bluuebunny/crossref_metadata_2025 huggingface dataset:
How Geometrical Tolerances Affect the Measurement of Reciprocal Alignment of Two Different Assemblies: A Case Study
Authors: Vetturi David , Lancini Matteo , Bodini Ileana
Published: January 2011

Often a designer has the problem to apply a suitable system of geometrical and dimensional tolerances to an assembly. The right solution is not unique, in fact it depends on the chosen parameters. If the tolerances have to be optimized, some important parameters have to be taken into account, e.g. the efficiency of each prescription, or if this last is reachable, or it can be verified and how much the realization costs. The authors opinion is that a statistical approach based on the Monte Carlo Method is very useful when the tolerances chains are complex. This paper shows an application of this method in order to verify the functional alignment between two assemblies and a critical analysis of the uncertainty in phase both of the component design and test. This study has been developed thanks to the strict requirements imposed by ESA (European Space Agency) on the components that Thales Alenia Space has to realize within the LISA Pathfinder experiment. The very critical aspect of this work is to reciprocally align two cylindrical elements of two different assemblies. The specifications require 100 μm as maximum linear displacement and 300 μrad as maximum angular displacement. Moreover this prescriptions have to be verified also when the two elements are independently moving. To be able to reach such strict accuracy level the components have been assembled in an ISO 100 class cleanroom and the work space was a 3D Coordinate-Measuring Machine (CMM). The cylindrical elements have a 10 mm diameter, so the value of the measurement uncertainty associated with the alignment check is fundamental. Starting from the different uncertainty sources, the measurability and verifiability of the alignment have been considered and evaluated. The overall uncertainty has been assessed by numerical simulations which have taken into account the dimensional, geometrical and form tolerances as well as the instrumental uncertainty of the 3D CMM. This estimation has been positively validated by a session of repeated measurements. Numerical simulations have also allowed performing a sensitivity analysis, in order to give information about which sources more contribute to the overall uncertainty.
Heat Transfer on Parallel Plate Heat Exchangers in an Oscillatory Flow
Authors: Mao Xiaoan , Shi Lei , Jaworski Artur J. , Kamsanam Wasan
Published: January 2011

In thermoacoustic devices, an acoustic wave interacts with internal solid structures such as thermoacoustic stacks (regenerators), to either produce acoustic power due to an imposed temperature gradient, or to produce a heat pumping effect by an acoustic excitation. A cold and hot heat exchangers are usually placed on either side of these internal solid structures to enable heat communication between the thermoacoustic devices and their surroundings. Heat exchangers of various geometries have been extensively studied in steady flows and results are available from a collection of published articles and handbooks. However, there is still a lack of data for heat exchangers in an oscillatory flow, because the interaction of oscillatory flow with the solid boundary is governed by complicated fluid flow and heat transfer processes that are not fully understood. This work is a step towards a better understanding of the heat transfer mechanisms in the acoustically induced oscillatory flow within thermoacoustic systems, in particular obtaining the quantitative description of the heat transfer between heat exchangers and the stack. The assembly of a stack and heat exchangers is replaced by a simplified “stack-less” pair of heat exchangers, in order to focus on the generic heat transfer processes rather than the intricacies of practical thermoacoustic systems. The fins of the hot and cold heat exchangers are kept at constant temperatures by virtue of resistive heating and water cooling, respectively. Planar Laser Induced Fluorescence (PLIF) and Particle Image Velocimetry (PIV) are used to obtain the temperature and velocity fields around the fins. The heat flux between the heat exchanger fins and the fluid is analyzed phase-by-phase. The time dependent local heat transfer coefficient is obtained from the temperature gradient in the thermal boundary layer. The measurements are conducted at various levels of acoustic excitation in order to study the correlation between the non-dimensional heat transfer coefficient Nu and the Reynolds number. The effect of the flow behaviour at the end of the plates on the temperature field in the region is also studied. It is hoped that this work could lead to a better understanding of heat transfer on short plates in the acoustically induced oscillatory flows.
Multibody Investigation on the Passive Safety Performances of Seats in Railway Vehicles
Authors: Caputo Francesco , Fidanza Francesco , Lamanna Giuseppe
Published: January 2011

The research activities described in this paper aim to identify the causes and the typologies of secondary impact injuries to passengers of a railway vehicle during a specific crash event, to understand the measure in which these injuries can be absorbed and to identify possible ways of reducing or eliminating them. The main investigated solution was to restrain passengers to their seats by considering the presence of seat belts. Biomechanical performances of passenger configurations with two-point and three-point seat belts were investigated and compared with those of unrestrained passengers. An anthropomorphic test device representative of medium size people was furnished and experimental tests were worked out in order to obtain effective data regarding the interaction of passengers with seats and seatbelts. By using these experimental data a multi-body numerical model of the sled test was calibrated and validated and restraining configuration performances, which could not be physically tested, were simulated.
Derivation of Position-Probability Density for the Transient Nano-Tunnel Problem in SET
Authors: Lin Sheam-Chyun , Shih Hsien-Chang , Chuang Fu-Sheng , Tsai Ming-Lun , Yanto Harki Apri , Chang Cheng-Ju
Published: January 2011

