bluuebunny/crossref_metadata_2025 huggingface dataset:
Repeatability Analysis on the Tool Point Dynamics for Investigation on Uncertainty in Milling Stability
Authors: Lee Kang-Jae , Donmez M. Alkan
Published: May 2009

Stability analysis is needed to maximize milling performance while avoiding chatter. However, such an analysis is time-consuming, requiring the use of sophisticated instrumentation, and has significant level of uncertainty, which impedes the widespread use by industry. A main source of uncertainty is believed to be the changes in dynamics of the tool-holder-spindle system during the milling operation. This study investigates the variation in the tool point dynamics reflecting the dynamics of the tool-holder-spindle system and associated machining stability. The investigation focuses on the effects of the conditions generated by typical milling operations, such as tool changes and spindle warm up. The results of analyses demonstrate the necessity of continuous updates of the tool point dynamics during milling process by in-situ measurements to minimize uncertainty in evaluation of machining stability.
An Analytic Model for PTH/PWB Stress Due to Three-Dimensional Forces Generated by Symmetric Compliant-Pins
Authors: Roettele S. , Dasgupta A.
Published: May 2009

Analytical models are presented, to address the deformations and stresses caused in PWBs by compliant-pins used for solder-less component-interconnection technologies. These models are proposed for rapid-assessment capabilities when designing such interconnect assemblies for reliability. This model is based on mechanistic understanding of the physics of the pin insertion process. Previous studies in the literature focused on analytic solutions for the in-plane (radial and tangential) forces generated in the PWB & PTH due to the compliant-pin. In this study, the approach is extended to three-dimensional solutions by approximately including the axial forces generated by friction during the compliant-pin insertion process. The solution is linear elastic and is based on Fourier series expansions of the contact forces generated by the compliant-pin. This approximate solution therefore is appropriate for rapid-assessment capabilities for parametric trade-off studies and design guidelines. Model parameters include PWB hole-diameter, PTH plating thickness, and the PTH and PWB material properties. The model can be used with any mirror-symmetric compliant-pin geometry and stiffness. The numerical predictions allow us to quantify the dependence of the stresses in the PWB on compliant-pin geometry and on the PTH construction.
Vibration Durability Assessment of Sn3.0Ag0.5Cu and Sn37Pb Solders Under Harmonic Excitation
Authors: Zhou Yuxun , Dasgupta Abhijit
Published: May 2009

In this paper, the vibration durability of both SAC305 & eutectic SnPb interconnects is investigated with narrow-band harmonic vibration tests and finite element simulation. The tests are conducted at the first natural frequency of the test board using constant amplitude excitation. Compared to broad-band vibration durability test, the advantage of harmonic test is less complexity, hence, less uncertainty in the desired fatigue constant. A time-domain approach, reported in the literature 0, was adapted in this study for the fatigue analysis. The test board consists of daisy-chained components, to facilitate real-time failure monitoring. The tests are conducted at different loading amplitude to obtain the durability data points located at both low cycle fatigue and high cycle fatigue region. The SAC305 solder was found to have lower fatigue durability than the SnPb solder, under narrow-band harmonic excitation, which is consistent with results from broad-band vibration test 0, as well as with results of mechanical cycling studies and repetitive mechanical shock studies conducted earlier 0. The test board was first characterized before the vibration durability test. A modal test was conducted to determine the mode shape and natural frequency, which were used to decide the excitation frequency of durability test. Flexure strain amplitudes at critical locations on the PWB were first characterized with strain gages at each level used in the test excitation. Detailed local finite element analysis was then conducted to estimate the strain transfer function between the PWB flexure strain and the strain in the critical solder joints for selected components (BGA256, LCR1210 and LCR2512). Then the strain history in the critical solder joint was estimated from the measured PWB strain, using the strain transfer function. Finally the solder strain and the measured time-to-failure data were used to estimate durability model constants for a generalized strain-life fatigue model 0 for both SAC305 and eutectic SnPb solder. Destructive failure analysis (cross-sectioning, polishing and microscopy) was used to confirm that the failure was by solder fatigue.
Numerical Study of Time Domain Approach Applied to the Prediction of Noise Radiation From Rotating Blades
Authors: Tellier G. , Fedala D. , Kouidri S. , Rey R.
Published: May 2009

