bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Damage Models to Reliability Investigations for Input/Output Electronic Connectors
Authors: Chang C.-C. , Liao K.-C.
Published: April 2008

Contact forces between terminals of an electronic connector and the corresponding counterparts play an important role on signal transmission. The mated terminal with insufficient contact force might severely raise electrical resistance and induce intermittence or disconnection of current eventually. For input/output connectors, however, the contact force of the terminal usually decays dramatically after several thousand mating/unmating cycles. Critical plane approaches are adopted to estimate the "application duration" which indicates the number of cycles as the contact force of the terminal degrades beneath the corresponding minimum requirement in the present study. Damage parameters based on various criteria are evaluated for the terminal under cyclic loading conditions. Relationships among the damage parameter, the contact force reduction ratio, and the number of cycles are then constructed by linking numerical results to experimental measurements. Proposed models could be further applied to reliability investigations for the similar terminal design.
Development and Performance Study of an Apparatus for Imparting Lateral Cyclic Load on Model Pile Foundation
Authors: Basak Sudip
Published: April 2008

The environment prevalent in ocean necessitates the pile foundations supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-pile system introducing progressive reduction in the bearing capacity as well as settlement of the pile foundation. To understand the effect of lateral cyclic load on pile group, a new apparatus, consisting of mechanically and electrically controlled components, has been designed and fabricated. Each of the components of this apparatus is calibrated and a series of trial tests are performed for its performance study. This paper presents detailed description of the apparatus, calibration and operating principle of each of its components, the observations made from trial experiments and the relevant conclusions drawn therefrom.
The Operating Features of a Stoichiometric, Ammonia and Gasoline Dual Fueled Spark Ignition Engine
Authors: Grannell Shawn M. , Assanis Dennis N. , Bohac Stanislav V. , Gillespie Donald E.
Published: April 2008

An overall stoichiometric mixture of air, gaseous ammonia and gasoline was metered into a single cylinder, variable compression ratio, supercharged CFR engine at varying ratios of gasoline to ammonia. The engine was operated such that the combustion was knock-free with minimal roughness for all loads ranging from idle up to a maximum load in the supercharge regime. For a given load, speed, and compression ratio there was a range of ratios of gasoline to ammonia for which knock-free, smooth firing was obtained. This range was investigated at its roughness limit and also at its knock limit. If too much ammonia was used, then the engine fired with an excessive roughness. If too much gasoline was used, then knock-free combustion could not be obtained while the maximum brake torque spark advance was maintained. Stoichiometric operation on gasoline alone was also investigated, for comparison. It was found that a significant fraction of the gasoline used in spark ignition engines could be replaced with ammonia. Operation on mostly gasoline was required near idle. However, mostly ammonia could be used at high load. Operation on ammonia alone was possible at some of the supercharged load points. Generally, the use of ammonia or ammonia with gasoline allowed knock-free operation at higher compression ratios and higher loads than could be obtained with the use of gasoline alone. The use of ammonia/gasoline allowed practical operation at a compression ratio of 12:1 whereas the limit for gasoline alone was 9:1. When running on ammonia/gasoline the engine could be operated at brake mean effective pressures that were more than 50% higher than those achieved with the use of gasoline alone. The maximum brake thermal efficiency achieved with the use of ammonia/gasoline was 32.0% at 10:1 compression ratio and BMEP = 1025 kPa. The maximum brake thermal efficiency possible for gasoline was 24.6% at 9:1 and BMEP = 570 kPa.
Application of Neural Network to Find Initial State of Optimization Parameters
Authors: Babakhani A. Reza , Sayyaadi Hasan
Published: April 2008

This paper derives an estimated function made by simple Neural Network to find initial state of optimization parameters. It changes a system of differential equations with boundary values to a system of equations with initial values. So a lot of time would be saved to solve it. As a result, the system with differential equations will reach the desired final state.
SSEM-AG Computer Model for Optimization of Polymer Extrusion
Authors: Wilczynski K. , Nastaj A.
Published: April 2008

The optimization of an extrusion process is a conflicting, multi-objective problem. It is complicated by the number of variables (screw/die geometry, operating conditions, material data) and their non-linear relations, as well as by the opposing criteria, for example extrusion throughput and power consumption. It is difficult to find the global optimum for the process avoiding local optima. There are two approaches to solve the problem, experimental and using a mathematical model of extrusion. Optimization techniques based on an experimentation are time-consuming and very expensive. In this paper we present an optimization methodology based on the Genetic Algorithms (AG), where response surface is given by the extrusion model. A mathematical Single-Screw Extrusion Model SSEM developed at the Warsaw University of Technology is used to predict the extruder behavior, and AG approach is used for optimization. An integrated SSEM-AG system was developed to study optimization of the single-screw extrusion process. Three design criteria (output variables) are selected for optimization: maximum extrusion throughput, minimum power consumption and low melt temperature. As input variables, screw speed, barrel temperature and screw channel depth are chosen.
Oscillatory Flow of Magnetorheological Fluids in Pipes
Authors: Letelier Mario F. , Siginer Dennis A.
Published: April 2008

