International Journal of Mechanics


ISSN: 1998-4448
Volume 9, 2015

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 9, 2015


Title of the Paper: Consideration about Lateritic Mineral Pneumatic Conveying in Dense Phase

 

Authors: Enrique Torres Tamayo, Hernán Yánez Ávila, Ángel León Segovia, Gustavo Rodríguez Bárcenas

Pages: 343-348

Abstract: In the nickel companies, the pneumatic conveying has been limited by the excessive energy expense that reaches the 18, 82 MJ/T. The causes that originate this difficulty are: the incorrect selection of the gas transporter speed, the existence of the feeders numberless and the infinite variety of physical and aerodynamic characteristics of the materials to transport that lead to the inaccuracy of the pneumatic conveying projects. Starting from the existent knowledge for the solids pneumatic transport in flowed and dense phases a descriptive theoretical model is deduced whose parameters (difference of speed between the gas and the solid and flotation speed) are obtained with data of an experimental installation. To obtain the parameters of the pattern is used the method of solution differential equations Runge - Kutta fourth order, like part of a procedure iterative that it leads to the minimization of the average error module between the experimental values and the predicted for the pattern. With the employment of the pattern it is simulated the dependence of the pressure losses, the solid flow and the concentration of the mixture in function of the gas flow of the lateritic mineral pneumatic transport systems. The reduction of the losses pressure with the increment of the speed fluid is confirmed in values less than 6,12 m/s in the horizontal transport and 5,21 m/s in the vertical one. The transport in continuous dense phase extends until the 18 m/s in both cases.


Title of the Paper: Analysis of the Impact-Induced Two-to-One Internal Resonance in Nonlinear Doubly Curved Shallow Panels with Rectangular Platform

 

Authors: Yury A. Rossikhin, Marina V. Shitikova, Muhammed Salih Khalid J. M.

Pages: 329-342

Abstract: The problem of the low-velocity impact of an elastic sphere upon a nonlinear doubly curved shallow panel with rectangular platform is investigated. The approach utilized in the present paper is based on the fact that during impact only the modes strongly coupled by the two-to-one internal resonance condition are initiated. Such an approach differs from the Galerkin method, wherein resonance phenomena are not involved. Since is it assumed that shell’s displacements are finite, then the local bearing of the shell and impactor’s materials is neglected with respect to the shell deflection in the contact region. In other words, the Hertz’s theory, which is traditionally in hand for solving impact problems, is not used in the present study; instead, the method of multiple time scales is adopted, which is used with much success for investigating vibrations of nonlinear systems subjected to the conditions of the internal resonance.


Title of the Paper: Numerical Solution of Boundary Inverse Problems for Plane Orthotropic Elastic Solids

 

Authors: Igor Brilla, František Janíček

Pages: 323-328

Abstract: We deal with numerical analysis of inverse problems for orthotropic solids when measured data are given only on the boundary of the domain. In this paper we have elaborated an iterative procedure to the solution of inverse problems for orthotropic solids when input data measured from suitable states are sufficient for determination of unknown material parameters. We deal with numerical experiments.


Title of the Paper: Using of Finite Element Method and Computational Analysis of Mechanical Properties of Stent-grafts

 

Authors: Stepan Major, Marie Hubalovska

Pages: 319-322

Abstract: The paper presents process of modeling and simulation as one of the most important method in current research in the area of biotechnological engineering. The paper focuses on implementation of the finite element method (FEM) as basis for creation of computer simulation model of mechanical properties of tubular laser cut stents. The FEM was applied for computational analysis and representation of dependence of the radial forces as functions of displacement and compressed stent diameter of two stent materials (Nitinol-49 and Nitinol-55) in different stent geometry. The simulation models created in SolidWorks® Simulation program were validated by experimental measured data and confirm good agreement.


Title of the Paper: Simulation of Nonlinear Physical Processes with the Generalized Phenomenological Equation

 

Authors: Sergey O. Gladkov, Sophie B. Bogdanova

Pages: 309-318

Abstract: Using a phenomenologically constructed Lagrangian function, a nonlinear partial differential equation is obtained, which describes the space – time distribution of a physical scalar parameter n(r,t), which can be density, concentration, temperature, etc. For the one-dimensional case phase trajectories in three dimensions are obtained depending on the numerical parameter of the problem, designated as x3.


Title of the Paper: Virtual Testing of Advanced Driving Assistance Systems

 

Authors: Maria Russo Spena, Francesco Timpone, Flavio Farroni

Pages: 300-308

Abstract: This paper presents some results on the development and testing of new solutions in the field of driving automation. The introduction of increasing levels of vehicle automation aimed at enhancing road safety requires a renewed approach to the research and development process and needs a multi-actor environment where the innovation can be tested. Indeed, vehicle automation spans several scientific disciplines and it is becoming exceedingly difficult and too costly for a single research innovation team to go in depth into all technologies and solutions. This is shifting the innovation process toward a multidisciplinary approach in which the only way to ensure an easy, rapid, efficient and scalable introduction of the required innovation is to adopt integrated and complex testing platforms for the simulation of automation solutions, based on a modular architecture, where independent components can be developed and then integrated and tested in a multi-actor environment. A platform for virtual testing is presented herein and employed to assess the performance of an integrated driving assistance solution based on computing appropriate surrogate measures of safety that allow for the transition between different automation logics in free-flow, car-following and emergency braking conditions.


