International Journal of Mechanics


ISSN: 1998-4448
Volume 7, 2013

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Issue 1, Volume 7, 2013


Title of the Paper: Actual Behaviour of Composite Externally CFRP-Reinforced Timber Beams – Stress Analysis

Authors: Marcela Karmazinova

Pages: 1-9

Abstract: The paper is focused on the problems of compositeCFRP-reinforced timber beams. CFRP reinforcement is representedby the lamella externally bonded on the tensile part of the beam forthe strengthening the member to increase in the resistance from theviewpoint of both the ultimate and serviceability limit states. Usuallyfor the resistance determination the concept of composite structuralmembers based on the substitute (ideal, respectively) cross-section isapplied, but the usage of this principle is depending on the efficiencyof the shear connection (here bonded) between CFRP reinforcementand basic material – timber. It is mainly influenced by the glue typeand also by the bonded connection quality. The practical experiencesobtained from the tests oriented to the experimental verification ofthe actual behaviour show that the efficiency is very different independence on the particular structural member. The paper presentsselected results of the measurement of the stresses in CFRPreinforcement and in timber base, which can give the information onthe level of the mutual interaction between both materials and on therightness of the substitute cross-section approach mentioned above inthe case of timber beams. The paper deals with the verification of theactual normal stresses, mainly in the cross-section part of the contactbetween timber and CFRP reinforcement (here bottom tensile edge).Actual normal stresses obtained from the tests have been used for theevaluation of actual characteristics of the substitute cross-section,especially the second moment of the area. Applying those derivedcross-section characteristics the effects of the longitudinal shear, thatmeans shear forces and stresses, have been calculated aimed to theverification of the bonded shear connection.


Title of the Paper: A Model of Vehicle Fuel Consumption at Conditions of the EUDC

Authors: Michael Ben Chaim, Efraim Shmerling

Pages: 10-17

Abstract: A mathematical model for evaluating vehicle fuel consumption on a 100 km interval at standard operating conditions for the EUDC (Extra-Urban Driving Cycle) is presented. The extra-urban cycle fuel consumption has two significant components: fuel consumption at average speed and during accelerations, and therefore, in the model, it is determined separately for two different operating modes: average speed and accelerations. In each of these modes fuel consumption is calculated based on the efficiency of the engine. Unlike previously developed models, which determine fuel consumption based on specific fuel consumption, ours determines fuel consumption based on the efficiency of the engine, which makes the model more adequate since it incorporates engine mode changes. The efficiency of the engine is expressed as a function of the speed mode of the engine and of the degree of power utilization of the engine.


Title of the Paper: A Model for Vehicle Fuel Consumption Estimation at Urban Operating Conditions

Authors: Michael Ben Chaim, Efraim Shmerling

Pages: 18-25

Abstract: A mathematical model for Estimation of vehicle fuel consumption on a 100 km interval at standard operating conditions is presented. Vehicle fuel consumption is presented via mathematical modeling for urban operating conditions. Vehicle fuel consumption is calculated separately for four different operating modes: average speed, accelerations, decelerations and idle mode. This approach was chosen due to the fact that a significant part of fuel consumption at urban conditions occurs at idle mode. The efficiency of the engine is expressed as a function of the speed mode of the engine and of the degree of power utilization of the engine. The adequacy and accuracy of the model is verified using experimental calculations. Moreover, it is shown that the effect of various design parameters on vehicle fuel consumption can be studied utilizing the proposed model.


Title of the Paper: Drop Impingement onto a Wetted Surface: Effects of Gravity and Shape

Authors: Murat Dinc, Donald D. Gray

Pages: 26-36

Abstract: Single water drops impinging onto wet, flat, isothermal surfaces have been simulated numerically to investigate the influence of gravity level and drop shape on the resulting flow. The commercial code ANSYS 14 Fluent was employed to perform 2D-axisymmetric simulations for incompressible, laminar and unsteady flow conditions using the explicit Volume of Fluid (VOF) surface tracking method with the Piecewise Linear Interface Calculation scheme (PLIC), the Continuum Surface Force model (CSF), and adaptive mesh refinement. Simulations of a spherical water drop impacting an upward facing wet surface (Re = 6690, We = 139, h/D = 0.837, ? = 0?) were performed for different gravity conditions based on some of the planets and asteroids in our Solar System. These are Solar surface gravity (g = 275 m/s2), Jupiter surface gravity (g = 24.8 m/s2), Earth surface gravity (g = 9.81 m/s2), Mars surface gravity (g = 3.7 m/s2), Lunar surface gravity (g = 1.68 m/s2), Pluto surface gravity (g = 0.61 m/s2), asteroid Vesta surface gravity (g = 0.252 m/s2), asteroid 1999RQ-36 surface gravity (g = 0.038 m/s2), and zero gravity (g = 0). While the general evolution of the craters was similar, the rate at which they evolved increased as the value of g increased. The impact of an upward moving drop on a downward facing layer in Earth surface gravity (g = ?9.81 m/s2) caused a significantly different flow. Because laboratory observations have found that water drops in the size range under study deviate slightly from true spheres, three cylindrical drops, one having same diameter and mass as a spherical drop and the others having same diameters but different masses, were simulated. The flows produced by the cylindrical drops were sufficiently similar to that produced by a sphere of equal volume that it will not be necessary to account for the much smaller deviations from sphericity which occur in reality in order to obtain realistic simulations.


Issue 2, Volume 7, 2013


Title of the Paper: Noise Sources Analysis in a Wood Manufacturing Company

 

Authors: Claudio Guarnaccia, Nikos E. Mastorakis, Joseph Quartieri

Pages: 37-44

Abstract: The need for noise assessment in occupational health is a growing necessity, especially in production activity during which high sound pressure levels occur. A continuous exposure to relevant noise dose can lead to several effects on human health and quality of life. A resume of the auditory and non-auditory effects is given as an introduction to an experimental activity performed in a wood manufacturing company. The different sources are characterized by means of single source noise emission measurements performed during specific periods out of working time. In addition, the acoustic climate is evaluated with measurements taken during normal working activity. The emission of each single source operating in idling phase or with a sample load is highlighted and the correspondent spectrum is used as an identification pattern. The possibility of creating a database of noise spectra is suggested as a first step towards specific mitigation actions and monitoring tools tuned on frequency analysis.


Title of the Paper: An Investigation on Free/Forced Vibration of a Piezoelectric Circular Cylindrical Panel Located on an Elastic Foundation

 

Authors: A. Oveisi, M. Gudarzi, S. M. Hasheminejad

Pages: 45-56

Abstract: This paper presents an exact three-dimensional free and forced vibration analysis of an axially polarized transversely isotropic piezoelectric circular cylindrical panel on elastic foundation. Due to the wide use of piezoelectric materials as sensor/actuators, to the best knowledge of the authors, no one has studied the effect of imperfection in bonding of these piezo-layers to the host layer for cylindrical panels. Using separation of variables, three-dimensional exact solution is presented under generalized simply support boundary conditions. In addition, the effect of elastic foundation on both structure natural frequency and steady state frequency response is investigated. For validation purposes the results are compared with those obtained from FEM and the results from previous works. Finally conclusions are made.


