Issue 4
JTAM, Sofia, vol. 48 Issue 4 (2018)

MECHANICAL SYSTEMS OF COSSERAT–ZHILIN

Al. Cheremensky
Institute of Mechanics, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria


Mechanical systems of Cosserat–Zhilin are introduced as the main object of rational (non-relativistic) mechanics on the base of new notions of vector calculus — sliders and screw measures (bi-measures).

JTAM, Sofia, vol. 48 Issue 4 pp. 003-018 (2018), [Full Article]

REDUCTION OF DRAG OF SUV SIMILAR TO TATA SUMO USING VORTEX GENERATOR

Harsh Sardana, Mahavir Singh
Technosoft, Sec 16 Noida, UP-201301, India

The aim of this research paper is to reduce the drag of SUV by using a vortex generator and to calculate the pressure and turbulence profile across the vehicle. The Ahmed Reference Model is taken as a benchmark test. Computational fluid dynamics (CFD) simulation with and without vortex generator is performed at different velocities across the SUV similar to TATA Sumo. The performance of Vortex generator is analyzed at different velocities to obtain the particular velocity at which it will have the minimum value of drag. The end results are henceforth analyzed and a comparative study has been performed with the experimental data given by Gopal and Senthikumar on SUV. And finally it is found that the 10{\%} of drag reduction is achieved using vortex generator.

JTAM, Sofia, vol. 48 Issue 4 pp. 019-030 (2018), [Full Article]

STUDY OF RADIAL VIBRATIONS IN AN INFINITELY LONG FLUID-FILLED TRANSVERSELY ISOTROPIC THICK-WALLED HOLLOW COMPOSITE POROELASTIC CYLINDERS

Sandhyarani Bandari1, Anand Rao Jakkula1, Malla Reddy Perati2
1Department of Mathematics, Osmania University, Hyderabad 500007, India
2Department of Mathematics, Kakatiya University, Warangal 506009, India

In this paper, radial vibrations of an infinitely long fluid-filled transversely isotropic thick-walled hollow composite poroelastic cylinder are investigated in the framework of poroelasticity. The cylinder consists of two concentric cylindrical layers namely, core (inner one) and coating (outer one), each of which retains its own distinctive properties. A comparative study has been made between the thick-walled hollow composite poroelastic cylinder and that of fluid-filled one. Frequency is computed against the ratio between the thickness to inner radius of the composite cylinder at various anisotropic ratios. Another comparative study is made between the results of current case and that of isotropic case by making Young's modulus and Poisson ratio values of isotropic and that of transversely isotropic in the transverse direction equal. Numerical results are depicted graphically and then discussed.

JTAM, Sofia, vol. 48 Issue 4 pp. 031-044 (2018), [Full Article]

BUCKLING ANALYSIS OF ORTHOTROPIC THICK CYLINDRICAL SHELLS CONSIDERING GEOMETRICAL IMPERFECTION USING DIFFERENTIAL QUADRATURE METHOD (DQM)

A. Maleki, A. Ahmadi
Department of Mechanical Engineering, Malek Ashtar University of Technology, Iran

This paper presented a three dimensional analysis for the buckling behavior of an imperfect orthotropic thick cylindrical shells under pure axial or external pressure loading. Critical loads are computed for different imperfection parameter. Both ends of the shell have simply supported conditions. Governing differential equations are driven based on the second Piola--Kirchhoff stress tensor and are reduced to a homogenous linear system of equations using differential quadrature method. Buckling loads reduction factor is computed for different imperfection parameters and geometrical properties of orthotropic shells. The sensitivity is established through tables of buckling load reduction factors versus imperfection amplitude. It is shown that imperfections have higher effects on the buckling load of thin shells than thick ones. Results show that the presented method is very accurate and can capture the various geometrical imperfections observed during the manufacturing process or transportation.

JTAM, Sofia, vol. 48 Issue 4 pp. 045-060 (2018), [Full Article]

ANALYTICAL STUDY OF ELASTIC-PLASTIC FRACTURE IN THE CRACK-LAP SHEAR MULTILAYERED BEAM CONFIGURATION

Victor Rizov
Department of Technical Mechanics, University of Architecture, Civil Engineering and Geodesy, 1 Chr. Smirnensky blvd, Sofia, Bulgaria

This paper reports an analytical study of delamination fracture in the Crack-Lap Shear (CLS) multilayered beam configuration with taking into account the material non-linearity. A delamination crack was located arbitrary along the beam height. It was assumed that the CLS mechanical response can be described by using a power-law stress-strain relation. It should be mentioned that each layer may have different material constants in the stress-strain relation. Besides, the thickness of each layer may be different. The classical beam theory was applied in the present study. The non-linear fracture behaviour was analyzed by the J-integral. Analytical solutions of the J-integral were obtained for homogeneous as well as for multilayered CLS beams. In order to verify the solutions obtained, analyses of the strain energy release rate were developed with considering material non-linearity. Material properties and crack location effects on the non-linear fracture behaviour were investigated. The analysis revealed that the J-integral value increases when the material non-linearity is taken into account. It was found also that the J-integral value decreases with increasing the lower crack arm thickness. The approach developed here is very convenient for parametric fracture analyses. The solutions derived can be used for optimization of the CLS multilayered beams with respect to their fracture performance.

JTAM, Sofia, vol. 48 Issue 4 pp. 061-077 (2018), [Full Article]

EFFECT OF HIGHER ORDER ELEMENT ON NUMERICAL INSTABILITY IN TOPOLOGICAL OPTIMIZATION OF LINEAR STATIC LOADING STRUCTURE

Naman Jain
Department of Mechanical Engineering, G. B. Pant University of Agriculture and Technology, Pantnagar, India

This paper presents the mathematical model to solve the topological optimization problem. Effect of higher order element on the optimum topology of the isotropic structure has been studied by using 8-node elements which help in decreasing the numerical instability due to checkerboarding problem in the final topologies obtained. The algorithms are investigated on a number of two-dimensional benchmark problems. MATLAB code has been developed for different numerical two dimensional linear isotropic structure and SIMP approach is applied. Models are discretized using linear quadratic 4-node and 8-node elements and optimal criteria method is used in the numerical scheme. Checkerboarding instability in the final topology is greatly reduces when incorporated 8-node element instead of 4-node element which can be confirmed through comparing the final topologies of the structure.

JTAM, Sofia, vol. 48 Issue 4 pp. 078-094 (2018), [Full Article]