JOURNAL OF THEORETICAL AND APPLIED MECHANICS

Volume 29 Number 3 1999
CONTENTS




P. Kiriazov, K. Delchev.

Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria,
e-mail: dors@bgcict.acad.bg

A Robust Algorithm for Parameter Identification of Robotic Manipulators

Abstract. A simple deterministic identification procedure for multi-degree-of-freedom robotic manipulators is presented. The procedure is always convergent in despite of the measurement noise and unmodelled dynamics. Open-loop control functions are used and only angular displacements are measured at the beginning of the test movements. With known model mismatch, a precise error analysis can be done for the identified parameters. The identification method is applied to a full dynamic model of a SCARA-type robot.

Key words: robotic manipulators, dynamic modelling, parameter identification, two-degree-of-freedom tests.



 V. Abadjiev, P. Gospodinov, Hr. Hristov.

Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria,
gospodin@bgcict.acad.bg

On the Mathematical Modelling and Computer Simulation of a Car Crash

Abstract. The present study offers mathematical modelling of a car crash where the vehicle loses several times contact with the road and the road facilities. Mathematical models describing the car complex trajectory during the car crash are obtained on the basis of the general laws of solid mechanics and the laws of a body motion into a fluid. The authors perform a numerical simulation of the car crash and realize its scenario using the models proposed. The results obtained enable to analyze the vehicle behaviour during the accident. The models and algorithms proposed can be used for the analysis of other car crash or of separate car crash elements.

Key words: mathematical modelling, car crash, car dynamics



A. Ivanov.

Higher Military School of Transport,
158, Geo Milev Str., 1115 Sofia, Bulgaria
anastas@mail.vvtu.bg

Joined Forced Vibrations of Railway Vehicle and Bridge

Abstract. In this paper we analyze the joined forced vibrations of the system ``Vehicle-Bridge'' when the vehicle is moved on the bridge. Discrete dynamic models with finite number degree of freedom are used. A concrete numerical solution is made. The investigation could be used for dynamic analysis and synthesis of the perspective constructions high velocity railway vehicles and railway bridges, especially lightened military temporary bridges.

Key words: multi-body systems, vibrations, railway vehicle.



P. K. Kolev, V. S. Nedev

Higher Military School of Transport,
158, Geo Milev Str., 1115 Sofia, Bulgaria

Dynamics of Regional Movement of a Robot Manipulator with Distributed Parameters and Hydraulic Drive of the Module for Vertical Translation

Abstract. Subject of present research is the relationship between regional movement and micro-ones of a robot with hydraulic drive of the module for vertical translation in cylindrical co-ordinates. A mechanical-mathematical modelling in conditions of autonomy of the system with distributed mass and elastic parameters is represented. The natural frequencies, weight coefficients, normal functions, as well as law of disturbed motion are defined.

Key words: mechanical-mathematical modelling, robot manipulator, distributed parameters.



B. Pavlov, B. Kazakov, G. Jaigarov.

Institute of Water Problems, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 2, 1113 Sofia, Bulgaria

Interaction between Fluid and a Boundary Formed by Cohesionless Rigid Particles
Downstream Hydraulic Structures

Abstract. A two dimensional problem for determination of local river scour downstream of hydraulic structures with stilling basins and aprons is investigated. A mathematical model is developed by means of statistical methods of the theory of experimental design, that model predicting the main characteristics of local bed scour with a reliability of 95%. When the discharge and the main diameter of the river bed cohesionless particles are constant by a proper choice of the length of the apron the maximum scour depth and the distance from the end of the apron to the section with the maximum scour depth could be varied. In that way the process of local river bed scour downstream of the stilling basin can be controlled.

Key words: river bed deformation, hydraulic structures.



J. D. Nikolova.

University ``Prof.Dr.Assen Zlatarov'' -- Bourgas

Ultrafiltration in Ring-Shaped Channel and Removal of Superconcentrate Therefrom

Abstract. Ultrafiltration process with continuous removal of the superconcentrate from the existing concentration zones is performed using a channel with ring-shaped cross-section at laminar flow. Acetatecellulose tubular membranes with inner diameter of 12.5 mm and cylindrical inserts with diameter 5.6 mm are used. Relatively higher throughput is determined than in the case without superconcentrate receptacle.

Key words: ultrafiltration process, concentration polarization, superconcentrate receptacle, lubricant emulsions.



T. Karamanski.

University of Architecture, Civil Engineering and Geodesy,
1, Hr.Smirnenski Str., 1421 Sofia, Bulgaria,
e-mail: tdk_fce@uacg.acad.bg

Common Engineering Theory of the Thin-Walled Beams

Abstract. A new theory of the thin-walled beams and similar structures is developed. The thin-walled beam is treated as an assemblage of strips. The cross-section of the beam could be open, closed or mixed. The strips may have changeable thickness, different length, openings. The interaction of the strips is realised by means of co-ordination of their displacements across the beam axis and equating the longitudinal displacements of the neighbouring strips. Unknown values are: the displacements perpendicular to the longitudinal axis, the rotation around this axis and the longitudinal distributed and concentrated forces between the strips. For every strip the well known beam theory is applied. The strains related to the normal stresses and also with the shear stresses are taken into account. A formula is given for calculation of the cross-section characteristics related to the shear strains. The model ``thin-walled beam'' is suitable for example for analysis of the system of shear walls in a building, bearing the vertical forces and also the horizontal forces caused by wind or earthquakes. The data input, the static and dynamic analysis of a thin-walled beam or of a system of shear walls and also the dimensioning of strips could be easily performed by means of the program system STADYPS.

