bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Differential Scanning Calorimetry and X-Ray Diffraction as Experimental Tools to Understand How Nucleating Agent Concentration Affects Supercooling in Microencapsulated Phase Change Materials
Authors: Alvarado Jorge L. , Marsh Charles , Sohn Chang , Newell Ty , Johar Jasmeet Singh
Published: April 2008

In this paper, a description and explanation of the experimental techniques used to understand and quantify supercooling will be presented, including differential scanning calorimetry and x-ray diffraction. Differential scanning calorimetry experimental results indicate that supercooling in microencapsulated n-Tetradecane can be suppressed significantly when 4% to 6% of a homologous material is used as nucleating agent. X-ray diffraction experimental results elucidate how nucleating agent concentration affects the morphology of the phase change material after solidification. Both experimental techniques in unison prove to be valuable experimental tools and provide a better understanding of how inclusion of nucleating agents affects the solidification process. Quantitative characterization of microencapsulated n-Tetradecane thermal properties is also presented including latent heat of fusion and melting point data.
Fabrication of Micromachined Mold Masters for 3-D, High-Aspect-Ratio Cell Culturing Scaffolds
Authors: Zhao Yanzhu , Wu Xiaosong , Yoon Yong-Kyu , Park Jung-Hwan , Kennedy Stephen J. , Schwartz Zvi , Boyan Barbara D. , Allen Mark G.
Published: April 2008

In this paper, three approaches to micromachined mold master structures for molding of a wafer-scale bone culturing platform are compared and contrasted. The processes investigated are a silicon deep-reactive ion etching (DRIE) process, an SU-8/polydimethylsiloxane(PDMS) process, and a multi-step SU-8 process. Upon comparison of the advantages and disadvantages of each approach, a wafer-scale implementation of bone cell culturing substrates is successfully demonstrated using the two-step SU-8 process, and successful duplication of hydrogels based on these molds is demonstrated.
Creep Behavior of Nextel™ 610/Monazite/Alumina Composite at Elevated Temperatures
Authors: Ruggles-Wrenn M. B. , Musil S. S. , Mall S. , Keller K. A.
Published: April 2008

Aerospace components require structural materials that have superior mechanical properties and can withstand severe environmental conditions, such as ultra-high temperature, high pressure, or water vapor. Ceramic-matrix composites (CMCs), capable of maintaining excellent strength and fracture toughness at high temperatures are prime candidate materials for aerospace applications. This research effort investigates creep behavior of N610/LaPO4/Al2O3 composite consisting of a porous alumina matrix reinforced with Nextel 610 fibers coated with monazite in a symmetric cross-ply (0°/90°/0°/90°)s orientation. Tensile creep was examined at temperatures in the 900-1100°C range for creep stresses ranging from 40 to 150 MPa. At 900°C primary and secondary creep regimes were observed. At temperatures above 900°C, the composite exhibited primary, secondary and tertiary creep. Minimum creep rate was reached in all tests. Creep rates accelerated with increasing temperature and creep stress. Creep run-out was defined as 100 h at creep stress. At 900°C the run-out stress was 120 MPa. Monazite coating resulted in improved creep resistance at 900°C. Creep performance deteriorated rapidly at temperatures above 900°C.
Parameter Effect and Sensitivity Analyses of Fixturing Dynamic Stability in Machining
Authors: Deng Haiyan , Melkote Shreyes N.
Published: April 2008

The dynamic stability of a workpiece in a fixture is a critical indicator of machining fixture performance and is affected by a variety of factors. This paper presents a parameter effect analysis of fixturing dynamic stability in machining based on a previously developed stability model. The effects of four major factors - spindle speed, static coefficient of friction, fixture layout, and clamping forces - on the dynamic stability of a fixtured workpiece are investigated and the predominant effects are identified. Further, the effect of imprecision of the static coefficient of friction on the fixturing dynamic stability is examined. A numerical example is presented and insightful interpretations are given.
Combined Mechanical Engineering Materials Lecture and Mechanics of Materials Laboratory: Cross-Disciplinary Teaching
Authors: Nowak Michael D.
Published: April 2008

We have developed a course combining a Mechanical Engineering Materials Laboratory with a Materials Science lecture for a small combined population of undergraduate Mechanical and Biomedical Engineering students. By judicious selection of topic order, we have been able to utilize one lecture and one laboratory for both Mechanical and Biomedical Engineering students (with limited splitting of groups). The primary reasons for combining the Mechanical and Biomedical students are to reduce faculty load and required resources in a small university. For schools with medium or small Mechanical and Biomedical Engineering programs, class sizes could be improved if they could include other populations. The heterogeneous populations also aid in teaching students that the same engineering techniques are useful in more than a single engineering realm. The laboratory sections begin with the issues common to designing and evaluating mechanical testing, followed by tensile, shear, and torsion evaluation of metals. To introduce composite materials, wood and cement are evaluated. While the Mechanical Engineering students are evaluating impact and strain gauges, the Biomedical Engineering students are performing tensile studies of soft tissues, and compression of long bones. The basic materials lectures (beginning at the atomic level) are in common with both Mechanical and Biomedical student populations, until specific topics such as human body materials are discussed. Three quarters of the term is thus taught on a joint basis, and three or four lectures are split. Basic metal, plastic and wood behavior is common to both groups.
Parylene Micro-Membrane Capacitive Bio/Chemical Sensor
Authors: Satyanarayana Srinath , McCormick Daniel T. , Majumdar Arunava
Published: April 2008