Title of the Paper: Adaptive Sliding Mode Control of Chaos in Nonlinear Friction-Driven Oscillator

 

Authors: E. Maani Miandoab, A. Yousefi-Koma

Pages: 57-64

Abstract: In this paper, the adaptive sliding mode controller (ASMC) is used to control the chaotic vibration of a block-on-belt system subjected to harmonic external excitations and supported by a limited energy supply. To control the chaotic vibration of this system, a switching surface is defined such that it becomes easy to ensure the stability of the error dynamics in the sliding mode. Then an adaptive sliding mode controller (ASMC) is derived to ensure the occurrence of the sliding motion and the Lyapunov stability analysis is used to guarantee the stability and tracking of the controlled system. Two different desired responses are considered in this study and the effectiveness of the proposed method is shown for both cases.


Title of the Paper: Roughness Analysis of Local Fatigue Fracture Surface

 

Authors: Stepan Major, Stepan Hubalovsky

Pages: 65-72

Abstract: A stereophotogrammetrical analysis in scan electron microscopy is used to investigate the fracture morphology of the high-strength low-alloy steel generated under combined bending-torsion fatigue loading. The type of loading is described by loading ratio Z= τa / (σa + τa ) (σa is the bending amplitude and τa is the torsion amplitude). The fatigue life of investigated specimens was in the order of 106 cycles (high cycle fatigue). Roughness characteristics studied in two mutually perpendicular directions on facets in the region of crack initiation were found to be sensitive to the crack front positron. The investigation of surface topography revealed the presence of the opening Mode I in all investigated crack front locations.


Title of the Paper: On the Problems of Testing Methodology used in Case of the Temporary Steel through Truss Footbridge Development

 

Authors: Michal Štrba

Pages: 73-80

Abstract: This paper brings some information about a performed research project in which a testing methodology was used in case of development of a new type of temporary steel truss footbridge for pedestrians and cyclists. At first, the mentioned structure was designed according European standards using finite elements method software and then the point of research was to experimentally verify the actual behaviour of the footbridge in the event of real loading. For that purpose they were firstly performed tests on selected members and details using tension and compression static force. According the obtained results it was used cyclic force for some parts as well. Finally, there was performed a test of full-scale prototype as well. In this paper there are some particular results and illustrative photos of the research presented.


Title of the Paper: Dynamics of Shell Conveyer with Maltese Cross

 

Authors: Jiri Balla, Van Yen Duong, Zbynek Krist

Pages: 81-89

Abstract: The paper deals with one weapon application of the Maltese cross in the shell or cartridge conveyer using a hydraulic drive. Kinematics and dynamics of this mechanism is discussed. The first model with one DOF and the second model having two DOF are worked out. Both models use mechanism with varying transmission function. The equations describing the mechanical and hydraulic part are explained.


Title of the Paper: Minimizing Uncertainty of Selected Composite Materials Using Various Mathematical Approaches

 

Authors: Stella B. Bondi, Steven J. Makonis, Jr., Zia Razzaq, Resit Unal

Pages: 90-100

Abstract: Three different mathematical approaches are presented herein as procedural and numerical results for flexural rigidity characterization of Fiber Reinforced Polymer (FRP) plates retrofitted with various types of composites and fabrics. The first approach is based on theoretical and experimental findings using composite materials such as FRP and Kevlar® during simulation of heavy-ion cosmic radiation. Since it is thought that FRP and composites are non-magnetic and corrosion resistant, it is assumed that a better protection from radiation in both space and during exposure to radioactive situations would be provided. The second approach used FRP plate flexural rigidity values calculated with a central finite-difference iterative scheme while utilizing the experimental load-deflection relations based on bending tests. The tests were performed on each plate by applying a concentrated load at the center. A fourth-order partial differential equation of plate equilibrium was adopted to estimate the plate flexural rigidities and ultimately obtain the theoretical load-deflection relations. The results were verified with Navier’s solution for the same type of loading. The third approach used FRP and various composites to their fullest potential with ultimate goal to minimize uncertainty by comparing probability and evidence theories. The application of these criteria or standards will be demonstrated through practical analysis and design examples. This research further expanded the FRP and composites knowledge base by identifying material strengths and weaknesses through conducting experimental versus theoretical studies. The proposed methods synthesize the study of the emerging new materials with a probability-based approach. Such an approach is considered a pre-cursor to the so-called Load and Resistance Factor Design (LRFD) philosophy based on which a currently evolving FRP design specification will be based and will subsequently become Standard of Practices and Procedures that could provide promising tools to implement various mathematical models during conceptual design and selection of appropriate composite material.


Title of the Paper: Optimization of Tuned Mass Dampers for RC Structures with Projection in Plan

 

Authors: S. M. Nigdeli, G. Bekdas

Pages: 101-108

Abstract: Irregularities of civil structures are an important issue when structures are under the effects of strong ground motions. Several irregularities may affect the seismic behavior of structures. Irregularities may lead important damages or collapses. Using cantilever members in reinforced concrete (RC) structures is an important irregularity in plan for vibrations in vertical direction. Also, these projections in plan can affect the response of the structure in horizontal direction and these structures may suffer from big displacements during earthquakes. In order to prevent these displacements at RC structures, a tuned mass damper (TMD) can be used to improve the seismic behavior. In this study, RC structures with projection in plan were passively controlled with an optimum TMD. The structure was compared with two equivalent structures without projection. The optimum parameters of TMD were found by using a metaheuristic algorithm called Harmony Search (HS). Different TMD parameter ranges were used in optimization and the optimum results were verified by using benchmark earthquakes. According to the different cases of the TMD parameters, the optimum TMD is effective on obtaining a better seismic behavior than structures without projection.


Title of the Paper: Optimization of T-shaped RC Flexural Members for Different Compressive Strengths of Concrete

 

Authors: G. Bekdas, S. M. Nigdeli

Pages: 109-119

Abstract: In this study, cost optimization of T-shaped reinforced concrete (RC) beams under flexural effect was investigated for different compressive strengths of concrete. Harmony search (HS) algorithm which is a music inspired metaheuristic algorithm, was employed to find the minimum cost per unit length of the beam elements by searching best suitable cross-section dimensions and amount of the reinforced steel bars. The RC beams were designed according to ACI 318-Building Code Requirements for Structural Concrete. In additional to different compressive strengths of concrete, the optimum values with minimum costs were investigated for different cross-section ranges under various objective flexural moments. According to optimum results, the proposed optimization approach may be a great source for the preliminary design of RC members.


Title of the Paper: Experimental Investigation and Finite Element Simulation of Laser Lap Welding of SS304 Sheets

 

Authors: N. Siva Shanmugam, G. Buvanashekaran, K. Sankaranarayanasamy

Pages: 120-127

Abstract: Laser beam welding (LBW) is one of the most important manufacturing processes used for joining of materials. It is also a remarkably complicated, nonlinear operation involving extremely high temperatures. Since its invention more than two decades ago, laser beam welding has been more of an art than a science. Laser welding of austenitic stainless steel AISI 304 the candidate material of this research work is used in several areas, including electronics, medical instruments, home appliances, automotive and specialized tube industry. An industrial 2kW CW Nd:YAG laser system, available at Welding Research Institute (WRI), BHEL Tiruchirappalli, is used for conducting the welding trials for this research. After proper tuning of laser beam, laser welding experiments are conducted on AISI 304 grade sheets for lap joint configuration to evaluate the influence of input parameters such as beam power, welding speed and spot diameter of the beam on weld bead geometry i.e. bead width (BW) and depth of penetration (DOP). Three dimensional finite element simulation of high density heat source is performed for laser welding technique using finite element code SYSWELD for predicting the temperature profile on AISI 304 stainless steel sheets. The temperature dependent material properties for AISI 304 stainless steel are taken into account in the simulation, which has a great influence in computing the temperature profiles. The latent heat of fusion is considered by the thermal enthalpy of material for calculation of phase transition problem. A Gaussian distribution of heat flux using a moving heat source with a conical shape is used for analyzing the temperature profiles. Experimental and simulated values for weld bead profiles are analyzed for stainless steel material for different beam power, welding speed and beam spot diameter. The results obtained from the simulation are compared with those from the experimental data for laser welding of lap joint configuration and it is observed that the results of numerical analysis (FEM) are in good agreement with experimental results, with an overall percentage of error estimated to be within ±5%.