In this paper it is analysed the case of an oscillatory flow in a round pipe in which a magnetic flow is applied. In magnetorheological flows (MRF) the fluid develops yield stress, the strength of which depends on the intensity of the magnetic field. The analysis considers an oscillatory pressure gradient and an oscillatory magnetic field of different frequencies. It is investigated the effect of a cyclical yield stress on the frequency and amplitude of the flow velocity, including the phenomenon of resonance. In this study, the MFR is modelled as a Bingham fluid with time- dependent yield stress.
Aspect Ratio Effects on Partially Premixed Flames From Elliptic Burners in Coflow
Authors: Hariharan P. , Periasamy C. , Gollahalli S. R.
Published: April 2008

In this paper, partially premixed flames of propane-hydrogen blends from elliptic burner geometries in coflow environment have been experimentally studied. Two different elliptic burner geometries with aspect ratios (AR) of 3:1 and 4:1 were used. A circular burner with the same discharge area as that of the elliptic burner was employed for comparison. Measurements were taken at stoichiometric and three other equivalence ratios. Global flame characteristics such as visible height, emission indices, and flame radiation were measured. Flame structure data such as transverse profiles of inflame concentrations of combustion products and local flame temperature were also measured at three axial locations in the flame. Results indicate that elliptic burner flames were shorter, more radiating, and produced lower NO and CO emissions than the corresponding circular burner flames. Results from the inflame measurements of NO and CO were in good agreement with the corresponding global data. Further, the 4:1 AR elliptic burners exhibited a twin-jet flame structure at fuel-rich conditions. The twin-flame structure was evident from the inflame measurements of temperature and combustion species. This study suggests that the combination of elliptic burner geometry and coflow reduces NO and CO emissions from combustion systems, which could potentially lead to cleaner environment.
Modeling of Eddy Current Damper Composed of Spherical Magnet and Conducting Shell
Authors: Takayama Yoshihisa , Sueoka Atsuo , Kondou Takahiro
Published: April 2008

If a conducting plate moves through a nonuniform magnetic field, eddy currents are induced in the conducting plate. The eddy currents produce a magnetic force of drag, known as Fleming's left-hand rule. This rule means that a magnetic field perpendicular to the direction of movement generates a magnetic damping force. We have fabricated the eddy current damper composed of the spherical magnet and the conducting shell. The spherical magnet produces the axisymmetric magnetic field, and the shape of the conducting shell appears to combine a semispherical shell conductor and a cylinder conductor. When the eddy current damper works, the conducting shell is fixed in space, and the spherical magnet moves under the conducting shell. In this case, since there are magnetic flux densities perpendicular to the direction of movement, eddy currents flow inside the conducting shell, and then a magnetic force is produced. The reaction force of this magnetic force acts on the spherical magnet. In our study, eddy current dampers composed of a magnet and a conducting plate have been modeled using infinitesimal loop coils. As a result, magnetic damping forces are obtained. Our modeling has three merits as follows: the equation of a magnetic damping force is simple in the equation, we can use the static magnetic field obtained using FEM, the Biot-Savart law or experiments and the equation automatically satisfies boundary conditions using infinitesimal loop coils. In this study, we explain simply the principle of this method, and model an eddy current damper composed of a spherical magnet and a conducting shell. The analytical results of the modeling agree well with the experimental results.
Experimental Study of Thermomigration in Lead-Free Nanoelectronics Solder Joints
Authors: Abdulhamid Mohd F. , Basaran Cemal , Hopkins Douglas C.
Published: April 2008

The study of thermomigration on Sn-Ag-Cu solder sphere subjected to a high thermal gradient of 1100°C/cm is presented. After 286 hours, the hot end showed a thin and flat intermetallic compound (IMC) while the cold side showed a scallop-like Cu6Sn5 IMC. Small voids can be seen within the Cu6Sn5 IMC after 712 hours on the cold side, while the IMC on the opposite side showed no observable changes.
Comparison of Subcooling Effect of Water as a Refrigerant With the Current Refrigerants
Authors: Kilicarslan Ali , Mu¨ller Norbert
Published: April 2008

