Issue 2

JTAM, Sofia, vol. 11 Issue 2 (1980)

Reaching Region and Working Region of Plane Manipulators

B. Bekiarov, V. Christov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev str.

The paper proposes an inductive method for defining the contours of the regions mentioned. Some topological properties of those two sets have been analysed.

JTAM, Sofia, vol. 11 Issue 2 pp. 013-017 (1980)

Designing of Shock Testing Machines for Fracture of Hard Materials

A. Fedulov
630091 Novosibirsk, Kr. Pr. 54 IGD SO Acad. Sci. of the USSR

There have been derived some relations based on the experimental investigation of the process of hard material shock fracture. Those relations make possible the choosing of the parameters of the shock devices.

JTAM, Sofia, vol. 11 Issue 2 pp. 018-021 (1980)

A Method for Analysis of the Dynamics of Open Kinematic Chains by Means of Computers

V. Tchirikov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev str.

The author analyses arbitrary systems of absolutely hard bodies. Those bodies are connected by means of arbitrary holonomic bonds a configuration which does not contain closed kinematic chains. A computing programme has been made, which constructs and solves the differential equations of motion of an arbitrary system. The computing programme is universal because the solving of the reversed problem of dynamics requires only giving the structure of the system and the active forces and moment actingupon it. This programme may be applied to designing and synthesys of different mechanisms and devices, i.e. to mechanical modelling of robots and manipulators.

JTAM, Sofia, vol. 11 Issue 2 pp. 022-029 (1980)

Inelastic Deformation of Quasihomogeneous Materials

V. Kafka
Inst. of Theor. and. Appl. Mech., Vyšehradska 49, Praha, CSSR

The paper is a review of the author's results obtained in the process of investigation of inelastically deforming bodies, which are macrohomogeneous and micrononhomogeneous. Those bodies are statically loaded above the yield limit.

JTAM, Sofia, vol. 11 Issue 2 pp. 030-035 (1980), [Full Article]

Precise Smooth Interpolation. Interpolation by Means of Expansion of the Function in Maclaurent Series

Chr. Ganev, Kr. Georgiev
Inst. of Water Problems, Bul. Acad. Sci., Bl. 4, Geo Milev str.

The author proposes a definition of precise smooth interpolation. New interpolating formulas have been obtained based on the above definition. The first formula is of Maclaurent type, but only the values of the function have been given. Using them, an approximate value of the function derivative has been obtained. The second formula has been obtained by means of expansion of the function in Maclaurent series, using the approximate presentation of the derivatives in the zero point. A computing programme realization of the formulas has been made and the results have been given in a table.

JTAM, Sofia, vol. 11 Issue 2 pp. 037-040 (1980)

A Numerical Method for Investigation of Nonstationary Space Motions of a Contractable Gas

G. Mahviladze, S. Shterbak
Inst. of Mech. Pr., Acad. Sci. of the USSR, Moscow

A method for numerical integration of Navie – Stokes equations has been proposed in the paper, those equations describing the nonstationary motion of a contractable heat conducting gas. The method leads to an implicit difference scheme along the coordinate division, which has the property of a full approximation. The scheme proposed is effective in the process of calculating stationary and nonstationary processes and spares time. A numerical solution of the two-dimensional problem, concerning the natural convection of a contractable gas in a closed container, has been given. This solution illustrates the method effectivenes.

JTAM, Sofia, vol. 11 Issue 2 pp. 041-053 (1980)

A Generalized Mises Flow

V. Liubenov, T. Tchakurov
High. Inst. of. Mech. and Elactr. Eng. "V. I. Lenin", Durvenitsa

The paper deals with a plane stationary flow of an ideal noncontractable weightless fluid in a channel with an arbitrary oriented plate between its two walls. A conform transformation has been used for defining the complex potential. A solution of the problem in a boundary case has been given as an example. The relation between the jet compression coefficient and the plate slope angle has been illustrated.

JTAM, Sofia, vol. 11 Issue 2 pp. 054-057 (1980)

A Model of Wave Dynamics of Multiphase Media

V. Nakoriakov

The author presents experimental investigations analysing the disturbance propagation in gas-liquad mixture. Waterglycerine solution and carbon oxide bubbles and helium bubbles have been used in the experiment.

JTAM, Sofia, vol. 11 Issue 2 pp. 058-061 (1980)

Pure Bending of a Polymer Beam

L. Rabinovitch, A. Bernadski, V. Shirokolava

The volume coefficint has been experimentally defined in the paper, the general nonlinear equation of Maxwel concerned. A theoretical solution of the problem of polymer beam bending has been performed. The relation between the yield value in bending and pressure and the strain rate has been used in the calculation of the volume coefficient. An algorythm for numeric al solution of the polymer beam bending problem has been developed.

JTAM, Sofia, vol. 11 Issue 2 pp. 062-069 (1980)

On the Problem of Calculating Viscoelastic Wave like Cylindric Shells

L. Hadjikov, Chr. Christov
Inst: of Mech. and Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev str.

The basic equations of mixed type, concerning the above shells have been derived in the paper. An algorythm for solution of the problem with nonlinear constitutive equations concerned has been proposed.

JTAM, Sofia, vol. 11 Issue 2 pp. 070-078 (1980)

On the Stability of a Round Cylindrical Shell with a Variable Thicknes Undergoing Creep

M. Kozarov, P. Kolev
High. Inst. for Arch. and Civ. Eng., Chr. Smirnensky Blvd. 1, Sofia

The paper deals with the stability of a simply supported round cylindrical shell with an average length and lineary changing thickness. The shell has been loaded by means of a load, equally distributed along its ends and parallel to the shell axis. A variational method has been used with the application of the principle of Helinger- Reissner and the theorem of Sanders – McComb – Schlechte. A supposition has been made that there exists an initial shape deviation in the shell average surface, while the critical time has been found according to Hoff criterion. The results show that the shell wall thickening increases shell life time.

JTAM, Sofia, vol. 11 Issue 2 pp. 079-086 (1980)

A Mechanical-Mathematical Modelling of Static Processes in Thermoplastic Polymer Materials

A. Baltov, B. Vidin, Iv. Sgureva
Inst. of Mech. and Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev str.

An author's approach to the problem formulated has been proposed in the paper. A model of the reological behaviour of thermoplastics has been created with static loadings with comparatively small intensities considered.

JTAM, Sofia, vol. 11 Issue 2 pp. 087-093 (1980)