Mechanics and Control
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ISSN 2083-6759
e-ISSN: 2300-7079
Issue Date
2011
Volume
Vol. 30
Number
No. 4
Description
Journal Volume
Mechanics and Control
Vol. 30 (2011)
Projects
Pages
Articles
Simulations of fracture in concrete elements using continuous and discontinuous models
(2011) Bobiński, Jerzy Robert; Tejchman, Jacek
The paper presents results of numerical simulations of fracture in concrete using two different approaches. First, fracture was modelled in a smeared way by an elasto-plastic and a damage continuum model. In elasto-plasticity, a Rankine criterion was used. The degradation of the stiffness in the damage model was described as a scalar variable of an equivalent strain measure. To ensure mesh-independent results, a non-local theory was used. Second, fracture was simulated as discontinuities with the aid of cohesive elements and Extended Finite Element Method (XFEM). The experimental benchmark test for concrete by Nooru-Mohamed under mixed mode conditions was modelled. The obtained numerical results were compared with the corresponding experimental ones.
Analysis of effective properties of piezocomposites by the subregion BEM-Mori-Tanaka approach
(2011) Dziatkiewicz, Grzegorz
Recently, many approaches have been proposed to estimate the effective properties of composites. The most typical are: the self-consistent method and the Mori-Tanaka method. However, they are restricted to simple geometries of phases. Also for complex constitutive laws the analytical results are complicated. On the other hand, the combination of numerical methods and these approaches gives an efficient computational scheme for estimating effective properties of composite materials. In this paper the hybrid subregion boundary element method (BEM) and Mori-Tanaka approach is implemented to solve coupled field equations of linear piezocomposites in the unit cell approach and then to determine the effective properties. To obtain the BEM fundamental solutions, the Stroh formalism is used. The numerical examples demonstrate an effectiveness of the BEM-Mori-Tanaka approach.
Elastic properties of composites reinforced by wavy carbon nanotubes
(2011) Górski, Radosław
In the paper the prediction of the elastic Young modulus of single-walled carbon nanotubes (CNTs) and the elastic properties of composites reinforced by straight or wavy CNTs is presented. The properties are evaluated by numerical methods. Nanotubes are modeled and analyzed by the finite element method (FEM). The specific atomistic nature of CNTs is taken into account by using a linkage between molecular and continuum mechanics. The methodology consists in replacing the discrete molecular structure of a CNT with a space-frame FE model by equating the molecular potential energy and the elastic strain energy of both models subjected to small elastic deformations. A three-dimensional frame is further substituted with a one-dimensional beam which represents the reinforcement in a representative volume element (RVE) of the considered composite. The properties of the nano-composite are determined by modeling and analyzing RVEs using the coupled boundary and finite element method (BEM/FEM). A two-dimensional matrix is modeled by the BEM and CNTs by the FEM using beam elements. The waviness and shape of a single fiber or multiple aligned nanotubes on the properties of the nanocomposite are investigated. Sinusoidal or arbitrary shapes of the reinforcement are considered. The influence of volume fraction of the reinforcement and the fiber/matrix Young's modulus ratio on the elastic properties of the composite is also studied.
Modelling of damage evolution in adhesive metal-composite structures for various joint designs
(2011) Končakova, Nataliâ Aleksandrovna; Müller, Ralf; Barth, Franz Josef
A viscoelastic model with the Lemaitre-type damage is applied to simulate the mechanical behaviour of the contact zone of an adhesive aluminum/fiber-reinforced polymer specimen. The damage evolution in this light weight engineering structure is investigated. The joints of aluminium alloy 5754 (AA5754) and carbon fibre reinforced thermoplastic composite CF-PA66 are manufactured by means of adhesion with an epoxy (1K-EP). The contact zone is considered as an interface material. The aim of the research is to study the influence of the interface geometry on the mechanical characteristics of the structure. The finite element method is used to simulate the complex processes in the joint. The aluminium substrate is modeled as an elastoplastic continuum with linear (isotropic) hardening. The polymer composite possesses an orthotropic elastic behaviour. A solid interface approach is used for the discretisation of the damage domain. It is shown that damage evolution depends on the geometry of the interface. The present work contains the numerical analysis of fracture processes in adhesive specimens with square, rectangular- and circle-shaped geometry of the joint.
Orthotropic yield criteria in a material model for timber structures
(2011) Małyszko, Leszek
The continuum structural model for the failure analysis of timber structures in the plane stress state is discussed in the paper. Constitutive relations are established in the framework of the mathematical multisurface elastoplasticity theory with three orthotropic strength criteria that have been incorporated in the model as the plasticity conditions. The invariant form of the criteria is given based on the representation theory of scalar-valued functions of the orthotropic invariants. The model is implemented into a commercial finite element code by means of user-defined subroutines. Introductory implementation tests of the proposed numerical algorithm are presented in the paper.