The Experts below are selected from a list of 101553 Experts worldwide ranked by ideXlab platform
Jonathan P Belnoue - One of the best experts on this subject based on the ideXlab platform.
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a nonlocal coupled damage Plasticity Model for the analysis of ductile failure
2015Co-Authors: Giang D Nguyen, Alexander M Korsunsky, Jonathan P BelnoueAbstract:This paper presents a nonlocal coupled damage-Plasticity Model for the analysis of ductile fracture. The proposed Model makes use of both damage mechanics and Plasticity theories and hence is able to capture the pre-peak hardening and post-peak softening responses as well as the stiffness reduction of the material during the deformation and fracture processes. Nonlocal regularisation technique is used as an enhancement to the proposed damage-Plasticity Model to deal with softening related problems in the constitutive Modelling and the failure analysis. Emphasis is put on the determination of Model parameters with a novel calibration procedure, based on the experimental technique (Korsunsky and Kim, 2005) on the measurement of essential and non-essential works of fracture, proposed and effectively used for the Model calibration. It is shown that all Model parameters can be properly calibrated based on the proposed method, and experimental results, making the Model attractive for practical applications. The proposed nonlocal Model enables the stress update to be carried out pointwise, and hence facilitates the implementation of the Model in existing finite element codes. Numerical examples are used to demonstrate the capability of the proposed Model.
Curt A Bronkhorst - One of the best experts on this subject based on the ideXlab platform.
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crystal Plasticity Model for single crystal ni based superalloys capturing orientation and temperature dependence of flow stress
2021Co-Authors: Satyapriya Gupta, Curt A BronkhorstAbstract:Abstract We develop a dislocation density based crystal Plasticity Model to capture the micromechanical behavior of γ′ strengthening nickel-based superalloys. The elasto-viscoplastic Model presented here accounts for hardening behavior of both γ and γ′ which are the two phases considered in the present work. The Model includes multiple strengthening mechanisms such as Orowan stress, evolving slip resistance caused by dislocation interactions, and γ′ structural contribution to initial slip resistance. Interaction between γ and γ′, a key feature of these alloys has been Modelled in terms of back stress induced by dislocation pileup or looping around the large γ′ precipitates. Furthermore, anti-phase boundary (APB) shearing is considered as the dominant deformation mechanism for shearable γ′ precipitates. In addition to octahedral {111}⟨110⟩ slip, the Model also accounts for cube slip systems {100}⟨110⟩ which are known to be instrumental in γ′ shearing and introducing flow stress orientation dependence. Temperature dependence of the initial slip resistance is fitted against experimental observation of anomalous yielding for two different single crystal orientations. An optimization procedure based on the minimization of the error between simulated and experimental stress strain curves, is adopted to evaluate a selected group of material parameters. Subsequently, proper working of the Model is tested against an independent set of single crystal experimental data available for CMSX-4 around service temperature and MD2 at room temperature. The Model also represents a strong orientation dependence of yield stress anomaly (YSA), a salient feature of Ni-based superalloys.
Peter Grassl - One of the best experts on this subject based on the ideXlab platform.
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Modelling the failure of reinforced concrete with nonlocal and crack band approaches using the damage Plasticity Model cdpm2
2016Co-Authors: Dimitrios Xenos, Peter GrasslAbstract:A nonlocal extension of the damage-Plasticity Model CDPM2 is proposed. The performance of this extension is evaluated in comparison with a crack band version of the same Model for describing the failure of reinforced concrete. In particular, the influence of mesh size on the structural response in the form of load-displacement curves and strain distributions is studied for a reinforced concrete beam subjected to four point bending. The nonlocal Model provides mesh independent load-displacement curves and strain profiles, whereas the peak loads and strain profiles obtained with the crack band Model depend on the element size. HighlightsA new nonlocal damage-Plasticity Model has been proposed.The Model has been applied to analyse plain and reinforced concrete members.The results of the nonlocal Model are compared to those of a crack band approach.The influence of mesh size for the two Modelling approaches has been investigated.The nonlocal Model yields mesh independent results.
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full length articleModelling the failure of reinforced concrete with nonlocal and crack band approaches using the damage Plasticity Model cdpm2
2016Co-Authors: Dimitrios Xenos, Peter GrasslAbstract:A nonlocal extension of the damage-Plasticity Model CDPM2 is proposed. The performance of this extension is evaluated in comparison with a crack band version of the same Model for describing the failure of reinforced concrete. In particular, the influence of mesh size on the structural response in the form of load–displacement curves and strain distributions is studied for a reinforced concrete beam subjected to four point bending. The nonlocal Model provides mesh independent load–displacement curves and strain profiles, whereas the peak loads and strain profiles obtained with the crack band Model depend on the element size.
Mgd Marc Geers - One of the best experts on this subject based on the ideXlab platform.
