bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Shock Testing as a Reliability Qualification Test for Lead-Free Solder
Authors: Goray Kunal , Mahalingam Saketh , Shah Amit , Dasgupta Abhijit
Published: April 2008

Accelerated thermal cycling tests are used to ascertain the reliability of solder interconnects in electronics assemblies. These tests typically last a few months and therefore, are highly resource intensive. Thermal shock tests on the other hand are faster but have been found to be ineffective in accelerating thermal cycling failures for eutectic tin lead solder. In this paper, thermal shock testing is proposed as an alternative to conventional thermal cycling testing for lead-free solder interconnects using Sn, Ag and Cu (SAC) solder. Results from the thermal shock and thermal cycling testing of Ball-Grid-Array (BGA) components are presented. Failure analyses of the solder joints reveal the failure mode for thermal shock in comparison to thermal cycling testing. Numerical modeling results for the thermal cycling and thermal shock testing for lead free and eutectic lead solder are then presented and discussed. The simulation results agree with the experiments and theory is proposed to account for the similar trends between thermal cycling and thermal shock testing for lead free solder.
CFD Investigation of Developing and Redeveloping Laminar Flow and Heat Transfer Characteristics in Coiled Tube Systems for Constant Wall Temperature Heating and Cooling: Part I — Toroid and Helical Configurations
Authors: Bowman Anthony J. , Park Hyunjae
Published: April 2008

In this paper developing laminar fluid flow and heat transfer performance in toroidal and helical coiled tube heat exchanger systems with coil-to-tube radius ratios (5 to 45) and small helical pitch are investigated using appropriate numerical modeling techniques available in the CFD package (Fluent v6.2). Base CFD models were primarily developed, optimized and compared with available published friction factor and heat transfer data and correlations for the toroidal and helical coil systems. With the proven CFD modeling technique and the results obtained, the analysis was extended to the coil-to-tube radius ratios of interest and to the investigation of the effect of thermo-physical properties of working fluids on the system thermal performance. The CFD models employ variable thermo-physical properties in the analysis of uniform wall temperature heating and cooling of common working fluids such as air and water. Defining appropriate dimensionless variables to describe the developing and redeveloping hydrodynamic and thermal flow for coiled tube systems, the variations of friction factor and local Nusselt number along the coil are investigated. It has been shown that in addition to the common affecting parameters, i.e. the coil-to-tube radius ratio and the Dean and Prandtl numbers, the heat transfer performance also depends upon the interactions (expansion and suppression) between the viscous and thermal boundary layers due to secondary flows caused by the centrifugal and torsional forces inherent in coiled tube systems. Upon investigation of the variations of the local dimensionless velocity and temperature along the coil length, it was found that for both heating and cooling conditions, fully-developed hydrodynamic and thermal conditions are not established in the coiled-tube system for the geometric constraints and system boundary and operating conditions used in this work. The case studies performed in this paper indicated approximately 20-30% higher for heating of water (20-30% lower for cooling of air and water) than values of heat transfer coefficients obtained from the reported correlations. The results obtained in this work can be used to correct/adjust the flow and thermal performance used in the design of toroidal and helical coiled tube systems.
A Comparison of Runge Kutta and Novel L-Stable Methods for Real-Time Integration Methods for Dynamic Substructuring
Authors: Gonzalez-Buelga Alicia , Wagg David , Neild Simon , Bursi Oreste S.
Published: April 2008

In this paper we compare the performance of Runge-Kutta and novel L-stable real-time (LSRT) integration algorithms for real-time dynamic substructuring testing. Substructuring is a hybrid numerical-experimental testing method which can be used to test critical components in a system experimentally while the remainder of the system is numerically modelled. The physical substructure and the numerical model must interact in real time in order to replicate the behavior of the whole (or emulated) system. The systems chosen for our study are mass-spring-dampers, which have well known dynamics and therefore we can benchmark the performance of the hybrid testing techniques and in particular the numerical integration part of the algorithm. The coupling between the numerical part and experimental part is provided by an electrically driven actuator and a load cell. The real-time control algorithm provides bi-directional coupling and delay compensation which couples together the two parts of the overall system. In this paper we consider the behavior of novel L-stable real-time (LSRT) integration algorithms, which are based on Rosenbrock's method. The new algorithms have considerable advantages over 4th order Runge-Kutta in that they are unconditionally stable, real-time compatible and less computationally intensive. They also offer the possibility of damping out unwanted high frequencies and integrating stiff problems. The paper presents comparisons between 4th order Runge-Kutta and the LSRT integration algorithms using three experimental configurations which demonstrate these properties.
Feasibility Study on the Use of Dynamic Neural Networks (DNN’s) for Modeling a Variable Displacement Load Sensing Pump
Authors: Li Leslie , Burton Richard , Schoenau Greg
Published: April 2008

