bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing Mechanical Responses of Microstructures From Optical Heating
Authors: Wong C. Channy , Spahn Olga B. , Phinney Leslie M.
Published: April 2008

Optical microswitches are being developed for use in communication and security systems because of their small size and fast response time. However, as the intensity of the light incident on the microswitches increases, the thermal and mechanical responses of the reflective surfaces are becoming a concern. It is important to dissipate heat adequately and to minimize any deformation on the reflective surfaces. To understand the mechanical responses of these microswitches, a set of microstructures have been fabricated and tested to evaluate how the surfaces deform when irradiated with a high-intensity laser beam. To evaluate and further investigate the experimental findings, the coupled physical analysis tool, Calagio, has been applied to simulate the mechanical behavior of these test structures when they are optically heated. Code prediction of the surface displacement will be compared against measurement. Our main objective is to assess the existing material models and our code predictive capability so that it will be used to qualify the performance of micro-switches being developed.
Band Gap Engineering in N-Dimensional Phononic Crystals
Authors: Kushwaha Manvir S.
Published: April 2008

Periodic binary elastic/acoustic composites can give rise to genuine band gaps in the band structure. The term genuine refers to the complete gaps, which persist independently of the polarization of the wave and of its direction of propagation. Within these complete gaps sound and vibrations are forbidden, the "acoustic crystals" stand still, and the total silence reigns. Thus a vibrator (or defect) introduced into a periodic elastic composite would be unable to generate sound or vibrations within the gap. The existence of complete gaps in the band structure is closely associated with the (classical) Anderson localization of sound and vibrations. The search for phononic band-gap materials is of comparable interest to the pursuit of photonic band-gap materials. Thus the phononic crystals are to acoustics as photonic crystals are to optics. In comparison to the photonic crystals, there are additional parameters (the mass densities and two velocities - longitudinal and transverse) involved in the phononic crystals, which make the physics richer and leaves us with more options in the quest of creating full stop bands in the system. As regards the applications, the phononic crystals are envisioned to find ways in the acoustic waveguides, improvements in designing the transducers, elastic/acoustic filters, noise control, ultrasonics, and medical imaging, to name a few. Since the interesting phenomena emerging from the phononic crystals are all consequences of the existence of the gap(s), a major part of the research efforts has focused on the search for phononic band-gap crystals. As such, we report and emphasize on the spectral gaps in the band structure for cleverly synthesized N-dimensional (N = 1, 2, 3) phononic crystals. PACS numbers:
Development of No Flow Underfills for Lead-Free Flip Chip Applications
Authors: Nagarkar Kaustubh , Zhang Tan , Esler David , Simon David , Gillespie Paul , Tonapi Sandeep , Susarla Prameela , Mills Ryan
Published: April 2008

Flip chip packaging is one of the fastest growing segments in electronics packaging technology. The semiconductor packaging industry is continuing to migrate towards Pb-free electronics assembly. Therefore, the development of compatible materials for Pb-free flip chip packaging is critical to this transition [1]. Flip chip devices are commonly underfilled to compensate for the mismatch in the Coefficient of Thermal Expansion (CTE) between the die and the chip carrier. The No Flow Underfill (NFU) process is a type that can increase the throughput of the flip chip assembly process and reduce manufacturing costs. Significant research has been performed to develop NFUs for eutectic applications. However, further research is required for the development of NFUs that are compatible with the Pb-free solders and the high temperature reflow process associated with these solders. In this paper, the challenges associated with the development of 'filled' underfill formulations for assembly with the 95.5Sn/3.8Ag/0.7Cu bumped flip chip devices are discussed. The effects of process variables that affect voiding in the underfill layer have been presented. The impact on voiding due to stencil printing of the underfill has been discussed. The impact on assembly reliability due to the underfill material properties has also been reported.
Computer Simulation of Warpage Formation in Polymer Injection Molding of a Step Pad
Authors: Ramamurthy Sridhar P. , Steenson Lyle , Hu Zhong
Published: April 2008

Warpage is one of the most common defects of a plastic product in the polymer injection molding process. It is attributed to the differential shrinkage after the part is ejected from the die cavity due to the nonlinear material property of the polymer, improper design of the cooling system, geometry of the part and the related process parameters. In this paper, the warpage formation of a plastic part, Step Pad of polypropylene copolymer, in the cooling stage of the polymer injection molding process was simulated by finite element analysis (FEA). A three-dimensional FEA model, taking into account the nonlinear material (polypropylene copolymer) properties, with a thermal-structural sequential coupled approach of higher computing efficiency was developed. The effects of mold closed time and layout of cooling system on the dimension and shape of the part were investigated. Industrial experiments for the different mold closed times (25s, 30s, 35s, 40s, 45s, 50s, and 55s) were conducted. The simulation results were compared with the experimental results. The approach is effective in predicting warpage in the polymer injection molding processes.
A Hydraulic Fan Driven Heat Exchanger for Automotive Cooling Systems
Authors: Frick Peyton , Bassily Hany , Watson Heather , Wagner John
Published: April 2008

