bluuebunny/crossref_metadata_2025 huggingface dataset:
Actuation of Shape Memory Polymer by Resistive Heating of Carbon Nanopaper
Authors: Lu Haibao , Tang Yong , Gou Jihua , Chow Erin , Leng Jinsong , Du Shanyi
Published: July 2010

To electrically activate the shape recovery in a styrene-based shape-memory polymer (SMP) by coating with conductive carbon nanofiber paper has been demonstrated in this paper. Carbon nanofibers in the form of paper sheet in combination with SMP significantly improve the electrical and thermal conductivity of polymer, leading to the actuation of SMP/nanopaper composite (with 15% volume fraction of carbon nanopaper, dimension of 10.0 cm × 0.5 cm × 0.3 cm) can be carried out by applying 8.4 V voltage, with response time of 140 s. Therefore, electrical conductivity of 6.6 S/cm is obtained. This approach, although demonstrated in styrene-based polymer, is applicable to other type of SMP materials. Furthermore, the morphologies of carbon nanofiber in the form of paper is observed by scanning electron microscopy, and the thermomechanical properties of composites are measured and analyzed by dynamic mechanical analysis.
Optically Induced Rapid Electrokinetic Patterning: A Study of the Operational Regimes and Dominant Forces
Authors: Kumar Aloke , Wereley Steven T.
Published: July 2010

We study a recently proposed optically induced electrokinetic colloidal particle patterning technique that can pattern/translate or trap particle clusters on an electrode surface using high power laser beams and under an applied AC field. By exploring variations in particle density, with changes in various factors, using Voronoi tessellations we show that the role of various forces changes dramatically with conductivity. For low conductivity (∼2 mS/m) solutions we show that particle density increases with frequency primarily due to a lowering of the induced dipole moment of the particle.
Mode I and Mixed Mode I and II Measurements for Stiction Failed MEMS Devices
Authors: Kashamolla Maheshwar R. , Mousavi Arash K. , Leseman Zayd C.
Published: July 2010

Recently, we have shown that in-service repair of stiction failed MEMS devices is possible with structural vibrations. In order to further understand this phenomenon and better predict, theoretically, the onset of repair we have constructed an apparatus to determine the Mode I, II, and III interfacial adhesion energies of MEMS devices failed on a substrate. Though our method is general, we are specifically focused on devices created using the SUMMiT V process. An apparatus has been constructed that has 8 degrees-of-freedom between the MEMS device, the surface on which the device is failed, and a scanning interferometric microscope. Deflection profiles of stiction failed MEMS (micro-cantilevered beams 1500 microns long, 30 microns wide, and 2.6 microns thick) have their deflection profiles measured with nanometer resolution by the scanning interferometric microscope. Then non-linear elastic models are used in order to determine the interfacial adhesion energy between the failed micro-cantilevers and the surface. In this work we report the interfacial energies from Mode I and Mixed Mode I and II type failures. We also show further experimental results of repair of stiction failed MEMS and corresponding modeling results that use data from the Mode I and II experiments.
Investigation of ZnFe2O4 Nanoparticles Prepared by High Energy Milling
Authors: Srinivasan S. S. , Kislov N. , Emirov Yu. , Goswami D. Y. , Stefanakos E. K.
Published: July 2010

Nanoparticles of Zinc Ferrite (ZnFe2O4) prepared by both wet- and dry- high-energy ball milling (HEBM), have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM), surface area and pore size distribution (BET) and wavelength-dependent diffuse reflectance and scattering turned into absorption coefficient estimation using the Kubelka-Munk theory. It was found that after 72 hours of HEBM, the particle size was decreased from 220 nm for the initial material to 16.5 nm and 9.4 nm for the wet- and dry-milled samples, respectively. The optical absorption analysis revealed that the energy gap is increased (blue shift) by 0.45 eV for wet-milled and decreased (“anomalous” red shift) by 0.15 eV for dry-milled samples of ZnFe2O4 as the particle size decreased.
A Comparison of Coupling Molecular Dynamics to General Finite Elements
Authors: Macri Michael F.
Published: July 2010

In this paper, we assess the ability of three interpolation functions in a discretized continuum model to capture and accurately represent the solution. In particular we examine the differences between the partition of unity, moving least squares and finite element methods in the continuum part of the multiscale model.
Optimization Strategy for Resonant Mass Sensor Design in the Presence of Squeeze Film Damping
Authors: Li Chengzhang , Miller Michele H.
Published: July 2010

This paper investigates the design optimization of an electrostatically actuated microcantilever resonator that operates in air. The nonlinear effects of electrostatic actuation and air damping make the structural dynamics modeling more complex. There is a need for an efficient way to simulate the system behavior so that the design can be more readily optimized. This paper describes an efficient analytical approach for determining the optimum design for a microcantilever resonant mass sensor. One simple case is described. The sensor design is a square plate that is coated with a functional polymer and attached to the substrate with folded leg springs. The plate has a square hole in the middle to reduce the effect of squeeze film damping. With the analytical approach, the optimum hole size for maximum sensitivity is found.
A Multifunctional MWCNT Composite: Strain Sensing, Damping and Application to Structural Vibration Control
Authors: Li Xiaohua , Levy Cesar , Li Ming , Keshri Anup Kumar , Agarwal Arvind
Published: July 2010

