bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigations on Impregnation Effects on a Non-Crimp Fiber Bed
Authors: Repsch M. , Huber U. , Rief S. , Kehrwald D. , Steiner K.
Published: April 2008

Permeability and viscosity are the key input parameters for performing LCM (Liquid Composite Molding). Currently the measurement expenses for the determination of permeability are very high. In order to reduce these expenses and to predict the permeability value in a more theoretical manner the interaction between fiber bed and impregnating fluid has to be clarified. This paper presents an overview about experimental and evaluation techniques in order to identify interaction of fluid and dry fiber structure driven impregnation. Flow experiments are executed using an epoxy resin and a non-crimp fiber bed. Attention is paid to the global flow behavior as well as to the impregnation effects on a mesoscopic level. Additionally the viscosity characteristic of the resin used is investigated. Finally basic micro structural simulations are performed and verified by the evaluation of the flow experiments.
Accuracy Analysis of Machining Process Using a Spindle Probe and a CMM to Reduce the Scrap
Authors: Kwon Yongjin
Published: April 2008

In-process part inspection using a spindle touch probe has gained a significant importance, mainly because parts can remain on the machine without disrupting the machine setup while inspection is being conducted. This practice leads to a shorter inspection time, improved part accuracies, and reduction of scraps. Recently, intense domestic and international competition has put more importance on part quality in terms of producing parts right the first time and maintaining the consistent quality standards. A literature review revealed that a comparative analysis between in-process gauging using a touch probe and post-process inspection using a coordinate measuring machine (CMM) to ascertain part quality has not been adequately studied. Therefore, there is a need for a study to measure the characteristics of the two inspection techniques. To address the problem, cutting experiments were conducted and measurement data were analyzed using a state-of-the-art CNC machine, a CMM, a touch probe, and a high-precision ballbar system. The experimental data show that machined features and touch probe measurements are affected by the inherent shortcomings in machine tool structure, suggesting a machine tool capability analysis be undertaken in tune with the required tolerance specifications prior to machining operations, rather than solely relying on the touch probe inspection for part quality assessment.
Chemical Non-Equilibrium Model for Simulation of Combustion and Flow in Propulsion and Power Generation Systems
Authors: Naumov V. I. , Kriukov V. G. , Abdullin A. L. , Demin A. V. , Iskhakova R. L.
Published: April 2008

Novel methodology of the simulation of combustion and flow in propulsion and power generation systems is developed. The basic concept of the methodology and model is division of the working volume into reactors on the ground of equations of motion or semi-empirical models of fluid flow. Each reactor is interpreted as a time-dependent volume with uniform non-stationary parameters. Mass- and heat-transfer between neighbor reactors are simulated. Time variation of chemical composition of working medium is described by equations of chemical kinetics derived in exponential form. Depending on the specific conditions mathematical model of each reactor could include additional “submodels” and corresponding equations of accompanying processes which describe variation of temperature, pressure, mass, enthalpy, etc. Reactor’s approach is realized in invariant computer code NERCHIM. Models of combustion and flow in propulsion systems, developed on the basis of reactor’s approach and NERCHIM software are presented.
Chaotic Mixing of Highly Viscous Liquids With Rectangular or Elliptical Rotors
Authors: Ulucakli M. Erol
Published: April 2008

The objective of this research is to experimentally investigate various mixing regions in a two-dimensional Stokes flow driven by a rectangular or elliptical rotor. Flow occurs in a rectangular cell filled with a very viscous fluid. The Reynolds number based on rotor size is in the order of 0.5. The flow is time-periodic and can be analyzed, both theoretically and experimentally, by considering the Poincare map that maps the position of a fluid particle to its position one period later. The mixing regions of the flow are determined, theoretically, by the fixed points of this map, either hyperbolic or degenerate, and their stable and unstable manifolds. Experimentally, the mixing regions are visualized by releasing a blob of a passive dye at one of these fixed points: as the flow evolves, the blob stretches to form a streak line that lies on the unstable manifold of the fixed point.
Incremental Forming for Aluminum Automotive Technology
Authors: Golovashchenko Sergey F. , Krause Al , Gillard Alan J.
Published: April 2008

Insufficient formability can be a major issue in the manufacturing of complex parts, particularly in aluminum alloys that have less formability when compared to steel. The approach which is the subject of this work is to determine the technical feasibility of partial forming, followed by a fast heat treatment and then further deformation. Alloys for consideration would include both 5xxx and 6xxx alloys typically used on interior and exterior automotive panels. The heat treatment regimes used for 6xxx alloys did not affect the material structure, which was confirmed by microstructural analysis and comparison of mechanical properties before and after the heat treatment. Experiments on 5xxx alloys indicated relative improvement of 300% or more. Regimes of material deformation and heat treatment will be presented.
Design of the SAFER Emergency Gate Using LS-DYNA
Authors: Bielenberg Robert W. , Rohde John D. , Reid John D.
Published: April 2008