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non local crystal Plasticity Model with intrinsic ssd and gnd effects
2004Co-Authors: L Laurens P Evers, Wam Marcel Brekelmans, Mgd Marc GeersAbstract:A strain gradient-dependent crystal Plasticity approach is presented to Model the constitutive behaviour of polycrystal FCC metals under large plastic deformation. In order to be capable of predicting scale dependence, the heterogeneous deformation-induced evolution and distribution of geometrically necessary dislocations (GNDs) are incorporated into the phenomenological continuum theory of crystal Plasticity. Consequently, the resulting boundary value problem accommodates, in addition to the ordinary stress equilibrium condition, a condition which sets the additional nodal degrees of freedom, the edge and screw GND densities, proportional (in a weak sense) to the gradients of crystalline slip. Next to this direct coupling between microstructural dislocation evolutions and macroscopic gradients of plastic slip, another characteristic of the presented crystal Plasticity Model is the incorporation of the GND-effect, which leads to an essentially different constitutive behaviour than the statistically stored dislocation (SSD) densities. The GNDs, by their geometrical nature of locally similar signs, are expected to influence the plastic flow through a non-local back-stress measure, counteracting the resolved shear stress on the slip systems in the undeformed situation and providing a kinematic hardening contribution. Furthermore, the interactions between both SSD and GND densities are subject to the formation of slip system obstacle densities and accompanying hardening, accountable for slip resistance. As an example problem and without loss of generality, the Model is applied to predict the formation of boundary layers and the accompanying size effect of a constrained strip under simple shear deformation, for symmetric double-slip conditions.
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crystal Plasticity Model with enhanced hardening by geometrically necessary dislocation accumulation
2002Co-Authors: L Laurens P Evers, D M Parks, Wam Marcel Brekelmans, Mgd Marc GeersAbstract:Abstract A strain gradient dependent crystal Plasticity approach is used to Model the constitutive behaviour of polycrystal FCC metals under large plastic deformation. Material points are considered as aggregates of grains, subdivided into several fictitious grain fractions: a single crystal volume element stands for the grain interior whereas grain boundaries are represented by bi-crystal volume elements, each having the crystallographic lattice orientations of its adjacent crystals. A relaxed Taylor-like interaction law is used for the transition from the local to the global scale. It is relaxed with respect to the bi-crystals, providing compatibility and stress equilibrium at their internal interface. During loading, the bi-crystal boundaries deform dissimilar to the associated grain interior. Arising from this heterogeneity, a geometrically necessary dislocation (GND) density can be computed, which is required to restore compatibility of the crystallographic lattice. This effect provides a physically based method to account for the additional hardening as introduced by the GNDs, the magnitude of which is related to the grain size. Hence, a scale-dependent response is obtained, for which the numerical simulations predict a mechanical behaviour corresponding to the Hall–Petch effect. Compared to a full-scale finite element Model reported in the literature, the present polycrystalline crystal Plasticity Model is of equal quality yet much more efficient from a computational point of view for simulating uniaxial tension experiments with various grain sizes.
Giang D Nguyen - One of the best experts on this subject based on the ideXlab platform.
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failure analysis of a cold rolled steel tensile specimen using a damage Plasticity Model
2017Co-Authors: Bac V Mai, Giang D Nguyen, Cao Hung Pham, Gregory J HancockAbstract:This paper presents preliminary results on the formulation of a damage-Plasticity Model and its applications for the failure analysis of cold-rolled high strength steels. The Model is based on von Mises plastic theory combined with a damage criterion to capture both hardening and softening responses. The proposed constitutive Model is calibrated against available experimental data and implemented into the ABAQUS finite element (FE) package for the failure analysis in a tensile test of cold-formed steel (CFS). Both the experimental overall response of the member and its fracture pattern can be predicted, showing the potentials of the Model in structural applications. In addition, both advantages and disadvantages of the Model are discussed with proposals for further improvements.
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a nonlocal coupled damage Plasticity Model for the analysis of ductile failure
2015Co-Authors: Giang D Nguyen, Alexander M Korsunsky, Jonathan P BelnoueAbstract:This paper presents a nonlocal coupled damage-Plasticity Model for the analysis of ductile fracture. The proposed Model makes use of both damage mechanics and Plasticity theories and hence is able to capture the pre-peak hardening and post-peak softening responses as well as the stiffness reduction of the material during the deformation and fracture processes. Nonlocal regularisation technique is used as an enhancement to the proposed damage-Plasticity Model to deal with softening related problems in the constitutive Modelling and the failure analysis. Emphasis is put on the determination of Model parameters with a novel calibration procedure, based on the experimental technique (Korsunsky and Kim, 2005) on the measurement of essential and non-essential works of fracture, proposed and effectively used for the Model calibration. It is shown that all Model parameters can be properly calibrated based on the proposed method, and experimental results, making the Model attractive for practical applications. The proposed nonlocal Model enables the stress update to be carried out pointwise, and hence facilitates the implementation of the Model in existing finite element codes. Numerical examples are used to demonstrate the capability of the proposed Model.