The feasibility of using a particular form of neural networks, defined as Dynamic Neural Units (DNU's), to model a pump in a load sensing system is investigated in this paper. Because of the highly complex structure of the pump, its compensators and controlling elements, simulation of load-sensing pump systems pose many challenges to researchers. Several models of pumps, compensators and valves have been developed and published in the literature but they are overly simplified or are in an extremely complex form. One modeling approach which can capture the nonlinear dynamic properties of the pump yet still retain reasonable simplicity in its basic form is to use neural network technology. Previous studies have shown some limited success in using feed forward neurons with dynamic properties being introduced using time delays. A problem referred to a error accumulation has prevented these neural based models from being practical dynamic representations of load sensing systems. Based on the topology of the biological neural systems several new structures, Dynamic Neural Units (DNU's) have been developed. Only one DNU is necessary to capture or represent some of the dynamics of a plant, which a static (feed forward) neuron cannot do. The main advantage of the dynamic neuron is that it reduces the network dimension and the amount of computational requirement and has the potential to avoid this error accumulation problem. The use of Dynamic Neural Networks with Dynamic Neural Units in simulating a variable displacement pump is presented in this paper. Only the pump portion of the load sensing pump system is considered due to problems of interacting operating points. A DNU structure and a DNN (which is comprised of DNU's) are introduced. The simulation results establishes the feasibility of using a Dynamic Neural Networks with DNU's to model a simulated nonlinear hydraulic system such as a load sensing pump.
The Parametric Studies of Brain Materials in the Analysis of Head Impact
Authors: Li Dalong , Ziejewski Mariusz , Karami Ghodrat
Published: April 2008

Crash analysis and head injury biomechanics are very important fields in biomedical research due to the devastating consequences of traumatic brain injuries (TBI). Complex geometry and constitutive models of multiple materials can be combined with the loading conditions in finite element head model to study the dynamic behavior of brain and the TBI. In such a modeling, the proper regional material properties of brain tissues are important. Brain tissues material properties have not been finally determined by experiments, and large variations in the test data still exist and the data is very much situation-dependent. Therefore, parametric analysis should be performed to study the relationship between the material properties and the brain response. The main purpose of presenting this paper is to identify the influence of material constitutive properties on brain impact response, to search for an improved material model and to arrive at a better correlation between the finite element model and the cadaver tests data. In this paper a 3-D nonlinear finite element method will be used to study the dynamic response of the human head under dynamic loading. The finite element formulation includes detailed model of the skull, brain, cerebral-spinal fluid (CSF), dura mater, pia mater, falx and tentorium membranes. The brain is modeled as linear viscoelastic material, whereas linear elastic material behavior is assumed for all the other tissue components. The proper contact and compatibility conditions between different components have been implemented in the modeling procedure. The results for the direct frontal impacts will be shown for three groups of material parameters. The parametrical analysis of tissue material models allows to examines the accuracy of three different set of material parameters for brain in a comparison with the prediction of the head dynamic response of Nahum's human cadaver direct impact experiment. Three sets of suggested material parameters are examined. It is concluded that although all three groups of material models will follow the dynamic behavior of the head and brain behavior, but the parametric data considered in this paper have a closer resemblance to the experimental behavior.
Nondimensional Analysis on the Mitigation of Hard Surface Roughness Induced Torque on Hard Cylinders by Introduction of a Soft Interfacial Layer for Precision Positioning Applications
Authors: Barrett Steven R. H. , Slocum Alexander H.
Published: April 2008

It is widely known that surface roughness and other geometric imperfections can impose a limit on the positioning precision of actuators. The case of a hard cylinder rolling on a hard layer is investigated here, as it is applicable to friction drives. It is proposed that a soft interfacial layer between the drive roller and drive rail can mitigate the effects of geometric imperfections on positioning accuracy. Positioning accuracy is characterized by way of a 'roughness torque', which is the maximum torque that the roller sustains due to roughness of the rail. It is assumed that lower roughness torque values lead to greater positioning accuracy. Finite element analysis and an analytic approach are employed to investigate the situation.
The Effects of Yttrium on the Tensile and Creep Behavior of Thermally Grown Oxide at High Temperature
Authors: Ko G. D. , Sun S. K. , Kang K. J.
Published: April 2008

Recently, It has been revealed that TGO(thermally grown oxide) plays important roles on durability of TBC(thermal barrier coating) systems. In this work, Fecralloy foils were chosen as the substrates which form TGO on the surface at high temperature and the tensile and creep experiments were performed with the thick foils 100 μm at 1200°C. During the experiments the load, displacement and the TGO thickness were monitored in-situ. The effect of Yttrium on the mechanical behavior was investigated using the specimens with two different levels of the concentration. As the results, it was found that Yttrium enhances the strength of TGO as well as that of the substrate at the high temperature.
A Reasoning Process for Armored Face Conveyor Platform Design
Authors: Zhao Wenyan , Zhang Huangao , He Zhen , Tan Runhua
Published: April 2008

