Issue 2
JTAM, Sofia, vol. 5 Issue 2 (1974)

Professor Blagovest I. Dolapčiev, Corresponding Member of the Bulgarian Academy of Sciences – Life and Activities

A. Anchev


JTAM, Sofia, vol. 5 Issue 2 pp. 009-018 (1974)

Formation and Initial Stage of Development of a Boundary Layer on a Parabolic Cylinder Which Begins Moving in an Impulsive Manner

Z. Zaprianov
Sofia, Institute of Mathematics and Mechanics with Computing Centre, Bulgarian Academy of Sciences, Cleo Milev Quarter

The method of matched asymptotic expansions is used in solving the problem of determining the development of a non-stationary boundary layer on a parabolical cylinder which starts its movement impulsively and travels in the direction of the axis of the guiding parabola. An approximate solution with a precision to the second order has been obtained.

JTAM, Sofia, vol. 5 Issue 2 pp. 019-028 (1974)
Erweitertung des Hamiltonischen Variationalprinzips für perkutierten materiallen Systeme
(Expansion of the Hamiltonian Variation Principle for Percutient Material Systems)

I. Constantinescu, E. Tocacci
Rumania,

An expansion is given of the Hawiltonial variation principle for percutient mechanical systems. A functional has been worked out whose extremization determines the structure of the equations of movement of these systems. Boundary cases have been examined and a number of examples have been given.

JTAM, Sofia, vol. 5 Issue 2 pp. 029-040 (1974)
Non-Circulation Spatial Flow around Wing-Body Combinations

D. Dobrev, L. Panov
Sofia, Higher Institute of Mechanical and Electrical Engineering, Department of Hydromechanics, Dârvenica Quarter

A method is described for the numerical solution of the inverse problem of the non-circulation steady spatial flow of ideal incompressible fluid around articulate surfaces of the wing-body type. The authors apply the method of singularities, using various types of concentrated and continuous coatings in a given spatial domain. Rankin's method is used fn plotting the streamlined plane. Results illustrating the possibilities offered by the method have been shown.

JTAM, Sofia, vol. 5 Issue 2 pp. 041-054 (1974)
On the Bifurcation and Stability of Permanent Revolutions of a Heavy Solid Body with One Stationary Point

V.N. Rubanovskij
USSR, Moscow-B-333, Computing Centre of the Academy of Sciences of the USSR, 40, Vavilova Street

A study has been made into the problem of bifurcation and stability of permanent revolutions of a solid body with one stationary point in homogeneous gravitational field on the basis of a possible modification of the Poincaré-Četaev theory about the bifurcation of stationary movements.

JTAM, Sofia, vol. 5 Issue 2 pp. 055-070 (1974)
On the Non-Linear Physical Dependence of Cross-Linked Polymers and Glass-Fibre Reinforced Plastics under Variable Stress

N. Petrov1, G. Zahariev2
1Sofia, Institute of Mathematics and Mechanics with Computing Centre, Bulgarian Academy of Sciences, Geo Milev Quarter
2Central Laboratory of Physico-Chemical Mechanics, Bulgarian Academy of Sciences, Geo Milev Quarter

The authors examine a physical model of a solid and rigid body with reticular structure and work out its corresponding three-parameter rheologic model in which the moduli of the elastic and highly elastic deformations are assumed to be constant. The coefficient of viscosity is obtained as a function of the stress and time for the following cases of loading: permanent, slowly changing and rapidly changing in time.

JTAM, Sofia, vol. 5 Issue 2 pp. 071-076 (1974)
An Amplifying Factor in the Spreading of Surface Waves in the Earth Layer

H. Boncheva
Sofia, Geophysical Institute, Bulgarian Academy of Sciences, Geo Milev Quarter

The author has established the amplification factors of the surface waves travelling in the rock and in the overlying soil layer. It is assumed that the materials of the media in which the wave is propagating are elastic and isotropic, while the waves are harmonic and plane. The rock is considered as half-space.

JTAM, Sofia, vol. 5 Issue 2 pp. 077-084 (1974)
Thermoviscoelasticity with Temperature Rate Dependence

Ts. Ivanov
Sofia, Institute of Mathematics and Mechanics with Computing Centre, Bulgarian Academy of Sciences, Geo Miley Quarter

In the present paper we consider a generalization of the thermovisco-elasticity for Kelvin-Voigt solids when a dependence on the temperature rate is assumed, It is based on the entropy production inequality suggested by Green and Laws [4]. This generalization leads to a stress-strain relation that includes the temperature rate and allows for a finite speed of heat propagation in the linearized theory.

JTAM, Sofia, vol. 5 Issue 2 pp. 085-091 (1974), [Full Article]

Statics of Inhomogeneous Rheologic Media

N. Dimov
Sofia, Higher Institute of Mining and Geology, Dărvenica Quarter

The article presents displacement functions of the transpositions of inhomogeneous rheologic bodies with physical equations of the Bolzmann type. The application is shown of these functions to the problem of torsion of prismatic rods and to the problem of plane stressed and strained state.

JTAM, Sofia, vol. 5 Issue 2 pp. 093-098 (1974)