In recent years, NASCAR and the Indy Racing League have improved the safety of their racetracks through the installation of the Steel And Foam Energy Reduction barrier (SAFER). The new barrier consists of a high-strength, tubular steel skin that distributes the impact load to energy-absorbing foam cartridges in order to reduce the severity of the impact, extends the impact event, and provides the occupant of the race car additional protection. During installation of the SAFER barrier, the designers realized that certain race tracks were designed with the emergency track exit in the outside of the corner. Because the SAFER barrier needed to be installed in these corners, a gate mechanism had to be designed for the barrier that would provide access to the track while retaining the safety performance of the system. Full-scale crash testing of the first SAFER gate design showed that the gate did not posses sufficient capacity to handle the loads experienced during a worst-case impact scenario. Non-linear finite element analysis was then used to redesign the gate mechanism. The original gate design was simulated using LS-DYNA in order to validate the computational model. Modifications to increase the capacity of the gate mechanism were designed and analyzed until suitable results were obtained through simulation. Finally, the redesigned SAFER gate was successfully full-scale crash tested.
A Sacrificial Method for Fabricating Microchannel Accelerated by Galvanic Corrosion
Authors: Zeng Hongjun , Feinerman Alan , Wan Zhiliang
Published: April 2008

A metal sacrificial method has been investigated for creation of microchannels by galvanic corrosion in a metal multilayer. To achieve the fastest sacrificial metal combination, different metals and the corresponding etchants are chosen. Channels from 50 μm to 1 μm wide, 0.2 μm high, and 1500 μm long, as well as the channel array is fabricated, using Cr/Cu galvanic metal couple as sacrificial material. The relationship between the etching front vs. the etching time, and the relationship of the etch rate vs. channel width is measured and compared with the etching performance of the single metal. The measurement shows there is approximately 10 times faster etching in the galvanic coupled metals than that in the single metal. SEM images of the channels and channel array made by this method are presented. This method is compatible with the conventional VLSI process, and has the potential for fabricating microchannels with submicron or even nanometer cross section.
Sensors for Measuring Forces and Moments With Application to Ground Vehicles Design and Engineering
Authors: Gobbi M. , Mastinu G. , Giorgetta F.
Published: April 2008

The paper presents a new family of sensors that can be produced at a relatively low cost and that can measure the 3 forces and 3 moments acting at a point of a structure. The final aim of the research work is to develop measuring hubs and general purpose 6-axis load cells able to enhance the active safety of vehicles by providing information on forces and moments acting at the tyre/suspension system or on different vehicle subsystems, in the low frequency range (up to 100 Hz). Measuring hubs and general purpose 6-axis sensors have been manufactured and tested. The paper presents the concept, the construction issues and the performances of such devices. All of the presented measuring devices are based on a special statically determined structure. Twelve strain gauges measure the deformations at special locations and six signals (linearly related to the forces and moments) are filtered, amplified and digitally converted before they are stored or transmitted to a remote receiver. The sensitivity and the accuracy of such measuring devices are sufficient to exploit them to enhance the active safety of road vehicles.
Transient Temperature Measurement in Nanosecond Pulsed Laser Micro Drilling by Using Micro Thin Film Thermocouples
Authors: Choi Hongseok , Li Xiaochun
Published: April 2008

It is of fundamental interest to investigate the complicated and transient thermal phenomena near the nanosecond pulsed laser-material interaction region. While numerous analytic and numerical models have been developed, little experimental results are available for a solid understanding of transient thermal phenomena in nanosecond pulsed laser micro drilling. In this paper, micro thin film thermocouples were fabricated on electroplated nickel substrates to study the transient temperature variations during laser micro drilling. Transient temperatures were successfully measured with superior temporal and spatial resolutions for the fundamental study of the nanosecond pulsed laser micro drilling. The in-situ measured data can be used to improve existing analytical and numerical models.
Condition Monitoring of PEM Fuel Cell Using Hotelling T2 Control Limit
Authors: Xue X. , Tang J.
Published: April 2008

Although a variety of design and control strategies have been proposed to improve the performance of polymer electrolyte membrane (PEM) fuel cell systems, temporary faults in such systems still might occur under practical operating conditions due to the complexity of the physical process and the functional limitations of some components. If these faults cannot be detected in a timely manner, long-time malfunction of fuel cell components may lead to catastrophic failures. Clearly, it is necessary to study the appropriate state condition monitoring scheme for fuel cell systems. In this research, we first develop a fuel cell stack model which can simulate the complicated transient behavior and dynamic interactions of the temperature, gas flow, phase change in the anode and cathode channels, and membrane humidification under operating conditions. Using this model as basis, we then employ the Hotelling T2 control limit approach to monitor stack conditions by using real-time measurements of fuel cell state variables such as output voltage. An important feature of the Hotelling method, a multivariate statistical analysis approach, is that one may decide fault occurrence under measurement noise. Simulation indicates that the new method has very high detection sensitivity and can detect the fault conditions at the early stage. This proposed monitoring strategy could provide valuable information for low-level real time control as well as high-level decision making.
Model Reference Adaptive Control of SUT Building Energy Management System
Authors: Fardadi M. , Selk Ghafari A. , Hannani S. K.
Published: April 2008

