Paper Title, Authors, Abstract (Issue 1, Volume 1, 2007)

Pages

Investigation on Heat Transfer in Quadrangular Plate under Vertical or Horizontal Crack Using FDM
M.M Azhdari Moghadam

Abstract: In this study an efficient method for distribution of temperature in quadrangular plate is developed. Heat transfer is transient which by that one can gain distribution of temperature of plate in various times. Temperature of plate is calculated using FDM. Applying transient heat transfer equation and comparing with results of ANSYS Software, excellent agreement is shown. Then equations to calculate temperature in cracked plate in all of regions of plate were derived. The transient temperature distribution of finite plate with insulated cracks are compared with an non-cracked plate and discussed in detail.
 

Formation of High Wear Resistance Surface Layers using Metals Powder
A. Regita Bendikiene, B. Petras Ambroza and C. Lina Kavaliauskiene

Abstract: Submerged arc surfaced layers, obtained using halfautomatic welding device, were investigated in the present work. Steels Ct3, 45, Y8, X12M, P6M5 (GOST) were deposited under the flux AMS1 (chemical composition: more than 50 % of SiO2 and MnO) mixed with chromium, molybdenum, graphite powder and powder of inoculant SiCaBa. Changing quantity of inoculant powder added to the flux, layers of various structure and mechanical properties were composed; while feeding of low carbon wire of 1.2 mm in diameter were continuously delivered into the welding zone. Initial and secondary hardness of layers, alloyed with chromium, molybdenum, manganese and silicon, was increased by powder of the SiCaBa. The opportunity of structural steel deposition using milling chips of high speed steels was estimated. Chips spread on the surface were fused under the flux AMS1, when arc was struck between welding wire and the substrate; layers were alloyed with alloying elements, presented in the chips and flux.
 

Solution of some Differential Equations of Reversible and Irreversible Thermodynamics
Stasys Bockus

Abstract: There are presented the analytical solutions of differential equations of transfer laws in the body with n binding degrees of freedom of thermodynamics describing stationary and non-stationary processes in this paper. It is suggested that potential fields are one-, two- and three-dimensional. Laplace’s differential equations are analysed in Cartesian, cylindrical and spherical coordinates taking into account various boundary conditions. The solutions considerably facilitate the numerically methods put into solving of some Laplace’s differential equations and increase the possibility of employing these equations in thermodynamics of stationary and non-stationary processes.
 

Interaction of External Vortical and Thermal Dis-turbances with Boundary Layer
Sergey А. Gaponov

Abstract: Longitudinal structures generated by external vortical and thermal waves in subsonic and supersonic boundary layers are studied in the paper. Particular attention is paid to the boundary conditions at the boundary layer outer edge. It was established that longitudinal velocity and mass flow disturbances inside the bound-ary layer can exceed the amplitude of external vortical wave in several times. Excitation efficiency decreases with increasing Mach number. Influence of thermal external waves on the flow structure in the boundary layer is much weaker.
 

    Paper Title, Authors, Abstract (Issue 2, Volume 1, 2007)

Pages

Design of a low cost electronic control system for an articulated robot arm
J. J. Rubio Ávila, R. Alcántara-Ramírez, J. Jaimes-Ponce, and I. I. Siller-Alcalá

Abstract: With the continuous growth Mecathronics has had in the past few years, public universities have seen the necessity of developing its own prototypes for the application of Modern and Classical Control laws. The development of such Mechatronical systems involves electronic conditioning circuits of signals as well as power electronic systems for the adequate control of the traction elements of the mechanical system. This article presents the design and the construction of electronic systems for the control of an articulated robot developed for research and teaching in subjects related with instrumentation and control. The main advantage of this design is its lower cost than commercial equipments with similar characteristics, an extra advantage to this, is the fact that the maintenance as well as future modifications can be done in a quick and easy way.
 