Armored Face Conveyor (AFC) is a kind of typical customized product. Different AFCs are similar in function, structure and parameter. In order to obtain new products more efficiently and effectively, it is essential for the AFC to implement Mass Customization. Product platform is common items shared by a set of products and a good way to achieve Mass Customization. Most methods and processes of designing product platform discussed in relative references are processes that common items are found, developed or redesigned. If differentiae of a set of similar products are identified, those parts associated with those differentiae will be customized parts that need to be redesigned each time, and the rest will be integrated into a platform. From that point a reasoning process of designing platform for AFC is put forward. The fishbone diagram, reverse fishbone diagram and a matrix method are introduced, and the analyzing process and steps are discussed.
Control of the Start/Stop of a Diesel Engine in a Parallel HEV: Modeling and Experiments
Authors: Canova Marcello , Sevel Kris , Guezennec Yann , Yurkovich Steve
Published: April 2008

The start/stop of an internal combustion engine is probably the most common feature realizable in passenger car hybrid electric vehicles (HEV), regardless of system configuration and degree of hybridization, to achieve significant fuel economy savings in urban driving. Many examples of this feature are found in production or near-production gasoline hybrid vehicles today, with implementation through either belted starter/alternators or integrated starter/alternators. One of the key factors in the successful implementation of that technology is the ability to start and stop the engine quite fast with no or little unwanted vibrations, requiring a precise closed-loop control of the starter/alternator. This issue becomes even more acute in the case of a Diesel engine, as the instantaneous compression torque is quite large. With this in mind a simplified model of a 4-cylinder Diesel engine dynamics has been developed and identified with experimental data on a recent production, 1.9l Common-Rail Diesel engine. The engine is belt-coupled to a 10.6kW permanent magnet motor and its controller. The system was characterized in the test cell on a dynamometer to calibrate the dynamic model and develop the controller and the hardware was implemented in a mid-size prototype hybrid SUV. In this configuration, the starter/alternator is capable of starting the engine (0-800rpm idle speed) in 200-300ms, and stopping following a prescribed speed trajectory in 500-600ms with little or no vibration induced. Results from the experimental setup and from simulations are shown.
On the Design of the Tubesheet and the Tubesheet-to-Shell Junction of a Fixed Tubesheet Heat Exchanger
Authors: Behseta K. , Schindler S.
Published: April 2008

On the hand of the (mechanical) design of an existing, very large, extreme fixed tubesheet heat exchanger, a C2-Hydrogenation reactor in a petrochemical plant, various code solutions are compared, with each other and with a Finite Element solution based on the Direct Route in Design by Analysis (EN 13445-3, Annex B). The codes and standards used in the investigation are ASME Section VIII, Division 1 (and 2), (TEMA), and EN 13445-3, Clause 13 and Annex J. ASME VIII/2, and TEMA are not appropriate for this design. ASME VII/1 and EN 13445-3 Clause 13 approaches are similar. Differences in maximum permissible pressures result partly from different nominal design stresses. The modern EN 13445-3 Annex J approach, being based on limit analysis theory, leads to very different, much more efficient results. The Direct Route in Design by Analysis confirms the EN 13445-3 Annex J results, but gives, at the same time, clear insight into the behaviour of the whole structure and the various maximum permissible pressure limiting details.
Three-Dimensional Modeling of Plasma Arc in Arc Welding
Authors: Xu G. , Tsai H. L.
Published: April 2008

Most previous three-dimensional modeling work in gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool. Almost all three-dimensional weld pool models are based on the two-dimensional axisymmetric Gaussian assumption of plasma arc pressure and heat flux. In this paper the three-dimensional plasma arc is modeled and results are presented. The velocity, pressure, temperature, current density, and magnetic field of the plasma arc are computed by solving the conservation equations of mass, momentum, and energy, as well as part of Maxwell's equations. This three-dimensional model allows one to study the non-axisymmetric plasma arc caused by external perturbations such as the external magnetic field. It also provides more accurate boundary conditions when modeling the welding pool. The future work is to unify it with the weld pool model and accomplish a complete three-dimensional model of GTAW and GMAW.
Fabrication of Optical Microlenses in Glass Using a Femtosecond Laser for LBA-on-a-Chip Applications
Authors: Cheng Y. , Tsai H. L.
Published: April 2008

We describe the fabrication of microoptical cylindrical and hemispherical lenses vertically embedded in a photosensitive Foturan glass by femtosecond (fs) laser three-dimensional (3D) micromachining. The process is mainly composed of four steps: (1) fs laser scanning in the photosensitive glass to form curved surfaces (spherical and/or cylindrical); (2) postannealing of the sample for modification of the exposed areas; (3) chemical etching of the sample for selective removal of the modified areas; and (4) second postannealing for smoothening the surfaces of the tiny lenses. We examine the focusing ability of the microoptical lenses using a He-Ne laser beam, showing great potential of using these microoptical lenses in lab-on-a-chip applications.
Materials Removals During Femtosecond Laser Non-Thermal Ablation of Dielectrics
Authors: Jiang Lan , Tsai Hai-Lung
Published: April 2008

