bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Property and Processing Investigation of Pulsed Laser Deposited Al2O3 and AlN-TiN Thin Films
Authors: Wang Xinyu , Waters Cindy , Yarmolenko Sergey , Kumar Dhananjay , Sankar Jagannathan
Published: April 2008

We have grown alumina (Al2O3) and Aluminum Nitride - Titanium Nitride (AlN-TiN) multilayer thin films on (100) silicon substrates using KrF excimer pulsed laser. Hardness, Young’s Modulus and fracture toughness of the films were analyzed using Vickers and nanoindentation methods. The films with thicknesses ranging from 0.2 mm to 1.0 mm were tested under indentation loads as small as 100mN with the MTS nanoindentor up to 3000 mN with the Vickers test. By studying the Al2O3 and AlN-TiN films on the Si substrates we were able to assess the fracture toughness and the nature of the cracking and delamination. The effects of the processing parameters (laser energy and substrate temperature) on these films were studied. The fracture toughness was analyzed by different methods.
Multi-Scale Micro-Mechanical Poroelastic Modeling of Fluid Flow in Cortical Bone
Authors: Swan Colby C. , Kim Hyung-Joo
Published: April 2008

To explore the potential role that load-induced fluid flow plays as a mechano-transduction mechanism in bone adaptation, a lacunar-canalicular scale bone poroelasticity model is developed and exercised. The model uses micromechanics to homogenize the pericanalicular bone matrix, a system of straight circular cylinders in the bone matrix through which bone fluids can flow, as a locally anisotropic poroelastic medium. In this work, a simplified two-dimensional model of a periodic array of lacunae and their surrounding systems of canaliculi is developed and exercised to quantify local fluid flow characteristics in the vicinity of a single lacuna. When the cortical bone model is loaded, microscale stress and strain concentrations occur in the vicinity of individual lacunae and give rise to microscale spatial variations in the pore fluid pressure field. Consequently, loading of cortical bone can induce fluid flow in the canaliculi and exchange of fluid between canaliculi and lacunae. For realistic bone morphology parameters, and a range of loading frequencies, fluid pressures and fluid-solid shear stresses in the canalicular bone are computed and the associated energy dissipation in the models compared to that measured in physical in vitro experiments on human cortical bone. For realistic volume fractions of canaliculi, deformation-induced fluid flow is found to have a much larger characteristic time constant than deformation-induced flow in the Haversian system.
A Parametric Study on Gravity-Induced Brain Shift Using a Three-Dimensional FE Model of the Human Brain
Authors: Lee Jong B. , Hu Jingwen , Zhang Liying , Yang King H. , King Albert I. , Zamorano Lucia
Published: April 2008

The mass density, shear modulus, bulk modulus and decay constant of brain tissues play important roles when calculating gravity-induced brain shift during brain surgery. A parametric study was conducted to determine the effect of these properties on gravity-induced brain shift, using a three-dimensional (3D) finite element (FE) model of the human brain that was developed at Wayne State University (WSU). Results from this parametric study indicate that the magnitude of brain shift altered significantly due to changes in a combination of the shear modulus and bulk modulus of the brain.
Development of a Testing Facility for Experimental Investigation of MEMS Dynamics
Authors: Ozdoganlar O. Burak , Epp David S. , Reu Philip L. , Sumali Hartono
Published: April 2008

Dynamic characteristics of overhung and/or moving components play a pivotal role in determining the overall performance and reliability of microsystems (MEMS). In addition to the structural dynamics of the components, the response is very sensitive to multi-physics phenomena such as electrostatics, gas damping, and friction. Therefore, the ability to experimentally analyze linear and nonlinear dynamics of microsystems under varying environmental conditions is very important. This paper describes a facility for experimental investigation and validation of linear and nonlinear dynamic response of microsystems under varying environmental conditions. A detailed account of the facility components and software developed for excitation and data collection is given. Experimental results and discussion for various MEMS structures are included to illustrate the effectiveness of the experimental facility.
Enhancement of Design and Manufacturing Curriculum Through Rapid Prototyping Practices
Authors: Fidan Ismail , Patton Ken
Published: April 2008

Advances in computer technology opened new horizons in teaching Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM) technologies. This paper will report the outcomes of two current NSF grants, 0311586 and 0302314, funded on Rapid Prototyping (RP) curriculum development. The objective of these RP projects is to provide advanced instruction and laboratory practices in the areas of CAD/CAM/CAE through challenging laboratory assignments and industrial projects that are integrated into any engineering curriculum. These projects create web-based materials, and also adapt and implement RP experiences and educational practices following successful similar models at various engineering schools to enhance pedagogy in design and manufacturing curriculum. Enhanced RP capabilities enable the students to build physical models directly from CAD data, where the prototype communicates important information about parts, including engineering data such as fit and limited functional testing, labeling, highlighting, and appearance simulation. Developed RP labs are used in junior and senior level design and manufacturing courses, including the senior capstone courses.
Micro-LIF Measurement in a Micro-Channel Using an Ultra-Thin Laser Light Sheet
Authors: Yoon Sang Youl , Kim Jae Min , Kim Su Hun , Kim Kyun Chun
Published: April 2008