Time-Frequency Distribution of Encountered Waves Using Hilbert-Huang Transform
Ming Li, Xue-Kang Gu, and Pei-Wei Shan

Abstract: Time-frequency distribution (TFD) of signals gains increasing applications in various areas of sciences and engineering for processing non-stationary signals and nonlinear signals. This paper presents our work of TF analysis of encountered wave signal in ship science using the Hilbert-Huang transform (HHT). The results in this paper exhibit that the HHT based TFD of encountered wave signal has better resolution in comparison with those resulted from the traditional methods, such as short-time Fourier transform (STFT), wavelet transform (WT) TFD, and Choi-Williams TFD.
 

Isentropic Sound Waves Propagation in a Tube Filled with a Porous Media
H. M. Duwairi

Abstract: A rigid frame, cylindrical capillary theory of sound propagation in porous media that includes the nonlinear effects of the Forchheimer type is laid out by using variational solutions. It is shown that the five main parameters governing the propagation of sound waves in a fluid contained in rigid cylindrical tubes filled with a saturated porous media are shear wave number, s = R ρ ω / μ , reduced frequency parameter, k = wR a , porosity, ε , Darcy number, Da = R 2 K , and Forchheimer number, s F C * = 2C . The manner in which the flow influences the attenuation and the phase velocities of the forward and backward propagating isentropic acoustic waves is deduced. It is found that the inclusion of the solid matrix increases wave’s attenuations and phase velocities for both forward and backward sound waves, while increasing the porosity and the reduced frequency number decreased attenuation and phase velocities. The effect of the steady flow is found to decrease the attenuation and phase velocities for forward sound waves and enhance them for the backward sound waves.
 

Wind flow pressure load simulation around storage tanks using SGS turbulent model
S.R. Sabbagh-Yazdi, N.E. Mastorakis, and F. Meysami

Abstract: The equation of continuity is simultaneously solved with the two equations of motion in a coupled manner by application of the pseudo compressibility technique for the steady state problems. The set of two dimensional for the incompressible fluid is combined with a SGS (Sub-Grid Scale) eddy viscosity turbulence model. The discrete form of the two-dimensional flow equations are formulated using the Galerkin Finite Volume Method for unstructured mesh of triangular cells. Using unstructured meshes provides the merit of accurate geometrical modeling of the curved boundaries of the tanks. Satisfactory results are obtained by the use of proper boundary conditions. The accuracy of the model for the solution flow around circular cylinder at supercritical Reynolds number is assessed by comparison of computed results with experimental coefficient of pressure measurements. Then, the model is applied to simulate the changes in the pressure distributions due to the wind flow on two storage tanks in tandem arrangement.
 

    Paper Title, Authors, Abstract (Issue 3, Volume 1, 2007)

Pages

Multi-layer simulation of circulations in an artificial shallow lake
S.R. Sabbagh-Yazdi, N.E. Mastorakis, and H. Arabi

Abstract: In the current study a multi layers numerical model is introduced for modeling shallow water flows. The model numerically solves conservative equations of continuity and motions in order to compute water depth and velocity patterns in each layer. The model can consider the elevation variation of upper layers and bed and wall geometric complexities and resistances. It can also consider the effect of wind as well as evaporation and rain on surface layer. The governing equations are discretized using vertex base overlapping finite volume method in triangular unstructured meshes. For stabilizing the explicit solution process, artificial viscosity formulations are adopted for the unstructured meshes in such a way that preserves the accuracy of numerical results. The accuracy of results of present multi-layer flow solver is assessed by simulating wind induced flow in a circular basin and comparison of computed results with the results of previous research works. The application of the model to a real world environmental problem is presented as well.
 

Dynamic Modeling of Hermetic Reciprocating Compressors, Combining Multibody Dynamics, Finite Elements Method and Fluid Film Lubrication
Edgar A. Estupiñan and Ilmar F. Santos

Abstract: A multibody dynamic model of the main mechanical components of a hermetic reciprocating compressor is presented in this work. The dynamics of the mechanical components are described with help of Dynamics of Multibody Systems (rigid components) and Finite Element Method (flexible components). Some of the mechanical elements are supported by fluid film bearings where the hydrodynamics interaction forces are described by the modified Reynolds equation. The system of nonlinear equations is numerically solved, taking into account the lateral and tilting vibration of the center of the crank. Particularly, in this study the main focus is on the lubrication behavior of the upper and lower bearings of the crankshaft, considering hydrodynamic lubrication conditions. The behavior of the orbits and the pressure distribution in the journal bearings is presented giving some insights into design parameters, such as, maximal fluid film pressure, minimum fluid film thickness and maximum vibration levels.
 