Aeroacoustic formulations in time domain are frequently used to model the aerodynamic sound of airfoils, the time data being more accessible. The formulation 1A developed by Farassat, integral solution of the Ffowcs Williams and Hawkings equation, holds great interest because of its adequacy for surfaces in arbitrary motion. The aim of this work is to study the numerical sensitivity of this model to specified parameters and the geometry used in the calculation. The numerical algorithms, spatial and time discretizations, and approximations used for far-field acoustic simulation are presented. A parametrical study of the relevant criteria is carried out based on the Isom’s and Tam’s test cases. A helicopter blade airfoil as defined by Farassat to investigate the Isom’s case is used in this work. According to Isom, the acoustic response of a dipole source with a constant aerodynamic load ρ0c02 is equal to the thickness noise contribution. In practice, this observation is subject to numerical errors that are not systematically well controlled. Variations of these errors depending on the time step, Mach number and the source-observer distance are studied. The analysis is then extended to the Tam’s test case. Tam test case has the advantage of providing an analytical solution for the first harmonic.
Introduction of Nanotechnology in the Basic Energy Sciences
Authors: Wong Kau-Fui V. , Garcia Pablo A.
Published: May 2009

Nanotechnology is, according to some authorative sources, the new wave of the immediate future in science and technology. Many universities in the world do not have this topic taught at the college level in engineering. The objective of the current work is to prepare teaching materials in nanotechnology that could be used in a couple of lectures to be incorporated in a junior-level course of thermodynamics or other basic energy science course. The aim of preparing these modules is an effort to introduce our current undergraduate engineering students to some important concepts in nanotechnology. The modality of modules is so that many other college programs in the world can adopt these modules and incorporate in their curriculum easily; the result is that the education of our future engineers will be more complete and our engineers more competitive in the world market. The current work concentrates on the discussion and elaboration of the topics to be covered in nanotechnology in two one-hour and a-half lectures. Introductory items include the differences between nano-science and macro-science as well as atomic-level science theory. It cannot just be a survey of where nanotechnology has affected our modern lives. It should contain enough basics so that future courses/topics can build on these preliminary foundation lectures. The topics will tie in two existing lectures with nanotechnology applications. First, the principles of heat transfer relating to thermodynamics will be introduced. Second, an overview of nanotechnology will be presented. Third, students will be given an in-depth look at the various heat transfer processes. Finally, the nanotechnology applications relating to heat transfer shall be discussed, including a focus on nanofluids. This work will introduce some of the fundamental ideas regarding nanotechnology that relates to the energy sciences as it may be presented to a junior-level engineering class. This will include a discussion of some of the properties of nanoparticles, the synthesis of nanoparticles and the various materials used in fabrication, as well as the importance of nanofluids to complex thermal energy systems based on current and past research. After laying out the lesson plan integration in the current course curricula, several sample problems are presented in the appendix that would lend the students a greater grasp of the new material. An engineering upperclassman should understand the fundamentals of nanoscale engineering. Initial educational evaluation data based on a couple of lectures alone gave an average concept inventory, ([1] C.I., Foundation Coalition, 2007) score (geared for the two lectures) of 61.4% for a class of about twenty students (Spring 2007) in thermodynamics; the corresponding improvement in the average C.I. score for about ten students (Summer 2007) was from 43.7% to about 60%.
Simulation of a Biodiesel Continuous Production Process Using HYSYS®
Authors: Garci´a Jaime , Giraldo Jorge , Bula Antonio , A´vila Adria´n
Published: May 2009

Elements of Chemical Process Engineering were used in this research to design and simulate two continuous transesterification processes for the production of biodiesel from palm oil, using the chemical simulator, HYSYS®. This design specified the operating conditions of all the equipment required for the continuous production of biodiesel using ethanol and methanol as alcohols. The palm oil was modeled as a mixture of the triglycerides that compose it in greater proportion, estimating the chemical properties of the substances that take part in the transesterification reaction, with group contributions and group interactions theories. Finally, the quality specifications for biodiesel obtained in both simulations were analyzed to verify the fulfillment of the properties required by ASTM (American Society for Testing and Materials) and EN (European Norms) standards.
Emissions Testing From the Use of Various Biodiesel Blends in Representative Canadian Army Equipment
Authors: Allan W. D. , Gardiner D. , Bennett L. , LaViolette M. , Pucher G. , Turingia M.
Published: May 2009

