Journal of Theoretical and Applied Mechanics-Bulgaria has been selected for
coverage in Thomson Reuter’s products and services. Beginning with Vol. 46(1)
MAR 2016, this publication will be indexed and abstracted in
Emerging Sources Citation Index


AL . C HEREMENSKY

Institute of Mechanics, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria
[Received 25 November 2016. Accepted 08 October 2018]



IMPLEMENTATION OF THE AXIOMS OF COSSERAT–ZHILIN
SYSTEMS ON EXAMPLES OF THEIR MAIN TYPES

ABSTRACT: The differential equations of motion are derived for different types of Cosserat–Zhilin systems in the case where Stocks theorem is applicable. There are defined multiplicative groups which represent the measure of stress as a (well-defined) linear isotropic map of strain tensor or tensor of strain velocities for classical and polar continua in 2- and 3-dimensional cases.

KEY WORDS: Classical mechanics, continuum mechanics, mechanical measures, foundations of mechanics, constitutive equations, screw theory.

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HAMZA MADJID BERRABAH
Laboratoire Matériaux et Hydrologie, Centre Universitaire Ahmed Zabana
Relizane, Relizane, 48000, Algérie
[Received 17.09.2018. Accepted 18 February 2019]



THE INFLUENCE OF THE PIEZOELECTRIC EFFECT ON THE
ANALYSIS OF ELASTIC STRESSES FOR A COMPOSITE DISK
UNDER THE PARABOLIC DISTRIBUTION OF TEMPERATURE

ABSTRACT: In this paper, we studied the influence of the piezoelectric effect under the variation of the parabolic temperature, for this purpose, a thermoelastic composite disk reinforced by steel fibers is used for the analysis of the radial and tangential elastic thermal stresses. The solutions of the stresses were obtained analytically. In addition, a comparison between these expressions for different temperature values is calculated.

KEY WORDS :
piezoelectric, radial, temperature, tangential, elastic.


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YURII CHUI , PETRO MARTYNIUK,
MYKOLA KUZLO , OKSANA ULIANCHUK -MARTYNIUK
National University of Water and Environmental Engineering, Rivne, Ukraine
[Received 21 September 2018. Accepted 18 February 2019]




THE CONDITIONS OF CONJUGATION IN THE TASKS OF
MOISTURE TRANSFER ON A THIN CLAY INCLUSION TAKING
INTO ACCOUNT SALT SALUTIONS AND TEMPERATURE


ABSTRACT: The processes of non-isothermal moisture transfer of single-component chemical solutions in the porous environment containing thin semi-permeable clay inclusions have been considered. The conjugation conditions for the functions of humidity, salt concentration and temperature have been modified. The modification has been based on taking into account the dependences of the parameters of the porous medium on the physico-chemical processes and osmotic flows.

KEY WORDS :
moisture, salt solutions, temperature, porous medium, semipermeable membrane, conjugation condition, osmosis.
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PEYMAN MIANJI , EHSAN SEYEDI HOSSEININIA
Department of Civil Engineering, Ferdowsi University of Mashhad, Azadi Sq.,
Mashhad, Iran
[Received 09 October 2017. Accepted 18 February 2019]



A MODIFIED METHOD FOR MODELLING OF SPREAD
FOOTING UNDER UNIFORM DISTRIBUTED LOAD USING
WINKLER’S MODEL

ABSTRACT: Recent developments and advancements in soil models and computer programs failed to prevent structural engineering to use one the most elementary theories in modeling of the soil-structure interaction, i.e. Winkler’s model. Superseding the soil with all its complexity with a series of uncoupled, independent springs whose stiffness known as the modulus of subgrade reaction (Ks), imposes many non-avoidable errors to the model. In the first two parts of the paper, the impact of soilfoundation system stiffness on the Ks distribution alongside the precision of the theoretical relations for Ks estimation are investigated as the basis for the proposed dividing technique presented in the rest of the article.

KEY WORDS :
Winkler’s model; modulus of subgrade reaction; soil-foundation system rigidity; experimental and theoretical relation of Ks estimation; dividing technique.

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SHANKAR SEHGAL , HARMESH KUMAR
Mechanical Engineering, UIET, Panjab University, Chandigarh,160014 India
[Received 02 January 2018. Accepted 18 February 2019]



EXPERIMENTAL DAMAGE IDENTIFICATION BY APPLYING
STRUCTURAL DYNAMIC MODEL UPDATING

ABSTRACT: In this paper, structural dynamic model updating has been utilized in experimentally evaluating the extent of damage at six locations of a damaged cantilever beam structure. Six elements of the beam had lateral cuts. These cuts resulted in unknown reductions in flexural rigidity parameters. These parameters were taken as updating parameters and the reductions in these parameters were identified through dynamic model updating and evaluated to be 54.49, 100.09, 79.63, 82.17, 45.60 and 27.40 Nm2 . Updated finite element model of the structure was created by incorporating reduced flexural rigidity parameters. Dynamic results of updated model showed that total absolute error in prediction of natural frequencies was reduced by 98.36%, which confirmed accurate identification of flexural rigidity parameters and hence damage extents in the beam.

