bluuebunny/crossref_metadata_2025 huggingface dataset:
Project-Oriented and Problem-Based Learning:A Mechatronic Curriculum
Authors: Hansen Michael Rygaard , Andersen Torben Ole
Published: April 2008

Mechatronics engineering is an emerging technology. New applications where a mechatronic approach is needed are added continuously. The demands to the education of engineers in this field are also increasing. Basically the challenge is to increase the content of the curriculum within usual study time. This paper presents a complete curriculum at Aalborg University based on problem-oriented and project-based learning from day one. This teaching approach has proven to be very well suited for mechatronics engineering as it provides the required holistic view of the multidisciplinary design process in a natural way. The trend and application of mechatronics engineering and research are illustrated followed up by a discussion on how problem-oriented and project-based learning are implemented in Aalborg with a number of project examples.
Comparison of Gas Nucleation and Pool Boiling Site Densities
Authors: Qi Yusen , Klausner James F.
Published: April 2008

It has been well established that the rate of heat transfer associated with boiling systems is strongly dependent on the nucleation site density. Over many years attempts have been made to predict nucleation site density in boiling systems using a variety of techniques. With the exception of specially prepared surfaces, these attempts have met with little success. This paper presents an experimental investigation of nucleation site density measured on roughly polished brass and stainless steel surfaces for gas nucleation and pool boiling over a large parameter space. The fluids used for this study, distilled water and ethanol, are moderately wetting and highly wetting, respectively. Using distilled water it has been observed that the trends of nucleation site density versus the inverse of the critical radius are similar for pool boiling and gas nucleation. The nucleation site density is higher for gas nucleation than for pool boiling. An unexpected result has been observed with ethanol as the heat transfer fluid, which casts doubt on the general validity of heterogeneous nucleation theory. Due to flooding, few sites are active on the brass surface and at most two are active on the stainless steel surface during gas nucleation experiments. However, nucleation sites readily form in large concentration on both the brass and stainless steel surfaces during pool boiling. The nucleation site densities for the rough and mirror polished brass surfaces are also compared. It shows that there is no large difference for the measured nucleation site density.
An Approach to Specifying the Dynamic Performance of a Hitch Valve on an Agricultural Tractor
Authors: Andersen Torben Ole , Hansen Michael R. , Nielsen Brian
Published: April 2008

This paper is on the design of control systems to handle the the oscillations occurring on tractors without any suspension. During transport phases, the lack of suspension causes the vehicle to bounce and pitch, and makes it difficult to control. A number of different approaches to actively damping the oscillations exist. In the current paper one of these control schemes are adopted and used together with an experimentally verified model of an agricultural tractor to determine the necessary requirements to the hitch valve by means of optimization. The design variables include controller gain, valve response time and valve dead band whereas the criteria are the comfort of the driver, the energy consumption and the loading of the mechanical parts of the hitch linkage.
Reliability Issues in MEMS Related to Cyclic Loading Conditions
Authors: Kraft Oliver , Volkert Cynthia A.
Published: April 2008

Continuous and patterned metal thin films are widely used in micro-electro-mechanical systems (MEMS). Applications range from reflective coatings in micro-optics to current carrying metallization in sensors and actuators. In these applications, temperature changes of up to several 100°C may occur, and as a result of thermal mismatch between film and substrate materials, large mechanical stresses arise. For instance, gas sensors containing metal thin films are cycled to temperatures well above 300°C[1] and temperatures up to 800°C can be anticipated in the future. Fig. 1 illustrates the effect of temperature changes on the stress development in a thin film, for the case when the substrate has a smaller thermal expansion coefficient than the film. Initially, at room temperature, the metal film under biaxial tension. On heating, the film tends to expand more than the substrate and the tensile stress in the film is reduced. For small stresses, the film and substrate behave elastically, and the slope of the curve in Fig. 1 is given by ΔαEf/(1−νf) where Δα is the difference in thermal expansion coefficients, and Ef and νf are Young’s modulus and Poisson’s ratio of the film material. Above a certain stress (in this case reached at around 250°C on heating), the film begins to plastically deform. On cooling from the maximum temperature of 500°C, the film tends to contract more than the substrate and, as a result, the film stress becomes tensile. The total strain range, Δεth is given by Δεth=ΔαΔT, where ΔT is the temperature range. Thus, for the applications mentioned above, thin metal films encounter strain ranges up to 1% and will undergo both elastic and plastic deformation during use.
Modeling Thin-Walled Microbubbles for Medical Ultrasound
Authors: Sarkar Kausik , Jain Pankaj , Chatterjee Dhiman
Published: April 2008

Microbubble contrast agents injected into patient’s body increases contrast of ultrasound images. They are encapsulated by a thin layer of surface active materials to prevent their dissolution inside the body. Here we provide a detail procedure of characterizing them by in vitro acoustic experiment and modeling. The encapsulation is modeled as an interface having an intrinsic surface rheology. The rheological parameters are determined by matching the model with measured attenuation. We have characterized contrast agent Definity with surface tension γ, and dilatational viscosity κs. We also the variation of properties with driving frequency.
Destruction of Definity® Microbubbles Used for Ultrasound Imaging and Drug Delivery
Authors: Sarkar Kausik , Jain Pankaj , Chatterjee Dhiman
Published: April 2008