Title of the Paper: A Numerical Approach to Design a Compliant Based Microgripper with Integrated Force Sensing Jaw

 

Authors: R. Bharanidaran, T. Ramesh

Pages: 128-135

Abstract: Technological advancement in precision industries generates enthusiasm in engineers and scientists. Microgripper is an elementary device in precision manipulation of micro-objects. For precision manipulation of micro devices or micro assembly of components, the design of microgripper is a challenging task. Design of mechanism influenced micro devices are required new methodology. In this research work, an attempt has been made to develop a new compliant mechanism design of microgripper with force sensing jaw. Topology optimization technique has been used to derive the conceptual design of mechanism of microgripper. This conceptual design is post-processed, that is, the flexure hinges and smoothened edges are introduced in the senseless regions suitably to achieve the final design. Gripping force acting on the object is calculated introducing a cantilever jaw. Deflection of cantilever jaw is directly proportional to the gripping force acting on the object. A detailed study of the flexible cantilever gripping device and its behavior with various parameters of circular flexure hinges is performed and the gripping force is measured through finite element software ANSYS Workbench. First natural frequency of the micro gripper and out of plane sagging due to the self weight of the micro gripper is measured to ensure the effectiveness of design.


Title of the Paper: Evaluation of Projectile Ramming Process in New and Worn Smooth Barrels of Guns

 

Authors: Jiri Balla, Stanislav Prochazka, Van Yen Duong

Pages: 136-144

Abstract: This article deals with the influence of barrel wear and barrel thermal deformation of tank cannon on the ramming process. Barrel wear was used as input data from measuring on 125 mm smooth tank cannon barrels. Barrel thermal deformation and the ramming process of APFSDS (Armor-Piercing Fin-Stabilized Discarding Sabot) projectiles were calculated using ANSYS Workbench software utilizing the Finite Element Method (FEM). The ramming process calculation was done for two case scenarios: the first case was for a new barrel deformed by barrel thermal effects from firing; the second case was for a worn barrel influenced by the same thermal effects. The reaction force as the most important standardized factor used to evaluate the effect and safety of the ramming process is verified by experiment performed on the above mentioned 125 mm weapon system. The calculated results are reasonably compatible with the experimental results. The research results also provide a background for the state-of-the-art knowledge to upgrade the Czech Defense Standards (COS) for the ramming device of artillery weapons and tanks.


Title of the Paper: Experimental Verification of Actual Behaviour, Failure Mechanism and Load-Carrying Capacity of Floor and Roof Thin-Walled Ferro-Cement Panels

 

Authors: Marcela Karmazinova, Jindrich Melcher

Pages: 145-153

Abstract: This article deals with the influence of barrel wear and barrel thermal deformation of tank cannon on the ramming process. Barrel wear was used as input data from measuring on 125 mm smooth tank cannon barrels. Barrel thermal deformation and the ramming process of APFSDS (Armor-Piercing Fin-Stabilized Discarding Sabot) projectiles were calculated using ANSYS Workbench software utilizing the Finite Element Method (FEM). The ramming process calculation was done for two case scenarios: the first case was for a new barrel deformed by barrel thermal effects from firing; the second case was for a worn barrel influenced by the same thermal effects. The reaction force as the most important standardized factor used to evaluate the effect and safety of the ramming process is verified by experiment performed on the above mentioned 125 mm weapon system. The calculated results are reasonably compatible with the experimental results. The research results also provide a background for the state-of-the-art knowledge to upgrade the Czech Defense Standards (COS) for the ramming device of artillery weapons and tanks.


Issue 3, Volume 7, 2013


Title of the Paper: Nonlinear Dynamic Response of a Fractionally Damped Suspension Bridge Subjected to Small External Force

 

Authors: Yury A. Rossikhin, Marina V. Shitikova

Pages: 155-163

Abstract: Nonlinear force driven coupled vertical and torsional vibrations of suspension bridges, when the frequency of an external force is approaching one of the natural frequencies of the suspension system, which, in its turn, undergoes the conditions of the one-to-one internal resonance, are investigated. The method of multiple time scales is used as the method of solution. The damping features are described by the fractional derivative, which is interpreted as the fractional power of the differentiation operator. The influence of the fractional parameters (orders of fractional derivatives) on the motion of the suspension bridge model is investigated.


Title of the Paper: Properties of Irradiated PA11 by Accelerated Electrons

 

Authors: A. Mizera, M. Manas, Z. Holik, D. Manas, M. Stanek, J. Navratil, M. Ovsik, M. Reznicek

Pages: 164-171

Abstract: Radiation processing involves the use of natural or manmade sources of high energy radiation on an industrial scale. The principle of radiation processing is the ability of high energy radiation to produce reactive cations, anions and free radicals in materials. The industrial applications of the radiation processing of plastics and composites include polymerization, cross-linking, degradation and grafting. Radiation processing mainly involves the use of either electron beams from electron accelerators or gamma radiation from Cobalt-60 sources. The PA11 polyamide 11 tested showed significant changes of temperature stability and mechanical properties after irradiation. From this point view, new applications could also be seen in areas with service temperatures higher than their former melting point. The comparison of the temperature stability and mechanical properties of irradiated and non irradiated PA11 is presented in this paper.


Title of the Paper: Preservation Provisions for the Environmental Protection of Egyptian Monuments subject to Structural Vibrations

 

Authors: Ottavia Corbi, Abdel Hamid Zaghw, Adel Elattar, Ahmed Saleh

Pages: 172-179

Abstract: The Egyptian area is characterized by a number of outstanding historical minarets, which represent a significant part of the monumental and architectural heritage of the country. Such structures usually are rather vulnerable as regards to environmental vibrations due to earthquakes, strong winds or even traffic vibrations, and proper protection strategies are required. In the paper some possible control devices are considered based on passive or semi-active control strategies, also making recourse to the adoption of smart materials.


Title of the Paper: Track Defects and the Dynamic Loads due to Non-Suspended Masses of Railway Vehicles

 

Authors: Konstantinos Giannakos

Pages: 180-191

Abstract: The motion of a railway vehicle on the rail running table is a forced oscillation with a forcing excitation (force), and damping expressed by a random, non-periodic function. The motion is described by formulas and it is illustrated through diagrams which have the form of a “signal”. The railway vehicle has the Suspended (Sprung) and the Non Suspended (Unsprung) Masses. The track defects/ faults are the random excitation for the rolling wheels of the vehicle. In the case of the Sprung Masses of the vehicles, the forces resulting from the excitation (track defects) are not large and have small effect on the rolling of the wheel. In the case of the Unsprung Masses the forces resulting from the excitation (track defects) are large and have grate effect on the rolling of the wheel. The track, is simulated (with the observer situated on the wheel) as an elastic means with damping. The general equation that describes the problem is the second order differential equation of motion. In this paper the aforementioned equation is presented for the case of a railway vehicle rolling on a railway track and its solution is presented for the Unsprung (Non-Suspended) Masses of the vehicle that act directly on the track without the presence of any spring or damper.