Model Reference Adaptive Controller (MRAC) design, for Sharif University of Technology (SUT) Building Energy Management System (BEMS) is addressed in this paper. A reference model with fuzzy adaptive control rules was employed to design the controller for a system with time delay and model parameter uncertainties. Simulation study shows good performance of the closed loop system with optimum energy consumption for this system under external load disturbance.
Stabilization of a Steer-by-Wire Vehicle at the Limits of Handling Using Feedback Linearization
Authors: Hsu Yung-Hsiang (Judy) , Gerdes J. Christian
Published: April 2008

As a vehicle approaches the limits of handling (the operating region defined by the peak lateral tire force), the vehicle response may be oscillatory or unstable. This paper develops a control system to allow the driver to approach the limits of handling safely. The control algorithm uses a new method that applies recent advances in vehicle sensing to estimate tire cornering stiffness and coefficient of friction in real-time. The controller employs state feedback linearization to cancel nonlinearities in the system using steer-by-wire steering inputs. Once the lateral force surpasses a threshold value, the driver steering input is saturated to keep the vehicle in the linearizable handling region and to alert the driver of approaching limits. Simulation results and preliminary experimental work performed on a steer-by-wire research vehicle demonstrate the potential benefits of this control system.
Improved Nanopositioning Resolution Through Piezoresistive Feedback Control of a MEMS Thermal Actuator
Authors: Messenger Robert K. , McLain Timothy W. , Howell Larry L.
Published: April 2008

Utilizing the piezoresistive properties of polysilicon as an on-chip sensing mechanism facilitates the implementation of feedback control on surface-micromachined MEMS devices. We have performed nanopositioning resolution tests on a MEMS thermal actuator, both open and closed loop, to demonstrate the performance improvements possible with feedback control. A thermomechanical in-plane microactuator (TIM), fabricated using the MUMPS fabrication process, was used in this study. The actuator was coupled to a piezoresistive displacement sensor (PRDS) that was fabricated as part of the same process. Measurements of the actuator output, taken using a scanning electron microscope, show that nanopositioning repeatability improved from ±59 nm to ±31 nm when feedback control is employed.
Spray Cooling of Small-Pitched, Straight-Finned, Copper Heat Sinks
Authors: Coursey Johnathan S. , Kim Jungho , Kiger Kenneth T.
Published: April 2008

Spraying a dielectric liquid such as PF-5060 (95% pure FC-72) has been shown to be an effective method of cooling high power electronics. Recent studies have illustrated the potential enhancement of spray cooling by the addition of extended structures, particularly straight fins, to the heated surface. In the current work, these studies are extended to finer fin widths and pitches and longer fin lengths. Four such heat sinks were EDM wire machined. These 1.41 × 1.41 cm2 heat sinks featured a fin pitch of 0.86 mm; a fin width of 0.5 mm; and fin lengths of 0.5 mm, 1 mm, 3 mm, and 5 mm, which substantially increase the total area, allowing more residence time for the incoming liquid to be heated by the wall. The four enhanced surfaces and a flat surface with the same projected area were sprayed with a full cone nozzle using PF-5060 at 96 mL/min, 24°C, and 3.65 atm (38.5 psig). In all cases, the enhanced surfaces improved thermal performance. Longer fins were found to outperform shorter ones in the single-phase regime. Adding fins also resulted in two-phase effects and higher heat transfer at lower wall temperatures than the flat surface. Finally, the two-phase regime appeared to be marked by a balance between added area, changing flow flux, channeling, and added conduction resistance. Although critical heat flux (CHF) was not reached for the finned surfaces, fin lengths between 1–3 mm appeared to be optimum for heat fluxes as high as 131 W/cm2 and the range of conditions studied.
An Approach for Micro End Mill Frequency Response Predictions
Authors: Cheng Chi-Hung , Schmitz Tony L. , Arakere Nagaraj , Duncan G. Scott
Published: April 2008

A method for predicting the tool point frequency response of a tool-holder-spindle system is provided. Receptance coupling is used to analytically combine responses for the tool, holder, and spindle substructures and predict the assembly dynamics. The spindle response is determined using experimental procedures, while the holder and tool are modeled using Timoshenko beams. With the use of this method, predictions may be completed for micro scale end mills where impact testing is inconvenient. Experimental results are provided.
Pool Boiling of FC-72: A Comparison of Two Thin Porous Coatings on Heat Transfer Enhancement
Authors: Xu Kuiyan , Lloyd John R.
Published: April 2008