Title of the Paper: Destruction of Brittle Materials by Microsecond Pressure Pulses at their Formation by Magnetic Pulse Method

 

Authors: S. I. Krivosheev, N. V. Korovkin, V. K. Slastenko, S. G. Magazinov

Pages: 293-299

Abstract: The possibility to use the magnetic pulse method of controlled pressure pulses formation in the microsecond interval with amplitude of up to 2 GPa has been presented. The comparison of test results of brittle materials has exhibited the possibility to analyze the destruction process both of samples having macro defects and defect-free ones. The controlled magnetic pressure makes possible to form by using the ultimate potential energy a set of key parameters (strength under static conditions, ultimate elongation, time of energy storage) featuring the process of destruction. Application of described criteria approach allowed to determine the relation between surface fracture energy and impact parameters using the measured initial crack propagation velocity. The application of magnetic pulse method for testing conducting materials has also been proven.


Title of the Paper: Criteria and Layouts for Improving Approaches to the Improvement of the Seismic Resistance of Masonry Constructions

 

Authors: Ileana Corbi, Francisco Pallares, Luis Pallares

Pages: 286-292

Abstract: The preservation of masonry constructions poses some fundamental issues as regards the protection of the historical and monumental heritage. To this regard, a series of approaches should be suitably conceived for improving the resistance of masonry constructions to dynamic events, for example through the adoption of properly designed composite reinforcements. Design approaches may be vary very significantly depending on the geometry and the expected failure modes of the structural system, in order to best fit the specific need of the structure under analysis. Within this framework, the paper focuses on some design issues and criteria, presented according to some selected typologies and geometries of the masonry structures; the objective consists of strengthening the structural system and increasing the seismic resistance of the construction, tailored on its shape and overall behavior.


Title of the Paper: Geodetic Support in the Context of GIS for Monitoring Mechanics of Movement of the Earths Surface in Mining Subsidence

 

Authors: Vladimir Sedlak

Pages: 279-285

Abstract: The mining activity influence on the environment belongs to the most negative industrial influences. As a result of underground mining of the mineral deposits in the surface creates the subsidence trough, i.e. caving zone which could be dangerous for any movement of people in this zone. Character and size of the mining subsidence on the surface depends mainly on the geotectonic ratios of rock massif above the mined out area. Knowing the extent of the subsidence trough in mining areas is determining to prevent the entry of people into these dangerous zones. Conditioning factors to establish the extent of the movement of the earth's surface above the mined out area are a geodetic way surveyed deformation vectors which can be derived from the processing of measurements at monitoring stations based on these mining tangent territories. The limits of undermined regions in many cases equal to isolines connected so called break points occurred in the front of the subsidence borders. The theory for the estimation of polynomial break points in the case of subsidence analysis is presented. The theory was developed as a part of the kinematics analysis procedures for the evaluation of the magnesite deposit in the suburb of Kosice-Bankov on the northern outskirts of the city of Kosice in the eastern Slovakia. The subsurface abandoned mine Kosice-Bankov is located in the immediate vicinity of the recreational and tourist zone in the northern suburb of the city of Kosice. Some numerical and graphical results from the break points estimation in the magnesite deposit Kosice-Bankov are presented. The obtained results from the abandoned mining area Kosice-Bankov were transferred into GIS for the needs of the local governments in order to conduct the reclamation of this mining landscape.


Title of the Paper: A Comparison of Imputation Techniques in Acoustic Level Datasets

 

Authors: Claudio Guarnaccia, Joseph Quartieri, Carmine Tepedino, Ljiljana Petrovic

Pages: 272-278

Abstract: Continuous and high acoustical noise level is one of the recurrent problems that affect citizens of large cities. For this reason, acoustic level long term monitoring is a common practice in large urban areas, in which, according to the international regulation, the noise levels must be kept under certain thresholds. Frequently, in order to predict acoustical level values in future periods, forecasting methods are implemented. Many of these techniques need a calibration or training phase to be performed on a continuous measurements dataset, i.e. not affected by missing data. In this paper the performances in the reconstruction of missing data of two techniques are compared. The models implemented are a Time Series Analysis (TSA), based on the evaluation of trend and periodicity of the series, and a Regression (REGR) method, based on a modification of linear stochastic regression. The error analysis will show interesting features of both the models. In addition, the study of dataset mean and variance preservation will highlight the differences between a deterministic (TSA) and a stochastic (REGR) imputation approach. Finally, a validation on 21 data not used in the calibration phase is presented, comparing the predictive performances of two TSA models, calibrated on datasets with 60 missing data and in which different imputation techniques have been used.