Microbubble based contrast agents improves medical ultrasound images. Destruction of contrast agent Definity® (Bristol Meyer-Squibb Imaging, North Ballerina, MA) is studied using broadband attenuation technique. Single-cycle ultrasound pulses are sent through a bubble suspension at different pulse repetition frequencies (PRF) and pressure amplitudes. For each PRF, there is a critical pressure amplitude (~1.1–1.2MPa for 50, 100, 200 Hz PRFs studied), below which there is no evidence of bubble destruction. Above the critical pressure amplitudes the rate of destruction depends on PRF and pressure. But at high pressure amplitudes (e.g. 2.97 MPa) destruction becomes independent at higher PRFs.
Exploiting the Confined Twin-Jet Instability for Micro Mixing Enhancement
Authors: Nahum Assaf , Seifert Avraham
Published: April 2008

A method for exploiting hydrodynamic instability for enhancement of micro-mixing is proposed, studied numerically and demonstrated experimentally. The confined twin-jet geometry is selected as the baseline unstable flow, since it undergoes a Hopf bifurcation at low Reynolds numbers. It is shown that by adding weak fluidic perturbation to the mean flow, significant amplification of unstable modes results, leading to enhanced mixing in laminar flow. Good agreement was found between Computational Fluid Dynamics (CFD) and experimental results for the critical Re, for which instability sets-in, and its related Struohal number. In order to evaluate mixing efficiency, backward tracing particle was performed using the computed flow field. Mixing is estimated based on particle’s location in time and space. A parametric mixing study was performed and its results are presented and discussed. It is shown that mixing was significantly enhanced when the perturbation frequency was matched with the baseline’s most-unstable Struohal number, even for sub-critical Reynolds number.
In Vitro Investigation of Contrast Mixability for Functional Angiography
Authors: Lieber Baruch B. , Gounis Matthew J. , Bahar Nico
Published: April 2008

Ever since x-ray cine-angiography was employed to visualize blood vessels, the observed flow of contrast through the vasculature enticed researches to attempt evaluation of blood flow or its velocity through the observed contrast dispersion. However, despite considerable efforts that were expended both in vitro on phantoms and in vivo, the determination of blood flow from the observed contrast remains elusive. What conspired to frustrate these efforts are the complex physical phenomena that govern the dispersion of a bolus of contrast in the pulsatile flowing blood solvent. Further, what compounded the difficulties is the deteriorating visibility of the contrast as it dispersed in the blood. In this experiment we investigate the dispersion of iodine based contrast material as is settles in slender glass vials filled with various fluids that are commonly used to either dilute the contrast material for in vivo application or as fluid media into which the contrast is injected both in vivo and in vitro.
Dynamic Analysis of a Serpentine Belt Drive With a Decoupler/Isolator
Authors: Balaji Raghavan , Mockensturm Eric M.
Published: April 2008

Belt drives employing a single, flat serpentine belt tensioned by a passive tensioner are found in automotive engine Front End Accessory Drive (FEAD) where the crankshaft supplies power to accessories like alternators, air-conditioning compressors, pumps, etc. [1]. When the FEAD undergoes forced vibration due to crankshaft excitation, dynamic tension fluctuations can cause the belt to slip on the accessory pulleys [2]. The probability of belt slip increases with the peak drop in belt tension over the pulley during steady state operation [3]. In this paper, one possible solution is analyzed, using a decoupler to isolate/separate the accessory inertia (e.g. alternator) from the FEAD system. This is achieved by placing between the pulley and the accessory a combination of a one-way rigid clutch and an isolator spring. In this study, the rotational response of a typical FEAD is extended to include the clutch and isolator. An analytical solution is then obtained by considering it as a piecewise-linearized system moving about an equilibrium angular displacements. The performance of the ordinary FEAD with regard to tension fluctuation is then compared to that of the system equipped with a decoupler/isolator. The results obtained indicate that within the practical working range of engine speeds, use of either an isolator or a decoupler-isolator could significantly lower the dynamic tension drop across the accessory pulley.
Precision MEMS Nano-Cutting Device for Cellular Microsurgery
Authors: Chang Wesley C. , Keller Christopher G. , Sretavan David W.
Published: April 2008