Measurement of concentration fields in a micro-channel is the crucial technology in the area of Lab-on-a-chip to be used for various bio-chemical applications. It is well-known that the only possible way to measure the concentration field in the micro-channel is using micro-LIF(Laser Induced Fluorescence) method. However, an accurate concentration field at a given cross plane in a micro-channel has not been made so far due to the limit of light illumination. The present study demonstrates a novel method to provide an ultra thin laser sheet beam having 5 microns thickness by a micro focus laser line generator. Nile Blue A was used as fluorescent dye for LIF measurement. The laser sheet beam illuminates an exact plane of concentration measurement in the micro-channel to increase the signal to noise ratio and reduce the depth uncertainty considerably.
Developing a Multisemester Interwoven Dynamic Systems Project to Foster Learning and Retention of STEM Material
Authors: Avitabile Peter , Pennell Stephen , White John
Published: April 2008

Students generally do not understand how basic STEM (Science, Technology, Engineering and Mathematics) material fits into all of their engineering courses. Basic material is presented in introductory courses but the relationship of the material to subsequent courses is unclear to the student since the practical relevance of the material is not necessarily presented. Students generally hit the “reset button” after each course not realizing the importance of basic STEM material. The capstone experience is supposed to “tie all the pieces together” but this occurs too late in the student’s educational career. A new multisemester interwoven dynamic systems project has been initiated to better integrate the material from differential equations, mathematical methods, laboratory measurements and dynamic systems across several semesters/courses so that the students can better understand the relationship of basic STEM material to an ongoing problem. This paper highlights the overall concept to be addressed by the new approach. The description of the project and modules under development are discussed.
Development of a Multilayer Mesoscale Burner Array for Gas Turbine Reheat
Authors: Lee S. , Edwards C. F. , Bowman C. T.
Published: April 2008

Mesoscale burner arrays allow combustion to be conducted in a distributed fashion at the millimeter (meso) scale. At this scale, diffusive processes are fast, but not yet dominant, such that a number of advantages over conventional burners can be achieved without giving up the possibility to use fluid inertia to advantage. Since the scale of the reaction zone follows from the scale at which the reactants are mixed, very compact flames result. We expect that this compact, distributed form of combustion can provide not only the opportunity of inter-turbine reheat, but also the potential for lean premixed or highly vitiated combustion to suppress NOX emissions. In previous work, a 4×4 array, with burner elements on 5-mm centers, was fabricated in silicon nitride using shape deposition manufacturing. Results from both fully premixed (mixing prior to the array) and partially premixed (mixing in the array) configurations demonstrated the degree to which premixed performance can be achieved with this design and pointed to ways in which the array design could be improved. In the present work, a next-generation 6×6 array has been developed and tested. Major design changes in this array include use of a combination of bluff-body and swirl flame stabilization and a multilayer architecture with a separate fuel manifold for more uniform fuel distribution. In this multilayer design, the array is fabricated in three separate pieces, one of which is a vaporization layer designed for use with liquid fuels. Results using gaseous fuel (methane) in a fully premixed operating condition, including pressure drop, flame stability, temperature distribution in the burned gas, and NOx emissions, are reported for both bluff-body and no-bluff-body configurations. Tests for a partially premixed configuration are being carried out to evaluate the potential of the design modifications.
Analytical Three-Dimensional Solution for Heat Sink Temperature
Authors: Lehtinen Antti , Karvinen Reijo
Published: April 2008

In the paper an analytical steady-state solution for heat transfer in a heat sink is presented. The heat sink consists of an array of fins and a base plate. The array is cooled by forced convection. There is a prescribed heat flux distribution at the bottom of the base plate. In order to obtain an analytical solution the assumption of a constant heat transfer coefficient is made. Furthermore, the array is assumed to be so short that the centerline temperature of the flow equals that of the free stream. The results are applied to a specific case of a single heat source, which generates constant heat flux and is mounted at the center of the bottom of the base plate. The use of the results is illustrated with a couple of simple numerical examples.
Mechanics and Dynamics of Hard Turning Process
Authors: Buyukhatipoglu Kivilcim , Lazoglu Ismail , Kratz Hubert , Klocke Fritz
Published: April 2008

In precision machining, due to the recent developments on the cutting tools, machine tool structural rigidity and improved CNC controllers, hard turning is an emerging process as an alternative to some of the grinding processes by providing reductions in costs and cycle-times. In industrial environments, hard turning is established for geometry features of parts with low to medium requirements on part quality. Better and deeper understanding of cutting forces, stresses and temperature fields, temperature gradients created during the machining are very critical for achieving highest quality products and high productivity in feasible cycle times. In order to enlarge the capability profile of the hard turning process, this paper introduces to prediction models of mechanical and thermal loads during turning of 51CrV4 with hardness of 68 HRC by CBN tool. The shear flow stress, shear and friction angles are determined from the orthogonal cutting tests. Cutting force coefficients are determined from orthogonal to oblique transformations. Cutting forces and surface profiles are predicted and compared with experimental measurements.
Experimental Investigation on the Roles of Chemical Corrosion and Mechanical Polishing on Copper CMP
Authors: Tsai Jhy-Cherng , Shieh Yaw-Yi , Tsai Ming-Shih , Dai Bau-Tong
Published: April 2008

