Issue 4

JTAM, Sofia, vol. 3 Issue 4 (1972)

Professor Vazlav Olshak (On the Occasion of His 70th Anniversary)

G. Brankov
Bulgarian Academy of Sciences, 7-i Noemvri st., 1 Sofia

JTAM, Sofia, vol. 3 Issue 4 pp. 009-010 (1972)

Stability of a Three Layer Strip Subjected to Finite Elastic Deformations

Al. Rachev
Institute of Technical Mechanics, Bulgarian Academy of Sciences, Geo Milev district, Sofia

The problem for the stability of a finitely pressed strip, consisting of three non-linear elastic layers, is considered. The conditions for loosing stability are deduced by investigation of the small possible deformation, imposed on the initial finite deformation of the strip. The stability equations are obtained for special forms of impartial equilibrium, which have local character-surface instability and contact instability. These equations are valid for the cases in which the cross dimension of some layers of the strip strongly increases.

JTAM, Sofia, vol. 3 Issue 4 pp. 011-022 (1972)

Termoelastic Waves in Transversally Isotropic Elliptic Cylinder

M. Kozarov, Ts. P. Ivanov
Institute of Technical Mechanics, Bulgarian Academy of Sciences, Geo Milev district, Sofia

Propagation of thermoelastic waves in infinite transversally isotropic cylinder with elliptic cross section is considered on the basis of the synthetized theory of thermoelasticity, which takes into account the interaction between the field of strain and temperature. The equation for determining the phase velocities of the wave propagation is obtained as an infinite determinant, equal to zero, from the boundary condition for a stress free boundary surface and for a set form of the heat transfer between the cylinder and the ambient medium. It is shown that four kinds of thermoelastic waves exist in the elliptic cylinder in dependence on the symmetry with regard to the axes of the ellipse. The case of thermoelastic wave propagation in circular cylinder can be obtained from the deduced results.

JTAM, Sofia, vol. 3 Issue 4 pp. 023-036 (1972)

Vibration Damping in Pulley Block Systems

A.V. Andreev
Svoboda district, bl. 2, entr. B, Sofia

When investigating the interaction between the load and the cart at crane suspension, it can be conditionally accepted that they are connected only with one rope. The reduced length of this rope and the conditional point f its fastening with the cart are graph-analytically determined. Damping due to stiffness of the ropes and friction forces of the relative vibrations of the load with respect to the cart, is the subject of the paper. Formulae are deduced for finding the coefficient which takes into account the increase of the tension in the ropes and the overloading of the motor of the elevating gear at swinging of the load.

JTAM, Sofia, vol. 3 Issue 4 pp. 037-052 (1972)

On the Calculation of the Elasticity Modules of Orientated Reinforces Plastics

M. Kmetov
Institute of Constructive Cybernetics, Lenin sq., 1, Sofia

The analytic determination of the elastic modules of orientated reinforces plastics at two-dimensional state of stress and different reinforcing in two mutually perpendicular directions, is considered in the paper. The reduced sections method is applied with additional introduction of the rigidity of the elementary layers. The formula, obtained in the present paper, unlike the existing formulae for calculation, is more general and renders a possibility for comprising of all possible cases of reinforcement. The problem is solved as elastic.

JTAM, Sofia, vol. 3 Issue 4 pp. 053-059 (1972), [Full Article]

Effect of Friction of Deformations in the Interior of a Pressed Solid Concrete Cylinder

K. JamboIiev
Institute of Technical Mechanics, Bulgarian Academy of Sciences, Geo Milev district, Sofia

Investigation, on the effect of the friction, existing in the contact surfaces, on the deformations in the interior of a pressed solid circular concrete cylinder, are surveyed. These investigations are carried out on the basis of results from measuring the six components of the deformation tensor in the cylinder. The analysis of the distribution of the transversal deformation components shows that the cylinder undergoes transversal expansion in the middle part as a result of friction. This expansion increases with the growth of the pressure loading of the cylinder. The effect of the variation of the friction forces of the state of deformation of the cylinder is considered in the paper.

JTAM, Sofia, vol. 3 Issue 4 pp. 061-072 (1972)

On the Rotation Stability of a Rotor

A. Mushinska
Warsaw, Poland

A theorem for the asymptotic stability of the solution of a system of differential equations, describing the motion of a rotor, is proved in the paper. It is proved that the obtained conditions are to certain extent necessary for the asymptotic stability of the zero solution (mere rotary motion of a rotor), since if one of the conditions is not fulfilled, the system may have periodic solutions.

JTAM, Sofia, vol. 3 Issue 4 pp. 073-078 (1972)

Longitudinal Wave Propagation in Unidimensional Visco-Elastic Rod

G. Brankov, N. Petrov
Institute of Technical Mechanics, Bulgarian Academy of Sciences, Geo Miley Distract, Sofia

A solution describing the propagation of forced longitudinal waves in unidimensional 6, 5, ... parametric visco-elastic rod at arbitrary boundary conditions, is compiled. An analytical expression for the absorption coefficient and the phase velocity as frequency functions is obtained. Their variation at introduction of new parameters in the rheological model is investigated.

JTAM, Sofia, vol. 3 Issue 4 pp. 079-086 (1972)