The goal of this work is to develop and investigate the properties of a new type of multifunctional composite which is based on multi-walled carbon nanotubes (MWCNT). The composite was prepared from a paper like MWCNT film which was sandwiched between two adhesive layers. Both two point probe and four point probe methods were used to test its mechanical strain sensing properties. The Young’s modulus and shear modulus of MWCNT film composite were acquired by the nanoindentation test and direct shear test. A free vibration test was also performed to investigate its structural damping properties. A new model/configuration for sandwich structural vibration control was then proposed based on the MWCNT experiments results. In this new configuration, a cantilever beam covered with MWCNT composite on the top and one layer of shape memory alloy (SMA) on the bottom was used to illustrate this concept. The MWCNT composite simultaneously serves as free layer damping and strain sensor, and the SMA acts as actuator. Simple on-off controller was designed for controlling the temperature of the SMA so as to control the SMA recovery stress as input and the system stiffness. Both free and forced vibrations were analyzed. Simulation work showed that this new configuration for sandwich structural vibration control was successful especially for low frequency system.
Investigation of a Spectral-Based Surface Contact Model via Pointwise Computations
Authors: Streator Jeffrey L.
Published: July 2010

One of the outstanding issues in the analysis of contacting surfaces regards properly accounting for the multi-scale nature of the surface topography. Many treatments of surface contact, particularly those that derive from the well known Greenwood Williamson (GW) model, proceed from the basis that one can determine a representative curvature of the surface peaks (or summits) by means of computing the appropriate numerical derivative of the sampled profile data. However, as has been demonstrated over the last 20 years or so, numerical derivatives of surface data are sensitive to the lateral spacing between sampled surface points. In view of the potential ambiguity associated with such a determination of peak curvature, a number of models have been put forth that account for the fact that topographical features exist at many scales of observation. In the present work, predictions of a recently developed spectral-based model of elastic (rough) surface contact are compared to those of a deterministic numerical computation in which the equations of elasticity are solved at every nodal point of a 3D surface.
A Comprehensive Quarter-Car Model for Kinematic and Dynamic Analysis of a Suspension
Authors: Balike Krishna Prasad , Rakheja Subhash , Stiharu Ion
Published: July 2010

The conflicting dynamic performances of a vehicle such as ride quality, road holding and rattle space requirements have been widely studied using either linear or nonlinear two DOF quarter-car models. Such models, however, cannot account for contributions due to suspension kinematics and joint compliances. Considering the proven simplicity and effectiveness of a quarter-car model for such analyses, this paper discusses a comprehensive quarter-car dynamic model to study the influences of the linkage geometry and flexible joint bushings on selected performance measures. An in-plane two-DOF model was formulated for a double wishbone suspension comprising an upper control arm, a lower control arm, and a strut mounted on the lower control arm. The dynamic responses of the model were evaluated under harmonic and idealized rounded-pulse displacement excitations. The responses of the proposed model with free and flexible joint conditions were compared with those of the conventional quarter-car model to illustrate the contributions due to suspension kinematics and joint bushings. Owing to the asymmetric kinematic behavior of the suspension system, the dynamic responses of the comprehensive model were also observed to be asymmetric about the equilibrium. The responses of the model with flexible joint bushings revealed approximately 5% variations from that of the model with free joints. Furthermore, the upper control arm bushings have exhibited more significant influence on the dynamic responses than that of the lower control arm bushings.
Experimental Approach for Developing and Testing Predictive Self-Assembly Models
Authors: Hendrick Gary , Tuckerman James , Juha Mario , Crane Nathan
Published: July 2010

Testing methods and apparatus for studying capillary self-assembly processes are presented. This system permits the control of key self-assembly process variables so that relationships between process rates and yields and the process variables can be tested. Part arrival energies and angles are controlled by dropping through a fluid at terminal velocity onto fixed substrate binding sites. Using this system, the assembly probability at the low energy limit is shown to match a simple area fraction relationship.
High Sensitivity Pressure Measurement Using Van der Pauw Structure as a Sensing Element
Authors: Cassel R. , Mishty A. , Mian A.
Published: July 2010