It remains a big challenge to theoretically predict the material removals mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of non-metals have been based on free electron density distribution without the actual consideration of the phase change mechanism. However, this widely-used key assumption needs further theoretical and experimental confirmations. By combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through non-thermal processes (the Coulomb explosion and electrostatic ablation). The predicted ablation depths and shapes in fused silica, by using 1) the plasma model only and 2) the plasma model plus the two-temperature equation, are both in agreement with published experimental data. The widely-used assumptions for threshold fluence, ablation depth, and shape in the plasma model based on free electron density are validated by the comparison study and experimental data.
Modeling of CO2 Gas Excitation Under CO2 Laser Irradiation
Authors: Jiang Lan , Tsai Hai-Lung
Published: April 2008

Lasers especially multiple laser beams demonstrate unique advantages as energy sources in diamond synthesis. However, the fundamental mechanisms involved in the laser-assisted processes are not Well understood. In a reported amazingly-fast multiple laser coating technique, CO2 gas is claimed as the sole precursor or secondary precursor, which remains poorly understood and unverified. The absorption coefficient changes under the irradiation of the multiple lasers are one of the keys to resolve the mysteries of multiple laser beam coating processes. This study investigates the optical absorption in CO2 gas at the CO2 laser wavelength. This resonance absorption process is modeled as an inverse process of the lasing transitions of CO2 lasers. The well-established CO2 vibrational-rotational energy structures are used as the basis for the calculations with the Boltzmann distribution for equilibrium states and the three-temperature model for non-equilibrium states. Based on the population distribution, our predictions of CO2 absorption coefficient changes as the function of temperature are in agreement with the published data.
Characterization of Silicon Oxide-Based Materials in an Atomic Force Microscope
Authors: Post Marissa J. , Liu J. , Du J. , Schmid S. R. , Ovaert T. , Laurent M.
Published: April 2008

Silicon oxides are widespread in microelectronics and microelectromechanical systems (MEMS) applications. One form of this material that has been suggested as a dielectric in MEMS applications is a carbon-doped form of silicon oxide that can be produced in thin coatings. However, the mechanical properties and wear resistance of these coatings is unknown, and coatings of interest are difficult to characterize because they are very thin. A test methodology has been previously described using extremely sharp diamond tips on a stainless steel cantilever in an atomic force microscope, and this method allows direct calculation of an effective material flow strength at penetration depths as small as twenty nanometers. A number of forms of carbon-doped and undoped silicon dioxide have been evaluated using this methodology. Size effects on material properties are evaluated, and correlations between test methods are presented.
Fuzzy Adaptive Sliding Mode Control of Chaos
Authors: Arjmand Mehdi Tabe , Layeghi Hamed , Salarieh Hassan , Alasty Aria
Published: April 2008

A simple and systematic approach is developed for modeling and adaptive control of an unknown (or uncertain) chaotic system of the formx(n) = f(X) + g(X)u, using only input-output data obtained from the underlying dynamic system. Two different fuzzy identification methods, i.e. least-squares and gradient descent, are used for identifying the unknown functions f(X) and g(X). Based on the fuzzy modeling, an adaptive controller is devised, which works through sliding mode method. The presented procedure is illustrated by using the chaotic system-modified Duffing's equation as an example, on which simulation results demonstrate the effectiveness of the proposed adaptive algorithm.
Modeling of Dynamic Tire Friction Potential on Ice Surfaces
Authors: Ivanovic Vladimir , Deur Josko , Asgari Jahan , Hrovat Davor , Hofmann Otto
Published: April 2008

It has been shown recently that the tire-ice friction is characterized by a significant dynamic potential for abrupt increases of wheel torque at low vehicle speeds. The paper presents experimental identification and modeling of dynamic tire friction potential (DTFP) on ice surfaces. The model is based on the LuGre tire friction model extended with the DTFP effect. The extension is based on the hypothesis that the DTFP is caused by the bristle dwell time effect. The bristle dwell time process is firstly described by a distributed-parameter model, which is then transformed to a lumped-parameter form based on a definition of average tire-bristle dwell time. The calculated bristle dwell time is used to schedule the maximum static friction parameter of the LuGre model. The extended tire friction model is validated against the experimental data for different operating conditions.
Preliminary Study on Nanometer-Scale Gamma-Alumina Powder Densification Through Vibration
Authors: Cao M. , Arsenault S. , Mosher D. A.
Published: April 2008