The performance comparison of water as a refrigerant (R718) with some prevailing refrigerants including R717, R290, R134a, R12, R22, and R152a is presented. A computer program simulating an actual vapor compression refrigeration cycle including subcooling was developed to calculate the coefficient of performances (COPs) for the different refrigerants. Evaporator temperatures above which water yields a better COP over the other refrigerants are investigated for subcooling case. The effect of degree of subcooling on the COPs is elaborated. For most of the refrigerants (R290, R134a, R12, R22, and R152a) the COP increases by around one percent (1%) per one Kelvin (1K) subcooling, while the COP for R718 and R717 increases by around 0.2 % and 0.5 % per one Kelvin (1K) subcooling. At constant evaporator temperature, increasing the degree of subcooling results in decrease of the relative COP gain of R718. R718 gives the highest relative COP increase at constant condenser temperature and polytropic efficiency. The effect of polytropic efficiency on the performance is also investigated. It is observed that the evaporator temperature range at which R718 presents a better COP than other refrigerants increases with increasing values of polytropic compressor efficiency if the degree of subcooling is kept constant.
Streamlined Modeling for Reaction Equilibrium
Authors: Gaggioli Richard A.
Published: April 2008

Traditionally, the determination of composition at chemical equilibrium has been carried out using the concept of the "equilibrium constant." Though awkward, the use of equilibrium "constant" is straightforward when the equilibrium temperature and pressure are known. However, even with modern software (such as Stanjan [1]), the usage becomes very burdensome in cases such as: (a) constant volume combustion, with T known, (b) adiabatic combustion, at constant pressure (or volume), when the final temperature and density (or pressure) are unknowns, (c) there are more than one independent reactions, (d) non-isothermal combustion with heat transfer, (e) when ideal-gas or ideal solution assumptions are not acceptable Furthermore, even in the more simple cases, becoming engrossed with the mechanics of applying the equilibrium constant (and other relevant principles), students and practitioners often lose sight of the fundamentals that are being applied. In this paper, via several examples, it is illustrated how to directly employ the fundamental principles - element, mass, volume, energy and entropy balances, along with the property relations - and avoid the use of equilibrium constants. Reaction equilibrium conditions - composition, temperature, pressure, density - are determined in a straightforward, easy manner. The key to this improved and easy approach is the accessibility of equation solving software that includes property relations for gases and liquids. In particular, in the present work, EES [2] is employed.
Substructure Coupling of Micro-End Mills
Authors: Mascardelli Brock A. , Park Simon S. , Freiheit Theodor
Published: April 2008

Micro-end milling is an important micro-manufacturing technique which offers the ability to machine micro parts of complex geometry relatively quickly when compared with photolithographic techniques. Key to good surface quality in the micro milling operation is the minimization of tool chatter. This requires an understanding of the system dynamics; the system including both the milling tool and the milling structure. However, owing to the miniature nature of micro end mills whose diameters are as small as 50 micrometers, impact hammer testing cannot be applied directly to predict the dynamics at the tool tip. This paper investigates substructure coupling of the spindle/micro machine and arbitrary micro tools with different geometries. This is done through use of the receptance coupling technique. The frequency response functions (FRFs) of the spindle/micro machine are experimentally measured through impact hammer testing utilizing a laser displacement gauge. The dynamics of an arbitrary tool substructure are determined through modal finite element (FE) analyses. Joint rotational dynamics are indirectly determined through experimentally measuring FRFs of gauge tools. The method also enables designers to come up with the optimum design of tool geometries prior to actual fabrication to prevent chatter vibrations.
MIMO-FEA Active Vibration Suppression of a Satellite Using an Adaptive Composite Thruster Platform
Authors: Ghasemi-Nejhad Mehrdad N. , Antin Nicolas
Published: April 2008

Adaptive or intelligent structures which have the capability for sensing and responding to their environment promise a novel approach to satisfying the stringent performance requirements of future space missions. This research focuses on a finite element analysis (FEA) multi-input-multi-output (MIMO) approach for vibration suppression and precision position control of a satellite thruster and its structure, due to the thruster-firing, employing an intelligent composite thruster platform. This smart platform connects the thruster to the structure of the satellite and has three active struts and one active central support with piezoelectric stacks as actuators, and each has a sensor at its base. It also has an active circular composite plate as the top device plate with nine embedded piezoelectric patches that six of them are back-to-back and function as three actuators pairs and three of them are placed next to the bottom actuators and function as sensors. Here, the predominant modes of the structure are first determined. In the FEA method, a finite element harmonic analysis was employed to develop a vibration suppression scheme, which was then used to study the vibration control of the satellite structure using the vibration suppression capabilities of the intelligent platform mounted on the satellite. In this approach, the responses of the structure to a unit external force as well as unit internal piezoelectric control voltages are first determined, individually. The responses are then assembled in a system of equation as a coupled system and then solved simultaneously to determine the control voltages and their respective phases for the system actuators for a given external disturbance. Next, this technique was applied to the vibration suppression of the satellite frame as well as its thruster simultaneously as a coupled problem and the results are discussed. This approach is an effective technique for the design of smart structures with complex geometry to study their active vibration suppression capabilities and effectiveness. The entire system has ten actuators: four piezoelectric stack actuators and three pairs of piezoelectric patch actuators.
Unsteady Three-Dimensional Analysis of Inlet Distortion in a Transonic Fan
Authors: Sun Peng , Feng Guotal
Published: April 2008