Key words: thin-walled beams, shear walls, Finite Element Method.



 F. Sidoroff,  K. Hadjov.

F. Sidoroff
Ecole Centrale de Lyon, Dep. Mecanique des solides, LTDS URA C.N.R.S 855,
36, av. Guy de Collongue B.P. 163, 69131 ECULLY cedex France
K. Hadjov
University of Chemical Technology and Metallurgy,
St.Kl.Ohridski Str., 1756 Sofia, Bulgaria,
e-mail: vega@ttm.bg

Anisotropic Elasticity for Fibre Reinforced Materials

Abstract. The work which is presented here is devoted to a mechanical analysis of the behaviour of a fibre reinforced composite material whose phases are elastic. The matrix is isotropic and the fibres are transverse isotropic with arbitrary directions. The localisation and compliance matrix in a general case are obtained. Lamé's coefficients of quasi-isotropic fibre distribution are given. The plane case reinforcement are examined. The compliance matrix components in the unidirectional case are compared with other theoretical results and experiments. We have used Euclidean tensors in an orthonormed basis everywhere.

Key words: homogenisation, anisotropy, composite materials.



R. Raikova.

Centre of Biomedical Engineering, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 105, 1113 Sofia, Bulgaria
e-mail: rosir@bgcict.acad.bg

Indeterminate Problems in Biomechanics: Which Weight Factors Can Be Considered in the Objective Function and Why?

Abstract. The paper is devoted to the indeterminate problems in biomechanics and their solving using optimisation methods. The main question is: what type of mathematical function has to be used and what is its physiological meaning. Assuming that the optimisation criterion has the form åci.Fi2 (ci is an unknown weight factor at the i-th muscle), different sets of ci may be investigated aiming to predict physiologically possible solutions. It is shown using a planar, 3DOF model of the human upper limb including ten muscles that: ci at muscles from one synergistic group have one and the same sign and this sign is opposite to the sign of ci at muscles from respective antagonistic group; the value and the sign of ci depend essentially on the value and direction of the net external moments in the joints.

Key words: biomechanics, upper human limb, modelling optimisation, muscle force.



 M. Koudelka, R.  Zák, M. Talanda, L. Mitutsova.

Measurement of Force in Biomechanics oM. Koudelka
Institute of Materials and Machine Mechanics, SAS,
Ra cianská 75, P.O.Box 95, 830 08 Bratislava, Slovakia
R. Zák
Iodine Spa, 980 43 C\' z, Slovakia
M. Talanda
Faculty of Electronics and Informatics, Slovak Technical University,
Ilkovi cova 3, 812 19 Bratislava, Slovakia
L. Mitutsova
Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bontchev Str., Bl. 4, 1113 Sofia, Bulgaria

MEASUREMENT OF FORCE IN BIOMECHANICS OF LOCOMOTORY APPARATUS

Abstract. Measurement is an objective method of the biomechanical evaluation of locomotion apparatus of a man from the point of view of its objective activity. Significant criterion of the function of locomotion apparatus is the force knowledge of which may serve to judge the correctness of the function of the parts of locomotion apparatus, namely upper and lower extremities. Time course of the force at the exerted activity may give e.g. picture about the measure of compensation of eventual damage by organism and on the other hand may give a picture about the result of cure or rehabilitation.

Because of specific requirements on the force sensors authors developed their own electromechanical sensor of force. In a paper they give an information about some of its properties and mention the examples of its realisation not only in the area of biomechanics of locomotion apparatus but also in the area of its industrial realisation.

Key words: electromechanical sensor of force, optomember, shading of infrared light flow, elastic member, gripping of a hand, time course of force.



N. Kounov,  K. Prodanov,  G. Mateev,  D. Petkanova.

Institute of Mechanics, Bulgarian Academy of Sciences,
Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria,
e-mail: kavarj@imech.imbm.acad.bg
G. Mateev
Department of Dermatology and Venerology, Medical University,
5, G. Sofiyski Str., Sofia, Bulgaria

The Use of Erythrocyte Sedimentation Curves in Dermatology - I. Psoriasis vulgaris

Abstract. A new theory of the thin-walled beams and similar structures is developed. The thin-walled beam is treated as an assemblage of strips. The cross-section of the beam could be open, closed or mixed. The strips may have changeable thickness, different length, openings. The interaction of the strips is realised by means of co-ordination of their displacements across the beam axis and equating the longitudinal displacements of the neighbouring strips. Unknown values are: the displacements perpendicular to the longitudinal axis, the rotation around this axis and the longitudinal distributed and concentrated forces between the strips. For every strip the well known beam theory is applied. The strains related to the normal stresses and also with the shear stresses are taken into account. A formula is given for calculation of the cross-section characteristics related to the shear strains. The model ``thin-walled beam'' is suitable for example for analysis of the system of shear walls in a building, bearing the vertical forces and also the horizontal forces caused by wind or earthquakes. The data input, the static and dynamic analysis of a thin-walled beam or of a system of shear walls and also the dimensioning of strips could be easily performed by means of the program system STADYPS.

Key words: thin-walled beams, shear walls, Finite Element Method.



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