bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing Two Levels of Functional Detail for Mapping Historical Failures: You Are Only as Good as Your Knowledge Base
Authors: Stock Michael E. , Stone Robert B. , Tumer Irem Y.
Published: May 2008

When failure analysis and prevention, guided by historical design knowledge, are coupled with product design at its conception, shorter design cycles are possible. By decreasing the design time of a product in this manner, design costs are reduced and the product will better suit the customer’s needs. Prior work indicates that similar failure modes occur within products (or components) with similar functionality. To capitalize on this finding, a knowledge base of historical failure information linked to functionality is assembled for use by designers. One possible use for this knowledge base is within the Elemental Function-Failure Design Method (EFDM). This design methodology and failure analysis tool is implemented during conceptual design and keeps the designer congnizant of failures that are likely to occur based on the product’s functionality. EFDM offers potential improvement over current failure analysis methods, such as FMEA, FMECA, and Fault Tree Analysis, because it can be implemented hand in hand with other conceptual design steps and carried throughout a product’s design cycle. These other failure analysis methods can only truly be effective after a physical design has been completed. EFDM however is only as good as the knowledge base that it draws from, and therefore it is of utmost importance to develop a knowledge base that will be suitable for use across a wide spectrum of products. One fundamental question that arises in using EFDM is: At what level of detail should functional descriptions of components be encoded? This paper explores two approaches to populating a knowledge base with actual failure occurrence information from Bell 206 helicopters. Functional models expressed at various levels of detail are investigated to determine the necessary detail for an applicable knowledge base that can be used by designers in both new designs as well as redesigns. High level and more detailed functional descriptions are derived for each failed component based on NTSB accident reports. To best record this data, standardized functional and failure mode vocabularies are used. Two separate function-failure knowledge bases are then created and compared. Results indicate that encoding failure data using more detailed functional models allows for a more robust knowledge base. Interestingly however, when applying EFDM, high level descriptions continue to produce useful results when using the knowledge base generated from the detailed functional models.
Modeling and Control of a Construction Machine With a Human-in-the-Loop Assessment in Virtual Reality
Authors: Fales Roger C. , Kelkar Atul G. , Spencer Erik , Chipperfield Kurt , Wagner Francis
Published: May 2008

This paper presents dynamic modelling, control design, simulation results, and real time Virtual Reality (VR)-based human-in-the-loop testing for a wheel loader control system. In particular, a loader with electro-hydraulic actuation is considered. A detailed nonlinear dynamic model is developed for the hydraulic system and the loader linkage. The hydraulic model includes a load sensing pump, valves, and cylinders. The linkage model represents a two degree of freedom loader with lift and tilt functions. An LQG-based (Linear Quadratic Gaussian) robust controller is designed for automatic bucket levelling to assist the operator during the boom motion. The controller design is tested with a nonlinear model in a real-time VR simulation. In this VR simulation, the operator interacts with the model using a joystick input. The loader linkage geometry is displayed to the operator in real time using a VR display.
An Investigation of Vibration Feedthrough and Feedthrough Cancellation in Joystick Controlled Vehicles
Authors: So¨ve´nyi Szabolcs , Gillespie R. Brent
Published: May 2008

The inertial and applied forces acting on operators of joystick controlled machinery in moving vehicles can produce unintentional control signals through the joystick. These forces tend to deteriorate continuous tracking performance and further, when the machinery in control is the vehicle itself, they may lead to unstable oscillations that jeopardize that vehicle’s safe operation. In this paper, we propose the use of a force-reflecting joystick and a model-based controller to cancel the effects of inertia forces. Using a simple physical model of human biomechanics, we experimentally investigate the effectiveness of a cancellation controller in stabilizing a driving task. A second experiment involving a human subject on board a motion base investigates the ability of the cancellation controller to improve performance in a continuous tracking task. Results indicate that the cancellation controller enhances stability and improves tracking.
The Use of Spatial Statistics and Nuisance Variables in Estimating Parameters for Validating Models and Predictions
Authors: Emery A. F. , Bardot D.
Published: May 2008

Estimation of parameters for nonlinear systems is often computationally expensive and slow to converge. The procedure is aggravated when parameters, other than those sought, are not known with precision. By using Bayesian estimation, it is possible to eliminate such nuisance variables, but often at considerable cost. Using response surface approaches is effective only a) for linear systems, b) when the initial guess is close to the final values. By using concepts from spatial statistics and incorporating nuisance variables, the convergence is improved and only a reduced number of computations need be performed. Spatial statistics also provides an efficient means for predictions.
DSMC Analysis of Fluid Film Damping in Laterally Oscillating Microstructures
Authors: Park Jae Hyun , Beskok Ali
Published: May 2008

