Issue 3

JTAM, Sofia, vol. 12 Issue 3 (1981)

Synthesis of Manipulator Kinematic Schemes with Respect to Total Service Coefficient

K. Minkov, B. Bekiarov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

The paper presents a generalization of the volume method, used in the optimization of the kinematic schemes of spatial manipulation systems. An algorithm is set forth and an universal computing procedure is created, which is used in the synthesis of manipulation system kinematic schemes. The synthesis is based on the total service coefficient. There is given a numerical example, which concerns the synthesis of link optimal lengths and restrictions in the joints of an 8 degrees of freedom manipulator.

JTAM, Sofia, vol. 12 Issue 3 pp. 013-019 (1981)

An Approach to the Problem Treating the Application of Hamilton-Jakoby's Method to Nonholonomic Systems

Il. Iliev
47 Assen Halatchev Str., Plovdiv

There is analysed the problem which treats the Hamilton-Jakoby's method application to a nonholonomic system, subjected to nonlinear nonintegral links of Tchataev's type. Taking into account the definition of equivalent nonholonomic mechanical systems introduced [1, 21, there are derived the conditions, which make the method applicable. It is illustrated that those conditions could be extended, so that there could be obtained a sufficient number of relations, entirely solving the problem.

JTAM, Sofia, vol. 12 Issue 3 pp. 020-025 (1981)

On the Dynamics of Loop Manipulation System

L. Lilov
Inst. Mech. Biomech., Bulg. Acad. Sci., B1. 8, Geo Milev

The modern industrial manipulators are usually designed as open loop kinematic chains. In the present paper (following [1]) there is proposed a body of mathematics, which models those systems, taking into account their speciality. There are derived formulas, which make possible the effective calculation of the basic kinematic values. The dynamic equations of motion (in generalized coordinates) are explicitly given. The joint forces are determined as well. There are separately discussed special cases of chains with rotation couples and of ones with translation couples. Specific simplifications, concerning those couples, are made. The equations obtained especially suit the application of algorithms and computing operations. This fact makes them an effective tool of the kinematic and dynamic analysis and of the modelling of the controllable motion of industrial manipulators. This holds true especially when the manipulators may be treated as open loop chains.

JTAM, Sofia, vol. 12 Issue 3 pp. 026-033 (1981)

Heat Transfer in the Process of Rotational and Translation Motion of a Sphere Immersed in Liquid

N. Kovatcheva
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

The paper presents an investigation of the convective heat transfer when a viscous fluid flows over a hard sphere. The fluid motion is of rotational and translation character. The analysis refers to Prandtl numbers Pr = O(1) and to Taylor numbers T < l. The solution is obtained using the method of matching of the asymptotic expansions. There are obtained numerical values for the Nusselt number Nu, which are related to the Taylor number T, taking into account two values of the Prandtl number Pr and different values of the Rosby number E. The results are presented by means of graphs.

JTAM, Sofia, vol. 12 Issue 3 pp. 034-043 (1981)

Screw Movements of Dusty Gas

I. Jeleva, V. Stulov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

There is obtained an automodel solution of the equation of two-phase medium screw motion. Taking into account the squared radial velocity, there is obtained a system of 5 ordinary differential equations. The unknown functions are determined by means of this system. There are given classes of particular solutions in the limit cases of a phase independent motion and of "freezing" motion. There is investigated the structure of the singular points of the partial equations, considering small mass concentration. Numerical solutions of the entire system of equations are obtained. Those solutions illustrate the weak effect of the particles on the carrier phase.

JTAM, Sofia, vol. 12 Issue 3 pp. 044-053 (1981)

Thermodynamical Model of Externally Controlled Mechanical Medium

N. Petrov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

Externally controlled mechanical medium is supposed to be a deformable medium, which changes its rheology properties under some external impacts. There is proposed a thermodynamical model in which the effect of the external controlling impact is noted by means of a phenomenological function, called external signal. It is assumed that the controlling impact is included in the dynamic equations, related to the medium external parameter evolution. This theory is applicable to the modelling of vibrocreep processes, of the ionizing radiation effect on the material rheology properties and of other physical actions on deformable media.

JTAM, Sofia, vol. 12 Issue 3 pp. 054-059 (1981)

A Variational Treatment of the Specified Smooth Interpolation Problem

Hr. Ganev, Kr. Georgiev
Inst. Water. Probl., Bulg. Acad. Sci., Bl. 4, Geo Milev

The paper introduces and gives proof of the term "smooth analytic interpolation''. Proof of the variational treatment of the smooth interpolation considered is given as well. In this respect it is started from the obvious and logical principle of the existence of a real curve (connecting a number of previously given points) of minimal length. Thus the problem is reduced to a variational one and extremum is looked for, considering isoperimetric conditions and links. In order to use the mutual orthogonality of Legendre's functions in (-1, +1) interval, it becomes necessary to derive new special functions, namely integral Legendre's functions. General as well as recurrent formulas are given for them. A numerical example is also realized, which illustrates the "smooth analytic interpolation" methods proposed and is of very high accuracy.

JTAM, Sofia, vol. 12 Issue 3 pp. 060-067 (1981)

Eigen Oscillation Forms of Long Structure Systems

L. Tsenov
Inst. on Geophys., Bulg. Acad. Sci., Geo Milev

In buildings under seismic impacts, which lengths are commensurable with the seismic wave length, it is characteristic an appearance of torsional oscillations, even when those buildings are structurally symmetric. The theoretical and experimental investigations indicate the presence of "beating" in the process of oscillation. This makes the building more vulnerable under seismic impacts. The paper gives answers to a number of questions, related to that event. Three mechanical models have been analysed. Conclusions and recommendations, valid for practice, are made on that basis.

JTAM, Sofia, vol. 12 Issue 3 pp. 068-075 (1981)

A Combination Between the Additional Load Method and the Finite Element Method Used in the Solving of Optimization Problems

A. Baltov, St. Todorov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8, Geo Milev

The paper proposes a suitable remodelling of the traditional load method. It aims to create a method for multiple solving of boundary problems of theory of elasticity, taking into account that the body keeps its loading and supports, but changes its stiffness. The investigation aims most of all at the rationalization of the computing procedure involved in the solving of optimization problems.

JTAM, Sofia, vol. 12 Issue 3 pp. 076-083 (1981)

Temperature-Experimental Investigation of the Jung's Modulus of a Bimetallic Steel-Brass Composite

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

There is developed a method for the investigation of the dynamic modulus E of a steel StllJa – brass MC90 bimetallic composite, in the 20-520°C temperature internal. The composite is obtained using the explosion welding method. There are determined the values of the dynamic E-moduli of bi metallic steel-brass composites as well as the modulus of the transition layer of the material considered (in 20-520°C temperature interval). This is done within one loading-unloading cycle.

JTAM, Sofia, vol. 12 Issue 3 pp. 084-089 (1981)

On the Analytic Definition of the Reinforced Concrete Element Curvature during Loading and Unloading

M. Kmetov, T. Igneva
KNIPETEUS, 6 Lenin Sq., Sofa

The paper proposes a method for the calculation of the reinforced concrete element curvature, taking into account the repeatedness of loading and unloading. The method is based on the classical theory for calculation of the curvature in stages I and II. This theory, as a mattr of fact, is developed further by introducing a variable concrete modulus of elasticity, taking into account the physical properties of the reinforced concrete – i.e. the gradual accumulation and subsiding of plastic strain.

JTAM, Sofia, vol. 12 Issue 3 pp. 090- (1981)