Lightweight, compact hydrogen storage has been one of the major bottlenecks in developing fuel cell systems applicable to powering ground vehicles. In this study, preliminary experimental examinations have been performed to evaluate vibratory densification of nanometer-scale powder particles, which directly affects the volume and weight of storage systems based on complex hydrides such as NaAlH4. Since NaAlH4 is is reactive with moisture and oxygen, and thus not possible to test in air, γ-alumina (gamma-aluminum oxide) with a similar average particle size (~50 nm) is applied as a surrogate material in this preliminary investigation. An apparatus including a tube test section to quantify the densification of a column of powder was developed for this study. Comprehensive testing has been carried out to identify the optimal vibration conditions achieving the highest densities. The study investigates the effectiveness of 1-dimensional and 2-dimensional vibration, as well as the impact of frequency patterns (constant frequency and frequency sweeping). Offering fundamental understanding of nano-powder densification using shakers, this experimental investigation provides guidelines for further study of vibration-based hydride powder densification.
Promoting Active Learning in Mechanical Engineering
Authors: Carvalho I. S.
Published: April 2008

In order to promote active learning in a Mechanical Engineering course a learning/teaching methodology which comprises several distributed activities is introduced, hence providing a wider choice and opportunity for students' effective learning. An online collaborative environment is implemented using different technologies, namely a mail box and a discussion forum. This methodology allows students a wider choice and diversity of practices and promotes contact with real world applications, while contributing for students' learning motivation and creativity enhancement.
Shock Reduction for Electronic Components Within a Projectile
Authors: Chakka Vinod , Trabia Mohamed B. , O'Toole Brendan , Sridharala Srujanbabu , Ladkany Samaan , Chowdhury Mostafiz
Published: April 2008

Electronic components within a projectile are subjected to severe loads over extremely short duration. Failure of these components is likely to have negative implications to the projectile or mission. While experimental data can be helpful in understanding the failure phenomena, collecting such data is usually difficult. There are also limitations on the reliability of sensors under these circumstances. Finite element modeling (FEM) can offer a means to better understand the behavior of these components. It can also be used to design better techniques to mitigate the shocks these components are subjected to. A model of a typical projectile and the gun barrel is presented. The projectile is modified to include a payload of a one-pound mass that represents a typical electronic package, which is supported by a plate. The model, which is subjected to a realistic launch pressure-time history, includes the effects of friction between the gun barrel inner surface and the projectile. The effect of the flexibility of the gun barrel on the vibrations of the electronic package is also considered. This paper proposes using a composite plate, with carbon fibers embedded in an epoxy matrix, to reduce the shocks transmitted to the payload. A parametric study of the effects of varying the thickness of the supporting plate and the fiber volume fraction on accelerations and stresses is included.
Experimental and Numerical Study of the Effect of Plastic Ball Grid Array Package Placement on PWB Warpage During Convective Solder Reflow
Authors: Powell Reinhard E. , Tan Wei , Ume I. Charles
Published: April 2008

Warpage has long been known to cause thermomechanical reliability problems in electronic packaging. The coefficient of thermal expansion (CTE) mismatch between different materials in an electronic assembly such as solder, copper, FR-4, encapsulation molding, and silicon is known to be one of the leading causes of manufacturing defects and fatigue failures. The CTE mismatch between packaging materials induces thermomechanical stresses at interfaces between the materials. Warpage is a global effect of interfacial stress and displacement. The warpage problem in electronic packaging can be further aggravated by thermal processes such as reflow and temperature cycling. In a printed wiring board assembly (PWBA), warpage of the PWB or chip packages may result in chip package misregistration, solder joint failure, die cracking and delamination of the solder bumps between chip packages and the PWB. In this paper, the warpage of a printed wiring board assembly (PWBA) is studied using projection moire´ experimental measurements and a finite element model. The effects of plastic ball grid array (PBGA) chip package placement on PWB warpage during convective reflow will be evaluated. The projection moire´ experimental warpage results will show that the number of PBGA chip packages as well as their location has an effect on the warpage of the PWB. In addition to the experimental results, the finite element warpage results will be used to make recommendations on the optimal PBGA package placement locations on the PWB to minimize PWB warpage during reflow processes.
Heat Transfer Enhancement in a Horizontal Channel by the Addition of Curved Baffles
Authors: Luviano J. L. , Hernandez A. , Rubio C. , Banerjee D.
Published: April 2008

This paper presents the heat transfer and fluid dynamics analysis of a horizontal channel formed by parallel plates with periodic insertions of heated blocks, having curved deflectors to direct the flow. The heat transfer coefficient investigated is compared with that of the horizontal channel without deflectors. The aim of the deflectors is to lead the fluid to the space between the heated blocks increasing the dynamics in this area. This zone will normally, without deflectors, become a stagnant fluid zone in which low energy transfer rate occurs. The results show that the heat transfer coefficient is larger as compared to that of the case without deflectors. The increment in the heat transfer coefficient is due primarily to the fluid motion stirred in the area between the heated block due to the deflectors. However, it must be pointed out. This implementation also increases the pressure drop in the channel.
A Novel Projection Moire´ System for Measuring PWBA Warpage During Simulated Optimized Convective Reflow Process
Authors: Powell Reinhard E. , Tan Wei , Ume I. Charles
Published: April 2008

