| 1. |
- Fagerström, Martin, 1979, et al.
(författare)
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Utilising the eXtended Finite Element Method (XFEM) to model failure of thin-walled structures
- 2013
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Ingår i: Proceedings of Svenska mekanikdagar 2013.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The eXtended Finite Element Method (XFEM), exploring the partition of unity concept in terms of an enriched FE-space in order to represent strong (e.g. discontinuity in the field itself) and/or weak (e.g. discontinuity in the spatial derivative) discontinuities, has been extensively used in the literature ever since it was presented by Belytschko and co-workers in 1999. Interesting applications are mesh independent representation of cracks and crack propagation, holes, inclusions, evolving grain and phase boundaries etc.The current contribution will aim at giving an overview of XFEM and the developments thereof with the application to modelling of crack propagation and failure, focusing on the work performed at the Department of Applied Mechanics at Chalmers. Starting from the basics of XFEM, specifics related to robustness and efficiency, extensions of the XFEM concept and applications to industrial relevant loading conditions and materials will be discussed.Currently, the developments are made within two parallel projects on XFEM representation of crack propagation, from which numerical results will be presented. The first project focuses on ductile failure of thin and large metal structures addressing issues related both to the modelling of the ductile failure process as to robustness and computational efficiency of the structural representation. The second project is devoted to crashworthiness of structural composites with the aim of developing a shell element formulation that can simultaneously handle multiple delaminations (within one shell element) and through-thickness cracking (splitting), both being important mechanisms in the modelling of composite crushing. As a first step, a shell element formulation has been established that is able to represent multiple delaminations. The basic features of this formulation and some preliminary results will be presented.
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| 2. |
- Ander, Mats, 1964, et al.
(författare)
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Constructive alignment in solid mechanics courses by means of project assignments
- 2017
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Ingår i: 6: e Utvecklingskonferensen för Sveriges ingenjörsutbildningar, Chalmers tekniska högskola, 22 -23 november 2017.
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Konferensbidrag (refereegranskat)abstract
- This short text paper describes the procedure of planning and implementing project assignments as a means to constructive align courses in Solid mechanics at the school of Civil enginnering at Chalmers. The courses has now been given twice and we summarize our experiences so far.
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| 3. |
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| 4. |
- Auth, Kim Louisa, 1995, et al.
(författare)
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A fully coupled chemo-mechanical cohesive zone model for oxygen embrittlement of nickel-based superalloys
- 2022
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Ingår i: Journal of the Mechanics and Physics of Solids. - : Elsevier BV. - 0022-5096. ; 164
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Tidskriftsartikel (refereegranskat)abstract
- For nickel-based superalloys subjected to high temperatures and oxygen-rich environments, mechanical loading in combination with oxygen diffusion along grain boundaries leads to an acceleration of crack propagation. To account for these phenomena, a fully coupled thermodynamically consistent chemo-mechanical modeling framework for stress-assisted oxygen embrittlement of grain boundaries in polycrystals is proposed. We formulate an extended cohesive zone model where the grain boundary strength is reduced by the presence of oxygen and the oxygen diffusion is enhanced by tensile mechanical loading. We show that the model can qualitatively predict experimental results such as: reduction of ultimate tensile strength and accelerated crack growth due to dwell time combined with mechanical loading and saturation of crack growth rates for increasing environmental oxygen pressure levels. In addition, numerical simulation results of intergranular crack growth are shown for a 2D polycrystalline structure. An emphasis is put on the difference in cracking behavior after dwelling with or without mechanical loading.
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| 5. |
- Auth, Kim Louisa, 1995, et al.
(författare)
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Modeling of environmentally assisted intergranular crack propagation in polycrystals
- 2023
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Ingår i: International Journal for Numerical Methods in Engineering. - 0029-5981 .- 1097-0207. ; 124:23, s. 5183-5199
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline nickel-based superalloys experience accelerated intergranular crack growth when exposed to dwell times in oxygen-rich environments and a combination of high temperature and tensile mechanical loading. Increasing crack growth rates are observed for increasing amounts of environmental oxygen in a certain oxygen concentration range, while below and above that range crack growth rates remain approximately constant. A fully coupled chemo-mechanical modeling framework accounting for the degradation of grain boundaries by oxygen has been presented by the authors. In this work, we expand the framework by a moving boundary condition to capture a realistic oxygen flux in grain boundary cracks for both edge cracks connected to the environment and interior cracks. In numerical simulation results, the behavior of the moving boundary condition is shown for intergranular crack propagation through a polycrystal subjected to cyclic loading. Finally, the capabilities of the modeling framework to qualitatively predict the dependence of the average crack growth rate on the environmental oxygen content, load level, and dwell time are evaluated and it is shown that predictions qualitatively agree with experimental observations for intergranular fracture.