A comprehensive series of emissions measurements were taken from two pieces of equipment used by the Canadian Forces. A field kitchen burner unit and the engine from the Light Armoured Vehicle III (LAVIII) were operated using two base fuels: low and ultra low sulphur diesel fuel blended with three different biofuels. Methylesters from canola, tallow and yellow grease were mixed in a range of volumetric proportions from 0 to 20%. Additionally, both very low sulphur diesel and aviation turbine fuel (JP-8) were tested against neat low sulphur diesel fuel. The complete chemical analysis conducted on all test fuels will not be presented here. A full range of gaseous emission measurements were obtained including oxides of nitrogen, unburnt hydrocarbons, carbon monoxide and dioxide and limited sulphur dioxide measurements. Two means of monitoring particulate matter were used with one proving to be more effective than the other. Novel techniques were used to obtain the burner unit emissions results and the AVL 8-mode test sequence was applied to the Caterpillar engine from the LAVIII. Although emission trends were detected, levels were often on the margins of perceptibility of the gas analysis system, and atmospheric conditions were challenging. Nevertheless, a methodology was developed and refined. Some correlations were made between the chemical analysis and emissions results. The testing will allow the Canadian Army to estimate its emissions footprint.
Extended Arrhenius Kinetic Model for the Transesterification Reaction of Biodiesel From Palm Oil and Ethanol
Authors: Giraldo Jorge , Garci´a Jaime , Bula Antonio , Sanjuan Marco , A´vila Adria´n
Published: May 2009

Modeling and understanding reaction kinetics is essential for processes and equipment design. This paper presents a kinetic analysis of the transesterification reaction of palm oil extracted in the Colombian north coast with ethanol to produce biodiesel. The analysis is based in actual lab scale production and it considers a set of three reactions in a batch reactor with dynamic behavior. It was found that the kinetics does not adjust to the common Arrhenius equation model, therefore an extended Arrhenius equation model was proposed. This extended model captures temperature effects better than the standard Arrhenius form. New reaction constants were found using computer-based regression analysis, and the model was later used to simulate a continuous biodiesel production plant.
Effect of Size and Spatial Distribution of Titania Pigments in Injection Molded Parts on Surface Reflectance
Authors: Dantal B. R. , Saigal A. , Zimmerman M. A.
Published: May 2009

Titania pigments are used in molding compounds as a means to improve opacity by increasing the scattering efficiency of the medium and to develop new applications such as liquid crystal displays (LCD) and light emitting diodes (LED). The characteristics of the injection molded products are a function of molding parameters such as gate location and shear rate. In this study, quantitative measures of the particle distribution of titania pigments in polymer composites have been experimentally determined, including area fraction, average diameter, and diameter volume. A 2 × 3 × 3 ANOVA test has been conducted to assess the statistical significance of these parameters. This study deals with the size and spatial distribution of the particles. The important parameters calculated based on the Feret’s diameter are diameter-volume (dv), diameter-number (dn), and area fraction (AF). The term diameter-volume (dv) has been used to give greater significance to the large particles and thus ‘large’ indicates more and/or larger particles. The parameters have been calculated by using Image-J image processing software. MINITAB has been used to assess the statistical significance of these parameters. The results show that titania particles are not uniformly distributed within the final molded parts and they vary along the molding (longitudinal) and transverse directions of plastic flow. The difference of pigment area fraction and diameter volume at different locations within a final molded part has a significant effect on the percentage reflectance of the surface.
Stability Issues for Gas-Liquid Flows in Bubble Columns
Authors: Law Deify , Battaglia Francine , Heindel Theodore J.
Published: May 2009

In the present work, gas-liquid flow dynamics in a bubble column are simulated with CFDLib using an Eulerian-Eulerian ensemble-averaging method in a two dimensional Cartesian system. The time-averaged gas holdup simulations are compared to experimental measurements of a cylindrical bubble column performed by Rampure et al. [1]. Numerical predictions are presented for the time-averaged gas holdup at various axial heights as a function of radial position. The effects of grid resolution, bubble pressure model, and drag coefficient models on the numerical predictions are examined. The bubble pressure model is reported to account for bubble stability, thus providing physical solutions. The objectives are to obtain grid-independent numerical solutions to resolve unphysical results observed in FLUENT with increasing grid resolutions [2], and to validate computational fluid dynamics simulations with experimental data to demonstrate the use of numerical simulations as a viable design tool for gas-liquid bubble column flows.
Determining Material Properties of Nonlinear Materials From Transient Response
Authors: Reed Shad A. , Palazotto Anthony N. , Baker William
Published: May 2009