This theoretical investigation intends to study the nano-tunnel problem of the single electron transistor (SET), which is one of the most important components in the nano-electronics industry. With a combined effort of quantum mechanics and similarity parameter, the partial differential equation of transient position-probability density is attained and can be applied to predict the electron’s position inside the nano tunnel. Also, an appropriate set of the initial and the boundary conditions is set up in accordance to the actual electron behavior for solving this PDE of probability density function. Thereafter, a simple, closed-form solution for the probability density is obtained and expressed in terms of the error function for a new similarity variable η. Note that this analytic similarity solution is easy to perform the calculation and suitable for any further mathematical operation, such as the optimization applications. In addition, it is shown that these predications are reasonable and in good agreement to the physical meanings, which are evaluated from both microscopic and macroscopic viewpoints. In conclusions, this is an innovative approach by using the Schro¨dinger equation directly to solve the nano-tunnel problem. Moreover, with the aids of this analytic position-probability-density solution, it is illustrated that the free single electron in the SET’s tunnel can only appear at some specified regions, which are defined by a dimensionless parameter η within a range of 0 ≤ η ≤ 2. This result can be served as a valuable design reference for setting the practical manufacture requirement.
Investigation of Effective Parameters on Dynamic Response of Composite Bridge Under Moving Vehicle
Authors: Jafari Ali Asghar , Vahdat Azad Nader
Published: January 2011

In this paper, the effects of various parameters influencing on the dynamic response of composite bridge are investigated by FEM method. Herein composite bridge with one, two and four degree of freedom for vehicle has been studied. The corresponding Equations of motion are integrated numerically by applying the Newmark’s method. The models were verified by analytical and numerical solutions available for isotropic bridge. The speed of the vehicle, mass ratio, bridge damping on the dynamic deflection and acceleration and effect of composite bridge layup have been analyzed. Bridge damping can significantly decrease the acceleration of the structure, and it is true particularly for higher values of the speed parameters. Dynamic deflection is not influenced by damping changes; however, it also reduces with the increase of the damping ratio. Bridge damping has negligible effect on the vehicle acceleration. The bridge acceleration generally increases with the mass parameter. The vehicle acceleration increases much steeply and reaches much higher values for large mass parameters.
An Elastic-Plastic Solver of the Wheel-Rail Contact
Authors: Ba˘rbiˆnt¸a˘ Constantin I. , Yaldiz Sulleyman , Dragomir Alina , Cret¸u Spiridon S.
Published: January 2011

Wheel and rail in service undergo continual wear and plastic deformation at the surface, so that in time all wheel profiles will be different. The optimization by grinding a worn rail profile to minimize contact stresses requires the development of a software to reconstruct a rail profile using circular arcs. A working algorithm, able to be incorporated into a computer code, has been developed to solve the stress state in the general case of non-Hertzian contacts. To limit the pressure, an elastic-perfect plastic material has been incorporated into the computer code. The pressure distribution and the corresponding stresses states have been investigated for pure normal loadings, as well as for the combined, normal and tangential loadings. The elastic-plastic analysis model allows fast investigations regarding the influence of different parameters such as load level, contact geometry including the geometry of the worn profiles.
Modeling and Experimental Verification of a Novel SMA-Actuated Robotic Module
Authors: Hadi Alireza , Yousefi-Koma Aghil , Elahinia Mohammad , Moghadam Majid M.
Published: January 2011

Robotic modules with especial abilities may provide new opportunities in developing robotic systems. Changing the robot framework in different missions may be implemented in the modular robotic system design. Shape memory alloys (SMA) may be considered as suitable actuators with unique features. Due to the complex behavior of the SMAs less works are done on the precise modeling and positioning systems of them. Spring type SMA actuators, which are less considered in the literature, produce more deflections. In this paper a novel module with two DOFs is developed. SMA springs are employed as actuators in an embedded package including a mechanism, an electronic hardware, and a sensory system. Modeling of the spring type SMA is discussed in details using Liang and Brinson models. Simulation results are verified using an experimental setup indicating the applicability of the model in predicting the dynamic behavior of the module.
An Efficient, Non-Regularized Solution Algorithm for a Finite Strain Shape Memory Alloy Constitutive Model
Authors: Arghavani Jamal , Auricchio Ferdinando , Naghdabadi Reza , Reali Alessandro , Sohrabpour Saeed
Published: January 2011