Hydraulics are widely applied in transportation and manufacturing systems due to their high power density, design flexibility for power transmission, and ease of computer control. One fluid system application that merits investigation is the internal combustion engine advanced thermal management system which replaces the traditional mechanical coolant pump and radiator fan with computer controlled components. Although electric servo-motors may be integrated to drive these mechanical loads, the power demands often require large actuator sizes and electrical currents. An alternative to dc motors are hydraulic driven motors which offer higher torques in a smaller package space. In the paper, an automotive heat exchanger will be investigated that features a computer controlled hydraulic actuated fan. A series of dynamic models will be presented for the radiator, fan assembly, and hydraulic circuit. For comparison purposes, two radiator models are developed using heat transfer concepts for a cross flow heat exchanger. The ε-NTU method is a standard methodology for heat exchanger analysis involving a logarithmic mean temperature difference of the fluids. In contrast, the Nusselt method uses temperature differential equations for fluids in cross flow to calculate an average temperature difference. Representative numerical results will be presented to demonstrate transient responses of the hydraulic components as well as the radiator temperature.
Micro-Surface Construction and Characterization From Digital Elevation Model Using Thin Plate Splines in Matlab Environment
Authors: Mayyas Mohammad , Shiakolas Panos S.
Published: April 2008

The Thin Plate Splines (TPS) theory is modified and employed in the reconstruction of 2D 1/2 unfolded micro-topographical surfaces. The modified TPS allows the reconstruction of MEMS structures based on sampled digital elevation model (DEM). The developed algorithms are implemented in MATLAB and applied to restore bad samples, enhance surface reconstruction, and compensate for surface irregularities for micromachining purposes. In addition, the restored surface reveals the scale components of the real surface (roughness, waviness and form). The irregularity of meso, micro and nano surfaces is then characterized into slope, curvature, strike, dip, azimuth and energy surfaces. It is concluded that the simplicity, differentiability of TPS and roughness components relaxation make the proposed theory advantageous on reconstruction and characterization of micro surfaces for a variety of applications.
Event-Based Haptic Representation of Small Surface Features
Authors: Fiene Jonathan , Niemeyer Gu¨nter
Published: April 2008

This work seeks to extend the paradigm of event-based haptics through analysis and simulation of the dynamics of probe-based interactions with small surface features. As the preliminary work in this area, this paper focuses on the case of moving a probe down a step from a high surface to a lower one. Event parameters can be computed from measurements of velocity and contact force as the probe is traversed across a small step height change in a real material. These parameters are then used to simulate the same change in a virtual environment. Comparison with standard position-based renderings of step discontinuities show significant improvements in perceived realism using the event-based approach.
The Effect of Welding Self-Equilibrating Stresses on the Natural Frequencies of Thin Rectangular Clamped Plate
Authors: Al-Ammri A. Salam
Published: April 2008

In this paper an investigation has been made into the effect of residual stresses on the vibration characteristics of thin rectangular clamped plate. General frequency equations with and without the effect of residual stresses due to multi-lines of heating or welding along the length and width of the plate have been obtained. The validity of the equations obtained was checked with available special solutions with a good agreement.
The Effect of Solid Particle Erosion on the Mechanical Properties and Fatigue Life of Fiber-Reinforced Composites
Authors: Yang N. H. , Nayeb-Hashemi H.
Published: April 2008

The effect of solid particle erosion on the strength and fatigue properties of E-glass/epoxy composite was investigated. Solid particle erosion with SiC particles of 400 μm to 500 μm in diameter was simulated on 12 ply [45°/-45°/0°/45°/-45°/0°]s E-glass/epoxy composites with a constant particle velocity of 42.5 m/s and solid particle to air volume ratio of 6 kg/m3 at impact angles of 90°, 60°, and 30° for 30, 60, 90 and 120 seconds. Damaged and undamaged specimens were subjected to tensile tests while monitoring their acoustic emission (AE) activity. An erosion damage parameter was defined as a function of the particle impact angle and erosion duration to determine the residual tensile strength of the composite. Scanning electron microscope (SEM) images of the erosion damaged specimens revealed the same damage mechanism occurred at different impact angles. The AE stress delay parameter was used to predict the residual tensile strength of erosion damaged composites. Tension-tension fatigue tests were performed on virgin specimens and specimens exposed to erosion damage of 60 seconds and 90 seconds at 90° particle impact angle to observe the effects of erosion damage on the fatigue life. A modified Basquin's equation was defined to predict the fatigue life of the erosion damaged specimens.
Research on Electro-Hydraulic Control of Propellers of the Underwater Vehicles With Switch-Mode Hydraulic Power Supply
Authors: Cao Jianwei , Gu Linyi , Wang Feng , Chen Ying
Published: April 2008

