SUMMARYThe statement that theories of inelasticity at ÿnite strains have arrived at a high level of development is only true in conjunction with isotropic material behaviour. From both points of view (theoretical and computational), the extension to anisotropic material behaviour seems to be a complicated task. The statement is especially true when the multiplicative decomposition of the deformation gradient is considered a basis for the formulation. Of special interest are questions related to the mathematical form of the stored energy function or, equivalently, of the constitutive relation for the material stress tensor as the thermodynamical force. This paper deals with the above issues. The anisotropic formulation is accomplished using the notion of structural tensors. Here we suggest that the privileged directions of the material should be transformed in a speciÿc way under the action of the inelastic part of the deformation gradient. The inelastic behaviour is assumed to be governed by evolution equations of the uniÿed type.Numerically, we deal with the full multiplicative structure of the theory. The numerical treatment is developed in full detail. Expressions concerning the local iteration as well as the tangent operator are derived. Various numerical examples with applications to shells are presented which demonstrate the in uence of anisotropy and the applicability of the theory.

No abstract

The free bending vibration of single-walled carbon nanotubes (SWCNTs) is investigated in the present paper. A continuum approach based on nonlocal theory of beam bending is used for natural frequency computation. Analytical solutions of frequency equations are given for four types boundary conditions: clamped-free (C-F), simply-simply supported (S-S), clamped-simply supported (C-S) and clamped-clamped (C-C). The graphical representations of numerical results are shown for the first case of boundary conditions clamped end -free end.

The paper is concerned with the ÿnite element formulation of a recently proposed geometrically exact shell theory with natural inclusion of drilling degrees of freedom. Stress hybrid ÿnite 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.

This paper studies the buckling behavior of simply-simply supported Single-walled Carbon nanotubes (SWCNTs) with and without defects. The buckling of carbon nanotubes without defects was investigated using the Finite element method (FEM) and analytical treatment and that of carbon nanotubes with defects was studied only by FEM. The carbon nanotubes were modeled as beams and shells. Computations showed that beam elements in the given form provided varying results as shells in their numerical or analytical manner for a small aspect ratio. The defects resulted from the removal of randomly determined carbon atoms and beam elements connected to the nodes. The increasing number of defects decreased the critical buckling force of SWCNTs. The decrease in the critical buckling force was almost the same for SWCNTs with the same diameter but with different chirality.

The contribution deals with an experimental investigation of deformation fields of a specimen loaded by combined loading. The experiment was done using non-contact optical method of low-speed digital image correlation. This technique allows investigate displacement as well strain fields. The experimentally obtained results depicted in the paper in a form of color maps and graphs were verified by a numerical simulation performed in Ansys, where two types of meshing were used to demonstrate the coherence between experiment and simulation.

No abstract

No abstract