In this paper we investigate a three-dimensional finite-strain phenomenological constitutive model and propose an efficient solution algorithm by properly defining the variables and by avoiding extensively-used regularization schemes which increase the solution time. We define a nucleation-completion criterion and modify the regularized solution algorithm. Implementation of the proposed integration algorithm within a user-defined subroutine UMAT in the commercial nonlinear finite element software ABAQUS has made possible the solution of boundary value problems. The obtained results show the efficiency of the proposed solution algorithm and confirm the improved efficiency (in terms of solution CPU time) when a nucleation-completion criterion is used instead of regularization schemes.
Bifurcation Analysis for Brake Squeal
Authors: Hetzler Hartmut
Published: January 2011

This article presents a perturbation approach for the bifurcation analysis of MDoF vibration systems with gyroscopic and circulatory contributions, as they naturally arise from problems involving moving continua and sliding friction. Based on modal data of the underlying linear system, a multiple scales technique is utilized in order to find equations for the nonlinear amplitudes of the critical mode. The presented method is suited for an algorithmic implementation using commercial software and does not involve costly time-integration. As an engineering example, the bifurcation behaviour of a MDoF disk brake model is investigated. Sub- and supercritical Hopf-bifurcations are found and stationary nonlinear amplitudes are presented depending on operating parameters of the brake as well as of tribological parameters of the contact.
Numerical Simulation of Cavitation Bubble Collapse in the Vicinity of a Rigid Boundary
Authors: Samiei Ehsan , Shams Mehrzad , Ebrahimi Reza
Published: January 2011

In the present study collapse stage of cavitation bubbles in the vicinity of a rigid boundary in quiescent water has been studied numerically with concentrating on initial bubble radius and stand-off parameter (the ratio between the distance of bubble center and the wall, and maximum bubble radius γ). Navier-Stokes and energy equations in an axisymmetric domain were hired to simulate the flow, and VOF method was used in order to track the interface between liquid and gas phases. Surrounding liquid was assumed to be incompressible water, and water vapor as ideal gas was considered for the bubble contents. Simulations were done in a wide range of bubble radius and stand-off parameter. Good agreements with reference experimental data were achieved. Results show that for the same bubble radii maximum jet velocities increase and collapse time decreases with increasing stand-off. However, increasing initial bubble radius causes the differences between maximum jet velocities, bubble volume at the moment of jet impact to the other side of the bubble, and collapse time of the cases with different values of stand-off to decrease. For the bubbles with smaller values of stand-off liquid jet forms sooner and its length with respect to bubble size is greater. Also, for the same standoff parameters liquid jet is wider and its length with respect to bubble size is smaller for smaller bubbles. As bubble manner tends to spherical with increasing stand-off parameter, calculated velocities in present study become larger than those of physical values.
Control Theory in Practice: Magnetic Levitation
Authors: Rogers John , Rabb Robert
Published: January 2011

A device that levitates a steel ball beneath an electromagnet is used for educational purposes at the United States Military Academy, West Point, New York. Students in the course “Mechatronics” engage in a set of laboratory exercises with the device to reinforce classroom learning. Mechatronics is a senior-level course that introduces the interdisciplinary design of smart systems. Students in the electrical engineering and mechanical engineering programs take the course together, and the material is taught by a team of instructors from both academic departments. The Magnetic Levitation experiments are the primary means of teaching the classical analog control portion of the course. Other aspects of the course involve interfacing microcontrollers with sensors and actuators, and digital control. The magnetic levitation device fits easily on a two-person workbench and requires a power supply and oscilloscope. An infra-red emitter / detector pair is used to sense ball position for a feedback compensator. Students first learn classical control theory in a co-requisite course, “Dynamic Modeling and Control.” Modeling principles are introduced in the context of the magnetic levitation system as an unstable plant to be controlled. The system can be simulated by models ranging from simply linear to more complex to teach the trade-off between model fidelity and model development effort. The students derive the nonlinear governing equations and then linearize the equations and develop the transfer function of the plant. Students design a compensator and simulate the resulting stabilized system with Matlab and Simulink software. Students build their compensator on a solderless project board to levitate the steel ball. A proven lead-type compensator using two resistors and a capacitor is readily provided to students that struggle with their own compensator design so that all teams may enjoy the fruit of a successful experiment. As a laboratory aid, the magnetic levitation system allows for basic and advanced approaches to both theoretical study and practical investigation of a nonlinear, unstable system control. The comparison of measured results to predicted behavior leads to insight about how the physical system is modeled by mathematics. Students write a case study describing the system in detail including characterization of the sensors and actuators. Instructors report that the hands-on nature motivates students to excel. Surveyed students cite the hands-on activities as relevant applications that help develop deeper understanding and greater appreciation for the concepts learned in the classroom. The students are motivated to learn by the fascination of defying gravity.
A Robust Active Vibration Control of Automotive Engine
Authors: Fakhari V. , Talebi H. A. , Ohadi A. R.
Published: January 2011

