang Pourboghrat, Frederic BarlatAbstract:Up to now, several computational methods have been proposed for Crystal Plasticity Models. The main objective of these computational methods has been to overcome the problem with the non-uniqueness of active slip systems during the plastic deformation of a single Crystal. Crystal Plasticity Models based on a single Crystal yield function have been proposed as alternative algorithms to overcome this problem. But the problem with these Models is that they use a highly non-linear yield function for the Crystal, which makes them computationally expensive. In this paper, a computational method is proposed that would modify a single Crystal yield function in order to make it computationally efficient. Also to better capture experimental data, a new parameter is introduced into the single Crystal yield function to make it more flexible. For verification, this Crystal Plasticity Model was directly applied for the simulation of hydroforming of an extruded aluminum tube under complex strain paths. It was found that the current Model is considerably faster than the previous Crystal Plasticity Model based on a power-law type single Crystal yield surface. Due to its computational efficiency, the current Crystal Plasticity Model can also be used to calculate the anisotropy coefficients of phenomenological yield functions.
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anisotropic strain hardening behavior in simple shear for cube textured aluminum alloy sheets
International Journal of Plasticity, 2005Co-Authors: Frederic Barlat, J Gracio, E F RauchAbstract:Abstract Finite element (FE) simulations of the simple shear test were conducted for 1050-O and 6022-T4 aluminum alloy sheet samples. Simulations were conducted with two different constitutive equations to account for plastic anisotropy: Either a recently proposed anisotropic yield function combined with an isotropic strain hardening law or a Crystal Plasticity Model. The FE computed shear stress–shear strain curves were compared to the experimental curves measured for the two materials in previous works. Both phenomenological and polyCrystal approaches led to results consistent with the experiments. These comparisons lead to a discussion concerning the assessment of anisotropic hardening in the simple shear test.
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anisotropic strain hardening behavior in simple shear for cube textured aluminum alloy sheets
International Journal of Plasticity, 2005Co-Authors: Frederic Barlat, J Gracio, E F RauchAbstract:Abstract Finite element (FE) simulations of the simple shear test were conducted for 1050-O and 6022-T4 aluminum alloy sheet samples. Simulations were conducted with two different constitutive equations to account for plastic anisotropy: Either a recently proposed anisotropic yield function combined with an isotropic strain hardening law or a Crystal Plasticity Model. The FE computed shear stress–shear strain curves were compared to the experimental curves measured for the two materials in previous works. Both phenomenological and polyCrystal approaches led to results consistent with the experiments. These comparisons lead to a discussion concerning the assessment of anisotropic hardening in the simple shear test.
David L Mcdowell - One of the best experts on this subject based on the ideXlab platform.
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Crystal Plasticity Model for bcc iron atomistically informed by kinetics of correlated kinkpair nucleation on screw dislocation
Journal of The Mechanics and Physics of Solids, 2014Co-Authors: Sankar Narayanan, David L McdowellAbstract:Abstract The mobility of dislocation in body-centered cubic (BCC) metals is controlled by the thermally activated nucleation of kinks along the dislocation core. By employing a recent interatomic potential and the Nudged Elastic Band method, we predict the atomistic saddle-point state of 1 / 2 〈 111 〉 screw dislocation motion in BCC iron that involves the nucleation of correlated kinkpairs and the resulting double superkinks. This unique process leads to a single-humped minimum energy path that governs the one-step activation of a screw dislocation to move into the adjacent { 110 } Peierls valley, which contrasts with the double-humped energy path and the two-step transition predicted by other interatomic potentials. Based on transition state theory, we use the atomistically computed, stress-dependent kinkpair activation parameters to inform a coarse-grained Crystal Plasticity flow rule. Our atomistically-informed Crystal Plasticity Model quantitatively predicts the orientation dependent stress–strain behavior of BCC iron single Crystals in a manner that is consistent with experimental results. The predicted temperature and strain-rate dependencies of the yield stress agree with experimental results in the 200–350 K temperature regime, and are rationalized by the small activation volumes associated with the kinkpair-mediated motion of screw dislocations.
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microstructure sensitive Modeling of polyCrystalline in 100
International Journal of Plasticity, 2008Co-Authors: M M Shenoy, Yustianto Tjiptowidjojo, David L McdowellAbstract:Abstract A rate dependent, microstructure-sensitive Crystal Plasticity Model is formulated for correlating the mechanical behavior of a polyCrystalline Ni-base superalloy IN 100 at 650 °C. This Model has the capability to capture first order effects on the stress–strain response due to (a) grain size, (b) γ′ precipitate size distribution, and (c) γ′ precipitate volume fraction. Experimental fatigue data with variable strain rates are used to calibrate the Model for several distinct IN 100 microstructures (grain size, precipitate size distributions and volume fractions) obtained from thermomechanical processing. Physically based hardening laws are employed to evolve the dislocation densities for each slip system, taking into consideration the dislocation interaction mechanisms. The calibrated Crystal Plasticity Model is used to inform microstructure dependent parameters of a macroscopic internal state variable (ISV) Model, which is computationally feasible for use in component scale notch root analyses. A hierarchical methodology is outlined to embed this microstructure-dependence in the macroscale Model.