Title of the Paper: Bearing Capacity Analysis of Reinforced Concrete Beams

 

Authors: Oldřich Sucharda, Jiří Brožovský

Pages: 192-200

Abstract: This paper deals with a non-linear analysis of reinforced concrete beams. The goal is to determine the total bearing capacity of the structure. For purposes of the analysis, an elastic-plastic model of concrete has been chosen. In some calculations, other constituent models of concrete have been used. These models of the concrete are based on fracture mechanics, model of smeared cracks or plasticity. The paper also compares the model of smeared reinforcement and that of discrete reinforcement. When analysing a specific example of a T-beam, stochastic modelling has been used.


Title of the Paper: On the Structural Assessment of Masonry Vaults and Domes

 

Authors: Alessandro Baratta

Pages: 201-209

Abstract: Basic properties of masonry do not allow to rely on tensile strength, and flexural strength cannot be trusted on. Nevertheless in 2D walls and in double curvature vaults, a particular organization of the vault apparatus can in some instances, through the action of compression and friction, give place to a equilibrium pattern including tension, which explains the unexpected good performance of some walls and cupolas.


Title of the Paper: Static and Dynamic Simulation in the Seismic Behavior of a Building Structure using ANSYS Program

 

Authors: Adriana Ionescu, Madalina Calbureanu, Mihai Negru

Pages: 210-217

Abstract: This paper present the results of seismic behavior simulation obtained in two different methods used to analyze a two stories building. The methods presented in the paper are: the static equivalent forces method and the modal spectral analysis method. Both methods were applied using Finite Elements Method and ANSYS program for the tri-dimensional structure of the building. The study was made in order to determine which type of analysis is more convenient and easier to be applied in ANSYS program for simulating the seismic behavior of a classical type of reinforced concrete building.


Title of the Paper: Microhardness of Electron Beam Irradiated Polyamide 6.6

 

Authors: D. Manas, M. Ovsik, M. Manas, M. Stanek, P. Kratky, A. Mizera, M. Bednarik

Pages: 218-225

Abstract: Experimental study deals with the influence of beta radiation on the micromechanical properties of the surface layer of polyamide 6.6 with 6% crosslinking agent addition. When subjecting the polyamide 6.6 to beta radiation, the structure as well as the surface layer show structural changes (crosslinking, degradation). The injected specimens were irradiated by doses of 0, 33, 45, 66 and 99 kGy. Irradiation of the specimens caused changes in the surface layer similar to the process of nitriding or cementation in metals. There was an improvement in some micromechanical properties of the surface layer of polyamide 6.6. The improvement/deterioration of micromechanical properties of surface layer of polyamide 6.6 measured by the instrumented microhardness test is the content of this experimental study.


Title of the Paper: An Innovative Modular System for the Building of Timber Cylindrical Roofs

 

Authors: Dora Foti, Domenico De Tommasi

Pages: 226-233

Abstract: This article aims to analyze the mechanical characteristics of an innovative constructive system for arches and vaults made of hollow wooden boxes designed with interlocking joints. This new technology ensures at the same time good mechanical performances and fast installation and servicing. Experimental studies have been conducted on the base material, on the individual blocks and, thereafter, on an arch built in scale 1:1 to evaluate the displacements, the deformations and the maximum load to failure and to examine its compatibility with the provisions of the code on force. Finally a limit analysis has been developed to model the behavior of the structural system under the testing load.


Title of the Paper: Three-Dimensional Numerical Analysis of Restricted Water Effects on the Flow Pattern around Hull and Propeller Plane of LNG Ship

 

Authors: M. Nakisa, A. Maimun, A.Y.Sian, Yasser M. Ahmed, A. Priyanto, Jaswar, F. Behrouzi

Pages: 234-241

Abstract: This paper aims to show bank and shallow water hydrodynamic force and moment effects on hull of Liquefied Natural Gas (LNG) ship that Lateral and vertical hydrodynamic forces are generated due to influence of confined water by using Computational Fluid Dynamics (CFD) methods. The simulation method is a numerical solution of the Navier-Stokes equation based on a finite volume method. Liquefied Natural Gas (LNG) carrier frequently navigates through noticeable banks with shallow water for its maneuvers. The flow pattern around a travelling or navigating ship in restricted water is affected significantly by the water depth and vicinity of the wall of a quay or canal. Sailing the ship in vicinity of bank may consequence in making hydrodynamic loads such as sway force and yaw moment on ship hull also changing velocity and pressure contours around the hull and the generation of asymmetric flow around the ship, hence may lead to potentially dangerous situations. In this research work the behaviour of a LNG carrier in confined water where there is a confined in water depth and in waterway width has been studied experimentally and numerically. From the results of pressure and velocity measured, the distribution of hydrodynamic lateral forces was obtained. Acting of hydrodynamic forces and moments on the hull ship and wake pattern behind ship hull has been investigated using CFD. The numerical results have been validated by comparison with model testing in Marine Teknologi Center (MTC) of Universiti Teknologi Malaysia (UTM).


Title of the Paper: Influence of Runner section on Curing Rate during Injection Molding of NBR Compound

 

Authors: K. Kyas, M. Stanek, A. Skrobak, M. Manas, D. Manas, M. Reznicek, V. Senkerik

Pages: 242-250

Abstract: Right used computational analyses are commonly good tool for technical industry to improve process. This paper show using computational analysis during injection molding process. With using two different shape and two different section dimensions of injection molding channel there is shorted cycle time for product which is represented by 30 mm cube. Results show the save of time for different temperatures of injection mold. These received dates should be helpful for setting of injection machine and cycle in rubber injection molding process.


Title of the Paper: Nonlinear Seismic Analysis to Evaluate the Effectiveness of Damped Braces Designed for Retrofitting r.c. Framed Structures

 

Authors: Fabio Mazza, Alfonso Vulcano

Pages: 251-261

Abstract: The supplementary energy dissipation represents an efficient technique for the seismic protection of structural systems. In the last few decades several applications have been used in many countries, adopting damping systems with different characteristics, depending on both the arrangement of the damped braces and kind of damping device. However, for a widespread application of this technique, practical design procedures and simple numerical models are needed. In this paper, attention is focused on the modeling and nonlinear seismic analysis of framed structures equipped with friction, metallic yielding, viscoelastic and viscous dampers. A design procedure is proposed for proportioning damped braces in order to attain, for a specific level of seismic intensity, a designated performance level of the structure. A six-storey reinforced concrete (r.c.) framed building, designed in a medium-risk seismic region, is supposed to be retrofitted as in a high-risk seismic region. Two different criteria are followed for distributing the stiffness and strength properties of dissipative braces, over the whole at each storey, among the single braces. A numerical investigation is carried for studying the nonlinear dynamic behaviour of the designed structures. The results show that the proposed design procedure is effective and reliable.


