Issue 3

JTAM, Sofia, vol. 14 Issue 3 (1983)

The 20th anniversary of the Institute of Mechanics at the Bulgarian academy of sciences; the 15th anniversary of the National committee of theoretical and applied mechanics; the 10th anniversary of biomechanics at the Bulgarian academy of sciences; the 10th anniversary of physicochemical mechanics at the Bulgarian academy of sciences.

Opening Speech at the Official Scientific Session

G. Brankov

JTAM, Sofia, vol. 14 Issue 3 pp. 009-011 (1983)

Institute of Mechanics: 20 Years Since

D. Kolarov

JTAM, Sofia, vol. 14 Issue 3 pp. 012-025 (1983)

The 15th Anniversary of the National Committee of Theoretical and Applied Mechanics

G. Brankov

JTAM, Sofia, vol. 14 Issue 3 pp. 026-029 (1983)

On a Problem Formulated by Ishlinski

B. Cheshankov, M. Tseryanov
High. Inst. Mech. Electr. Eng., Darvenitsa

In Ishlinski's "Mechanics of Gyroscopic Systems" motion of a gyro-compass system is investigated and the exact equations of motion are obtained. Some problems, involving motion of the said system for simplified cases, have been considered by other authors. Exact equations of motion of the gyro-compass in the case of resonance in second approximation are investigated. A possibility of special instability occurrence is shown.

JTAM, Sofia, vol. 14 Issue 3 pp. 030-040 (1983)

Method for Calculating Wave-Like Shells

Hr. Hristov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8 Geo Milev

A method for a simplified calculation of wave-like shells, involving sufficient accuracy, is developed. The theory of thinwalled elastic shells, as well as methods of statics, are used. Forces applied on the profile of the transversal contour are determined. The static system thus obtained is solved, and the shell stressed and strained states are determined.

JTAM, Sofia, vol. 14 Issue 3 pp. 041-052 (1983)

Shear Moduli of Orthotropic Two-Phase Media

E. Sobotkova, Z. Sobotka
Czechoslovak Academy of Sciences

Shear moduli of two-phase media are determined on the basis of orthogonal three-dimensional models, representing the idealized structural configuration. Two-phase materials cinsisting of orthotropic matrix and oriented particles of the dispersed phase are considered. For deriving the relations for physico-mechanical shear moduli and ideal standard moduli, the same assumptions have been adopted, which are usual in the theory of rheological models.

JTAM, Sofia, vol. 14 Issue 3 pp. 053-063 (1983), [Full Article]

Axisymmetric Jet Flow Past Body of Revolution

K. Varsamov, A. Haimov
Inst. Nav. Hydromech., Varna

The paper has been presented at the 4th National Congress of Theoretical and Applied Mechanics, Varna 1981.

JTAM, Sofia, vol. 14 Issue 3 pp. 064-067 (1983), [Full Article]

An Analytic Solution of a Variational Problem of Low Drag Airfoil Section with Given Area

I. Nedyalkov1, S. Panev2, P. Petrova2
1Inst. Nucl. Res. Energ., Bulg. Acad. Sci
2Inst. Met. Res. Techn. Met., Bulg. Acad. Sci.

A plane steady incompressible viscous flow past a symmetric airfoil section at Reuel is studied. A classical variational problem of an airfoil section with given area and low drag is solved. A solution of a differential equation is found in a closed form at some simplifications of the considered physical problem and mathematical model. The optimum profile obtained can be used as a first approximation when the same extremal problem is solved by means of another method of minimization.

JTAM, Sofia, vol. 14 Issue 3 pp. 069-075 (1983)

Development of New Smooth Interpolation Methods and Mechanical Models

Hr. Ganev
Inst. Water Problems, Bulg. Acad. Sci., Bl. 4, Geo Milev

If Lagrangean interpolation (which is not a smooth one) is taken as a basis, an analogy between Lagrangean functions (9) for Lk(x) (characterized by properties (10)) on one hand and influence line functions Ek(x) (Eq. (7a) and Fig. 2 and 2) for reactions at the supports of a continuous elastic beam, on the other, can be disclosed. Applying Mohr's method, popular in structural mechancis, and thus avoiding the cumbersome conversion of a (n+1, n+2) matrix, the analogy can be exploited for an effective interpolation. More than that additional implicit information for the first and second derivatives of the interpolated function y = y(x) and for their mechanical interpretation can be involved. The latter adds to the increase of the interpolation smoothness. Thus an expansion of the mechanical analogy is obtained. It increases the accuracy of the smooth interpolation, and the interpolation function not only passes through definite points but satisfies smoothness conditions as well. The latter arise from the use of additional implicit information for values of functions y'(xk) and y"(xk) in these points – see formulae (13), (14) . . . (20).

JTAM, Sofia, vol. 14 Issue 3 pp. 076-081 (1983)

Quantitative Estimation of the Interactions between Shells in a Semi-Infinite Equidistant Row and Immersed in Acoustic Liquid

V. Dzhupanov, D. Karagyozova
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

Steady oscillations of circular cylindric shells with the said characteristics are considered, whereas an infinite liquid layer of constant depth is involved. Using a convenient matrix form of the motion potential, estimates of the number of shells which affect significantly the value of the hydrodydynamic pressure are made. They cover as well errors, occurring as a result of the truncation of the system of equations. Numerical values of the esti- mates are obtained for definite geometrical characteristics and oscillation frequencies.

JTAM, Sofia, vol. 14 Issue 3 pp. 082-094 (1983)