Development and validation of detailed 3-D finite element model of human skull used for explicit dynamic simulation of impact conditions is presented in the paper. The FE model is based on the series of computer tomography scans of resolution 512x512 pixels taken in 1mm slices. Fully automated direct generation of the volumetric tetrahedral mesh based on the Marching Cubes Algorithm, Laplacian smoothing and Delaunay tetrahedralisation is used to develop the geometry of both the human skull and the brain.Results obtained using this detailed FE model are compared to experimental results from a standard drop test as well as a simplified version of the skull model based on geometry of a head form used in our experiments. These experiments use a standard metal head form of variable size. Results from both the experimental and numerical modelling will be used to describe possible injury mechanisms and quantify design parameters of protective helmet related to a specific impact event.

This article deals with finite-element (FE) modelling of the reinforcing effect of the geosynthetic material used in the construction of a ballasted track. Various different designs of geosynthetic material are studied and their reinforcing effects are evaluated in terms of the total settlement reduction. Three-dimensional FE models of the reinforced railway superstructure are compared to a reference FE model with no reinforcement. Each geosynthetic material is modelled respecting its material properties, and the interaction with the ballast material is simulated according to its primary function. A clear distinction in the modelling of the interaction with the ballast material is made between geogrids and the remaining geosynthetics. A new approach to model the reinforcing effect of a geogrid is proposed and evaluated by FE analysis. The results of numerical modelling are compared to those of experiments conducted using an experimental box instrumented with one half of an instrumented concrete sleeper. Different types of geosynthetics were used to reinforce the ballast material, and the settlement reduction was measured using linear variable differential transformer (LVDT) sensors. The proposed FE models enable quick evaluation of the reinforcing effect of a given geosynthetic and comparison to other possible solutions in terms of the total settlement reduction. Other design possibilities (e.g. the use of reinforcing geosynthetics in several layers) are briefly discussed, too.

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Abstract. A comparative analysis using the programme ANSYS (FEM) deals with the generation of the computation model and with the assessment of the influence of the geogrids and the vertical lime-cement columns on the bearing capacity and deformation of the railway embankment on the less load-bearing subsoil. The graphic outputs give an overview of the field layout of equivalent stresses and deformation in the construction of the railway substructure.

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