Micro-fabricated sensor arrays have immense potential to become an accurate, quantitative and high-throughput analysis tool for chemical and biological sensing. In the recent years, several microcantilever sensors using surface stress transduction principle have been developed to address this need [1]. However, the design of these sensors is limited by the high mechanical rigidity of the silicon based materials used in fabrication. The cantilever geometry also has limitations in liquid media, which is common in biological applications, because of non-specific adsorption on the back side of the cantilever. The optical detection methods used for measuring the microcantilever deflection are also not amenable to miniaturization. In this paper we demonstrate a novel parylene micro-membrane sensor that exploits the low mechanical stiffness of polymers and addresses the above issues. The concept of a polymer micro-membrane surface stress sensor was first presented by the authors using parylene as the membrane material [2] and later by Rodriguez et al using PDMS membranes [3]. The salient features of the sensor are that it: (i) is label free; (ii) is a universal platform - suitable for both chemical and biological sensing, (iii) uses electronic (capacitive detection) readout; (iv) has integrated microfluidics for addressing individual sensors on the chip (v) is capable of handling both liquid and gas samples; (vi) is made using standard low temperature microfabrication processes (< 120 C); and (vii) can readily be scaled and multiplexed.
Band Gap Formation in Composite Models With Quasi-Random Fiber Arrangements
Authors: Patil Shashidhar , Cai Liang-Wu
Published: April 2008

Large-scale deterministic simulations are performed in order to observe the band gap formation in composite models having quasi-random fiber arrangements. Composite plates are modeled in two-dimensions with various unidirectional fiber arrangements. The quasi-random fiber arrangements can be qualified as essentially regular with slight randomness. Simulation results are compared with the corresponding case of ideally regular fiber arrangement. The most interesting observation is that the slight randomness in the fiber arrangements enhances the band gap phenomenon by introducing a few secondary band gaps adjacent to the primary band gap. An attempt is made to relate the band gap characteristics to the statistical parameters of fiber arrangements.
A Case-Based Reasoning Approach to Robot Selection
Authors: Chang Guanghsu A. , Sims J. Paul
Published: April 2008

Robot selection is one of critical decisions in the design of robotic workcells. Over the last ten years, many Case-Based Reasoning (CBR) systems have been developed to solve decision making problems successfully. We propose to develop three sort systems: browsing systems, preference-based selection organizers, and alternative suggestion agents. All four stages of the CBR cycle are designed to assist robotic application designers to go through robot selection and decision-making. A case-based reasoning approach is employed to solve new robot selection decision problems by adapting solutions that were used to solve previous robot selection problems. In this study, CBR has shown that it has several advantages over other techniques. The results of this study will help robot workcell designers to develop a more efficient and effective method to select robots for specific robot applications.
Reliability of Carbon Coated Optical Fibers
Authors: Chakravarthy Srinath S. , Chiu Wilson K. S.
Published: April 2008

The inert strength of carbon coated optical fibers has been observed to be less than that standard optical fibers. The fracture toughness of the carbon film and the residual stress in the film play a critical role in determining the strength of the carbon coated optical fibers. The fracture toughness and the residual stress in the film were measured for a variety of deposition conditions. A recently developed fracture mechanics model was used to predict the failure of carbon coated optical fibers. Model based strength predictions were compared to experimentally measured values. The prediction was found to be in good agreement with the measured values.
Early Damage Stress State MMM Testing
Authors: Xing Hai Yan , Xu Min Qiang , Zhang Jia Zhong
Published: April 2008

The stress state testing and evaluation is the major concern in early damage testing. The metal magnetic memory (MMM) testing, based on ferromagnetic theory, is a new NDE technology that can find the most serious stress concentration zones, microscopic defect, etc. However, there is no quantitative analysis standard in engineering practice. This paper is to find out MMM critical signal characteristics of early damage to offer a foundation data for MMM quantitative testing. The relation between stress distribution and magnetic memory signal has been studied by experiments. Two different states of stress, including one-direction tensile stress state and two-direction bend stress state, were created. The critical magnetic characteristics are given in zones of stress concentration, which can serve as a rule for testing early damage. The result of metallographic examination proves the validity of MMM early damage testing.
Correlation Between the Strain on the Printed Circuit Board and the Stress in Chips for the Failure Prediction of Passive Components
Authors: Lau Dennis , Lee S. W. Ricky
Published: April 2008