In this study, the effectiveness of an active engine mount in vibration suppression of a four-cylinder V-shaped engine is evaluated. In this regard, a 6 degree of freedom engine model under inertia and balancing mass forces and torques is considered. At first, the governing equations of motion of engine supported by three rubber mounts are presented. Subsequently, one of the rubber mounts is replaced by an active mount and the effectiveness of active mount, in the presence of sensor noise, in vibration isolation of the engine is investigated. Two robust control algorithms, namely H2 and H∞ schemes are employed to provide control input using feedback from accelerations of the engine body in the position of the mounts. Moreover, unstructured uncertainties due to the unmodeled dynamic of the plant, actuator and sensors are considered. Simulation results show that the active mount is more effective than the rubber mount in vibration suppression of the engine.
Experimental Investigation of Flow Instability in a Supersonic Inlet
Authors: Soltani Mohammad Reza , Farahani Mohammad
Published: January 2011

An extensive wind tunnel test series were conducted on an axisymmetric supersonic inlet. The model was tested at Mach numbers from 1.8 to 2.2 and at different values of mass flow rate. Shadowgraph flow visualization was used to capture the external shock structure in front of the inlet. The goal of this study is to find out the general characteristics of the inlet buzz. Frequencies of the buzz have been achieved from the analysis of the pressure data as well as the shadowgraph pictures. The amplitude of the shock waves motion has been measured from the visualization pictures too. In the some large value of mass flow rate, the frequency of shock oscillation increased versus Mach number. Also in each Mach number due to the mass flow rate decrement, the buzz frequency decreases and its amplitude increases conversely. Also buzz instability affects the external flow by the same frequency of the internal one.
On Independent Modal Control of a Vibrating System
Authors: Braghin Francesco , Cinquemani Simone , Resta Ferruccio
Published: January 2011

Of the multitude of available control techniques, modal control is a favourite amongst structural dynamicists because of its representation in modal coordinates. The term modal control is used to describe a wide variety of control techniques which find their origin in a description of the system through the main coordinates, defined by the modes of vibration of the system. This approach stems from the consideration that the response of a mechanical system to a disturbance is the sum of the independent responses of its vibrational modes. This motivates the desire to design a control that does not alter these mode shapes, but allows to change the natural frequency and the damping of each mode. In active vibration control the purpose is to increase the damping of modes interested in the vibratory phenomenon. The paper shows how stability, spillover effects, system controllability and sensors and actuators position are all linked to the analysis of the controlled system damping matrix and to the possibility that the forces introduced by the control is non-dissipative. Theoretical aspects are supported by numerical simulations.
Fatigue Behavior of Notched Aluminum Plates Repaired by Smart and Composite Patches
Authors: Khalili S. Mohammad Reza , Eslami Farsani Reza , Mojahedi Pasha
Published: January 2011

In this study, mode I fatigue crack growth behavior of single edge notched thin aluminum plates repaired with single side composite patches is investigated experimentally. Three patches are investigated in this analysis, 1- three layers carbon/epoxy laminated composite patch, 2- smart patches contained shape memory alloy (SMA) wires without pre-strain embedded in between the carbon/epoxy layers, and 3- smart patches contained SMA wires with pre-strain embedded in between the carbon/epoxy layers. The results are compared with the results obtained for un-repaired notched plate and the influence of SMA wires is also studied. The experimental results show a significant increase in crack growth life in all repaired plates compared with un-repaired plate. The repaired plates with smart pre-strained SMA patches show greater life as compared to other plates repaired by other patches. The three layers carbon/epoxy patches show better results compared to smart SMA un-strained patches. Also, numerical modeling is done by ANSYS software to obtain the stress intensity factor in mode I fatigue loading and then applied to Paris law for prediction of the fatigue crack growth life. The results are compared with the experimental results and a good agreement is obtained.
Poor-Contrast Particle Image Processing in Microscale Mixing
Authors: Ergin F. Go¨khan , Watz Bo Beltoft , Erglis Kaspars , Cebers Andrejs
Published: January 2011

Particle image velocimetry (PIV) often employs the cross-correlation function to identify average particle displacement in an interrogation window. The quality of correlation peak has a strong dependence on the signal-to-noise ratio (SNR), or contrast of the particle images. In fact, variable-contrast particle images are not uncommon in the PIV community: Strong light sheet intensity variations, wall reflections, multiple scattering in densely-seeded regions and two-phase flow applications are likely sources of local contrast variations. In this paper, we choose an image pair obtained in a micro-scale mixing experiment with severe local contrast gradients. In regions where image contrast is sufficiently poor, the noise peaks cast a shadow on the true correlation peak, producing erroneous velocity vectors. This work aims to demonstrate that two image pre-processing techniques — local contrast normalization and Difference of Gaussian (DoG) filter — improve the correlation results significantly in poor-contrast regions.
Computation of Overdrive Gear Ratio in Vehicle Gearbox With Considering Fuel Economy and Gearbox Specifications
Authors: Ghafoori Ahangar R. , Meigounpoory M. R. , Eskandari A.
Published: January 2011