Switch-mode hydraulic power supply is a hydraulic pressure converting unit made of some distributed hydraulic components, which can boost or buck hydraulic pressure continuously with low power loss (about 20%)and continuous flow-rate. There are two types of switch-mode hydraulic power supply, pressure boost and pressure buck. (see "Switch-mode Hydraulic Power Supply Theory", 2005 ASME, IMECE-FPST No.79019)[1]. This paper introduces a new propeller driving system using the motor of the switch-mode hydraulic power supply for the underwater vehicle. And PFM (Pulse Frequency Modulation) control of high-speed switch-valves is applied to adjust the rotation speed of the propeller. The system has advantages over the widely used servo-valve valve-control system and pump-control system on the energy-weight ratio, anti-contamination performance and energy-saving capacity.
Improvement in Mechanical Properties of Clay Filled Carbon-Epoxy Composite
Authors: Zhou Yuanxin , Pervin Farhana , Hamilton Jamese , Jeelani Shaik
Published: April 2008

In the present investigation, a high intensity ultrasonic liquid processor was used to obtain a homogeneous molecular mixture of epoxy resin and K-10 MMT clay. The clay were infused into the part A of SC-15 (Diglycidylether of Bisphenol A) through sonic cavitations and then mixed with part B of SC-15 (cycloaliphatic amine hardener) using a high speed mechanical agitator. The trapped air and reaction volatiles were removed from the mixture using high vacuum. Flexural tests were performed on unfilled, 1wt. %, 2wt. %, 3 wt. % and 4 wt.% clay filled SC-15 epoxy to identify the loading effect on mechanical properties of the composites. The flexural test results indicate that 2.0 wt% loading of clay in epoxy resin showed the highest improvement in strength as compared to the neat systems. After that, the nanophased matrix with 2 wt.% clay is then utilized in a Vacuum Assisted Resin Transfer Molding (VARTM) set up with satin weave carbon preforms to fabricate laminated composites. The resulting structural composites have been tested under flexural and tensile loads to evaluate mechanical properties. 13.5% improvement in flexural strength and 5.8% improvement in tensile strength were observed in carbon/epoxy nanocomposite. TGA and DMA tests were also conducted to observe the thermal stability of the structural composite.
Revising Thermo/Fluids Education for the 21st Century
Authors: Scott Timothy C. , Ribando Robert J.
Published: April 2008

During the 1960s, major revisions took place in undergraduate thermo/fluids (thermodynamics, fluid mechanics and heat transfer) textbooks and in the pedagogy used to teach these disciplines. In the decades since, students and instructors have both changed. Many students arrive with less-than-adequate mathematics and study skills, rely almost exclusively on the Internet for reference materials, and have very little "hands on" knowledge of how things work. The number of instructors with practical expertise or industrial experience has decreased markedly as well. Yet the methods by which material is presented and the tools and resources students are exposed to have not changed sufficiently. In contrast, the tools available in industry have improved significantly and the knowledge needed by graduates to use these tools has not kept pace. This paper looks at how thermo/fluids has evolved over the past five decades and points out some areas that are not receiving sufficient attention. These include the use of computers as teaching aids, the training of students in the software packages prevalent in modern industry, and the need to update the database of design information. The almost exclusive use of the Internet and other non-refereed sources of information by students is also a significant problem that needs addressing.
An Optimal Control Approach to Minimizing Entropy Generation in an Adiabatic IC Engine With Fixed Compression Ratio
Authors: Teh Kwee-Yan , Edwards Christopher F.
Published: April 2008

Entropy generation due to combustion destroys as much as a third of the theoretical maximum work that could have been extracted from the fuel supplied to an engine. In this paper, an optimal control problem is set up to minimize the entropy generation in an adiabatic internal combustion engine, with the piston velocity profile serving as the control input function. The compression ratio of the engine is fixed, thereby imposing a constraint on the piston motion. The switching conditions for the optimal bang-off-bang control is determined based on Pontryagin's maximum principle. In thermodynamic terms, the optimal solution reduces to a strategy of equilibrium entropy minimization. This result is independent of the underlying combustion mechanism.
Design of Simulation Tools for Trainig Programs in Lean Manufacturing
Authors: Verma Alok , Devulapalli Jyotsna
Published: April 2008

A physical simulation based activity in the form of a board game has been developed to explain the concepts of Value Stream Mapping (VSM) and analysis. The activity explains the basic concepts of Value Stream Mapping, drawing of the Current state map, development of Future state map, and implementation of the future state. Simulation activity is run in three phases and the results of implementing various lean tools are observed. Effects of various tools like the Supermarket, Kanban, and Pull system are observed in a learn-by-doing environment. This simulation activity can be used to compliment training programs in Lean manufacturing.
Turning ABET Accreditation Review Into a Continuous Improvement Process
Authors: White Phillip R.
Published: April 2008

