Issue 1
JTAM, Sofia, vol. 14 Issue 1 (1983)

Accuracy of Systems with a Tree-Like Structure and Pairs of an Arbitrary Class

L. Lilov, B. Bekyarov
Inst. Mech. Biomech., Bulg. Acad. Sci., bl. 8 Geo Milev


A mathematical model is created and compact analytical expressions are derived for the error estimation, regarding positioning and orientation of a meth anical system with a tree-like structure and arbitrary kinematic pairs. All significant error sources are taken into consideration, namely errors arising from an inaccurate realization of the generalized coordinates, errors due to the existance of backlash in the pairs and errors resulting from the inaccurate realization of the link metric characteristics. The mathematical model allows for the deterministic or stochastic error estimation, or for an estimation according to maximum.

JTAM, Sofia, vol. 14 Issue 1 pp. 011-021 (1983)

A Theorem on Nonholonomic System Stability

Il. Iliev
Plovdiv, 47 As. Halachev Str.

The author applies Lyapunov-Malkin's theorem to the proof of a theorem, concerning stability of a nonholonomic system. What is determined is the structure of the generalized forces, whereas the theorem proved could be applied to the system. In literature on stability a concept has won recognition that the set of equilibrium states has a dimensionality greater than or equal to the number of nonholonomic bonds [2]. It is proved that at definite conditions the set dimensionality could be less than that number, in particular the system could possess isalated equil ibriurn states. Examples aregiven.

JTAM, Sofia, vol. 14 Issue 1 pp. 022-027 (1983)
Hydroelasticity of Nuclear Reactors – Ideas, Development and Scientific Research Practice

G. Brankov, A. Golovkina, V. Dzhupanov
Inst. Mech. Biomech., Bulg. Acad. Sci., bl. 8, Geo Milev

General considerations on structures, loadings, computing criteria and scientific research, which ensure the reliability of PWR are given. The classification of structural elements (rods, tubes, perforated plates, shells) appearing to be the subject of the hydroelastic, problem, is discussed. The general ideas of the structure of the solving equation of the element hydroelastic vibration in most general terms are followed in detail. The hydroelasticity methods are described briefly. Examples from scientific research practice, concerning SMIRT, are given. Different aspects of the research organization are discussed, taking into consideration the status of hydroelasticity. For reasons of brevity only 77 references (including works of scientists from the USSR, USA, Canada, Bulgaria etc.) are given in the survey.

JTAM, Sofia, vol. 14 Issue 1 pp. 028-049 (1983)
An Investigation of the Stressed-Strained State of an Elastic Matrixwith a Spherical Elastic Inclusion and in the Presence of Peeling – I

V. Valeva, G. Brankov
Inst. Mech. Biomech., Bulg. Acad. Sci., bl. 8 Geo Milev

What is obtained is a system of two singular integral equations for the determination of the unknown contact stresses, occuring in an infinite elastic space with a spherical cavity, where an elastic sphere is placed. Loading is specified by two independent axisymmetric stress components applied to infinity.

JTAM, Sofia, vol. 14 Issue 1 pp. 050-056 (1983)
Methods for the Treatment of Some Oscillating Viscous Flows

Z. Zapryanov, Hr. Hristov, S. Tabakova
Inst. Mech.Biomech., Bulg. Acad. Sci., bl. 8 Geo Milev

What is investigated is the fundamental problem of nonlinearity-viscosity interaction in oscillating flows and a secondary flow emergence. Three problems are analyzed: a two solid sphere hydrodynamic interaction when the spheres execute transiatory oscillations, a fully developed flow in a thoroidal pipe and the viscous flow between two concentric spheres which execute rotary oscillations. Numerical and assymptotic methods of solution are involved: the method of matching the singular assymptotic expansions is applied to the case of high frequencies, while the numerical method of fractional steps is employed for the case of moderate frequencies.

JTAM, Sofia, vol. 14 Issue 1 pp. 057-069 (1983)
On the Instability of a Liquid Capillary Jet Flowing into an Immiscible Liquid

St. Radev, B. Chavdarov, Iv. Penchev
Inst. Mech. Biomech., Bulg. Acad. Sci., bl. 8 Geo Milev

The equations of a perturbated flow for a capillary viscous jet, flowing into a viscous medium, are solved in a general linear treatment. The method of differential Gauss eliminations, discussed in (17), is applied to solve the Orr-Somerfeld eigenvalue problem. The present method is applicable to large-Reynolds numbers and is characterized by high accuracy and economy. An experimental study has been carried out to determine the influence of the nozzle upon the jet length. A comparison has been made between numerical and the experimental results, showing that the present theory describes the phenomenon satisfactory in the domain of low initial jet velocities.

JTAM, Sofia, vol. 14 Issue 1 pp. 070-078 (1983), [Full Article]

A Determination of the Boundary Layer Characteristics during the Filling up of a Vertical Cylindric Pipe by a Heavy Viscous Fluid

Sl. Slavchev, K. Daskalov
Inst. Mech. Biomech., Bulg. Acad. Sci., bI. 8 Geo Milev

The characteristics of an unsteady boundary layer are determined. The layer develops on the internal surface of a semi infinite vertical pipe during filling up with a heavy viscous fluid. What is taken into consideration is the effect of the fluid viscosity on the change of the rate of filling up and on the position of the fluid free surface, both depending on time.

JTAM, Sofia, vol. 14 Issue 1 pp. 079-088 (1983)
An Investigation of the Dynamic Processes of Inelastic Body Deformation and Fracture

A. Baltov
Inst. Mech. Biomech., Bulg. Acad. Sci., bl. 8 Geo Milev

A survey of some investigations in Bulgaria, concerning the dynamics processes of inelastic body deformation and fracture is made. The paper has been presented at the conference on "Scientific Foundations of the Mechanics of Machines, Structures and Processes of Technology" Frunze, USSR, 24-28 May, 1982.

JTAM, Sofia, vol. 14 Issue 1 pp. 089- (1983)