A time-accurate three-dimensional Navier-Stokes solver of the unsteady flow field in a transonic fan was carried out using "Fluent-parallel" in a parallel supercomputer. The numerical simulation focused on a transonic fan with inlet square wave total pressure distortion and the analysis of result consisted of three aspects. The first was about inlet parameters redistribution and outlet total temperature distortion induced by inlet total pressure distortion. The pattern and causation of flow loss caused by pressure distortion in rotor were analyzed secondly. It was found that the influence of distortion was different at different radial positions. In hub area, transportation-loss and mixing-loss were the main loss patterns. Distortion not only complicated them but enhanced them. Especially in stator, inlet total pressure distortion induced large-scale vortex, which produced backflow and increased the loss. While in casing area, distortion changed the format of shock wave and increased the shock loss. Finally, the format of shock wave and the hysteresis of rotor to distortion were analyzed in detail.
Thermodynamic Equillibrium Model of Emission Levels of Small Gas Turbine Engine Using Kerosene Ethanol Blends
Authors: Solanki Hitesh K. , Channiwala S. A.
Published: April 2008

The increasing awareness towards environment protection and peak load response is accredited in the development of gas turbine system. Many such system preliminary utilizes liquid fuels like kerosene. The emission level with such liquid fuel may be reduced by addition of oxygenated fuel like ethanol. Hence, the basic objective of present paper is to investigate analytically the influence of ethanol addition on emission levels of the kerosene fired small laboratory gas turbine unit. This paper discusses about the theoretical investigation on emission levels with kerosene-ethanol blended fuel using thermodynamic equilibrium model. The theoretical investigations have been carried out on Gilkes GT 85/2 twin shaft Gas Turbine Engine with ethanol blended kerosene fuel to a concentration level of 25% ethanol in the step of 5% increment. The investigations of the emission levels were carried out for CO2, CO, O2, H2, N2, H2O, OH and NO with respect to equilibrium temperature at different overall equivalence ratios ranging from 0.1 to 1.1. It is worth to mention that the equilibrium thermodynamic model clearly indicates that in narrow operative range of equivalence ratio (0.1 to 0.2) and the ethanol addition to an extent of 10% to 15% clearly offers reduced emission levels.
Comparative Performance Analysis of IADR Operating in Natural Gas-Fired and Waste-Heat CHP Modes
Authors: Petrov Andrei Y. , Sand James R. , Zaltash Abdolreza , Fischer John , Mitchell Rick
Published: April 2008

Fuel utilization can be dramatically improved through effective recycle of "waste" heat produced as a by-product of on-site or near-site power generation technologies. Development of modular compact cooling, heating, and power (CHP) systems for end-use applications in commercial and institutional buildings is a key part of the Department of Energy's (DOE) energy policy. To effectively use the thermal energy from a wide variety of sources which is normally discarded to the ambient, many components such as heat exchangers, boilers, absorption chillers, and desiccant dehumidification systems must be further developed. Recently a compact, cost-effective, and energy-efficient integrated active-desiccant vapor-compression hybrid rooftop (IADR) unit has been introduced in the market. It combines the advantages of an advanced direct-expansion cooling system with the dehumidification capability of an active desiccant wheel. The aim of this study is to compare the efficiency of the IADR operation in baseline mode, when desiccant wheel regeneration is driven by a natural gas burner, and in CHP mode, when the waste heat recovered from microturbine exhaust gas is used for desiccant regeneration. Comparative analysis shows an excellent potential for more efficient use of the desiccant dehumidification as part of a CHP system and the importance of proper sizing of the CHP components. The most crucial factor in exploiting the efficiency of this application is the maximum use of thermal energy recovered for heating of regeneration air.
Engineering Analyses for Railroad Tank Car Head Puncture Resistance
Authors: Jeong D. Y. , Tang Y. H. , Yu H. , Perlman A. B.
Published: April 2008

This paper describes engineering analyses to estimate the forces, deformations, and puncture resistance of railroad tank cars. Different approaches to examine puncture of the tank car head are described. One approach is semi-empirical equations to estimate the velocity at which puncture is expected to occur. Other approaches apply elastic-plastic finite element analysis. The results from these approaches are compared with experimental data from impact tests, and are shown to provide reasonable estimates of impact forces.
Multiscale-Based Mechanical Engineering Education
Authors: Karami G. , Pieri R. V.
Published: April 2008