Fluid film damping in laterally oscillating microstructures is investigated in the entire Knudsen regime and a wide range of Stokes numbers by using the unsteady DSMC method. DSMC results are validated through comparisons with theoretical predictions at continuum and free molecular flow regimes. Dynamic response of the flow, including the velocity profile, normalized velocity amplitude distribution, and phase angle are presented at various flow conditions. Based on the DSMC data, quality (Q) factors are computed to quantify the damping characteristics of the system. The quality factor increases with rarefaction, proportional to the Knudsen number. The Q-factors from DSMC are compared with predictions of slip-based continuum models. Although the DSMC-based Q-factors successfuly satisfy the theoretical criterion in the free molecular flow regime, slip-based continuum models fail to predict the Q-factors in the transition and free molecular flow limits. These models also fail for high Stokes number conditions.
The Load Acting on Bearings of Rotary Compressor Sliding Vanes
Authors: Huang Yuan Mao , Li Chien Liang
Published: May 2008

This study designs extended rods with bearings for vanes and guider slots on covered plates to improve the performance of a sliding vane rotary compressor and determines the load acting on the bearings and vanes. A polytropic process with a polytropic exponent was assumed during the compression process to calculate the air pressure in the vane segments. The air pressure was used with Newton’s law to calculate loads acting on bearings and vanes. A compressor and experimental setup were also built to measure the radial load acting on the bearings. The measured load acting on the bearing was then compared with the calculated results. The exponent constant of 1.05 determined can be used for the further development of the compressor.
A New Approach on Mounting Systems Optimization
Authors: Madjlesi Reza , Khajepour Amir , Schubert Brad , Ismail Fathy
Published: May 2008

Vehicles are assemblies of subsystems or modules, which are developed in parallel at multiple locations and often for more than one vehicle. CAE software provides the integration of modules in a complete vehicle in parallel; however the whole system requires final adjustments and tunings. These adjustments, especially in suspensions and mounting systems are very time consuming and are generally based upon trial and error techniques. To reduce the number of trials, usually noise path analysis (NPA) is used. In this technique, the noise and vibration paths for each mount to the objective point are measured. Using the measured data, the dominant path is detected. A highly experienced NVH engineer now can use the information to tune the mount to satisfy the target response. This technique is appropriate if the subsystems are weakly coupled. This situation is not usually the case in engine mounting systems where any modification in one of the mounts may change the dominant path. An important step to reduce refinement time is to develop a method to obtain the overall model of the whole vehicle. In this paper, we introduce a new approach in vehicle’s NVH development. In this approach, the model of the vehicle for mounting system optimization is obtained based on the FRF synthesis. A hybrid analytical/experimental model of the vehicle is developed to predict the NVH response of the vehicle for any given mounting system. This model along with an optimization technique is used to arrive at the optimum mounting system for any objective function. The optimization method is linked with the noise path analysis (NPA), which is used to specify the dominant directions that the noise/vibration is transferred to the response point. These directions are used in the optimization procedure to find the optimum mounting system with minimum calculation time. Experimental results on a full size car are presented to evaluate new approach.
Framework for Validation of Computer Models Applied to a Resistance Spot Weld Model
Authors: Cavendish James C. , Cafeo John A.
Published: May 2008

We view the most important question in evaluation of a computer model to be: Does the computer model provide predictions that are accurate enough for the intended use of the model? The purpose of this presentation is to discuss a systematic six-step model validation process intended to help answer that question. This will be done by presenting a Bayesian statistical strategy for developing error bounds on model predictions with the interpretation that there is a specified confidence (e.g. 80%) that the corresponding true process value will lie within the range of these error bounds. Although seldom done in practice, such error bounds and confidence estimates should be provided whenever model predictions are made. A Caveat: The process of model validation is inherently a hard statistical problem. The statistical problem is so hard that one rarely sees model validation approaches that actually produce error bounds and confidence estimates on computer model predictions. The intent of this presentation is essentially to provide a ‘proof of concept’, that it is possible to provide such bounds and estimates for predictions of computer models, while taking into account all of the uncertainties present in the problem. However, the computations required in the methodology we propose can be intensive, especially when there are large numbers of model inputs, large numbers of unknown parameters, or a large amount of data (model-run or field). The test bed application we consider in this presentation (a resistance spot weld model) is relatively modest in these dimensions. Finally, we call the reader’s attention to the reference, Bayarri et. al. (2002). This reference provides a down-loadable PDF file that contains a technical report presenting all of the technical details associated with our proposed validation strategy as well as practical application of the strategy to the spot weld model described in this presentation as well as to an automobile crash model.
Requirements for Consistent and Productive Performance in High Speed Milling
Authors: Young Keith A. , Helvey Amy M.
Published: May 2008

