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- Cloots, Rudy J.H., et al.
(författare)
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Multi-scale mechanics of traumatic brain injury : predicting axonal strains from head loads
- 2013
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Ingår i: Biomechanics and Modeling in Mechanobiology. - : Springer Science and Business Media LLC. - 1617-7959 .- 1617-7940. ; 12:1, s. 137-150
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Tidskriftsartikel (refereegranskat)abstract
- The length scales involved in the development of diffuse axonal injury typically range from the head level (i.e., mechanical loading) to the cellular level. The parts of the brain that are vulnerable to this type of injury are mainly the brainstem and the corpus callosum, which are regions with highly anisotropically oriented axons. Within these parts, discrete axonal injuries occur mainly where the axons have to deviate from their main course due to the presence of an inclusion. The aim of this study is to predict axonal strains as a result of a mechanical load at the macroscopic head level. For this, a multi-scale finite element approach is adopted, in which a macro-level head model and a micro-level critical volume element are coupled. The results show that the axonal strains cannot be trivially correlated to the tissue strain without taking into account the axonal orientations, which indicates that the heterogeneities at the cellular level play an important role in brain injury and reliable predictions thereof. In addition to the multi-scale approach, it is shown that a novel anisotropic equivalent strain measure can be used to assess these micro-scale effects from head-level simulations only.
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| 2. |
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| 3. |
- Mirkhalaf, Mohsen, 1982, et al.
(författare)
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Micro-mechanical modelling of anisotropic behaviour of oriented semi-crystalline polymers
- 2019
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Ingår i: Journal of Polymer Science, Part B: Polymer Physics. - 1099-0488 .- 0887-6266.
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Tidskriftsartikel (refereegranskat)abstract
- Some manufacturing processes of polymeric materials, such as injection moulding or film blowing, cause the final product to be highly anisotropic. In this study, the mechanical behaviour of drawn Polyethylene (PE) tapes is investigated via micro-mechanical modelling. An elastoviscoplastic micro-mechanical model, developed within the framework of the so-called composite inclusion model, is presented to capture the anisotropic behaviour of oriented semi-crystalline Polyethylene. Two different phases namely, amorphous and crystalline (both described by elasto-viscoplastic constitutive models), are considered at the micro-structural level. The initial oriented crystallographic structure of the drawn tapes is taken into account. It was previously shown that by only considering the oriented crystallographic structure, it is not possible to capture the macroscopic anisotropic behaviour of drawn tapes. The main contribution of this study is the development of an anisotropic model for the amorphous phase within the micro-mechanical framework. An EGP (Eindhoven Glassy Polymer) based model including different sources of anisotropy namely, anisotropic elasticity, internal stress in the elastic network and anisotropic viscoplasticity, is developed for the amorphous phase and incorporated into the micro-mechanical model. Comparisons against experimental results reveal remarkable improvements of the model predictions (compared to micro-mechanical model predictions including isotropic amorphous domains) and thus the signicance of the amorphous phase anisotropy on the overall behavior of drawn PE tapes.
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| 4. |
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| 5. |
- van Dommelen, JAW, et al.
(författare)
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Mechanics of Traumatic Brain Injury at Multiple Length Scales
- 2010
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Ingår i: Proceedings of the 16th US National Congress on Theoretical and Applied Mechanics, State College.
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Konferensbidrag (refereegranskat)abstract
- Current numerical head models predict the response of the brain based on a geometrically homogeneous anatomical structure. However, these models often lack the detailed anatomy of the heterogeneous structures within the head and an accurate description of the constitutive response of the brain tissue. A nonlinear constitutive model for brain tissue has been developed and validated. The consequences of meso-level heterogeneities in the brain for the development of traumatic brain injury have been investigated, as well as the orientationdependent sensitivity of brain tissue to mechanical loads based on a cellular injury mechanism.
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