For many engineering programs, the assessment required for ABET accreditation results in little actual improvement in the educational program and is viewed by many faculty simply as a hurdle to be overcome to maintain accreditation. Particularly tedious is the assessment of the achievement of the ABET (a-k) program educational outcomes. One innovative approach to minimize the work involved in assessing the achievement of the (a-k) program educational outcomes is based on the establishment of course outcomes for each required course along with a mapping of the course outcomes to the (a-k) program educational outcomes. Course outcomes are the required topics that are to be covered in each required course and are the topics whose achievement are normally assessed through tests, homework, quizzes, reports and presentations. Collecting data on achievement of course outcomes places little additional burden on instructors because the data is readily available in grade records normally created for each course. The mapping of course outcomes to (a-k) program educational outcomes indicates which of the (a-k) outcomes each course outcome addresses. Therefore using the course outcome achievement data provided by each instructor from their grade records and the mapping of course outcomes to (a-k) program educational outcomes, the achievement of the (a-k) program educational outcomes by the entire curriculum can be relatively easily assessed. The process of establishing and assessing course outcomes not only addresses the assessment of achievement of the (a-k) program educational outcomes but it can also easily lead to continuous improvement of the curriculum. Continuous improvement can result when assessment is done periodically and the results are discussed by faculty groups responsible for each course. The establishment of course outcomes and their achievement assessment can lead to serious dialog about what is being taught in each course and the continuity between courses. Instruction and testing are more focused and improved because faculty know they must provide assessment data for each outcome. And finally the strengths and weaknesses in the curriculum as a whole are determined when the mapping is used to assess the overall achievement of the (a-k) program educational outcomes.
On the Crosswind Stability of High Speed Railway Vehicles
Authors: Wetzel Christian , Proppe Carsten
Published: April 2008

The crosswind stability against overturning is a major design criterium for high speed railway vehicles. Due to the increasing interoperability in Europe it has also become an important international task. In recent years efforts have been made to derive an uniform rule in certifying railway vehicles. In this case especially probabilistic methods have been proposed These probabilistic techniques are common design criteria for wind turbines. A sophisticated method to compute the reliability of railway vehicles under strong crosswind is presented. In consideration of the given gust signal and the high-frequency turbulent fluctuations of the wind the response of a simplified train model is computed. The major failure criterion to determine the reliability is the lowest wheel-rail contact force of the railway vehicle. Special attention is given to the stochastic modeling of the high-frequency turbulent fluctuations of the wind and to the effect of these fluctuations on the crosswind stability.
Multiplexed Force Control of Pneumatic Muscles
Authors: Jouppila V. , Ellman A.
Published: April 2008

Pneumatic actuators are often used in applications that require high power-to-weight ratio, combined with low price and clean and fast operation. However, due to the compressibility of air and highly nonlinear behavior of seal friction, the position and force control of these actuators is difficult to manage. As a result, pneumatic cylinders have been used for many years solely in simple repetitive tasks requiring only a very limited amount of system control. Nonetheless, the pneumatic actuators have properties such as compactness, high power-to-weight ratio, and simplicity that are desirable features in advanced robotics. To overcome the shortcomings, a number of advanced pneumatic components have been developed, of which the most promising is the pneumatic muscle. Compared to a cylinder, a pneumatic muscle not only has a higher power-to-weight and power-to-volume ratio but it is also almost frictionless and has zero leakage. In spite of the muscle actuator's nonlinear force-to-contraction characteristics, many motion and force control methods have been successfully applied to it. The characteristics of the actuator enable it to be used in simple positioning systems and as a variable gas spring. The actuator's almost linear pressure-to-force ratio is extremely well-suited to a variety of gripping and pressing applications. Due to the muscle actuator's characteristics and recent developments in pneumatic valve technology, there is an opportunity to share a single pressure control servo valve among multiple muscle actuators. The multiplexed control of the actuators with only one servo valve reduces the system costs significantly. In this paper we investigate the feasibility of employing multiplexed force control of four pneumatic muscle actuators. In the system, pressure is controlled by a single proportional pressure valve. High-speed switching valves are used for activating the pressure control for each muscle actuator in the desired manner. Pneumatic cylinders are attached to the other ends of the muscles in order to cause controllable position disturbances. The displacement, force and pressure of each muscle are measured with appropriate sensors. The system behavior is investigated under position disturbances.
Heat Exchangers for Aero Engine Applications
Authors: Yakinthos Kyros J. , Missirlis Dimitris K. , Palikaras Achilles C. , Goulas Apostolos K.
Published: April 2008

