Issue 4
JTAM, Sofia, vol. 10 Issue 4 (1979)

Longitudinal One Frequency Resonant Oscillations of Mechanical Systems with Periodic Structure and Dissipative Relations

S. Butchvarov
High. Inst. of Mech. and Electr. Eng., Sofia


In this work is examined the influence of energy dissipation upon the forced oscillations of mechanical systems with a periodical structure and dissipative relations in the presence of outward resonance. The dissipation of the energy in the material is recorded by Davidenko's hypothesis. The solution is done by using the asymptotical method of Krilov-Bogoliubov.

JTAM, Sofia, vol. 10 Issue 4 pp. 009-018 (1979)

An Improved Hydrostatic Method for Measuring the Friction Moment in Machine Supports

M. Aiatos, E. Hende
200026, Estonian SSR, Polytech. lnst. of Talin

This paper has been reported at the Third National Congress on Mechanics – Varna, 1977.

JTAM, Sofia, vol. 10 Issue 4 pp. 019-021 (1979)
A Statistical Analysis of Monomeasured Deformable Systems with Single and Double Nonlinearity

S. Simeonov
High. Inst. for Arch. and Civ. Eng., 1 Hr. Stnirnenskv Blvd., Sofia

The analyzed system state of eqilibrium has been written down by means of eq. (1) and (2), where the operator A is a potential one, while the metric function A(x) is a symetrical one. In the general case the solution of (1) and (2) is found by means of the process (3), its convergence being proved by (2) – (6). The latter generalizes a number of well known methods. It has been used as a generalizing method of the secants and as a model regula palsi. Computing procedures have been proposed for the different cases of nonlinearity. The cases of unloading and loss of stability have been analyzed as well.

JTAM, Sofia, vol. 10 Issue 4 pp. 022-036 (1979)
Stability of Previously Stressed Reinforced Concrete Thin Wall Bars in Creep

St. Pamuktchiev
High. Inst. for Arch. and Civ. Eng., 1 Hr. Smirnensky Blvd., Sofia

The bars mentioned have been treated according to prof. Vlasov's theory with 1/h > 4. Their stability in creep has been analyzed with the help of the ageing theory. A system of stability differential equations has been derived. The system has been solved with respect to a thin wall bar with two axes of symmetry, loaded by an outer normal force. The Oiler bending critical forces and the specific torsion critical force have been obtained. It has been proved that in the process of creeping the critical forces grow smaller, which leads to structure safety decreasing.

JTAM, Sofia, vol. 10 Issue 4 pp. 037-045 (1979)
The Flow Field Induced by the Torsial Oscillations of a Small Particle in a Spherical Container

Z. Zaprianov, S. Tabakova
Inst. of Mech. and Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

The flow of a viscous fluid between two spheres has been investigated, the inner sphere being oscillating, while the outer one not moving. The flow is caused by the oscillations mentioned. The case of oscillations with high frequency and small amplitude has been analyzed. The solution has been constructed as a double asymptotical series with two parameters concerned. It has been given in a closed form. The results have been illustrated by the flow lines of the stable part of the solution with several numbers of parameters taken into account.

JTAM, Sofia, vol. 10 Issue 4 pp. 046-054 (1979), [Full Article]

A Sound Field in Two Connected Round Cylinder Regions Containing a Fluid

V. Dzhupanov, P. Dineva
Inst. of Mech. and Biomech., Bulg. Acad. Sci , Bl. 8, Geo Milev

The investigation proposed is a continuation of a group of methodic problems, connected with the calculation of the acoustic fields in atomic power stations. There are roundcylindric regions in the corp of the reactor which contain liquid and constructive elements. The acoustic wave propagation has been analysed. The paper presented investigates the sound difraction obtained in the process of analysis of a panel in a liquid. The wave field is created by a wave producer with a given frequency f and previously given law of oscillation U(r,t) = V(r)exp(rot). Thus the boundary problem has been formulated and a solution concerning the velocity potential has been found. In the same time a solution has been found concerning the pressure, the velocity and the intensity of the acoustic field in front and behind the opening.

JTAM, Sofia, vol. 10 Issue 4 pp. 055-064 (1979)
A Stress and Strain State of a Thin Wall Viscoelastic Bar

L. Hadjikov, Hr. Hristov, K. Simeonova
Inst. of Mech. and Bio. Mech. Bulg. Acad. Sc., Bl. 8, Geo Milev

The paper presents an investigation of the stress and strain state of the bar mentioned, its deformability taken into account. The equation of equilibrium has been obtained by means of the principle of virtual work. An algoritm is proposed for obtaining the solution of the system of nonlinear integro-differential equations. The elastic stability of the bar has been analyzed.

JTAM, Sofia, vol. 10 Issue 4 pp. 065-073 (1979)