Integration of I-kaz Coefficient and Taylor Tool Life Curve for Tool Wear Progression Monitoring in Machining Process
Nuawi M. Z., Lamin F., Nor M. J. M., Jamaluddin N., Abdullah S., Nizwan C. K. E.

Abstract: This paper presents a new statistical-based method of tool wear progression monitoring in turning process, called Integrated Kurtosis-based Algorithm for Z-filter Technique, I-kaz. The I-kaz method calculates the related coefficient for the measured machining signals. The input data of the I-kaz method was acoustic signal that was generated during machining process, which was in the ultrasonic frequency range. Ultrasonic signal was measured as a tool of sensing element to study the flank wear on the cutting tool edge at various cutting parameters. The flank wear progression was monitored by the value of the I-kaz coefficient integrated with the Taylor Tool Life curve. The resulting trend of I-kaz coefficient on the flank wear rate in the Taylor Tool Life curve was effective in observing the flank wear progression. In addition, the technique was reliable for both low and high speed cutting that could help to predict tool life.
 

    Paper Title, Authors, Abstract (Issue 4, Volume 1, 2007)

Pages

Design and Fabrication of a Delta Wing Micro Aerial Vehicle
Sepideh Afshar, Aghil Yousefi-koma, Hossein Shahi, Donya Mohammadshahi, Hesam Maleki

Abstract: Design and fabrication of a bodyless MAV is presented in this paper. Bodyless MAVs take advantage of more lift and less drag. A triangular wing is chosen to this end and two models are fabricated to investigate winglet effect in aerodynamic properties, especially roll and yaw stability. Results show that this wing provides better results than conventional models. Moreover, the model proves good maneuverability characteristics. It is also shown, in the designed MAV, lack of winglets results in stability reduction.
 

Design, Fabrication and Hydrodynamic Analysis of a Biomimetic Robot Fish
Donya Mohammadshahi, Aghil Yousefi-koma, Shahnaz Bahmanyar, Hassan Ghassemi, Hessam Maleki

Abstract: The purpose of this paper is design, fabrication and hydrodynamic analysis of a biomimetic robot fish that is fabricated at Advanced Dynamic and Control Systems Laboratory (ADCSL), University of Tehran. In order to fabricate a fish-like swimming robot, comprehensive hydrodynamic and structural analysis was performed. All of these followed by extensive study of the biology of the fish especially their maneuverability and propulsion system. Swimming principle is achieved from Carangiform swimming mode. This is the swimming mode of fish that use their tail and peduncle for propulsion. Employing servomotors, oscillating mechanism, latex shell, and plexy tail, a tiny model of robot fish has been fabricated and tested. Experiments show smooth, repeatable, and controllable motion of the robot fish. In order to evaluate hydrodynamic forces, Computational Fluid Dynamic (CFD) method was used besides test results. It provides helpful results to optimize performance parameters in the process of design and fabrication.
 

Simulation of Three Dimensional Progressive Damage in Composite Laminates
Ali Evcil

Abstract: A three-dimensional, non-linear finite element code was developed to simulate the progressive damage of composite laminates in three dimensional space and to analyze the failure propagation and mode of failure around composite to metal joints. The code includes large displacement theory, isotropic and orthotropic material properties and a contact algorithm based on transformation matrix. A progressive damage model was implemented to predict the extent and the failure modes of the internal damage in composite laminates as a function of applied load and to stimulate the three-dimensional response of composite laminates from initial loading to final collapse. Hashin failure criteria was used together with the fiber-matrix shear failure and Yeh delamination criterion and material properties were degraded according to the mode of failure. 3D non-linear finite element formulation was tested with a 45° bend cantilever provided with a concentrated tip load and a solid sphere with radius R = 1.0 cm compressed diametrically by two parallel rigid plates was modeled to verify the contact algorithm. The progressive damage algorithm was verified using a clustered crossply [06/906]s laminate with a hole under compressive in-plane load. The results determined were found to be in good agreement with the experimental results with a deviation of as low as 2.6 % from the average. Pinned joint failure analysis of same cross-ply [06/906]s laminate was conducted using two different geometries and net-tension, bearing, shear-out and mixed modes of failure of the joined was examined according to the progression of the damage.
 