Several researchers have shown that the material properties of hard coatings used in free layer damping treatments are dependent on the strain amplitude in the coating. This nonlinear phenomenon complicates the material characterization process and makes it difficult to find independent sets of data that are in complete agreement. During a recent in depth study of these materials, it became apparent that there were several other time and load history dependent nonlinearities present in these fascinating materials. These nonlinearities were observable because a free response based testing methodology was employed. Results indicate that the stiffness and damping of these materials change during the first several million loading cycles before finally stabilizing. Additionally, results suggest that the material properties are dependent on the initial condition of the free response, indicating a short term loading history dependency.
Comparison of Particle Dynamics Analyzer (PDA) and SetScan Optical Patternator Results
Authors: Muliadi Ariel R. , Sojka Paul E. , Sivathanu Yudaya R. , Lim Jongmook
Published: May 2009

The primary goal of this study was to determine when patternation information derived from Particle Dynamics Analyzer (Dantec Dynamics dual-PDA) measurements of volume flux, velocity and mean drop size agreed with corresponding values measured using an optical patternator (En’Urga, Inc SetScan OP-600). To achieve this, data from each instrument was transformed into spatially resolved absorptances (equivalent to drop surface area per unit volume) and compared. The secondary goal of this study was to explain the cause of any discrepancies in comparison of the two absorptance sets when they occurred. Key conclusions drawn from this study are: absorptance agreement to within 20% can be achieved in many cases; however, the difference between the PDA-calculated and optical patternator-measured absorptances becomes larger as the drop arrival rate increases, as the drop size decreases, and when a significant drop size-velocity correlation is present. These discrepancies are attributed to an underestimation of the volume flux (which becomes more important with increasing droplet arrival rate), an over-reporting of the mean drop diameter (which is the result of the restrictive data acquisition scheme applied when ensuring mass closure), the limited PDA dynamic range (which can preclude simultaneously accounting for both the largest and smallest drops in the spray), and by the optical patternator’s number-density based measurement scheme (which will not yield the same results as the flux-based PDA when a drop size-velocity correlation is present).
Experimental Evaluation of the Convective Heat Transfer Coefficients in a Nanofluid-Cooled Milli Channels Heat Sink
Authors: Valencia Guillermo E. , Ramos Miguel A. , Bula Antonio J.
Published: May 2009

The convective heat transfer process and flow characteristics of aluminum oxide (Al2O3)/water nanofluid flowing through milli channels with a hydraulic diameters of 2 mm, with a constant heat flux boundary condition, was investigated. Using experimental equipment, the effect of some factors like volume fractions, Reynolds number and Peclet number are evaluated. Furthermore, an experimental model for Nusselt number is presented in order to show the enhancement of the convective heat transfer compared with a single-phase model in milli channel. Suggestions and direction for future developments for the use of nanofluids in milli channels are also presented.
Differentially Flat Designs of Mobile Vehicles With Under-Actuated Manipulator Arms
Authors: Ryu Ji-Chul , Sangwan Vivek , Agrawal Sunil K.
Published: May 2009

Differential flatness has been investigated in the context of mobile vehicles for planning and control of their motions. In these models, the wheels are considered to be non-slipping, i.e., the system dynamics is subject to non-holonomic constraints. If a manipulator arm is mounted on such a mobile vehicle, the dynamics becomes highly nonlinear due to the nonlinear coupling between the motions of the mobile vehicle and the manipulator arm. A challenging question is how to perform point-to-point motions of such a system in the state space of the mobile manipulator. If some of the actuators are absent in the mechanical arm, the mobile manipulator becomes under-actuated and consequently even harder to plan and control. This paper presents a methodology for design of mobile vehicles, mounted with under-actuated manipulators operating in a horizontal plane, such that the combined system is differentially flat. In this paper, we show that by appropriate inertia distribution of the links and addition of torsion springs at the joints, a range of under-actuated designs are possible where the underactuated mobile manipulator system is differentially flat. The differential flatness property allows to efficiently solve the problem of trajectory planning and feedback controller design for point to point motions of the system. The proposed method is illustrated by the example of a mobile vehicle with under-actuated three-link manipulator.
Closed-Loop Optimal Control Strategy for Cancer Chemotherapy
Authors: Ramkumar Barathram , Naidu D. Subbaram
Published: May 2009

