Issue 2
JTAM, Sofia, vol. 6 Issue 2 (1975)

On the Dynamics of Plane Lever Mechanisms

L.T. Kandov, N.G. Jončeva
Sofia, Darvenitsa, Higher Institute of Mining and Geology


Some dynamic problems related to plane lever mechanisms are considered. The concept of a simple kinematics chain is applied as a base for the investigation. An illustrated example is given.

JTAM, Sofia, vol. 6 Issue 2 pp. 009-014 (1975)

Variational Principles in the Non-Holonom Variables of Analytic Dynamics

T.L. Bojadžiev
Sofia, Centre for Research and Training in Mathematics and Mechanics, Bulgarian Academy of Sciences, IV km

It is shown that the equations in non-holonom Lagrange and canonical variables of analytic mechanics can be obtained on the basis of an integral variational principle, analogous to the problem of finding an extremum of a functional with local constraints.

JTAM, Sofia, vol. 6 Issue 2 pp. 015-018 (1975)
On the Viscosoelastics Behaviour of a Two Phase Mixture. I. An Equivalent Model with Elements in Series

P.A. Marinov
Sofia, Institute of Mathematics and Mechanics with Computing Centre, Bulgarian Academy of Sciences, IV km

Gibbs' equation for a two phase mixture of a viscosoelastic matrix and elastic filler based on an equivalent mechanical model with elements in series is derived. A thermodynamic approach, including internal state variables is used. The tensor of total stress σij, the inelastic stress tensor σij" and the respective state equations are defined.

JTAM, Sofia, vol. 6 Issue 2 pp. 019-026 (1975)
On the Stability of a Pure Bending Cylindrical Shell Under Conditions of Creep. II

L.M. Hadžikov1, A.A. Nikišin2, V.P. Fomin2
1Sofia, Institute of Mathematics and Mechanics with Computing Centre
2USSR, Moscow

The stability of a pure bending cylindrical shell is investigated. The material of the shell is cross-link polymer. The algorithm of the numerical solution of the system of non-linear equations is given. The results are compared with experimental data.

JTAM, Sofia, vol. 6 Issue 2 pp. 027-034 (1975)
On a Problem of the Mathematical Theory of the Boundary Layer

G.N. Smirnova1, I. Raičinov2, D.G. Barzakov3
1USSR, V. I. Lenin Moscow State Pedagogical Institute
2Sofia, Georgi Dimitrov Agricultural Academy
3Sofia, Department of Higher Mathematics, Board for Research in Energetics, 51 A. Ivanov Str.

A problem of the motion of incompressible viscous fluid in a parallel-plane boundary layer is considered. The respective boundary problem for Prandtl's equations is transformed into a boundary problem of a second order nonlinear equation using Mises' transformation. Obvious and non-obvious schemes in finite differences are put up and their solubility is proved. A particular case of a parallel-plane inseparable boundary layer of the exponential type is investigated. Computer programs are worked out and the results for this case are compared with the actual values of the velocity components. The analysis shows the advantages of the non-obvious scheme.

JTAM, Sofia, vol. 6 Issue 2 pp. 035-044 (1975)
A Numerical Method of the Strength Problem of an Orthotropic Body with Cylindrical Anisotropy

I.N. Molčanov, I.S. Levčenko
USSR, Kiev, Academy of Sciences of the Ukrainian SSR, Institute of Cybernetics

A cylindrical rotational orthotropic shell is considered. The method of finite differences is applied for determining the stress state.

JTAM, Sofia, vol. 6 Issue 2 pp. 045-048 (1975)
Towards the Question of Excitation of Circular Normal Elastic Waves in Hollow Infinitely Long Thick Walled Cylinders

G.I. Georgiev1, E.K. Lazarov2
1Sofia – Dărvenitza, Higher Institute of Mining and Geology
2Higher Institute of Mechanical and Electrical Engineering

The results obtained by numerical calculations of the radial component of the vector of elastic translations are presented in the paper for the internal and external surfaces of the hollow cylinder depending on the frequency of the elastic oscillation for cylinders with different ratio of the thickness of the cylinder wall and its external radius and made of different materials as well.

JTAM, Sofia, vol. 6 Issue 2 pp. 049-058 (1975)
An Investigations of Post-Buckling Strains of Thin Anisotropic Shells III

V.I. Babenko1, J.A. Ivanova2
1USSR, Harkov 86, Institute of Low Temperature Physics and Engineering, Academy of Sciences of the Ukrainian SSR
2Sofia Institute of Mathematics and Mechanics with a Computer Centre, Bulgarian Academy of Sciences, IV km

The post-buckling strains of inclined anisotropic strictly convex shells are considered under the effect of concentrated force and external pressure. The obtained numerical results are presented in a graphic form. An analytic expression of the lower critical load for a spheric shell of the orthotropic type A under the effect of external pressure is given.

JTAM, Sofia, vol. 6 Issue 2 pp. 059-066 (1975)
Hydrodynamic Stability of a Thin Elliptical Cylindrical Shell

M.I. Kozarov, K. Mladenov
Sofia, Higher Institute of Civil Engineering

The hydrodynamic stability of cylindrical shells with elliptical cross section is considered. The flow is on the external as well as the internal wall. It is assumed that the fluid is ideal and the flow potential. The basic equations are derived on the basis of the moment shell theory. A general solution with given boundary conditions is obtained, A numerical example is considered and some conclusions are drawn.

JTAM, Sofia, vol. 6 Issue 2 pp. 067-076 (1975)
Academy of Sciences of the Georgian SSR. Hydrolic Stroke in Two-Layer Pipe-Lines

A.G. Džvaršeižvili, V.G. Turabelidze, T.Š. Camalašvili
USSR, Tbilisi – 30

A hydrolic stroke on two-layer pipelines is considered. Relations for the velocity during sudden change of pressure when pulp flows in two-layer pipelines are proposed.

JTAM, Sofia, vol. 6 Issue 2 pp. 077-081 (1975)