Nowadays, the needs for safer, cleaner and more affordable civil aero engines are of increasing importance. To cover these needs, a technology for an advanced aero engine design, which uses an alternative thermodynamic cycle, has been presented. The basis of this cycle lies in the integration of a system of heat exchangers installed in the exhaust nozzle of the aircraft engine. The heat exchangers are operating as heat recuperators, exploiting the thermal energy of the turbine exhaust gas to pre-heat the compressor outlet air before combustion and, thus, resulting in reduced pollutants and decreased fuel consumption. In this work, a procedure for the optimization of this installation is presented. The minimization of the pressure losses on the exhaust gas side is chosen as the optimization criterion of this effort. The optimization is based on experimental measurements in laboratory conditions and 2D CFD modelling for the flow inside the exhaust duct and through the heat exchangers. Detailed measurements were carried out in order to derive the pressure drop law through one heat exchanger. This pressure drop law was used in a CFD approach where the heat exchangers were modelled as porous media with prescribed pressure drop. The accuracy of this pressure drop law was validated in comparison with experimental data for a wide range of inlet conditions. A 1:1 model of the quarter of the nozzle was constructed in a wind tunnel with four full-scale heat exchangers installed in the exhaust nozzle. The measurements proved the non-uniformity of the flow field, which resulted in increased pressure losses for the heat exchangers that were operating with increased mass flow. It was possible to make improvements in the nozzle installation in order to optimize the mass flow balance through the heat exchangers and minimize the pressure losses. The optimization was based on 2D CFD modelling for the flow inside the exhaust duct and through the heat exchangers. The adopted porous media model modelled the presence of the heat exchangers inside the nozzle. The CFD modelling proved sufficient in predicting the main flow field phenomena, which were responsible for the non-uniform distribution of the mass flow and the increased pressure losses. Then, modifications in the nozzle geometry and the heat exchangers orientations were implemented in the CFD modelling. These modifications proved that with a careful approach, a better arrangement of the heat exchangers could be achieved.
Numerical Simulations of Unsteady Fluid Flow and Heat Transfer in a Transonic Turbine Stage
Authors: Mumic F. , Sunden B.
Published: April 2008

In this work, a numerical study has been performed to simulate the unsteady fluid flow and heat transfer in a transonic high-pressure turbine stage. The main objective of this study is to understand the unsteady flow field and heat transfer in a single transonic turbine stage using an unsteady structured Navier-Stokes solver. For the time accurate computation, a fully implicit time discretization, dual-time stepping, is performed. The results of the CFD simulations are compared with experimental heat transfer and aerodynamic results available for the so-called MT1 turbine stage. The predicted heat transfer and static pressure distributions show reasonable agreement with experimental data. In particular, the results show significant fluctuations in heat transfer and pressure at midspan on the rotor blade, and that the rotor has a limited influence on the heat transfer to the NGV at mid span.
Effect of Free-Stream Turbulence on Heat Transfer and Fluid Flow in a Transonic Turbine Stage
Authors: Mumic F. , Sunden B.
Published: April 2008

In the present work, a numerical study has been performed to simulate the effect of free-stream turbulence, length scale and variations in rotational speed of the rotor on heat transfer and fluid flow for a transonic high-pressure turbine stage with tip clearance. The stator and rotor rows interact via a mixing plane, which allows the stage to be computed in a steady manner. The focus is on turbine aerodynamics and heat transfer behavior at the mid-span location, and at the rotor tip and casing region. The results of the fully 3D CFD simulations are compared with experimental results available for the so-called MT1 turbine stage. The predicted heat transfer and static pressure distributions show reasonable agreement with the experimental data. In general, the local Nusselt number increases, at the same turbulence length scale, as the turbulence intensity increases, and the location of the suction side boundary layer transition moves upstream towards the blade leading edge. Comparison of the different length scales at the same turbulence intensity shows that the stagnation heat transfer was significantly increased as the length scale increased. However, the length scale evidenced no significant effects on blade tip or rotor casing heat transfer. Also, the results presented in this paper show that the rotational speed in addition to the turbulence intensity and length scale has an important contribution to the turbine blade aerodynamics and heat transfer.
The Effect of Cracks Interaction on the Critical Strain in Orthotropic Heterogeneous Material Under Compressive Static Loading
Authors: Winiarski B. , Guz I. A.
Published: April 2008

Laminar composites due to their internal structure and manufacturing methods contain a number of inter- and intra- component defects which size, dispersion and mutual interaction alter significantly the critical compression strain level. The current paper is one of the first attempts to study the crack interaction in orthotropic materials compressed in a static manner along interlaminar defects. For laminated composites compressed along layers and, therefore, along the mentioned interfacial defects, the classical Griffith - Irvin criterion of fracture or its generalization are inapplicable and all stresses intensity factors and crack opening displacements are equal to zero. This fact emphasises the importance and the necessity of the most careful investigation of fracture due to specific mechanisms inherent to heterogeneous materials. The statement of the problem is based on the most accurate approach, the model of piecewise-homogenous medium. The moment of stability loss in the microstructure of material is treated as the onset of the fracture process. The behaviour of each constituent is described by the three-dimensional equations of solid mechanics, provided certain boundary conditions are satisfied at the interfaces. The complex non-classical fracture mechanics problem is solved by finite elements analysis, using linear buckling model. Numerical analysis is aided by the advanced FE analysis software - Abaqus 6.5. The results were obtained for particular cases of real composites for the typical dispositions of cracks. It was found that both cracks length and mutual position of cracks influence the critical strain of the composite.
Evaluation of Critical Design Factors on the Thermal Behavior Due to Frictional Heat in the Oscillatory Sliding Conformal Contact
Authors: Wang P. , Hua D. Y. , Mansouri M. , Khonsari M. M.
Published: April 2008