Title of the Paper: Drag Force on a Confined Particle: Particle Transport

 

Authors: Mounia Makhoul, Philippe Beltrame, Maminirina Joelson

Pages: 260-271

Abstract: The hydrodynamic interaction between a channel confinement and a suspended body is an important class of hydrodynamic problems. In this paper, we point out a quantitative study of the effects of the channel boundaries on the drag force exerted by the fluid on the particle surface. As results, we can obtain the drag coefficient as well as the flow in the channel due to the presence or the motion of the particle. We consider a channel with a periodic variation in diameter in which an axisymmetric particle is translating along its axis. Our numerical resolution is performed using the boundary integral formulation of Stokes flow which is solved using a boundary elements method. The numerical results are presented for the cases of spherical and ellipsoidal particles. Different geometric effects like the curvature of the channel, the particle geometry, and the channel size to particle size ratio are handled. Using the second law of Newton, these results enable us to study the existence and kinds of the mechanisms allowing the transport of the suspended particle and experienced by the computed drag force.


Title of the Paper: Single vs Multi Parameter Calibration for the Numerical Simulation of Submerged Flows in Jet Grouting Applications

 

Authors: Stefania Evangelista, Gaspare Giovinco, Lidia Wanik

Pages: 252-259

Abstract: The numerical simulation of the diffusion of turbulent submerged flows contributes to understand the fundamental mechanisms of the jet grouting technology for a more efficient use of it. In fact, the erosive efficiency of the jet, and, consequently, the dimensions of columns strongly depend on the jet propagation modalities and the energy exchange between injected and surrounding fluids. Even though the mathematical basis of turbulence models are well established, their use requires dimensionless constants to be calibrated. In a previous study a numerical model was presented to simulate the turbulent diffusion of submerged jets. It was calibrated with literature experimental data, varying a single parameter and assuming the other ones as constant. In this work a multi-parameter calibration was carried out varying all the parameters. The numerical results obtained with both calibrations were compared with the experimental data to evaluate the best solution in terms of accuracy and computational efficiency.


Title of the Paper: New Design of the Headstock - Generator for Creating Folded Rotary Motion

 

Authors: Ľubomír Šooš, Peter Križan, Miloš Matúš, Juraj Beniak

Pages: 246-251

Abstract: The quality of machine tools or construction elements depends on the accuracy of the operation, the range of operating speed, the maximum rotational speed and the ability to quickly change the specified requirements. The tool or work-piece holder must meet specific demands for maximum speed, rigidity and maximum torque at low speed. This is often not possible to achieve a classic arrangement of the drive kinematic chain. Therefore was idea to create a generator assembled rotary motion. The proposed generator consists in the construction of the spindle, which is doubly stored and powered by two separate engines. This allows the generator to work in four separate modes providing the required sense of rotation up questions and their scope and desired torque at low speed.


Title of the Paper: A New Prognostic Method Based on Simulated Annealing Algorithm to Deal with the Effects of Dry Friction on Electromechanical Actuators

 

Authors: Matteo D. L. Dalla Vedova, Paolo Maggiore, Lorenzo Pace

Pages: 236-245

Abstract: In prognostics it is possible to apply several approaches with the aim to detect incipient failures, caused by progressive wear, of electromechanical actuators (EMA) in primary flight commands. The anticipation of a failure has to be performed through a correct interpretation of the degradation pattern, so to trig an early alert for maintenance and to properly schedule the servomechanism replacement. This paper proposes a prognostic approach based on the simulated annealing optimization method, able to identify symptoms of degradation before the behavior of the actuator becomes anomalous; friction failures are considered as the case study. The approach is validated through an experimental test bench, resulting in an adequate robustness and a high degree of confidence in the ability to early identify faults, with a low amount of false alarms or not annunciated failures.


Title of the Paper: Elastic-Plastic Calculation of a Steel Beam by the Finite Element Method

 

Authors: O. Sucharda, J. Vasek, J. Kubosek

Pages: 228-235

Abstract: The purpose of the paper is to assess behaviour of steel beams during a loading test and the FEM models which take into account computational nonlinearities. The steel beams are loaded with a single load. The calculation was made in ANSYS and vFEM, the own software under development. In case of vFEM which can be used for nonlinear solutions of tasks, the computation and algorithm are supported by examples.


Title of the Paper: Thermal Transient Analysis of the Railway Brake Disc Using the High-Speed Camera

 

Authors: Min-Soo Kim

Pages: 220-227

Abstract: When the friction braking is applied, high temperatures transition can be occurred in the brake disc from inside high thermal to outside in contact with the friction material. The evaluation technology of brake performance and thermal effects in braking has been generally developed with technology of speed improvement of railway vehicles. Particularly brake system of railway vehicles has a crucial role for the safety as well as riding quality of passengers. Brake dynamometer is designed to simulate the brake characteristic of the high speed train, analyze the experimental object, and also is used to develop and test the brake systems including brake parts. In this paper, we tried to analyze the temperature transition and/or pressure distributions of the brake disc surface during braking using the high-speed brake dynamometer and the high-speed camera with lighting system. Based on information from the acquisition images, we analyzed thermal images in a moment at the same position hourly. The highlight region in thermal image of the disc surface indicates the high temperature. Therefore we could find temperature transition or thermal characteristic of the disc surface. That is, the scattered distribution of thermal moves gradually to a point and be destroyed after that. The results also indicated that the formation and extinction area of hot spot of the disc surface was same region. And these research results will be introduced by means of a braking performance test evaluation technology as well as brake parts development on braking system of the railway vehicles.