An important tool for biological research and microsurgery is a microdevice for the cutting and isolation of subcellular neuronal components such as axons and dendrites for analysis or microsurgery. We have fabricated an easy-to-use, inexpensive and robust MEMS device with a nanoscale cutting tool that performs highly reproducible cutting of axons and dendrites. The device consists of a knife with an 20 nm-sharp edge ranging from 10–200 microns in length and is formed from molding conformally deposited silicon nitride over a potassium hydroxide-etched trench in <100>-oriented single crystal silicon. Knife surfaces are coated with a thin layer of liquid perfluorinated polyether to prevent adhesion of debris from cut targets. The knife is assembled onto a microfabricated suspension and frame consisting of serpentine flexures of single crystal silicon. These supporting structures help to properly orient the knife and control cutting force. We have used this assembled nano-cutting device to make reliable cuts of individual living dendrites and unmyelinated and myelinated axons from both adult and embryonic animal tissue. The cutting device was able to target and cut specific cell processes within a complex field and without disturbing surrounding structures. The cuts were sharp and repeatable, and microdevice’s performance was undiminished with repeated use.
Microstructural Analysis and Control of Magneto-Rheological Fluid
Authors: Bechtel Stephen , Washington Gregory , Ahmadkhanlou Farzad , Wang Yingru
Published: April 2008

Characteristic phenomenological behavior of MR fluids is typically modeled by Bingham’s equation, which has no fundamental connection to the microstructure of MR fluid and the fully coupled mechanical-electrical-magnetic equations. In this paper microstructurally, kinetic theory-based model of MR fluids (consisting of micro-sized ferrous particles suspended in a Newtonian fluid) are developed. For modeling these composite systems, dumbbell models in which two beads joined by an elastic connector are investigated. In these models the distributed forces from the carrier fluid and from the magnetic field on the suspended particle are idealized as being localized on beads. Microscale constitutive equations relating flow, stress, and particle orientation are produced by integrating the coupled equations governing forces, flow, and orientation over a representative volume of particles and carrier fluid. Coefficients in the constitutive equations are specified not by a fit to macroscale experimental flow measurement but rather in terms of primitive measurements of particle microstructure, carrier fluid, viscosity and density, and temperature. These new models for MR fluids are three dimensional and applicable to any flow geometry, while the Bingham plastic model is in general applicable only to shear flow. The models in this paper reduce to forms similar to Bingham’s model in a simple shear flow, but with coefficients which arise from fundamental electromagnetic considerations and microstructural features such as geometrical, magnetic and mechanical characterization of the particles, quantities measured primitively from the carrier fluid, magnetic field and temperature.
Finite Element Analysis of Transverse Impact on a Woven Textile
Authors: Duan Yiping , Keefe Michael , Bogetti Travis A. , Powers Brian
Published: April 2008

High-strength textiles are widely used in soft impact threat shield systems. During the past several decades, a lot of experiments and theoretical work were conducted to understand the transverse impact behavior of textile structures. As a continuation of those efforts, this paper presents finite element modeling of transverse impact of a rigid right circular cylinder into a square patch of plain-woven textile. Two boundary conditions are applied on the woven textile: four edges clamped; two opposite edges clamped and the other two edges left free. Results show that during the initial stage of the impact, there exists an abrupt momentum/energy transfer from the projectile to the local textile in the impact region. The modeling results also show that the textile boundary condition plays an important role in the impact. It significantly affects the textile transient deformation, stress distribution, energy absorption, and failure modes. The textile absorbs energy more quickly when all its four edges are clamped.
Performance and Development of a Miniature Rotary Shaft Pump (RSP)
Authors: Blanchard Daniel B. , Ligrani Phillip M. , Gale Bruce K.
Published: April 2008

The development and performance of a novel miniature pump called the rotary shaft pump (RSP) is described. The impeller is made by boring a hole in one end of a shaft, and cutting slots in the side of the shaft at the bottom of the bored hole, such that the metal between the slots defines the impeller blades. Several impeller designs are tested over a range of operating conditions. Pump performance characteristics, including pressure rise, efficiency, slip factor, and flow rate are presented for several different pump configurations, with maximum flow rate and pressure rise of 64.9ml/min, and 2.1kPa, respectively, when the working fluid is water. Potential applications include transport of biomedical fluids, drug delivery, total analysis systems, and electronics cooling.
Experimental Investigation Into Rotary Ultrasonic Machining of Alumina
Authors: Zeng W. M. , Li Z. C. , Churi N. J. , Pei Z. J. , Treadwell C.
Published: April 2008

Many experimental studies have been conducted to explore the relations between control variables and process outputs in rotary ultrasonic machining (RUM). However, there are few reports on the comparison between RUM and conventional diamond drilling. In this paper, the cutting force and surface roughness are compared when machining alumina with RUM method and with conventional diamond drilling method. Furthermore, the effects of the control variables (rotational speed, feed rate, and ultrasonic power) on RUM outputs (such as cutting force and surface roughness) are studied. It is found that in comparison with conventional diamond drilling, the cutting force can be reduced significantly and the surface roughness can be improved by using RUM. It is also found that rotational speed, feed rate, and ultrasonic power have significant effects on RUM process.
Dispersion Characterization of Nanoclay in Molded Epoxy Disks by Combined Image and Electron Microbeam Analysis
Authors: Aktas Levent , Hamidi Youssef K. , Altan M. Cengiz
Published: April 2008