The present research is an experimental study of pool boiling behavior of surfaces coated with thin porous layers. The fluid employed is FC-72, a highly-wetting dielectric perfluorocarbon with zero ozone-depletion potential (ODP). This creates the potential for electronic cooling application. Different surfaces, including the super-smooth surface (SSS), the High Flux™ surface (HFS), and the new electrochemical deposition surface (EDS) were tested, and the test results were compared. Both subcooled and saturated fluid pools were studied. The boiling hysteresis phenomenon was studied for these surfaces under different boiling conditions, which include the fluid bulk temperature and the non-boiling immersion time. Results of the study showed that the porous-coated surface dramatically enhanced the nucleate boiling heat transfer performance. The boiling hysteresis phenomenon is more prominent on porous-coated surfaces than on smooth surfaces, and subcooling can deteriorate this phenomenon.
Autonomous, Line-Tracking Vehicles: A Mechatronics Term Project
Authors: Murray William R.
Published: April 2008

A six-week term project used in a senior-level mechatronics course at Cal Poly State University is described. In this project, teams of students each design and build an autonomous, line-tracking vehicle to compete in an end-of-quarter competition. The rules for the project are as follows: Design, build and demonstrate a microcontroller-controlled vehicle to race two laps around a closed course delineated by white tape on a black table. On the first lap, the vehicle will encounter two racquetballs positioned randomly on straightaway sections of the track. The vehicle should capture both racquetballs, bring the captured balls back to the starting area, and place the captured balls into a corral situated adjacent to the start/finish line. Each vehicle is scored on elapsed time and reliability, which are weighted equally. Time trials are held in the lab on Tuesday of the tenth and final week of class in the academic quarter. The fraction of teams achieving at least one successful run, that is, corralling both balls after completing two laps, has steadily increased over the six times this project has been used, and has recently been as high as 100 percent. Similarly, the record elapsed times have steadily fallen.
Force Feedback in Dynamic Atomic Force Microscopy
Authors: Stark R. W.
Published: April 2008

The feedback perspective of dynamic AFM provides a powerful tool to investigate the non-linear system dynamics from a system theoretic point of view. Including the higher order dynamics of the extended cantilever beam in the model the contact resonances can be reproduced faithfully without the need to solve the partial differential equation of motion directly. The investigation of the non-linear dynamics provides valuable insight into the generation of higher harmonics in dynamic AFM. However, the light lever detection scheme is widely used in dynamic AFM. This means that — strictly speaking — the tip-deflection is not a measurable quantity: the local deflection angle is measured but not the deflection itself. Additionally, time-delays may be introduced into the system influencing the dynamic behavior. Apart from system inherent time delays, a delayed force feedback is often used in order manipulate the system’s resonance characteristics (quality factor). Such an active control of the oscillatory behavior of the cantilever used in atomic force microscopy (AFM) allows one to tune the quality factor to purpose. For experiments requiring a high force sensitivity an enhancement of the quality factor is desirable whereas in time critical experiments additional damping may be needed. In order to control the quality factor a feedback signal is used that approximates the time derivative of the system state within the bandwidth of interest.
Design and Implementation of a PKM Based 5-Axis Reconfigurable Machine
Authors: Orban Peter E. , Bi Zhuming M. , Lang Y. T. , Verner Marcel
Published: April 2008

In this paper we present the design and implementation of a parallel kinematics based reconfigurable machine. The machine utilizes a Tripod based module with 3 degrees-of-freedom combined with a linear X-Y stage and gantry system for 5-axis machining. The tripod module uses a unique passive link mechanism with constant length leg actuators. This architecture offers good stiffness and high accuracy. The gantry system itself is reconfigurable, allowing for changing the working characteristics of the machine. The control system is based on open architecture principles. Corresponding to the mechanical reconfiguration, the control system also needs to be reconfigured to reflect the actual state of the machine. Mechanical reconfiguration also brings with it the need to verify the accuracy of the new configuration. Also discussed in the paper is the calibration methodology that ensures high production quality in each configured mode of the machine.
Liquid Displacement Through Tube-Annular Transition Region Inside Oil Wells
Authors: Dutra Eduardo S. S. , Naccache Moˆnica F. , Souza Mendes Paulo R. , Martins Andre´ L. , de Miranda Cristiane R.
Published: April 2008

In this work, a numerical simulation of three adjacent fluids flowing through a tube followed by an annular axi-symmetric channel is performed. This analysis is motivated by the study of drilling and completion processes of oil wells, where a cement slurry pushes the drilling mud, used in the drilling process to lubricate the drill and to remove the produced drilling cuts. The completion process is perfect if all the drilling mud is removed, and if there is no contamination between the two fluids. To avoid contamination, a spacer fluid is usually inserted between them. Both drilling mud and cement slurry behave as non-Newtonian fluids, and the spacer fluid can be Newtonian or non-Newtonian. The analysis of flow and interface configuration between these fluids helps to determine contamination, and is an important tool for the process optimization. The numerical solution of the governing conservation equations is obtained with the Fluent software, using the finite volume technique and the volume of fluid method. The effects of rheological parameters and pumped volume of the spacer fluid are investigated. The results obtained show that the displacement is better when a more viscous spacer fluid is used. The results also shown zones of recirculation, where the drilling mud remains stagnant, decreasing the process efficiency.
Appropriate Design of Medical Technologies for Emerging Regions: The Case of Aurolab
Authors: Sandhu Jaspal S. , Bhandari Aman , Ibrahim Mahad , Balakrishnan P.
Published: April 2008