The shadow moire´ technique is a widely used method of measuring printed wiring board (PWB) warpage. It has a high resolution, high accuracy and is suitable for use in an online environment. A shortcoming of the shadow moire´ technique is that it cannot be used to measure PWBs populated with chip packages. In this paper, a novel warpage measurement system based on the projection moire´ technique is presented. The system can be used to measure bare PWBs as well as PWBs populated with chip packages. In order to use the projection moire´ system to accurately determine the warpage of PWBs and chip packages separately, an automated chip package detection algorithm based on active contours is utilized. Unlike the shadow moire´ technique which uses a glass grating, the projection moire´ technique uses a virtual grating. The virtual grating sizes can be adjusted, making it versatile for measuring various PWB and chip package sizes. Without the glass grating, which is a substantial heat inertia, the PWB/PWBA/chip package sample can be heated more evenly during the thermal process. The projection moire´ system described in this paper can also be used to measure PWB/PWBA/chip package warpage during convective reflow processes. In this paper, the characteristics of the projection moire´ warpage measurement system will be described. In addition, the system will be used to measure the warpage of a PWB and plastic ball grid array (PBGA) packages during a Lee optimized convective reflow process. It is concluded that this projection moire´ warpage measurement system is a powerful tool to study the warpage of populated PWBs during convective reflow processes.
Identification of Vertical Exciting Force on the Surface of an Elastic Half-Space Using Sensor Fusion
Authors: Hamidzadeh Hamid R. , Luo Albert C. J.
Published: April 2008

An analytical technique for identification of the location of an unknown vertical exciting force on the surface of ground using sensors fusion is presented. The analysis is based on the dynamic responses of points on the surface of an elastic half-space medium subjected to a vertical, harmonic and concentrated force on the surface. The medium is assumed to be an elastic, isotropic and homogeneous half-space. The problem is analytically formulated by employing double Fourier transforms, and the solution is obtained in the form of integral expressions in terms of Rayleigh functions. Numerical techniques are utilized for the computation of integrals presented by the inverse transforms. Non-dimensional values for the in-phase and quadrature components of the displacements for any position on the surface of the unloaded half-space in terms of frequency and position of the exciting force are presented for a Poisson's ratio of 0.25.
Resonance of Rubber Tubes Generated by Air Force Ultrasound Transducers
Authors: Zhang Xiaoming , Greenleaf James F.
Published: April 2008

In paper, we report our recent results of using the air force ultrasound transducer to study the resonance of rubber tubes. Experiments were carried out on a rubber latex tube. Seven resonant frequencies were measured between 50 Hz and 200 Hz. Theoretical calculation of the resonant frequency on the tube was done with the wave propagation approach. The relative differences of the seven resonant frequencies between the experiment and the theory are less than 6 %. This research shows that the air force ultrasound transducer can be used for tube resonance measurement.
Comparison of Piezoelectric, Magnetostrictive and Electrostrictive Hybrid Hydraulic Actuators
Authors: John Shaju , Sirohi Jayant , Wang Gang , Wereley Norman M.
Published: April 2008

In recent years, active material driven actuators have been widely researched for potential applications in the fields of aerospace, automotive and civil engineering. While most of these active materials, such as piezoelectric, magnetostrictive and electrostrictive materials, have high force and bandwidth capabilities, they are limited in stroke. In combination with hydraulic systems, the field dependent motion of these materials can be amplified to produce high force, high stroke actuators. In a hybrid hydraulic pump, the motion of an active material is used to pressurize a hydraulic fluid. Since the properties of active materials vary greatly in terms of free strain and block force, there is a need to identify the optimum active material for a particular application. This study compares four active materials, Lead-Zirconate-Titanate (PZT), Lead-Magnesium-Niobate (PMN) and Terfenol-D, as the drivers of a hybrid hydraulic actuation system. The performance of each of these active materials was evaluated in the same hydraulic actuator through systematic testing of the actuator while maintaining the same length and volume for each active material. In each case, the active material had a length of around 54 mm and a cross-sectional area of 25 mm2. Commonly used metrics such as output power and electromechanical efficiency are used for comparison. Of the four materials tested in this study, PMN presented the largest free strain (2000με), while Terfenol presented the least (1000με). The highest no-load velocity was also exhibited by the PMN based actuator (270mm/s). The maximum output power obtained was 2.5W for both PMN and Terfenol-D based actuators while the highest electromechanical efficiency obtained was 7% for the PMN based actuator.
Thermo-Mechanical Behavior of a Micromirror for Laser-to-Fiber Active Alignment Using Bimorphs With Breakable Tethers
Authors: Kitagawa Hajime , Boteler David J. , Lee Yung-Cheng
Published: April 2008

