International Journal of Mechanics

ISSN: 1998-4448
Volume 12, 2018

Notice: As of 2014 and for the forthcoming years, the publication frequency/periodicity of NAUN Journals is adapted to the 'continuously updated' model. What this means is that instead of being separated into issues, new papers will be added on a continuous basis, allowing a more regular flow and shorter publication times. The papers will appear in reverse order, therefore the most recent one will be on top.

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Volume 12, 2018

Title of the Paper: The Influence of Material and Geometric Parameters on the Design of Steel Mechanical Anchors to Concrete under Tension Loading


Authors: Michal Štrba, Marcela Karmazínová, Veronika Václavíková

Pages: 131-139

Abstract: This paper deals with some problems in case of the effective and efficient design of post-installed steel mechanical expansion anchors to concrete which are subjected to the tension loading using either static or cyclic loading force. Also the influence of some selected parameters and characteristics in case of the loadcarrying capacity determination and of the actual behaviour of these fastening members is discussed. All the presented information and results are mostly based on the previous theoretical and experimental research realized in last years on the authors’ workplace and oriented to a verification of these steel anchors to concrete using the effect of the mechanical interaction of both component materials (steel and concrete). Within the framework of mentioned research programme a large number of loading tests were performed for various loading cases and all the results were subsequently elaborated to get values of load-carrying capacity corresponding different failure mechanisms of these fasteners depending on the used material and geometric parameters as well as on the type of loading. They were also realized some additional loading tests for the verification of actual material properties of the selected members (especially in case of strength characteristics). All the data and test results obtained from the performed experiments were evaluated using statistic and probabilistic approaches to get the characteristic and design valuesof load-carrying capacity. Therefore, this article provides some additional information about the general principle of mentioned members for fastening as well as it complements some author’s previous publications in this field.

Title of the Paper: Probabilistic Modelling of Fatigue Crack - Some Observations about Conditional Probability


Authors: Z. Kala

Pages: 121-130

Abstract: The article deals with time-dependent analysis of the failure probability of a load bearing element of a steel bridge. The theoretical model of fatigue crack propagation is based on linear fracture mechanics. The Latin Hypercube Sampling statistical method is used to calculate the unconditional and conditional probabilities. The conditional probability is calculated by excluding those random observations that have a detectable crack length observed during the inspection. The effect of included and excluded observations of input random quantities on the conditional failure probability is mapped and shown graphically. It is proven that the number of stress peaks per year can be considered as one random variable for any time interval of the life span of the bridge.

Title of the Paper: On the Falls of Two Wheeled Vehicles


Authors: Andrea Bonci, Sauro Longhi, Emanuele Lorenzoni, Giuseppe Antonio Scala

Pages: 109-120

Abstract: The study and analysis of two-wheeled vehicle’s falls and critical situations are difficult tasks to perform due to the rather elaborate dynamics that come into play. However, to prevent such events, it is necessary a good understanding of the conditions that trigger them. To this purpose, suitable tools able to show how the vehicle's parameters may influence its dynamic behavior are required. In the present paper the analysis of the major falls relative to a two-wheeled vehicle is performed by means of dynamics simulations based on the motorcycle model presented by the authors in prior works. The simulations are also discussed in relation to alternative descriptions provided by theoretical instruments reported in the literature and the substantial consistency of the results is shown.

Title of the Paper: A Interface Formation in Two-Phase Flow Problems


Authors: K. Fraňa, I. Nová

Pages: 102-108

Abstract: The objective of the paper is a numerical investigation of the multi-phase unsteady flow problem representing the formation and kinetic of bubbles. The mathematical model is given by the equation system used commonly for the three-dimensional viscous unsteady laminar flow problem. Shapes and forms of the phase-interface between gas-liquid depend strongly on the used grid resolution. Generally for various grid resolutions, different bubble formations were found. However, the volumetric fraction of the gas in the mixture was identical up to particular time. In advanced time, different progress of the gas decomposition was identified and the gas amount in the mixture was significantly lower in respect to the theoretical assumption. Furthermore, kinetic and bubble formations were investigated in liquids with various kinematic viscosity. It was found that kinematic viscosity could evidently influence the bubble formation, size and shape, but not a capability of the liquid to capture gas in the liquid as it can be assumed.

Title of the Paper: Second Law Analysis of Ion Slip Effect on MHD Couple Stress Fluid


Authors: Abiodun A. Opanuga, Hilary I. Okagbue, Olasunmbo O. Agboola, Sheila A. Bishop

Pages: 96-101

Abstract: This paper is concerned with the numerical investigation of entropy generation in viscous incompressible MHD couple stress fluid in a rotating frame of reference. An approximate solution of the dimensionless velocity and temperature profiles are obtained and used to calculate the entropy generation rate and Bejan number. The influences of the governing parameters on velocity, temperature, entropy generation and Bejan number are presented with the aid of graphs.

