Issue 4

JTAM, Sofia, vol. 20 Issue 4 (1989)

Identification of Inertial and Dissipative Parameters of Industrial Robots

P. Genova
High. Inst. Mech. Electr. Eng., Sofia

The present paper consists of two parts. It is devoted to methods which identify generalized inertial and dissipative parameters when the experimental treatment is one and the same. The identification methods are based on the closed form of the differential equations that have been derived symbolically. The first part deals with the general treatment of a test motion scheme. The necessary number of experiments has been minimized. What is avoided is the configuration influence on dissipative characteristics. An illustration is made and the method is applied to a "Versatran" type regional system. The second part of the paper is devoted to concrete experimental schemes and computation treatment of "Electrolux" and "Pickomatic" type manipulation systems.

JTAM, Sofia, vol. 20 Issue 4 pp. 011-021 (1989)

On the Kinematic Error Estimation of a Membrane Connector

J. Jordanov, V. Penev
High. Inst. Mech. Electr. Eng., Gabrovo

Often, the connection of photoelectric "angle-code" type transformers is done by membrane connectors. What is required when projecting and choosing the connector is the estimation of the kinematic error which has been brought by the connector during the connecting. The paper deduces some relations that help the kinematic error estimation. The error itself has been induced by dimension deviations, connector details form and disposition. The kinematic error is shown and calculated for a connector with a comparative low accuracy of the dimensions and the disposition deviations of the details axes and surfaces.

JTAM, Sofia, vol. 20 Issue 4 pp. 022-027 (1989)

Some Results of the Processing and Analysis of Strong Motion Records of the Strazhitsa Earthquake of 7.12.1986 and the Aftershock of 21.01.1987

G. Georgiev, I. Paskaleva
CLSMEE, Bulg. Acad. Sci., Block 3

The earthquake of 7.12.1986 and the strong aftershocks that followed it were recorded by the network of accelerographs situated in the region of the town of Strazhitsa on an area of about 2000 km2. A number of records were obtained but here only records of 7.12.1986 with M = 5.7 and the records of the aftershock of 21.01.1987 with M = 3.9 will be analized. 14 horizontal and 7 vertical components are processed and analized. A criterion is proposed to estimate the lower limit frequency in the accelerogram correction.

JTAM, Sofia, vol. 20 Issue 4 pp. 028-034 (1989), [Full Article]

On Structural Modelling for Seismic Analysis with Hydrodynamic Interaction

B. Yanev

The hydrodynamic interaction of the structural components of a dam is investigated for earthquake induced effects. Structural deformability and water compressibility are taken into account. Results are compared to those obtained by traditional analysis. A practical approach is developed for adapting available computer software to the specific requirements of the existing structure. The modelling of the structural elements is incorporated in the analysis of the global structural behaviour under conditions of maximum credible earthquake.

JTAM, Sofia, vol. 20 Issue 4 pp. 035-040 (1989), [Full Article]

Loading Velocity and Temperature Influence on Constructional Steel Protraction Limit

K. Minchev
IMTM, Bulg. Acad. Sci., Block 1

The paper presents some results concerning constructional steel protraction limit and its values under static and dynamic loading. Test bodies with V-type thread have been used under three-point bending. The protraction dynamic limit values of the investigated steel are obtained by experimental static mechanical characteristics. The experimental values are compared to the empiric ones. A possibility is shown to use the cited relations in protraction limit determination under different temperature tests.

JTAM, Sofia, vol. 20 Issue 4 pp. 041-045 (1989)

Development of Weak-Conductive Fluid Electro-Convection in a Free Surface Thin Layer. I. Analysis of the Basic Equations

S. Slavchev, D. Kulova-Nenova
Inst. Mech. Biomech., Bulg. Acad. Sci., Block 4

The development of weak-conductive viscous fluid in a horizontal thin layer with deformable free surface is examined under tangent electric tensions due to non-homogeneous electric field. The first part of the paper analyses the equations system of electrohydrodynamics. Simplifications are possible under thin layer, small viscous and electric Reynolds numbers assumptions. The characteristic times of the fluid motion process have been expressed.