This paper is an experimental investigation on the roles of chemical corrosion and mechanical polishing of the chemical mechanical polishing (CMP) of wafers with copper film of 1,000 nm thickness. Three types of experiments are designed and conducted: chemical corrosion, mechanical polishing, and CMP with φ0.3μm Al2O3 as abrasives. The results showed that copper films after PVD and annealing sustain tensile stress that intensifies corrosion rate. In general, the stress of copper film increases at higher annealing temperature and the corrosion rate increases correspondingly though the relationship is weak. The polishing rate of pure mechanical polishing is about the same as that of pure chemical corrosion, but surface roughness of mechanical polishing and CMP are much better than that of chemical corrosion. Furthermore, the removal rate of mechanical polishing and chemical corrosion, about 2nm/min, are relatively low compared to that of CMP, about 30nm/min, it indicates that the removal mechanism of CMP is not simply a linear superposition of chemical corrosion and mechanical polishing. The strong interaction and the combined reaction of chemical corrosion and mechanical polishing need further investigation.
Oxygen Separation/Enrichment From Atmospheric Air Using Magnetizing Force
Authors: Asako Yutaka
Published: April 2008

The possibility of oxygen separation/enrichment from atmospheric air using a magnetizing force was investigated numerically. Direct Simulation Monte Carlo (DSMC) method was utilized to obtain distribution of oxygen concentration in a capsule under a strong magnetic field gradient. The molecular movement was calculated by taking into account the magnetizing force on the molecules. The computations were performed for a wide range of pressure and magnetic flux density gradient. The simulation results showed that there is a possibility of oxygen separation/enrichment from atmospheric air under a strong magnetic field gradient.
Mechanisms of Jet Breakdown in Nanoliter Dispensers
Authors: Goldschmidtboeing F. , Woias P.
Published: April 2008

We present a classification scheme for different breakdown mechanisms of free jets. In addition to the well discussed mechanism of absolute instability two further mechanisms, the breakdown due to the wetting of the nozzle surface and the breakdown due to the recoiling of the jet, are introduced. All mechanisms are described by analytical theory and numerical simulations. Special emphasis is given to the influence of the cross section shape of the nozzle. Experiments conducted with our nanoliter dispenser with a square shaped nozzle affirm the theoretical results for the recoiling mechanism.
The Use of Second Order System Equation in the Micro Electro Mechanical System (MEMS) Education
Authors: Dong Haifeng , Zhang Haixia , Hao Yilong
Published: April 2008

A major challenge in Micro Electro Mechanical System (MEMS) education, is dealing with the multi-disciplinary nature of the field, which may include solid mechanics, fluid mechanics, electronics etc. Instead of teaching these subjects independently, we link this multi-disciplinary knowledge domain by the second-order system equation. In addition, the related CAD software is introduced during the explanation of the second order system equation. This teaching method makes the student understand MEMS more quickly and systemically, and if needed, they can seek the related knowledge and study further on their own.
Modeling Friction Wedges: Part II — An Improved Model
Authors: Klauser Peter E.
Published: April 2008

Friction wedges are a critical but imperfectly understood component in the typical North American three-piece freight car truck. A companion paper has reviewed the “state-of-the-art” in modeling this crucial suspension element. This paper proposes a new and considerably more complex wedge model. Among the features of the model are the ability to represent shear compliance of the wedge faces and varying normal and tangential pressure distributions on the faces, as well as explicit modeling of column toe-in and toe-out. The model is implemented using the VAMPIRE® vehicle dynamics package developed by AEA Technology plc. Sample results are presented for a standard metal wedge and a design with a resilient pad on the slope surface. Directions for further developments are proposed.
Frequency Response of a Three-Node Finite Element for Composite Thin and Thick Plates
Authors: Shastry A. V. S. Ravi , Kumar Pramod
Published: April 2008

A shear-locking free isoparametric three-node triangular finite element is considered for the study of frequency response of moderately thick and thin composite plates. The strain displacement relationship is based on Reissner-Mindlin plate theory that accounts for transverse shear deformations into the plate formulation to circumvent the shear locking effect. The element is developed with full integration scheme; hence the element remains kinematically stable. The performance of the element for the case of static load response using the shear correction terms to shear strain components applied to a composite plate has been studied. The natural frequencies and mode shapes in accordance with varying mode numbers, are deduced and the results are compared with the available analytical and finite element solutions in literature.
Pool Boiling Heat Transfer in Saturated Nanofluids
Authors: Kim J. H. , Kim K. H. , You S. M.
Published: April 2008