Title of the Paper: Minimising the Actuating Power of Vertical Transport Installations by Optimisation of Dynamic and Kinematics Parameters

 

Authors: Florin Dumitru Popescu

Pages: 262-276

Abstract: The specific energy consumption is mainly influenced by kinematics and dynamic measures of vertical transport installations as well as by the compatibility of different composing parts and their subcomponents. The optimisation of kinematics and dynamic parameters characterising a transport cycle is decisive considering the energy consumption. Also considering the operation of the vertical transport installations, as well as the character of the variation of kinematics and dynamic parameters during a race, it has been considered that one of the adequate optimisation methods of these parameters is the calculus of variations. In order to apply this calculus, the definition of the optimisation functional and restrictions is imposed. The acceleration and deceleration periods during each race of a vertical transport installation may be considered as periods of transitional processes where kinematics and dynamic measures variations take place (acceleration, speed and forces) as well as some electric measures (actuating motor’s current). One of the basic performance parameters of the operation of the vertical transport installations is the specific energy consumption during a cycle. It therefore means that the optimisation of the transport cycle related to this parameter may be realised using a functional with a function under the integral depending on the electric energy consumption during a race.


Title of the Paper: How Amount of Talc Influence the Polymer Flow

 

Authors: M. Stanek, D. Manas, M. Manas, K. Kyas, V. Senkerik, A. Skrobak, J. Navratil

Pages: 277-284

Abstract: Delivery of polymer melts into the mold cavity is the most important stage of the injection molding process. This paper shows the influence of cavity surface roughness, amount of filler (in this case – talc) and technological parameters on the flow length of polymers into mold cavity. Application of the measurement results may have significant influence on the production of shaping parts of the injection molds especially in changing the so far used processes and substituting them by less costly production processes which might increase the competitiveness of the tool producers and shorten the time between product plan and its implementation. Because the finishing operations of machining are very time and money consuming leading to high costs of the tool production.


Title of the Paper: Properties and Design of Dissipative Visco-recentring SMA members for Civil Structures

 

Authors: Ottavia Corbi, Abdel Hamid Zaghw

Pages: 285-292

Abstract: In the paper one focuses on some fundamental issues in the modeling and design of dynamic control devices conceived for structural applications, based on the exploitation of Shape Memory Alloys (SMAs). General properties and advantages are described which make these alloys particularly suitable for applications aimed at the response reduction under dynamic events, and some indications to be considered at the design stage of the SMA devices are outlined in function of the re-centring and/or dissipation tasks one wants to accomplish. Numerical investigation is presented as well relevant to some possible application.


Title of the Paper: Numerical Analysis of Shape Stability of Rubber Boot

 

Authors: David Samek, Jakub Javorik

Pages: 293-301

Abstract: This paper presents numerical models that are able simulate a buckling of the rubber boot. Rubber boot must be able of a large change of its length. A buckling of cylindrical shape of the boot during this deformation would cause a serious problem. Due to the space limitation in an assembly it is quite difficult to find optimal shape of the boot profile which will be able of the required deformation without the buckling. We have created numerical models that are able to simulate mechanical behavior of the compressed boot including the buckling of the boot with an inappropriate profile. Due to the material of the boot (rubber), a nonlinear hyperelastic material model was used in the analyses. The material constants of this hyperelastic model were obtained from the uniaxial and equibiaxial tests of the boot material. Created numerical models were used to design the optimal shape of the boot which eliminates the risk of the buckling.


Title of the Paper: Base Isolation of Railway Bridges

 

Authors: L. Di Sarno

Pages: 302-309

Abstract: The seismic vulnerability assessment of existing and new lifelines, especially transportation systems, either highways or railways, is becoming of paramount importance in resilient social communities. The structural performance analysis of typical existing bridges for high speed railway is however not an easy task to accomplish. Additionally, the seismic assessment of such as-built bridges tend to emphasize the high vulnerability of the structural systems. In the present analytical work, the earthquake response analysis of typical existing bridges for high speed railway was carried out through linear and nonlinear dynamic analyses using refined finite element three-dimensional lumped-plasticity models and multiple component ground motions. The seismic vulnerability of such bridges was assessed through local and global response quantities. The retrofitting scheme adopted to augment the earthquake performance of the sample bridge structures is the base isolation system comprising either lead rubber bearings or steel dampers. The present study investigates and compares the response of such isolation devices. The outcomes of the numerical analyses proved that the use of base isolation systems lowered significantly the seismic demand, especially on the bridge piers and the foundation systems. Hysteretic metallic devices were found more suitable for the seismic isolation of railway bridges. Additionally, the need to comply with the serviceability requirements is found to be more stringent for the base isolation system in the design of retrofitting schemes for railway bridges than the fulfillment of the ultimate limit state. Further work is ongoing to account for the nonlinear modeling of the rail on the global response of base isolated railway bridges under multiple earthquake components.


Title of the Paper: Effect of Beta Low Irradiation Doses on the Nano-hardness of PBT

 

Authors: M. Ovsik, D. Manas, M. Manas, M. Stanek, M. Bednarik, P. Kratky, A. Mizera

Pages: 310-317

Abstract: This article deals with the influence of different doses of β - radiation on nano-mechanical properties of PBT. The PBT modification was carried out with the aid of β - radiation at different radiation intensities and the resulting properties were measured with the aid of nano-indentation test by the DSI (Depth Sensing Indentation) method. The aim of the article is to find out the influence of the radiation on the nano-hardness of the modified PBT.


Title of the Paper: On the Acoustic Efficiency of Road Barriers: The Reflection Index

 

Authors: Lamberto Tronchin

Pages: 318-326

Abstract: The transportation noise caused by roads and railways is often considered mostly the main cause of noise pollution in urban environment. In order to limit this annoyance, many barriers are realized in several different configurations. These barriers can be characterized by two indices: the reflection index for sound reflection and the insulation index for airborne sound insulation. Both of them can be measured following the method described in CEN/TS 1793-5 standard, based on impulse response measurements employing a pressure microphone. The method mandates for averaging results of measurements taken in different points in front of the device under test and/or for specific angles of incidence, employing the obsolete MLS signal for performing the measurements, which can cause severe artifacts due to nonlinearity and time-variance of the system. Furthermore, the CEN/TS 1793-5 standard presents some geometric problems, which could arise if the barrier does not reach a minimum height or if it has a very rough (scattering) surface. During the reflection index measurement on a barrier of limited height, the reflected sound can be contaminated by the ground reflection, compromising the fairness of the whole result. Also the insulation index can be affected by the height of the noise barrier, since the sound passing above the device under test can become mixed with the sound passing through it. It has been noticed how these practical problems, jointly with the assumption of a surface reflecting specularly in the final formula, can significantly over/under estimate the laboratory values of both the indices. Results of in situ tests based on CEN/TS 1793-5 will be shown in comparison with results obtained through a different approach, based on sound intensity measurements, and with the traditional tests performed in the lab.


Title of the Paper: Tensile Toughness of Irradiated HDPE

 

Authors: J. Navratil, M. Stanek, M. Manas, D. Manas, K. Kyas, A. Skrobak, V. Senkerik

Pages: 327-334

Abstract: Although irradiation of plastics is a well-recognized modification, little research has been undertaken on the possible re-use of such modified materials. In this research paper their possible utilization as fillers into non-irradiated materials is investigated. A powder of recycled irradiated high-density polyethylene (HDPE) was used as filler and granules of non-irradiated neat low-density polyethylene (LDPE) were used as a polymer matrix. Both materials were mixed together in seven concentrations (from 0 % to 60 % of the filler) and test specimens were prepared from the resulting compound by an injection molding technology. Tensile test at two temperatures (ambient – 23 °C and elevated – 80 °C) was performed and influence of the filler on strength, toughness and elasticity was observed. According to measured results there is significant growth of, strength (up to 41 %) and toughness (up to 85 %) and on the contrary significant loss of elasticity (up to 69 %), similar trend is observed at elevated temperature as well. These findings indicate that it is possible to re-use irradiated polymer material after the end of its service life, while taking advantage of the improvement in the resulting mechanical properties.


