Jozef Bocko

On hybrid stress, hybrid strain and enhanced strain finite element formulations for a geometrically exact shell theory with drilling degrees of freedom

The paper is concerned with the finite element formulation of a recently proposed geometrically exact shell theory with natural inclusion of drilling degrees of freedom. Stress hybrid finite elements are contrasted by strain hybrid elements as well as enhanced strain elements. Numerical investigations and comparison is carried out for a four-node element as well as a nine-node one. As far as the four-node element is concerned it is shown that the stress hybrid element and the enhanced strain one are equivalent. The hybrid strain formulation corresponds to the hybrid stress formulation only in shear dominated problems, that is the case of the plate.

Algorithm for determining static characteristic on electromagnetic actuator for rectilinear locomotion structure of a snake-like robot

This work deals with the determination of static characteristics of electromagnetic actuator. Electromagnetic actuator is designed as drive for rectilinear locomotion structure parts of snake-like robot. Static characteristics are determined by the solving of a non-linear problem of the actuators magnetic circuit in a ferromagnetic cores particular positions and at the different fluxional rates of the coil. Static characteristics are represented by a L induction, magnetic force affecting ferromagnetic core Fm. For the calculation of the coil induction L is used the power of magnetic field. Magnetic field power is calculated by using Maxwell stress tensor and differential formula by a numeric derivation way.

Methods for Verification of Safety of the Sluice Gates in Water Power Plants

Methods for Verification of Safety of the Sluice Gates in Water Power Plants The aim of a paper is to show theoretical and experimental methods that are used in the process of evaluation of safe operation of sluice gates in water power plants. On several examples are represented various treatments that allow to provide identification of locations of possible failures on carrying elements of sluice gates.

Hyperplastic Material Models and their Applications in Engineering

In this paper concepts and behaviour of plasticity, hyperelasticity and hyperplasticity are explained and clarified. Description of hardening models and hyperplastic models is provided too. The theoretical overview presented in this paper covers the crucial prerequisite for creating and applying hyperplastic material models into practice, either for simulation purposes or for real world application.

The Use of Nonlocal Theory for Bending Vibrations of Single-Walled Carbon Nanotubes

In the paper are investigated the eigenfrequencies of single-walled carbon nanotubes (SWCNTs) by the analytical method based on nonlocal theory of beam bending. A continuum approach is applied for eigenfrequency computation of SWCNTs with four types of beam end conditions: clamped-free (C-F), simply-simply supported (S-S), clamped-simply supported (C-S) and clamped-clamped (C-C).

Buckling Analysis of Hetero-Junction Carbon Nanotubes

Abstract The buckling analysis of carbon nanotubes without and with hetero-junctions is described in this paper. The buckling behaviour was investigated by the finite element method and the carbon nanotubes were modelled as space frame structures. The results showed that the critical buckling force depends on the dimensions of carbon nanotubes. The critical buckling forces of hetero-junction carbon nanotubes are in range between critical buckling forces of carbon nanotubes of both used diameters with the same chiralities without hetero-junction.

Granulation Process of the Organic Suspension: Fluidized Bed Temperature Influence on the Kinetics of the Granule Formation

The authors of the article present and prove the possibility of reducing the economic and environmental indicators in the processes of mineral fertilizers granulation by means of recycling and using organic agricultural waste. It is shown that such waste products are in the form of very moist suspensions, therefore, in order to minimize energy consumption for their processing, the optimal technology for granular product preparation is granulation in the fluidized bed apparatus. For this purpose there has been conducted the physical modelling of the granule formation process and one found out the conditions of suspended layer formation, which determine the nature of the dispersed suspension and dispersed solid phase interaction. One has experimentally established the temperature regimes of organic suspensions granulation and determined the operating parameters of the process. The kinetics of coarsening of granules was studied depending on the temperature of dehydration of organic suspensions. Analytical dependencies that are determined by the heat transfer coefficient are obtained to determine the time and temperature of granule heating.

Selection of a Significant Numerical Model of Plasticity for the Purpose of Numerical Analysis of Plastic Reinforcement

The paper is focused on the process of selecting a suitable material plasticity model. Such a model would be used in the future numerical analysis of the behaviour of selected structural elements in the elastic-plastic deformation of the steel in the SolidWorks software environment. These analyzes should include monitoring the behaviour of the material under the conditions of its plastic reinforcement (strain - hardening). Numerical modelling used two models of plasticity, namely the von Mises and Trescas models. Subsequently, a comparison of the match between the real load-deformation diagram, possibly stress-strain diagram, obtained by the experimental static tensile test and the diagram obtained from the numerical simulation of two different steel-based structural materials was performed. The results of the dual tensile test analysis showed that the von Mises model achieves greater consistency with the tensile curve based the actual tensile test. Therefore, this model will be later used in subsequent numerical simulations of the material under the conditions of its plastic reinforcement.

Stability Loss of Axisymmetric Cylindrical Shell under Axial Pressure Load

The paper deals with geometric imperfections, which are defined as the deviation of the mid-surface of the shell. A parametric model of the axially symmetrical shell was created which was loaded with axial compressive load. The task was to determine the decrease in critical force causing loss of stability. The finite element method was used in order to find solution.

Application of finite element method for analysis of nanostructures

Abstract The paper deals with application of the finite element method in modelling and simulation of nanostructures. The finite element model is based on beam elements with stiffness properties gained from the quantum mechanics and nonlinear spring elements with force-displacement relation are gained from Morse potential. Several basic mechanical properties of structures are computed by homogenization of nanostructure, e.g. Youngs modulus, Poissons ratio. The problems connecting with geometrical parameters of nanostructures are considered and their influences to resulting homogenized quantities are mentioned.