In this paper, we presented is a four-terminal piezoresistive sensor commonly referred to as a van der Pauw (VDP) structure for its application to MEMS pressure sensing. In a recent study, our team has determined the relation between the biaxial stress state and the piezoresistive response of a VDP structure by combining the VDP resistance equations with the equations governing silicon piezoresistivity and has proposed a new piezoresistive pressure sensor. It was observed that the sensitivity of the VDP sensor is over three times higher than the conventional filament type Wheatstone bridge resistor. To check our theoretical findings, we fabricated several (100) silicon diaphragms with both the VDP sensors and filament resistor sensors on the same wafer so both the sensor elements have same doping concentration. The diaphragms were subjected to known pressures, and the pressure sensitivities of both types of sensors were measured using an in-house built calibration setup. It was found that the VDP devices had a linear response to pressure as expected, and were more sensitive than the resistor sensors. Also, the VDP sensors provided a number of additional advantages, such as its size independent sensitivity and simple fabrication steps due to its simple geometry.
Preparation and Characterization of Porous Magnesium Alloys in Biomedical Applications
Authors: Xu Zhigang , Linford James , Chen Shuo , Smith Christopher , Sankar Jag
Published: July 2010

Porous magnesium (Mg) alloys were processed by solid state sintering from mixture of elemental metal powders and pore-filling materials, such as, carbamide (urea). The porosity of the Mg alloy was controlled by selecting different particle size of the pore-filling and volume fraction material, as well as the sintering condition, which were arranged by a factorial experimental design. The effects of their porosity and porous structure were analyzed and the mechanical strength was evaluated with compression tests.
Combustion of Methane in Microchannels
Authors: Loire Sophie , Mezic´ Igor , Fonoberov Vladimir A.
Published: July 2010

The interest in micropower generation using the high energy density provided by hydrocarbon fuels as a portable power and heat source has stimulated research on combustion in microdevices. As the length scale of a combustion channel is decreased, the surface area-to-volume ratio increases approximately inversely with the critical dimension. The resulting high surface heat loss is a limiting factor to the size of a microcombustor. However when using arrays of micro-combustors, some of the surface heat loss in a channel becomes heat source for its neighbors. Combustion of methane/air mixture in an array of channels is studied as a function of gas velocity and distance between channels and is compared to the case of a single channel. Arrays of channels are shown to have self-sustained combustion when no such combustion is possible in a single channel.
Numerical Simulation of Hollow Fiber Ultrafiltration Membrane
Authors: Zhou Nina , Nnanna A. G. Agwu
Published: July 2010

Low pressure driven ultrafiltraion (UF) processes has been applied in various industries due to its economical and easy operated benefits. Hollow fiber membrane is one of the most used membrane configuration in industry, membrane fouling is the major challenge for widely usage. Most of the investigation of UF was carried out by experiments to determine the effect of different operating conditions on permeate flux. However, experiments provide limited insight information on the membrane performance. In addition, the prediction of permeate flux under different operating conditions is necessary for experimental design and optimization. The purpose of the present study is to develop a numerical model to simulate the UF process and investigate the UF mechanism. A numerical model was developed using commercial CFD package (FLUENT). The effects of various operating conditions on permeate flux were determined by experiments and simulations, the comparison of the experimental and CFD results shows good agreements. Controlling membrane fouling will maintain a high productivity. The simulations were carried out to investigate the efficiency of removing accumulated particles on membrane surface by installing spacer filaments in membrane channels. The results suggested that the zigzag type spacer has d/h = 0.5 and l/h = 5 is more economical and efficient in reducing fouling.
Interfacial Fracture Analysis in EB-PVD/PTAL TBC Systems
Authors: Ma Q. , Beuth J. L. , Meier G. H. , Pettit F. S.
Published: July 2010

Thermal barrier coatings (TBCs) have been utilized for more than four decades to increase the efficiency and durability of aircraft engines as well as land based gas turbines. Though the function of the thin TBC layer is heat insulation, it is critically important for it to maintain adherence in service. In this paper, we address some fundamental aspects of TBC debonding failure in electron beam physical vapor deposition (EB-PVD) TBC systems that had been considered in a previous study. We demonstrate that the energy release rate formulation for EB-PVD TBC systems based on as-processed conditions and a thin thermally grown oxide (TGO) layer overestimates the energy release rate for exposed TBC systems having thicker TGO layers. A modified formulation is given, applicable to exposed TBC systems. A finite element contact and fracture model is used to validate the formulation as well as study crack mode mixity. Mode II interfacial cracking is shown to be dominant for practical TGO thicknesses seen in exposed EB-PVD TBC systems.
A Shape Memory Alloy Controlled Heat Pipe Based Thermal Switch
Authors: Benafan Othmane , Vaidyanathan Raj
Published: July 2010

This work reports on the design, fabrication and testing of a low temperature shape memory alloy thermal switch for meeting NASA’s thermal management needs on the surface of the moon. The switch is designed to provide on demand heat transfer to cool a liquid oxygen tank while the temperature of the surrounding space environment varies from 40 K to 400 K on the lunar surface. NiTiFe shape memory helical actuators are the sensing and actuating elements in the switch. Heat transfer is accomplished via heat acquisition, transport and rejection in a variable length heat pipe with pentane and R-134a as working fluids. The approach used to design the shape memory elements, quantify the heat transfer at both ends of the heat pipe and the pressures and stresses associated with the actuation are outlined. Testing of the switch is accomplished in a vacuum bell jar with instrumentation feedthroughs, using valves to control the flow of liquid nitrogen and heaters to simulate the temperature changes. Various performance parameters are measured and reported under both transient and steady-state conditions.
Fly-Ear Inspired Miniature Directional Microphones: Modeling and Experimental Study
Authors: Liu H. J. , Yu M. , Currano L. , Gee D.
Published: July 2010

