Journal of Theoretical and Applied Mechanics, Sofia, Accepted Papers



OFF-AXIS 2D DISPLACEMENT FIELDS EVALUATION BY DIGITAL IMAGE CORRELATION USING MARKERS

Georgi Stoilov, Dessislava Pashkouleva, Vassil Kavardzhikov
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria


ABSTRACT: Digital image correlation is a mathematical technique which can be used successfully for evaluation displacements and deformations of large engineering components. Compared to traditional contact measurements, digital image correlation allows full-field deformation information to be obtained by non-contact procedure. Herein, we propose a method to improve the accuracy in evaluation of two dimensional displacement fields by introducing markers, which are used during the following digital image correlation analysis. The effectiveness of the proposed method is illustrated in processing of displacement fields on the surface of a wooden wall, subjected to cyclic loading. The results are in good agreement (less than 1%) with the data obtained by linear voltage differential transformer sensors. Experiments show that the use of markers is a perspective way to improve the accuracy of a digital image correlation method, and to improve its applicability in structural monitoring.

JTAM, Sofia , [Full Article]




A STEADY-STATE HEAT CONDUCTION PROBLEM IN A COMPOSITE SOLID SQUARE TWO-DIMENSIONAL BODY

István Ecsedi, Attila Baksa
Institute of Applied Mechanics, University of Miskolc, H-3515 Miskolc, Miskolc-Egyetemváros, Hungary


ABSTRACT: Studying inhomogeneous structural elements is a very important task. Many studies deal with inhomogeneity of the type whose introduction into an originally homogeneous body does not change its physical fields belonging to the prescribed boundary conditions. This type of inhomogeneity is called neutral inhomogeneity. In the relevant literature, we find several examples of this, mainly in the mathematical theory of elasticity. A prime example is the Saint-Venant's torsion problem of prismatic bars. In the present paper a steady-state heat conduction problem is considered in a two-dimensional square-body. The Cartesian orthotropic solid square body consists of a circular inclusion. The circular inclusion is placed at the center of the square and it has two parts, a core and a coating component, both of which are cylindrically orthotropic. The paper deals with the determination of the thermal conductance of component bodies such that the temperature distribution in originally homogeneous Cartesian orthotropic solid square body does not change. All results of the paper is based on the Fourier theory of heat conduction in solid body.

JTAM, Sofia , [Full Article]




A DEVICE FOR IMPLEMENTATION OF THE FORCED OSCILLATION METHOD ON STRIP PREPARATIONS OF BIOLOGICAL TISSUES IN VITRO IN PROLONGED EXPERIMENTS

Mariya L. Antonova, Andreyan G. Georgiev, Tsvetalin T. Totev
Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria


ABSTRACT: The viscoelasticity of blood vessels determines their biomechanical behavior. The present work aims to develop and validate a new device modification for the forced oscillation method and to elaborate an experimental protocol for investigating the direct effect of opioids on the arterial wall in vitro in a prolonged experiment. The construction and software of a previously constructed device were improved and upgraded. A new photo optic recording system and Analog-To-Discrete conversion and recording scheme were developed. The elaborated experimental protocol allows an accumulative treatment with opioids while keeping the preparation vital. The total error of the measurement modules is less than 4.45%. The device ensures sufficient repeatability and precision in recording the response oscillations and estimating the viscoelastic characteristics of biological tissues.

JTAM, Sofia , [Full Article]