Due to the demand for miniaturization of microelectronic devices, the density of packaging has become higher and higher. Also, the sizes of components have become smaller and smaller. In addition to advanced active components such as chip scale packages (CSPs) and flip chips (FCs), mini sized passive components such as chip capacitors and resistors are also important elements for high density packaging. It is quite common to see dozens up to hundreds of passive components on printed circuit boards (PCBs). Both active and passive components contribute to the function (and also malfunction) of electronic systems. However, the reliability issues of passive components are often overlooked because they are relatively small in size and cheap in cost. In view of the fact that “small components could lead to big problems”, the present study is conducted to evaluate the threat to passive components assembled on PCBs under a specific type of mechanical loading. Because of the nature of mass production, microelectronic devices are always manufactured in a batch mode. It is quite often that several PCBs are linked together during the surface mount assembly process. Even if the PCB is a stand-alone unit, extra peripheral frames or tie bars are needed for tooling and fixture. After the board level assembly, a depaneling process is usually required to singulate individual PCBs or to remove the tooling frames for the system level assembly. Some depaneling processes may be automated with precision control. However, it is not unusual for operators in the factory to perform manual depaneling. During this process, the PCB is subjected to mechanical bending and the curvature of the bent PCB may be big enough to damage small passive components. The present study is intended to establish a model for the failure prediction of passive components under depaneling load condition. Computational stress analysis is performed with a 3D finite element model. The emphasis is placed on finding the correlation between the bending strain on the PCB (which is an index of the local curvature of the bent PCB) and the bending stress in the passive components (which is the reason to crack capacitors/resistors). It is observed that such a relationship can be established. With this model, the cracking of passive components may be predicted under the depaneling load condition. The understanding of this potential threat can be turned into a design rule to avoid mounting passive components in the “high risk” area on the PCB. As a result, the objective of “design for reliability” (DFR) can be achieved. The details of the aforementioned model and the results of stress analysis will be presented in this paper.
A Novel Nanomaterial Based Electrochemical Sensor for Free Radical Detection
Authors: Patil Swanand , Mehta Anjum , Bang Hyoungseok , Cho Hyoung J. , Seal Sudipta
Published: April 2008

Hydrogen peroxide (H2O2) is not only a product of the reactions catalyzed by a large number of highly selective oxidases but also an essential mediator in food, pharmaceutical and environmental analysis. Therefore its determination is of paramount importance in many areas in chemical, biological and clinical fields. Most H2O2 biosensors developed till date are based on enzymes and proteins which have a limited sensor life. Moreover, complex procedures are followed for sensor fabrication. Therefore an inorganic material based sensor with a simple design and longer shelf-life is highly desirable. In this work, the development of a novel cerium oxide nanomaterial based electrochemical sensor for the measurement of hydrogen peroxide is described. This has direct ramifications in the development of sensors for other superoxide radicals.
Experimental Investigation of the Effect of Reflow Cooling Rate on the IMC Growth of SAC Lead-Free Solder Alloy
Authors: Song Fubin , Lee S. W. Ricky
Published: April 2008

The present research is conducted to investigate a critical issue for Lead-free solder alloy. Near-ternary eutectic Sn-Ag-Cu alloys have been studied since they are the leading Lead-free candidate solders for various applications. There are three main phases in the near-ternary eutectic alloys: β-Sn rich phase, Ag3Sn and Cu6Sn5. Cooling rate is an important processing factor that affects the microstructure of these alloys and then significantly influences mechanical behavior of the Sn-Ag-Cu solder joints. It is demonstrated that the amount and size of large Ag3Sn plates increase with decreasing of the cooling rate. When large Ag3Sn plates present in the solder joints at the lower cooling rate, they may affect the mechanical integrity of the joints by providing a crack initialization during the mechanical testing under room-temperature condition. In the present paper, the effects of cooling rate on the microstructure and mechanical properties are studied on Sn-3.8Ag-0.7Cu solder ball, including shear strength and ball pull test. There are two kinds of fracture mode for Ag3Sn plates preformed mechanical loading in room-temperature condition. One is brittle fracture inside Ag3Sn plate itself; the other is interfacial fracture of Ag3Sn plates and the IMC layer. Moreover, the fractures of large Ag3Sn plates induce the decrease of mechanical properties on Sn-3.8Ag-0.7Cu solder ball. The critical cooling rate of large Ag3Sn plate formation is also investigated.
Elastic Stress and Magnetic Field Concentration Near the Vertex of a Soft-Ferromagnetic 2-D Compound Wedge
Authors: Hasanyan Davresh , Qin Zhanming , Librescu Liviu
Published: April 2008

The problem of the elastic stress and induced magnetic field concentration near the vertex of a compound wedge is modeled and investigated. The wedge is made of two isotropic dielectric soft-ferromagnetic materials and is immersed in a static magnetic field. By using eigenfunction series expansion technique, the components of the magnetoelastic stresses and the disturbed magnetic field near the vertex are determined. It is shown that in that region the magnetic permeability and the applied magnetic field have a strong influence on the elastic and Maxwell stresses concentration. The results are instrumental toward actively controlling the stress concentration intensity via the applied magnetic field.
Design and Simulation of Computer Business Model for Primary Processing of Hardwood Material
Authors: Padma Sudheer K. , Ragsdell Kenneth M. , Sickler Robert A.
Published: April 2008