Healthcare delivery in emerging regions presents a unique set of challenges and is characterized largely by poor infrastructure. Though there is significant variation from country to country - and even within countries - in emerging regions, common themes emerge, such as overreliance on direct payment schemes, unreliable supply chains, and intermittent power in rural settings. These themes in turn impose particular design requirements on manufacturers of medical devices and pharmaceuticals; this paper focuses on these design requirements. We illustrate the importance of designing specifically for the developing context, using the example of Aurolab, a non-profit medical manufacturer located in Tamil Nadu, India. Started in 1992, Aurolab began operations with the manufacture of intraocular lenses (IOL), implantable polymer lenses for cataract surgery, becoming the first to produce this technology in India. Today Aurolab produces a variety of medical devices and ophthalmic pharmaceuticals, and deliver their products to 120 countries worldwide. Aurolab’s products illustrate many of the key design requirements for healthcare delivery in India and in other emerging contexts.
Evaluation of Heavy Truck Rollover Crashworthiness
Authors: Evans Jeffrey L. , Batzer Stephen A. , Andrews Stanley B. , Hooker Robert M.
Published: April 2008

Heavy trucks (those having a gross vehicle weight rating of greater than 10,000 pounds) are an essential part of the United States economy and account for 4% of all registered vehicles. The large size and weight of these vehicles can pose a serious safety threat to the vehicle’s occupants in the event of a rollover collision. The rollover crashworthiness of heavy trucks, in particular the structural integrity of the cab, is analyzed in this paper. An actual rollover accident was analyzed and the cab design of an exemplar vehicle was evaluated. Modifications were made to the exemplar and an inverted drop test onto the roof of the cab was conducted. Recommendations for improving the rollover crashworthiness of heavy trucks are provided. An analysis of heavy truck rollover accidents was also conducted for data available from 1994-2002 by submitting queries to the Fatality Analysis Reporting System (FARS), which is administered by the National Highway Safety Administration (NHTSA), in order to determine the number of incapacitating and fatal injuries that occurred when the occupants were contained in the cab during a rollover accident. The percentage of incapacitating and fatal injuries for restrained occupants was determined by analyzing the rollover data obtained from the FARS rollover query that was used and was found to be 35%. Therefore, restrained occupants in heavy trucks can sustain significant injuries during rollover accidents, in part, due to insufficient rollover crashworthiness.
Aeroelastic Flutter at the Free Edges of Uni-Axially Tensioned Webs and Thin Films
Authors: Bidkar Rahul A. , Raman Arvind , Bajaj Anil K.
Published: April 2008

Aero elastic flutter may play an important role in the breakage of thin membrane-like structures (a.k.a. webs) found in paper-handling, textile, sheet-metal and magnetic tapes industry. In this article, we examine the aero elastic stability of a web modeled as a uni-axially tensioned (along the machine direction) low aspect ratio Kirchhoff plate, which is subject to a fluid flow in the cross machine direction. Panel methods based on the distribution of singularity solutions (sources and doublets) on the surface of the web are used to numerically solve the problem of 3D unsteady potential flow surrounding the web. The equation of motion of the plate coupled to a fluid flow is discretized by using Galerkin’s method. The discretization is performed in the configuration space formulation of the gyroscopic eigenvalue problem. The linear stability of this reduced order system is investigated. The onset of flutter instability as a function of base fluid flow in the cross machine direction is studied. The effects of fluid coupling on the frequencies and modes of oscillations of the web are also studied.
Hierarchical Design of Phononic Materials and Structures
Authors: Hussein Mahmoud I. , Hulbert Gregory M. , Scott Richard A.
Published: April 2008

Within periodically heterogeneous materials and structures, wave scattering and dispersion occur across constituent material interfaces leading to a banded frequency response. A novel multiscale dispersive design methodology is presented by which periodic unit cells are designed for desired frequency band structures, and are used as building blocks for forming fully or partially periodic structures, typically at larger length scales. Structures resulting from this hierarchical design approach are tailored to desired dynamical characteristics without the necessity for altering the overall geometric shape of the structure nor employing dissipative damping materials. Case studies are presented for shock isolation and frequency sensing.
Irradiiaton-Induced Defect Self-Organizatoin
Authors: Salac David , Lu Wei
Published: April 2008