KEY WORDS :
  damage identification; structural dynamics; model updating; response surfaces; modal testing.


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ALEXANDER POPOV 1, GEORGY DOBREV 2
1 Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev St., Bl. 4, 1113, Sofia, Bulgaria
2  Institute of Metal Science, Equipment and Technologies, Bulgarian Academy of Sciences, Shipchenski prohod St. 67, 1574, Sofia, Bulgaria
[Received 25 July 2018. Accepted 18 February 2019]



EVALUATION OF THE LAME’S CONSTANTS IN THEORY OF
ELASTICITY BY ULTRASONIC MEASURMENTS


ABSTRACT: The evaluation of Lame’s constants (λ; μ) is taken in theory of elasticity. An interest in practice is the possibility of non-destructive evaluation (NDE) of (λ; μ) by measuring ultrasound wave propagation longitudinal and transversal velocities (VL ; VT ) with unilateral access to the test sample.

KEY WORDS : Lame’s constants; ultrasonic velocities.


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XU WANG1 , P ETER S CHIAVONE 2
1 School of Mechanical and Power Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
2 Department of Mechanical Engineering, University of Alberta, 10-203 Donadeo Innovation Centre for Engineering, Edmonton, Alberta, T6G 1H9, Canada
[Received 06 November 2018. Accepted: 18 February 2019]



ESHELBY’S INCLUSION AND SCREW DISLOCATION
PROBLEMS FOR A THREE-PHASE PIEZOELECTRIC LAMINATE


ABSTRACT: We propose a simple yet effective method based essentially on analytic continuation to derive analytical solutions for a screw dislocation or a two-dimensional Eshelby inclusion of arbitrary shape in a three-phase piezo-electric laminate composed of two semi-infinite piezoelectric media bonded together via an intermediate piezoelectric layer of finite thickness. The screw dislocation or the Eshelby inclusion can be located either in the upper semi-infinite piezoelectric medium or in the intermediate piezoelectric layer. Elegant expressions for the image force acting on the piezoelectric screw dislocation are presented and compared with existing results. We also observe some very
interesting properties of the solutions obtained.


KEY WORDS : Three-phase piezoelectric laminate, screw dislocation, Eshelby inclusion, image force, analytic continuation.

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SIMEON KARPUZOV1, GERGO MITOV 2, ASSEN SHULEV1
1 Institute of Mechanics, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria
2 Steiner Landstrae 124 A-3500, Krems-Stein, Austria
[Received 17 August 2018. Accepted 18 February 2019]



SURFACE ROUGHNESS ESTIMATION OF DENTAL MATERIALS
USING SPECKLE CONTRAST


ABSTRACT: In this paper a simple technique for surface roughness estimation of composite dental material samples widely used in modern stomatology is presented. The proposed method is easily applicable and based on statistical properties of diffusely scattered laser light. The main challenge we addressed was the specific structural and optical properties, as well as the complex geometric shapes of real dental restorations. A relation between surface roughness and speckle contrast, used in the presented method, is verified.
KEY WORDS : speckle, roughness, contrast, light scattering.

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TONY BOIADJIEV1 , GEORGE BOIADJIEV2, KAMEN DELCHEV3,
IVAN CHAVDAROV 4, RUMEN KASTELOV5
1  Institute of Information and Communication Technologies, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria
2 Mathematics and Informatics, Sofia University, Sofia, 1164, Bulgaria
3 Institute of Mechanics, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria
4 Institute of System Engineering and Robotics, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria
5 Orthopaedic and Trauma Clinical Centre of Ministry of Interior, Sofia, 1606, Bulgaria

[Received 11 October 2018. Accepted: 18 February 2019]



AUTOMATIC BONE DRILLING IN HIP FRACTURES
OSTEOSYNTHESIS


ABSTRACT: This paper presents an investigation of automatic bone drilling application in osteosynthesis of hip fractures. The real hip fractures osteosynthesis includes bone drilling from hip femur through the neck (along its axis) and the hip head to its far cortex avoiding joint penetration by hip head far cortex registration. The automatic execution of such a task by the Orthopedic bone Drilling Robot ”ODRO” is the main contribution of this paper. A femoral head cortex registration algorithm is proposed for automatic drilling the proximal femur (hip joint). Experiments are provided and graphs illustrating the results are presented and commented to validate them.

KEY WORDS : orthopedic surgery, bone drilling, handheld robot.

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