The classical engineering mechanics courses of Statics, Dynamics and Strength of Materials are taught to most engineering disciplines. With the advent of multiscale analysis and practice, reforms should be implemented in such classical mechanics courses to address the change so that they won't be limited only to continuum and macro-based level, but to include all the scales. This paper will suggest revisions that should be implemented in these courses. This includes introducing the concepts of multiscale engineering and the addition of new modules in the form of example problems in micro and nano-scales. Relying upon the framework of existing courses and using the existing physical and intellectual resources, an array of educational activities will be suggested to provide such an opportunity for undergraduate engineering students. The efforts will be substantiated and facilitated using the simulation capabilities of Computer Aided Engineering and Drawing (CADD) techniques as well as the analysis capabilities of Finite Elements Model (FEM) procedures.
Retaining Hypoid Gear Performance Characteristics With Differential Housing and Shafts Deflections
Authors: Kolivand Mohsen , Hannaneh Abdolhamid , Soltani Nasser , Shoroki Zabihhollah Kargar
Published: April 2008

Hypoid gears are widely used in rear drive and 4WD vehicle axles. Investigation of their sensitivity to misalignments is one of the most important aspects of their design and optimization procedures. Because of unavoidable mounting deflections under working load, the values for mounting distances and angle deviate from the designed (desired) values (due to elastic deformation of differential housing and gear shafts). As a result the performance characteristics will be changed. This study provides a calculation procedure to design "optimized vehicle differential housing side elastic coefficients" that maintains primary performance characteristics during load variations (caused by both the road and engines). The calculation is based on third order contact surface parameters for combined mismatched tooth surfaces. Calculations will be done in four separate groups to maintain four primary groups of performance characteristics, including: i) the amount of transmission error ii) contact pattern shape (by controlling bias angle) iii) backlash and iv) contact pattern size; in all mentioned cases theoretical contact pattern position during differential housing deflections is kept unchanged. Moreover, an experimental analysis was performed on a hypoid gear pair, the results of which were in close relation to theoretical results of sensitivity of contact pattern location. The method used in this study gives insight to effects of differential housing and gear shaft deflections (as misalignments) on hypoid gear performance. Considering this information in differential housing and gear shaft design will provide more correlations between hypoid gear pair and their housing and shafts in order to optimize performance characteristics under actual load.
Deformation Effects on the Load Carrying Capacity of the Barrel Bearing in Axial Piston Pumps and Motors
Authors: Achten Peter A. J. , Schellekens Marc P. A.
Published: April 2008

Most hydrostatic pumps and motors apply mechanical face seals, often also acting as a thrust bearing. The load carrying capacity of these bearings is very much dependent on the pressure profile generated in the sealing gap. Previous research, outside pumps and motors, has already shown that the gap pressure profile is largely influenced by small radial deformations of the seal lands. This paper discusses the elastic deformation of pump components and the effects of these deformations on the load carrying capacity of a barrel in an axial piston machine.
Modeling of a Membrane Mirror Strip Actuated Using a Piezoelectric Bimorph
Authors: Renno Jamil M. , Tarazaga Pablo A. , Seigler Michael T. , Inman Daniel J.
Published: April 2008

This paper presents an improved model for the one-dimensional behavior of a membrane mirror strip actuated using a piezoelectric bimorph. This model specifically accounts for the changes in physical properties of the membrane strip at the location of the piezoelectric bimorph. The membrane strip is modeled as a pinned-pinned beam under tension and the finite element method (FEM) is used to represent the system mathematically. The frequency response obtained from the proposed model is shown to be in agreement with experiments. Furthermore, the importance of including local mass and stiffness effects is demonstrated.
Lumped Parameter Modeling of a Magnetorheological Fluid Clutch
Authors: Ulicny John C. , Klingenberg Daniel J. , Smith Anthony L. , Sun Zongxuan
Published: April 2008

A lumped-parameter mathematical model of an automotive magnetorheological (MR) fluid fan clutch was developed. This model is able to describe the average fluid temperature, average clutch temperature, and output fan speed as a function of time, input current, and fluid composition. The model also reproduces numerous features of fan operation observed experimentally and revealed a mechanism for some observed cases of hysteresis. However, it fails to capture certain other features which lead us to conclude that phenomena which are not included in the model, e.g., sedimentation and re-suspension, are important to the clutch behavior. In addition, the results indicate that certain physical properties need to be measured over a larger temperature range in order for the model to better predict the clutch behavior.
Synthesis of Magnesium Reinforced With Nano-Size Y2O3 Using Disintegrated Melt Deposition Technique
Authors: Goh C. S. , Wei J. , Gupta M.
Published: April 2008

