| 1. |
- Stukowski, A., et al.
(författare)
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Atomicrex-a general purpose tool for the construction of atomic interaction models
- 2017
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - 1361-651X .- 0965-0393. ; 25:5, s. Article Number: 055003 -
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Tidskriftsartikel (refereegranskat)abstract
- We introduce ATOMICREX, an open-source code for constructing interatomic potentials as well as more general types of atomic-scale models. Such effective models are required to simulate extended materials structures comprising many thousands of atoms or more, because electronic structure methods become computationally too expensive at this scale. ATOMICREX covers a wide range of interatomic potential types and fulfills many needs in atomistic model development. As inputs, it supports experimental property values as well as ab initio energies and forces, to which models can be fitted using various optimization algorithms. The open architecture of ATOMICREX allows it to be used in custom model development scenarios beyond classical interatomic potentials while thanks to its Python interface it can be readily integrated e.g., with electronic structure calculations or machine learning algorithms. ELL GC, 1985, PHYSICAL REVIEW B, V31, P6184
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| 2. |
- Mackerle, Jaroslav
(författare)
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Smart materials and structures - a finite element approach - an addendum : a bibliography (1997-2002) (vol 6, pg 293, 1998)
- 2003
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 11:5, s. 707-744
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis and simulation of smart materials and structures. The bibliography is an addendum to the Smart materials and structures-a finite-element approach: a bibliography (1986-1997) published in 1998 Modelling Simul. Mater. Sci. Eng. 6 293-334. The added bibliography at the end of this article contains 977 references to papers and conference proceedings on the subject that were published in 1997-2002. The following topics are included: smart materials, smart components/structures, smart sensors and actuators, and controlled structures technology.
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| 3. |
- Hallberg, Håkan
(författare)
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A modified level set approach to 2D modeling of dynamic recrystallization
- 2013
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 21:8
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Tidskriftsartikel (refereegranskat)abstract
- The macroscopic properties of metallic materials depend on the state of the grain microstructure. Recrystallization acts as one of the most important mechanisms in the evolution of the microstructure and hence also of the macroscopic properties. This paper presents a mesoscale model of microstructure evolution due to recrystallization, based on a level set formulation employed in a finite element setting. The use of level sets to represent grains and grain boundaries in polycrystal microstructures is a relatively recent development in computational materials science and the present contribution suggests new methodologies such as interface reconstruction, allowing for example boundary conditions to be prescribed along grain boundary interfaces and distinct localization and representation of grain boundary junctions. Polycrystal plasticity is modeled by considering the evolution of dislocation density in the individual crystals. The influence of grain boundaries on dislocation accumulation is captured in the model, causing the formation of dislocation density gradients within the grains. The model is used in simulations of dynamic recrystallization, taking pure copper as example material. It is shown that the proposed model captures the salient features of dynamic recrystallization during thermomechanical materials processing.
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| 4. |
- Hallberg, Håkan
(författare)
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Influence of anisotropic grain boundary properties on the evolution of grain boundary character distribution during grain growth - a 2D level set study
- 2014
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 22:8
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Tidskriftsartikel (refereegranskat)abstract
- The present study elaborates on a 2D level set model of polycrystal microstructures that was recently established by adding the influence of anisotropic grain boundary energy and mobility on microstructure evolution. The new model is used to trace the evolution of grain boundary character distribution during grain growth. The employed level set formulation conveniently allows the grain boundary characteristics to be quantified in terms of coincidence site lattice (CSL) type per unit of grain boundary length, providing a measure of the distribution of such boundaries. In the model, both the mobility and energy of the grain boundaries are allowed to vary with misorientation. In addition, the influence of initial polycrystal texture is studied by comparing results obtained from a polycrystal with random initial texture against results from a polycrystal that initially has a cube texture. It is shown that the proposed level set formulation can readily incorporate anisotropic grain boundary properties and the simulation results further show that anisotropic grain boundary properties only have a minor influence on the evolution of CSL boundary distribution during grain growth. As anisotropic boundary properties are considered, the most prominent changes in the CSL distributions are an increase of general low-angle Σ1 boundaries as well as a more stable presence of Σ3 boundaries. The observations also hold for the case of an initially cube-textured polycrystal. The presence of this kind of texture has little influence over the evolution of the CSL distribution. Taking into consideration the anisotropy of grain boundary properties, grain growth alone does not seem to be sufficient to promote any significantly increased overall presence of CSL boundaries.
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| 5. |
- Mellbin, Ylva, et al.
(författare)
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A combined crystal plasticity and graph-based vertex model of dynamic recrystallization at large deformations
- 2015
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- A mesoscale model of microstructure evolution is formulated in the present work by combining a crystal plasticity model with a graph-based vertex algorithm. This provides a versatile formulation capable of capturing finite-strain deformations, development of texture and microstructure evolution through recrystallization. The crystal plasticity model is employed in a finite element setting and allows tracing of stored energy build-up in the polycrystal microstructure and concurrent reorientation of the crystal lattices in the grains. This influences the progression of recrystallization as nucleation occurs at sites with sufficient stored energy and since the grain boundary mobility and energy is allowed to vary with crystallographic misorientation across the boundaries. The proposed graph-based vertex model describes the topological changes to the grain microstructure and keeps track of the grain inter-connectivity. Through homogenization, the macroscopic material response is also obtained. By the proposed modeling approach, grain structure evolution at large deformations as well as texture development are captured. This is in contrast to most other models of recrystallization which are usually limited by assumptions of one or the other of these factors. In simulation examples, the model is in the present study shown to capture the salient features of dynamic recrystallization, including the effects of varying initial grain size and strain rate on the transitions between single-peak and multiple-peak oscillating flow stress behavior. Also the development of recrystallization texture and the influence of different assumptions on orientation of recrystallization nuclei are investigated. Further, recrystallization kinetics are discussed and compared to classical JMAK theory. To promote computational efficiency, the polycrystal plasticity algorithm is parallelized through a GPU implementation that was recently proposed by the authors.