Experimental investigations were performed to understand the fundamentals of pool boiling heat transfer in nanofluids. The pool boiling curves of water and nanofluids at the pressure of 2.89 psia (Tsat = 60°C) were obtained and compared using a flat square (1 × 1 cm) heater. The tested nanofluids contain aluminum oxide (Al2O3) nanoparticles dispersed in distilled-deionized water. The concentrations of nanofluids range from 0 gram/liter to 0.05 gram/liter. The results show that the boiling heat transfer coefficient is independent of concentrations of nanofluids. Remarkable enhancement (~200%) of CHF was achieved for low concentrations of nanofluids (above 0.01 gram/liter). The boiling parameters, such as bubble size and departure frequency, were measured and analyzed using a 390-μm-diameter platinum wire. The measurement reveals that the size of bubbles increases and the bubble frequency decreases significantly in saturated nanofluids as compared to those in pure saturated water. The surface orientation effects on boiling heat transfer in nanofluids are also investigated. The results show that CHF enhancement of nanofluids is more effective as the boiling surface faces downward.
Momentum Transfer Between Polydisperse Particles in Granular Flow
Authors: Gao D. , Fan R. , Subramaniam S. , Fox R. O. , Hoffman D.
Published: April 2008

We perform Molecular Dynamics (MD) simulations (based on the soft sphere model) of a model granular system consisting of two types of spherical particles differing in size and/or density to characterize particle-particle momentum transfer (solid drag). The velocity difference between two types of particles is specified in the initial conditions, and the evolution of relative mean velocity and the velocity fluctuations in terms of granular temperature are quantified. The dependence of the momentum transfer is studied as a function of volume fraction, size and density ratio of the two types of particles, inelasticity, and friction coefficient. An existing continuum model of particle-particle momentum transfer based on extensions of kinetic theory is compared to the MD simulations. A modified continuum solid drag model is suggested for a limited range of parameters.
Dynamic Crush Behavior of Aluminum 5052-H38 Honeycomb Specimens Under Out-of-Plane Inclined Loads
Authors: Hong Sung-tae , Pan Jwo , Tyan Tau , Prasad Priya
Published: April 2008

The dynamic crush behavior of aluminum 5052-H38 honeycomb specimens under out-of-plane inclined loads is investigated. Honeycomb specimens were designed to minimize the secondary stresses under out-of-plane inclined loads. A test fixture was designed such that inclined loads can be applied in dynamic crush tests. A static linear elastic finite element analysis was performed to understand the stress distributions in honeycomb specimens under inclined loads. The computational results show that the secondary stresses of the specimens are limited to the region near the stress-free boundary. The results of dynamic crush tests indicate that the effects of the impact velocity on the crush strengths are significant. Under dynamic loads, as the impact velocity increases, the crush strengths increase. The trends of the inclined crush strengths for specimens with different in-plane orientation angles as functions of the impact velocity are very similar to that of the pure compressive crush strength. Honeycomb specimens under pure compressive and inclined loads show similar progressive folding mechanisms. The similar trends of the crush strengths as functions of the impact velocity are possibly due to the similar progressive folding mechanisms.
SCREAM’03: A Single Mask Process for High-Q Single Crystal Silicon MEMS
Authors: Zhang Wenhua , Zhang Weibin , Turner Kimberly , Hartwell Peter G.
Published: April 2008

We present a single-mask single-crystal silicon (SCS) process for the fabrication of suspended MicroElectroMechanical devices (MEMS). This is a bulk micro-machining process that uses Deep Reactive Ion Etch (DeepRIE) of a silicon-on-insulator (SOI) substrate with highly doped device layer to fabricate movable single-crystal silicon MEMS structures, which can be electrically actuated without metal deposition. The buried oxide layer is not removed afterwards and no wet process release is involved in the whole process sequence, which makes this process different from others works based on SOI wafer. Several MEMS oscillators have been made using this process. Dynamic behavior is characterized using a laser vibrometer. Quality factor is improved by more than 1 order compared to the same oscillator made using SCREAM process.
Encoder-Less Synchronized Averaging Using Order Tracking and Interpolation
Authors: Tzeng George T.
Published: April 2008

Synchronized averaging is a very useful signal processing technique, in particular, for condition monitoring of rotating machinery. It enhances the signal to noise ratio by attenuating noises that are not repeated from one rotation to the next. Its use, however, is limited due to the costly hardware needed to trigger the sampling at exactly the same angular positions rotation after rotation. This paper describes an improved order tracking technique which employs a Kalman filter to track the instantaneous rotating speed of machinery and an interpolation technique to resample data obtained under constant sampling time interval into data sampled at constant angular increments. Experiments were conducted to validate the proposed algorithm. Comparing the synchronized average obtained by the order tracking algorithm with the true average using encoder triggering, no significant difference can be seen until 3x of meshing frequency. Since the technique only requires band-pass filtered vibration and a once-per-revolution index signal, it is much simpler compared to the existing technique which requires complex and cumbersome hardware to track the rotating speed.
Rapid Maneuvering of a Biologically Inspired Hexapedal Robot
Authors: McClung Arthur J. , Cutkosky Mark R. , Cham Jorge G.
Published: April 2008