Computer business model of hardwood production gives the user an opportunity to examine different ways and provide the capability of executing scenarios using alternative activities and process flow paths. This paper illustrates the design of business model based on which the simulation will be built. It will be able to simulate the effect of variables in each process and provide the output in terms of cost, quality and quantity of timber products produced at the end of primary hardwood processing. The simulation will act as a powerful decision making tool and be user friendly. It will be built with the combination of Visual Basic.NET and Microsoft Excel. It will provide cost and revenue estimates, identifies process issues and will have the capability to rapidly react to changing markets. The simulation will also be able to study the viability of capturing more product value and reducing production cost.
Modeling and Simulation of a Full Vehicle With Parametric and External Uncertainties
Authors: Li Lin , Sandu Corina , Sandu Adrian
Published: April 2008

This paper presents the mathematical development of and simulation results for a full vehicle model with parametric uncertainties operating over unprepared terrain. The vehicle is modeled as a rigid multi-body dynamic system, consisting of chassis and four suspension and tire subsystems. The vehicle parameters considered uncertain are the suspension damping and the tire stiffness. The terrain profile is also modeled as a stochastic function. The uncertainties are explicitly represented using polynomial chaos decompositions. The computational technique presented in this study is more efficient than the traditional Monte Carlo approach, in modeling nonlinear multi-body dynamic systems with uncertainties. The numerical results presented here are very promising. The general computational tools discussed in this paper can be applied directly to any area that involves multi-body dynamic models, e.g., robotics, autonomous mechanical systems, actuator dynamics, and automatic control of systems with uncertainties.
Investigation of a Framework for Collaborative Activities Across Heterogeneous Engineering Domains
Authors: Gobinath N. , Cecil J.
Published: April 2008

This paper describes the functions underlying the creation of a collaborative framework to support robust information exchange across heterogeneous engineering domains. The application context relates to nano manipulation of particles such as proteins; the initial findings relating to distributed accomplishment of target activities in this identified context will be elaborated in this paper. In the scenario being considered, the potential project partners who possess skills and resources related to nano tube design, synthesis, manipulation plan, and simulation are identified from a service directory to form a Virtual Enterprise, with which the final target physical manipulation is formulated. In the proposed framework, the user specifications are used by various planning activities and a detailed top level plan is generated, which is represented by , where NTDS (Nano Tube Design Specification) is a representation of the design attributes of a carbon nano tube, NTSS (Nano Tube Synthesis Specification) is a representation that describes the synthesis of nano tube depending upon the design specification, MPS (Manipulation Plan Specification) is a representation which allows to formulate a nano manipulation plan according to user specification, and SS (Simulation Specification) is a representation that allows to generate various test cases to evaluate the nanomanipulator and the associated manipulation plan. The proposed framework is composed of an enterprise level Planning Manager (which generates a detailed top level plan from the user specification), a Design Coordinator (that identifies and evaluates the candidate design companies to find a potential design that can be used for a target nano manipulation tasks), a Synthesis/Manufacturing Coordinator (which focuses on identifying candidate partners and resources capable of manufacturing a specified nano manipulator). In the modeled context, this manipulator is a Nano tube attached to the tip of Atomic Force Microscope (AFM) probe; a Manipulation Plan Coordinator focuses on identifying candidate manipulation plan generators, and a Simulation coordinator deals with identifying candidate simulation tool vendors who provide services to evaluate nano tube and nano manipulation plan. The framework is proposed with scalability in mind so that new modules can be support a ‘plug and play’ type of integration in depending on the customer requirements.
Modular System for Teaching Kinematics Control of Robot Manipulators
Authors: Rodriguez Carlos F. , Zarama Carlos A.
Published: April 2008

One of the main drawbacks for teaching kinematics of robot manipulators is the cost of the experimental platform, which has to be composed by robot manipulators of different structures. In this work, a modular system for experimentation of manipulators kinematics is presented. The system consists of rotational and translational modules. Each module is a robotic link with one controlled degree of freedom. The modules can be linked together by a simple fixture, such that, the actuator of a module is attached to a fixed point of the previous one, forming the open chain structure. Up to three modules can be chained together, producing a 3 DOF manipulator. The appropriate electronics were developed for control and communication of the modules with a computer, via the serial or the USB port. A software program, with basic synchronized control capabilities, completes the system, enabling the execution of joint trajectories. The system is complemented with additional modules for construction of sub-actuated robots.
Electric Motors Coupled to Hydraulic Motors as Actuators for Hydraulic Hardware-in-the-Loop Simulation
Authors: Driscoll Scott , Huggins James D. , Book Wayne J.
Published: April 2008

