Issue 4
JTAM, Sofia, vol. 5 Issue 4 (1974)

Corresponding Member Prof. Dr. Georgi Bradistilov – 70 years

Editorial Board


JTAM, Sofia, vol. 5 Issue 4 pp. 009-012 (1974)

On Thermowave Visco Plasticity

A. Baltov, K. Vasilev
Institute of Mathematics and Mechanics with Computer Centre, Bulgarian Academy of Sciences, IV km, Sofia

Visco-plastic material subjected to impulsing temperature and mechanical loadings is considered. The basic simultaneous equations for the thermowave visco-plasticity are obtained and investigated. The equations of corresponding characteristic elements are deduced. The expressions for velocities of thermomechanical wave propagation are obtained. Corresponding results are analysed.

JTAM, Sofia, vol. 5 Issue 4 pp. 013-022 (1974)
On the Convergence in the Method of Nonlinear Optimization

G. Donat, K.H. Elster
Halle, GDR

In direct methods of non-linear optimization the convergence conditions are often absent. The authors give the necessary and sufficient convergence conditions according to Tzengvill using Petern-Sarje method improved by Hook and Jeevs as example. In this case quasi-unimodule and differentiated quasi-unimodule target functions play a great role.

JTAM, Sofia, vol. 5 Issue 4 pp. 023-028 (1974)
Asymptotic Analysis of the Deviations of the Non-Linear Wave Solution from the Linear Solution at Unidimensional Transition Processes of Elastic Deformation

U.K. Nigul
Tallin, ESSR

The method of consecutive integration of the linear heterogeneous wave equations for solution of the unidimensional wave problem described by quasilinear wave equation is considered in this paper. The influence of non-linear effects on the transitional wave process is investigated.

JTAM, Sofia, vol. 5 Issue 4 pp. 029-036 (1974)
Laws of Conservation for Non-Potential Systems

L. Bojadjiev
Department of Mathematics and Mechanics, 6, A. Ivanov Blvd, Sofia

On the basis of the transformation characteristics of the arbitrary group of continued transformations of configuration space of non-potential system the analog of the Tkalich fundamental conservation law is obtained. Non-potential forces lead to limitations of the transformations group. These limitations are given in explicit form. In the particular case when the transformations group is N-parametric group of Lee the analog of the first Neuter's theorem is obtained.

JTAM, Sofia, vol. 5 Issue 4 pp. 037-040 (1974)
On the Calculation of Cylindrical Glass-Fibre-Reinforced Plastic Shell Partially Filled with Liquid with Regard to the Creep

G.D. Batsinov, Y.I. Karpenko
18, R. Popovich Str., Varna-2

The cylindrical glass-fibre-reinforced plastic anisotropic shell with regard to the creep is considered. Semimomentless theory is used. The formulae for determination of translations and strains are obtained. A numerical solution is found and graphs of the main strains are drawn in the particular case of the shell freely supported by two ends and partially filled with liquid.

JTAM, Sofia, vol. 5 Issue 4 pp. 041-046 (1974)
Axial Asymmetric Bending of the Circular Plate at Creeping

M. Kishkilov, P. Kolev
Higher Institute of Civil Engineering, Department of Theoretical Mechanics, Sofia

Stress and strain state of a circular plate fixed along contour at axial asymmetric bending in the conditions of creep is investigated. The loading is distributed according to the linear law along the radius and sinusoidal law along the ring. Cubic creep law is assumed. Basic differential equations are obtained by means of the theorem of Sanders-McComb-Schlechte. The conclusions are deduced on the basis of numerical solution obtained by means of computer.

JTAM, Sofia, vol. 5 Issue 4 pp. 047-054 (1974)
Movement of Fishes in Ideal Liquid without Formation of Vortexes

R.M. Garipov
Novosibirsk, USSR

The movement of fishes as vortex-free flow in ideal incompressible liquid in the absence of external force fields is investigated. The optimization problem of fish movement velocity is considered.

JTAM, Sofia, vol. 5 Issue 4 pp. 055-062 (1974)
On the Invariance up to the Higher Derivatives in the Movement Law of the Machine Units with Variable Mass

E.S. Stanchev, N.D. Minehev
N. I. Vaptsarov Higher National Naval School, Department of technical mechanics, Varna

The problem of the synthesis of machine units on the basis of movement independence of arbitrary mass from the dynamic model of forces applied to other arbitrary mass is the subject of the present paper. It is established that this problem is reduced to the synthesis of mechanisms according to the given transfer functions.

JTAM, Sofia, vol. 5 Issue 4 pp. 063-070 (1974)
Stability of Long Cylindrical Shell at Simple Bending in Conditions of Creep

L.M. Hadjikov
Institute of Mathematics and Mechanics with Computer Centre, Bulgarian Academy of Sciences, IV km, Sofia

The stability of long cylindrical homogeneous polymer shell at simple bending under the effect of constant moment and temperature is investigated. The mechanomathematical model of Maxwell-Gurevich-Rabinovich is used in the investigation.

JTAM, Sofia, vol. 5 Issue 4 pp. 071-072 (1974)
Summation of Some Fourier Series and Its Application in Structural Mechanics

I.G. Kolchakov
Institute of Construction Cybernetics, 6, Lenin Square, Sofia

A number of Fourier series applied in the structural mechanics are sumarized. Initial functions are given in closed and graphic form. This investigation makes possible the improvement of convergence of some Fourier series obtained during calculation of thin-walled constructions or girder systems.

JTAM, Sofia, vol. 5 Issue 4 pp. 073-088 (1974)
Indirect Method for Determination of the Tensile Strength of Brittle and Brittle-Plastic Materials

G.E. Andreev
61, G. Milev str., Sofia-11

The indirect method for determination of the tensile strength of brittle and brittle-plastic materials is considered by means of special arrangements with needle-shaped heads.

JTAM, Sofia, vol. 5 Issue 4 pp. 089-096 (1974)