BULGARIAN ACADEMY OF SCIENCES NATIONAL COMMITTEE OF THEORETICAL AND APPLIED MECHANICS Journal of Theoretical and Applied Mechanics
Print ISSN: 0861-6663 Online ISSN: 1314-8710
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JTAM, Sofia, vol. 30 Issue 1 (2000) |
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Rate Kinematics of a Hybrid Type Manipulation System T. Tanev Central Laboratory of Mechatronics and Instrumentation, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 1, 1113 Sofia, Bulgaria
The paper presents an approach to solving the inverse velocity problem for a hybrid manipulation system. The
proposed approach offers an efficient alternative to using the inverse Jacobian. The considered manipulation system consists of
two variable-geometry modules, which are serially connected. An numerical example and a simulation of the kinematic solutions
derived in this paper have been performed.
JTAM, Sofia, vol. 30 Issue 1 pp. 01 (2000)
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An Investigation of the Robot Service Coefficient During the Manipulation System Calibration P. Raikov, N. Valchkova, D. Denev Central Laboratory of Mechatronics and Instrumentation, Bulgarian Academy of Sciences, Acad.G. Bonchev Str., Bl. 1, 1113 Sofia, Bulgaria
An approach for calibration of the joint-axes orientation of the robots by calculating of the service coefficient is
proposed. The computational scheme uses a ``grid-based'' numerical method for estimation of the working area of multilink
mechanisms.
The proposed approach is applied using the geometrical parameters of two commercially available in Bulgaria robots and the
results of these computations are presented.
JTAM, Sofia, vol. 30 Issue 1 pp. 02 (2000)
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Sliding Velocity Vectors Field in Case of Spatial Rack Mechanisms V. Abadjiev, E. Abadjieva Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria
This work studies spatial rack mechanisms transforming rotation into translation. The transformation is realized by the
theoretically conjugate surfaces. The created mathematical model describes the sliding velocity vectors field and the axoids of
the rack sets. The defined kinematic characteristics have a direct application to the synthesis of these mechanisms.
JTAM, Sofia, vol. 30 Issue 1 pp. 03 (2000)
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Chaotic Spatio-Temporal Structures in the Rayleigh-Benard Flow of a Rarefied Gas Vl. Roussinov1, S. Stefanov1, V. Yanitskii2 1Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G.Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria 2Computer Center, Russian Academy of Sciences, 40, Vavilova Str., 117967 Moscow, Russia
A permanent non-stationary and nonperiodical finite difference solution (known as ''strange attractor'') of the Rayleigh-Bénard problem of a rarefied gas has been found out for Knudsen number Kn = 0.001, Froude number Fr = 1.0 and temperature ratio Tc/Th = 0.1. The continuum model is based on the full Navier-Stokes equations for compressible viscous gas with viscosity and heat-transfer coefficients obtained from the first order Chapmen-Enskog approximation of the Boltzmann kinetic equation for low Knudsen number.
JTAM, Sofia, vol. 30 Issue 1 pp. 04 (2000)
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Velocimetry and Displacements Measurement by One-Beam Digital Speckle Interferometry Il. Roussev1, P. Koulev1, Evt. Toshev1, P. Bojanova1, T. Partalin2 1Institute of Mechanics, Bulgarian Academy of Sciences, Acad.G.Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria 2Faculty of Mathematics and Informatics, Sofia University ``St. Kl. Ochridski'', 5, J. Bourchier Str., 1164 Sofia, Bulgaria
The hardware and the software parts of a method for One-Beam Digital Speckle-Interferometry have been
developed. The possibilities of the technique are experimentally confirmed in the cases of: digital translation of synthesised
speckle pattern, real rigid body translation and rotation, rubber-plate deformation and two-dimensional sedimentation in
Hele-Show cell of marble-sendand quartz-send particles suspension in mineral oil
JTAM, Sofia, vol. 30 Issue 1 pp. 05 (2000)
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Nonlinear Behaviour of Reinforced Concrete Shear Wall Under Seismic Excitation D. Stefanov Central Laboratory for Seismic Mechanics and Earthquake Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl.\ 3, 1113 Sofia, Bulgaria
The reinforced concrete shear walls are the primary bearing elements in building structures in nuclear power plants.
This paper investigates the nonlinear behaviour of a shear wall, experimentally tested on shaking table. The applied loading
permits to comprehend the response at levels ranging from the elastic state to the elasto-plastic ultimate state. A finite element
model is used, taking into account the nonlinear behaviour of the materials - concrete and steel. Comparisons between
analytical and experimental results are made.
JTAM, Sofia, vol. 30 Issue 1 pp. 06 (2000)
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Examination of the Structure and Mechanical Behaviour of Constructional Foamed and Recycled Thermoplastic Composites (CFRTC) N. L. Piperov Institute of Metal Science, Bulgarian Academy of Sciences, 67, Shipchenski Prohod Str., 1574 Sofia, Bulgaria
Some structural and constructional-technological peculiarities of the recycling and the re-use of composite foamed
thermoplastic products are studied in this paper. The experimental and theoretical analysis carried out of structure forming
under the conditions of the method of gas counter-pressure injection moulding, of the zones with plastic leaking at the
boundaries of dispersed particles and gas bubbles, of the formation and accumulation of defects in the interphase marginal
zones of CFRTC enables the search for correlation with the technological and constructional parameters of the system
``thermoplastic matrix-dispersed filler-gas phase'' by predicting its functional fitness and possibilities over a wide
composite-technological and operating range.
JTAM, Sofia, vol. 30 Issue 1 pp. 07 (2000)
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Modelling the Temperature Condition in the Ends of Long Cylindrical Forgings during Hot Plastic Deformation in a Radial Forging Machine T. Troufkin, V. Evlogieva Institute of Metal Science, Bulgarian Academy of Sciences, 67, Shipchenski prohod Str., 1574 Sofia, Bulgaria
Well-known analytical formulae of relative dimensionless temperatures in infinite cylinder and infinite plate the
intersection of which forms a cylinder of finite dimensions are used. In the computer calculation the method of consecutive
intervals is applied and it is operated with weighted average values for the radii, the thickness of the two half plates and the
coefficients of thermal conductivity and heat transfer of the hot metal. A calculation experiment is carried out by means of the
computer model developed. The difference in the cooling of the ends in comparison with the central part of the forging is
quantitatively determined.
JTAM, Sofia, vol. 30 Issue 1 pp. 08 (2000)
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Investigation of the Mechanical and Nuclear Magnetic Resonance Properties of Human Vascular Walls in Vitro S. I. Petkov Technical University of Gabrovo
The purpose of the present study is to find a correlation between the visco-elastic and proton nuclear magnetic
resonance (H1 NMR) properties aiming to characterise the stress state of the vascular wall by non-invasive method. In order to
obtain quantitative relationships between mechanical characteristics of large human vascular walls of different anatomic
localisation both static and dynamic methods were applied. The results obtained were compared with data from H1 NMR
measurements at 4 MHz and 60 MHz. Typical changes of line-shape have been observed by hystologicaly controlled selective
lysis for identification of collagen protons: the fast component of the signal disappears after collagen extract. On limited number
of samples from normal and aneurysmal aorta the technique was applied and significant correlation between the line-shape
second moment and mechanical characteristics was obtained.
JTAM, Sofia, vol. 30 Issue 1 pp. 09 (2000)
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