Hardware-in-the-Loop (HIL) Simulation enables testing of an actual physical component of a system under a variety of conditions without the expense of full scale testing. In hydraulic systems, flows or pressures that interface with the component in question are controlled by a computer running a simulation designed to emulate a complete system under real operating conditions. Typically, servo valves are used as actuators to control the flows or pressures. This paper investigates the use of electric servo-motors coupled to hydraulic gear motors as alternative actuators, and discusses some of the advantages and disadvantages that motors have in comparison to valves. A demonstration HIL simulation involving a mobile proportional flow control valve attached to an emulated backhoe is described, and results are compared to data from a real backhoe.
Characterizing the Dynamics of 3-D Elastic Nonlinear Continua Using the Method of Proper Orthogonal Decompositions
Authors: Georgiou Ioannis , Servis Dimitris
Published: April 2008

A novel and systematic way is presented to characterize the modal structure of the free dynamics of three-dimensional elastic continua. In particular, the method of Proper Orthogonal Decomposition (POD) for multi-field dynamics is applied to analyze the dynamics of prisms and moderately thick beams. A nonlinear finite element model is used to compute accurate approximations to free motions which in turn are processed by POD. The extension of POD to analyze the dynamics of three-dimensional elastic continua, which are multi-field coupled dynamical system, is carried out by vector and matrix quantization of the finite element dynamics. An important outcome of this study is the fact that POD provides the means to systematically identify the shapes of nonlinear normal modes of vibration of three-dimensional structures from high resolution finite element simulations.
Optimization of Design and Operational Parameters Using Genetic Algorithm for a Spark Ignition Engine With CNG/H2 Mixtures
Authors: Anand G. , Balamurugan R.
Published: April 2008

The present contribution describes the potential of using gaseous fuels like Hythane (CNG/H2 mixtures) as a spark ignition (SI) engine fuel. Genetic Algorithm (GA) is used to optimize the design and operational parameters of a CNG/H2 fueled spark ignition engine for maximizing the engine efficiency subjected to NOx emission constraint. This research deals with quasi-dimensional, two-zone thermodynamic simulation of four-stroke SI engine fueled with CNG/H2 blended fuel for the prediction of the combustion and emission characteristics. The validity of the model has been carried out by comparing the computed results with experimental data obtained under same engine setup and operating conditions. A wide range of engine parameters were optimized using a simple GA regarding both engine efficiency and NOx emissions. The five parameters chosen were compression ratio, engine speed, equivalence ratio, H2 fraction in the fuel, and spark plug position in cylinder head. The amount of NOx emissions was being kept under the constrained value of 750 ppm (< 5 g/kWh), which is less than permissible limit for heavy-duty engines.
Integrated Control of Tire Normal Forces and Active Front Steering to Enhance Vehicle Handling
Authors: March Carl , Shim Taehyun , Zhang Yi
Published: April 2008

This paper presents the development of an active front steering (AFS) control system and normal force control (NFC) scheme utilizing fuzzy reasoning to track neutral steer yaw rate. The performance of the stand-alone controllers is compared with an integrated chassis management scheme combining the two. The simulation results indicate that the NFC by the active suspension as a stand-alone system shows improvement in vehicle handling response. The integrated chassis control scheme utilizing the steering and suspension controllers is proven to be more effective in attaining the desired performance that would not be attained individually.
Three-Dimensional Microfabrication System for Biodegradable Microdevices With High-Resolution and Bio-Applicability
Authors: Yamada Akira , Niikura Fuminori , Ikuta Koji
Published: April 2008

Biodegradable polymers are employed in medicine and its further application is expected with eagerness. But the lack of an appropriate processing method retards the progress. To overcome this problem, we have developped a novel three-dimensional microfabrication system. The system design allows us the processing of the free three-dimensional micro-level forms by stacking up melted polymers from the nozzle. Different from the conventional method, we adopted a batch process to supply materials in order to eliminate the prior process that required toxic solvents. In addition, it is possible to handle almost all biodegradable thermoplastic resins by adopting this system. A single layer from the piled-up layers of extruded lines was observed to evaluate the resolution. The lateral and depth resolutions attained are 40 μm and 45 μm, respectively. Biodegradable polymers enable three-dimensional microstructures such as micro-pipes, micro-bends, and micro-coil springs to be manufactured in less than 15 min. The biocompatibility of the newly fabricated structure was evaluated using a cell line (PC12). For this purpose, a small vessel, with a transparent base, was fabricated using PLA and cells were cultivated in it. The results were then compared with the results obtained using the standard method. The mechanical strength of our microstructures was evaluated using a tensile strength test. The tensile strength of the microstructure was lower than the one obtained from the conventional method, but has enough strength for fabrication of medical devices. Our system renders it possible to produce toxic-free, as well as transparent and leakage-free devices. Our system is expected to have potential applications in optimum design and fabrication of implantable devices, especially in tissue engineering.
Boundary Element Analysis of Interface Cracks
Authors: Hadjesfandiari A. R. , Dargush G. F.
Published: April 2008