Magnesium (Mg), which is the lightest structural metal known, is used in various high-end sectors due to its high specific strength and stiffness. In an attempt to further improve the mechanical properties of Mg, a judicious incorporation of reinforcements into Mg is recommended. Conventional micron-size particulate reinforced Mg composites are faced with the issues of low ultimate tensile strength and ductility due to particle cracking and particle matrix interfacial failures. To overcome these underlying problems and to look for further improvement in properties, the use of nano-size particles is investigated. Accordingly, Mg reinforced with 0.5, 1 and 2 volume percent of nanosize Y2O3 respectively were synthesized using the disintegrated melt deposition technique. Mechanical property results reveal an improvement in yield and tensile strengths of the nanocomposites relative to pure Mg. Ductility of the nanocomposites remain relatively constant even with up to 2 volume percent of Y2O3 particles added. The Mg nanocomposites synthesized exhibited excellent combination of properties that were more superior than conventional Mg-SiC composites.
Mechanical Performance Analysis of Axially Loaded Active Fiber Composites
Authors: Askari Davood , Nejhad Mehrdad N. Ghasemi
Published: April 2008

Active fiber composites (AFCs) or macro fiber composites (MFCs) are often subjected to external loads and mechanical deformations. Furthermore, demands from industry for sensors and actuators with higher quality and better performance for specific applications have lead the researchers to design piezoelectric systems with optimal configurations to enhance the performance of such actuators and sensors. Therefore, it is important to investigate the mechanical performance of the individual AFCs/MFCs that exist in different geometrical configurations with alternative constituent materials. Here in this work, analytical exact solutions for effective mechanical properties of AFCs/MFCs are derived and then used to obtain the analytical exact solutions for displacements, strains and stresses induced in axially loaded AFCs/MFCs, which is the most common loading condition, i.e., tension/compression, that exist for such structures. In our study, constituent materials are considered orthotropic and two different geometries, i.e., AFCs/MFCs with circular and rectangular cross-sections, are investigated. For the given material properties, the displacement, strain, and stress results, corresponding to an axially applied external load are obtained in the domain of each constituent for both AFC/MFC geometrical configurations. To verify the analytical exact solution, 3-dimensional finite element analysis is performed and then the results obtained from both techniques are compared where excellent agreement was achieved.
Effect of Tooth Profile Modifications on the Dynamics of High-Contact-Ratio Gears With Different Tooth Spacing Errors
Authors: Lin Hsiang H. , Liu Jing
Published: April 2008

A computer simulation was conducted to investigate the effectiveness of profile modification for reducing dynamic loads in high-contact-ratio gears with different tooth spacing errors. The simulation examined varying amplitudes of spacing error and differences in the span of teeth over which the error occurs. The modification considered included both linear and parabolic tip relief. The dynamic analysis was performed using a revised version of a NASA gear dynamics code, modified to take into consideration the tooth spacing errors in the dynamic analysis. The findings of this study can be used to design robust tooth profile modification for improving dynamic performance of high-contact-ratio gear sets with different tooth spacing errors.
Determination of the Temperature Dependent Dynamic Response of Elastomeric Materials Using the Split Hopkinson Pressure Bar
Authors: Vallee Glenn E. , Army Steven D.
Published: April 2008

An effective, low cost method of determining the temperature dependent dynamic response of elastomeric materials at high strain rates using the Split Hopkinson Pressure Bar (SHPB) is developed. The test system allows the determination of the dynamic modulus at temperatures up to 150°C with control of specimen temperature within ± 3°C without the use of specialized equipment or cumbersome heating and positioning fixtures often required for temperature dependent testing. The test specimen is heated using a low cost electric resistance tape, which heats the transmitter and incident bars adjacent to the specimen. A finite element analysis is performed to predict the temperature vs. time response of the test specimen, which is verified using a simple thermocouple arrangement. The dynamic stress-strain response of a nitrile elastomer, commonly used as an impact absorber, is investigated over temperatures ranging from 20°C to 110°C at strain rates between 3000/s and 3500/s. The effect of strain rate on the dynamic modulus is not significant, but the effect of temperature is dramatic. The dynamic modulus of the nitrile is reduced by more than 60% at 110°C.
Biological Agent Detection Using Optical Diffusometry Methods
Authors: Kumar Aloke , Gorti Venu , Wereley Steve
Published: April 2008