The state of nanoclay dispersion in a molded epoxy disk and its effects on the thermo-mechanical properties of the resulting nanocomposite are analyzed. A commercially available nanoclay, Cloisite® 25A, is mechanically mixed at 2wt.% with EPON 815C epoxy resin. The epoxy/clay compound is then mixed with EPI-CURE 3282 curing agent by a custom made molding setup and injected into a disk shaped mold cavity. Upon completion of curing, nanoclay dispersion is quantified using Cameca SX50 Electron Microprobe Analyzer (EMPA) on a sample cut along the radius of the composite disk. Dispersion of nanoclay clusters larger than 1.5μm are analyzed by digital image processing of scanning electron micrographs taken radially along the sample, whereas dispersion at smaller scales is quantified by compositional analysis of clay via wavelength dispersive spectrometry (WDS). Digital images of the microstructure indicate that amount of nanoclay clusters that are larger than 1.5μm remain approximately constant along the radius. However, size analysis of nanoclay clusters revealed that they are broken down into finer clusters along the radius, possibly due to high shear deformation induced through-the-thickness during mold filling. Compositional analysis by WDS signified that approximately 0.4wt.% of the nanoclay is dispersed to particles smaller than 1.5μm which are not visible in micrographs. Tensile and three-point bending tests are conducted on additional samples cut from the molded disks. Except for slight reduction in flexural strength, up to 9.5% increase in tensile strength, stiffness and flexural modulus are observed. Glass transition temperature is determined under oscillatory torsion and observed to increase by 4.5% by the addition of nanoclay.
Feedforward Laser Power Specification for Uniform Cooling of Thin-Walled Parts
Authors: Korde Umesh A. , Langerman Michael A. , Buck Gregory A. , Kalanovic Vojislav D.
Published: April 2008

This paper presents results from ongoing research on thermal-model based feedforward specification of laser power in a laser powder deposition process. The goal of this algorithm is to compute, before deposition of a layer, the laser power sequence and distribution that would produce a desired temperature distribution over that layer. This in turn will enable uniform cooling of the layer and avoid build up of residual stresses. In this paper, results based on a simplified thermal model and second-order spatial discretization are presented. Two types of discretization in the time domain are examined. The matrix-exponential-based discretization is expected to be more accurate at lower laser speeds. The desired laser power sequence and the resulting temperature histories for a prescribed laser speed are discussed within the context of a thin-walled part.
Elongation Variability of AM60 Die Cast Specimens
Authors: Chen Xiaoming , Wagner David A. , Houston Dan Q. , Cooper Ronald P.
Published: April 2008

Tensile properties of die cast magnesium AM60 were investigated by testing tensile bar specimens obtained from three sources. The first series of tensile bars were cut from eight locations from multiple copies of a die cast magnesium AM60 automotive instrument panel beam. The second series were cut from six-inch square AM60 die cast plates in both the parallel and perpendicular to the flow direction. The last series of specimens were die cast AM60 tensile bars. The measured yield stress did not significantly depend on the specimen source and matched published values. However, the elongation as determined by the engineering strain at break in the tensile test varied significantly for samples cut from the automotive instrument panel beams and those cut from the six-inch by six-inch plates. The elongation remained constant for the cast tensile bars. Statistic General Linear Models were used to study the effect of casting conditions on both the yield stress and the strain at break. Sample location within the beams was the main factor for the material property variation.
Modeling the Behavior of Insertion-Mounted Components — Part 1
Authors: Valentin Ricky , Barker Donald , Johnson Aaron
Published: April 2008

Insertion mount, or trough hole, technology has historically been considered a fatigue-free method for soldering components to printed circuit boards; recently, though, applications implementing this technology have experienced use lifetimes sufficient to warrant investigation into fatigue failure. Although much research has been done into failure mechanisms and rapid failure prediction methods for surface mount components, there have been on such studies in the area of insertion mount technology. Therefore, this paper will be the first in a series of two papers introducing a rapid failure assessment approach for components fixed using insertion mount technology. The purpose of this paper will be to introduce the methodology used in this study, as well as to provide a method for determining the critical lead forces quickly and accurately.
High Efficiency Mixing in the Shear Superposition Micromixer
Authors: Bottausci Fre´de´ric , Cardonne Caroline , Mezic Igor , Meinhart Carl
Published: April 2008

We present a numerical and experimental study of the mixing in a Micro Electro Mechanical System (MEMS). The mixer is an active micromixer. Its design consists of a main mixing channel where the main flow is perturbed by jet flows emanating from a series of secondary channels. The lateral flows oscillate in time and reorient the lamination of passive tracers from streamwise to cross-stream. The micromixer is a silicon-etched device where the main channel is 2h wide, 13h long and h deep (h = 100 microns). The secondary channels are 5h long and h/2 wide. The parameters (flow rate, frequency, and amplitude of oscillations) are accurately controlled. The mixing process is studied numerically and experimentally using flow visualizations techniques. The numerical simulations are performed for the 3-D flow. We analyze the mixing properties using the Mixing Variance Coefficient (MVC).
MR Fluid Behavior Under Constant Shear Rates and High Magnetic Fields Over Long Time Periods
Authors: Ciocanel Constantin , Molyet Kevin , Yamamoto Hideki , Vieira Sheila L. , Naganathan Nagi G.
Published: April 2008