Title of the Paper: Application of Electrical Impedance Spectrometry for Measurements of humidity Distribution in Aerated Concrete Masonry Constructions

 

Authors: S. Rubene, M. Vilnitis

Pages: 213-219

Abstract: In time when one of the most important construction trends is sustainable construction as well as cost saving on heating and cooling of buildings, it is important to acknowledge the possibilities of application of construction materials with high heat parameters and the ways in which these parameters can be obtained. Autoclaved aerated concrete (AAC) is a load bearing construction material, which has high heat insulation parameters, although it has one significant problem. If the autoclaved aerated masonry construction has high moisture content then it loses its heat insulation properties. This is the reason why it is important to detect the humidity distribution throughout the cross section of the masonry elements in order to conduct the drying process of the aerated concrete construction. Electrical impedance spectrometry (EIS) can be applied for monitoring of drying process of the masonry constructions and detecting of humidity distribution throughout the cross section of aerated concrete masonry constructions. Research of correlation between EIS measurements on autoclaved aerated concrete masonry blocks and absolute values of humidity content in the masonry blocks has been described in this paper.


Title of the Paper: Reinforced Concrete Wall Under Shear Load – Experimental and Nonlinear Simulation

 

Authors: Jiri Kala, Petr Hradil, Miroslav Bajer

Pages: 206-212

Abstract: Concrete-like materials models generally share in common some basic features of brittle materials such as pressure hardening, strain hardening and strain rate dependency. The elasto-plastic models are based on the condition of plasticity with the associative or non-associative plastic flow law. The modulus of elasticity of concrete is one of the most important parameters for determining the strain distributions and displacements. The numerical study was verified by an experiment carried out on the test specimen is a reinforced concrete wall with the dimensions 1000 mm x 1000 mm x 80 mm.


Title of the Paper: Study on the Adhesion Characteristic between Wheel and Rail Using the Scaled Test-Bench

 

Authors: Min-Soo Kim

Pages: 198-205

Abstract: Railway vehicles driven by wheels obtain driving force required to propulsion and braking by adhesion force between wheels and rails, this adhesion force is determined by multiplying adhesion coefficient of the friction surface by the applied axle load. In railway system, this adhesion coefficient is usually defined as the maximum traction/braking coefficient. To get the maximum traction/braking force represented as the adhesion coefficient, it is necessary to estimate the adhesion coefficient according to the speed difference between the wheel and the rail on the contact point. Scaled adhesion test-bench is an experimental device that contacts mutually with disc rollers which are equivalent to wheels and rails of railway vehicles, and rotates mutually by friction by driving each motor connected with roller axes. Test procedure for adhesion characteristics on slip change is following; First, initial speed of the wheel disc with radius 0.1 [m] is set in 1000 [r.p.m] after applying the axle load of wheel/rail as 200 [kgf], then reduce the speed of the rail disc with radius 0.15 [m] from 628 [r.p.m] to 30 [r.p.m] to generate slip while maintaining the initial speed of wheel disc constantly. And test procedure for adhesion comparison under dry and wet is following; First, the wheel disc's (radius 0.15 [m]) initial speed is set in 500 [r.p.m] after applying the axle load of wheel/rail as 142.63 [kgf], then reduce the rail disc's speed from 500 [r.p.m] to 475 [r.p.m] (generates slip) for one minute while maintaining the speed of wheel disc. This paper also observes the variations in surface roughness and hardness of the wheel/rail discs for the sliding distance in each position and describes the development of a scaled adhesion test-bench for analyzing of the adhesion coefficient between wheel and rail.


Title of the Paper: Extension the Matrices of one Dimensional Beam Elements for Solution of Rectangular Plates Resting on Elastic Foundation Problems

 

Authors: Abdulhalim Karasin

Pages: 189-197

Abstract: Complex medium of foundations is a frequently recurring problem for many engineering structures in case of transmission of rational, vertical or horizontal forces. In general it is often difficult to find suitable analytical models for plates on elastic foundation problems. In this study, it is proposed to extend analytical solutions of the discrete one-dimensional beam elements resting on one- or two-parameter elastic foundation for solution of plate problems. Firstly, the derivations of the governing differential equations and exact shape functions are obtained. In order to observe the influences of foundation parameters, some graphical comparisons have been done on stiffness terms and the shape functions for solving general plate problems.


Title of the Paper: Vibration Based Structural Health Monitoring to Evaluate the Damage in Flexural Members

 

Authors: David P. Thambiratnam, Hoi Wai Shih, Tommy H.T. Chan, Zhi Xin Tan

Pages: 181-188

Abstract: Structures are built to last a long time. However, during their service life, they may suffer damage due to deterioration with age, changes in loading patterns and random actions such as impacts. This damage must be detected and assessed so that appropriate retrofitting can be carried out to prevent structural failure. Damage in a structure affects its stiffness and this in turn affects its vibration characteristics. This is the basis of vibration based structural health monitoring techniques which have emerged as a means of evaluating the health of a structure. This paper uses vibration based methods to develop and apply techniques to evaluate the damage in beam and plate structures that form important components in bridges and buildings. This paper selects two damage indices based on the vibration properties. These damage indices are called (i) modal flexibility and (ii) modal strain energy. Results show that these indices can successfully detect and locate damage in beam and plate structures. The success of this technique will enhance the safety and efficiency of structures and prevent unexpected and sudden collapse.


