Issue 1

JTAM, Sofia, vol. 10 Issue 1 (1979)

On the Stability Conditions of a Satellite-Gyrostate System on a Circular Orbit

A. Antchev, L. Lilov
Inst. Mech. and Biomech. Bulg. Acad. Sc. Bl. 8, Geo Milev


The tensor form stability conditions are derived. From them some well known conditions are obtained. A geometrical interpretation of the conditions found is given.

JTAM, Sofia, vol. 10 Issue 1 pp. 011-015 (1979)


On the Measuring System in Mechanics and Particularly in Civil Mechanics

Vl. Hristov
Inst. Mech. Biomech., Bulg. Acad. Sc., Bl. 8, Geo Milev, Sofia

The paper deals with the new measures, used in mechanics according to the international measuring system.

JTAM, Sofia, vol. 10 Issue 1 pp. 016-020 (1979)


On the Propagation Thermoelastic Waves in a Semi-Infinite Medium

P. Marinov, P. Kiriazov
Inst. Mech. Biomech., Bulg. Acad. Sc., Bl. 8, Geo Milev, Sofia

A nonstationary propagation of jumps, concerning temperature, deformations, stresses, velocities and temperature flow vectors in semicontinuum is analysed in the paper. Recurrent relations are found, which determine the above characteristics behind the thermoelastic wave fronts in the semicontinuum. The results obtained generalize some others, previously given by Achenbach.

JTAM, Sofia, vol. 10 Issue 1 pp. 021-027 (1979), [Full Article]


Stress and Strain Calculations in the Finite Element Method

M. Todorov, M. Kovatchev
High. Inst. Mech. Agr. Ruse

The paper deals with the calculation of stresses and strains from displacements, obtained in the course of solving problems of the applied theory of elasticity, using the finite element method. The derivative difference from i to k point and the differential quotient concerning those two points of the displacement function are analysed: Rk = 2/hk[(ux)ixk/hk + (u'y)i(yk/hk) - (uk - ui)/hk], where u(x, y) is the displacement function. Minimizing the functional ∑Rk2min a sistem of linear algebraic equations is obtained, which defines the partial derivatives u'x and u('y)k in point k. All this concernes the space problem as well. Using the Cauchie formulas and Hooke's generalized law one can easily obtain the stresses and strains. An example is given at the end of the paper.

JTAM, Sofia, vol. 10 Issue 1 pp. 028-033 (1979)


Physical Systems with Complex Behaviour

R. Garipov
Novosibirsk 90, Ilitcha Str., D. 7, Kv. 21, USSR

The paper analyses a particular class of relay systems. An equation is obtained, describing the system evolution in time. It corresponds to the equation of motion in mechanics. The equation obtained does not coincide with the well known definition of a finite automatic.

JTAM, Sofia, vol. 10 Issue 1 pp. 034-042 (1979)


Modern Naval Hydromechanics Equipment in Bulgaria

P. Bogdanov
Inst. Naval Hydromech., Varna

In this paper the institute of naval hydromechanics in Varna is presented.

JTAM, Sofia, vol. 10 Issue 1 pp. 043-046 (1979)


Nonhomogeneous Mass Exchange in Round Nozzle Driers

K. Kuzov, S. Kraitchev, A. Melikov
High. Iust. Mech. Electr. Eng., Kv. Durvenitsa, Sofia

The influence of some geometrical characteristics of a “nozzle field – drying material" system over the uniformity of the mass exchange in industrial round nozzle driers is analysed. The nonuniformity of the mass exchange is explained, taking into account that it is caused by the turbulent pulsations of air jets, appearing behind perforated plates. A relation between plate geometry and flow hydrodynamic characteristics is given.

JTAM, Sofia, vol. 10 Issue 1 pp. 047-052 (1979)


On a Stationary Random Process with Special Properties

Hr. Hristov
Inst. Mech. Biomech., Bl. 8, Geo Milev, Sofia

A stationary random process of “blanc noise" type is analysed, its three point third couple being two-dimensinal delta funcion. A class of particularly stationary random processes is built. A special correlation concerning the blanc noize invented, is proposed. This correlation is applied in stochastic solution analysis with nonlinear system of differential equations concerned.

JTAM, Sofia, vol. 10 Issue 1 pp. 053-057 (1979)


A Numerical Analysis of Quet's Two Phase Flow

I. Jeleva
Inst. Mech. Biomech., Bl. 8, Geo Milev, Sofia

A Quet's stationary cylindric flow is analysed in the paper, taking into account the blowing in of inner cylinder surface particles. The particle collision could be neglected, according to the model treated, while particle motion has been defined by the gradient of the working phase pressure and by the forse of the viscous interaction. The particle relative motion has been neglected. The problem has been solved numerically. Relations between the particle velocity components, the working phase and the problem defining parameters have been obtained.

JTAM, Sofia, vol. 10 Issue 1 pp. 058-062 (1979)


A Method for Analysing The Influence of the Strain Velocity History over Metal Plastic Properties

A. Baltov, St. Vodenitcharov
Inst. Mech. Biomech., Bl. 8, Geo Milev, Sofia

A method for metal plastic property analysis has been proposed. Flat Specimens have been used and the influence of the strain velocity history over the surface of plasticity has been analysed.

JTAM, Sofia, vol. 10 Issue 1 pp. 063-070 (1979)


A Way for Calculating the Stresses and Strains Appearing in Sloping Shells with Double Curvature on a Rectangular Base with Temperature Action Taken into Account

Hgo The Fong
High. Inst. Arch. Civ. Eng., Hr. Smirnensky Blvd. 1, Sofia

A thermaly treated sloping shell with the properties mentioned has been investigated. The Vlasov moment theory has been applied. Formulas, defining the stresses and the vertical displacements have been found.

JTAM, Sofia, vol. 10 Issue 1 pp. 071-079 (1979)


On the Triangular Finite Element TUVA 3

Y. Pavlova, T. Karamansky
High. Inst. Arch. Civ. Eng., Hr. Smirnensky Blvd. 1, Sofia

The paper notes that article (1) contains a mistake, concerning the equation (40) development. This mistake has been corrected in the paper presented.

JTAM, Sofia, vol. 10 Issue 1 pp. 080-084 (1979), [Full Article]


An Ivestigation of Oscillations in an Oval Cylindric Shell

K. Mladenov, K. Popova
High. Inst. Arch. Civ. Eng., Hr. Smirnensky Blvd. 1, Sofia

The paper deals with private oscillations of an oval cylindric shell. The problem has been solved linearly on account of Vlasov equations. The thin isotropic shell has an infinite length, its edges being fixed by means of joints. Taking into account the special choice of the approximating function, an exact private solution of the continuity equation has been found, while the other equation in the system has been solved by means of Bubnov – Galjorkin method. A numerical realization has been made and some conclusions have been drawn out.

JTAM, Sofia, vol. 10 Issue 1 pp. 085-092 (1979)


A Plastic Deformation Specific Energy with Pulsating Small Cycle Loading Taken into Account

S. Mandjakov, L. Lazov
High. Inst. Mech. Electr. Eng., Kv. Durvenitsa, Sofia

The paper deals with the change of the specific deformation energy concerning a plastic deformation with the above conditions taken into account. This energy is treated as a summation of macroplastic deformation energy and the scattered energy in the material. Relations, defining the deformation energy as a function of the cycle number and the stress type have been proposed. Those relations have been verified experimentally.

JTAM, Sofia, vol. 10 Issue 1 pp. 093-097 (1979)