We will present a novel micromirror design in which tethered bimorph strips are used for mirror active alignment including beam steering and position fixing. A micromirror is attached to bimorphs that are pre-stressed at room temperature. A series of tethers link the bimorphs to the substrate to restrain their deformation. Breaking a tether by Joule heating allows the deformation of the bimorph to increase, changing the mirror position and orientation for precision alignment. With a large number of tethers, an optimum alignment can be achieved after breaking a selected group of tethers. We also report the experimental results of devices fabricated.
From Experimentation to Analysis: Considerations for Determination of the Metal/Mold Interfacial Heat Transfer Coefficient via Solution of the Inverse Heat Conduction Problem
Authors: Woolley Jonathan W. , Pohanka Michal , Woodbury Keith A.
Published: April 2008

Casting solidification simulation has been established as an effective tool used to improve the efficiency of the casting design process. Knowledge of the interfacial heat transfer coefficient at the metal/mold interface of metal castings is crucial to the simulation of casting solidification. The characterization of the heat transfer from metal to mold has been the focus of many researchers. The solution of the inverse method has been used to determine the interfacial heat flux and/or the interfacial heat transfer coefficient (IHTC) and has been applied to a variety of casting techniques and geometries. While the inverse method is a legitimate technique to determine the metal/mold interfacial heat transfer coefficient, there are a number of important issues to consider before applying the method to actual castings. The present work is a discussion of practical and important issues related to various common casting techniques that must be considered when collecting temperature measurements to be used in an inverse calculation and when developing a heat transfer model of the system.
Flow Field in the Vicinity of a High-Pressure-Drop Ball Valve
Authors: Jiang Lei-Yong , Depooter Keith , Carscallen William
Published: April 2008

The testing of gas turbine combustors requires large flow rates at high pressures and elevated temperatures. In order to control the flow and pressure inside the combustor, some type of control valve is required in the exhaust section of the testing system. This backpressure valve is exposed to severe operating conditions. To understand the complex flow features in the exhaust section and provide relevant information for selecting suitable low-cost valves for new large test cells, a numerical study was carried out on a backpressure valve that has been used in a number of testing programs. The flow fields in the vicinity of the valve and the piping sections ending at the exhaust stack were resolved for three practical operating conditions. The results indicate that because of the presence of the valve with a V-shape opening, the flow field behind experiences a series of three-dimensional expansion and shock waves. The strong interactions exist between the flow behind the blockage and the flow passing through the opening area. More importantly, it is found that most of the pressure drop occurs immediately downstream of the valve, and its values are much larger than those provided by suppliers based on shock-free flow calculation. This may explain why the valve lost its function during testing and its stainless-steel seat had to be removed in order to maintain its rotational function. Based on this study, it is recommended that a second pressure-drop element be installed in the exhaust section in order to keep the expected lifetime of valves and reduce noise level. This suggestion has been implemented in the new large test cell at the Gas Turbine Laboratory.
Electrical Energy Harvesting Using a Mechanical Rectification Approach
Authors: Tieck R. M. , Carman G. P. , Lee D. G. Enoch
Published: April 2008

This paper presents a new approach using frequency rectification to harvest electrical energy from mechanical energy using piezoelectric devices. The rectification approach utilizes a linearly traveling Rectifier to impart vibrational motion to a cantilever piezoelectric bimorph. A conventional cantilever-type energy harvester is tested aside the rectified beam. The Standard beam generated 0.11 W of power, a power density of 15.63 kW/m3, and an energy density of 130.7 J/m3. The Rectified beam generated 580 mW of power, a power density of 871.92 kW/m3, and an energy density of 313.15 J/m3, a factor 2.4 greater than conventional energy harvesting methods. These results confirm the original thesis that a mechanically rectified piezoelectric Energy Harvester would generate larger Energy and Power Densities as well as Specific Powers, compared to conventional technologies.
Manufacturing Methods for Producing Water Pasteurization Indicators (WAPI)
Authors: Kumagai Akihiko , Liu Tien I. , Khan Minhaj , Yu Scott , Wargala Brian , Little Anthony , Johnson Robert , Bear Jeff
Published: April 2008

Securing safe drinking water in developing countries is a significantly important problem for engineers to be aware of. Out of 6.5 billion people in the world, 1.1 billion people still do not have access to safe drinking water in their daily lives. A team lead by the Department of Biological Science at our institution developed a prototype device called Water Pasteurization Indicator (WAPI). This device is used to check if water temperature heated by a solar ray reflector panel reached above the pasteurization temperature. The WAPI consists of Carnauba wax in a polycarbonate tube with both ends sealed, a washer for adding weight and setting up the orientation of a WAPI when it is submerged in water, and a fishing string for pulling the WAPI out of water. This paper describes development of a mass-production method for WAPIs. It is essential to establish a mass production method for WAPIs so that it can be made available to people in developing countries in large quantities with an affordable price. The manufacturing method was developed considering appropriate technologies which can be adapted by people in developing countries. In addition, the manufacturing method should be simple, economical, productive, and consistent in quality of WAPIs produced. After the prototype WAPI processing device was developed, a full-factorial design of experiment (DOE) was conducted to optimize three critical process parameters for sealing both ends of a polycarbonate tube by a pair of heat-clamping plates. These parameters are claming temperature, claming time, and clamping gap. During the period of Summer 2004 through Spring 2005, approximately 2000 WAPIs were produced by the WAPI processing device and were sent to Kenya and Tanzania, and all were tested to work successfully.
Tracking the Performance of Heavy Axle Load Vehicles in Revenue Service
Authors: Harrison Harold D. , Cheng Li R. , GeMeiner William
Published: April 2008