To address the challenges in developing miniature directional microphones, a novel micro-fabricated directional microphone inspired by the superacute ears of the parasitoid fly Ormia ocharacea is presented in this paper. It consists of two clamped circular silicon diaphragms structurally coupled by an oxide/nitride composite bridge. The separation between the diaphragm centers is 1.25 mm, about the same size as the fly ear. A finite element model is developed to achieve a better understanding of the microphone device and guide the optimal design of the miniature microphones. Using a low coherence fiber optic interferometer detection system, the experiment shows that the directional sensitivity of this device is equivalent to a conventional microphone pair that is 9 times larger. Validating the feasibility to replicate the fly ear in a man-made structure, this work is expected to significantly impact many different fronts that require miniature sensors for sound source localization.
Characterization of Ultrathin Membranes to Enable TEM Observation of Gas Reactions at High Pressures
Authors: Alan Tuncay , Gaspar Joao , Paul Oliver , Zandbergen Henny W. , Creemer Fredrik , Sarro Pasqualina M.
Published: July 2010

In-situ, atomic scale imaging of chemical reactions at high gas pressures and elevated temperatures is crucial to characterize structural changes in catalysts. To enable transmission electron microscopy (TEM) imaging in realistic environments, a MEMS device that confines the gas flow and reactions to a micromachined channel was developed. The device consists of two parts that were brought into contact to form a channel. At the central part of the structure there is a large square region containing several 10–15 nm thick membranes that act as electron transparent windows, hence, allowing TEM imaging. The present design was previously demonstrated to sustain 0.1 MPa pressure, yet, to accurately mimic industrial conditions, the device should survive gas pressures as high as 1 MPa. In this article, we study the mechanical performance of individual components using simulations and nanoscale bulge tests and determine the necessary modifications to improve device functionality.
Nano-Structured Phase Change Materials and Their Calorimetry
Authors: Baris Oksen T. , Sinha Sanjiv
Published: July 2010

Phase change materials (PCMs) store thermal energy through a phase transition. Extending the use of PCMs to transient thermal management of electronic handheld devices requires storage capacity beyond 195 kJ/m3, typical limit of a paraffin. Nano-structures can potentially increase the material choice for PCMs. Melting behavior and heat of fusion are empirically known to be altered in nano-structures. In this paper, we present thermodynamic modeling to show that confinement can lead to an enhancement in the heat of fusion of soft matter. We present material concepts that can serve as such enhanced PCMs. We also discuss modifying existing calorimetry techniques to measure the heat capacity of nanometer scale thin films of soft matter. Design and sensitivity details of nano-calorimeter are presented to analyze phase change phenomenon in ultra-thin polymer films.
Micro-Visualizing Assay of Drug Delivery System Using 2-Color Optical Coherence Dosigraphy
Authors: Nakamichi Yu , Saeki Souichi , Saito Takashi , Hiro Takafumi , Matsuzaki Masunori
Published: July 2010

2-Color Optical Coherence Dosigraphy, which could visualize micro-scale drug infiltration, was applied to lipidrich plaques of rabbit with drug administration. Calculated distributions of absorption coefficient had good coincidence with drug infiltration into tissue. Therefore, 2C-OCD has a promising modality for micro-visualizing assay of drug delivery system.
Corrosion Detection/Quantification on Thin-Wall Structures Using Multi-Mode Sensing Combined With Statistical and Time-Frequency Analysis
Authors: Yu Lingyu , Giurgiutiu Victor , Wang Jingjiang , Shin Yong-June
Published: July 2010

In this paper, we present a multiple mode sensing methodology to detect active corrosion in aluminum structure utilizing the broadband piezoelectric wafer active sensors. This method uses ultrasonic Lamb wave complemented with the electromechanical impedance measurement to detect, quantify, and localize the corrosion progression in plate-like structures. The ultimate objective of this research is to develop in-situ multimode sensing system for the monitoring and prediction of critical aerospace structures that can be used during in-service period, recording and monitoring the changes over time. The test experiments were conducted on an aluminum plate installed with a five sensor network using 7-mm piezoelectric wafer active sensors. The corrosion was emulated as material loss of an area of 50mm 38mm on the other surface of the plate. Detection of corrosion and its growth was first conducted using the Lamb wave method in pitch-catch mode. The corroded area resulted in a thickness loss on the Lamb wave propagation and caused the amplitude and phase changes in the structural responses. The experimental data was first evaluated by the statistics-based damage indicator using root mean square deviation. Though the damage indicator is able to detect the presence of the corrosion and identify the corrosion location quantitatively, it failed in giving the right indication of corrosion development. A more corrosion signal processing based method, the cross time-frequency analysis, was proposed and used to analyze the phase characteristics of the data set. This cross time-frequency analysis was found more reliable and precise for detecting the corrosion progression compared with the damage indicator method.
3-D Integration of Micro-Gratings Into Bio-Analytical Devices
Authors: Farshchian Bahador , Ok Jeong Tae , Lee JaeJong , Park Sunggook
Published: July 2010