MR fluids are smart materials that reversibly change their rheological properties in the presence of a magnetic field. Their capability to support a high range of shear stresses makes them an ideal component of many mechanical devices. However, to be suitable for applications requiring a large number of cycles, e.g. a clutch, the long term behavior of these fluids needs to be thoroughly investigated and well understood. The paper presents a new MR cell design along with a study of the shear rate, shear strain, magnetic field and time influences on the properties and behavior of a MR fluid tested for long periods of time. The MR cell is required to adapt a commercially available rheometer to measure the rheological properties of the fluid. Overall characteristics of the designed MR cell output capability are provided. Constant shear rate tests, two hours in duration, have been performed at shear rates between 0.1 and 200 l/s under magnetic field intensities up to 0.4 T. The rheological measurements indicated that the time, the shear strain and the shear rate influence the fluid’s shear stress magnitude.
Investigation of MEMS Resonator Characteristics for Long-Term and Wide Temperature Variation Operation
Authors: Kim Bongsang , Candler Rob N. , Hopcroft Matthew , Agarwal Manu , Park Woo-Tae , Li Jeffrey T. , Kenny Thomas
Published: April 2008

Two types of single-crystal silicon micromechanical resonators having resonant frequencies at 150 kHz and 130 kHz were tested under harsh environment to investigate stability. To observe long-term stability, the main characteristics, such as resonant frequency and quality factor were measured over 2,500 hrs continuously while maintaining constant environmental temperature at 25°C±0.1 °C. A separate experiment was also initiated to show stability during temperature cycling from −50°C to 80 °C. In both experiments, the total change in resonant frequency were less than 10 ppm and quality factor less than 10%, which demonstrates the stability of encapsulated micromechanical resonators upon exposure to harsh environments.
Pressure Drop Study and Correlation Development for Two-Phase Flow of R134a in Annular Helicoidal Pipe
Authors: Mo H. L. , Prattipati R. , Lin C. X.
Published: April 2008

Pressure drop characteristics of R134a in annular helicoidal pipe was investigated experimentally with R134a flowing in the annular section. The experimental results revealed that when more R134a vapor was condensed, the liquid phase pressure drop increased largely while the vapor phase pressure drop decreased slightly. By comparing with the experimental data obtained from the same test section with R134a flowing in the inner circular tube of the helicoidal pipe, it was observed that the pressure drop for refrigerant in the annular section was always larger. It was also observed that the helicoidal pipe orientation showed little effect on the pressure drop variations. A pressure drop correlation was developed from the experimental data in terms of pressure drop multiplier with respect to Lockhart-Martinelli parameter.
A New Mesostructural Soft Tissue Testing System With Multiaxial Loading and Local Strain Measurement Capabilities
Authors: Doehring Todd C. , Kahelin Michael , Vesely Ivan
Published: April 2008

A new mesostructural testing system (MSTS) has been developed to measure structural and material properties of soft tissues at an intermediate, or “mesostructural” scale (i.e. ~ .01 to 10 mm). Key features of this new system are biaxial computer controlled loading and synchronized high-resolution microscopic digital imaging. The system uses a marker-less feature tracking algorithm to measure local deformation of mesostructures such as the fiber bundles of the aortic valve. Validation and bioengineering applications are described.
Effect of Boundary Conditions and Initial Concentrations on the Solidification of Binary Mixture in Trapezoidal Cavity
Authors: Duggirala R. K. , Sirpal P. , Lin C. X. , Ghenai C.
Published: April 2008

The solidification of binary mixture (NH4Cl–H2O) inside a trapezoidal cavity is investigated experimentally in this study. The experiments are carried out in a trapezoidal cavity measuring 65 mm × 130 mm × 150 mm with inclined angle of 69°. Solidification of ammonium chloride occurs on the left inclined copper wall held under constant heat rate condition while the other walls are maintained at adiabatic conditions. Particle image velocimetry was used in this study for visualization of the dynamic field during the solidification process. The temperatures of the solution inside the cavity and the boundary walls were measured by 32 thermocouples during the solidification process. Convective flow field, temperature distribution and frozen layer thickness were obtained for different initial concentrations of ammonium chloride varying from 0 to 19.8 % (sub-eutectic and near-eutectic growth) and various boundary conditions (Tcold = −30 °C to 0 °C). The results obtained in the course of study reveal that (1) the solidification rate is higher during initial stages of the solidification process, (2) the process of solidification is slower with increase in the initial concentration levels of the ammonium chloride and (3) the initial concentration play a significant role in the evolution of convection flow patterns.
Flow and Heat Transfer of Microfoams in Horizontal Minichannels
Authors: Tseng Howard , Pilon Laurent
Published: April 2008

