Issue 1

JTAM, Sofia, vol. 16 Issue 1 (1985)

Extreme Evaluation of the Accuracy Characteristics of a Manipulation System

B. Bekjarov, Sl. Lazarov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

Local and global characteristics of the functional capabilities of a manipulation system are analysed. However, computation algorithms are designed and software for the estimation of the accuracy characteristics of an arbitrary manipulation system is provided as well.

JTAM, Sofia, vol. 16 Issue 1 pp. 011-016 (1985), [Full Article]

On the limits of Application of the Precession Equations of Gyroscope Systems

A. Cheremenski
Inst. Mech. Biomech., Bulg. Acad. Sci., BI. 8

A solution of the problem of stability of stationary, nonstationary and nonlinear mechanical systems is provided, by employing the Klimushev-Krasovski method. The systems, however, consist of rotors of large kinematic moment. The paper provides, as well, an example that confirms the method effectiveness.

JTAM, Sofia, vol. 16 Issue 1 pp. 017-022 (1985)

Criterion for a Uniform Asymptotic Stability of Discrete Systems

E. Rusev
PU „P. Hilendarski", Plovdiv

The paper formulates a criterion for the asymptotic stability of discrete systems, whereas considerations are based on an investigation performed by Kalitin.

JTAM, Sofia, vol. 16 Issue 1 pp. 023-026 (1985)

Influence of Gripper's Motion on Control Synthesis of Manipulator Dynamics

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

The effect of the clamp kinematics on the regional dynamic motion is investigated. However, the authors design and employ a method for the synthesis of the control of a "point-to-point" manipulator. Positioning of a robot by employing cylindric coordinates is performed, and deviation is calculated, disregarding the clamp configuration. A synthesis of the control of a nonstationary regional system is made, as well, for a given clamp trajectory.

JTAM, Sofia, vol. 16 Issue 1 pp. 027-031 (1985), [Full Article]

Some Properties of the Potential Energy Functional in the Theory of Elastic Stability

T. Ivanov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

Some characteristics of the potential functional are investigated. They are usually employed for the determination of the equilibrum state of an elastic body undergoing conservative impacts. Moreover, they are based on properly formulated definitions that provide the proof of a number of theorems. It seems worth noting that the author's definitions impose restrictions on the type of the potential energy, which are weaker than the ones formulated by Coiter. Coiter's results on stability can still be proved.

JTAM, Sofia, vol. 16 Issue 1 pp. 032-037 (1985), [Full Article]

The Effects of the Harmonics of Love-Raileigh's Waves on the Spectral Structure of Synthesized Accelerograms

I. Paskaleva, G. Georgiev, S. Simeonov
CLSMSI, Bulg. Acad. Sci., Bl. 3

To design structures undergoing seismic impacts, one needs to employ synthesized accelerograms if real records lack. However, the accelerogram generation input consists in the velocities of Love-Raileigh's surface waves. The authors propose a method of solution based on a correction of the Fourier transformations, the latter being performed by introducing scale factors. Hence, synthesized accelerograms are obtained that account for the basic tone and for one, two, three and four harmonics as well. The response, as well as Fourier's spectra are estimated as a result, regarding the number of harmonics. What is established is that the basic tone is not able to provide effective seismograms for the design of seismic-resistant buildings.

JTAM, Sofia, vol. 16 Issue 1 pp. 038-045 (1985)

A Model of the Oscillations of a

E. Manoah
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

The free oscillations of a system of two clamped circular plates, connected by long, thin and elastic pipes, are investigated. Moreover, a model of a pointwise plate-pipe junction is adopted (pipes are clamped to the plates). The problem is solved analytically by splitting the solution into two terms, e. basic and compensating ones. The bar effect on the plate motion is specified by the action of the bending moments applied to the bar tips. The frequency equations, as well as expressions for the oscillation forms, are obtained. However, simplifications due to the geometry symmetry are taken into account as well. What is analysed in addition is the case of absolutely rigid supports. Numerical examples illustrate the effect of the pipe (bar) number and distribution on the first several eigen frequencies.

JTAM, Sofia, vol. 16 Issue 1 pp. 046-056 (1985)

Nonparallel Instability of a Liquid Capillary Jet

S. Radev
Inst. Mech. Biomech., Bulg, Acad. Sci., Bl. 8

The author employs one-dimensional model for the investigation of the instability of a liquid capillary jet. An analysis of the instability, involving large Froude numbers, is performed. Moreover, a first order approximation of the jet contraction and acceleration is taken into account. The wave number variation, the coefficient of the disturbance growth along the jet and the jet length are calculated.

JTAM, Sofia, vol. 16 Issue 1 pp. 057-065 (1985), [Full Article]

Flow of a Viscous Contractible Fluid around a Counter Scarp

R. Petkov, V. Simeonova, V. Matakiev
Inst. Water Problems, Bulg. Acad. Sci., Bl. 1

An analysis of the flow is performed and the flow parameters are determined for a zero angle of attack. Moreover, laminar and turbulent flow is considered in a stationary treatment.

JTAM, Sofia, vol. 16 Issue 1 pp. 066-069 (1985)

A Rule of Nonsymmetric Anisotropic Hardening

N. Bontcheva, A. Baltov, St. Todorov
Inst. Mech. Biomech., Bulg. Acad. Sci. Bl. 8

A plasticity condition is proposed, whereas the preliminary plastic defor¬mation provides nonsymmetry of the plasticity surface. Nonsymmetry, however, consists in a blowing-up of the surface along the direction of the preliminary loading and into a flattening along the opposite direction. It is provided by a term which is an invariant quantity and contains the components of both the stress and the microstress tensors (the latter, however, is related to the preliminary plastic deformation). A possibility to a successful treatment of the existing experimental data is revealed.

JTAM, Sofia, vol. 16 Issue 1 pp. 070-083 (1985), [Full Article]

Unsteady Flow of the Lubricant of Elasto-Hydrodynamic Sliding Bearings under Small Deformations

V. Aleksandrov
High. Inst. Arch. Civ. Eng., 1 Hr. Smirnenski Blvd.

The author considers the lubricant flow in bearings of finite length, by taking into account the relatively small deformations of the neck elastic coating. The lubricant is considered to be an incompressible Newtonian fluid and the solution is performed for averaged values of temperature and viscosity. Local inertial forces have been taken into account only. A differential equation for the calculation of the additional hydrodynamic pressure is obtained. It is constituted, however, by the contact deformation. The finite difference method is employed. Results show that both the rubbing surface deformability and the local inertial forces imply the reduction of the pressure maximum values.

JTAM, Sofia, vol. 16 Issue 1 pp. 084-092 (1985)

Antisymmetric Distribution of Thermal Stresses in the Vicinity of a Flat External Crack in an Infinite Solid

M. Lal
School of Studies in Mathematics, Jiwaji University Gwalior 7-44011, India

An attempt has been made to solve antisymmetric distribution of thermal stress in the vicinity of a flat external crack in an infinite solid. It is assumed that the temperature is prescribed inside the crack while the flux at the outside of the crack. The problem is reduced into a pair of dual integral equations and the closed form solution has been obtained.

JTAM, Sofia, vol. 16 Issue 1 pp. 093-102 (1985), [Full Article]