Title of the Paper: The Development and Testing of a New Type of the Temporary Steel Truss Footbridge with Closed Cross-Section

 

Authors: Michal Štrba, Marcela Karmazínová

Pages: 173-180

Abstract: In this paper there is some particular information about the development of a new sort of a temporary modular steel footbridge for pedestrians and cyclist, which was designed as a truss system with the deck below the supports and with the closed cross-section. Actually, this development was connected to the research project, which was one of the several ones from the recent period, where they all were focused on temporary steel footbridges design, developing and testing (including full-scale testing) and which were realized on our workplace in cooperation with research centres and companies. In this case the new footbridge has a span 18 - 36 m and it is divided into 3.0 m long assembly units. They were selected some its details for the loading tests and finally it was performed also a test of the prototype. Therefore, this paper brings the results of those experiments as well as some particular conclusions.


Title of the Paper: Forecasts of Dynamic Response for Structural Systems with Low Robustness

 

Authors: I. Corbi, N. Mastorakis

Pages: 167-172

Abstract: In the paper one addresses the problem of forecasting the dynamic response of structures behaving according to rocking modes. Purely rotational motions do often occur in structures and facilities subject to seismic solicitations, turning those in monolithic rigid bodies or assemblies. Rocking dynamics, thus, usually interests a wide variety of structures and objects, also including historical and monumental constructions or ancient art items, usually made of large-dimension monolithic stone blocks. Nevertheless, the high non-linearity and complexity affecting the rocking dynamics of rigid bodies make hard to perform some reliable forecasts about their response, and push towards the adoption of alternative strategies.


Title of the Paper: Propeller Performance Measurements at Low Reynolds Numbers

 

Authors: Miguel Silvestre, João Morgado, Pedro Alves, Pedro Santos, Pedro Gamboa, José Páscoa

Pages: 154-166

Abstract: Propellers are being used as propulsive devices since the early days of aviation. However, if they are not properly designed, they can have poor efficiency, especially at low Reynolds numbers environments such as the case of the high altitude airships envisioned in the MAAT project. Experimental data those operating conditions are crucial to effectively improve and validate new numerical design tools. This work presents the development of an experimental setup for low Reynolds propeller testing. The experimental data were successfully compared against reference data to validate the test rig. In addition, the performance data for commercially available propellers that were not characterized in the existing literature is also presented.


Title of the Paper: On Conditions for Reducing the Hazard of a Gas Explosion in the Kitchen

 

Authors: Iurii H. Polandov, Vitalii A. Babankov, Sergei A. Dobrikov

Pages: 145-153

Abstract: Often gas explosions occur in amenity rooms and, especially, in the kitchen. During the research, as a rule, pressure is studied as the development of such  process, under the influence of which rooms can be destroyed. While doing this, one can miss not less dangerous factor - high temperature of combustion products, under the influence of which fire can occur. Meanwhile, it seems that its more preferable to assess not only the possibility of destruction of a building, but also the risk of fire. At the same time, of course, to assess the danger of destruction of the rooms during the explosion, it is reasonable to use a well - known process indicator - pressure. But for assessing the fire hazard of explosion it is proposed to use a measure called the index of fire danger in the gas explosion (briefly If), defined as the integral over time of the difference between the temperature of the gases in the room and the ignition temperature of the interior of the kitchen: the increase in the index corresponds to an increase of fire hazard. Based on the results of the physical experiment it is shown that when k=S/V2/3>0,03 where S is the area of the window, m2; V is the volume of the room, m3, that is, for most ordinary kitchens, the idea that the approximation of the gas stove to the window contributes to the reduced explosion pressure, remains in force. In addition, analysis using a numerical model based on the method of large particles showed that the traditional arrangement of furniture along the walls is the most preferable from the point of view of reducing the pressure of a possible explosion, and from the point of view of reducing fire hazard.


Title of the Paper: Experiment on Production Time for Model Creation on Small Fused Deposition Modeling Device

 

Authors: Juraj Beniak, Peter Križan, Miloš Matúš, Ľubomír Šooš

Pages: 138-144

Abstract: The production time is one of very important parameters which can influence the whole economic profit in production process. Also in case of Rapid Prototyping we are interesting in time for which we are able to produce the prototype parts. The Rapid prototyping systems are also in many cases used as production device to produce the components for final use. For this reason we have prepared the experiment in which is measured the production time necessary for building of models with different settings. The aim of this article is to present how the production time changes depending on different settings of production process, and orientation. Specimens are produced on small Fused Deposition Modeling device with use of wired PLA (Polylactic Acid) plastic. This measured data are statistically evaluated and compared with tensile strength values of produced models.


Title of the Paper: Numerical Investigation of Methane-Air Mixture with CO2 Dilution (in Fuel, First Air and Second Air Inlet) in a Gas Turbine Combustor Chamber

 

Authors: Guessab A., Aris A., Benabdallah T., Cheikh M.

Pages: 128-137

Abstract: A numerical study on non-premixed combustion methane/air and biogas/air mixture in swirl combustor is performed. In this study the inlet velocity, NO and temperature of fuel and combustor geometry and size are kept to be the same but the effect on the variation of CO2 dilution is observed. Results of this simulation show as the CO2 dilution rate increases, flame temperature, NO and combustion velocity decreases.