There is a range of mechanical components in tribological systems that operate under oscillatory sliding contact. An example of interest is the so-called pin-bushing joint interface that is typically lubricated with grease. Pin-joints are often heavily loaded and the relative sliding motion at the interface between the pin (shaft) and inner surface of the bushing generates considerable amount of heat. As a result, the surface and near-surface materials can quickly deteriorate and often trigger premature catastrophic failures. Nevertheless, the severity of the temperature rise is strongly dependent upon a series of design factors including various geometric variables, materials properties, and operating conditions. In this paper, the development of a fractional factorial experimental design for evaluation of the effect of five important design factors in pin-bushing assembly is reported. The factors of special interest include the clearance ratio (C/R), aspect ratio (L/D), oscillating angle, RPM, and applied load. The performance response is the interface temperature rise. The factorial analyses presented provide quantitative information on the factors that tend to have the greatest influence on the thermal behavior of a pin-bushing assembly.
Flush-Mounted Steady-Periodic Heated Film With Application to Fluid-Flow Measurement
Authors: Cole Kevin D.
Published: April 2008

Recently unsteady heating of surface-mounted films has been applied to the measurement of fluid flow. In this paper steady-periodic heating of a surface-mounted film is studied analytically. Wall effects and axial heat conduction in the fluid are included. The temperature is found as an exact integral expression constructed from separate Green's functions formulations in the fluid flow and in the solid wall that are matched at the fluid-solid interface. Numerical results for temperature, obtained by quadrature, are reported for several flow speeds and several steady-periodic frequencies. The results show that steady-periodic heating has potential for fluid-flow measurement because the system may be tuned, via frequency, to maximize the temperature response at the fluid flow of interest. Simulated calibration curves are given.
Unique Projects for Individual Needs: Assistive Technology Designs in Engineering Education
Authors: Ault Holly K. , Hoffman Allen H. , Liadis Keith N. , Scarsella Michael J. , Toddes Steven P.
Published: April 2008

This paper describes the integration of design projects to aid persons with disabilities in the mechanical engineering program at WPI. Students ranging from first year through graduate level design and build a wide range of devices as aids to daily living, to improve mobility, or for use in recreational activities. Ongoing relationships with local agencies that serve persons with disabilities are used to solicit project topics. The range of student abilities allows us to fit the sponsor-requested projects to an appropriate class level. Students experience the full range of design activities from needs assessment through prototype construction. Students are highly motivated to work on these unique design projects that have a high impact on their clients.
Power Plant Component Design Using Creep-Damage Analysis
Authors: Kostenko Y. , Lvov G. , Gorash E. , Altenbach H. , Naumenko K.
Published: April 2008

The constitutive equation for the creep deformation rate, as well as the kinetic equations for hardening, recovery and damage processes, with a continuous functional dependence on temperature, are proposed. The material model is able to describe the primary, secondary and tertiary stages of creep behavior. The technique for the identification of parameters in the uniform model is developed on the basis of experimental creep curves for a wide range of temperatures and stresses. The parameter fitting for a creep-damage model with temperature dependence is carried out for one typical heat-resistant steel widely used in the power plant industry. Numerical results are obtained by the Finite-Element-Method for a real power plant component using the ABAQUS code and incorporated user-defined materials routines.
Computation of Acoustic Transmission Loss Through Doubly-Periodic 3D Elastic Panels
Authors: Dey Saikat , Shirron Joseph J.
Published: April 2008

We address acoustic transmission loss through doubly-periodic elastic panels separating two semi-infinite fluid half-spaces. This involves the computation of the transmitted and reflected sound fields due to an incident plane wave. The elastic panel may have complex internal structures, for example, a sandwiched honeycomb core. Our computations are based on using high order (p-version) finite element discretization. The semi-infinite fluid half-spaces on either side of the elastic panel are truncated using perfectly matched layer (PML) approximations. We verify our model using data for transmission loss for thin and thick homogeneous elastic plates using analytic solutions based on 3D elasticity as well as thin and thick plate theory. This is followed by a study of transmission loss though sandwiched honeycomb panel for a range of frequencies and incident angles.
Developing a Process to Identify Material Flow of a Priority Chemical
Authors: Ciocci Richard , Massey Daniel , Funck Steve
Published: April 2008