Experiments show that vacancies in a solid may coalesce into voids and self-organize into a super-lattice. The voids have diameters around 10 nm and spacing of tens of nanometers. This paper develops a thermodynamic model to explain and simulate the remarkable phenomena. We incorporate free energy of mixing, interface energy and elasticity into a continuous phase field model. It is well known that the total interface energy reduces when the voids grow larger. Simulations show that elastic anisotropy may limit the coarsening. Starting from randomly distributed vacancies, the process of coalescence and void lattice formation demonstrates rich dynamics. Long-range elastic interaction and elastic anisotropy are found to play a significant role that determines the self-assembled super-lattice.
AB Initio Simulation on Grotthuss Mechanism
Authors: Han Jiahua , Liu Hongtan
Published: April 2008

Ab initio simulations on Grotthuss mechanism have been carried out. Using the simulation results together with the existing experimental data, all the popular propositions for Grotthuss mechanism, including the one recently proposed by Noam [1], have been checked. Combining with the charge distribution calculation and the movement of the positive charge center inside the protonated water cluster during the proton diffusion process, only one mechanism is shown probable, while all the other proposed mechanisms are excluded. According to this probable mechanism, the high mobility of proton inside water is caused by the high diffusion rate of H5O2+, while the diffusion of H5O2+ is mainly induced by the thermal movement of water molecules at the second solvation shell of H5O2+ cation and the Zundel polarization inside the cation ion. Furthermore, the external field and thermo-dynamic effects play important roles during the transport process by affecting the reorientation of water molecules at the neighborhood of the second solvation shell of H5O2+ to induce the Zundel polarization and by providing the energy for the cleavage of the hydrogen bond between a newly formed water molecule and H5O2+. Because the weight (fraction) of H5O2+ among protonated water clusters decreases as temperature increases, this proposed mechanism is considered to play the dominant role only when temperature is below 572 K, above which, protons transport by other mechanisms become dominant.
Experimental Characterization of Laser-Assisted Mechanical Micromachining (LAMM) Process
Authors: Singh Ramesh , Melkote Shreyes N.
Published: April 2008

There is growing demand for micro and meso scale devices in the field of optics, semiconductors and bio-medical devices. In response to this demand, mechanical micro-cutting (e.g. micro-turning, micro-milling) is emerging as a viable alternative to lithography based micromachining techniques. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials such as mold and die steels, limitations in cutting tool stiffness and strength are major impediments to the use of mechanical micromachining methods. This paper presents a Laser Assisted Mechanical Micromachining (LAMM) process that involves highly localized thermal softening of the hard material by focusing a solid-state continuous wave/pulsed laser beam in front of a miniature (100μm–1mm wide) cutting tool. By suitably controlling the laser power, location and spot size, it is possible to cause a sufficiently large decrease in the strength of the work material and thereby minimize catastrophic tool failure and lower tool forces and deflection. This paper presents the results of experimental characterization of the LAMM process. Micro scale grooving experiments are conducted on H-13 mold steel (42 HRc) in order to understand the influence of the laser variables (laser power, beam location with respect to tool) and cutting parameters (depth of cut, cutting speed and tool width) on the cutting forces and surface finish. The results show that, for a given cutting condition, these process responses are significantly influenced by the laser variables. Plausible explanations for the observed trends are given.
A Model for Contaminant Transport, Aggregation and Deposition in Lubricated Contact of Rough Surfaces
Authors: Cheng W. , Farhang K. , Kwon Y.
Published: April 2008

Effective prediction of lubricated contact poses an especially challenging problem. On the one hand surfaces are non-smooth at micron-scale while, on the other hand, a lubricant contains varying degrees of impurities in form of particle contaminants. An accurate model for lubricated contact, therefore, must be able to account for the various interactions that include particle-fluid, particle-particle, fluid-rough surface, particle-rough surface and rough surface-rough surface interactions. In the current study we propose the use of Lattice Boltzmann Method (LBM) and JKR theory for elasto-adhesive contact to simulate the particle transport processes in a lubricant flow between two rough surfaces. A particle dynamics simulation method is proposed to predict the interaction of a group of particles. The particle-particle and particle-boundary interactions are modeled by an extension of the JKR theory in which viscoelastic interactions are included through the implementation of the Kelvin-Voigt stress-strain relations. The particle-fluid interaction is calculated from the LBM simulation. Time scale relations between LBM and particle dynamics are characterized. Simulation results show the effects of particle density and surface roughness on frequencies of particle-particle and particle-boundary impacts, particle deposition rate, particle cluster forming and fluid boundary pressure changes due to particle deposition. A parametric study is performed to elucidate the effect of rough surface geometry and the relative velocity of the surfaces on friction and lift. The results provide fundamental insight on the contamination effects on wear and life of lubricated surfaces.
Numerical Modeling of an Ion-Drag Micropump Performance
Authors: Benetis Vytenis , Shooshtari Amir , Ohadi Michael
Published: April 2008