JTAM, Sofia, vol. 20 Issue 4 pp. 046-051 (1989)

Development of Weak-Conductive Fluid Electro-Convection in a Free Surface Thin Layer. II. Velocity Field and Layer Thickness

D. Kulova-Nenova, S. Slavchev
Inst. Mech. Biomech. Bulg. Acad. Sci., Block 4

This part of the paper gives an analytic solution of the problem that has been formulated in the first one and concerns the development of weak-conductive viscous fluid electro-convection in a thin layer with deformable free surface. The problem is linear and this gives a possibility to consider an arbitrary type of the tangent electric tension which induces fluid motion. An equation is obtained of the layer thickness change in time and length. The equation itself is solved numerically when the specific potential type of the electric field is space-periodic. The established free surface form is determined analytically. The flow pictures have been followed from the motion start until its stabilization when the qualitative picture coincides with experimental observations of a flow in a layer. What has been calculated in the cases of space-periodic and constant tangen tensions in the surface maximum fluid velocity which depends on the electric potential.

JTAM, Sofia, vol. 20 Issue 4 pp. 052-060 (1989)

Calculation of Transitional Two-Dimensional Boundary Layer under the Influence of Free Stream Turbulence

D. Marinov, Z. Zapryanov
Inst. Mech. Biomech., Bulg. Acad. Sci., Block 4

Predictions of transitional two-dimensional boundary layer are presented. A low Reynolds turbulent number version of the k-ε turbulence model is used for simulating the turbulent transport. The calculation examples include various levels of free stream turbulence as well as a variety of flat plate boundary layers and boundary layers under pressure gradient (elliptic cylinder). The predictions are compared to experiments and a good agreement is obtained.

JTAM, Sofia, vol. 20 Issue 4 pp. 061-069 (1989), [Full Article]

On the Force Interaction in the Rotating Body Boundary Layer in Weak-Viscous Fluid

K. Shulev
High. Inst. Arch. Civ. Eng., Sofia

Inequality estimations are given for the active force interaction (inertial and mass forces) and the pressure gradient in the rotating body boundary layer in weak-viscous fluid. Viscous forces are considered to be neglectable. It is proved that an withstanding force acts in the boundary layer not allowing its tearing off the body. A criterion is proposed for the body flow over the fluid free surface. Experiments are carried out by rotating cone, sphere and body with variable meridian curvature. They confirm the criterion.

JTAM, Sofia, vol. 20 Issue 4 pp. 070-076 (1989)

Model of an Elastic-Visco-Plastic Body with Damage

A. Baltov, O. Minchev
Inst. Mech. Biomech., Bulg. Acad. Sci., Block 4

The damage of metals is a well known phenomenon and there are different mechano-mathematical models that describe this phenomenon at a different degree of approximation. What is proposed in the present work is a new model of an elastic-visco-plastic body with demage. It is based on an energetical approach to the inelastic deformable processes (visco-plastic deformation and microfracture) employing special energetical measures. It is considered the case when the microdamage is mainly isotropic and the voids can be taken spherical. This does not introduce orientation into the material structure and a deformation anisotropy does not develop. The model is applied to plates that have been submitted to external dynamic impacts, thus causing elastic-visco-plastic deformations with demage.

JTAM, Sofia, vol. 20 Issue 4 pp. 077-083 (1989), [Full Article]

A Method for Simulating of Non-Steady Thermoplastic Processes

N. Bontcheva
Inst. Mech. Biomech., Bulg. Acad. Sci., Block 4

A method for simulating non-steady thermoplastic processes is proposed. The method is based on a combination between the finite element method and thee fre point. method A. program system is built using the proposed method.

JTAM, Sofia, vol. 20 Issue 4 pp. 084-095 (1989), [Full Article]

Impulse Loading of a Beam with a Variable Cross-Section and on an Elastic Base

D. Karagyozova, E. Manoah
Inst. Mech. Biomech., Bulg. Acad. Sci., Block. 4

What is solved by a numerical method is the problem to determine the stressed-strained state of a beam with a variable cross-section and on an elastic base to which an instant initial velocity has been applied. The beam equilibrium equations account for the rotation inertia and the cutting forces. Three cases of boundary value conditions are considered: a beam which has been supported to an elastic base simply and which resists or does not resist to tearing off, a beam which has not been supported to a base and which resists to tearing off. Numerical results are obtained for the beam tensions and displacements in all the considered cases. The contact forces are obtained as well in the case of a base that does not resist to tearing off. The results are presented graphically.

JTAM, Sofia, vol. 20 Issue 4 pp. 096-106 (1989)

The Inertial Loading Problem in Dynamic Three-Point Bending of Prismatic Test Bodies

St. Vodenicharov
Sc. Ind. Union "Technology of Metals", Sofia

Analysis of the dynamic three-point bending is done on an energetic point of view. It is established that the inertial loading is connected with the initial steady state of the test body. Experiments are carried out by model test bodies and they prove the proposal that has been described.

JTAM, Sofia, vol. 20 Issue 4 pp. 107- (1989)