The ability to produce three-dimensional micro- and nanoscale features at low cost is desirable for many applications such as microfluidic devices, micro and nanomechanical systems, photonic crystals and diffractive optics. For example, micro and nanostructures patterned on the sidewalls of microfluidic devices allow better control over the wetting behavior of fluids flowing through the microchannel. In this study we report on a simple and effective process that allows direct integration of microstructures into a microfluidic device via a modified molding process. The key for the process is to use a thin poly(dimethylsiloxane) layer having microgratings as an intermediate stamp which was placed between a brass mold insert with microfluidic features and a PMMA sheet, which was followed by hot embossing. Using this method, we have demonstrated the formation of micropatterns on non-planar surfaces and at the sidewalls of microfluidic devices, as confirmed using scanning electron microscopy. The designed process will fill the gap in current micro- and nanofabrication technologies in that most of the technologies allow for patterning only on planar substrates.
Investigation and Measurement of Electrical Transport of Metal Particle Polymer Composites for the Development of MEMS-Based Corrosion Sensor
Authors: Pan Feng , Huang Adam
Published: July 2010

Recently, our research group has proposed a MEMS-based solid state corrosion sensor based on the carbon black and metal particle polymer composite materials. The chemical and dimensional properties of the particles and polymer matrix will provide the tailorability in sensor sensitivity, selectivity, time response, and operating life-span. This paper will analyze the electrical resistivity of the sensor relative to the percentage of different type of particles in PDMS matrix in order to understand the effect of corrosion mechanism on metal particle polymer composites. This paper will also present the electrical quantification techniques for the micro corrosion sensors, the understanding of which is need for the transduction from corrosion to electronic output. Electronic transduction is the natural form of output due to the redox reactions of the electrochemical corrosion of particles and the electric current generated is directly proportional to the rate of the reaction.
Thermoplastic Fusion Bonding of Polymer-Based Micro Devices Using a Pressure Cooker
Authors: Park Taehyun , Zimmerman Thomas J. , Park Daniel , Lowrey Brooks , Murphy Michael C.
Published: July 2010

A novel method of thermoplastic fusion bonding (TPFB), or thermal bonding, for polymer fluidic devices was demonstrated. A pressure cooker was used in a simple sealing and packaging process with precise control of the critical parameters. Polymer devices were enclosed in a vacuum-sealed polymer container. This produced an even pressure distribution and a precise temperature boundary condition over the whole surface of the device. Deformation indicators were integrated on the devices to provide a rapid means of checking deformation and pressure distribution with the naked eye. Temperature, pressure, and time are the fundamental parameters of TPFB. The temperature and pressure are dominated by the material and contact area of the device. The temperature and pressure can be manipulated by controlling the water vapor pressure. The boiling solution guarantees an accurate, constant temperature boundary condition. Time can be eliminated as a variable by choosing a sufficient time to achieve good bonding, since there was no apparent damage to the microstructures after one hour. This new method of TPFB was demonstrated for sealing and packaging a PMMA (polymethylmethacrylate) microfluidic device. Good results were obtained using the vacuum sealed polymer container in the pressure cooker. This method is also suitable for scaling up for mass production.
On the Effect of Uncertainty Factors on Mechanical Behavior of Woven Fabric Composites at Meso-Level
Authors: Komeili Mojtaba , Milani Abbas S.
Published: July 2010

Unit cell modeling of woven fabric composites at meso-level has been advantageous in finding equivalent mechanical properties of different weave architectures without performing physical experiments on each new fabric. The obtained properties, in turn, can be used in the macro-level modeling and simulation of large composite structures. Models used for this purpose, however, often consider a perfect description of unit cells, while in practice fabrics are not always fabricated under ideal conditions and flaws like fiber misalignment, material and/or geometrical defects are present. A benchmark work covering effects of this kind on the mesoscopic behavior of woven fabrics is underway. The aim of this paper is to present a statistical way to approach the problem by studying the main effects of such uncertainty/noise factors along with their levels of significance. Namely, a one-factor-at-a-time screening method is selected to identify the effect of (1) fiber misalignment, (2) fiber modulus variation, (3) geometrical flaws in yarn section, (4) unpredictable friction between weft and warp yarns. Computer experiments are done using FE modeling of a plain weave unit cell under the uniaxial, equibiaxial, and trellising (shear) modes. A parameter sensitivity analysis is conducted to identify the most significant factors and the extent to which each can independently contribute to the variation of load-displacement curves (i.e., testing data non-repeatabilities).
Surface Acoustic Waves in Piezoelectric Half Space With Periodic Surface Electrodes
Authors: Lai Chien-Hsun , Chou Yuan-Fang
Published: July 2010