Title of the Paper: Natural Convection in a Square Cavity with Two Baffles on the Vertical Walls: Experimental and Numerical Investigation

 

Authors: Giorgia Nardini, Massimo Paroncini, Raffaella Vitali

Pages: 120-127

Abstract: Natural convection in a square enclosure filled with air is experimentally and numerically analyzed. The cavity has horizontal and vertical Plexiglas walls with discrete sources. Two Plexiglas baffles are attached to its vertical walls between the sources symmetrically. The effect of different baffle lengths is investigated. The results are presented for Rayleigh numbers from 104 to 105. The fluid flow field, thermal field and heat transfer are analyzed for two different baffle lengths through interferograms, streamlines, isotherms and velocity maps. The dimensionless baffle lengths investigated are Lb= 0.2 and Lb= 0.4. The results clearly demonstrate that different baffle lengths have a significant effect on the heat transfer and flow characteristics of the fluid. The flow field pattern is baffle length and Rayleigh number dependent. It is, in fact, observed that for Lb= 0.2 the flow tends to circulate as a vortex strangled by the baffles, while for Lb= 0.4 the flow tends to separate into two different vortices. The Nusselt number increases as Rayleigh number increases and it is a decreasing function of baffle length for the lower sources and increases for the higher sources. The average Nusselt numbers from Lb = 0.2 to Lb = 0.4 decrease on average by 23% on the lower source and it increases on average by 29% on the higher source.


Title of the Paper: F.E.M. and Experimental Studies Concerning New Devices for Seismic Damping of Buildings Subjected to Earthquakes

 

Authors: Adriana Ionescu

Pages: 112-119

Abstract: This paper presents the F.E.M. and experimental studies of new Romanian devices for dissipation of seismic energy for buildings affected by Romanian Vrancea earthquakes. These devices were tested by experimental and F.E.M. studies in static cases because their behaviors are the same in dynamic cases. The studies were made in order to determine the stiffness and damping non-linear parameters of these new devices which are necessary to obtain the hysteresis curves. The hysteresis curves obtained within the study can be simulated with Bouc-Wen model of hysteresis and the mathematical relation of this type of hysteresis can be used in order to simulate the new SERB dampers on a building subjected to seism using special simulation software.


Title of the Paper: Manufacturing Technology of Prosthetic Parts: 3-axis CNC Milling of Master Model

 

Authors: Bílek Ondřej, Javořík Jakub, Lukovics Imrich

Pages: 105-111

Abstract: Medical prostheses are intended to replace human body parts lost by injury or missing from birth or to supplement defective body parts. The current trend of prostheses production is directed to the application of computer systems processing digitized information and to a marked increase in the use of computer numerical machine tools (CNC). The objective of this study is to extend the application of reverse engineering technology and knowledge to fabricate the master model of missing limb. The optically digitized right upper limb was transformed into the computer master model. Further computer aided (CA) systems were implemented to automate manufacturing process and to improve the flexibility of production. The resulting master model is a crucial for the fabrication of unique prosthetics, cosmetic covers, or cavities for injection and casting. In the case study, emphasis is placed on computer aided manufacturing (CAM) and 3 axis milling on regular CNC machine tool.


Title of the Paper: The Variability of Gravitational Constant G in Constitutive Medium - Based Models of Space: The Vacuum-Polarizable Approach and the Fluid-Dynamic Model of Gravity as a Pressure Force

 

Authors: Luigi Maxmilian Caligiuri

Pages: 90-104

Abstract: Gravitation is still the less understood among the fundamental forces of Nature. The ultimate physical origin of its ruling constant G could give key insights in this understanding. In a previous paper the author proposed, starting from ZPF inertia hypothesis and the Polarizable -Vacuum approach to General Relativity, a novel model of G as a function of quantum vacuum energy density, showing that, according to it, G could actually be a function of the distance r from the mass generating the gravitational field. In this paper the variability of G within a scalar fluid dynamics-like theory of gravity as a pressure force, basing on the above previous results, is outlined. An analytical expression for G(r ), under the hypothesis of spherically symmetric body and slowly varying gravitational potential, is also derived in this case and compared with that previously obtained within the Polarizable – Vacuum approach by starting from different hypothesis. The results strongly suggest G could be actually related to the property of physical vacuum viewed as a medium characterized by special properties and depend from the distance from massive bodies. The proposed idea could give new interesting insights into a deeper understanding of gravitation and represent a starting theoretical point for the engineering of unimaginable solutions related, for example, to the field of gravity control and space propulsion.


Title of the Paper: Engine Air Intake Filters - Consequences of Premature Replacement

 

Authors: Marius Toma

Pages: 83-89

Abstract: The life of an internal combustion engine is influenced by a multitude of parameters, engine’s wear being one of the most important. The dust particles from the atmospheric air that pass through the air cleaners heavily influence their wear at the kinematic couples of internal combustion engines. The main purpose of air filters is to reduce the quantity of particles that reach the burning chambers of internal combustion engines. To achieve this purpose, air cleaners with high filterring efficiency are used and also an increased importance must be given to maintenance activity. In this paper were tested original air cleaners manufacturer and aftermarket air cleaners. The following results are being presented: the pressure drop on air filters at the time of their replacement; the filtering efficiency of new and used filters; the size of dust particles that passed throught new and used air filters. This paper demonstrates that the replacement of air cleaners based on the distance travelled by the car or the usage time (in kilometres or years) without taking into account their real estate is uneconomical and disadvantageous due to technical state evolution of the engines.