Title of the Paper: Health Monitoring of Masonry Structures in the Rione Terra Archeological Area

 

Authors: O. Corbi, M. Candela

Pages: 335-342

Abstract: In the paper one refers to an archeological area affected by significant tectonic phenomena, i.e. the Rione Terra in Pozzuoli. The task of preserving the standing structures, mainly made of masonry material, or those requiring a partial or total reconstruction, pushes towards the adoption of some effective health monitoring of the masonry, which allows to follow the response of old and new fabrics according to the occurring environmental changes and events. To this purpose some special instrumented masonry elements are referred to able to couple the structural and the monitoring needs.


Title of the Paper: Numerical Experimenting of Combustion in the Real Boiler of CHP

 

Authors: A. Askarova, S. Bolegenova, S. Bolegenova, A. Bekmukhamet, V. Maximov, M. Beketayeva

Pages: 343-352

Abstract: Physical and chemical processes occurring in the combustion chamber are fast and complete oxidation of the fuel (in this case coal) by atmospheric oxygen. These processes occur at high temperatures, accompanied by a large energy release due to chemical reactions and the concentration of all of reacting substances. Mathematical description of the processes taking place in the steam generators, furnaces and reactors with modern computer algorithms, using computer programs allow to solve problems for specific installations.


Issue 4, Volume 7, 2013


Title of the Paper: Effect of a Multiscale Factor on the Axisymmetric Vibrations of Composite and Layered Cylindrical Shells with Cracks

 

Authors: Larissa Roots

Pages: 353-361

Abstract: Vibrations of circular cylindrical shells made of layered composite materials are considered. The shells are weakened by circumferential cracks. The influence of circumferential cracks with constant depth on the vibration of the shell is prescribed with the aid of a matrix of local flexibility coupled with the coefficient of the stress intensity known in the linear elastic fracture mechanics. Effect of a multiscale factor on the axisymmetric vibrations of composite and layered cylindrical shells with cracks is considered. Dependence of the Young’s modulus from quantity of molecular layers of a cylindrical shell is investigated. Numerical results are presented for the case of the shell with one circular crack.


Title of the Paper: Solutions of Beams, Frames and 3D Structures on Elastic Foundation Using FEM

 

Authors: Karel Frydrýšek, Roland Jančo, Horst Gondek

Pages: 362-369

Abstract: This paper contains numerical methods and approaches used in the solution of plane beams and frames and 3D structures on an elastic foundation. In the first case, the solution uses beam element BEAM54 in the program ANSYS and the derivation of the stiffness matrix for this element is presented. The second approach uses a beam element in a combination with a contact element with the description of the derivative of the stiffness matrix applied for the frame on elastic foundation. Both solutions are compared with theoretical solution. The influence of the number of divisions for the beam element on the accuracy of the solution is shown. There are also presented some other application of structures on elastic foundation (biomechanics & traumatology – external fixators for treatment of complicated bone fractures, mining industry - pressure distributions in the contact between mining supports and foot-wall, rack-railway and drop-in test as a problem of 3D body on elastic foundation).


Title of the Paper: Visco-Re-Centring Energy Dissipating System for Seismic Protection of Framed Buildings

 

Authors: Felice Carlo Ponzo, Antonio Di Cesare, Domenico Nigro

Pages: 370-378

Abstract: Energy Dissipating Bracing (EDB) system using both Shape Memory Alloy (SMA) and viscous damper (VD) devices has been considered in order to control seismic vibrations on buildings. The basic mechanical properties of the SMA+VD were used in order to recentre the gravity-load resisting system to its initial configuration at the end of the seismic event and to increase the energy release during the seismic motion. A performance based design procedure for the evaluation of the mechanical characteristics of both SMA and VD devices, starting from an equivalent Hysteretically Damped (HD) EDB designed for the same inter-storey target drift, was proposed. In order to verify the effectiveness of the design method and the performances of the system a parametric study was developed considering numerical nonlinear time history analysis and an extensive program of dynamic experimental tests, has been carried out at the Structural Laboratory of the University of Basilicata considering a 1:1.5 scaled three-dimensional steel frame within the JetPacs project (Joint Experimental Testing on Passive and semi-Active Control Systems). In this paper the main results obtained by numerical nonlinear time history analysis (NTHA) are compared with experimental ones.


Title of the Paper: A Study of Run onto the Wheel Contact Crane Stops of Tower Cranes

 

Authors: Vadim Rabey

Pages: 379-384

Abstract: The processes of load-lifting crane’s interactions with impact and non-impact end stops are still at the research level due to the simplified approaches that are used. The use of the wheel contact crane stops to smoothly slow tower cranes has demonstrated an alarming tendency to run over the wheel contact crane stops, and additionally, potential decreases in the stability of the cranes may result. The existing standards for load-lifting cranes and the scientific studies devoted to this problem have prevented the evaluation of the spatial behavior of tower cranes when cranes run onto the wheel contact crane stops due to flat computational models with few degrees-of-freedom. The present work was devoted to a study of the interaction of tower cranes with the wheel contact crane stops based on a numerical method analysis, i.e., a finite element method. With the help of a finite element model reflecting the actual metal construction of the tower crane, a series of computational experiments were performed to determine the theoretical spatial behavior of a tower crane when the crane runs onto the wheel contact crane stops. This behavior is important to determine the actual stability of tower cranes.


Title of the Paper: Computer Modeling of Heat Balance in Counterflow Tube Heat Exchanger

 

Authors: H. Charvátová, D. Janáčová, R. Drga, O. Líška, V. Vašek, M. Zálešák

Pages: 385-392

Abstract: The paper deals with mathematical modeling of heating and cooling of fluids in heat exchanger by use software MAPLE. It describes computer teaching application programmed in MAPLE for computation of temperature curves derived from mathematical model of heat balance in the thermal isolated counterflow tube heat exchanger. The accuracy of data computed by MAPLE were verified by simulation with use commercial software COMSOL MULTIPHYSICS. The obtained results are also presented.


Title of the Paper: About the Structural Restoration of the S. Domenico’s Monastery in Naples

 

Authors: O. Corbi, M. Candela

Pages: 393-400

Abstract: In the paper one focuses on the need of coupling the building site experience with a deep theoretical knowledge, which is of primary importance especially when dealing with masonry fabrics, and in particular with constructions with an historical or monumental relevance. The case of the monumental complex of S. Domenico Maggiore in the Campania Region is focused on, by presenting some intervention strategy adopted for increasing the seismic vulnerability of the main Chapter Hall.


Title of the Paper: The Computational Fluid Dynamics (CFD) Study of Fluid Dynamics Performances of a Resistance Muffler

 

Authors: D. Tutunea, M. X. Calbureanu, M. Lungu

Pages: 401-408

Abstract: The exhaust pollution has become one of the important problems of environment pollution with applications in automobile industry, and the exhausted muffler has been paid attention to improve the performance of engines. Computational Fluid Dynamics (CFD) method was used to explore the aerodynamic performance of the muffler. The dimensions of muffler design should be limited in the demand of assembly with simple structure. Resistance muffler research relates with the fields of acoustics, fluid dynamics, heat transfer and mechanism design. The author simulated the field by numerical method with Cosmos Flow and analyzed the effect which the internal flow field has on the performance of the muffler, which may be a credible guidance of the muffler structural design. With this method the pressure distribution in the muffler is simulated and the pressure loss is predicted for the structure modification. The experiment results verify that the assembly performance of the muffler modified is better than the original muffler.