System Parameters Identification in a General Class of Non-linear Mechanical Systems
D’Ambrosio S., Guarnaccia C., Guida D., Lenza T.L.L., Quartieri J.

Abstract: The problem of system identification and parameters monitoring for a general class of non-linear systems is discussed together with the introduction of a new method based on Lie series expansion. In order to use this approach, the system features must be modeled by analytic or sufficiently smooth functions of the state variables, including the time parameter. The method uses the Lie differential operator representations. The solution obtained are expressed in the form of analytical power series including the system parameters. The information carried by these solutions is sufficiently complete and provides good estimates of the system parameters. In this paper, a mechanical system made by a reverse pendulum jointed to a sliding mass is studied. The identification of parameters of this system is the main aim of this simple application. Since the motion equations can be numerically solved, a comparison between theoretical and experimental values of parameters is performed. This comparison is based on the minimization of the difference between numerical and approximated solution, the last obtained by Lie series.
 

Experimental and theoretical analysis of the dynamical behavior of the technological equipment foundation
Adrian Leopa, Silviu Nastac

Abstract: The aim of the work presented here was to investigate the possibility of using hangs in the non-linear vibration characteristics to detect damage in mechanical structure. The nonlinearities were detected by examining the changes in time and frequency response, in over time (and hence over amplitude of vibration). These analyses were made by comparison for the two considerate hypotheses: linear and nonlinear elastic characteristic of the viscous-elastic system.
 

Infinitesimal Equivalence between Linear and Curved Sources in Newtonian Fields: Application to Acoustics
J. Quartieri, L. Sirignano ,C. Guarnaccia

Abstract: The equivalence between the vectorial field produced by a scalar linear source and the one produced by a scalar curved source is proved in the centre of the circumference which contains the curved source, if this circumference is tangent to the line of the linear source. Since this equivalence is true already at the infinitesimal level, many consequences come out. Applications of this result can be highlighted in electrostatics and in acoustics, since these fields fulfil the above requirement. In particular, in acoustics, the problem of isolated receivers along a high velocity rail line can be approached by means of studying the equivalent curved source.
 

Analysis of seepage with nonlinear permeability using least square finite element and finite difference methods
M. M. Toufigh, M. H. Bagheripur, A. Bazrafshan M.

Abstract: Free-surface seepage problems have been attracting interests of many engineers and mathematicians due to the strong non-linearity as well as the importance in designing the hydraulic structures, such as embankments, canals, and earth and rock-fill dams. Free-surface seepage flow is governed by an elliptic partial differential equation when steady state flow conditions have been considered. In most geotechnical analyses, soil properties are assumed to be spatially and temporally invariant and thus, average property values are used. In reality, however, these soil parameters usually vary from point to point (heterogeneous) and even at one point they may have different values in various measured directions (anisotropy). Moreover, these parameters may vary in time while a geotechnical process is occurring due to an external influence such as surface pressure or due to the change of chemical compositions. Therefore in this research, the coefficients of permeability are assumed to vary in terms of geometry, external load influences and the effect of head variation in the system and the resulted nonlinear seepage problem is solved using Least Square Finite Element Method and Finite Difference Method. The seepage Problem is analyzed for two cases of variable and constant coefficients of permeability. The effect of a variable coefficient of permeability may not be significant on small dams, but as the height of the dam increases, the effect becomes more considerable. It is believed that a variable permeability analysis such as the one described in this paper should be taken into account.