In this article, the gear ratio of RD (An Iranian made car by Iran Khodro Co.) vehicle gearbox with considering fuel economy and gearbox specifications is evaluated. In the first step, the gearbox advantages and its effects on the engine rotational velocity with considering road load and engine torque are investigated. It is distinguished that in a specified velocity of vehicle, engine speed in overdrive state is very lower than engine speed in fourth gear. It means that noise and fuel consumption and engine wearing and damages will be decreased. The optimized region of engine operation is identified. Using a geometric progression between automotive gear ratios and entering number of effective parameters such as specific fuel consumption, minimum mean effective velocity, and etc., overdrive gear ratio is computed. Finally the overdrive gear ratio is chosen 0.81 for vehicle.
Effect of Mass Models in the Dynamic Analysis of Structures
Authors: Korkmaz I˙brahim
Published: January 2011

In this research the utilization of distributed, lumped, and consistent mass models in the dynamic analysis of structures is studied, and the results obtained by these models for example problems are compared. In distributed mass model, the dynamic stiffness matrix for a planar beam element is derived by integrating the differential equations of motion. In lumped mass model, the mass of the structure is lumped at the nodal points where translational displacements are defined. However, in the consistent mass model the mass characteristics corresponding to the nodal coordinates of beam element are evaluated by a procedure similar to the determination of the element stiffness coefficients. These mass models are executed for three numerical examples. Results of two examples are compared with analytical solutions. The last example analysis of planar frames with distributed mass model is calculated with using a developed computer program by using two comparison results of other examples. The Fourier series approach is used for the solution of dynamic equations. Numerical results have shown the effectiveness of the dynamic stiffness approach with the distributed mass model. The distributed mass model gives the exact values of the natural frequencies with the exception of numerical errors in computer calculations. This research is different from the other studies that demonstrate the application of the modeling and calculation of the natural frequency values’ accuracy regarding to choose mass model. It is also shows the method to deal with the external excitation.
Design and Verification of Bobsleigh Track
Authors: Braghin Francesco , Cheli Federico , Melzi Stefano , Sabbioni Edoardo
Published: January 2011

The design of new bobsleigh track is a challenging and difficult task since it requires several competences ranging from the physics of ice to civil engineering, from dynamics to tribology. Thus, presently, only very few companies are able to correctly design a bobsleigh track. Moreover, during the construction phase, unshared approximations, imposed by the orography and geology of the location, are adopted by the constructor. This leads to tracks that are usually characterized by unpredicted accelerations on the athletes (sometimes even above accepted standards). The following paper deals with the development of a simple though precise virtual tool for the prediction of both the speed (acceleration) profile and the trajectory of a bobsleigh able to easily account for the effects of small track profile changes. Therefore, this tool could be profitably used by both designers and constructors to avoid the necessity of “adjusting” the track once built.
Design and Control of a 13-DOF Biped Robot Using Human Gait
Authors: Naghibi Reza , Akbarzadeh Tootoonchi Alireza
Published: January 2011

This paper presents a new biped humanoid robot, as well as control strategies to be implemented for walking and balance recovery. The ultimate design goal was to design the structure to be as close to a lower part of human body as possible. Therefore, golden-ratio-based human body proportions and proper number of degrees of freedom of the lower part are used [1]. The biped has 12 actuated DOE in the lower body: three at each hip, one at each knee, two at each ankle as well as 1 additional DOF at its torso. Each degree of freedom is powered by a force controllable actuator. To achieve human like trajectory, human walking data has been used [2]. To insure both stability and human like trajectory, a torque compensator is added to the one DOF at the torso. The Biped is designed in SolidWorks and simulated in SimMechanic and COSMOSMotion. The movement of the joints are achieved by motors and harmonic drives. The contact between sole and ground is considered to be elastic and is modelled using spring and damper in horizontal and vertical directions [3]. Finally, control of the biped is performed using a PID control scheme and each of the 13 motors achieve desired human like trajectory.
The Development of a Surface Waviness Pattern During Brake-Like Applications
Authors: Slavicˇ Janko , Boltezˇar Miha
Published: January 2011

Dynamical systems with contacts are often exposed to wear even under small loads. The wear develops at the micro, macro or global level and changes the contact shape. This changed contact shape alters the dynamics of the system and can further increase the wear. This research presents a numerical investigation of the interaction between the wear at the contacts and the dynamics. The research involves a dynamical model normally used in the research of car-brake dynamics and simulates the run-in wear of the brake pad and the development of waviness on disc. Special attention is given to the real roughness of the contacting surfaces and to on exact numerical simulation; because concurrent contacts between rough asperities occur, a specifically developed multibody dynamics approach is presented. This research shows that after the run-in period a concave pad produces a waviness pattern on the disc. Using a spectral analysis of the disc’s surface it is possible to show the effect of the wear particle-size and the pad-width on the surface waviness.
Exergy Analysis of a Simple Gas Turbine System Considering Combustion Process as Complete Combustion and Equilibrium Combustion
Authors: Razmara Nayyer , Khoshbakhti Saray Rahim
Published: January 2011