Biological agent detection has captured the attention of many researchers over the last few years. The present research explores the possibility of directly measuring the diffusion coefficients of sub-micron particles as a means of pathogen detection. At a constant temperature, the diffusion coefficient is simply a function of the drag on the particle. If the particles are functionalized with antibodies against a specific analyte and introduced into a sample containing that analyte, binding of the analyte with the particles will increase the particles' hydrodynamic drag. This results in a decrease in diffusion, which is measured by a particle tracking algorithm. The reduction in diffusion is correlated with the amount of analyte present. Sensitivity to experimental conditions is also explored and it is shown that alternate methods like optical traps provide an even better technique for biological agent detection.
Adaptive Sliding Mode Control of MEMS Vibrational Gyroscope
Authors: Fei J. , Batur C.
Published: April 2008

This paper presents a new sliding mode adaptive controller for MEMS z-axis gyroscope. The proposed adaptive sliding mode control algorithm can on-line estimate the component of the angular velocity vector, which is orthogonal to the plane of oscillation of the gyroscope (the z-axis) and the linear damping and stiffness model coefficients. The stability of the closed-loop system can be guaranteed with the proposed control strategy. The numerical simulation for MEMS Gyroscope is investigated to verify the effectiveness of the proposed adaptive sliding mode control scheme. It is shown that the proposed adaptive sliding mode control scheme offers several advantages such as on-line estimation of gyroscope parameters including angular rate and large robustness to parameter variations and external disturbance.
Efficient Test Procedures for Characterizing MR Dampers
Authors: Boggs Chris , Borg Lane , Ostanek Jason , Ahmadian Mehdi
Published: April 2008

The response of a magneto-rheological (MR) damper is often characterized by a force-velocity response plot from a sinusoidal input. These plots are created in a shock dynamometer in which one end of the damper is attached to a load frame and the other end is moved in a sine wave with a given peak velocity and frequency. The peak damper force from a series of sine wave tests of varying peak velocity is measured and plotted as discrete data points versus the relative velocity across the damper. This is a standard procedure for characterizing passive shock absorbers in the automotive industry. The validity of this characterization relies on the assumption that the damper is dominantly a velocity-dependent device. However, it is well-known that the internal dynamics of the damper depend not only on the velocity of the input, but also the frequency of the excitation. Therefore both velocity and frequency should be considered as independent parameters to achieve a more complete characterization of a MR damper's response under sinusoidal excitation. This paper investigates the dependence of the force response to both peak velocity and frequency, for several different MR dampers from a wide variety of applications. By treating the velocity and frequency as two independent parameters, a complete characterization of the damper's response under sinusoidal excitation can be characterized. After investigating how damper force varies with both peak velocity and frequency, efficient test procedures are recommended for future MR damper characterizations.
Adaptive Feedforward Vibration Control of Flexible Structure With Discrete Sliding Mode Controller
Authors: Fei J.
Published: April 2008

This paper presents an adaptive feedforward control scheme using the least mean square (LMS) algorithm combined with sliding mode control for a flexible beam using piezoceramic actuator. A finite element model of the dynamic response of flexible beam system with PZT patches is derived and analyzed. Implementation of an adaptive LMS feedforward controller has the advantages of inherent stability and simplicity in design. The proposed adaptive LMS feedforward control system maintains the basic structure of the adaptive feedforward controller, but incorporates reference model in the system. Discrete sliding mode controller is added in the feedback loop to enhance the robustness of control system subjected to the variation of system parameters and external disturbances. Simulation results from flexible beam model verify the effectiveness of the proposed adaptive LMS feedforward with sliding mode control scheme and good disturbance rejection properties.
University Spinouts and Student Start-Ups: A Study in Heat Transfer and Rocket Science?
Authors: Handscombe Robert D. , Patterson Eann A. , Rodriguez-Falcon Elena
Published: April 2008

One of the current challenges for the developed countries is to establish and maintain a commercial and competitive advantage without the benefit of a low wage economy and in the face of increasingly stiff competition from such economies. Business analysts and regional development agencies find it easy to imagine the role of university staff and students in creating GDP from knowledge and technology but the challenge of entrepreneurship is often unimagined by faculty and students alike. How might the opportunities of new, knowledge-based business be brought more coherently to the attention of engineering faculty and students? Maybe one way is to begin the discussion by using engineering concepts familiar to the students and to develop an enterprise strand through the undergraduate curriculum. This paper provides some ideas of how the challenge might be accepted. Technology transfer, broadly understood to be the creation of new products, new processes and new companies from the research findings in universities, is well-established in principle but relatively few faculty are actively engaged in it. The demand is evident: few, if any, companies have the resources to carry out all the research and development necessary to generate the technology that they need for their products and processes. This paper considers how technology transfer might be characterised by an engineering approach and by analogy to well-established heat transfer processes. This engineering approach is developed further to consider the factors relevant to graduate entrepreneurship. The argument is put forward that the appropriate analogy can be drawn from combustion science and space exploration: the challenge is to identify barriers to 'ignition' and drivers of 'escape velocity'. The factors are reviewed and assessed in the light of feedback from students involved in business start ups. The conclusion is that not only might the engineering analogies be a useful way to introduce entrepreneurial issues to engineering students, but also that the analogies allow analysis that might indicate how improvements may be made to the support activity for student start-ups.
On Global Transversality and Tangency in a Periodically Forced, Damped Duffing Oscillator
Authors: Luo Albert C. J.
Published: April 2008