In dynamic running hexapods, stable and rapid turns can be achieved by small changes in the nominal configuration of the system used for straight-ahead running. Such changes in configuration, or “shape,” alter the direction of the ground reaction forces and result in a high rate of change in heading and orientation. In this paper, we explore strategies for rapid maneuverability of a hexapedal running robot, taking further inspiration from its exemplar, the cockroach. Through simulation and experiments, we show that a one-parameter control input, or turn factor, can be used to coordinate changes in the multi-dimensional configuration space of the robot for efficient turning up to 4 rad/s. This turn factor is used in the characterization of turning dynamics via system identification techniques.
A Single Cell Study on the Temperature Effects of Electroporation
Authors: Di´az Rube´n , Rubinsky Boris
Published: April 2008

In electroporation, the charging of the cell membrane due to an applied electric field is followed by a localized structural rearrangement of the membrane, which consequently creates pores or aqueous pathways that perforate the membrane. A tremendous increase in ionic and molecular transport through the membrane occurs because of the presence of these aqueous pores. As part of a comprehensive study on the effects of temperature on electroporation of cells, we have designed a micro device capable of integrating single cells into an electronic circuit while controlling the temperature. In the present work, we have studied the effect of temperature on the electroporation of Madin-Darby canine kidney epithelial cells (MDCK) with a micro-electroporation device. It was found that the critical voltage for electropermeabilization was strongly dependent on temperature, increasing by a factor of 2 with decreasing temperature from 37 to 5 °C. Data shows there is a correlation among the viscoelastic properties of the cell membrane and the temperature.
The Use of Frequency Response Functions for Composite Plate Monitoring With Ultrasonic Validations
Authors: Park Gyuhae , Rutherford Amanda C. , Wait Jeannette R. , Nadler Brett R. , Farrar Charles R.
Published: April 2008

In this study, frequency response functions (FRF) measured by piezoelectric Macro-Fiber Composites (MFC) are used to detect invisible delamination in a composite plate. The plate is impacted to seed damage in the form of fiber delamination. Then, the active-sensing system exerts an excitation into the plate, and measures the subsequent responses. FRF and damage indicator features are derived from the measured signals and used to assess the condition of the plate. Validation of the delamination is completed using an ultrasonic scan method. The effective area of observed damage is well correlated to the damage indicator feature.
Identification of Structural Systems With Limited Number of Sensors and Actuators
Authors: Yu Jun , Imbimbo Maura , Betti Raimondo
Published: April 2008

The common assumption in the so-called linear inverse vibration problem, which provides the mass/stiffness/damping matrices of second order dynamic models, is the availability of a full set of sensors and actuators. In “reduced-order” problems (with limited number of instrumentation), only the components of the eigenvector matrix regarding the measured degrees of freedom can be successfully identified while nothing can be said about the components connected to the unmeasured degrees of freedom. This paper presents a recently developed “reduced-order” model and expands such a model to a “full-order” one that is quite useful in damage detection. The five representative categories of “reduced-order” problems, defined by considering different types of geometrical conditions, are analyzed and a discussion on their solution space has been performed. The effectiveness and robustness of this approach is shown by means of a numerical example.
Experimental Characterization of Anode Heating Due to Electron Emission From an Individual Carbon Nanotube
Authors: Westover T. L. , Fisher T. S. , Chopra V. , Pfefferkorn F. E.
Published: April 2008

Electron field emission is the process by which electrons tunnel from a cathode to an anode, usually through vacuum, by the application of a large voltage bias. Field-emission devices find applications in flat panel displays, electrical circuit breakers, and power diodes. A significant amount of heat can be transferred to the anode from high-energy electrons as they impact the anode surface. This study investigates the heating of a thin, disc-shaped steel anode by field-emitted electrons from a single carbon nanotube. Experiments have demonstrated a temperature rise of more than 11.0 C at the anode center at an energy deposition rate of 16 mW. A finite-difference model is employed to predict the steady-state anode temperature profile resulting from electron field emission, and this profile is compared to that obtained from measurements taken with an infrared camera. The comparison yields information regarding the diameter of the electron beam as it strikes the anode. The paper also discusses significant experimental challenges, which include attaching individual nanotubes on a tungsten needle to withstand the applied electric field and obtaining consistent results during repeated testing.
Uniqueness of Solutions for the Identification of Linear Reduced Order Structural Systems
Authors: Franco Guillermo , Yu Jun , Betti Raimondo
Published: April 2008