Exergy analysis provides useful information for the system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. The present work is an attempt to compare the effect of variations of species concentrations of the combustion process in a simple gas turbine system. Therefore, using a Complete combustion model and an Equilibrium combustion program model, the exergetic evaluation is carried out for a simple gas turbine system with a rated output power of 30 MW. The Complete combustion involves O2, N2, CO2, H2O and Equilibrium combustion model involves N2, O2, CO2, H2O, CO, H2, H, O, OH, N, NO as the species of combustion products. In this work, Equilibrium combustion products were calculated using Olikara and Borman method. Also, a principle of division of chemical availability (exergy) into oxidation availability, reduction availability and diffusion availability has been investigated in these models. Expression involving the variables for exergetic efficiency, exergy destruction, and chemical availability in the components of the gas turbine cycle are derived. The exergy losses and efficiencies of components based on both Complete combustion and Equilibrium combustion models are evaluated. The exergetic efficiencies of the plant based on Complete combustion and Equilibrium combustion are determined to be 28.11% and 28.16%, respectively. It is found that, variation of species has negligible effect on the system main parameters. It is also concluded that chemical exergy in Equilibrium combustion is a little more than that of Complete combustion. Because of additional species involved in Equilibrium combustion, reduction availability and oxidation availability are defined in this modeling beside diffusion availability and it increases chemical exergy of equilibrium combustion modeling. The results obtained here show that in the analysis of the power plant cycles, a simple combustion model (i.e. Complete combustion model) is in good agreement with a complex combustion model considering various species (i.e. Equilibrium combustion model). As a result, there is negligible difference between results of the mentioned combustion models and the simple Complete combustion model facilitates the analysis of such processes.
Dynamic Stability of a Spinning Timoshenko Beam Subjected to a Moving Mass-Spring-Damper Unit
Authors: Young T. H. , Chen M. S.
Published: January 2011

This paper investigates the dynamic stability of a finite Timoshenko beam spinning along its longitudinal axis and subjected to a moving mass-spring-damper (MSD) unit traveling in the axial direction. The mass of the moving MSD unit makes contact with the beam all the time during traveling. Due to the moving MSD unit, the beam is acted upon by a periodic, parametric excitation. In this work, the equations of motion of the beam are first discretized by the Galerkin method. The discretized equations of motion are then partially uncoupled by the modal analysis procedure suitable for gyroscopic systems. Finally the method of multiple scales is used to obtain the stability boundaries of the beam. Numerical results show that if the displacement of the MSD unit is equal to only one of the two transverse displacements of the beam, very large unstable regions may appear at main resonances.
Design for Manufacturing Systems Complexity: A Perspective Approach
Authors: Garbie Ibrahim H. , Shikdar Ashraf
Published: January 2011

Nowadays researchers focused their attention on design for manufacturing, design for assembly, design for cost or design for quality,....., design for X, etc., but they didn’t address design for manufacturing complexity. Design for complexity is a systemic approach that simultaneously considers design objectives (i.e., optimize complexity level)), variables and constraints. In this paper, a guideline is presented to show the design requirements. Based on this requirement, the complexity levels will be analyzed through four fundamental levels: design for manufacturing systems vision complexity, design for manufacturing systems structure, design for manufacturing systems operating complexity, and design for manufacturing systems evaluating complexity. The new measuring is suggested for determining the level of complexity. This complexity level is measured and optimized in terms of issues count based on the designer/analyst view. This will represent the degree of freedom of manufacturing system designer to identify which issue is more important than others. The ultimate goal of this paper is to provide the manufacturing system designer with such complexity information throughout the analysis process that an efficient design requirement produces in the first instance. This analysis shows that the design for manufacturing systems complexity should be optimized and taken into considerations when designing manufacturing systems.
Numerical Simulation of Cone Formation in Electrospraying Process
Authors: Passandideh-Fard Mohammad , Rahimzadeh Mortaza , Pooyan Sajad
Published: January 2011

A numerical model is developed to study the transient behavior of a liquid jet leaving a capillary tube under an electrostatic field. The surface profile of the deforming jet is defined using the Volume-of-Fluid (VOF) scheme and the advection of the liquid free-surface is performed using Youngs’ algorithm. Surface tension force is treated as a body force acting on the free-surface using continuum surface force (CSF) method. To calculate the effect of the electric field on the shape of the free-surface, the electrostatic potential is solved first. Next, the surface density of the electric charge and the electric field intensity are computed, and then the electric force is calculated. Liquid is assumed to be a perfect conductor, thus the electric force only acts on the liquid free-surface and is treated similar to that of surface tension using the CSF method. The developed model is validated by a comparison between the calculated results and measurements for an electrowetting scenario for which experimental results are available in the literature.
Experimental Investigation of Gasoline Fumigation in a Turbocharged IDI Diesel Engine
Authors: Sahin Z. , Durgun O. , Bayram C.
Published: January 2011

