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Computational Homogenization of Cement-Based Porous Piezoelectric Composites with Random Structure

Abstract

The finite element method (FEM) is used to characterize the effective thermo-electromechanical material properties of cement-based piezoelectric ceramic composites in this paper. The micromechanics representative volume element (RVE) approach is used with distribution of piezoelectric particles in the porous cement matrix. The effects of the piezoelectric particle volume fraction and pore volume fraction on the effective composite properties are determined using sets of different boundary conditions. Microscale homogenization is carried out through the analysis of particles which are randomly distributed in a homogenized matrix.

Open access
Estimation of Material Properties of Carbon Nanotubes Using Finite Element Method

Abstract

The paper deals with estimation of material properties of single-walled carbon nanotubes (SWCNTs). The SWCNTs are simulated as frames, where carbon atoms are replaced by nodes and interatomic interactions are replaced by beams. The tension and torsion loading is applied on SWCNTs for determining the elastic modulus, Poisson’s ratio, shear modulus and membrane stiffness of SWCNTs. The simulations for obtaining elongations and torsion angles of SWCNTs are accomplished by the finite element method.

Open access
Evaluation of Performance Indicator of Railway Bridges Using Updated Finite Element Model

Abstract

Structural health monitoring (SHM) can provide information needed to make important decisions regarding the maintenance of bridge structures. However, the data collected from monitoring needs to be first translated into actionable, quantitative or qualitative based characteristics, that indicate the condition of a bridge. This paper presents a process of evaluation of such performance indicator in case of a steel railway bridge using the updated FE model and in-situ measurements of strains on selected stringers and floorbeams.

Open access
Extension of the FGM Beam Finite Element by Warping Torsion

Abstract

In the contribution, our 3D FGM Timoshenko beam finite element with 12x12 stiffness and mass matrices for doubly symmetric open and closed cross-section [1] is extended by warping torsion effect (non-uniform torsion) to 14x14 finite element matrices. A longitudinal continuous variation of effective material properties is considered by the finite element equations derivation, which can be obtained by homogenization of the spatial varying material properties in real FGM beam. Results of numerical elastostatic non-uniform torsional analysis of the FGM cantilever beam of I-cross-section are presented and the accuracy and effectiveness of the new FGM beam finite element is discussed and evaluated.

Open access
Glaucoma vs. Biomechanical Properties of Cornea

Abstract

The paper deals with the influence of various biomechanical parameters on the intraocular pressure (IOP). The IOP is a very important factor in more accurate diagnosis and better management of glaucoma. To get a more realistic value of IOP the measurement methodology must reflect the patient’s individual biometric and biomechanical parameters, for example age, sex, race, biomechanical properties of cornea, etc. Many measuring methods are based on the applanation of cornea during its loading by the measuring device - tonometers. These tonometers apply the Imbert – Fick law [1], which determines their size. This work also addresses the current approaches to creating more realistic IOP data.

Open access
On the Access to Transverse Shear Stiffnesses and to Stiffness Quantities for Non-Uniform Warping Torsion in FGM Beam Structures

Abstract

The application of first order shear beam theory in the analysis of beam structures made of functionally graded materials requires the access to homogenized stiffness quantities. These quantities depend on the cross-sectional shape and on the spatial variation of constitutive parameters. Some of these stiffness quantities can be evaluated easily by simple integration, however, the access to transverse shear stiffnesses and to stiffness quantities regarding warping torsion is typically cumbersome. In this contribution a novel approach for their evaluation is proposed, which is based on a reference beam problem. Here, we restrict ourselves to double symmetric cross-sections, however, a generalization of the proposed method to the arbitrary case is obvious. Besides that, a novel approach to cover non-uniform warping torsion is included. The proposed method is efficient, since the discretization of the cross-section suffices, and accurate as can be shown in challenging bench mark problems.

Open access
Stochastic Loading of a Sitting Human

Abstract

The aim of this paper is the biomechanical evaluation of the interaction between load forces to which a sitting man and the seat are exposed. All loads, which consider actual anthropometry histograms of human population (i.e. segmentation of human weight, height, centroids, gravity and shape of seat) are determined using the direct Monte Carlo Method. All inputs are based on the theory of probability (i.e. random/probabilistic inputs and outputs with respect their variabilities). A simple plane model (i.e. probabilistic normal forces and bending moments) shows a sufficient stochastic/probabilistic evaluation connected with biomechanics, ergonomics, medical engineering (implants, rehabilitation, traumatology, orthopaedics, surgery etc.) or industrial design.

Open access
A Study on the ‘Compatiblity Assumption’ of Contemporary Multiplicative Plasicity Models

Abstract

Contemporary multiplicative plasticity models are now generally accepted as “proper material models” for modelling plastic behaviour of deformable bodies within the framework of finite-strain elastoplasticity. The models are based on the assumptions that the intermediate configuration of the body is stress-free or locally unstressed, for which no plastic deformation exists that meets the conditions of compatibility. The assumption; however, has never really been questioned nor justified, but was rather taken as an axiom and therefore considered to be generally true. In this study, we take a critical look at the assumption from both, physical and mathematical points of view, in order to investigate whether contemporary multiplicative plasticity models are indeed continuum based and if there are alternatives to them.

Open access
Analysis of the Effect of the Addendum Modification Coefficient for Contact Surfaces of Spur Gear

Abstract

The spur gear is widely used in many types of machines and appliances that is why the research of the connection analysis of them (Tooth Contact Analysis, TCA) is very important because of the development of these gears. The TCA analysis is a complex task because the mathematical description, the CAD modelling process, the overall designing process, the manufacturing process of the gears and the definition of the mechanical parameters have to be known. After the gear designing process the gear pairs have to be analysed by TCA method to determine the typical dimension of the mechanical parameters in case of given load. Knowing of the result we can reason for the appropriate gear geometry of the given construction and working conditions.

Open access