In this paper, the analytical conditions for global transversality and tangency of a 2-D nonlinear dynamical system are derived. Further, a periodically forced, damped Duffing oscillator with a separatrix is investigated as an application example. The corresponding analytical conditions for the global transversality and tangency to the separatrix are obtained and the global and tangential flows are illustrated to verify the analytical conditions. The illustrations show that the analytical and numerical predictions of the global transversality and tangency exactly are agreed very well. The analytical conditions are obtained from the new theory rather than the Melnikov method. The new conditions for the global transversality and tangency are more accurate and independent of the small parameters. Therefore, chaotic flows based on the global transversality will be further investigated, and the corresponding results will be presented in a sequel.
Warpage of Flip Chip BGA Package
Authors: Vujosevic Milena
Published: April 2008

The work focuses on the thermally induced out of plane displacement of Flip Chip Ball Grid Arrays (FCBGA). Analytical expressions for substrate displacements are derived based on the Plate Theory and Suhir's solution for stresses in tri-material assembly. The validity of the model is established by comparing the analytical solution to the finite element results as well as to the experimental data. The benefits of the model are twofold: 1) it provides a tool for fundamental understanding of the parameters that influence warpage, and 2) has a predictive capability. With respect to 1) an analysis is presented on the nature and degree of influence that different geometric and material parameters have on the FCBGA warpage. With respect to 2) the "Warpage Contour Plot" is proposed as a tool for warpage prediction that can be easily utilized in the early stages of the design process.
What Makes a Bicycle?: A Coloring Activity to Teach Basic Mechanical Concepts
Authors: Dolid Rosamond L.
Published: April 2008

A hands-on coloring activity is developed that teaches participants basic mechanical concepts using visual, auditory and tactile learning styles. The fist version of the coloring activity book is geared toward 4th-6th grade students, and is easily expandable to high school and beyond by incorporating more detail and associating the colored-in drawings with relevant physics and mathematical equations. A facilitator leads the students through the coloring activity, one part at a time. For example, the frame of a bicycle is colored one tube at time, the students are directed to write in the name of each tube as they color, and a discussion of basic functionality and design constraints can ensue. A second coloring activity is currently under development to teach basic functionality of an electro-hydraulic servovalve. This activity is not suited for children – it is aimed at adults who are either students of fluid power or work in industrial settings that involve fluid power.
A Study of Traffic Noise Reduction Performance of Arc Pavement Roads and Traffic Flow
Authors: Lou Zheng , Dai Liming
Published: April 2008

Asphalt Rubber Concrete (ARC) pavement has shown an excellent performance of noise reduction in terns of reducing the power of air pumping, absorbing sound power, depressing carcass vibration and changing sound reflection geometry. This research is to investigate the traffic noise reduction performance of a segment of test highway with ARC pavement in Saskatchewan, Canada. Before and after the highway section was repaved, a series of traffic noise level measurements combining with traffic flow monitoring are conducted in order to compare the sound performance of ARC and conventional pavements. A relationship between the noise level and corresponding traffic flow conditions of ARC pavement is established. The energetic averaging method is employed to study the relationship between traffic noise level and traffic flow condition. The two noise levels of 24-hour's time averaged and Statistical Pass-By noise levels indicated that the ARC pavement has a better sound performance over that of conventional pavement in terms of traffic noise reduction. The traffic noise reduction applicability of ARC pavement under various traffic flow conditions is also performed in this research.
Effect of Solder Mask Thickness on Shear and Pull Tests of Lead-Free Solder Balls
Authors: Song Fubin , Lee S. W. Ricky
Published: April 2008

The present study is aimed at investigating the effect of solder mask thickness on the solder ball shear test. Compared to the ball pull test, less brittle failures were found in the ball shear test. This is most likely caused by the support of solder mask. So far there is not publication reporting the effect of solder mask in detail. In this paper, specimens with various thicknesses of solder mask were fabricated and a series of ball shear tests were conducted. Cold ball pull (CBP) tests were performed as well for parallel studies. The attachment strength of solder balls under multiple reflows was evaluated as an index for comparison. The test results indicate that, in ball shear tests, brittle failures can be identified more easily in specimens with thinner solder mask after multiple reflows, especially for tests with higher shear speed and more reflows. No obvious effect of solder mask thickness on the ball pull test was found, regardless of different pulling speeds and multiple reflows.