As market forces drive up the gross weight on rail, railroads continue moving toward increased usage of heavy axle load (HAL) equipment, namely 286,000 lb and 315,000 lb GWR vehicles that provide more competitive and efficient transportation. According to the AAR's Universal Machine Language Equipment Register (UMLER) database, since 1995, at least 70% of vehicles built each year were HAL vehicles. 2005 had 49,923 more HAL vehicles running on the North America railroad system than the previous year. This practice can result in significant overall savings in operating costs. However, HAL equipment can also accelerate wear and damage to the railroad infrastructure and have a greater potential for truck warping and vehicle dynamics problems. Thus, keeping rolling stock and track safe while ramping up the usage of HAL equipment presents a significant challenge. Wheel Impact Load Detector (WILD) SuperSites, developed by Salient Systems Inc. (SSI), provide real time monitoring and alarming on excessive axle loads and vehicle dynamics. SuperSites are important tools in the scientific study of HAL vehicles and the monitoring of heavy haul operations. This paper provides a snapshot of results of studies conducted on Union Pacific (UP) HAL routes and demonstrates how HAL loads affect the rolling stock, the track, and the wheel/rail interaction. The heavier the load, the higher the impact of the defective wheels to the track; therefore, heavily loaded vehicle routes (such as the coal route from the Powder River Basin to Kansas City and the primary intermodal route from Los Angeles to El Paso) need to be monitored more proactively to avoid track structural damage.
Multi-Frequency Multi-Modal Excitation of a Heated Annular Plate
Authors: Arafat Haider N. , Nayfeh Ali H.
Published: April 2008

The forced nonlinear dynamics of a pre-buckled thermally loaded annular plate are investigated. The plate is modeled using the von Ka´rma´n plate theory and the heat equation. The heat, which is generated by the difference between the uniformly distributed temperatures at the inner and outer boundaries, is assumed to symmetrically flow in the radial direction. The amount of heat affects the natural frequencies, which may give rise to different internal resonance conditions. The method of multiple scales is used to examine the system axisymmetric responses when it is driven by an external multi-frequency excitation. The plate responses could be very complex exhibiting Hopf and cyclic-fold bifurcations, quasi-periodicity, chaos, and multiplicity of attractors.
A Real-Space Parallel Optimization Model Reduction Approach for Electronic Structure Computation in Large Nanostructures Using Orbital-Free Density Functional Theory
Authors: Negrut Dan , Anitescu Mihai , El-Azab Anter , Benson Steve , Constantinescu Emil , Heyn Toby , Zapol Peter
Published: April 2008

The goal of this work is the development of a highly parallel approach to computing the electron density in nanostructures. In the context of orbital-free density functional theory, a model reduction approach leads to a parallel algorithm that mirrors the subdomain partitioning of the problem. The resulting form of the energy functional that is subject to the minimization process is compact and simple. Computation of gradient and hessian information is immediate. The salient attribute of the proposed methodology is the use of model reduction (reconstruction) within the framework of electronic structure computation.
Stabilized Time-Discontinuous Galerkin Methods With Applications to Structural Acoustics
Authors: Thompson Lonny L. , Kunthong Prapot
Published: April 2008

The time-discontinuous Galerkin (TDG) method possesses high-order accuracy and desirable C-and L-stability for second-order hyperbolic systems including structural acoustics. C- and L-stability provide asymptotic annihilation of high frequency response due to spurious resolution of small scales. These non-physical responses are due to limitations in spatial discretization level for large-complex systems. In order to retain the high-order accuracy of the parent TDG method for high temporal approximation orders within an efficient multi-pass iterative solution algorithm which maintains stability, generalized gradients of residuals of the equations of motion expressed in state-space form are added to the TDG variational formulation. The resultant algorithm is shown to belong to a family of Pade approximations for the exponential solution to the spatially discrete hyperbolic equation system. The final form of the algorithm uses only a few iteration passes to reach the order of accuracy of the parent solution. Analysis of the multi-pass algorithm shows that the first iteration pass belongs to the family of (p+1)-stage stiff accurate Singly-Diagonal-Implicit-Runge-Kutta (SDIRK) method. The methods developed can be viewed as a generalization to the SDIRK method, retaining the desirable features of efficiency and stability, now extended to high-order accuracy. An example of a transient solution to the scalar wave equation demonstrates the efficiency and accuracy of the multi-pass algorithms over standard second-order accurate single-step/single-solve (SS/SS) methods.