Title of the Paper: The Synchronized Force Impact Measurement and Visualization of Single Cavitation Bubble Generated with LIB

 

Authors: D. Jasikova, M. Muller, M. Kotek, V. Kopecky

Pages: 76-82

Abstract: In this paper we present the results of the synchronized investigation of the single cavitation bubble behavior. The cavitation bubble is generated with Laser Induced Breakdown (LIB) technique that is based on single laser shot that is synchronized with c high speed shadowgraphy visualization and the pressure force measurement.  The bubble dynamics response in the field of fluid can be detected acoustically by PVDF needle hydrophones or optically by high speed CCD cameras working on frequencies up to 180 kHz. Here we present two PVDF film signals corresponding to two bubble wall distances and we are following the run of the first peak in the signal, which corresponds to the interaction between the wall and shock wave, which is radiated at the bubble initiation due to rapid plasma expansion. The main goal of this research was to set the optical setup for the laser induced breakdown and to create the calibration relation curve for the bubble size dependence on the input energy of the laser beam. This calibration curve was related to the collapse time of the cavitation bubble to estimate the lifespan of each bubble. This information was the entry condition for the setup of the visualization technique.


Title of the Paper: Strategies for the Protection from Structural Failures Under Seismic Events

 

Authors: A. Baratta, I. Corbi, O. Corbi, N. Mastorakis

Pages: 69-75

Abstract: In the paper one presents some researches in course of development in the field of protection of new and existing structures subject to dynamic events. The described researches involve both theoretical, numerical and experimental features on the topic. Design issues for base isolation systems are reported, as well as the dynamic behavior of some structures that can be modeled under monolithic rigid mode and multi-storey steel frames are presented, and the coupling with some control devices is investigated. As concerns the rigid blocks, pure rocking motion is analysed and the response attenuation is accomplished by means of dampers introducing a dissipative liquid mass. In the case of the steel frame, the mitigation of the dynamic response is pursued by means of a base isolation system, able to get a significant reductions of dynamic response variables. Reinforcement techniques for existing buildings based on composite technology are referred to in the final part of the paper, with special regards to new composites with cement matrix.


Title of the Paper: The Experimental Study of the Coherent Structures Generated in the Agitated Vessels and Effected by Fluid Viscosity

 

Authors: D. Jasikova, B. Kysela, M. Kotek, V. Kopecky

Pages: 61-68

Abstract: This paper presents results and interpretation of the dataset processed with Proper Orthogonal Decomposition (POD). The object of this work was the description of the coherent structures that are present in the mixing process. The results obtained by TR PIV measurements focused on detailed flow analysis in selected region in the context of impeller movement were processed with POD and OPD algorithms. The study was focused on the viscosity effect on the coherent structure behavior. Here we worked with three degree of viscos liquids: pure water, solution of 28% mono-ethylene glycol (MEG) and 43% MEG in water. The rounds of the Rushton impeller were set to follow the Re = (5.104 – 1.105) to perform fully turbulent flow. The main aim of this study was to analyze the coherent structures in the higher eigenmodes and its energy contribution to the flow system.


Title of the Paper: Investigation of Traffic-Induced Vibrations on a Historic Swing Bridge in Italy

 

Authors: Adriana Netti, Alessandra Fiore, Pietro Monaco, Giuseppe Carlo Marano

Pages: 53-60

Abstract: This work presents a study on a very peculiar bridge, the “St. Francesco da Paola” swing bridge in Taranto, with the aim to investigate the problem of vertical traffic-induced vibrations and their effects on pedestrians. A wide monitoring ambient vibration testing has been conducted on the bridge, in order to obtain useful data for identification of modal parameters and analysis of vibration level. A detailed finite element 3D-model has been realized on the basis of survey and design data; then a model updating has been calibrated with experimental data. The vertical vibrations have been compared to reference values from technical standards/literature in order to estimate the vibration level, and a probabilistic approach has been adopted to evaluate the pedestrian comfort.


Title of the Paper: Comparative Machinability and Surface Integrity in Grinding of Titanium

 

Authors: Bílek Ondřej, Javořík Jakub, Čop Jiří

Pages: 43-52

Abstract: This paper investigates the surface grinding process to evaluate the effect of input parameters of titanium, which is commonly known to have poor machinability. Dry and wet grinding experiments have been carried out and optimal conditions for grinding titanium have been identified with respect to feed rate, wheel speed and depth of cut. The incorporation of cooling improves integrity of ground surface which significantly extended resistance to wear. Moreover, comparative ANOVA roughness model has been derived. This model approved an interaction among all input parameters.