A new boundary element formulation is developed to determine the complex stress intensity factors associated with cracks on the interface between dissimilar materials. This represents an extension of the methodology developed previously by the authors for determination of free-edge generalized stress intensity factors on bimaterial interfaces, which employs displacements and weighted tractions as primary variables. However, in the present work, the characteristic oscillating stress singularity is addressed through the introduction of modified weighting functions and corresponding numerical quadrature formulas. As a result, this boundary-only approach provides extremely accurate mesh-independent solutions for a range of interface crack problems. A number of computational examples are considered to assess the performance of the method in comparison with analytical solutions and previous work on the subject.
Design and Modeling of Thermally Actuated MEMS Nanopositioners
Authors: Bergna Se´bastien , Gorman Jason J. , Dagalakis Nicholas G.
Published: April 2008

Several micro-scale nanopositioning mechanisms, or MEMS nanopositioners, have been developed for application in nanotechnology and optical sensors. In this paper, the design and modeling of these devices is presented along with initial experimental results. The MEMS nanopositioner is comprised of a parallel bi-lever flexure mechanism and a bent-beam thermal actuator. The flexure mechanism is designed to amplify and guide the motion of the actuator with high precision, while the thermal actuator provides the necessary force and displacement. The relationship between the applied voltage and resulting displacement for this mechanism has been calibrated using a scanning electron microscope and a simple image processing technique. A finite difference thermal model along with a FEA representation of the flexure mechanism and actuator is used to estimate the motion range of the device. Results from this method are compared with experimental calibrations, showing that the model provides a sufficient approach to predict the mechanism’s static performance. Finally, an open-loop controller based on calibration data was used to demonstrate the nanopositioning capabilities of these devices. The motion repeatability was found to be less than +/- 7 nm and step sizes well below 50 nm are possible, indicating suitable performance for many nanopositioning applications.
New Nonlinear Observer Design With Application to Electrostatic Micro-Actuators
Authors: Durbha Venkat , Balakrishnan S. N.
Published: April 2008

In many practical applications it is not possible to measure all the states required to control the system. In such instances observer/filter is used to give a good estimate of the states of the system. The objective of the observer is to estimate the states such that the error between the actual and computed measurements goes to zero and obtain the “best” estimates of the states of a given system. In the current study a new nonlinear observer structure is proposed. The development of the observer is based on optimal control theory. A cost function is defined in terms of the measurement residual and the magnitude of correction term. The observer gains are obtained by minimizing the cost function with respect to the magnitude of corrections. The proposed observer is used to estimate the states of a one-dimensional electrostatic micro-actuator. The states of the actuator dynamics are, charge on the capacitor plates, the distance between the plates and the relative velocity between the plates. The regulation of the actuator states to desired trajectories is achieved through optimal control based state feedback. However in practice it is very difficult to measure the relative position and velocity of the plates. In this paper optimal feedback control based on the state estimates provided by the observer is used to regulate the actuator states to the desired location.
The Role of the Interactions Between the Primary Jets and the Recirculation Zone of a Model Gas Turbine Combustor on Pollutant Emissions
Authors: ELKady Ahmed M. , Jeng San-Mou , Mongia Hukam
Published: April 2008

The present work investigates the effect of utilizing transverse air jets as well as its interactions with the recirculation zone on pollutant emission characteristics at different jet locations, jet mass ratios, and overall equivalence ratio. A multiple gas analyzer based on Fourier transform infrared (FTIR) spectroscopy is employed to measure emissions concentrations generated during combustion of Jet-A fuel in a swirl-cup assembly. The goal of this study is to provide more insight into nitric oxides and carbon monoxide production within the primary zone of a highly swirling combustion and methods to reduce its formation. The results reveal the possibility of injecting air into the recirculation zone without altering the flame stability. Besides, depending on the jet location and strength, nitric oxides as well as carbon monoxide can be reduced simultaneously. Placing the primary air jet just downstream of the rich fuel recirculation zone can lead to 40% reduction in both nitric oxides and carbon monoxide. While in the case of recirculation zones in the lean side of stoichiometry, reduction of nitric oxides can occur if the air jets are placed just 1 inch above the swirler exit.
Steady State Model of a Solar Evacuated Tube Collector Based on Sensitivity Analysis
Authors: Praene Jean Philippe , Garde Franc¸ois , Lucas Franck
Published: April 2008

This work deals with first modelling the dynamical behavior of the solar collector under natural tropical humid conditions. In a second part, this paper proposes a sensitivity analysis which lays on fast method. This analysis is very interesting as it allows pointing out the most influential factors. Finally, it is shown that the output of the model could be approach by polynomial of regression called “me´tamode`le”. This approximation constitutes a local approximation of the output of the solar collector, working under steady state conditions.
A Generalized Robust Control Framework Utilizing Dimensional Analysis
Authors: Li Yan , Alleyne Andrew
Published: April 2008