The problem of identification of structural systems is an inverse problem that uses input (say force excitation) and output information (accelerations, for instance) to obtain an optimal model to describe the system’s behavior. Since a full instrumentation setup is expensive, situations usually arise where only partial measurements are available. Uniqueness of the solution in these circumstances might not be guaranteed. This paper analyzes the minimum number of measurements required to ensure that only one solution exists for the identification problem of mass, damping and stiffness distributions of shear-type N degrees of freedom linear structures. Three typical configurations of measurements are studied with two distinct theoretical approaches, one based on classical polynomial theory, the other based on reduced order model theory. Both these approaches lead to the conclusion that only one input and one or two output measurements are sufficient to guarantee uniqueness of identification, depending on the selected location of the input measurement. Additionally, the identification of a 3DOF system is carried out analytically with the usage of Sylvester’s Dyalitic Elimination to show that fewer measurements than the ones proposed lead to non-unique identification. This fact is also illustrated with the usage of a recently developed optimization technique, with which convergence to the different solutions is observed depending on the initial estimate used.
Wire Deactivation Methodology for Inverse Dynamics of Wire-Actuated Redundant Manipulators
Authors: Kamalzadeh Amin , Notash Leila
Published: April 2008

Wire-actuated robot manipulators are generally lighter than other manipulators as actuated wires are used instead of joint actuators. The inverse dynamic modeling of these manipulators is complicated by the existence of multiple kinematic constraints as well as redundancy in actuation. In wire-actuated parallel manipulators with a constraining linkage and in tendon-driven serial manipulators, wires are used to control the joints. In these manipulators, each wire can provide a torque/force on a link about/along its revolute/prismatic passive joint in one direction, as wires only act in tension. Using one wire for each link sometimes does not fully constrain the motion of the link about/along its passive joint. Therefore, a second wire is attached to some links in a “counterbalance” configuration; i.e., the second wire can provide a “complementary” torque/force in the opposite direction of the torque/force produced by the first wire on the link about/along its passive joint. Depending on the end effector trajectory and external force at each instant, one of the mentioned two wires provides the desired direction of torque/force and the other, “counteracting wire,” imposes a “counteracting” torque/force on the link about/along its passive joint. Using more actuators than degrees of freedom (DOF) in the manipulator causes redundancy in actuation, which means that for a unique end effector trajectory and external force, inverse dynamic results (actuator torques/forces) have infinite solutions within a null space of actuator torques/forces. Obtaining a unique result within the null space requires several considerations, such as avoiding negative tensions in wires and decreasing the actuator torques/forces. The purpose of this article is to find a methodology to limit the infinite inverse dynamic solutions to one while the negative wire tensions are avoided and actuator torques/forces are relatively decreased. As explained in this article, by reducing the counteracting wire tensions, other actuator torques/forces are decreased, because a portion of other actuator torques/forces neutralizes the tensions of counteracting wires. A methodology is developed to detect the counteracting wires in real-time and to present the corresponding tensions to a low positive value; i.e., the counteracting wires are “deactivated.” The proposed methodology can be implemented in the inverse dynamic modeling of wire-actuated parallel manipulators with a constraining linkage and tendon-driven serial manipulators via using the Lagrangian method. This methodology can be used to provide optimum actuator torques/forces and avoid negative tensions in actuated wires. The methodology is implemented in the inverse dynamic modeling of a 4-DOF wire-actuated manipulator where there is one degree of actuation redundancy. In the simulation results, the inverse dynamic model based on the proposed methodology is observed to be quite robust in terms of avoiding negative wire tensions by deactivating the right actuated wire.
Transport in a Methanol Steam Reformer as the Fuel Processor for Fuel Cell Systems
Authors: Park Hyung Gyu , Lee Ming-Tsang , Hsu Frank K. , Grigoropoulos Costas P. , Greif Ralph , Lin Chun-Hung
Published: April 2008

An experimental and analytical study of the reacting flow in a catalytic reactor is presented. Methanol-steam reforming may be utilized in the fuel processing system for hydrogen fuel cells. Understanding the flow and transport phenomena as well as the reaction mechanisms is essential for improving the efficiency of the reforming process as well as the quality of the processed fuel. Utilizing the results obtained, optimized conditions for fuel processing are discussed.
An Integrated Environment for the Design and Control of Deadlock-Free Flexible Manufacturing Cells
Authors: Yuan Chengyin , Ferreira Placid
Published: April 2008