Colloidal gas aphrons (CGA) consists of closely packed minute gas bubbles with diameter ranging from 10 to 100 microns. It is produced by stirring a surfactant solution at high speed in a fully baffled beaker. CGA can be used in various applications such as bioremediation, bioreactors, oil recovery, and fire fighting. This paper reports experimental data for (1) adiabatic flow and (2) convective heat transfer of CGA into five 1.58 × 0.76 mm2 mini-rectangular channels. First, it is shown that CGA is a shear thinning fluid. Correlation for the Fanning friction factor as a function of Reynolds number is compared with that of water and macrofoams. Then, the local temperature and heat transfer coefficient along the minichannels are reported as a function of the mass flow rates and imposed heat flux. The heat transfer coefficients for CGA appears to be constant and independent of mass flow rate and imposed heat flux as well known in the case of single phase laminar flow.
1D Homogeneous Modeling of Microchannel Two-Phase Flow With Distributed Liquid Water Injection From Walls
Authors: Vigneron Se´bastien , Hidrovo Carlos H. , Wang Fu-Min , Lee Eon-Soo , Steinbrenner Julie E. , Kramer Theresa A. , Eaton John K. , Goodson Kenneth E.
Published: April 2008

This paper presents a theoretical model and a numerical simulation of a liquid-gas two-phase flow within a microchannel (50 μm × 500 μm × 2cm) equipped with distributed liquid water injection through the side walls. The modeling and solution of the conservation equations provide pressure drop as a function of inlet velocity. The influence of different parameters involving water injection is investigated, such as the quantity of water that is injected and the profile that is used to inject it. The numerical results show that for small water injection rates (1–10μL/min) the air flow velocity and pressure drop are not significantly perturbed by the presence of liquid water. But if water injection becomes important (10–100μL/min) larger pressure drops are observed. The influence of inlet pressure is also investigated. The model predictions are compared with experimental results obtained from testing a set of microchannels with a varying number of water injection slots on the side walls. Pressure drop distribution data from these experiments are consistent with model predictions.
Numerical Modeling of a Nonlinear MEMS Membrane
Authors: Crabtree Owen I. , Mesarovic Sinisa Dj. , Demir Ismail , Richards Robert F. , Bahr David F. , Richards Cecilia D.
Published: April 2008

A numerical model is developed to understand the behavior of a laminated, piezoelectric, geometrically nonlinear MEMS device. The finite difference method is chosen, along with the Newmark technique to model the static and vibrational behavior. This technique is validated by comparison to empirical data. The developed model is exercised to understand and optimize the device by studying residual stress, layer thicknesses, and electrode sizes with the goal of reduction of fundamental frequency and increase of charge output.
Micro-EDM Deposition Alloying Process
Authors: Ori Ricardo I. , Itoigawa Fumihiro , Hayakawa Shinya , Nakamura Takashi , Tanaka Shun-ichiro
Published: April 2008

A new deposition alloying process using Micro-EDM was developed. Using the energy released by the electrical discharge, material from the tool electrode is melted and deposited over the work surface. When a rotating bi-metal tool electrode is fed towards the work surface, the alloying between its elements occurs during process. The obtained results of the alloying between nickel and iron are presented in the present paper, when the components of the bi-metal tool electrode are made of YNi-1 (nickel alloy used in TIG welding — JIS standard) and medium carbon steel (S45C — JIS standard). X-ray and EDS analysis have shown that the chemical composition of the obtained deposit can be controlled and is proportional to the cross sectional area of each element present in the bi-metal electrode. With this process, a material with the same composition of Invar was successfully deposited.
Modeling and Characterization of MEMS Thermal Biosensors
Authors: Wang Li , Sipe David M. , Lin Qiao
Published: April 2008

In this paper, a closed-form analytical model, which considers the coupling of heat transfer effects and enzymatic reaction kinetics, is developed to describe the behavior of MEMS thermal biosensors for substrate detection either in flow-injection mode or flow-through mode. Simulation results show that the maximum thermopile output voltage is saturated at higher substrate concentrations for flow-injection mode. For flow-through mode, there exists an optimal flow rate which corresponds to the maximum thermopile output voltage. The optimal flow rate is inversely proportional to the concentration of the substrate involved in the reaction. A prototype MEMS thermal biosensor is fabricated and tested. The validity of the models is verified by comparison to the experimental results.
Component-Level Crash Optimization Within a System Environment
Authors: Averill Ronald C. , Halepatali Praveen , Sidhu Ranny
Published: April 2008

A new methodology is introduced to drastically reduce the time and effort required to perform vehicle crashworthy design optimization on components or subsystems whose performance is strongly coupled to that of the complete system to which they belong. The current approach reduces the CPU time for such design studies by a factor of 101 – 103, depending upon the problem definition. The main advantage of the current approach is that potentially thousands of design iterations can be performed in about the same amount of time required to perform a few (4–8) system level evaluations. With this approach, engineers can perform design studies and thoroughly explore new design concepts that were previously ignored due to their computational expense.
FE Calculations of J-Integrals on Crack Length in a Constrained Elastomeric Disc With Crack Surface Pressures and Isothermal Loads
Authors: Ching H. K. , Liu C. T. , Yen S. C.
Published: April 2008