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a three dimensional Crystal Plasticity Model for duplex ti 6al 4v
International Journal of Plasticity, 2007Co-Authors: Jason R Mayeur, David L McdowellAbstract:Abstract A rate dependent Crystal Plasticity Model for the α/β Ti–Al alloy Ti–6Al–4V with duplex microstructure is developed and presented herein. Duplex Ti–6Al–4V is a dual-phase alloy consisting of an hcp structured matrix primary α-phase and secondary lamellar α + β domains that are composed of alternating layers of secondary α laths and bcc structured residual β laths. The Model accounts for distinct three-dimensional slip geometry for each phase, anisotropic and length scale dependent slip system strengths, the non-planar dislocation core structure of prismatic screw dislocations in the primary α-phase, and Crystallographic texture. The Model is implemented in the general purpose finite element code (ABAQUS, 2005. Ver 6.5, Hibbitt, Karlsson, and Sorensen, Inc., Pawtucket, RI) via a UMAT subroutine.
J Segurado - One of the best experts on this subject based on the ideXlab platform.
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simulation of the hall petch effect in fcc polyCrystals by means of strain gradient Crystal Plasticity and fft homogenization
Journal of The Mechanics and Physics of Solids, 2020Co-Authors: S Haouala, J Llorca, J Segurado, S LucariniAbstract:Abstract The influence of grain size on the flow stress of various FCC polyCrystals (Cu, Al, Ag and Ni) has been analyzed by means of computational homogenization of a representative volume element of the microstructure using a FFT approach in combination with a strain gradient Crystal Plasticity Model. The density of geometrically necessary dislocations resulting from the incompatibility of plastic deformation among different Crystals was obtained from the Nye tensor, which was efficiently obtained from the curl operation in the Fourier space. The simulation results were in good agreement with the experimental data for Cu, Al, Ag and Ni polyCrystals for grain sizes > 20 µm and strains
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Modeling cyclic deformation of inconel 718 superalloy by means of Crystal Plasticity and computational homogenization
International Journal of Solids and Structures, 2017Co-Authors: A Cruzado, J Llorca, J SeguradoAbstract:Abstract A Crystal Plasticity computational homogenization framework is proposed to simulate the cyclic deformation of polyCrystalline alloys that exhibit Bauschinger effect, mean stress relaxation, ratcheting and cyclic softening, as it happens in many Nickel based superalloys. The response of the Crystals is taken into account by means of a phenomenological viscoplastic Crystal Plasticity Model that includes the contributions of isotropic softening and kinematic hardening. The effective behavior of the polyCrystal is computed through the numerical simulation of a representative volume element of the microstructure. A linear cyclic jump approach is developed in order to reduce the computational cost for simulating a large number of cycles. The Model is validated for a wrought polyCrystalline IN718 superalloy subjected to cyclic deformation under strain control at different cyclic strain amplitudes with Rϵ 0 and − 1. The actual microstructural features (grain size and orientation distribution) are included in the Model through the representative volume element of the microstructure, while the parameters of the Crystal Plasticity Model are determined using an inverse optimization strategy based on the Levenberg–Marquardt algorithm. The Model is shown to predict accurately the evolution of the stress–strain hysteresis loops with the number of cycles, as well as the mean stress relaxation and the cyclic softening observed in the experiments.
E F Rauch - One of the best experts on this subject based on the ideXlab platform.
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anisotropic strain hardening behavior in simple shear for cube textured aluminum alloy sheets
International Journal of Plasticity, 2005Co-Authors: Frederic Barlat, J Gracio, E F RauchAbstract:Abstract Finite element (FE) simulations of the simple shear test were conducted for 1050-O and 6022-T4 aluminum alloy sheet samples. Simulations were conducted with two different constitutive equations to account for plastic anisotropy: Either a recently proposed anisotropic yield function combined with an isotropic strain hardening law or a Crystal Plasticity Model. The FE computed shear stress–shear strain curves were compared to the experimental curves measured for the two materials in previous works. Both phenomenological and polyCrystal approaches led to results consistent with the experiments. These comparisons lead to a discussion concerning the assessment of anisotropic hardening in the simple shear test.
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anisotropic strain hardening behavior in simple shear for cube textured aluminum alloy sheets
International Journal of Plasticity, 2005Co-Authors: Frederic Barlat, J Gracio, E F RauchAbstract:Abstract Finite element (FE) simulations of the simple shear test were conducted for 1050-O and 6022-T4 aluminum alloy sheet samples. Simulations were conducted with two different constitutive equations to account for plastic anisotropy: Either a recently proposed anisotropic yield function combined with an isotropic strain hardening law or a Crystal Plasticity Model. The FE computed shear stress–shear strain curves were compared to the experimental curves measured for the two materials in previous works. Both phenomenological and polyCrystal approaches led to results consistent with the experiments. These comparisons lead to a discussion concerning the assessment of anisotropic hardening in the simple shear test.
Leo A I Kestens - One of the best experts on this subject based on the ideXlab platform.
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occurrence of shear bands in rotated goss 1 1 0 1 1 0 orientations of metals with bcc Crystal structure
Scripta Materialia, 2012Co-Authors: T Nguyenminh, Jurij J Sidor, Roumen Petrov, Leo A I KestensAbstract:The occurrence of shear bands in the rotated Goss ({1 1 0}〈1 1 0〉) orientation of Fe–1.2 wt.% Si alloy was investigated by the hypothesis of the geometric softening mechanism. The reduction of Taylor factor and the orientation evolution of in-band Crystals were calculated by applying the full-constraints Taylor Crystal Plasticity Model. The presence of in-grain shear bands and particularly the Cube-oriented Crystal volumes in shear bands was predicted by the Models and confirmed by experimental electron backscattered diffraction observation.