Surface acoustic waves of piezoelectric half space with periodic surface electrodes are investigated. Since the boundary has periodic character, Bloch’s theorem and plane wave expansion method are employed in the analysis. Modeling the periodic electrode’s mechanical effects and electric boundary conditions of short grating and open grating are major tasks. Verification is performed on a 128°YX-LiNbO3 substrate covered by aluminum electrodes. Cases of different electrode aspect ratios are also investigated. Comparisons of dispersion curves corresponding to different boundary conditions are given. The effect of electrode aspect ratio on band gap width is obvious. The developed solution scheme finds the dispersion relations and propagation modes very efficiently and accurately.
Numerical Simulation of the Combined Wave-Current Force Distributions on Large-Scale Underwater Objects
Authors: Zhao Lin , Yin Zegao , Sun Miaomiao , Ma Jian
Published: July 2010

In the design of undersea oil tanks, the computation of stability and the structural analysis needs parameters regarding the combined wave-current force on the surfaces of these large-scale objects. In this paper, numerical simulation is employed to calculate the wave-current forces on the circular surfaces along the whole depth with Fluent software. The calculation uses RNG k-ε model, VOF method and dynamic meshes to finish the task, with the selected water depth and wave and current elements similar to those of Chinese Bohai Bay. The computational results find drag forces, lift forces as well as composite forces shift periodically in coincidence with the wave periods, among them, the lift forces have bigger and more stable values than the drag forces, and have more strong effects on the composite forces.
Spot Locator for Autonomous Parking
Authors: Moshchuk Nikolai , Chen Shih-Ken
Published: July 2010

For a semi-autonomous or fully-autonomous parking system, detecting adequate parking spot is the first step. Ultrasonic sensor possesses a good compromise between cost and performance since the detection range is very small. This paper describes a parking assist system with two ultrasonic sensors mounted at the left front and right front corners of the vehicle. Special signal filtering and processing is derived. Kinematic observer for the vehicle position estimation during search and parking phases is discussed. The suggested algorithm is implemented in Matlab/Simulink and was verified in a test vehicle.
Isoelectric Focusing-Reversed Phase Liquid Chromatography Polymer Microchip With Integrated High-Pressure Valves
Authors: Liu Jikun , Chen Chien-Fu , Chang Chien-Cheng , DeVoe Don L.
Published: July 2010

A cyclicolefin polymer (COP) microchip supporting parallel 2-D peptide separations is described. By combining isoelectric focusing (IEF) as a first dimension and parallel reversed-phase liquid chromatography (RPLC) as a second dimension, the system enables efficient high-throughput fractionation prior to mass spectrometry in support of peptide mass fingerprinting for global proteomic analysis from highly limited specimens. The IEF-RPLC chip incorporates high-pressure micro shut-off valves, allowing uniform sample transfer and gradient elution from each micro LC column, and ensuring hydrodynamic isolation between the separation dimensions. The utility of the initial microchip is demonstrated by separation of a fluorescein labeled bovine serum albumin tryptic digest in a chip containing a five channel RPLC array.
New Shallow Foundation Security Barriers for Urban Applications: FEA and Certified Actual Crash Test
Authors: Omar Tarek A. , Bedewi Nabih E.
Published: July 2010

Providing an accurate and reliable design or analysis of complex physical security systems has been a great challenge for several years. To meet this challenge, the latest and most advanced engineering techniques proved to be necessary. Among them is the Finite Element Analysis (FEA) computational method. FEA is recognized today within the engineering and scientific community to be a very powerful tool in solving the most complex structural analysis, crash and impact-related problems. Due to the significant improvements in computer technology and software developments, FEA can now provide excellent support to the design, analysis, evaluation and improvement of all security barriers. In the current research, a new shallow-foundation bollard system design has been conceived and analyzed using nonlinear FEA. This design is appropriately suitable for urban applications since its foundation is a mere 18 inches deep and can be installed within a few hours. Further optimization led to the utilization of the most appropriate commercial steel-structural elements with the objective of reducing material, manufacturing and installation costs. The system has proven to be capable of sustaining severe impacts by spreading a portion of the induced energy throughout the entire structure and the supporting soil/concrete. This was possible through a process of FEA iterations that resulted in the refinement of the initial bollard concept. Subsequently, a five-bollard full-scale module was constructed and tested under K12 impact conditions as defined by the Department of State (DOS) guidelines (SD-STD-02.01). According to the DOS guidelines, a K12 rated barrier must be able to stop a 15,000 lb single unit truck at an impact speed of 50 mph. The system successfully stopped the truck with negative cargo penetration and less than 5 inch bollard deformation. In the final step, the FE model of the tested bollard system was validated by simulating the crash at the exact test speed (47.4 mph). The FE simulation results showed excellent correlation with the actual test output.
Nonlinear Thermoelastic Stress Analysis of the Rotating FGM Disk With Variable Thickness and Temperature-Dependent Material Properties Using Finite Element Method
Authors: Azadi Mohammad , Damircheli Mehrnoosh
Published: July 2010