An Environmental Protection Agency-funded project was the material flow analysis of naphthalene-containing products in an effort to eliminate, reduce, or replace the sources of naphthalene. The project analysis began with manufacturers who use naphthalene-containing products in their processes. It identifies the basic characteristics of naphthalene as a common polynuclear aromatic hydrocarbon, which is released to the environment. Included are likely sources of naphthalene emissions and releases as they were identified for further investigation. This paper, which is the sequel to IMECE 2005-82808, highlights a secondary objective of the project: to document the approach used in identifying the naphthalene flow from the raw material to its various products. This secondary objective was to show how process, product, and quantity data can best be gathered. Within the project, there were several means to collect data, some that have worked better than others. The purpose of this objective was to provide the framework of a proven approach to generating the material flow so that it can be followed for other priority chemicals that populate the EPA list.
The Influence of Cavitation and Aeration on Gear Pumps and Motors Meshing Volumes Pressures
Authors: Borghi M. , Milani M. , Paltrinieri F. , Zardin B.
Published: April 2008

The paper describes the influence of the fluid modeling on cavitation and aeration detection in external gear pumps and motors inter-teeth volumes during the gears meshing process, in order to compare the results coming from the use of different physical models of air release/adsorption and cavitation. A simplified cavitation model is firstly involved, and pressure transients are calculated imposing a pressure cut when the fluid vapor pressure (or the dissolved air partial pressure) is reached. After, assuming an equivalent approach able to involve the vapor phase generation, the cavitation phenomena in the meshing volumes are deepened, and the influence of the fluid modeling enhancement on the cavitating machine behavior is highlighted. Then, the equivalent fluid approach is enhanced introducing the air release, and properly coupling the gaseous phases release/adsorption to the Henry's Law for not instantaneous processes. Finally, the influence of the air release/adsorption time constant on meshing volumes pressure transients are detailed, with particular attention devoted to the modification introduced by the cavitation detailing on the gaseous phase void fraction determination and on the angular extension of the cavitation phenomena detection.
Heat Transfer Enhancement of Planar Pulsating Heat Pipe Device
Authors: Cai Qingjun , Chen Chung-Lung , Asfia Julie F.
Published: April 2008

Heat pipes are widely used heat transfer devices in the electronic cooling area. In this paper, a novel pulsating heat pipe (PHP) design, which combines features of PHP and capillary microstructures, is presented to enhance heat transfer of electronic printed circuit boards (PCB). Test prototype fabrication is initiated by making dual-radius serpentine channels on a 4.0mm thick aluminum plate, followed by compressing 4.67mm diameter copper tube into the grooves, and completed by generating a millimeter sized liquid channel with micro-grooves in the PHP along the longitudinal direction. Because of this design, the planar PHP is able to circulate operating liquid by both capillary pump and oscillation motions, which eliminate the dry state in the evaporator section and supply sufficient coolant at high heat loads. Demonstrations of heat transfer performance indicate that the planar PHP has high effective thermal conductivity and low evaporator temperature fluctuations, and oscillation continuity is the key factor to reduce the temperature difference between the evaporator and condenser.
Deformation Characteristics and Constitutive Relationship of SnAgCu Lead (Pb)-Free Solder Alloys Under Thermo-Mechanical and Mechanical Loading
Authors: Hossain Mohammad M. , Viswanadham Puligandla , Agonafer Dereje , Reinikainen Tommi
Published: April 2008

In this paper is reported the mechanical and thermomechanical aspect of SnAgCu solder alloys that have been tested for their deformation behavior. Commercially available Sn3.8Ag0.7Cu was considered as base alloy. The constant stress and strain-rate tests were performed in tensile and shear configuration. Mechanical deformations were measured using bulk solder tensile specimens and grooved lap shear specimens which enabled a stress-state of nearly pure shear in the solder joint. The strain rate range was between 0.1/sec and 10-6/sec, and test temperatures were 25°C, 75°C and 125°C. Both as-prepared and thermally aged samples were tested. The aging condition was 24hrs at 125°C. The measured tensile stress-strain data were utilized to determine the constants for the visco-plastic Anand's constitutive model. Thermo-mechanical properties like coefficient of thermal expansion (CTE) for those SnAgCu lead free alloys were measured in the temperature range of - 40 to 160°C using thermo-mechanical analyzer (TMA). The tensile and shear properties of 95.5Sn3.8Ag0.7Cu solder and solder joint specimens are highly dependent on test temperature and strain rate. The mechanical strength of SAC bulk solder and solder joint decreases with increase in temperature and increases with increase in strain rate. CTE for the SAC lead-free alloys were relatively lower compared with tin-lead solder. The steady-state creep test data for 95.53.8Ag0.7Cu solder was curve-fitted to a hyperbolic-sine creep model. The material constitutive parameters developed are in line with similar studies.
Modeling of Structure and Growth Rate of Carbon Nanotubes in Flame Synthesis
Authors: Naha Sayangdev , Puri Ishwar K.
Published: April 2008

