Issue 2

JTAM, Sofia, vol. 10 Issue 2 (1979)

On the Propagation of Converting of Lagrange Theorems Concerning Tchapligin Nonholonomic Stystems

A. Karapetian
375019, Erevan, Barekamutian Str. 50 A, Kv. 4

The paper states that the converti ng mentioned is true in the case of Tchapligin nonholonomic systems. In general, the theorem of Lagrange-Rumiantsev is nonconvertive when nonholonomic systems are concerned so it can be generalysed by the Lahua approach. The results known from nonholonomic system theory are applied to the Tchapligin nonholonomic systems, taking into account the effect of the dissipative and the gyroscopic forces on the motion stability.

JTAM, Sofia, vol. 10 Issue 2 pp. 011-016 (1979)

A-Definite Property of the Relations of Geometry, Defined by Means of Lever Plain Mechanism Kinematic Schemes

K. Entchev
High. Inst. of Agr. Eng., Russe

It has been determined that the relations of geometry mentioned possess a property, called “repeating of partial derivatives". This notion enables the equations obtained to take a form in which their structure laws are clearly stated. The paper has distinguished two types of partial derivative repeatedness, i.e. X and Y-repeatedness. A method of treating the geometric relations, possessing this characteristics has been developed.

JTAM, Sofia, vol. 10 Issue 2 pp. 017-024 (1979)

Stochastic Layer Diffusion in Simplest Multidimensional Oscillating Systems

G. Gadiak
Sibirian Dep. of the Acad. of Sci. of the USSR Novosibirsk, 90

The paper analyses the diffusion, based on crossing thin stochastic layers. This effect has been treated as a weak instability of a nonlinear oscillating system with several degrees of freedom.

JTAM, Sofia, vol. 10 Issue 2 pp. 025-031 (1979)

On the Second Law of Thermodynamics Concerning a Singular Surface

P. Marinov
Inst. of Mech. and Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

A generalizing of the second law of thermodynamics has been stated, concerning a singular surface in the mechanics of continua. A new local thermodynamic inequality has been derived. The result obtained is based on Meisner theory in which the local inequality of Clausius-Duhem has been replaced by a local fundamental inequality. A connection between the results obtained and those of Vilmansky (4) has been illustrated.

JTAM, Sofia, vol. 10 Issue 2 pp. 032-037 (1979), [Full Article]

The Influence of the Cyclic Temperature Action on the Stressand Strain Condition of Fiber Reinforced Glass Shell Structures

Ngo The Fong
High. Inst. of Arc. and Civ. Eng. Hr. Smirnensky Blvd. 1, Sofia

The author has defined the deformation in the shell stuctures with the above properties. A cyclic temperature action has been taken into account and a three parameter rheology model has been concerned. The viscosity coefficient has been considered variable.

JTAM, Sofia, vol. 10 Issue 2 pp. 038-044 (1979)

Changes of Elastic Modulus in Surface Layer and its Thickness Evaluation

R. Zuchowski
Institute of Material Science and Technical Mechanics M. Smoluchowskiego 25 50-370 Wroclaw Poland

The variation of the above elastic moduli has been analysed in the paper, the moduli taken as functions of the mechanical characteristics of the material. The influence of the previous plastic deformation has been taken into account. The scale factor has been also considered.

JTAM, Sofia, vol. 10 Issue 2 pp. 045-047 (1979), [Full Article]

The Equations of Caustics for Plate Problems in Bending by Using Complex Potentials

P.S. Theocaris, N.I. Ioakimidis
Greece, Athens 625

The paper has proved that the caustics method is a potential one, which can be used in solving plane problems of theory of elasticity. The equations of the caustics initial curve and of the caustics itself has been given in a complex form. This makes possible the application of the caustics method to the problems of elastic plate bending.

JTAM, Sofia, vol. 10 Issue 2 pp. 048-051 (1979), [Full Article]

Semiempiric Theory of Turbulence Concerning Space Flows of Chemically Reacting Gas Mixtures

G. Vasilev
Inst. of Mech. and Biomech Bulg. Acad. Sci. Bl. 8, Geo Milev

The author has applied the semiempiric theory to the description of chemically reacting gas mixture behaviour. Thus, a generalization of a similar model, based on the equation of turbulence energy, has been given. The theory is applicable to three dimensional flows.