In the present study the effects of gasoline fumigation (GF) in a turbocharged indirect injection (IDI) diesel engine have been investigated experimentally. Here an elementary carburetor which main jet opening (MJO) can be adjusted by a fine threaded screw has been installed on the inlet pipe of diesel engine. Thus gasoline at low amounts can be injected in the inlet air ant it evaporates during intake and compression processes. The engine operates at diesel principles and it is thought that instantaneous burning of fumigated gasoline will enhance the combustion and performance of diesel engine. Here the experiments have been performed for 2000, 3000 and 4000 rpm, at different fuel delivery rates (FDR). FDRs have been taken as (29, 33, 50, 67 and 75) % for 2000 rpm, (42, 50, 67, 75 and 83) % for 3000 rpm and (50, 67, 75, 83 and 100) for 4000 rpm. Also, experiments have been performed at 5 and 6 different carburetor MJOs for (2000, 3000) rpm and 4000 rpm respectively. By evaluating of experimental results, it is determined that effective power generally reduces at all of the engine speeds, whereas at some instances it takes values close to the neat diesel fuel (NDF). It is observed that the decrease ratio of effective power increases especially at low fumigation ratios, but it reduces for higher gasoline ratios. On the other hand, it is determined that brake specific fuel consumption (BSFC) reduces and thus effective efficiency increases. Similarly the BSFC reduction and effective efficiency increment take higher values for high gasoline ratios. Finally it has been seen that, BSFC reduces approximately at the levels of 5%. Also NOx concentration decreases approximately at the levels of 10%. Cylinder gas pressure becomes higher than NDF at the beginning of the combustion process, it reduces through to the end of the combustion and it again takes higher values at the end of expansion and during exhaust processes. Here the effect of the GF on the smoke formation has also been investigated. It is determined that, smoke index K reduces for up to (6–8) % GF and it begins to increase after 8% gasoline ratio. Its maximum reduction ratio is 20% and it is obtained at 8% GF for 2500 rpm.
The Influence of Fiber/Matrix Debonding on Inelastic Micro-Mechanical Behavior of Cross-Ply IMC Composites
Authors: Teimouri Hessamodin , Abedian Ali , Farahpour Hengameh
Published: January 2011

In this study the effect of stress field on delamination and fiber/matrix debonding in laminated composite panels is investigated from the micro-mechanical point of view by means of 3-D Finite Element Models. Specifically, the behavior of two-layer cross-ply symmetric laminates made up of SCS-6/Ti-24Al-11Nb Intermetallic Matrix Composite (IMC) during cooling from the processing temperature is studied. The results show that large plastic strains occur at the fiber/matrix interface at the fiber end on the laminate free edge which may eventually extend to the interface of the layers of the laminate inflicting delamination damage. This phenomenon is more serious at the corner areas of the laminate. It also can be shown that this situation is more serious for the four-layer laminate compared to the results of two-layer composite.
Simulation of Impact and Fragmentation With the Meshless Methods
Authors: Kılıc¸ Namık , Erdik Atıl , Ekici Bu¨lent
Published: January 2011

High velocity impact and penetration problems include large deformation, erosion, high strain rate dependent nonlinear material behavior and fragmentation. Therefore, meshless methods seem to be ideally suited for the modeling of penetration events as they allow unrestricted deformation and easy tracking of material interfaces and loading histories. In the first part of this study, a brief overview about meshless methods is given. Also the most important features of meshless methods with respect to mesh based approaches are compared. In the second part, numerical model is developed using one of the most frequently used meshless method, Smoothed Particle Hydrodynamics (SPH). 3D numerical simulations are performed on a high performance computer using MPP version of the explicit finite element code LS-Dyna. For reasonable behavior of material response under dynamic loading, Johnson Cook material models for armor steel target and 7,62 armor piercing projectile are derived using SHPB (Split Hopkinson Pressure Bar) test data. SPH computational investigation is compared with available experimental data such as penetration depth and impact crater diameter. For the future work, other potential meshless methods for ballistic impact problems are identified.
Numerical Approach to Design Process of Armored Vehicles
Authors: Erdik Atil , Kilic Namik , Guden Mustafa , Tasdemirci Alper
Published: January 2011