Title of the Paper: Comparison of Mechanical Properties of Injection Molded and Compression Molded Rubber Samples

 

Authors: A. Skrobak, M. Stanek, K. Kyas, D. Manas, M. Manas, M. Reznicek, V. Senkerik

Pages: 409-416

Abstract: This article demonstrates what influence has a change in production technology on mechanical properties of rubber testing samples. It compares two basic production technologies – compression molding and injection molding. The aim of this research is to show and evaluate to what extent the mechanical properties are influenced by the used production technology and to quantify this potential difference on the basis of mechanical tests.


Title of the Paper: Shape Optimization of Rectified Brick Blocks for the Improvement of the out-of-Plane Behavior of Masonry

 

Authors: Dora Foti

Pages: 417-424

Abstract: In this article the numerical and experimental study on different brick blocks for masonry structures or infill walls is developed. The blocks are rectified ones and are shaped in the way to get a better behavior with respect to out-of-plane forces such as the seismic ones. In particular the distribution of the forces in the cross section is defined in function of the shape of the holes. The stress state in the block is investigated by a finite element analysis and the results are compared with the experimental tests carried on individual blocks.


Title of the Paper: Design, Construction and Evaluation of a New Laboratory Convective Dryer using CFD

 

Authors: D. A. Tzempelikos, A. P. Vouros, A. V. Bardakas, A. E. Filios, D. P. Margaris

Pages: 425-434

Abstract: In order to overcome the lack of experimental data in the open literature and the necessity to validate numerical models, as well as increase the efficiency of the drying process, a new laboratory convective (LC) dryer has been designed, constructed and equipped with an integrated measurement and automated control instrumentation. The main sections of the LC dryer, which can be arranged for operation in a closed or open circuit mode through manually controlled dumpers, are the vertical flow drying chamber, the tube heat exchanger, the thermal boiler and finally the fan - motor with a smooth speed control unit. The experimental facility tested and monitored the moisture content removal of horticultural and agricultural products. The current paper outlines the methodology applied for the design and optimization of the LC dryer, which has been achieved through the analysis of the flow field by means of computational fluid dynamics (CFD). The prediction of the 3d flow problem was accomplished through the solution of the steady-state incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations with the incorporation of the standard k-ε turbulence model. The measurement and control instrumentation with the inclusion of the innovative, pc-controlled, 3d traverse system that serves detailed surveys of the temperature and velocity inside the drying chamber, are also discussed. The performance test and evaluation of the LC dryer was conducted using quince slices as a test material at an average temperature of 60oC and air at 2 m/s into the drying chamber.


Title of the Paper: Properties of Irradiated PA12 by Accelerated Electrons

 

Authors: A. Mizera, M. Manas, Z. Holik, D. Manas, M. Stanek, J. Navratil, M. Ovsik, M. Reznicek

Pages: 435-442

Abstract: Radiation processing involves the use of natural or manmade sources of high energy radiation on an industrial scale. The principle of radiation processing is the ability of high energy radiation to produce reactive cations, anions and free radicals in materials. The industrial applications of the radiation processing of plastics and composites include polymerization, cross-linking, degradation and grafting. Radiation processing mainly involves the use of either electron beams from electron accelerators or gamma radiation from Cobalt-60 sources. The PA12 polyamide 12 tested showed significant changes of temperature stability and mechanical properties after irradiation. From this point view, new applications could also be seen in areas with service temperatures higher than their former melting point. The comparison of the temperature stability and mechanical properties of irradiated and non irradiated PA12 is presented in this paper.


Title of the Paper: Application of Response Surface Methodology for Modeling the Properties of Chromite-based Resin Bonded Sand Cores

 

Authors: B. Surekha, D. Hanumantha Rao, G.Krishna Mohana Rao, Pandu R Vundavilli, M. B. Parappagoudar

Pages: 443-458

Abstract: Resin bonded sand cores are increasingly used in applications where high dimensional accuracy is required. The quality of the cast products produced using this system mainly depends on the properties of the core, namely compression strength, shear strength, tensile strength and permeability, which in turn depends on the process parameters, such as amount of resin, amount of hardener, number of strokes and curing time. The relationships of these input parameters with the properties of the core are complex in nature. In the present paper an attempt has been made to establish the said input-output relationships with the help of response surface methodology. A three level central composite design is utilized to conduct the experiments. Surface plots are used to study the effects of amount of resign, amount of hardener, number of strokes and curing time on the responses. Moreover, analysis of variance test has been conducted to determine the statistical adequacies of the developed models. The prediction accuracy of the non-linear models have been tested with the help of twenty test cases, and found reasonably good accuracy.


Title of the Paper: Shaking Table Testing for Structural Analysis

 

Authors: I. Corbi, Z. T. Rakicevic

Pages: 459-466

Abstract: In the paper the dynamic behavior of structures behaving like rigid blocks and a multi-plane steel frame are considered in order to study the most appropriate control system for vibrations. In the case of the rigid blocks the motion under pure rocking is analyzed and the problem is addressed of attenuation of the dynamic response by means of dampers based on a liquid mass. In details, one refers to rigid systems with unilateral constraints exhibiting pure rocking motion under dynamic load; this application is pretty significant since it embraces a wide variety of physical objects; moreover the coupling with dissipating liquid devices of rigid blocks is rarely treated in literature. In the case of the steel frame a tuning procedure is elaborated for adjusting multiple control variables, such as gains, lead terms, and notch filters, which allows to obtain unitary gain of the transfer function between command-reference and feedback signal within the frequency bandwidth of interest. As an additional tool to fixed control techniques, the Adaptive Control Technique is used when high fidelity in signal reproduction is required.


Title of the Paper: The Finite Element Analysis of the Thermal Stress Distribution of a Piston Head

 

Authors: M. X. Calbureanu, R. Malciu, D. Tutunea, A. Ionescu, M. Lungu

Pages: 467-474

Abstract: Computer aided engineering (CAE) tools allow engineers to design product and to simulate these designs for residual stress, structural response, thermal effects, pre-processing and post processing fatigue on the automotive component. The main purpose of the preliminary analyses presented in the paper was to compare the behavior of the combustion engine piston made of aluminum alloys. The paper describes the mesh optimization with using finite element analysis technique to predict the higher stress and critical region on the component. As initial condition we considered a temperature on the head piston of 330°C and a total pressure of 5 MPa. There were studied two cases, a piston head and a piston, pin and connecting rod.


Title of the Paper: Fatigue Tests of Assembly Joints of Truss Main Girders of Newly Developed Temporary Footbridges

 

Authors: Marcela Karmazínová, Pavel Simon

Pages: 475-483

Abstract: The paper is focused on the problems of the actual fatigue resistance of assembly joints of the temporary footbridge for pedestrians and cyclists, which is being newly developed within the framework of the applied research project of the Technological Agency of the Czech Republic. The necessity of the development of a new temporary footbridge has been invoked by the lack of such constructions in a practice, both in the case of flood situations, and also as the site facilities, for pedestrian traffic crossing on the construction sites of bridges or other structures. Within this work the attention is mainly paid to the static and structural design, in particular to the harmonization of aspects of static solution and structural detailing, to achieve the efficient design. In parallel, two types of the footbridge are being developed, both ones with a lower deck, truss main girders and bracings. The first structure, so-called “short footbridge” with a very small self weight, can reach up to 18 m span; the second structure, “long footbridge” with a normal self weight, can reach up to 36 m span. This paper mainly presents the basic information on the actual behaviour of assembly joints of the structure, if subjected to the fatigue loading actions. The content of the paper is focused on the experimental verification of fatigue parameters of the most important structural details and joints. Within the framework of experimental programme, the fatigue tests of exposed details and joints of the truss main girders have been performed. In this paper, the performance of fatigue tests including elaboration and evaluation of their main results are presented.