The major performance constraint in high speed milling operations is tool chatter. This is especially true when using long slender tools. Much recent research has been done to improve the performance of milling operations through choosing tool lengths and spindle speeds such that tool chatter is avoided. This paper describes two criteria for choosing productive lengths of tools.
Low Temperature CVD SiC Coated Si Microcomponents for Reduced Scale Engines
Authors: Wijesundara M. B. J. , Walther D. C. , Stoldt C. R. , Fu K. , Gao D. , Carraro C. , Pisano A. P. , Maboudian R.
Published: May 2008

The unique operating conditions of micro-thermochemical systems introduce many materials compatibility issues that must be addressed, particularly where thin film coatings are concerned. These issues include oxidation, wear, friction, and thermal stability. This work aims to explore the effectiveness of polycrystalline 3C-SiC films deposited by low temperature chemical vapor deposition on silicon substrates as a means for the remediation of these effects. The chemical structure of the deposited films is examined by X-ray photoelectron spectroscopy and X-ray diffraction techniques. Surface physical characteristics are evaluated by atomic force microcopy as well as by scanning electron microscopy. The structural makeup of these films is characterized both optically and by the sample’s resistance to chemical etching. These barrier films are found to conformally deposit and can therefore be used to coat substrates or individual components, as well as to create highly environmentally resistant sensor elements. Samples are exposed to both a non-reactive flow high temperature source and reactive flow condition (H2–air flame) to determine their survivability. The SiC films are shown to possess a relatively high oxidation resistance when compared to Si.
Linear Stability of Two-Dimensional Stationary Waves on Evaporating or Condensing Liquid Films
Authors: Ye Xuemin , Yan Weiping
Published: May 2008

The linear spatial stability equation of the two-dimensional stationary waves of evaporating or isothermal or condensing liquid films falling down an inclined wall is established for the film thickness with the collocation method based on the boundary layer theory and complete boundary conditions. This model includes the effects of Reynolds number, thermocapillarity, inclination angle, liquid property, evaporation, isothermal or condensation. The stabilities characteristics of stationary waves are fully indicated in theory for evaporating or condensing films.
Development of Protective Coatings for Silicon Devices
Authors: Yang Quan , Chitre Kaustubh , Salami Tolulope O. , Oliver Scott R. , Cho Junghyun
Published: May 2008

Ceramic coatings can be effectively used as a surface protective layer for silicon-based devices due to their inertness and good mechanical properties. One challenge is to avoid the weaknesses that ceramic coatings inherently possess, i.e., low strain tolerance, brittleness, high temperature required to process the film, and difficulty to produce a uniform, dense layer. Therefore, in an attempt to process strain-tolerant ceramic coatings at low temperatures, we develop an aqueous solution precursor processing route. Nanometer scale organic coatings, fabricated by self-assembly processes on the silicon, are used as a ‘template’ to aid the subsequent deposition of hard ceramic coatings (ZrO2). The ceramic coatings are deposited by spin coating. The organic self-assembled monolayer (SAM) coating provides temporary strain tolerance for the overlying hard coating upon mechanical and thermomechanical stresses before being decomposed at high temperatures. Molecular level understanding of the coating microstructure and micromechanics involved in the coating processes is systematically approached via experimental tools such as AFM and nanoindenter, as well as numerical simulation.
Mechanically Driven Microtweezers
Authors: Choi Yoonsu , Ross James , DeWeerth Steve , Allen Mark G.
Published: May 2008

This paper presents a simplified method of fabricating a fundamental MEMS tool: microtweezers. The tweezers presented here require no power, but instead augment a standard microprobe station in which the axis controls allow for both controlled motion of the tweezer tips and for full three-dimensional maneuverability. This technique allows for a broad range of tweezer styles (straight and serrated tips) and sizes (microns to millimeters). The unique design also affords extraordinarily delicate control that is potentially beneficial for applications in micro-assembly, electrophysiology, and micro-dissection.
Challenging the Design Process: High Electrical Cabinet Cooling Requirements vs. Stringent Airborne Noise Requirements
Authors: Cushman Erick B. , Gwin Bob , Shipman Reed
Published: May 2008

