Search

Porosity and permeability are related properties of solids that are investigated by different continuum models. Porosity has already been explained by the author as the variation of the strain energy density of a dry solid using the rheological-dynamical analogy (RDA). Permeability is traditionally, theoretically and experimentally, investigated by Darcy's law and as such depends on the properties of the fluid, water or gas flowing through the solid. This means that we do not have a defined permeability of solid matter, which is independent of the properties of water or gas. In this paper, intrinsic permeability is defined based on the rheological dynamics theory (RDT) in the state of critical damping. Furthermore, RDT defines the liquid flow criterion by the porosity threshold of the solid. Permeability defined in this way is confirmed by experimental data from the literature on the example of engineered permeable concrete.

This paper is concerned with experimental verification of inelastic buckling and failure analysis of concrete panels according to rheological dynamical theory (RDT). Iterative modulus calculation of buckling stress is presented and verified for concrete panels under biaxial and axial compression. For biaxial compression, three different concrete mixtures with two stress ratios are considered. Some experimental results from literature are also used to verify RDT calculation for concrete panels under axial compression as well as analytical expressions for concrete wall panel in two-way action. Besides normal concrete strength, this calculation can be used for fibre-reinforced ultra-high performance concrete UHPC. The calculation according to RDT had shown that the values of material parameters of such modulus of elasticity and Poisson's ratio have a significant influence on the structural material constant as well as buckling stress results. The calculation of buckling stress which is necessary for RDT calculation was carried out using the corresponding model in Abaqus software.

This paper presents a theoretical investigation of elastic and inelastic buckling of thin-walled beam with initial imperfections. The main aim of this paper is to show that the fracture of beams varies from brittle to extremely ductile depending on the imperfections. Elastic solution for estimation of initial imperfections against the limit load capacity in the elastic range is well known. However, the elastic solution can be applied only to the line of limit load capacity. Examination of the limit load capacity of structure is very complicate problem of material non-linearity, because this problem must includes the plastic mechanism of failure. In this paper the limit load capacity of beam is analyzed using the reological-dynamical analogy (RDA) [4]. In order to demonstrate the ability of RDA, the comparison with experimental and numerical results of one steel beam from Ref [1] by Murray, is done.

Many structural parts are exposed to high temperatures and loading. It is then important to have data about material inelastic behaviour under such exploiting conditions. Influence of temperature on mechanical characteristics of a material may be inserted via the creep coefficient in the range of visco-elasto-plastic (VEP) strains. This damage parameter is implemented in this paper in conjunction with mathematical material modelling approach named rheological-dynamical analogy (RDA) in order to address structural stiffness reduction due to inelastic material behaviour. The aim of this paper is to define structural-material internal damping based on both the RDA dynamic modulus and modal damping ratio, by modelling critically damped dynamic systems in the steady-state response. These systems are credible base for explanation of the phenomenon of thermo-visco-plasticity and creep in structural-material response due to high temperatures and loading. Though elastic buckling information for folded-plate structures is not a direct predictor of capacity or collapse behaviour on its own, both the mode and the load (moment) are important proxies for the actual behaviour. In current design codes, such as AISI S100, New Zealand/Australia, and European Union, the design formulae are calibrated through the calculation of elastic critical buckling loads (or moments) to predict the ultimate strength, thus the ability to calculate the associated elastic buckling loads (or moments) has great importance. Moreover, the buckling mode shapes are commonly employed into non-linear collapse modelling as initial geometric imperfections and thermal performance of folded-plate structures in fire. To examine the buckling behaviour of folded-plate structures, the main numerical solution methods are used such as the finite element method (FEM) and finite strip method (FSM). This paper aims at providing a unified frame for quasi-static inelastic buckling and thermal loading of uniformly compressed folded-plate structures using the FSM.

Paper deals with bifurcation stability of stiffened thin plates using the compound finite strip method. Using this method it is also possible to introduce point supports into plate which allows modeling of columns. Thin plate is obtained by simple addition of column and beam stiffness properties into finite strip via deformation energy. According to bifurcation stability theory, critical load is obtained from the standard eigenvalue problem. This approach allows efficient computation of stiffened plates without the need for additional degrees of freedom. Program code is written in software package Wolfram Mathematica. Verification of the model is done through comparison with the analytical solutions and the one obtained from commercial software packages.

This paper describes a set of software tools which we developed for the calculation of fluid flow through cardiovascular organs. Our tools work with medical data from a CT scanner, but could be used with any other 3D input data. For meshing we used a Tetgen tetrahedral mesh generator, as well as a mesh re-generator that we have developed for conversion of tetrahedral elements into bricks. After adequate meshing we used our PAKF solver for calculation of fluid flow. For human-friendly presentation of results we developed a set of post-processing software tools. With modification of 2D mesh (boundary of cardiovascular organ) it is possible to do virtual surgery, so in a case of an aorta with aneurism, which we had received from University Clinical center in Heidelberg from a multi-slice 64-CT scanner, we removed the aneurism and ran calculations on both geometrical models afterwards. The main idea of this methodology is creating a system that could be used in clinics.

Cardiovascular diseases are common and a special difficulty in their curing is diagnostics. Modern medical instruments can provide data that is much more adequate for computer modeling. Computer simulations of blood flow through the cardiovascular organs give powerful advantages to scientists today. The motivation for this work is raw data that our Center recently received from the University Clinical center in Heidelberg from a multislice CT scanner. In this work raw data from CT scanner was used for creating a 3D model of the aorta. In this process we used Gmsh, TetGen (Hang Si) as well as our own software tools, and the result was the 8-node (brick) mesh on which the calculation was run. The results obtained were very satisfactory so...