Gyumri State Pedagogical Institute

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Sarkisyan S.O.,Gyumri State Pedagogical Institute
Journal of Applied Mechanics and Technical Physics | Year: 2012

A number of hypotheses were formulated using the properties of an asymptotic solution of boundary-value problems of the three-dimensional micropolar (moment asymmetric) theory of elasticity for areas with one geometrical parameter being substantially smaller than the other two (plates and shells). A general theory of bending deformation of micropolar elastic thin plates with independent fields of displacements and rotations is constructed. In the constructed model of a micropolar elastic plate, transverse shear strains are fully taken into account. A problem of determining the stress-strain state in bending deformation of micropolar elastic thin rectangular plates is considered. The numerical analysis reveals that plates made of a micropolar elastic material have high strength and stiffness characteristics. © 2012 Pleiades Publishing, Ltd.


Sargsyan S.H.,Gyumri State Pedagogical Institute
Doklady Physics | Year: 2011

A general two-dimensional dynamic theory of micropolar elastic thin shells with independent fields of displacements and rotations, at which shear and related deformations are completely taken into account, is developed. The main set of equations of micropolar elastic thin shells with independent fields of displacements and rotations is expressed. The softened boundary conditions are attached on boundary contour of the middle surface of the shell to the set of dynamic equations considering that the contour coincides with the coordinate line. In the model of micropolar elastic shells, all rotational-shear deformations are taken into account. Based on the constructed dynamic theories of micropolar elastic shells, free and forced vibrations of micropolar shells, are considered.


Sargsyan A.H.,Gyumri State Pedagogical Institute | Sargsyan S.H.,Gyumri State Pedagogical Institute
Journal of Sound and Vibration | Year: 2014

A general model of dynamic bending of isotropic micropolar elastic thin plates with independent fields of displacements and rotations is presented. The model has been justified asymptotically based on the solutions for special cases subject to simplifying assumptions. The model incorporates transverse shear deformations. Neglecting transverse shear, a model of the dynamics of micropolar elastic thin plates is also constructed. Then, we study free and forced oscillations and derive the natural frequencies, the amplitudes of the forced oscillations and the resonance conditions for micropolar elastic hinge-supported rectangular and circular plates. Finally, the basic characteristic features of micropolar plates are numerically analysed for different values of various elastic and inertial constants of the micropolar material. © 2014 Elsevier Ltd.


Drmeyan H.R.,Gyumri State Pedagogical Institute
Journal of Surface Investigation | Year: 2016

The results of experimental and theoretical investigations of the X-ray diffraction patterns from double- or triple-crystal systems and a thick absorbing crystal are presented. The period of the fringe patterns from the double-crystal system is calculated. An expression for calculating the linear enlargement factor in the presence of a crystal-magnifier is deduced. It is proved that the crystal-magnifier does not change the interference pattern but only increases its angular sizes in the scattering plane. © 2016, Pleiades Publishing, Ltd.


Drmeyan H.R.,Gyumri State Pedagogical Institute
Journal of Surface Investigation | Year: 2015

The results of the investigation of deformation fields in a special silicon triple-crystal X-ray interferometer unit under external stress by means of Moiré X-ray-diffraction patterns are presented. The values of the dislocation deformation and the components of the elastic deformation are calculated. It is shown that for a crystal containing dislocations, the value of the elastic modulus decreases. The distribution of the modulus of elasticity in real crystals is determined. © 2015, Pleiades Publishing, Ltd.


Saharian A.A.,Yerevan State University | Manukyan V.F.,Gyumri State Pedagogical Institute
Classical and Quantum Gravity | Year: 2015

We evaluate the positive-frequency Wightman function, the vacuum expectation values (VEVs) of the field squared, and the energy-momentum tensor for a massive scalar field with general curvature coupling for a cylindrical shell in the background of de Sitter (dS) spacetime. The field is prepared in the Bunch-Davies vacuum state and on the shell, and the corresponding operator obeys the Robin boundary condition (BC). In the region inside the shell and for non-Neumann BC, the Bunch-Davies vacuum is a physically realizable state for all values of the mass and curvature coupling parameter. For both interior and exterior regions, the VEVs are decomposed into boundary-free dS and shell-induced parts. We show that the shell-induced part of the vacuum energy-momentum tensor has a nonzero off-diagonal component corresponding to the energy flux along the radial direction. Unlike in the case of a shell in Minkowski bulk, for the dS background, the axial stresses are not equal to the energy density. In dependence of the mass and the coefficient in the BC, the vacuum energy density and the energy flux can be either positive or negative. The influence of the background gravitational field on the boundary-induced effects is crucial at distances from the shell larger than the dS curvature scale. In particular, the decay of the VEVs with distance is power-law (monotonic or oscillatory with dependence of the mass) for both massless and massive fields. For the Neumann BC, the decay is faster than that for non-Neumann conditions. © 2015 IOP Publishing Ltd.


Sargsyan S.H.,Gyumri State Pedagogical Institute
Journal of Thermal Stresses | Year: 2011

The present paper aims at formulating asymptotically grounded assumptions and constructing the general refined applied two-dimensional theory of magnetothermoelasticity of electro- and heat-conducting non-ferromagnetic thin shells on their basis, at which shift deformations in the shell are completely taken into account. Copyright © Taylor & Francis Group, LLC.


Sargsyan S.H.,Gyumri State Pedagogical Institute
International Journal of Mechanics | Year: 2014

In the present paper main equations of threedimensional theory of micropolar elasticity, energetic relations and general variation equation are introduced. Assumptions are accepted which have asymptotic justification and on the basis of these assumptions general applied theory of micropolar thin shells is constructed. Equation of energetic balance and general variation equation are constructed for micropolar elastic thin shells, theorems of uniqueness, existence, Betty's and other energetic theorems are proved.


Sargsyan S.H.,Gyumri State Pedagogical Institute
Journal of Thermal Stresses | Year: 2013

With the account of qualitative results of the asymptotic method of integration of the boundary-value problem of micropolar thermo-elasticity in three-dimensional thin domain of shell, adequate hypotheses are formulated. On the basis of these hypotheses, general mathematical models of micropolar thermo-elasticity of thin shells are constructed. Based on the constructed theories of thermo-elasticity of micropolar thin shells, main statements on the thermo-elasticity of microplar circular cylindrical shells are made. With the consideration of the irregular heating of axisymmetric thermo-elasticity, for the case of hinged supported edges, numerical results are obtained. Based on the analysis of numerical results, effects of micropolarity of the material are shown. © 2013 Taylor and Francis Group, LLC.


Sargsyan S.H.,Gyumri State Pedagogical Institute
Physical Mesomechanics | Year: 2012

The paper formulates general hypotheses of micropolar elastic thin shells that are given asymptotic validation. Using these hypotheses and three-dimensional Cosserat (micropolar, asymmetric) theory of elasticity, general two-dimensional applied models of micropolar elastic thin shells with independent displacement and rotation fields, constrained rotation and low shear rigidity are constructed to suit dimensionless physical parameters of the shell material. The constructed micropolar shell models take into complete account transverse shear strain and related strain. Models of micropolar elastic thin plates and beams are particular cases of the constructed micropolar shell models. An axially symmetric stress-strain state problem of a hinged cylindrical micropolar shell is considered. Numerical analysis is used to demonstrate effective strength and rigidity characteristics of micropolar elastic shells. © 2012 Pleiades Publishing, Ltd.

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