An operationally critical, manned control station’s design was challenged to meet stringent airborne noise requirements. Through an innovative, interdisciplinary engineering approach, a solution was implemented, resulting in the first production unit meeting airborne noise requirements. The manned control station was initially designed with nine tubeaxial fans continuously operating at maximum rated speed to provide sufficient cooling to internal components at the station’s worst-case maximum ambient operating temperature of 122°F. Initial testing of a prototype unit showed airborne noise requirements were exceeded by as much as 22 dB (re 20 micro-Pascals). Fan speed reduction and installation of temporary internal acoustic absorption material were tested to measure effectiveness, but were not sufficient to meet airborne noise requirements. The normal operating condition of the control station was reviewed and detailed modeling and testing of the station’s actual cooling requirements under various operating scenarios was conducted. During this process, it was recognized that under normal operating conditions, the worst-case ambient operating temperatures were improbable and that a balancing of cooling requirements and acoustic requirements was possible. A new cost-effective method of fan control in conjuction with the installation of permanent internal absorption material and a redesign of ventilation ducting was implemented. In normal ambient temperature conditions, six of the nine internal fans operate at minimum rated speed. If ambient temperatures rise above normal (the control station’s airborne noise requirments only apply at normal “non-casualty” ambient temperatures), three additional exhaust fans automatically turn on at minimum rated speed to minimize additional airborne noise contributions. If ambient temperatures continue to rise, all nine fans are automatically switched on at maximum rated speed to protect the internal components of the operationally critical control station. Acoustic performance evaluations predicted these improvements would result in meeting the stringent airborne noise requirements. These predictions were validated during testing of the first production unit, which passed all airborne noise requirements.
Fluid Flow and Weld Pool Dynamics in Dual-Beam Laser Keyhole Welding
Authors: Hu J. , Tsai H. L.
Published: May 2008

The use of dual or multiple laser beams is necessary for welding thick-section metals, especially for Nd:Yag lasers which are limited to relatively low power as compared to CO2 lasers. It was also reported that the use of dual laser beams for welding can increase keyhole stability leading to a better weld quality. So far, the development of dual-beam laser welding technologies has been in the experimental stage. The objective of this paper is to develop mathematical models and the associated numerical techniques to calculate the transient heat transfer and fluid flow in the weld pool and to study weld pool dynamics during the dual-beam laser welding process. The simulation was conducted for a three-dimensional stationary dual-beam laser welding. A very interesting change of the top-surface view of the weld pool was predicted. During the welding process, the top-view shape of the weld pool changes, starting from an oval-shape with the long-axis connecting the centers of the two laser beams, to a circle, and finally to an oval-shape with the short-axis connecting the centers of the two laser beams. Although a direct comparison with published experimental observation is impossible (due to the lack of detailed experimental data), the predicted weld pool shape is similar to that observed from experiments. The dynamical change of the weld pool shape can be well explained by the predicted fluid flow field.
Non-Contact Virtual Instrument Measurement System for Analyzing the Liquid Droplet Shrinkage Parameters
Authors: Ramasamy Suresh K. , Shetty Devdas
Published: May 2008

Recent trend in assembly techniques in automotive industry has shown that adhesive bonding is gaining new applications. The main problem faced with the usage of adhesives is the need to understand the effects of adhesive bonding on the dimensional tolerances. Adhesive shrinkage depends on various parameters like base metal’s surface roughness, reflectivity, curing intensity etc., to name a few. In order to allocate the shrinkage allowance, we need to establish the parameters affecting the shrinkage. For this, we need to design a set of experiments and design a measurement system for calculating the adhesive shrinkage. This paper discusses the development of typical real time measurement system used for volumetric shrinkage measurement. The system is integrated with specialized laser, rotary mechanism, imaging system, data acquisition and virtual instrument. The paper details a systematic methodology that can be easily duplicated, the initial design stages planned and executed, and the repeatability and reproducibility test results done on the initial system. The test data is stored in spreadsheet format along with other parameters under consideration like the base plate’s surface roughness, reflectivity, and curing intensity. Based on the initial study, the root cause analysis will be done and further tests will be conducted on the new system utilizing the taguchi method. The tests would help us find the parameters controlling the shrinkage and also their interdependence factors.
The Design and Analysis of Piezoelectrically Actuated Microfluidic Systems
Authors: Chiarot Paul , Sullivan Pierre , Mrad Ridha Ben
Published: May 2008

Microfluidics requires a fundamental understanding of flow characteristics on the microscale. This work combines the design and characterization of passive microfluidic components. The goal is to improve the design and reliability of these devices and to develop and confirm design tools for microfluidic systems. To predict operating performance, models are developed for various components including two designs of a passive conduit valve and a passive mixing chamber. These are examined at different geometric scales and conditions using Finite Element Analysis (FEA) to determine the dimensional effect on the available flow rates, secondary flows, and driving pressures. FEA predicts the characteristics of the microfluidic devices including diodicity and achievable flow rates.
Free Vibrations of a Branched Structure as Applied to the Respiratory System
Authors: Au P. M. , Al-Jumaily A. M.
Published: May 2008

The vibration characteristics of a branched thin circular cylindrical shell structure, which resembles the respiratory system tree, are determined using membrane shell theory. Since there is no previous published data in this regard, the finite element method is used to justify the analytical results. The human airways are of a simple tree pattern but complex in physical structure. However, they should behave just like most mechanical parts that have their own natural frequencies in response to external excitation. Investigations are performed from the trachea down to the sixteenth generation. There is a good agreement between the two approaches, which set good foundations for future research.
Wave Propagation in Micromorphic Ferroelectric Solids
Authors: Lee James D. , Chen Youping , Eskandarian Azim
Published: May 2008