Most engineered systems designed under heavy external constraints share similar dynamics. Using a dimensionless model as system representation, a dimensionless robust controller can be designed and implemented for a class of dynamically similar systems that are different in size. Dimensionless transformations of time scale, inputs and outputs determine a nominal plant model and plant-to-plant uncertainties in a dimensionless form. Using parameter-dependent normalization, a normalized dimensionless model can be derived that has low level of plant-to-plant uncertainties. The benefit of this dimensional analysis is demonstrated by the analysis of a passenger vehicle model for yaw rate control with a database consisting of 36 sets of vehicle data.
Robust Adaptive Tracking Control of Delta Wing Vortex-Coupled Roll Dynamics Subject to Delay
Authors: Pakmehr M. , Gordon B. W. , Rabbath C. A.
Published: April 2008

In this paper a combinatory control strategy combined of a modified state feedback stabilizing controller, as the internal loop, and a robust adaptive sliding tracking controller has been proposed to be applied to the vortex-coupled roll dynamics of delta wing subject to state delay. The first subcomponent renders the closed-loop system globally practically stable. The second one is a robust adaptive sliding tracking controller which utilizes a special gaussian RBF neural network for online estimation of rolling moment coefficient as the main uncertainty of the model. To show the ability of the proposed combinatory control structure, it has been implemented to delta wing system to follow a sophisticated reference trajectory. Implementing the proposed combinatory control structure (controller with internal loop) enhanced the tracking performance in comparison to the controller without internal loop. Adding two more control inputs as a fraction of the first control input in the combinatory control structure (can be interpreted as perturbations in the vortex breakdown dynamics), also enhanced the tracking controller performance compared with the case without perturbations. Delta wing system simulation study demonstrated acceptable performance of the proposed combinatory control structure.
Multiscale Design of Vascular Plates
Authors: Maute K. , Dunn M. L. , Bischel R. , Howard M. , Pajot J. M.
Published: April 2008

Inspired by actuation mechanisms in plant structures and motivated by recent advances in electro-chemically driven micro-pumps, this paper is concerned with a novel concept for active materials based on distributed hydraulic actuation. Due to the similarity of the actuation principles seen in plants undergoing nastic motion, we refer to this class of active materials as nastic materials. We present a mechanical modeling approach for nastic materials representing the effects of pressure generation and fluid transport by incompressible eigenstrains. This model is embedded into a two-level macro/micro topology optimization procedure. On a macroscopic level, the integration of nastic material into a structural system is optimized. The placement and distribution of nastic material on a flexible substrate are optimized to generate target displacement and force distributions. On a microscopic level, the stress and strain generation is tailored to desired macroscopic material properties by optimizing the layout of vascular fluid channels embedded in an elastic matrix. For the layout optimization of vascular fluid channels, a novel topology optimization procedure is presented that models the effects of pressure along the fluid channels via an analogy with thermal conduction and convection. For this purpose an auxiliary heat transfer problem is solved. The macro-scale optimization procedure is studied for plate structures patterned by nastic materials in order to generate target bending and twist deformations. The results show the significant differences of the optimal distributions of active material depending on the strain model used for representing the actuation concept. The micro-scale vascular design methodology is verified with plane-stress examples. The results show that the layout of fluid channels can be optimized such that target strains are generated.
A Numerical Model for Micro Balloon-Jointed Actuation
Authors: An ZhiYong , Lu Yenwen
Published: April 2008

This paper reports a theoretical study of the pneumatic balloon-jointed actuation, which has been utilized in the microfinger and the microhand to perform an out-of-plane rotation [1]. The finite element method (FEM) is utilized to describe and to predict the performance of this actuation, in terms of the actuation angles, forces, and structure stiffness. Several related geometrical parameters have been studied, providing the guidelines of the micro balloon-jointed actuation.
Multiphysics Modeling of a Piezoelectric Bimorph Disc in a Direct Write Fabrication Process
Authors: Desai Salil , Lovell Michael
Published: April 2008

This paper investigates the behavior of the Piezoelectric (PZT) Bimorph disc within a Direct Write Fabrication Process. A modified Continuous Inkjet Print (CIJ) method is utilized to deposit a variety of conductive nano particulate materials for building miniaturized devices that can sustain harsh environments. Typical example includes the fabrication of electronic devices that are subject to severe fluctuations to temperature gradients. The spatial and temporal complexity of the novel CIJ based microfabrication process necessitates a computational solution to complement its experimental development. The interaction of three fields namely; electrostatic, structural and fluidic in the CIJ head are captured within a single Multiphysics model. A fluid-structure interaction (FSI) algorithm is used to capture the interaction of the PZT disc with the ink media. The effects of input parameters such as pressure, frequency and voltage on the PZT disc displacement are studied. Further, their effects on the transient pattern of the PZT displacement are explained. The findings from this research can be utilized to control the PZT disc displacements which, ultimately can be used to obtain an optimized and consistent drop break up for high precision printing.
Robust Backstepping Control of Robotic Nurse Unit to Assist Paraplegic Patient
Authors: Selk Ghafari Ali , Meghdari Ali
Published: April 2008