Title of the Paper: Application of EMD-Based TVAR Model for Modal Analysis of Semi-Submersibles

 

Authors: Edwar Yazid, M. Shahir Liew, Setyamartana Parman, V. J. Kurian, C. Y. Ng

Pages: 484-491

Abstract: This paper presents a technique for using a parametric approach for modal properties estimation of a floating offshore structure. The technique utilizes empirical mode decomposition (EMD)-based time-varying autoregressive (TVAR) model, which is an extended form of the well-known AR model. Input for TVAR model is surge motion as system response, obtained experimentally from a scaled 1:40 model of a prototype semi-submersible. By utilizing the advantage of time-varying spectrum generated from TVAR model, estimation of the modal properties is carried out in the time-frequency plane via poles technique under different random wave spectrum. The results show that the modal frequency and its corresponding damping ratio for surge motion either in low frequency or wave frequency region can be estimated well. The Stochastic subspace identification method and free-decay test of the semi-submersible prototype are taken as benchmark.


Title of the Paper: Uncertainties in Acoustic Measurements: A Case Study

 

Authors: Lamberto Tronchin

Pages: 492-499

Abstract: A new method for recording the spatial properties of a soundfield, or for generating a synthetic three-dimensional soundfield, is described. The spatial distribution of sound waves passing at a point in space is sampled by means of a number of virtual directive microphones, covering the surface of a sphere. This corresponds to a discretization of the spatial information, which is exactly the spatial equivalent of the PCM sampling of a waveform. Moreover, the influence of the height of the microphone in the calculation of the acoustic parameters was analysed. The measurements were repeated at different height and different position on a transversal line in the theatre, and statistically analysed


Title of the Paper: Micro-hardness of Glass Fiber-Filled PA6 Influenced by Beta Irradiation

 

Authors: M. Ovsik, D. Manas, M. Manas, M. Stanek, M. Bednarik, P. Kratky, A. Mizera

Pages: 500-507

Abstract: The presented article deals with the research of micro-mechanical properties in the surface layer of modified Polyamide 6 filled by 30% of glass fibers. These micro-mechanical properties were measured by the DSI (Depth Sensing Indentation) method on samples which were non-irradiated and irradiated by different doses of the β - radiation. The purpose of the article is to consider to what extent the irradiation process influences the resulting micro-mechanical properties measured by the DSI method.


Title of the Paper: Effect of Location of Cutout and Plate Aspect Ratio on Buckling Strength of Rectangular Composite Plate with Square/rectangular Cutout Subjected to Various Linearly Varying In-Plane Loading using FEM

 

Authors: A. Lakshmi Narayana, Krishnamohana Rao, R. Vijaya Kumar

Pages: 508-517

Abstract: A numerical study using finite element method (FEM) has been carried out to study the effect of plate aspect ratio and location of the cutout on the buckling behavior of a sixteen ply quasi-isotropic graphite/epoxy symmetrically laminated rectangular composite plate [0°/+45°/-45°/90°]2s with square and rectangular cutout subjected to various linearly varying in-plane compressive loads. Further, this paper addresses the effects of size of square/ rectangular cutout, location of the cutout, plate length/thickness ratio(a/t), boundary conditions on the buckling bahaviour of symmetrically laminated rectangular composite plates subjected to various linearly varying in-plane compressive loading. The results show that the buckling loads of rectangular composite plates with rectangular/square cutout subjected to various linearly varying in-plane loads are decreased by increasing the plate aspect ratio (a/b) and length/thickness (a/t) ratio irrespective of cutout shape, size and boundary conditions. It is noticed that the boundary conditions, various linearly varying in-plane loads, , aspect ratio (a/b) and length/thickness (a/t) ratio have a substantial influence on buckling strength of rectangular composite plate with square/ rectangular cutout. It is observed that the location of the square/rectangular cutout has substantial influence on buckling strength of rectangular composite plate irrespective of size and shape of cutout, orientation of cutout, plate aspect ratio (a/b), plate length/thickness ratio(a/t), boundary conditions and various linearly varying in-plane compressive loads.


Title of the Paper: Seismic Protection of Civil Buildings by Visco-Elastic Magneto-Rheological Fluids

 

Authors: Ottavia Corbi, Rui Carneiro de Barros

Pages: 518-525

Abstract: The objective of mitigating the dynamic vibrations in civil buildings induced by seismic events may be considered of primary interest for safety and safeguard purposes. Mostly the need of realizing dissipative devices able to couple economy in the energetic supply of the control system and effectiveness in the mitigation of the dynamic effects pushes towards the adoption and the set up of new strategies, alternative to more classical control devices. In the paper one focuses on the possibility of mitigating the effects induced in civil structures by earthquakes by means of Magneto-Rheological (MR) dampers. Modeling as well as design issues are discussed, together with some numerical and experimental investigation demonstrating the potentials of such devices.


Title of the Paper: Microhardness of Electron Beam Irradiated Polycarbonate

 

Authors: D. Manas, M. Ovsik, M. Manas, M. Stanek, P. Kratky, A. Mizera, M. Bednarik

Pages: 526-533

Abstract: Experimental study deals with the influence of beta radiation on the micromechanical properties of the surface layer of polycarbonate. When subjecting the polycarbonate to beta radiation, the structure as well as the surface layer show structural changes (crosslinking, degradation). The injected specimens were irradiated by doses of 0, 33, 66, 99, 132, 165 and 198 kGy. Irradiation of the specimens caused changes in the surface layer similar to the process of nitriding or cementation in metals. There was an improvement in some micromechanical properties of the surface layer of polycarbonate. The improvement/deterioration of micromechanical properties of surface layer of polycarbonate measured by the instrumented microhardness test is the content of this experimental study.


Title of the Paper: Natural Convection in Square Cavities with Three Active Source Configurations

 

Authors: G. Nardini, M. Paroncini, R. Vitali

Pages: 534-542

Abstract: Laminar natural convection in a two-dimensional square cavity of side length H due to some sources on the vertical sidewalls was experimentally and numerically investigated. Main efforts were focused on the size of the sources on the fluid flow and heat transfer characteristics. The test cell is a square cavity filled with air. Three cases are investigated: in the first case there are two identical active sources (hot and cold) on the side walls extended for the entire length H of the cell, in the second one there are two active sources of size H/2 and in the third one there are four sources of size H/4. The experimental study was carried out through holographic interferometry in order to obtain the average Nusselt numbers at different Rayleigh numbers and the numerical study was carried out through the finite volume code Fluent 12.1.4. The temperature distributions in the air and the heat transfer coefficients measured experimentally are compared with the numerical results. The isothermal lines, stream functions, velocity maps and average Nusselt numbers show the effect of the different heating size of the side walls to explore the fundamental fluid flow and heat transfer characteristics for natural convection in two-dimensional square enclosures.