Title of the Paper: Flow Structure of the Transverse Jet Interaction with Supersonic Flow for Moderate to High Pressure Ratios


Authors: Asel Beketaeva, Altynshash Naimanova

Pages: 88-95

Abstract: The vortex structures behind the transverse jet in a supersonic flow for moderate to high pressure ratios are studied. Numerical simulation is performed using the three-dimensional Favre-averaged Navier–Stokes equations coupled by the turbulence model which are solved by the algorithm based on the high-order non-oscillatory (ENO) scheme. The simulations correctly captured primary vortices: the well-known two counter-rotating vortices, the primary upstream vortex and the secondary upstream vortex, the horseshoe vortex, the pair of vortex in a separation region, and one pair of vortices appeared due to the interaction of the jet passing through the Mach disk, two pairs of vortices formed due to an overflow above the jet. The additional two vortices are found localized near the wall in the region behind the jet.

Title of the Paper: The Study of the Mixing Layer Particles Distribution in Dependence on the Convective Mach Numbers


Authors: Altyn Makasheva, Altynshash Naimanova

Pages: 79-87

Abstract: The numerical studies of the quasi two-dimensional supersonic turbulent gas-particle mixing layer are performed using the 2D-DNS (Direct Numerical Simulations). The system of Navier-Stokes equations of a multi-species flow is solved using the ENO scheme of a third-order accuracy. The dispersion of the particles is simulated by the Lagrangian method following their trajectories in the mixing layer. The study focuses on the roles of the large-scale vortex structures in a particle dispersion dependence on the Stokes numbers and convective Mach numbers.

Title of the Paper: Experimental Determination of Aeroelastic Derivatives for a Small-Scale Bridge Deck


Authors: M. Cassaro, E. Cestino, G. Frulla, P. Marzocca, M. Pertile

Pages: 67-78

Abstract: A heaving and pitching two degrees of freedom bridge-deck sectional model apparatus representative of a long-span bridge was designed, built, and tested in the wind tunnel to acquire measurement of aeroelastic derivatives. The main objective of this study was the experimental validation of the procedure to compute the aeroelastic derivatives based on the Iterative Least Square Method identification technique. A good correspondence was found between the flutter derivatives experimentally extracted from the model, and the corresponding reference values, which have been analytically derived from the Theodorsen’s theory. A simulation model in MATLAB/Simulink® environment, useful for future control laws applications, was also developed and validated by real experimental results.

Title of the Paper: Frequency Analysis of Partially-Filled Rectangular Water Tank


Authors: K. Kotrasova, E. Kormanikova

Pages: 59-66

Abstract: This paper deals with experimental studies of sloshing of liquid in partially filled container subjected to external excitation horizontal harmonic motion. The theoretical background of fluid response on rectangular tank due to horizontal acceleration of tank bottom, impulsive and convective (sloshing) pressure and the fluid natural frequencies is presented in paper. The dynamic behavior of fluid filled rectangular container was monitored and was evaluated in realized experiment. The resulting peak slosh heights for various excitation frequencies and amplitudes in fluid filled rectangular tank are compared with the fluid natural frequencies.

Title of the Paper: Complete Study for Solving Navier-Lame Equation with New Boundary Condition Using Mini Element Method


Authors: Ouadie Koubaiti, Jaouad El-Mekkaoui, Ahmed Elkhalfi

Pages: 46-58

Abstract: The objective of our article is to solve the Navier-Lame equation with a new boundary CA;B condition using the mixed finite elements method . We compare between minielement method and the ordinary finite element method by the other side. We compute the displacement and its divergence simultaneously by using an extra unknown. We prove the existence and uniqueness of the weak and discrete solution by proving the discrete inf-sup and coerciveness conditions. We expose two ways of comparison, that the first way we calculate the rate α called speed of convergence found by each of the two numerical methods, all this will be done by the use of the linear regression. An analytical example is used to validate the accuracy, convergence and robustness of the present mixed finite elements method for elasticity. In order to evaluate the performance of the method, and to confirm our method, the numerical results of mini element method are compared with others coming from commercial code like Abaqus system.

Title of the Paper: Post-Newtonian Equations for Free-space Laser Communications between Space-based Systems


Authors: Jose M. Gambi, Maria L. Garcia del Pino, Jonathan Mosser, Ewa B. Weinmüller

Pages: 38-45

Abstract: The purpose of this paper is to show that the equations for relative motions derived from the two systems of post-Newtonian equations presented here, allow to increase the acquisition, pointing and tracking accuracy when compared to the Newtonian equations aimed to describe free-space laser communications between Low Earth Orbit (LEO) satellites, so as between LEO and Medium Earth Orbit (MEO), and Geostationary Earth Orbit (GEO) satellites. The equations discussed in this work are similar, but not equivalent to those proposed for space debris removal, i. e. in the context of spacebased systems to throw middle size LEO debris objects into the atmosphere via laser ablation. In fact, the present equations are computationally much more affordable because the aim is now less demanding, and so they result from subtractions within each post-Newtonian system here provided.