This paper presents a numerical model for the electrophoretic force interaction in dielectric liquids, and results of applying this model to a multi-stage planar ion-drag micropump. Experimental results were checked against a mono-ionic numerical model results and good agreement was found. The model takes into account the unipolar charge injection with ohmic conduction where the migration of only one type of charge carriers (positive or negative) is simulated. The EHD governing equations are deduced from two basic sets of equations, namely, Maxwell’s equations and fluid flow conservative equation. Under special assumptions, these equations are simplified to form the governing equations of EHD. With the help of numerical model optimization of the planar ion-drag micropump geometrical design is offered.
Electrical and Electronic Equipment Recovery and Recycling in Turkey
Authors: Tumkor Serdar , Sutherland John W. , Kumar Vishesh V.
Published: April 2008

Discarded electrical and electronic equipment contains valuable materials, low value parts, and hazardous substances. There is a growing concern regarding the management of end-of-use equipment owing to the environmental concerns associated with discarding used devices. Electronic waste or scrap consumes valuable landfill space and may ultimately contaminate groundwater sources. In addition, replacing discarded components with new components typically consumes valuable virgin material resources. With the advent of the WEEE (Waste Electrical and Electronic Equipment) Directive, used electrical and electronic products are now being recovered in Turkey as a European Union (EU) candidate country, and several companies in Turkey have begun to recover latent value through disassembly and reuse/recycling of materials and components. To remain competitive, these companies must implement economical and environmentally responsible recovery processes. There are a number of research challenges associated with product recovery. This paper describes the current product recovery infrastructure in Turkey, and discusses future trends and drivers for successful product take-back.
Effect of Waveform on the Effectiveness of Tangential Dither Forces to Cancel Friction-Induced Oscillations
Authors: Michaux Michael A. , Ferri Aldo A. , Cunefare Kenneth A.
Published: April 2008

High-frequency dither forces are often used to reduce unwanted vibration in frictional systems. This paper examines how the effectiveness of these dither-cancellation techniques is influenced by the type of periodic signal employed. The paper uses the method of averaging as well as numerical integration to study a single-degree-of-freedom (SDOF) system consisting of a mass in frictional contact with a translating surface. Recently, it was found that sinusoidal dither forces had the ability to stabilize or destabilize such a system, depending on the system and frictional characteristics as well as the amplitude and frequency of the dither signal [1]. This paper extends this analysis to general, periodic dither forces. In particular, the system response for sinusoidal dither waveforms is compared to that of triangular dither waveforms and square dither waveforms. It is found that, for a given amplitude and frequency of the dither signal, square waveforms are much more effective in canceling friction-induced oscillations than sinusoidal dither; likewise, sinusoidal waveforms are more effective than triangular waveforms for a given amplitude and frequency. A criterion is developed that relates the effectiveness of the waveform to the properties of the integral of the dither signal.
On the Dynamics of Particle-Particle Interaction
Authors: Cheng W. , Farhang K. , Kwon Y.
Published: April 2008

In numerous engineering and science applications understanding the dynamic behavior of two interacting particles plays an indispensable role as it is the foundation based upon which the behavior of a large number of particles may be predicted. When two particles interact, two prominent forces of adhesion and elasticity are at work and, in some respect, in competition. This is especially true when particle-particle collision dynamics is of interest. Upon collision, two particles either develop physical bond, coalesce to form an agglomeration or rebound, each following a distinct path. A promising theory to address particle-particle collision dynamics is due to Johnson, Kendal and Roberts [1] referred to as the JKR method. However, JKR suffers from two main shortcomings in application to particle dynamics. These are (1) implicit relations between force and displacement and (2) representation of a two-particle system as a conservative system. These shortcomings were treated in [2] by first deriving a highly accurate approximate equation based on the JKR theory in which force and displacement are explicitly related and the extension of the JKR theory wherein the Kelving-Voigt viscoelastic model is used instead of the elastic model. This formulation provides an opportunity to study particle-particle collision dynamics, which is the study in the present paper.
A Dislocation Based Gradient Plasticity Theory With Applications to Size Effects
Authors: Abu Al-Rub Rashid K. , Voyiadjis George Z.
Published: April 2008

The intent of this work is to derive a physically motivated mathematical form for the gradient plasticity that can be used to interpret the size effects observed experimentally. This paper addresses a possible, yet simple, link between the Taylor’s model of dislocation hardening and the strain gradient plasticity. Evolution equations for the densities of statistically stored dislocations and geometrically necessary dislocations are used to establish this linkage. The dislocation processes of generation, motion, immobilization, recovery, and annihilation are considered in which the geometric obstacles contribute to the storage of statistical dislocations. As a result a physically sound relation for the material length scale parameter is obtained as a function of the course of plastic deformation, grain size, and a set of macroscopic and microscopic physical parameters. The proposed model gives good predictions of the size effect in micro-bending tests of thin films and micro-torsion tests of thin wires.
Effect of Suspension and Body Flexibility on Dynamic Behavior of Passenger Cars
Authors: Durali M. , Kasaiezadeh A. , Nakhjavani O. B.
Published: April 2008