The balance laws of mass, microinertia, linear momentum, moment of momentum, energy, and entropy for microcontinuum are integrated with the Maxwell’s equations. The general constitutive theory for micromorphic electromagnetic thermoelastic solid is constructed. Linear constitutive equations of specialized micromorphic theory for ferroelectric solids with axis symmetry are derived. The frequency-wave-vector relations of wave propagating in perovskites parallel and perpendicular to its c-axis are obtained.
Application of the Measured Slope Distribution to the Prediction of the Bidirectional Reflectance for Rough Surfaces
Authors: Zhu Q. Z. , Zhang Z. M.
Published: May 2008

Surface topography of the rough side of a silicon wafer is characterized using an atomic force microscope (AFM). The slope distribution calculated from the measured surface profiles deviates significantly from the Gaussian distribution. The experimentally obtained slope distribution is incorporated into a geometric-optics model to predict the bidirectional reflectance distribution function (BRDF) of the rough surface. Comparison has been made between the predicted BRDF and that measured with a recently built bidirectional scatterometer, at 635 nm and 785 nm for different incoming angles. The trends agree well between the predicted and measured BRDFs, especially for the parallel-polarized incidence (p-polarization), although relatively large discrepancies exist near the specular peak and at large reflection angles. This work offers a plausible explanation of the second non-specular peak in the observed BRDF as associated with the subsidiary maximum in the slope distribution. Anisotropic features have been found both in the calculated slope distributions and the measured BRDFs.
Numerical Simulations of Heat and Fluid Flow in Grooved Channels With Curved Vanes
Authors: McGarry Matthew , Campo Antonio , Hitt Darren L.
Published: May 2008

The use of vanes in grooved channels for heat transfer enhancement has received more attention in the recent years due to applications in heat exchangers and electronics cooling. The current work focuses on characterizing the vortex formation around heated elements in grooved channels with curved vanes. A computational model is developed to examine the effect that the vortices have on heat transfer and system performance for a range of Reynolds numbers of 100 to 800. These vortices explain the previously observed characteristics in system performance for geometries with the use of curved vanes. At a Reynolds number of 400 these vortices inhibit heat transfer and increase pressure drop in the channel, resulting in significant decreases in system performance.
Generalized Equation for Thermal Conductivity of MLI at Temperatures From 20K to 300K
Authors: Gu Lixing
Published: May 2008

Multilayer insulation (MLI) has the lowest thermal conductivity of any currently used insulation in high vacuum environments and is used in cryogenic insulation system to minimize heat leaks in liquid hydrogen storage tanks. MLI consists of highly reflective radiation shields separated by spacers or insulation. The thermal conductivity of MLI varies with both temperature and vacuum level. Most published apparent thermal conductivities were measured for temperatures between 80K and 300K; some of the published data were for temperatures between 20K and 80K. Since the temperature of liquid hydrogen is 20K and the storage tanks are exposed to ambient air, it is essential to know the thermal performance of MLI for the temperature range of 20K to 300K. In addition, in order to provide a detailed temperature distribution and to optimize insulation systems with respect to the number of layers of MLI, layer density, insulation weight, and separator configuration, the layer-by-layer thermal performance of MLI has to be established for efficient storage tank design. A general equation for thermal conductivity was developed based on heat transfer principles for a wide range of temperature differences and vacuum levels. The equation consists of four heat transfer modes: 1) thermal radiation between two adjacent reflectors, 2) thermal radiation absorbed by spacers 3) gas conduction, and 4) solid spacer conduction. The equation can be applied for the temperature ranges of liquid hydrogen up to ambient, and for pressure ranges between 1.33 mPa to 1.33 kPa (0.01 millitorr and 10 torr). The predicted layer-by-layer temperatures, heat fluxes and apparent thermal conductivities using the developed thermal conductivity equation show very good agreement with measured data between the temperatures of 80K and 300K at the various pressure levels. When the equation was applied for a temperature of 20K, heat fluxes increased due to the larger temperature difference, while apparent thermal conductivities decreased due to the lower cold side temperature.
Test Methodology for Impact Testing of Portable Electronic Products
Authors: Varghese J. , Dasgupta A.
Published: May 2008