At the enterprise level, manufacturing organizations are faced with accelerating technological cycles, global competition and an increasingly mobile work force. The flexibility of the enterprise and its ability to respond to various customer demands governs the competitiveness of the enterprise to the changes in its market and in the society in which it operates. It has been recognized for many years that flexibility on the enterprise floor can always be achieved if the resulting cost of product and process changeovers and its operations are not considered. However, with the increasing competitive pressures on today’s manufacturing enterprise, a flexible-manufacturing environment must be achieved at relatively low cost and high work-force productivity while maintaining a competitive advantage. To accomplish this goal, the manufacturing enterprise must be able to be reconfigured and verified with an increased level of automation that is scalable and flexible to meet diverse product demands quickly and economically. In this paper, we will introduce the recent research work on developing an integrated rapid prototyping environment, EMBench [22, 23], which can provide design, control configuration, simulation and deployment services for flexible manufacturing systems. This rapid prototyping environment has its own user-friendly GUI (Graphical User Interface) that allows user to issue various commands to the controller at different layers, from the simple joint servo to the complex manufacturing cell. In this paper, we also propose the implementation diagram for the controller of manufacturing cells that consists of scheduler, dispatcher, real-time database and structural control policy. All these internal components are responsible for storing system configuration, optimizing processing plan, releasing appropriate command, etc. We also present the idea of cell model and explore its characteristics and behaviors as well as the resource and workstation models. All above modules and architecture are developed using IEC-61499 function blocks that support scalable expansion and modular design. To demonstrate our theoretical achievements, we have developed various IEC-61499 function blocks to integrate various resources on the enterprise shop floor and achieve flexibility at a low cost. This software environment facilitates a modular, component-based mechanical and control design, simulating and prototyping tool for shop floor control.
Magnetorheological (MR) Jet Finishing Technology
Authors: Kordonski William I. , Shorey Aric B. , Tricard Marc
Published: April 2008

Conformal (or freeform) and steep concave optics are important classes of optics that are difficult to finish using conventional techniques due to mechanical interferences and steep local slopes. One suitable way to polish these classes of optics is by using a jet of abrasive/fluid mixture. In doing so, the energy required for polishing may be supplied by the radial spread of a liquid jet, which impinges a surface to be polished. Such fluid flow may generate sufficient surface shear stress to provide material removal in the regime of chemical mechanical polishing. Once translated into a polishing technique, this unique tool may resolve a challenging problem of finishing steep concave surfaces and cavities. A fundamental property of a fluid jet is that it begins to lose its coherence as the jet exits a nozzle. This is due to a combination of abruptly imposed longitudinal and lateral pressure gradients, surface tension forces, and aerodynamic disturbance. This results in instability of the flow over the impact zone and consequently polishing spot instability. To be utilized in deterministic high precision finishing of remote objects, a stable, relatively high-speed, low viscosity fluid jet, which remains collimated and coherent before it impinges the surface to be polished, is required. A method of jet stabilization has been proposed, developed and demonstrated whereby the round jet of magnetorheological fluid is magnetized by an axial magnetic field when it flows out of the nozzle. It has been experimentally shown that a magnetically stabilized round jet of MR polishing fluid generates a reproducible material removal function (polishing spot) at a distance of several tens of centimeters from the nozzle. In doing so, the interferometrically derived distribution of material removal for an axisymmetric MR Jet, which impinges normal to a plane glass surface, coincides well with the radial distribution of rate of work calculated using computational fluid dynamics (CFD) modeling. Polishing results support the assertion that the MR Jet finishing process may produce high precision surfaces on glasses and single crystals. The technology is most attractive for the finishing of complex shapes like freeform optics, steep concaves and cavities.
A New Anisotropic Damage Model for Ceramic Matrix Composites
Authors: Cazacu Oana , Soare Stefan
Published: April 2008

Within the framework of irreversible thermodynamics, a new general constitutive model for describing damage and its effect on the overall properties of anisotropic solids is proposed. The ability of the model to describe the overall stress-strain response as well as the loss of symmetry resulting from the interaction between initial and damage-induced anisotropy in a brittle matrix composite is demonstrated.
Bacterial Flagellar Motors as Microfluidic Actuators
Authors: Pooran Ryan , Al-Fandi Mohamed , Tung Steve , Kim Jin-Woo , Kotagi Nalini , Lee Ju Seok
Published: April 2008

Microfluidic actuators are extremely important components of microfluidic systems used in biological, chemical and biochemical analyses. We are in the process of developing hybrid microsystem devices that utilize flagellar motors in tethered Escherichia coli (E.coli) cells as actuators. In this study we describe the robustness of the flagellar motor actuators. To examine the robustness of the actuators we observe the behavior of the cells when exposed to a hydrodynamic load. With this method we are able to determine the torque generated by the flagellar motor and the adhesion force of the flagellar filament to the substrate. Using hydrodynamic loading we are also able to synchronize the rotation of multiple cells. Finally, we present data which represents the lifetime of the flagellar motor actuators.
Invariant Theory for Dispersed Transverse Isotropy: An Efficient Means for Modeling Fiber Splay
Authors: Einstein D. R. , Freed A. D. , Vesley I.
Published: April 2008

Microstructual studies suggest that in some tissues, collagen fibers are approximately normally distributed about a mean preferred fiber direction. Structural constitutive equations that account for this dispersion of fibers have been shown to capture the mechanical complexity of these tissues quite well. However, such descriptions are computationally cumbersome for two-dimensional fiber distributions, let alone for fully three dimensional fiber populations. We have developed a new constitutive law for such tissues, based on a novel invariant theory for dispersed transverse isotropy. The model is polyconvex and fits biaxial data for aortic valve tissue as accurately as the standard structural model. Modification of the fiber stress-strain law requires no re-formulation of the constitutive tangent matrix, making the model flexible for different types of soft-tissues. Most importantly, the model is computationally expedient in a finite element analysis.
A Study of Combined Braking and Cornering Performance of a Transit Bus Using Validated Computer Simulation
Authors: Ayalew Beshahwired , Yu Nan , Muthiah Saravanan , Kulakowski Bohdan T.
Published: April 2008