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| 6. |
- Mellbin, Y., et al.
(författare)
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Recrystallization and texture evolution during hot rolling of copper, studied by a multiscale model combining crystal plasticity and vertex models
- 2016
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 24:7
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Tidskriftsartikel (refereegranskat)abstract
- A multiscale modeling framework, combining a graph-based vertex model of microstructure evolution with a GPU-parallelized crystal plasticity model, was recently proposed by the authors. Considering hot rolling of copper, the full capabilities of the model are demonstrated in the present work. The polycrystal plasticity model captures the plastic response and the texture evolution during materials processing while the vertex model provides central features of grain structure evolution through dynamic recrystallization, such as nucleation and growth of individual crystals. The multiscale model makes it possible to obtain information regarding grain size and texture development throughout the workpiece, capturing the effects of recrystallization and heterogeneous microstructure evolution. Recognizing that recrystallization is a highly temperature dependent phenomenon, simulations are performed at different process temperatures. The results show that the proposed modeling framework is capable of simultaneously capturing central aspects of material behavior at both the meso- and macrolevel. Detailed investigation of the evolution of texture, grain size distribution and plastic deformation during the different processing conditions are performed, using the proposed model. The results show a strong texture development, but almost no recrystallization, for the lower of the investigated temperatures, while at higher temperatures an increased recrystallization is shown to weaken the development of a typical rolling texture. The simulations also show the influence of the shear deformation close to the rolling surface on both texture development and recrystallization.
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| 7. |
- Zijlstra, Eeuwe S., et al.
(författare)
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Optimized Gaussian basis sets for Goedecker-Teter-Hutter pseudopotentials
- 2009
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 17:1
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Tidskriftsartikel (refereegranskat)abstract
- We have optimized the exponents of Gaussian s and p basis functions for the elements H, B-F and Al-Cl using the pseudopotentials of (Goedecker, Teter and Hutter 1996 Phys. Rev. B 54 1703) by minimizing the total energy of dimers. We found that this procedure causes the Gaussians to be somewhat more localized than the usual procedure, where the exponents are optimized for atoms. We further found that three exponents, equal for s and p orbitals, are sufficient to reasonably describe the electronic structure of all elements that we have studied. For Li and Be results are presented for pseudopotentials of (Hartwigsen et al 1998 Phys. Rev. B 58 3641). We expect that our exponents will be useful for density functional theory studies where speed is important.
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| 8. |
- jsessionid=18B0653575ADA5FE168BC397D2678FC8.c3.iopscience.cld.iop.org, Pär, et al.
(författare)
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Mathematical models of transport phenomena associated with arc-welding processes: A survey
- 1994
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 2:5, s. 995-1016
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Tidskriftsartikel (refereegranskat)abstract
- A comprehensive survey is presented of research on transport phenomena, that is, heat flow, fluid flow, mass transfer, and electrodynamics, associated with arc welding. Both gas-metal arc-welding (GMAW) and gas-tungsten arc welding (GTAW) systems are considered, and appropriate emphasis is placed on the intrinsic differences between these systems. The topics discussed include the behaviour of the arc, and its interaction with both the electrode and the surrounding medium, on the one hand, and the behaviour of the weld pool on the other. The limited work done on the coupling between arcs, electrodes, and weld pools is also discussed, as are some process-control issues, but the problems of thermal stress evolution and stress-induced deformation in the solid state are not treated. A critical discussion of the comparison between model predictions and experimental measurements is a key feature of the presentation, which concludes with a discussion of the critical problems that still need to be addressed.
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| 9. |
- Nilsson, Annika, et al.
(författare)
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Process development of aluminium ironing using finite element analysis
- 1999
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 7:6, s. 1005-1011
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the use of finite-element simulation of an aluminum ironing process is presented. In this process friction, clearance distance between punch and die and punch radius must all be taken into consideration when designing products and processes. In practice, it is difficult to analyze individual parameters separately, but with computer simulation it is easy to see the effects of changing one specific parameter on the outcome of the process. This work has demonstrated the use of computational support in product development to gain an understanding of the effects of process and geometric parameters. The most important results were confirmation of the sensitivity of the process to clearance distance between punch and die and, also, frictional conditions, as well as the relative insensitivity of the process to change in punch nose radius
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| 10. |
- Hossain, Shakhawath, et al.
(författare)
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Uniaxial Compression of Three-Dimensional Entangled Fibre Networks: Impacts of Contact Interactions
- 2019
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Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 27:1
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns uniaxial compression of anisotropic fibre network, as typically seen in the end use of nonwoven and textile fibre assemblies. The constitutive relationship and deformation mechanism have been investigated by using a bead-model to represent the complex structures of the constituent fibres and the fibre networks. The compression stress shows a power-law dependency on the density with a threshold density for both experimental and numerical fibre networks. Unlike the widely studied tri-axial compression of the initially isotropic network, it was found that the contact interaction between the fibres, especially the fibre-fibre contact stiffness (or the transverse compression properties of fibres), has a large impact on all the constitutive parameters. In particular, the exponent values computed based on the softer contact stiffnesses agreed very well with the experimental values reported in the literature. The internal deformation mechanism was similar to the earlier studies that at low compression, the deformation is dominated by the low-energy-mode deformations (i.e. bending and shear), whereas at higher compression, the difference appears: the compression of fibre-fibre contacts, instead of the deformation in the fibre axial direction, takes over.
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