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| 6. |
- Brouzoulis, Jim, 1984, et al.
(författare)
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A shell element formulation for the simulation of propagating delamination and through-thickness cracks
- 2014
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Ingår i: Proceedings of 16th European Conference on Composite Materials - ECCM16. ; , s. (8p)-
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Konferensbidrag (refereegranskat)abstract
- In this contribution, we propose an enhanced shell element formulation for mesh independent FE simulation of through-thickness and multiple delamination crackp ropagation in orthotropic laminates, cf. Figure 1 for an illustration of the possibilities of using this shell element (multiple delaminations). The ambition is to offer a finite element tool to be used for larger component simulations, without having to resort to explicit resolution of each laminae in the laminated structure by three dimensional solid elements or stacked shell elements. The formulation involves three different types of displacement enrichments to make sure that each delaminated subsection which is also cut by a through thickness crack can be individually represented without (unphysical) kinematical couplings to the surrounding structure in the laminate. So far, the proposed modelling framework has been validated against pure deformation modes, in terms of either multiple delaminations or a through-thickness crack.
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| 7. |
- Brouzoulis, Jim, 1984, et al.
(författare)
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An enriched shell element formulation for efficient modeling of multiple delamination propagation in laminates
- 2015
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Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223. ; 126:August 2015, s. 196-206
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Tidskriftsartikel (refereegranskat)abstract
- In the modeling of progressive damage in fiber reinforced polymers, the kinematical representation of delamination is normally treated in one of two ways. Either efficient or accurate modeling of delamination is considered. In the first case, delamination is disregarded or implicitly included in the material modeling. In the second case, delamination is explicitly modeled at a significant numerical cost where all plies are represented by separate elements in the thickness direction, connected by interlaminar cohesive zone elements. In this paper, we therefore aim to take one step closer to more efficient FE analyses by presenting a modeling concept which supports laminate failure analyses requiring only one shell element through the thickness. With this concept, arbitrary delamination propagation is accounted for only in areas where it is needed. In addition, by using this concept, the model preparation time is reduced. We show that the current shell formulation proposed can be utilized to accurately simulate propagating delamination cracks as well as to accurately describe the kinematics of a laminate containing multiple delaminations through the thickness. Thus, we see significant potential for this modeling concept in analyses in which computationally efficiency is of major importance, such as for large scale crash analyses.
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| 8. |
- Brouzoulis, Jim, 1984, et al.
(författare)
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An enriched shell element formulation for modeling of inter- and intralaminar crack propagation in laminates
- 2016
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Ingår i: Composite Structures. - : Elsevier BV. - 0263-8223. ; 136, s. 616-625
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Tidskriftsartikel (refereegranskat)abstract
- In traditional finite element modeling of progressive failure in laminated fiber reinforced polymers, inter- and intralaminar cracks are normally treated in different ways. Interlaminar cracks are normally described explicitly by building up the laminate using stacked elements (solids or shells) connected by cohesive interface elements. Intralaminar cracks, one the other hand, are more often accounted for by using a continuum damage approach, (e.g. a smeared crack approach). In this paper, we propose a modeling concept which instead can accurately represent both intralaminar and interlaminar cracks with an extended kinematical representation, whereby cracks can be explicitly accounted for without excessive use of degrees of freedom. With this concept, we aim to take one step closer to more efficient FE analyses of progressive laminate failure, since only one shell element through the thickness is required, and where arbitrary inter- and intralaminar crack propagation are accounted for only in areas where it is needed. We show that the current shell formulation proposed can be utilized to describe the kinematics of a laminate containing multiple inter- and intralaminar cracks. Thus, we see significant potential for this modeling concept in analyses in which computational efficiency is of major importance.
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