| 1. |
- Adams, Camiel, 1992, et al.
(författare)
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Efficient modelling of delamination growth using adaptive isogeometric continuum shell elements
- 2020
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 65:1, s. 99-117
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Tidskriftsartikel (refereegranskat)abstract
- The computational efficiency of CAE tools for analysing failure progression in large layered composites is key. In particular, efficient approximation and solution methods for delamination modelling are crucial to meet today’s requirements on virtual development lead times. For that purpose, we present here an adaptive continuum shell element based on the isogeometric analysis framework, suitable for the modelling of arbitrary delamination growth. To achieve an efficient procedure, we utilise that, in isogeometric analysis, the continuity of the approximation field easily can be adapted via so-called knot insertion. As a result, the current continuum shell provides a basis for an accurate but also computationally efficient prediction of delamination growth in laminated composites. Results show that the adaptive modelling framework works well and that, in comparison to a fully resolved model, the adaptive approach gives significant time savings even for simple analyses where major parts of the domain exhibit delamination growth.
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| 2. |
- Amirian, Benhour, et al.
(författare)
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Phase-field approach to evolution and interaction of twins in single crystal magnesium
- 2022
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Ingår i: Computational Mechanics. - : Springer Nature. - 0178-7675 .- 1432-0924. ; 70:4, s. 803-818
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Tidskriftsartikel (refereegranskat)abstract
- Crack initiation and propagation as well as abrupt occurrence of twinning are challenging fracture problems where the transient phase-field approach is proven to be useful. Early-stage twinning growth and interactions are in focus herein for a magnesium single crystal at the nanometer length-scale. We demonstrate a basic methodology in order to determine the mobility parameter that steers the kinetics of phase-field propagation. The concept is to use already existing molecular dynamics simulations and analytical solutions in order to set the mobility parameter correctly. In this way, we exercise the model for gaining new insights into growth of twin morphologies, temporally-evolving spatial distribution of the shear stress field in the vicinity of the nanotwin, multi-twin, and twin-defect interactions. Overall, this research addresses gaps in our fundamental understanding of twin growth, while providing motivation for future discoveries in twin evolution and their effect on next-generation material performance and design.
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| 3. |
- Bargmann, Swantje, 1980, et al.
(författare)
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An extended crystal plasticity model for latent hardening in polycrystals
- 2011
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 48:6, s. 631-645
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Tidskriftsartikel (refereegranskat)abstract
- In this contribution, a computational approach to modeling size-dependent self- and latent hardening in polycrystals is presented. Latent hardening is the hardening of inactive slip systems due to active slip systems. We focus attention on the investigation of glide system interaction, latent hardening and excess dislocation development. In particular, latent hardening results in a transition to patchy slip as a first indication and expression of the development of dislocation microstructures. To this end, following Nye (Acta Metall 1:153-162, 1953), Kondo (in Proceedings of the second Japan national congress for applied mechanics. Science Council of Japan, Tokyo, pp. 41-47, 1953), and many others, local deformation incompatibility in the material is adopted as a measure of the density of geometrically necessary dislocations. Their development results in additional energy being stored in the material, leading to additional kinematic-like hardening effects. A large-deformation model for latent hardening is introduced. This approach is based on direct exploitation of the dissipation principle to derive all field relations and (sufficient) forms of the constitutive relations as based on the free energy density and dissipation potential. The numerical implementation is done via a dual-mixed finite element method. A numerical example for polycrystals is presented.
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| 4. |
- Berthelsen, Rolf, et al.
(författare)
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Computational homogenisation for thermoviscoplasticity : application to thermally sprayed coatings
- 2017
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 0178-7675 .- 1432-0924. ; 60:5, s. 739-766
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Tidskriftsartikel (refereegranskat)abstract
- Metal forming processes require wear-resistant tool surfaces in order to ensure a long life cycle of the expensive tools together with a constant high quality of the produced components. Thermal spraying is a relatively widely applied coating technique for the deposit of wear protection coatings. During these coating processes, heterogeneous coatings are deployed at high temperatures followed by quenching where residual stresses occur which strongly influence the performance of the coated tools. The objective of this article is to discuss and apply a thermo-mechanically coupled simulation framework which captures the heterogeneity of the deposited coating material. Therefore, a two-scale finite element framework for the solution of nonlinear thermo-mechanically coupled problems is elaborated and applied to the simulation of thermoviscoplastic material behaviour including nonlinear thermal softening in a geometrically linearised setting. The finite element framework and material model is demonstrated by means of numerical examples.
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| 5. |
- Bharali, Ritukesh, 1991, et al.