Cancer chemotherapy is the treatment of cancer using drugs that kill the cancer cells, when the drugs are administered either orally or through veins. The drugs are delivered according to a schedule so that a particular dosage of drug level is maintained in the body. The disadvantage of these drugs is that they not only kill the cancer cells but also kill the normal healthy cells. The role of optimal control in chemotherapy is to maintain an optimum amount of drug level in the body so that only cancer cells are killed and hence the effect of drug on the healthy cells is minimized. Three different mathematical models for cancer growth are considered: log-kill hypothesis, Norton-simon model, and Emax model. Two different cost functions are considered for constrained and unconstrained optimal control, respectively. An open loop optimal control strategy has been reported in the literature. In this paper, a closed-loop optimal control strategy is addressed using all the three models and for both the cases of constrained and unconstrained drug delivery. For the unconstrained case the original nonlinear model has been linearized and the closed loop design is obtained by using matrix Riccati solutions. On the other hand, for the constrained case the original nonlinear model has been used to obtain closed loop optimal control using bang-bang strategy. Final simulation results show the advantages of closed loop implementation in terms of simpler and elegant controller design and incorporating the effect of current state variations.
Analysis of Actuator Requirements for Micro UAV Telescoping Wings
Authors: Sanderson Terry
Published: May 2009

For many micro UAV uses, maximum air vehicle endurance and/or range is a primary requirement. Maximizing endurance and range requires long span, high aspect ratio wings, but for man-portable and tube launched UAV applications there is rarely enough room to stow adequate wing span. In this work, a simple slip fit telescoping shell wing concept, appropriate for extending the wing span of micro UAVs, was analyzed to determine the actuator force-displacement and power consumption relationships, including consideration of the variable wing load distribution that occurs on a telescoping span wing. The required time scale for actuation is also discussed. These results are a necessary part of selecting an appropriate actuator, whether it is an advanced “smart material” actuator or something as simple as a one-way, one-time coil spring. It was found that a wing span increase of about 85% is probably the optimum amount of extension that can be achieved using this telescoping shell wing concept.
Thermal Design of Highly-Efficient Thermoelectric Materials With Atomic-Scale Three-Dimensional Phononic Crystals
Authors: Gillet Jean-Numa , Chalopin Yann , Volz Sebastian
Published: May 2009

Owing to their thermal insulating properties, superlattices have been extensively studied. A breakthrough in the performance of thermoelectric devices was achieved by using superlattice materials. The problem of those nanostructured materials is that they mainly affect heat transfer in only one direction. In this paper, the concept of canceling heat conduction in the three spatial directions by using atomic-scale three-dimensional (3D) phononic crystals is explored. A period of our atomic-scale 3D phononic crystal is made up of a large number of diamond-like cells of silicon atoms, which form a square supercell. At the center of each supercell, we substitute a smaller number of Si diamond-like cells by other diamond-like cells, which are composed of germanium atoms. This elementary heterostructure is periodically repeated to form a Si/Ge 3D nanostructure. To obtain different atomic configurations of the phononic crystal, the number of Ge diamond-like cells at the center of each supercell can be varied by substitution of Si diamond-like cells. The dispersion curves of those atomic configurations can be computed by lattice dynamics. With a general equation, the thermal conductivity of our atomic-scale 3D phononic crystal can be derived from the dispersion curves. The thermal conductivity can be reduced by at least one order of magnitude in an atomic-scale 3D phononic crystal compared to a bulk material. This reduction is due to the decrease of the phonon group velocities without taking into account that of the phonon average mean free path.
Active Membrane Using Electrostructure Graft Elastomer for Deployable and Lightweight Mirrors
Authors: Yang E. H. , Hishinuma Y. , Su J. , Xu T. B. , Morgan R. , Chang Z.
Published: May 2009