JTAM, Sofia, vol. 10 Issue 2 pp. 052-060 (1979)

Analytic Evaluations of Hydroaccumulator Volume Exploitation

V. Georgiev, V. Mednikarov
Inst. of Mech. and Biomech. Bulg. Acad. Sci., Bl. 8, Geo Milev

Some relations have been derived, evaluating the volume exploitation of hydroaccumulators, used in impulse spraying. The analysis given shows that a previous air compression in accumulator water-and-air section is necessary. Thus, the pressure obtained must reach a value equal to the lower pressure value allowed. When reaching such a value the spurt changes its parameters. A conclusion has been substantiated that the hydroaccumulators should have been completed with low or middle pressure spray appliances. Thus the accumulator volume exploitation should have become more effective. Relations have been derived, which help the system calculation process.

JTAM, Sofia, vol. 10 Issue 2 pp. 061-071 (1979)

On the Effect of the Liquid Filtration Direction Changing upon the Layer Oil Production

R. Mincheva, L. Gerov, O. Tsonev
High. Inst. for Mech. and Electr. Eng., Sofia Durvenitsa

The possibility of increasing the coefficient of oil production of the layer has been analysed in the paper. In the same time the crack-cavern collectrors have been taken into account. Laboratory and industrial analyses have been performed. These analyses have been considered in the present paper.

JTAM, Sofia, vol. 10 Issue 2 pp. 072-076 (1979)

Elastic-Plastic Torsion Problem of a Cracked Plate

I. Mihovsky, Ch. Christov
nst. of Mech. and Biomech., Bulg. Acad. Sci, Bl. 8, Geo Milev

The stress field singularities arising in the vicinity of the crack tips are investigated for a cracked plate under torsion. The case of a power law hardening incompressible material of the plate is considered. The technique applied is based on a certain path independent integral. Numerical results for a series of values of the hardening exponent are presented and analysed.

JTAM, Sofia, vol. 10 Issue 2 pp. 077-083 (1979), [Full Article]

Seismic Loading of Long Constructive Systems

L. Tsenov
Inst. of Geophysics, Bulg. Acad. Sci., Bl. 4, Geo Milev

The paper has proposed a generalization of the existing methods used in defining the calculative seigmic loading. A two-dimensional calcuiating model has been used. Thus, a number of characteristic cases has been described, concerning long constriction systems.

JTAM, Sofia, vol. 10 Issue 2 pp. 084-088 (1979)

An Investigation of Free Nonsymmetric Oscillations of a Circular Conic Shell

G. Mintchev
2 Ts. Petkova Str., Sofia

The author has taken into account only the transversal displacements of a conic shell. Thus, a differential equation, describing the shell bending and oscillating has been derived, the shell fixing being known. The bending equation is an exact one, while the oscillation equation – an approximate one. The results obtained have been used in solving static and dynamic problems in the case of a closed conic shell.

JTAM, Sofia, vol. 10 Issue 2 pp. 089-092 (1979)

An Experimental Analysis of the Stability of a Viscous-Elastic Rod in a Vibrocreep Situation

P. Bekiarova, L. Hadjikov, P. Sotirov
Inst. of Mech. and Biomech. Bulg. Acad. Sci., Bl. 8, Geo Milev

The present paper has proposed an analysis of the rod mentioned above. Specimens of epoxy clay API have been investigated, the specimens having a circular cross section and being fixed nonsymmetrically. The testing has been performed with different values of Rw/R – the amplitude of the periodic load, and W – the frequence of the periodic load, taken into account, the outer temperature value being 22℃. The results obtained give a possibility of obtaining a qualitative and approximately quantitative characteristics of the stablility analysed.

JTAM, Sofia, vol. 10 Issue 2 pp. 093-098 (1979)

A Fracture Criterion of Materials in the Case of a Small Cycle Deformation with a Complex Strained State Taken into Account

L. Lazov, S. Mandjakov
High. Inst. of Mech. and Electr. Eng., Durvenitsa, Sofia

Using the concept of damage accumulation in the material strained, a criterion of material fracture has been derived, concerning their small cycle deformation. The criterion derived allows the definition of the fracture cycle number, taking into account the intesity of the stresses appearing in a weak point of a machine part. This criterion has been controlled experimentally in the process of thin wall tube specimen fracture.

JTAM, Sofia, vol. 10 Issue 2 pp. 099- (1979)