In this paper, nonlinear radial and hoop thermoelastic stress analysis of rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using the finite element method. In this method, one-dimensional second order elements with three nodes have been used. The geometrical and boundary conditions are in the shape of nonexistence of the pressure (zero radial stress) in both external and internal layers and zero displacement at the internal layer of rotating disk. Furthermore, it’s assumed that heat distribution is as second order curve while material properties such as elasticity modulus, Poisson’s ratio and thermal expansion coefficient vary by using a power law versus radius of the disk and also vary with the temperature. In a numerical example, the displacements and stresses for various powers (N) and the angular velocities have been calculated in according to the radius. It’s obvious that by increasing the values of the power (N) and the angular velocity, the value of displacements and stresses will be increased consequently. Finally, the effect of varying the thickness and the dependency and in-dependency of the material properties on the temperature has been considered.
Fatigue Analysis of Antiroll Bar for Periodic and Random Inputs Using Various Theories and Introducing a New Method
Authors: Azadi Mohammad , Zahedi Farshad
Published: July 2010

In the present paper, fatigue analysis of an antiroll bar is investigated and compared for several criterions by using the finite element method (FEM) and also the experimental results. The validity of some of commonly used criterions in estimating fatigue life including Mcdiarmid and Von Misses theories is examined in which the inputs are considered as periodic data. For random inputs, some other methods are proposed including new suggestions and also a new criterion are established for estimation of fatigue life based on Mcdiarmid and Von Misses criterions. Prediction capability of mentioned new criterion which is evaluated for the antiroll bar, shows better results than other methods proposed in this literature. The proposed method is shown to provide good approximations of fatigue life.
Evaluation of the Pumping Action of a Barrel-Shaped Composite Shell Structure
Authors: Ghoneim Hany , Santos Tiago
Published: July 2010

This paper evaluates the pumping-action potential of a flexible-matrix-composite barrel-shaped shell-of-revolution structure. The pumping-action potential is defined by the relative radial reduction due to a specific applied axial stretching. The fundamental concept of the investigated pumping action is based on the phenomenon that angle-ply fibrous flexible-matrix-composites, with fiber angle orientation of [±θf], can exhibit unprecedented high values of the in-plane Poisson’s ratio. Consequently, upon stretching an angle-ply flexible-matrix-composite axisymmetric shell-of-revolution structure, a substantial reduction in its diameter can be realized and a potential pumping action is provided. In the current paper, the effect of the large deformation on the pumping action of a barrel-shaped (concaved-out) shell-of-revolution composite structure is evaluated. A mathematical model governing the large deformation of an axisymmetric barrel-shaped shell-of-revolution flexible-matrix-composite structure is presented and the response due to axial stretching, for different barrel curvature (maximum diameter), is found using the B-spline collocation numerical technique. In addition, a limited, preliminary experimental work is presented. A carbon/polyurethane barrel-shaped shell-of-revolution structure is constructed, and tested using the Tinius-Olsen testing machine. The crude preliminary results are compared with the corresponding analytical ones, and a discussion of the analytical/experimental results and their implications are addressed. The investigation demonstrates that a barrel-shaped angle-ply flexible-matrix-composite shell structure possesses a relatively high pumping potential.
Side Branch Interaction With Main Line Standing Waves and Related Component Load Definition
Authors: Ruggles Arthur , Moore Eric M. , Shehane Michael , Zhang Bi Yao , Sparger John
Published: July 2010

Side branch resonance can cause standing waves in the main line. The main line standing wave modifies the acoustic boundary condition between the side branch and the main line. This interaction leads to drift in the side branch resonant frequency, and to sensitivity in the side branch and main line resonant amplitude as a function of branch position along the main line standing wave. In many cases the mainline standing wave is not stationary, leading to temporal modulation of the side branch frequency and amplitude. These features are examined using novel signal interrogation techniques that expose frequency and amplitude variation in time. Data from a low pressure air test facility are used to reinforce the theory and demonstrate the system behavior. Finally, the connection between the dynamic pressure signal features and methods for main line and branch component endurance prediction is developed. Components such as steam dryers, safety relief valves, and heat exchangers would be candidates for endurance prediction using these methods.
Structural Vibration as a Noise Source on Vibrating Screens
Authors: Yantek David S. , Camargo Hugo R.
Published: July 2010

A-weighted sound levels around vibrating screens in coal preparation plants often exceed 90 dB(A). The National Institute for Occupational Safety and Health (NIOSH) is actively developing noise controls to reduce noise generated by horizontal vibrating screens. A 121-microphone, 3.5-meter-diameter array was used to perform beamforming to determine locations of significant noise radiation on the screen. Below about 1 kHz, the screen body was found to be the most significant noise source. The beamforming contour maps showed several key locations on the sides of the screen and the feedbox are the most significant contributors. Operating deflection shape (ODS) analysis was used to examine the screen behavior under actual operating conditions. This information is helpful in determining how to modify the screen body to reduce the noise radiated by the screen below 1 kHz. The analysis showed modal vibration patterns on the sides and feed box were the main contributors to noise. The results show several areas on the screen sides and feedbox that can be modified to reduce noise.
Non-Destructive Testing of Fiber Reinforced Composite Materials Using a Capacitance Bridge
Authors: Asmatulu R. , Venishetty B. , Asmatulu E.
Published: July 2010