This paper introduces a test methodology to examine the durability of surface mount interconnects under impact loading when a portable electronic product is dropped. Conventional testing approaches that consider loading (total impact energy, orientation and number of impacts) as the governing criterion for failure, typically report difficulties in correlating with impact durability under field conditions. This study considers damage accumulated in the interconnects in terms of local flexural strain, strain rate and acceleration. The advantage is that the results are less dependant on structure and loading, because damage is quantified in terms of specimen response rather than the loading. An instrumented, repeatable impact test setup is developed. The test matrix covers the design space in terms of specimen styles, impact orientation, loading and boundary conditions. The entire test matrix is replicated twice for proof of consistency of the test data. A finite element model of the transient impact is developed. Results indicate that number of impacts to failure is a good damage metric for constrained impacts. The same damage metric may not be applicable for unconstrained (free) impacts because the strain signatures are more complex. A comparative analysis of the experimental and numerical data indicates a good correlation between the two. The end goal is to develop a consistent, accurate and generic methodology for ranking the impact durability of different surface mount interconnects technologies.
Evaporation of Methanol/Water Mixtures in Microchannels
Authors: Haendler Brenda E. , Sun Chen-Li , Pettigrew Kenneth I. , Walther David C. , Pisano Albert P.
Published: May 2008

This paper presents research on the evaporation of methanol/water mixtures in uniformly heated, constant cross-section silicon serpentine microchannels. The phase change of a variety of mixtures of methanol and water was observed, characterized and compared to the phase change both of pure water and pure methanol. Seven fluids were tested: pure water, pure methanol and five different molar fractions of methanol mixed with water. Flow rates were varied from Reynolds number five to ten. In the microscale system, it is shown that the flow boiling characteristics of the methanol/water mixtures are markedly different from those of pure liquids. Specifically, for the binary system there is a lack of a clear meniscus that spans the microchannel, which is seen in the pure fluid systems. Rather, the phase change of binary mixtures appears to occur over a much greater length of microchannel than for pure fluids. Unstable, intermittent evaporation fronts were also observed within the channels for moderate levels of superheat that are most likely dictated by the local temperature and pressure variations along the channel. Furthermore, at no time was bubble formation observed, despite the fact that several of the mixtures were subject to superheats as great as 20°C.
Leakage Flow Analysis for a MEMS Rotary Engine
Authors: Heppner Joshua D. , Walther David C. , Pisano Albert P.
Published: May 2008

An internal leakage flow analysis is presented for a MEMS fabricated rotary engine in order to establish design parameters for micro engine sealing systems. This research is part of the MEMS Rotary Engine Power System (REPS) group effort to develop a portable power system based on an integrated generator and Wankel rotary internal combustion engine. In order to have acceptable system efficiency, it is necessary to suppress internal leakage and thereby maintain a critical level of compression ratio. There are two inherent leakage paths in rotary engines, which result in blowby and reduced compression ratio: leakage around the apexes of the rotor and leakage across the rotor faces. These sealing issues arise due to the large pressure gradients, which occur along these leakage paths in the combustion chamber. It is the aim of this work to examine the effects of reduced scale on both traditional and novel rotary engine apex sealing mechanisms. In contrast to the macro scale, viscous forces have an increased importance in micro scale engines since Re~.01. A simplified Poiseuille-Couette flow model has been developed to analyze the leakage flows of rotary type engines. Since the Reynolds number for the MEMS REPS is extremely small, the model assumes that the flow is laminar, viscous, incompressible, and steady with air as the working fluid. The model indicates that if a 1 μm gap can be maintained between the housing and moving parts (rotor apexes and faces), leakage flows at expected engine operation speeds will only reduce the compression ratio from 8.3:1 to 6.1:1 so long as the rotation speed is greater than 10,000 rpm. It is doubtful that a traditional or simple micromachine design will yield such a gap and therefore several novel, integrated sealing approaches are under investigation. The model will determine design specification for one of these approaches, an integrated cantilever flexure apex. In conjunction with the theoretical model, a scaled engine experiment at the macro scale is used to verify the modeling effort. The scaling of the experiment complies with Reynolds scaling and ensures that Hele-Shaw flow within the leakage paths is maintained. The experiment does not operate as a functional engine, rather the experiment is designed to maintain a precise clearance between the rotor and housing. In order to preclude additional pressure driven flow effects, an electric motor is used to spin the rotor and simulate the rotation expected due to the combustion pressure acting on the rotor face.
Why Is (111) Silicon a Better Mechanical Material for MEMS: Torsion Case
Authors: Kwak Donghun , Kim Jongpal , Park Sangjun , Ko Hyoungho , Cho Dong-Il
Published: May 2008

This paper shows that using the Finite Element Method (FEM), the torsional stiffness of silicon varies by the least amount on silicon (111) with respect to crystallographic directions, when compared to silicon (100) and (110). The used simulator is ANSYS 5.7 with the element type of Solid 64. As a simulation model, we use a simple torsion system, in which a rotational inertia is attached to the center of clamped-clamped beam with a rectangular cross-section. From the results of the modal analysis, the torsional stiffness is derived using the formula between the natural frequency and the torsional stiffness. Simulation results show that the maximum variations of the torsional stiffness on silicon (111), (100) and (110) are 2.3%, 26.5%, and 31.2%, respectively. This implies that on <100> and <110> silicon wafers, substantially different physical dimensions are necessary for devices with the same torsional characteristics, but with different orientations. Therefore, <111> silicon wafers represent a more suitable substrate to design and fabricate torsional micro and nano systems.
Analysis of Experimental Shock and Impact Response Data of a Printed Wire Board
Authors: Heaslip Greg M. , Punch Jeff M.
Published: May 2008