In this study, we performed linear and nonlinear FE (Finite Element) analyses to compute J-integrals for a centrally perforated star-shaped disc, which is made of an elastomeric material, under crack surface pressures and isothermal loads. Deformations of the disc were constrained by a circular steel ring enclosing the disc. Different crack sizes were assumed to exist in the front of the star-shaped notches. For linear the analysis, material compressibility was modeled with Poisson’s varying form 0.48 to 0.4999. In addition, with the presence of the crack surface pressure, the J-integral needs to be modified by including an additional line integral. Numerical studies showed that the value of the J-integral increases with the increase of the crack length, reaches a maximum value at 1in of crack length, and then decreases gradually. Both linear and nonlinear analyses agree qualitatively but differ quantitatively. It was also found that values of the J-integral strongly depend upon the material compressibility.
Cycle-to-Cycle Control of Multivariable Manufacturing Processes With Process Model Uncertainty
Authors: Rzepniewski Adam K. , Hardt David E. , Vaughan Chester D.
Published: April 2008

In-process closed-loop control of many manufacturing processes is often impractical owing to the impossibility or the prohibitively high cost of placing sensors and actuators necessary for in-process control. Such processes are usually left to statistical process control methods, which only identify problems without specifying solutions. Cycle-to-cycle control is a method for using feedback to improve product quality for processes that are inaccessible within a single processing cycle but can be changed between cycles. This type of control has the same objectives as run-by-run control. However, it is developed from a different point of view allowing easy analysis of the process’ transient closed-loop behavior due to changes in the target value or to output disturbances. Our previous work introduced cycle-to-cycle control for single input-single output processes and here it is extended to multiple input-multiple output processes. Gain selection, stability, and process variance amplification results are developed and compared with those obtained by previous researchers, showing good agreement. Then, the limitation of imperfect knowledge of the plant model is imposed. This is consistent with manufacturing environments that require minimal cost and number of tests in determining a valid process model. The effects of this limitation on system performance and stability are discussed. The theoretical results are applied to a novel, discrete-die sheet metal stretch-forming process. The classical, monolithic tool is replaced by a large number of small, separate pieces that can be reconfigured between cycles to approximate continuous shapes. Thus, each forming cycle can use a new input shape. The experimental system is an ideal candidate for the application of cycle-to-cycle control in a multivariable fashion. A linear process model is presented that includes the effects of single input-multiple output coupling. Experimental validation of variance amplification results for a sheet metal forming processes is presented with hundreds of inputs and outputs. While many controller designs could be considered a purely diagonal (decoupled) and a Linear Quadratic Regulator design are presented and discussed. Comparison between theory and experiments is provided, showing good agreement.
Joining Dip-Pen Nanolithography and Microcontact Printing Into a Nanolithographic Process: From Engineering Design to Parallel Fabrication
Authors: Johannes Matthew S. , Clark Robert L. , Cole Daniel G.
Published: April 2008

One nanomanufacturing concern is the precise, controlled deposition of materials at the nanoscale, commonly referred to as nanolithography. One promising technique, dip-pen nanolithography (DPN), can deposit a multitude of organic and inorganic materials. Simple and accurate, DPN uses an atomic force microscope (AFM) cantilever to deposit inks under ambient conditions. However, from a manufacturing perspective, DPN’s main drawback is its inherent serial nature. Another more promising technique is microcontact printing (μCP), which can repeatedly cover larger areas in a parallel fashion. As interest in nanomanufacturing processes increases, the demand for user-friendly, automated nanolithography processes become a priority. This paper presents a nanolithography process that begins with a design plan and ends with a manufactured product using a unique progression from design environment to serial nanolithographic technique to parallel nanolithographic technique. The process begins with the creation of a design template using conventional CAD software. The design template is then transformed into a vector signal that serves as input to the AFM used in the DPN process. A custom AFM has been designed for nanometer scale precision in three axes using real-time, digital feedback methodologies. Using the appropriate DPN ‘ink’ coated on the AFM cantilever, the design template is automatically reproduced onto the substrate, where the appropriate features are filled in with predetermined chemical functionalities. Specifically, alkanethiol chemistry is used as a resist for wet chemical etching of a gold substrate to create raised surface features which mimic the original design template. This substrate is used as a positive mask for the creation of polymeric stamps for μCP. These stamps are then used to create replicas of the original design template in a parallel fashion and qualitatively examined for their completeness and reproducibility.
Adaptive Control for Intelligent Open Die Forging
Authors: Liu Wensheng , Nye T. J.
Published: April 2008

