Journal of Theoretical and Applied Mechanics, Sofia, vol. 50 Issue 3 (2020)

Table of contents



NONLINEAR DOUBLE DIFFUSIVE CONVECTION FROM A RADIATIVE SLENDER PARABOLOID IN A NON-DARCY POROUS MEDIUM

Rishi Raj Kairi1, Ch. Ramreddy2
1Mathematics Department, Cooch Behar Panchanan Barma University, Cooch Behar-736101, India
2Mathematics Department, National Institute of Technology Warangal-506004, India


This paper describes the nonlinear double diffusive convective phenomena of a Ostwald-de Waele power-law fluid from a radiative slender paraboloid in a non-Darcy porous medium. A suitable set of similarity transformations is utilized to convert the set of nonlinear partial differential equations to the set of nonlinear ordinary differential equations and hence, the resultant equations are solved numerically. The significance of various flow influencing parameters on dimensionless velocity, concentration, temperature, and heat and mass transfer rates, is elaborated graphically in detail.

JTAM, Sofia, vol. 50 Issue 3 pp. 205-221 (2020), [Full Article]




FRACTIONAL ORDER THEORY OF THERMAL STRESSES IN A TWO DIMENSIONAL TRANSVERSELY ISOTROPIC MAGNETO THERMOELASTIC MATERIAL

Parveen Lata, Iqbal Kaur
Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India


A mathematical model for homogeneous transversely isotropic magneto-thermoelastic (HTIMT) material and fractional order theory (FOT) of thermal stresses due to ramp type heat and with hall current effect is formulated. To solve the field equations, Fourier and Laplace transforms are used. The mathematical expressions of components of displacement, temperature, current density and stress are solved in the transformed domain and then obtained in physical domain using transform inversion techniques. The fractional order parameter by considering various cases of weak, normal and strong conductivity are represented graphically.

JTAM, Sofia, vol. 50 Issue 3 pp. 222-237 (2020), [Full Article]




WIND TURBINE COMPOSITE BLADE: FRACTURE MECHANICS ASSESSMENT

Waleed Ahmed
Mechanical Engineering Department, United Arab Emirates University, Al Ain, Abu Dhabi, UAE


The study aims to investigate a wind turbine composite blade subjected to wind loading forces. Linear elastic fracture mechanics principle was used to evaluate the blade with a deteriorated adhesive layer through the estimation stress intensity factor of an edge crack at the adhesive layer. The opening and sliding mode of SIF were predicted and discussed. Two dimensional, plane strain FE modeling was adopted in the study. Interfacial stresses along the bonding line of the composite blade were estimated as well. A parametric study was conducted to assess the influence of the adhesive, mechanical properties on the levels, and the distribution of the stresses along the interfacial bonding line of the composite blade for both intact and fractured blade.

JTAM, Sofia, vol. 50 Issue 3 pp. 238-258 (2020), [Full Article]




VIBRATIONAL ANALYSIS OF GLASS/CARBON FIBER REINFORCED HYBRID LAMINATE COMPOSITES

Kamal Singh1, Naman Jain2, Jitendra Bhaskar1
1Mechanical Engineering Department, Harcourt Butler Technical University, Kanpur India
2Mechanical Engineering Department, Meerut Institute of Engineering and Technology, Meerut, India


In present work fabrication of glass/carbon fiber hybrid composite had been done to tailor the properties of such materials to suit specific demand. The characterization of the hybrid composites had been done on the basic of vibrational analysis. Natural frequency, damping ratio, logarithmic response, and flexural stiffness of hybrid composites had been determined through experimental and numerical technique method. ABAQUS software was used to determine the natural frequency of hybrid composite and results obtained were also validated with experimental work. The result indicated that the quantity, stacking sequence and damping ratio of the carbon-glass fiber affected the natural frequency of hybrid composite. The stacking sequence of the carbon layer gave a significant result to the dynamic characteristic of the carbon-glass fiber hybrid composite. Validation of the natural frequency of composite laminates was also done using ABAQUS software. Result shows that hybrid laminate composites, which have higher natural frequency, have higher stiffness and good strength to absorb load. Whereas, composites, which have low natural frequency have low flexural strength but high damping ratio.

JTAM, Sofia, vol. 50 Issue 3 pp. 259-277 (2020), [Full Article]




HUMAN-INDUCED VIBRATIONS ON FOOTBRIDGES. CURRENT CODES OF PRACTICE — CASE STUDY

Krumka Kasapova, Dobromir Dinev
University of Architecture, Civil Engineering and Geodesy; 1 Smirnenski Blvd., 1046, Sofia, Bulgaria


Although not vulnerable regarding structural capacity and integrity in most cases, lightweight structures may exhibit excessive vibration levels. When regarding public buildings or structures which may be exposed to the excitation of a significant number of people, for instance concert halls, grandstands, long-span floors, staircases in malls etc. the issue concerning vibrations induced by humans becomes an important part of the overall structural design process.
The current article explores the dynamic behaviour of Eeklo footbridge. Calculations of vertical acceleration levels according to the current codes are implemented. The result are summarized and analyzed in details.

JTAM, Sofia, vol. 50 Issue 3 pp. 278-291 (2020), [Full Article]




ON THE STABILITY OF COUPLED OSCILLATIONS OF THE ELASTIC BOTTOM OF A RIGID RECTANGULAR CHANNEL AND IDEAL LIQUID

Yuri Kononov1, Alekcandr Lymar2
1Institute of applied mathematics and mechanics, National Academy of Sciences of Ukraine, Sloviansk, Ukraine
2Nikolaev National Agrarian University, Nikolaev, Ukraine


Normal oscillations of the elastic bottom of a rigid rectangular duct with an ideal non-compressive fluid, which completely fills it, were investigated. The elastic bottom is a membrane. It is shown that the frequency equation is divided into two equations describing symmetric (even) and antisymmetric (odd) frequencies, and can be written in a single form for these frequencies. For even and odd frequencies, an approximate formula is obtained, from which approximate conditions follow for stability of coupled vibrations of an elastic basis and a fluid. These conditions are independent of the liquid height and the membrane mass. Exact stability conditions that coincide with hydrostatic conditions are derived. It is shown that the approximate value of the critical tension for asymmetric frequencies is 4/5 times lower, and for symmetric frequencies, it is 0.818 times lower.

JTAM, Sofia, vol. 50 Issue 3 pp. 292-303 (2020), [Full Article]