Title of the Paper: Quasianalytic Evaluation of Stability of Nonlinear Dynamic Systems Oscillations

 

Authors: Lelya Khajiyeva, Askat Kudaibergenov, Askar Kudaibergenov, Almatbek Kydyrbekuly

Pages: 36-42

Abstract: The stability of nonlinear systems is studied by the method of partial discretization. The steady motion of a mechanical system is defined here as its motion without resonant oscillations. In order to avoid resonance oscillations in the operating modes of the system a quasianalytic evaluation of the behavior of the solution of the perturbed state equation is made. The equation is partially discretized in the class of generalized functions (Dirac delta function). An analytical solution characterizing the behavior of a small perturbation δf in time has been obtained. The efficiency of the proposed approach is based on the simplicity of the solution and visualization of its results. This is illustrated by the example of stability analysis of resonance oscillations at the basic frequency of physically and geometrically nonlinear systems. The results obtained in this paper are in good agreement with well-known results obtained by other methods.


Title of the Paper: Computer-Aided Design Of New Service Doors For Recreational Vehicles

 

Authors: Yary Volpe, Lapo Governi, Rocco Furferi

Pages: 26-35

Abstract: Recreational vehicles (camper, vans and motorhomes) are equipped with service doors to access to specific areas such as water tank or luggage zone. As the state-of-the-art technology stands at present, two different typologies of service doors are manufactured: doors with plastic frames, obtained by injection molding, and doors with aluminum frames realized by extruded bars. Plastic frame-based doors are characterized by concealed hinges (i.e. hinges integrated in the frame), therefore resulting aesthetically pleasant to the final user. Unfortunately, they are basically produced in standard dimensions due to the complexity and costs of injection molding process; as a consequence the number of available measures in the market is really limited. Quite the reverse, aluminum frame-based doors can be produced in customizable formats by adjusting the bars length. The main drawbacks of this second typology of doors are that the cutting and bending machines, used to produce them, need to be periodically tuned in order to take into account possible environmental thermal  variations and, moreover, in order to achieve 180° opening, the hinges are required to stick out the wall. Moving from these considerations, this work proposes a CAD/CAE-based design of an innovative service door based on a modular design where frames consist of extruded plastic bars, cut in required length, which are capable to comprise concealed hinges. Accordingly, the new door designed in the present work brings together the advantages offered by the standard solutions pushing forward the RV door technological state of the art.


Title of the Paper: Experimental Study of Turret-Mounted Automatic Weapon Vibrations

 

Authors: Jiri Balla, Zbynek Krist, Cong Ich Le

Pages: 16-25

Abstract: The purpose of this article is to introduce a new approach to finding the dynamic characteristics of weapon parts when burst-fired. The result is both vibrations of the parts mounted on track vehicle such as cradle and turret, and the excitation force acting from the weapon onto the mount. The experiments were tested out on a 30 mm soft recoil gas operated cannon turret-mounted on a track vehicle. All results follow from these technical experiments, as well as other derived parameters after frequency and correlation analysis. The outputs can be used for validation of a dynamic model of a weapon system mounted on a track vehicle, and the procedure can be used as an example of a practical technique and methodology for other weapon systems.


Title of the Paper: Thermodynamic Analyzes of Film Cooling for a Restructured Cooling Holes at the end of Gas Turbine Engine Combustor

 

Authors: Ehsan Kianpour, Nor Azwadi Che Sidik, Mohammad Hussein Razavi, Mohammad Akbari, Masoud Afrand, Iman Golshokouh

Pages: 11-15

Abstract: This research was done to analyze the effects of two different blowing ratios of BR=1.25 and BR=3.18 on the film cooling effectiveness at the combustor outlet, whereas the cylindrical and row trench holes with alignment angle of +60 degrees were considered. In the current research, a three-dimensional representation of a Pratt and Whitney gas turbine engine was simulated and analyzed with a commercial finite volume package FLUENT 6.2.26. This study has been carried out with Reynolds-averaged Navier-Stokes turbulence model (RANS) on internal cooling passages. The combustor combines the interaction of two rows of dilution jets, which are staggered in the stream-wise direction and aligned in the span-wise direction, with that of film cooling along the combustor liner walls. The entire findings of the study showed that trenched holes performed much more efficiently at both blowing ratios, especially at BR=3.18.


Title of the Paper: Numerical Comparison of Different Solution Methods for Optimal Boundary Control Problems in Thermal Fluid Dynamics

 

Authors: Daniele Cerroni, Sandro Manservisi, Filippo Menghini

Pages: 1-10

Abstract: In this paper we propose and compare different methods for the solution of the control-adjoint-state optimality system which minimizes an objective functional in temperature. The minimization is constrained by the energy convection-diffusion equation with velocity field defined by the incompressible Navier-Stokes system. Three methods, based on different solution spaces, for solving the adjoint-state optimality system are compared. In the first one, as in the standard approach, the controlled temperature field is assumed to belong to a regular class of solutions with smooth derivatives and the resulting control-adjoint-state optimality system is solved in a segregated way. In the second one we introduce a fully coupled solution approach, where, in order to obtain a more robust numerical algorithm, the boundary control is extended to the interior and Dirichlet conditions are implicitly enforced through a volumetric force term. In the last approach we introduce Discontinuous Galerkin formulation for the energy equation in order to seek discontinuous solutions. Numerical two and three-dimensional test cases are reported in order to show the validity of the proposed approaches. The results are compared in term of solution smoothness and achievement of low values of the objective functional.