Existing literature has focused on experimental investigations of CNT/CNF flame synthesis. However, there are as yet no comprehensive models regarding their formation, growth or structure. Herein, a CNT/CNF growth rate model is proposed that is applicable for any method of CNT/CNF production (although our particular interest lies in flame synthesis in ethylene/air flames). While it is usual for most existing models to consider only a single carbon-carrying gas that contributes towards carbon deposition, our extended model can consider a complex hydrocarbon mixture that can mimic a flame environment. The model shows steady carbon deposition and filament growth occurs once there is a stable carbon cluster size due to nucleation. The concentration of hydrocarbons in the vicinity of the toroidal zone near which most of the CNT growth is observed, is negligible compared to CO concentration.
Development of a Magnetocaloric Pump Using a Mn-Zn Ferrite Ferrofluid
Authors: Gutierrez Gustavo , Catan˜o Juan , Perales-Perez Oscar
Published: April 2008

Magnetic fluids or ferrofluids are colloidal dispersions of magnetic nanoparticles in a liquid carrier. These nanoparticles have a specific size range in order to remain suspended in the liquid, about 3 to 15 nm. In this range Brownian motion (thermal molecular motion in the liquid) keeps the particles from settling out. Because magnetic particles tend to aggregate, and aggregates sediment faster than single particles, the particles are coated with a stabilizing dispersing agent. The surfactant must be matched to the carrier type and must overcome the attractive Van der Waals and magnetic forces between the particles to prevent agglomeration even when a strong magnetic field is applied to the ferrofluid. A device that can pump a fluid with no moving mechanical parts represents a very encouraging alternative since such device would be practically maintenance free. A magnetocaloric pump achieves this purpose by providing a pressure gradient to a ferrofluid placed inside a magnetic field while experiencing a temperature change. If the temperature change is produced by extracting heat out of an element that needs refrigeration, coupling this heat via a heat pipe with the magnetocaloric pump will result in a completely passive cooling system. For applications near ambient temperature the ferrofluid must have specific characteristics such as low Curie temperature, high pyromagnetic coefficient, high thermal conductivity and low viscosity. This work presents the detailed description of the synthesis of ferrofluids composed of Mn-Zn ferrite nanoparticles and the characterization of its magnetic and thermal properties. Different composition of Mn-Zn ferrites nanoparticles were produce and evaluated. This ferrite ferrofluid was compared with commercially available magnetite ferrofluid in a magnetocaloric pump prototype. Results of saturation magnetization, pyromagnetic coefficient, Curie temperature, particle size, viscosity and pressure increment inside the magnetocaloric pump are presented.
Methods for Improving the Design of Experiments Outcome in an ME Curriculum
Authors: Scott Timothy C.
Published: April 2008

To do a design of experiments project with a sufficient degree of realism can require a large block of class time. It would be valuable for the students to practice uncertainty analysis, selection of instruments, experiment planning, and application of engineering analysis. It would also be useful for them to learn about test codes and standards, to examine descriptions of similar test rigs found in the technical literature, and to operate within constraints on time, materials and fabrication costs. Time and student skill levels limit the number of these "ideals" that can be achieved, and compromises have to be made. The hope is that these limitations will not cause the project to degenerate to the "design without much analysis the night before the project is due" mentality that many students equate with "design" This paper describes methods for improving the "design of experiments" outcome in the ME curriculum. The design of a rig for testing electronics cooling heat sinks is the project. Activities in several prerequisite courses are coordinated to provide supporting background knowledge. A heat sink thermal design project in the co-requisite heat transfer course is linked to the design of experiments project. These efforts allow more time for the actual design activity. Several techniques for bringing realistic constraints into the project and for improving the efficiency of some traditionally time consuming activities are presented. Instead of simplifying the objective, students are given more assistance in overcoming the problems that they are least able to solve due to their inexperience. In this way, the project maintains a higher level of realism.
Heat Transfer Analysis of Shape Memory Alloy Actuators
Authors: Szykowny Sarah , Elahinia Mohammad H.
Published: April 2008

In recent years, shape memory alloys (SMAs) have become widely used in engineering applications due to their simplicity in use and high power density. These smart materials are characterized by their unique temperature dependent phase transformations. An accurate heat transfer model is of the utmost importance for modeling the SMA actuator dynamics. This is due to the SMA constitutive and phase kinetic behaviors being directly dependent on the heat transfer model. The research shown in this paper was conducted to investigate the adequacy of the exiting heat transfer models for SMA wire actuators. Particularly, the convection heat transfer for SMA wires with diameter of a few hundred micrometers is studied. To this end, an SMA wire actuating a dead weight was used to experimentally determine how the heat transfer coefficient varies during transformation at varying levels of applied current. These results are then compared to several existing heat transfer models. In the experiments, the temperature of the wire was measured along with the strain and stress of the SMA wire. A detailed discussion of the theoretical models and experimental findings is presented in this paper.