Issue 1

JTAM, Sofia, vol. 13 Issue 1 (1982)

Some Force Fields Permitting Permanent Rotation of Solids with an Immovable Point

I. Iliev, D. Ganev
Plovdiv, str. "A. Halachev" 47

The problem of existence of permanent rotations of a solid with an immovable point in a potential force field with a force function and without axial symmetry, is considered. It is shown that there are fields not allowing permanent rotations. The functions for which such rotations exist(I), are separated. The weight field is a private case of such a field.

JTAM, Sofia, vol. 13 Issue 1 pp. 011-017 (1982)

The Inverse Problem in Kinematic Analysis of Manipulative Systems

B. Bekiarov, V. Hristov
Inst. of Mech. and Biomech., Bulg. Acad. Sci., bl.8, G. Milev

A method permitting the definition of each configuration of a given manipulative system in which a fixed point of the grip gets in a given point of the space is set forth in the following work. The proposed method is appliable for any space manipulator, if only the zones of attainment are known.

JTAM, Sofia, vol. 13 Issue 1 pp. 018-024 (1982)

Geometry of Point Masses or Modelling of Space Units

M. Konstantinov, V. Zamanov
High Inst. for Mech. and Electr. Eng., Durvenitsa

A method for obtaining optimized, with respect to the configuration, point dynamical equivalent models with partial distribution of masses on the geometric elements of the kinematic doubles of the units, is given in the presented work.

JTAM, Sofia, vol. 13 Issue 1 pp. 025-030 (1982)

A Method for Mathematical Modelling of Onedimension Nonlinear Stohastic Equations

N. Petrov
Inst. of Mech. and Biomech., Bulg. Acad. Sci., bl.8, G. Milev

A method for mathematical modelling of onedimension nonlinear stohastic constitutive equations is given in the work. It allows the construction of deterministic constitutive equations, representing the average properties of the considered media. The method can be used in each case of a solid material with stohastic and nonlinear behaviour. A characteristic feature of the method is that the precision of the used polinomial approximation is defined by an additional condition for adequately good approximation.

JTAM, Sofia, vol. 13 Issue 1 pp. 031-040 (1982)

Creep Buckling of a Column with Rectangular Cross Section Taking Account the Initial Imperfection and Different Creep Exponents

P. Kolev
High Inst. for Arch. and Civ. Eng., Sofia, b. "H. Smirnenski"I

An approximate approach for obtaining the critical time of a column with rectangular cross and noninteger creep exponent is considered in the present paper. The solution of the problem is based on the use of the previously obtained formula of the critical time of the column by integer number of the creep exponent. The obtained result are compared with the available experimental and theoretical data, reported from other authors, and a reasonably good agreement is found out.

JTAM, Sofia, vol. 13 Issue 1 pp. 041-046 (1982)

General Dispersion Equation for the Private Frequences of Perforated Circular Plates

V. Djupanov
Inst. of Mech. and Biom., Bulg. Acad. Sci., bl. 8, G. Milev

In the following work is shown how, using the formulaes for summation of cylindric functions, the dispersion equations for the private frequencies of circular plates with circular perforations can be obtained and written in most general form.

JTAM, Sofia, vol. 13 Issue 1 pp. 047-051 (1982)

Examination of a Turned Turbulent Jet

V. Madjirski, I. Antonov
High Inst. of Mech. and and Electr. Eng., Durvenitsa

Dependences for the distribution of the axial and the tangent velo city components, the pressure and theegection action of a faintly turned jet, are obtained in the present paper. The integral conditions for constancy of the amount and the moment of the amount of movement lengthwise the stream, areused. The obtained results are compared with the experimental ones.

JTAM, Sofia, vol. 13 Issue 1 pp. 052-058 (1982)

Critical Discussion on the Stability of the Plane and Circular Poiseulle Flows

C. Christov
Inst. of Mech. and Biomech., Bulg. Acad. Sci., bl. 8, G. Milev

Results of the known experimental and theoretical works concerned with the transition phenomena in tudes and channels are reanalysed and compared. The carefull analysis shows that the wide accepted (yet classical) discrepancy between the theory and experimental is only apparent and due to the fact that the comparison is made for Reynolds number based on the mean-profile velocity which is a functional of the flow. It is shown that employing the frictional velocity instead of mean-profile one brings the agreement fairly close.

JTAM, Sofia, vol. 13 Issue 1 pp. 059-064 (1982), [Full Article]

Aftercritical Deformation of Thin Orthotropic Shells under Torsion

I. Ivanova
Inst. of Mech. and Biomech., Bulg. Acad. Sci., bl. 8, G. Milev

After critical deformation of shells under torsion is considered in the work, in terms of the generalized variation principle of Pogarelov for anizotropic shells. A formula for the least critical weight is obtained analytically. The influence of the elastic modulus is given in diagrams.

JTAM, Sofia, vol. 13 Issue 1 pp. 065-071 (1982)

To the Static Examination of Thin Closed Shells in Terms of Two-Power Discretization

D. Panev
High Inst. of Arch. and Civil Eng. b. "H. Smirnenski" Sofia

Thin shells with ribs and with an arbitrary form-line are considered. The discrete-continium Vlasov model of solving by energetical method is proposed. The problem of defining the extremals of the functionals of the potential energy is discreted additionally, approximating the function we seek, with new ones from a Sobolev space. Simple standard formulaes, valid under various edge conditions and cross sections, are obtained for forming the system of algebraic equations for the unknown parameters.

JTAM, Sofia, vol. 13 Issue 1 pp. 072-078 (1982)

Influence of the Interaction between Fractures on the Prolonged Durability

G. Zahariev
Bulgarian Academy of Sciences

The process of failure of a plane with double-nonperiodical system of fractures is modelled. The accumulation of volume defects and the interaction among the fractures are taken in account. It is shown that the interaction among the fractures affects the course and some features of the dependence time to failure-constant tensile stress.

JTAM, Sofia, vol. 13 Issue 1 pp. 079- (1982)