There is considerable reported evidence that a large percentage of portable electronics product failure is due to impact or shock during use. Failures of the external housing, internal electronic components, package-to-board interconnects, and liquid crystal display panels may occur as the result of dropping. For many orientations of drop, the Printed Wire Board (PWB) will flex significantly during the impact event and subsequent clattering. Reducing the curvature and acceleration of the PWB during impact is an integral part of the design strategy for such products. This paper investigates the response of a PWB subjected to drop and shock tests through a combination of an analytical model, explicit dynamic Finite Element Analysis (FEA), and experimentation. A test vehicle consisting of a double-sided copper clad laminate PWB, mounted as a double cantilever, is used as a basis for the investigation. A free fall drop-test system is used to represent the drop scenario, and a vibration/shock system is used to impart shocks to the test vehicle. Measurements from strain gages and accelerometers are recorded using a high-speed data acquisition system. Results from experimentation show the strain/time series data from which maximum strain, natural frequencies, and damping coefficient are extracted. These measurements are compared with theoretical calculations and FEA output for the various shock and impact profiles. The investigation illustrates the response of a PWB to various shock and impact scenarios through theory, numerical simulation, and experimentation. Wavelet techniques are used to analyse the time series data, and from the resultant time/frequency space, component frequencies are extracted. It is shown that wavelet techniques are a useful tool in the analysis of shock and impact response data.
Experimental Comparison of Thermal Control Strategies in Piping Networks
Authors: Franco Walfre , Sen Mihir , Yang K. T. , McClain Rodney L.
Published: May 2008

This manuscript presents an experimental study of three thermal control strategies commonly used in heating and cooling of buildings. The strategies are defined by the variables to be controlled, the hardware used for control and the piping arrangement. The experimental facility includes three heat exchangers within secondary loops that are connected to a primary loop. A different control technique is applied to each secondary loop. A heat exchanger on the primary loop delivers cooling water to the secondaries and receives warm water in return. Chilled water is provided by the building services. The thermal load to the heat exchangers is supplied by two water heaters which are located on a closed heating circuit. PID controllers are used to respond to changes in the thermal load. The temperature difference at the primary loop heat exchanger is used as a criterion for comparison to assess the relative merits and drawbacks of each strategy.
MEMS Microvalve for Harsh Environment
Authors: Seeley Charles , Fortin Jeff , Wetzel Todd , Sealing Scott , Fosen Keith
Published: May 2008

There is a need for small valves which control flow at high temperature and pressure for a number of commercial and military applications. However, traditional solenoid actuated valves are typically expensive, heavy and subject to undesirable electrical and mechanical failure modes. Micromachining techniques, commonly used in the electronics industry, are finding more and more applications for Micro Electro Mechanical Systems (MEMS). Most of the previous work in the area of MEMS valves has been limited to low pressure/low temperature flows at ambient conditions. In this presentation, the development and testing of a two stage MEMS diaphragm valve that is capable of operating at high temperature and pressure gas flows is presented. Valve requirements, tolerances and thermal management are considered in the design. Valve fabrication processes, such as Reactive Ion Etching (RIE) and laser ablation, are discussed in detail. Issues related to the actuation of the microvalve are also discussed, including two approaches based on shape memory alloy and piezoelectric materials. Modeling and test results are presented throughout to identify successes and lessons learned.
Design and Tuning of Distributed Importance-Based Fuzzy Logic Controller for Two-Link Rigid-Flexible Manipulator
Authors: Shi Linda Z. , Trabia Mohamed B.
Published: May 2008

Fuzzy logic control has been widely used in many industrial processes due to its computationally efficient and robust characteristics. In many applications, verbalization of expert-knowledge can be easily used to design a fuzzy logic controller (FLC). On the other hand, other applications with many variables and complex mathematical model offer challenges to fuzzy logic control. Multi-link flexible manipulators belong to this category. An earlier work, [1], presented a distributed importance-based FLC for a single-link flexible manipulator. This paper extends this idea to a two-link rigid-flexible manipulator that moves in a vertical plane where the gravity field is active. The structure of the proposed controller is based on evaluating the importance degrees of the variables of the system, over its range of operation, to consider the coupling effects between the rigid and the flexible links. Variables with higher importance degrees are grouped together while variables with lesser importance degrees may be deleted to simplify the design of the controller. After determining the importance degrees of the variables, a distributed controller composed of four two-input one-output FLC’s is created. Unlike the single-link flexible manipulator, the fuzzy rules of the distributed FLC for the two-link rigid-flexible manipulator cannot be written by an expert based on intuition and observation of the inertial system due to the complexity of the manipulator and the coupling effect of its variables. To solve this problem, an importance-based linear controller that has the same input-output structure as that of distributed importance-based FLC is constructed to help write the fuzzy rules of the distributed FLC. Fuzzy rules of the distributed FLC are then selected to mimic the performance of the corresponding linear controllers. To compare the performance of the distributed importance-based FLC with that of importance-based linear controller, these two controllers are tuned using nonlinear programming by varying the gains of the importance-based linear controller and the parameters of membership functions of the variables in the distributed importance-based FLC. Robustness of each of the controllers after tuning is tested by varying the payload of the manipulator. The two importance-based controllers are simulated and compared.
Design and Optimization of an Aluminum Nitride Sublimation Growth System
Authors: Wu Bei , Ma Ronghui , Zhang Hui
Published: May 2008