Today, it is imperative that armored vehicles need advanced protection kits against anti-symmetric threats more than before. The primary goal of this study was to assess benefits of explicit hydrocodes for mine protection resistance of armored vehicles. An analysis of an armored vehicle under blast loading caused by high explosive (HE) detonation is presented with comparison to a full-scale test. The problem was examined using LS-DYNA which is an explicit non-linear finite element code. Multi Material Arbitrary Lagrangian Eulerian (MM-ALE) Fluid Structure Interaction Method was selected to model the explosion domain so as to observe advancing of the shock wave in the compressed air and to investigate the effects of blast on the vehicle structure after explosion. Johnson-Cook constitutive material model, Jones-Wilkins-Lee (JWL) and Linear Polynomial equation of states were used for the problem. Results show that numerical analysis was in good agreement with the experimental result.
Characterization of Phase Transformation and Shape Memory Behavior of Ti-Ni 54.4 wt(%) by Heat and Thermal Treatments
Authors: Urbina Cristina , De la Flor Silvia , Gispert-Guirado Francesc , Fabregat Albert , Ferrando Francesc
Published: January 2011

The objective of the study was to quantify changes in the phase transformation behavior in NiTi SMA wires when they are heat treated and thermally cycled at zero stress. The analysis involved weight fraction evolution derived from XRD profiles using the Rietveld method and specific software. The results were compared with those obtained from ER measurements. The study then analyzed how both treatments affect the SMA hardness. The results show how R-phase presence decreases with the increase in heat treatment temperature and indicate that the R-phase is developed or stabilized by thermal cycling depending on the heat treatment temperature. The SMA hardness increases due to thermal cycling. The increase is greater if there has been no R-phase development during the heat treatment. Combining the results of these techniques is deemed to be the most suitable combination of heat treatment and thermal cycling by which to improve the SMA’s functional properties.
An Application of Discontinuous Galerkin Method for Blast Wave Simulations
Authors: Alpman Emre
Published: January 2011

An implementation of Runge-Kutta Discontinuous Galerkin method to an in-house computational fluid dynamics code capable of simulating blast waves was performed. The resultant code was tested for two shock tube problems with moderately and extremely strong discontinuities. Numerical solutions were compared with predictions of a finite volume method and exact solutions. It was observed that when there are extreme discontinuities in the flowfield, as in the case of blast waves, the limiter adopted for solution clearly affects the overall quality of the predictions. An alternative limiting technique was proposed and tested to improve the results obtained. Blast wave predictions using Runge-Kutta Discontinuous Galerkin method with the alternative limiting technique yielded slightly stronger and faster moving shock waves compared to finite volume solutions.
Study on Sound Absorption and Transmission Loss of Transversely Isotropic Multi Layers Porous Material
Authors: Keshavarz Reza , Ohadi Abdolreza
Published: January 2011

In this work, acoustic wave propagation at oblique incidence in a multi layers material that consists of different layers such as air, homogenous and transversely isotropic porous layers is described. Transfer matrix method (TMM) is applied to compute acoustical properties of multilayer system. For transversely isotropic layer, the transfer matrix based on total displacement formulation of the Biot’s theory is used. Finally, for multi layers porous materials, variation of the sound absorption coefficient and transmission loss versus frequency and angle of incidence are determined. Analysis shows that transversely isotropic porous layers changes the absorption coefficient and improve the transmission loss.
Reliability Characterization of a Piezoelectric Actuator Based AVC System
Authors: Mazzola Marco , Aggogeri Francesco , Merlo Angelo , Brunner Bernhard , de la O Rodriguez Maria
Published: January 2011

Reliability and Maintainability analyses are becoming an increasing competitive advantage in machine tool design. In particular, the goal of machine tools for Ultra High Precision Machining is to guarantee high specified performances and to maintain them over life cycle time. A structured reliability approach applied to such complex and innovative systems must be integrated in the early phase of the design. In this paper, the reliability characterization of an adjustable platform for micromilling operations is presented. The platform is intended to improve the surface finishing of the workpiece, through a broadband Active Vibration Control device based on high performance piezoelectric multilayer actuators. The study intends to assess the capability of the system to maintain along the life cycle the appropriate reduction of the chattering vibrations without any shape error. By dividing the system through a morphological-functional decomposition, the critical elements are detected and their reliability issues are extensively discussed. Their lifetimes are described through opportune distributions and models. The study is completed by the quantitative reliability prediction of the overall system. Finally, a sensitivity analysis is performed and reliability allocation implications are evaluated to determine the effect of every component on the system reliability characteristics and life cycle cost.
Influence of Intermolecular Forces on Dynamic Pull-In Instability of Micro/Nano Bridges
Authors: Moghimi Zand M. , Ahmadian M. T.
Published: January 2011

In this study, influences of intermolecular forces on dynamic pull-in instability of electrostatically actuated beams are investigated. Effects of midplane stretching, electrostatic actuation, fringing fields and intermolecular forces are considered. The boundary conditions of the beams are clamped-free and clamped-clamped. A finite element model is developed to discretize the governing equations and Newmark time discretization is then employed to solve the discretized equations. The results indicate that by increasing the Casimir and van der Waals effects, the effect of inertia on pull-in values considerably increases.