The usual practice in vehicle dynamic modeling is to consider the body and suspension components as rigid elements. The question this paper is trying to answer is; how large the errors will be if flexibility of the components are not considered in vehicle dynamic model. The flexible vehicle model made for this study has 300000 elements which are generated using Super-element analysis in MSC/NASTRAN and made usable in MSC/ADAMS environment using Craig-Bampton theorem. The full vehicle model made in ADAMS has 200 degrees of freedom and includes all bushings, mechanism, power train, and suspension system. The model was used in simulating ride and handling behavior of the vehicle in several virtual road conditions. The results show that although a rigid car model will result errors in handling behavior, but these errors are all towards increased safety margin when used in design process. On the contrary using a rigid model in vibration and ride analyses of the car tend to suppress the vibrations, and a flexible model markedly affect the vibration modes of the body and the suspension system components
NASA Student Programs and Senior Capstone Design Experience
Authors: Parang M. , Naumov V. I. , Taylor L. A.
Published: April 2008

A significant way to attract engineering students, especially aerospace and mechanical engineering majors, to space issues is to implement exciting NASA student programs into the senior-year capstone design experience. Three years ago the University of Tennessee’s Mechanical, Aerospace and Biomedical Engineering Department offered two new projects, named “Microgravity” and “Lunar Rover Vehicle”, as senior capstone design projects. Both require participation, on a competitive basis, in two corresponding NASA programs: “The Reduced Gravity Student Flight Opportunities Program” and “The Great Moonbuggy Race”. Three years of experience have demonstrated that both programs are very suitable in offering senior students unique opportunities to improve their analytical abilities, develop design skills, gain experience in working in multi-disciplinary teams, solve cutting-edge engineering problems, and familiarize themselves with space issues and technical problems.
Preferential Orientation of Silicon Blocks During Fluidic Self-Assembly of Microelectronics
Authors: Brasoava Adriana , Danescu Radu , Srinivasan Visvanathan , Wells David
Published: April 2008

Fluidic Self-Assembly (FSA) is a newly developed, high productivity method to assemble millimeter and submillimeter size silicon electronic components (blocks) into circuit boards. Large numbers of thin, truncated pyramid shaped components are released in water and move gravitationally down inclined substrates to fall into indentations (receptors) of complementary shape. To increase the rate of receptor filling and improve the process efficiency, the probability of proper alignment between blocks and receptors must be maximized. The present paper reports an experimental study aimed at determining the preferential orientation of the blocks in a practical FSA process. Blocks ranging in size from 1050 to 3050 microns were tested for: (i) in-plane orientation angle during their motion, and (ii) right-side-up (RSU) versus up-side-down (USD) landing upon dispensing. Results indicate that blocks exhibit a high degree of in-plane angular self-orientation, which depends on the block aspect ratio. Spatial orientation of blocks at the release point is a decisive factor on their correct (RSU) landing on the substrate. Based on this observation, an original dispensing strategy was developed that increased the RSU fraction to values typically over 90%.
Synthetic Jets for Thermal Management of Microelectronic Chips
Authors: Erbas N. , Koklu M. , Baysal O.
Published: April 2008

Thermal control of electronic devices has been an active research area of heat transfer technologies. The impetus is straightforward: decreasing the temperature of a component increases its performance as well as its reliability. In the present study, a single microchip is placed in a 2D channel. A simple triangular cavity configuration is used to investigate the effectiveness of a synthetic jet for its thermal management. The study presents altered main channel flow results for various synthetic jet configurations and different membrane oscillation frequencies. The effect is that synthetic jet enhances mixing by imparting momentum to the channel flow thus manipulating the temperature field in a positive manner. Computations carried out for both continuum and slip flow regimes.
Design and Performance of a MR Torque Transfer Device
Authors: Molyet Kevin , Ciocanel Constantin , Yamamoto Hideki , Naganathan Nagi
Published: April 2008

Magnetorheological (MR) fluids possess the unique ability to undergo dramatic and nearly completely reversible changes in their rheological properties under the application of a magnetic field. These controllable fluids can serve as quiet, rapid interfaces between electronic controls and mechanical systems. One area of application is to use these fluids in torque transfer devices, such as clutches and brakes. After determining MR fluid properties and behavior using a rheometer, a parallel disk type MR clutch was successfully developed, which utilized a stationary electromagnetic coil. Finite element analysis was used to design the coil and clutch assembly in order to maximize the magnetic field generated within the MR fluid. The resulting magnetic field was uniform over the active portion of the clutch, easily controllable by adjusting the current passing through the coil, and provided a large range of field strength values. The experimentally measured output torque was generally in good agreement with predicted values. This work will detail the design considerations and methodology used to develop this clutch, which can be extended to the design of other MR devices.