A robust motion controller based on backstepping technique for a robotic nurse unit to assist paraplegic patients is addressed in this paper. A backstepping controller is proposed for tracking a desired trajectory in hospital environment. Simulation results are provided to validate the proposed controller. The results show satisfactory performance of the designed controller in tracking problem.
Micro-Precision Hydrostatic Actuation System
Authors: Habibi S. R. , Burton R. , Sampson E.
Published: April 2008

This paper reports on an important discovery that is: hydrostatic actuation systems are able to manipulate heavy loads with sub-micron precision and large stroke. In this relation, the design of a high-precision hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA) is presented. A laboratory prototype of this system has achieved an unprecedented level of performance by being able to move a large load of 20Kg with a precision of 50 nanometers and a stroke of 12cm. This level of performance places the hydrostatic actuation concept in competition with piezoelectric platforms in terms positional accuracy. Experimental results from this prototype are reported and analyzed.
Thermal and Fluid Dynamic Behavior of a Horizontal Channel With Adiabatic Moving Lower Plate
Authors: Andreozzi Assunta , Naso Vincenzo , Manca Oronzio
Published: April 2008

In this study a numerical investigation of mixed convection in air in horizontal parallel walled channels with moving lower plate is carried out. The moving lower plate has a constant velocity and it is adiabatic, whereas the upper one is heated at uniform heat flux. The effects of horizontal channel height, heat flux and moving plate velocity are analyzed. Results in terms of temperature and stream function fields are given and the mass flow rate per unit of length and divided by the dynamic viscosity is reported as a function of Reynolds number based on the moving plate velocity. For stationary condition of lower plate, a typical C–loop inside the horizontal channel is detected. Different flow motions are observed in the channel and the two reservoirs, depending on the heat flux values and the distance between the heated upper stationary plate and lower adiabatic moving plate. The dimensionless induced mass flow rate presents different increase between the Reynolds number lower or greater than 1000.
Auxetic Cellular Materials and Structures
Authors: Grima Joseph N. , Gatt Ruben , Farrugaia Pierre-Sandre , Alderson Andrew , Evans Kenneth E.
Published: April 2008

Auxetic materials and structures exhibit the very unusual property of becoming wider when stretched and narrower when squashed (i.e. they have a negative ‘Poisson’s ratio’). This property results in many beneficial effects in the characteristics of the system that make auxetics superior to conventional systems in many practical and high tech applications, including aeronautics where, for example, auxetics are being proposed as potential components for the production of better quality lifting devices such as helicopter rotor blades or airplane wings. This work reviews and discusses the behaviour of known and novel cellular systems, which exhibit this unusual but highly desirable property.
Progressive Damage and Delamination in Plain Weave S-2 Glass/SC-15 Composites Under Quasi-Static Punch Shear Loading
Authors: Xiao J. R. , Gama B. A. , Gillespie J. W.
Published: April 2008

Quasi-static punch-shear tests are carried out on plain weave (PW) S-2 glass/SC-15 epoxy composite laminates with a right circular cylinder punch to identify the sequence and extent of damage and the corresponding displacements at which they occur for a wide range of laminate thicknesses. Two different support spans of 25.4 mm (1 in) and 101.6 mm (4 in) diameter with different layers (0.6 mm ply thickness) of composite laminates are tested under quasi-static loading to identify compression-shear and tension-shear dominated modes of damage. Numerical punch shear experiments are conducted using LS-DYNA 970. The numerical modeling is carried out using a newly developed composite damage model, namely MAT 162, which has been incorporated into LS-DYNA. MAT 162 uses damage mechanics principle for progressive damage and material degradation. Input data required in MAT 162 have been calibrated to match the experimental results of 22-layer composite plate of both spans (25.4 mm and 101.6 mm). The calibrated material properties have been used to simulate other thicknesses, and the simulated results show good agreement with experiment results. It has been found that the dominant damage mechanisms are delamination and fiber breakage due to shear and tension.
Undergraduate Research Program in Mechatronics for Machine Tools and Micro-Systems
Authors: Rodriguez Ciro A. , Ahuett Horacio , Elias Alex , Molina Arturo , Ortega Carlos , Llamas Hugo , Forsbach Sebastian
Published: April 2008

This paper describes an undergraduate research program recently established at the Instituto Tecnolo´gico y de Estudios Superiores de Monterrey (ITESM). The motivation, structure and expected benefits of this program are presented. Early results are illustrated through case studies. The first case study focuses on the evaluation of cycle time and contouring error in high performance machining centers. Contouring error measurement is conducted with a Heidenhain Grid Encoder on several high performance machining centers and tool path shapes. The second case study focuses on the development of an experimental micro-positioning systems based on compliant mechanisms and smart materials for actuation.