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. 53 Issue 2 (2023) |
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DELAMINATION OF MULTILAYERED BEAMS WITH NON-LINEAR VISCOELASTIC BEHAVIOUR UNDER STRAINS OF STEP-LIKE VARYING VELOCITY V. Rizov1, H. Altenbach2 1Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky blvd. 1046 Sofia, Bulgaria 2Lehrstuhl für Technische Mechanik, Fakultät für Maschinenbau, Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Deutschland
The present paper deals with delamination
analysis of a multilayered inhomogeneous beam structure that exhibits
non-linear viscoelastic behaviour under strains whose velocity varies
step-like with time. There are two delaminations in the beam. The left-hand
delamination crack arm is subjected to bending so as the velocity of angle
of rotation of this crack arm varies step-like with time. A non-linear
viscoelastic model with a spring and two dashpots treats the beam mechanical
behaviour. Solutions of the strain energy release rate are derived for both
delaminations. A parametric investigation of delamination in the beam is
carried-out by using the solutions.
JTAM, Sofia, vol. 53 Issue 2 pp. 099-115 (2023), [Full Article]
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SPATIAL BEHAVIOUR IN MICROSTRETCH ELASTICITY WITH MASS AND THERMAL DIFFUSION Adina Chirilă, Marin Marin Department of Mathematics and Computer Science, Transilvania University of Braşov, Romania
We analyse the spatial behaviour of diffusive microstretch thermoelasticity with
microconcentrations and microtemperatures
in the linear, anisotropic and non-centro-symmetric case.
We define a function with a weight depending on time that characterizes the principal
characteristics of the model, then study its properties and derive a
differential inequality. Then we obtain an exponential spatial decay
that is independent of time and is valid for unbounded bodies.
JTAM, Sofia, vol. 53 Issue 2 pp. 116-135 (2023), [Full Article]
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CREEP CHARACTERISTICS OF POLYESTER COMPOSITES WITH NATURAL FIBER REINFORCEMENT (HORSE HAIR/SHEEP WOOL) Ali A. Battawi, Balsam H. Abed Middle Technical University, Technical Engineering College-Baghdad, Iraq
In this paper, experimental, theoretical, and numerical
simulations were used to investigate the effect of adding natural fiber
(Horsehair/Sheep wool) with varied weight ratios to polyester composite
material on creep behavior at room temperature and constant load. A
hand-layup technique was used to create polyester resin, and the test
specimens were produced following the standards (ASTM). The results showed
an improvement in creep behavior of polyester composites reinforced with
natural fibers when compare with non-reinforced polyester, hence the amount
of maximum strain was reduced to 74.64% when sheep wool was added at a
weight ratio of 0.8%, and 71.114% when horsehair was added at the same
weight ratio. The experimental results were verified theoretically and
numerically using ANSYS Mechanical APDL software 15, the results demonstrate
that they are in good agreement.
JTAM, Sofia, vol. 53 Issue 2 pp. 136-151 (2023), [Full Article]
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PROPERTIES OF A NOISE BARRIER WITH CONTROLLED DIFFRACTION AT THE EDGE V.T. Grinchenko1, I.V. Vovk1, V.O. Husak2, V.T. Matsypura2 1Institute of Hydromechanic of NAS Ukraine, National Academy of Sciences of Ukraine, Kyiv, 01030, Ukraine 2Faculty of Mechanics and Mathematics, Taras Shevchenko National University of Kyiv, Kyiv, 01033, Ukraine
The paper considers the problem of sound scattering on a
classical noise barrier and a noise barrier with a resonator. A rigorous
solution is obtained. It is shown that the use of the root mean square
approximation and the conjugation by points of fields in the problem of
sound scattering on a classical barrier gives a good coincidence of the
calculated values of fields. It is shown that for frequencies above the
resonance one exists a band in which there is a dip in the frequency
response of the integral criterion of the barrier. All this illustrates the
advantage of the barrier with the resonator.
JTAM, Sofia, vol. 53 Issue 2 pp. 152-165 (2023), [Full Article]
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THERMAL STABILITY ANALYSIS OF FUNCTIONALLY GRADED NANO BEAMS BASED ON HIGHER ORDER SHEAR DEFORMATION THEORY WITH TWO VARIABLES Zemri Amine1, Berrabah Hamza Madjid2 1Department of Civil Engineering, University of Relizane, 48000, Algeria 2Department of Civil Engineering, Mechanical Engineering Materials and Structures Laboratory, University of Relizane, 48000, Algeria
In this work, the thermal buckling of nano functionally
graded beams is investigated using nonlocal higher order deformation shear
theory with two variables. The variation of properties of FG material is
made through the thickness using a power law and exponential form. Governing
equations are derived using the principle of virtual work. The temperature
variation is assumed to be uniform. The critical buckling temperature is
calculated for various boundary conditions of the beam: simply supported and
clamped-clamped beams. The nonlocal parameter, power law index, slenderness
radio and boundary conditions on the critical buckling temperature of the FG
nano beams are analyzed.
JTAM, Sofia, vol. 53 Issue 2 pp. 166-181 (2023), [Full Article]
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SINGLE SPERMATOZOON HEAD TRACKING FOR ROBOTIC INTRACYTOPLASMIC SPERM INJECTION (ICSI) Tihomir Tiankov, Assen Shulev, Dimitar Trifonov Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl. 4, 1113, Sofia, Bulgaria
In this paper, a new approach for autonomous single spermatozoon
tracking has been proposed. During the presented approach, there is no need
to track low contrast objects (spermatozoon tail). The most important part
is the motion trajectory tracking of the spermatozoon head. The effective
sperm head tracking has been realized using image processing and sperm head
shape recognition (as a sphere). Without following the sperm tails – moving
with very high dynamics, the software application is faster working. The
tracking algorithm has been realized in a square Sperm Head Region of
Interest (SHROI), with a size of 100×100 pixels. The developed software
application is compatible with almost all digital cameras available on the
market.
JTAM, Sofia, vol. 53 Issue 2 pp. 182-199 (2023), [Full Article]
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