Fiber reinforced polymeric composites are used in many applications due to their uniqueness, and the ability to tailor specific properties to satisfy necessary requirements. Like many other materials, composites are susceptible to defects, which may significantly degrade their physical properties. Hence, fiber-reinforced polymeric composites should be tested both prior and during the life of the part to ensure that defects are either not present, or are not severe enough to compromise the integrity and performance of the materials. Composites, however, present a unique challenge to non-destructive testing because of their non-homogenous structure, and the wide variety of materials that are used in the manufacturing process. This study deals with the non-destructive testing of glass fiber reinforced composite materials using a capacitance bridge. The major advantage of using this method is that we can simultaneously determine voids, cracks and moisture uptake, which may occur during manufacturing and the usage of the composites.
Temperature and Humidity Effects on the Mechanical Properties of Polymeric Nanocomposites
Authors: Asmatulu R. , Gokathoti S. , Liao H. , Yip C.
Published: July 2010

An environmental testing was conducted on polymeric nanocomposites fabricated by dispersing the carbon nanotubes (CNTs) into polymeric epoxy resins in order to determine their shelf life, reliability, stability, as well as other property changes as a function of temperature and humidity. In this study, various multi wall CNTs (∼140 nm diameter and ∼7 μm length) ranging from 0.5% to 2.0% were initially dispersed in ethanol using a magnetic stirrer, and then an epoxy resin was added to the mixtures under continuous stirring. When the solvent completely evaporated after 18 hours of stirring, a hardener was added to the dispersion. The mixtures were then poured into rectangular shape molds and cured for 48 hours at the room temperature and pressure. Furthermore, a few samples of plain epoxy without nanotubes were also cast for comparison purposes. Dog-bone specimens were tested on a tensile testing machine after different hours of degradation in an environmental chamber. The experimental results showed that the yield stress, ultimate tensile strength and modulus of elasticity gradually reduced over time, indicating that nanocomposites were highly dependent on the humidity and temperature conditions. The results provide a useful guideline for a variety of applications of the nanocomposites in the future.
Fabrications of CNT Based Nanocomposite Fibers From the Recycled Plastics
Authors: Asmatulu R. , Davluri S. , Khan W.
Published: July 2010

Electrospinning is a viable technique that spins fibers at different diameters starting from 3 nm to several micron meters. This technique allows the fabrication of random and aligned fibers of diverse structures, such as ribbon or cylindrical shapes. In this work, the spinning solution is prepared by dissolving recycled polystyrene and the mixture of polystyrene and polyvinyl chloride along with carbon nanotubes in dimethyl acetamide (DMAc). The dispersions were then electrospun at various DC voltage, pump speed, concentration and distance. The general morphology of the fibers has been studied by scanning electron microscopy (SEM). The test results confirmed that fiber diameter and surface roughness were increased by increasing the CNTs, which may be because of the viscosity increase of the spinning solution. Addition of carbon nanotubes in the polymer solution also improves the thermal and electrical conductivity, as well as toughness, stiffness and other properties.
Acoustical Properties of Electrospun Nanofibers for Aircraft Interior Noise Reduction
Authors: Asmatulu R. , Khan W. , Yildirim M. B.
Published: July 2010

Electrospun micro and nanofibers produced via electrospinning method were used for the sound absorption purposes. Polymers were initially dissolved in dimethyleformamide (DMF) or ethanol with a ratio of 80:20 and electrospun at 20 kV, 20 cm separation distance and 3 ml/hrs pump speed. The two-microphone transfer function method of the B&K impedance tube was used to determine the acoustical properties of the manufactured nanofibers at various frequencies. The test results showed that the absorption coefficients of nanofibers (∼500 nm) drastically increased. The reason behind this phenomenon may be attributed to the higher surface area of nanofibers and their interactions with more sound waves/air molecules. This result may open up new possibilities for the sound absorption problems in many fields, such as aircrafts, other transportation vehicles and infrastructures.
Study of Impact Behavior of a Composite Graded Cellular Structure
Authors: Ali M. , Miller J. , Takak S.
Published: July 2010

The research study presented in this paper is a continuation of work done in analyzing the impact response of functionally graded cellular structure of a banana peel for energy absorbing applications. A composite graded cellular structure composed of three different materials is modeled in ABAQUS. The effects of composite sections on energy absorbing characteristics, e.g. deformation mode, crushing stress, stroke, acceleration pulse etc., are studied. An analytical model developed in previous study [1, 2] is used to simulate the quasi-static and dynamic crushing behavior of the composite structure. An agreement is found between finite element analysis and the analytical model.