86 research outputs found
Mechanics of Systems of Affine Bodies. Geometric Foundations and Applications in Dynamics of Structured Media
In the present paper we investigate the mechanics of systems of
affinely-rigid bodies, i.e., bodies rigid in the sense of affine geometry.
Certain physical applications are possible in modelling of molecular crystals,
granular media, and other physical objects. Particularly interesting are
dynamical models invariant under the group underlying geometry of degrees of
freedom. In contrary to the single body case there exist nontrivial potentials
invariant under this group (left and right acting). The concept of relative
(mutual) deformation tensors of pairs of affine bodies is discussed. Scalar
invariants built of such tensors are constructed. There is an essential novelty
in comparison to deformation scalars of single affine bodies, i.e., there exist
affinely-invariant scalars of mutual deformations. Hence, the hierarchy of
interaction models according to their invariance group, from Euclidean to
affine ones, can be considered.Comment: 50 pages, 4 figure
A symmetry classification for a class of (2+1)-nonlinear wave equation
In this paper, a symmetry classification of a -nonlinear wave equation
where is a smooth function on , using
Lie group method, is given. The basic infinitesimal method for calculating
symmetry groups is presented, and used to determine the general symmetry group
of this -nonlinear wave equation
Thermoelastic Damping in Micro- and Nano-Mechanical Systems
The importance of thermoelastic damping as a fundamental dissipation
mechanism for small-scale mechanical resonators is evaluated in light of recent
efforts to design high-Q micrometer- and nanometer-scale electro-mechanical
systems (MEMS and NEMS). The equations of linear thermoelasticity are used to
give a simple derivation for thermoelastic damping of small flexural vibrations
in thin beams. It is shown that Zener's well-known approximation by a
Lorentzian with a single thermal relaxation time slightly deviates from the
exact expression.Comment: 10 pages. Submitted to Phys. Rev.
On higher order gradient continuum theories in 1-D nonlinear elasticity. Derivation from and comparison to the corresponding discrete models
Higher order gradient continuum theories have often been proposed as models for solids that exhibit localization of deformation (in the form of shear bands) at sufficiently high levels of strain. These models incorporate a length scale for the localized deformation zone and are either postulated or justified from micromechanical considerations. Of interest here is the consistent derivation of such models from a given microstructure and the subsequent comparison of the solution to a boundary value problem using both the exact microscopic model and the corresponding approximate higher order gradient macroscopic model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42682/1/10659_2004_Article_BF00043251.pd
Possible configurations for Weiss domains in uniaxial ferroelectric crystals
The variational principle proposed in another paper of ours [Internat. J. Engrg. Sci. 30 (1992), no. 12, 1715--1729; MR1185410 (93h:82078)] is here applied to derive the configuration of Weiss domains in uniaxial crystals. It is proved that the configuration which was proposed by L. Landau and E. Lifshits [Phys. J. Sowjet. 8 (1935), no. 2, 153--169] is not possible even in the presence of an electric field. Moreover, another possible configuration is proposed in the absence of an electric field
Structure of Weiss domains in elastic ferroelectric crystals
The structure of Weiss domains in ferroelectric crystals in each of which the polarization vector is constant, is investigated through a new variational principle. The general field equations are obtained and it is shown that in the presence of external electric field the total electric field is also constant in Weiss domains but is usually different from that of the polarization field. Moreover, it is proved that domain walls can only be planar surfaces. Finally the case corresponding to pure polarization fields is also treated and an illustrative problem is considered
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