In this paper, results from actual braking tests of a low-floor, two-axle transit bus are used to validate a dynamic model of the bus. The model, developed using the commercial multibody dynamic system simulation software ADAMS, is an 18 DOF full-bus model of a transit bus equipped with air suspension and pneumatic brakes with Anti-lock Braking System (ABS). An ABS algorithm was implemented in MATLAB/Simulink and linked to the ADAMS full-bus model using co-simulations. The validated full-bus model was then used to study lateral and roll stability of a transit bus during combined braking and cornering maneuvers on various road surface conditions. Numerical experiments were also conducted to study the effects of variations in total load on the dynamics of the bus during braking while cornering. The results indicate the danger of yaw-instability on slippery surfaces. Increasing the total load reduced the lateral acceleration of the bus with a less pronounced effect on the roll angle.
High-Strain Ionomeric-Ionic Liquid Composites via Electrode Tailoring
Authors: Akle Barbar J. , Bennett Mathew D. , Leo Donald J.
Published: April 2008

Ionomeric polymers are a class of electromechanical transducer consisting of an ionomeric substrate with metal-plated electrodes. Application of a low voltage (< 5 V) across the thickness of the membrane produces controllable strain. The advantage of ionomeric polymers compared to other types of electromechanical transducers (e.g. piezoelectric polymers) is low-voltage operation, high strain capability, and high sensitivity in charge mode. Two of the primary limitations of ionomeric polymers for electromechanical transducers are unstable operation in air and solvent breakdown at low voltage. This work focuses on overcoming these limitations through the development of an ionic liquid-ionomeric composite with a tailored electrode composition that maximizes strain output. It is becoming clear that charge accumulation at the polymer-electrode interface is the key to producing high strain in ionomeric polymer transducers. In this work we combine a previously developed process for incorporating ionic liquids into ionomer membranes with a new method for tailoring the electrode composition. The electrode composition is studied as a function of the surface-to-volume ratio and conductivity of the metal particulates. Results demonstrate that the surface-to-volume ratio of the metal particulate is critical to increasing the capacitance of the transducer. Increased conductivity of the metal particulates produces improved response at higher frequencies (> 10 Hz) but this effect is small compared to the increase in strain produced by maximizing the capacitance. Increasing capacitance produces a transducer that is able to achieve > 2% strain at voltage levels of +/- 3 V.
Impact Tests of Crash Energy Management Passenger Rail Cars: Analysis and Structural Measurements
Authors: Jacobsen Karina , Tyrell David , Perlman Benjamin
Published: April 2008

Two full-scale impact tests were conducted to measure the crashworthiness performance of Crash Energy Management (CEM) passenger rail cars. On December 3, 2003 a single car impacted a fixed barrier at approximately 35 mph and on February 26, 2004, two-coupled passenger cars impacted a fixed barrier at approximately 29 mph. Coach cars retrofitted with CEM end structures, which are designed to crush in a controlled manner were used in the test. These test vehicles were instrumented with accelerometers, string potentiometers, and strain gages to measure the gross motions of each car body in three dimensions, the deformation of specific structural components, and the force-crush characteristic of the CEM end structure. Collision dynamics models were developed to predict the gross motions of the test vehicle. Crush estimates as a function of test speed were used to guide test conditions. This paper describes the results of the CEM single-car and two-car tests and provides results of the structural test. The single-car test demonstrated that the CEM design successfully prevented intrusion into the occupied volume, under similar conditions as the conventional test. During both CEM tests, the leading passenger car crushed approximately three feet, preserving the occupant compartment. In the two-car test, energy dissipation was transferred to the coupled interface, with crush totaling two feet between the two CEM end structures. The pushback of the couplers kept the cars in-line, limiting the vertical and lateral accelerations. In both the conventional tests there was intrusion into the occupant compartment. In the conventional two-car test sawtooth lateral buckling occurred at the coupled connection. Overall, the test results and model show close agreement of the gross motions. The measurements made from both tests demonstrate that the CEM design has improved crashworthiness performance over the conventional design.
Radiative Absorption in a Hollow Cylinder: Application to Microstructured Optical Fiber Fabrication
Authors: Tian Weixue , Chu Wilson K. S.
Published: April 2008

Radiation absorption of an infinitely long hollow cylinder with Fresnel boundary is studied using the ray tracing method. Since the radiative heat transfer is the dominant heat transfer mode in optical fiber drawing, the current radiative transfer model can provide insights into physical processes for microstructured optical fiber fabrication. Effects of refractive index, optical thickness and geometry on radiative heat transfer are studied. The results of this study can also serve as benchmark solutions for radiative heat transfer for other methods, such as the finite volume method and the discrete ordinates method for participating media with Fresnel boundary.