(författare)
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A micromorphic phase-field model for brittle and quasi-brittle fracture
- 2024
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Ingår i: Computational Mechanics. - 1432-0924 .- 0178-7675. ; 73:3, s. 579-598
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Tidskriftsartikel (refereegranskat)abstract
- In this manuscript, a robust and variationally consistent technique is proposed for local treatment of the phase-field fracture irreversibility. This technique involves an extension of the phase-field fracture energy functional through a micromorphic approach. Consequently, the phase-field is transformed into a local variable, while a micromorphic variable regularizes the problem. The local nature of the phase-field variable enables an easier implementation of its irreversibility using a pointwise 'max' with system level precision. Unlike the popular history variable approach, which also enforces local fracture irreversibility, the micromorphic approach yields a variationally consistent framework. The efficacy of the micromorphic approach in phase-field fracture modelling is demonstrated in this work with numerical experiments on benchmark brittle and quasi-brittle fracture problems in linear elastic media. Furthermore, the extensibility of the micromorphic phase-field fracture model toward smultiphysics problems is demonstrated. To that end, a theoretical extension is carried out for modelling hydraulic fracture, and relevant numerical experiments exhibiting crack merging are presented. The source code as well as the data set accompanying this work would be made available on GitHub (https://github.com/ritukeshbharali/ falcon).
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| 6. |
- Bonnaud, Etienne L., et al.
(författare)
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Explicit, fully implicit and forward gradient numerical integration of a hyperelasto-viscoplastic constitutive model for amorphous polymers undergoing finite deformation
- 2019
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Ingår i: Computational Mechanics. - : Springer. - 0178-7675 .- 1432-0924. ; 64:5, s. 1389-1401
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Tidskriftsartikel (refereegranskat)abstract
- Following the growing use of amorphous polymers in an expanding range of applications, interest for numerical modeling of polymer behavior has greatly increased. Together with reliable constitutive models, stable, accurate and rapid integration algorithms valid for large deformations need to be developed. Here, in the framework of hyperelasto-viscoplasticity and multiplicative split formulation, three integration algorithms (explicit, fully implicit and forward gradient) are generated for a constitutive polymer model and respective stability is investigated. The algorithms are furthermore implemented in a commercial Finite Element code and simulation of a full field tensile test is shown to capture the actual deformation behavior of polymers.
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| 7. |
- Brouzoulis, Jim, 1984, et al.
(författare)
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Strategies for planar crack propagation based on the concept of material forces
- 2011
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 47:3, s. 295-304
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a computational framework for the simulation of planar crack growth (including kinking) driven by "material forces". An evolution law for the crack tip position is formulated, which is shown to give rise to different propagation strategies when subjected to certain assumptions on regularity. Three such strategies, that previously have been proposed in the literature in principle: Explicit Proportional Extension (EPE), Implicit Proportional Extension (IPE) and Maximum Parallel Release Rate (MPRR), are outlined and assessed. Based on the results of two numerical examples, it is concluded that the presented propagation strategies produce almost identical results and are robust with respect to time discretization.
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| 8. |
- Börjesson, Elias, 1992, et al.
(författare)
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A generalised path-following solver for robust analysis of material failure
- 2022
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 70:2, s. 437-450
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Tidskriftsartikel (refereegranskat)abstract
- When analysing complex structures with advanced damage or material models, it is important to use a robust solution method in order to trace the full equilibrium path. In light of this, we propose a new path-following solver based on the integral of the rate of dissipation in each material point, for solving problems exhibiting large energy dissipating mechanisms. The method is a generalisation and unification of previously proposed dissipation based path-following solvers, and makes it possible to describe a wider range of dissipation mechanisms, such as large strain plasticity. Furthermore, the proposed method makes it possible to, in a straightforward way, combine the effects from multiple dissipation mechanisms in a simulation. The capabilities of the solver are demonstrated on four numerical examples, from which it can be concluded that the proposed method is both versatile and robust, and can be used in different research domains within computational structural mechanics and material science.
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| 9. |
- Cannmo, Patrik, et al.
(författare)
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Modelling of interfacial viscoplastic slip coupled to damage in a polycrystalline microstructure
- 1997
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Ingår i: Computational Mechanics. - 0178-7675 .- 1432-0924. ; 20:1-2, s. 12-19
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Tidskriftsartikel (refereegranskat)abstract
- The mesomechanics behavior of a polycrystalline microstructure subjected to creep and constant strain rate loadings is investigated. The analysis is based on a Voronoi polygonization strategy for the generation of grains, that are bonded to each other via interfaces along the grain boundaries. A new constitutive model is proposed for the rate-dependent debonding along these interfaces, whereby damage is kinetically coupled to viscoplastic slip and dilatation. The paper may be viewed as generalizing the rate-independent model used in Cannmo et al. (1995).
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| 10. |
- Carlsson, Kristoffer, 1989, et al.
(författare)
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A comparison of the primal and semi-dual variational formats of gradient-extended crystal inelasticity
- 2017
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 60:4, s. 531-548
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we discuss issues related to the theoretical as well as the computational format of gradient-extended crystal viscoplasticity. The so-called primal format uses the displacements, the slip of each slip system and the dissipative stresses as the primary unknown fields. An alternative format is coined the semi-dual format, which in addition includes energetic microstresses among the primary unknown fields. We compare the primal and semi-dual variational formats in terms of advantages and disadvantages from modeling as well as numerical viewpoints. Finally, we perform a series of representative numerical tests to investigate the rate of convergence with finite element mesh refinement. In particular, it is shown that the commonly adopted microhard boundary condition poses a challenge in the special case that the slip direction is parallel to a grain boundary.
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