Title of the Paper: Estimation of Dynamic Behavior and Energy Efficiency of Thrust Hybrid Bearings with Active Control


Authors: Alexander Babin, Sergey Majorov, Leonid Savin

Pages: 32-37

Abstract: The present paper considers analysis of world tendencies of application of bearings with feedback control systems in various types of rotor machines. A possibility of qualitative improvement of operational characteristics has been highlighted for bearings with integrated additional functions of automated diagnostics and active control of geometric, rheological and force parameters. The present paper features a mathematical model, its implementation in a form of an algorithm, and numerical results including pressure and temperature distribution in a bearing in question, load capacity and rotor’s axial trajectories. A quality index has been formulated for thrust tapered land hybrid bearings with a central feeding chamber that is based on a combination of minimum power loss due to friction and stability of motion of a rotor. Various combinations of roughness and axial gaps have been taken into account.

Title of the Paper: Influence of Non-Linear Behavior on Seismic Response Parameters


Authors: Rita Greco, Alessandra Fiore, Ivo Vanzi

Pages: 19-31

Abstract: This paper deals with the effects of post-yielding stiffness on the response of non-linear structural systems under seismic actions. In detail, two hysteretic models are considered: a bilinear plastic model, representing structures that exhibit strain hardening characteristics, and an elastic-perfectly-plastic model, widely adopted in design codes. For these models, a parametrical study is carried out to assess the influence of post-yielding stiffness ratio on some non-linear response quantities, such as the response modification factor, the ductility demand and the damage index. The analysis is developed on a SDOF system subject to El Centro earthquake and demonstrates that the elastic-plastic constitutive law is excessively conservative to evaluate structural deformations. Finally the study provides useful information also from an energetic point of view.

Title of the Paper: Axisymmetric Deformation Analysis of Thick-Walled Cylinders and Rotating-Disks Using an Improved Adomian Decomposition Method


Authors: Safa Bozkurt Coşkun, Zuhal Elif Kara

Pages: 14-18

Abstract: In this study, a problem arising in advanced engineering mechanics governed by a singular differential equation is solved using an improved Adomian decomposition method. The technique was previously used in literature for the solution of two-point singular boundary value problems in applied mathematics. Authors extend the use of the mathematical technique to presented problem and the results show that improved Adomian decomposition method can be successfully used in the axisymmetric deformation and stress analysis of thick-walled cylinders and rotating disks.

Title of the Paper: Model of Pressure Losses in Pipes During the Transport of Heavy Oil with 11 API Gravity


Authors: Manuel A. Falconi, Enrique T. Tamayo, Héctor L. Laurencio, Jorge P. Vega, Elvis P. Gualotuña, Edwin R. Grijalva, Luís Grijalva Campana

Pages: 8-13

Abstract: During the transport of heavy oils by pipes, there are difficulties related to their high viscosity with non-Newtonian behavior, directly affecting the performance of the transport facilities, because of the inaccuracies of the calculation methodologies. In the present work it obtain a mathematical model that describes the pressure variations for non-Newtonian oil flow in pipes; obtained from the limitations of methodologies and correlations, that allows the evaluation of the simultaneous effects of the viscous force and of mixing in the laminar and turbulent regime during the transport of heavy oils by pipes. Equation 15 is the generalized theoretical model for the calculation of pressure variations in the transport of heavy crude oil by pipeline. It takes into account the variation of temperature during transport, the effects of viscous friction, and the effects of mixing between flow layers. The values of the flow index for the transport of heavy oil of 11ºAPI by pipes oscillates between 0,917 and 0,929 in function of the temperature values that vary between 29 oC and 69.8 oC. The consistency index varies between 13.55 Pa.s and 1.46 Pa.s for the same temperature range.

Title of the Paper: Numerical Study of Disperse Materials Process in a Continuous-Flow Plasma Reactor


Authors: Issakhov A. A., Urmashev B. A.

Pages: 1-7

Abstract: The paper presents a numerical study of the temperature propagation in the direct-flow plasma reactor, which is solved by the compressible Navier - Stokes equations that is approximated by finite volume method, the numerical algorithm based on the SIMPLE method. In the numerical algorithm of the equation system can be divided into four stages. The first stage is that the transfer of momentum carried out only by convection and diffusion. The intermediate velocity field is solved by the solution of the differential velocity gradient equation with the Green-Gauss Cell Based scheme. For the pressure field is applied PRESTO numerical scheme. In a third step it is assumed that the transfer is carried out only by the pressure gradient. The fourth step of the equation is solved for the energy transport equation as well as the momentum equations by the Green-Gauss Cell Based scheme. The algorithm is parallelized on high-performance systems. With this numerical algorithm was obtained numerical results of temperature distribution in a continuousflow plasma reactor. Numerical modelling allows us to give a more precise description of the processes that have been identified and studied theoretically and can reveal new physical phenomena processes that are not yet available, seen in experimental studies. Simulation results show that the constructed numerical model provides the necessary accuracy and stability, which should accurately describe the process during the time interval.