In this paper, an integrated model considering induction heating, heat transfer, growth kinetics and thermo-elastic stress has been developed to study temperature distribution in the growth system, crystal shape and stress distribution in the asgrown aluminum nitride (AIN) crystal. The electromagnetic field and induction heat generation are calculated by the Maxwell equations. Transient temperature distribution in the growth chamber is simulated by energy accounting for conduction/radiation within and between various components. To reduce thermal stress and dislocation, a growth method to enlarge the ingot diameter from a smaller seed and maintain low thermal stress in the crystal has been proposed. The thermo-elastic stress fields have been calculated for several designed temperature profiles along the crucible inner wall and stress distribution has been correlated to dislocation density distribution.
Thermal Analysis and Buckling Behavior of Continuous Silicon Wafer Manufacturing by EFG Method
Authors: Sun D. , Wang C. , Zhang H.
Published: May 2008

A comprehensive two-dimensional numerical model, which accounts for heat/mass transfer, solidification, and electromagnetic field, has been developed to simulate the silicon tube growth by the edge-defined film-fed (EFG) method. A multi-block grid system has been employed to yield a high accuracy in the vicinity of die tip with relatively low CPU time. Selected results of magnetic and temperature fields have been presented for the silicon tube growth system of 30cm in diameter and 0.3mm in thickness. Based on elastic assumption, the mechanism of buckling behavior of the as-grown tube has been analyzed.
Discontinuous Galerkin Method for Internal Thermal Radiation Problems
Authors: Cui X. , Li B. Q.
Published: May 2008

The internal thermal radiation phenomena are described by a first-order integral-differential equation, which poses an intrinsic problem for the popular diffusion-based Galerkin finite element method. By allowing for discontinuity across the internal inter-element boundaries, the finite element procedure can be adapted to solve the integral-differential equation. This paper discusses a numerical procedure based on the discontinuous Galerkin method for the solution of radiation heat transfer involving participating media. Detailed formulation using the discontinuous Galerkin method for internal radiation heat transfer calculations is given. The coupling of the method with the conventional finite element method for mixed heat transfer calculations is also presented.
Novel Vehicle Stability Control Using Steer-by-Wire and Independent Four Wheel Torque Distribution
Authors: Kueperkoch Stefan , Ahmed Jasim , Kojic´ Aleksandar , Hathout Jean-Pierre
Published: May 2008

The introduction of X-By-Wire technology opens new possibilities for vehicle stability control. This technology replaces the mechanical links currently existing between the driver and different actuators with electrical connections so that the driver can be decoupled from the control system. In this paper, we consider a X-By-Wire vehicle powered by four independent wheel motors and front wheel steer-by-wire. For such a vehicle, a control algorithm is developed that employs steering and individual wheel acceleration in addition to braking to enhance stability and improve performance. Such a vehicle offers advantages in case of actuator failure where the remaining actuators can act to ensure stability and we illustrate this in simulation using our control algorithm. Finally, we describe our experimental setup and present preliminary experimental results.
Design of Cooling Systems for Electronic Equipment Using Both Experimental and Numerical Inputs
Authors: Icoz Tunc , Jaluria Yogesh
Published: May 2008

This paper presents a methodology for the design and optimization of the cooling system for electronic equipment. In this approach, inputs from both experimentation and numerical modeling are to be used concurrently to obtain an acceptable or optimal design. The experimental conditions considered are driven by the numerical simulation, and vice versa. Thus, the two approaches are employed in conjunction, rather than separately, as is the case in traditional design methods. Numerical simulation is used to consider different geometries, materials and dimensions, whereas experiments are used for obtaining results for different flow rates and heat inputs, since these can often be varied more easily in experiments than in simulations. Also, transitional and turbulent flows are more accurately and more conveniently investigated experimentally. Thus, by using both the approaches concurrently, the entire design domain is covered, leading to a rapid, convergent, and realistic design process. Two simple configurations of electronic cooling systems are used to demonstrate this approach.