Open die forging is a manufacturing process with a number of advantages; in particular it is an inherently flexible manufacturing process that makes efficient use of raw material. A fundamental drawback of this process, however, is the difficulty found in creating forging programs to control part manipulation and forming steps. A-priori approaches to creating these programs, such as by using FEM simulations or using modeling materials, are slow and have a strong tendency for errors to accumulate when predicting the results of consecutive forming steps. In this paper we present a new approach in which process feedback is used between forming steps to update a part geometry model that allows the forming sequence to be adjusted adaptively. This approach has been implemented in a simulated forging cell that uses non-linear FEM analyses to predict the effects of each forming step. A fully adaptive control scheme has been implemented that efficiently forges bars of one cross sectional shape into another shape, such as square to round or hexagonal. Programming the forging system with this scheme has proved particularly simple; the shape of the raw material is measured, and a desired shape is specified. Physical experiments have confirmed the simulation results.
Fluid-Structure Interaction in Finite Element Modeling of Traumatic Aortic Rupture
Authors: Lee Sang-Hyun , Darvish Kurosh , Lobovsky Libor
Published: April 2008

Traumatic Aortic Rupture (TAR) during automobile crashes is one of the leading causes of fatality. In this study, the physical parameters and mechanisms of aortic rupture in dynamic pressure loading condition were investigated using different numerical approaches in a finite element model, including Eulerian, Arbitrary Lagrangian-Eulerian (ALE), and Smoothed Particle Hydrodynamics (SPH) formulations. The TAR models were compared against in vitro experiments and predicted the most probable location of rupture at the isthmus as indicated in the literature.
RF Ablation in a Reconstructed Hepatic Geometry With an Electrical Heat Source
Authors: Hariharan Prasanna , Banerjee Rupak K.
Published: April 2008

This research aims to develop a methodology for modeling three-dimensional radiofrequency (RF) ablation using a reconstructed hepatic vasculature geometry with an electrical heat source. Coupled mass, momentum, heat transfer, and electric field, including voltage potential, equations are solved. The effects of heat convection through the nearby arteries and elevated level of blood perfusion through the tissue on the temperature distribution near the tumor zone is studied. The results show that for an arterial inlet velocity of 13.8 cm/s and 27.6 cm/s the peak tumor temperature drops by 7% and 10%, respectively, whereas the temperature along the outer periphery of the tumor close to the arteries drops by 50% and 75%, respectively. Asymmetries in the temperature profile indicate that the ablation procedure elevates the temperature to the required level only at localized regions. In the other regions the heat energy is not adequate for tumor destruction thereby permitting possible tumor recursion.
Wave Rotor Combustor Test Rig Preliminary Design
Authors: Alparslan Berrak , Nalim M. Razi , Snyder Philip H.
Published: April 2008

Pressure gain combustion in a wave rotor approaching the thermodynamic ideal of constant volume combustion has been proposed to significantly enhance the performance of gas turbine engines. A computational and experimental program is currently being conducted to investigate the combustion process and performance of a wave rotor with detonative and near-detonative internal combustion. An innovative and flexible preliminary design of the test rig is presented to demonstrate the operation and performance of the system. A preliminary design method based on a sequence of computational models is used to design wave processes for testing in the rig and to define rig geometry and operating conditions. The operating cycle allows for propagation of the combustion front from the exit end of the combustion channel to the inlet end. This is similar to and motivated by the Constant Volume Combustor (CVC) concept that seeks to produce a relatively uniform set of outflow conditions in both spatial and time coordinates.
Development of Precision Optical Traps for Single Molecule and Motor Protein Research
Authors: Wulff Kurt D. , Cole Daniel G. , Clark Robert L.
Published: April 2008

Optical traps have become an important instrument for investigating systems and processes at the micro- and nanoscale, particularly within biology where manipulation of biological systems from DNA to cells has offered new insights to cellular processes. Using the inherent momentum of light, particles are trapped in the high intensity field of a focused laser beam thus allowing for the manipulation of microscopic particles. This paper discusses the current development of a state-of-the-art optical trap with increased sensitivity for the measurement of single molecule and motor protein mechanics. A common position sensing technique uses quadrant photodiodes to detect motion on the order of tens of nanometers. However, the measurement of positions and forces on a smaller level than previously attempted requires increased precision. Interferometric techniques provide one method to improve the spatial resolution to the order of nanometers or less. Furthermore, the use of feedback control offers the ability to easily adapt the optical trap to the particular experiment being conducted. In addition, optical traps can apply torque to trapped objects for the study of rotary mechanics when the trapping laser has orbital angular momentum. Methods for generating a laser beam with orbital angular momentum will be discussed.
Failure Identification Methodology for Woven Composites Incorporating Sensor Degradation
Authors: Pearson James , Prabhugoud Mohanraj , Zikry Mohammed , Peters Kara
Published: April 2008

The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling of sensor data fusion with a three-dimensional predictive framework will provide insight and understanding of events that are difficult, if not impossible, in any experimental study, such as subsurface damage and crack nucleation in structural systems. The current work presents an experimental study of the survivability and degradation behavior of an optical fiber Bragg grating sensor, surface mounted on a woven fiber composite material system during multiple low velocity impacts. The results reveal that as sensor degradation occurs, additional coupling phenomena other than Bragg reflection are observed in the grating sensor. From these additional modes, information on the sensor/host bond and fiber degradation is obtained.