An important requirement enabling future space missions is the availability of very large, deployed, re-configurable apertures for high-resolution imaging. Membrane-based architectures have the potential for very low aerial densities, which will enable large aperture space telescopes. Two major requirements for considering large apertures are: 1) a high degree of surface control coupled with a low-mass deployable capability and 2) an optical quality membrane mirror technology. Current state-of-the-art deployable aperture technologies have significant limitations in their ability to correct the surface figure following deployment. In this paper, a controlled deformation of silicon membrane mirrors using electroactive polymer has been demonstrated to overcome these limitations. We have designed, modeled, and fabricated Electrostrictive Graft Elastomer (G-elastomer)-based bi-layer membranes. The bi-layer mirror membranes maintain a good working condition after thermal cyclic tests, performed at temperatures between −50 °C and 150 °C. G-elastomer provides means to drive and control the deflection and curvature of reflective membranes. Several G-elastomer-based bi-layer structures have been optically characterized. This concept can be scaled to a deployable ultra-large mirror with a self-reconfiguration capability.
Manipulation of Biological Analytes in Microfluidic Devices Using Various Electrode Geometries and Electrokinetic Techniques
Authors: Gangadharan Kishore , James Conrad , Song Hongjun , Bennett Dawn J.
Published: May 2009

Micro-electro-mechanical systems are now used in a wide variety of applications ranging from biodetection to the healthcare industry. Electrokinetic techniques such as dielectrophoresis and electroosmosis are frequently used for the manipulation of cells, molecules, and spores. In this paper, we show that dielectrophoresis can be used to manipulate allergens and bacteria in a wide variety of microfluidic devices. We have found that allergens such as Penicillium brevicompactum demonstrate positive dielectrophoresis and moves toward high field gradient regions while the non-biological latex beads move towards the low electric field gradient regions. Microfluidic devices equipped with dielectrophoretic gates arranged perpendicular to the flow were designed and fabricated at Sandia National Laboratories. Experiments were conducted on flowing suspensions over a broad range of flow and electric field parameters to investigate how these characteristics affect the concentration and separation of particles. Trapping using the dielectrophoretic gating device as well as the design, experimental results, and analysis of devices for particle filtration are presented. Some of the devices were fabricated using Sandia’s (SwIFT™) process while other devices were fabricated using polymers and traditional photolithography methods. We present both methods used in the fabrication of devices. The long-term goal is to develop complete hand held Lab-on-a-Chip microsystems for biodetection. The ability to manipulate and concentrate minute particles can allow for advances in the medical field as well as the future detection of biological warfare agents such as anthrax. In order to analyze biological analytes, it is first necessary to develop a method for positioning and detecting the analyte of interest. Concentrating biological particles such as the allergen Penicillium brevicompactum (PBC), Bacillus globigii (BG) spores, an anthrax stimulant, and Staphylococcus Aureus (Staph Cells), a type of food bacteria, is done using the principle of dielectrophoresis. Microfluidic devices which we use to test the suspensions were fabricated using the SwIFT™ process developed by Sandia National Laboratories. In addition, electrode designs were also fabricated using a process that we have developed in-house at the University of Maryland Baltimore County (UMBC) using polydimethysiloxane, PDMS, to make the channels and the deposition of gold, Au, as the material for the electrodes fabricated with the low pressure chemical vapor deposition method (LPCVD).
Effects on Initial Development of Rayleigh-Taylor Instabilities Due to a Change in Initial Conditions
Authors: Peart Michael , Gore Robert , Andrews Malcolm J.
Published: May 2009

The effect on the initial development of Rayleigh-Taylor mixing due to a change in initial conditions has been experimentally studied. A water channel facility at Texas A&M University has been used to provide a statistically steady experiment for the investigation of buoyancy-driven turbulent mixing. Parallel streams of hot and cold water are separated initially by a splitter plate. The streams are oriented in such a way to place cold water above the hot water. Upon the termination of the splitter plate, the two streams are allowed to mix and a buoyancy-driven mixing layer develops. The growth rate of the mixing layer has been experimentally measured using image analysis techniques. Our studies have shown that introducing broadband initial disturbances can have a significant effect on the growth rate of Raleigh-Taylor instabilities, however, the mechanism that controls energy transfer at early time is not clear and requires further investigation.
New Command Shaping Methods for Reduced Vibration of a Suspended Payload With Constrained Trolley Motion
Authors: Enes Aaron R. , Hsu Timothy Y. , Sodemann Angela A.
Published: May 2009

In manufacturing environments, a common task is to quickly move a suspended payload point-to-point along a fixed overhead conveyor track without inducing significant payload vibration. Recent research in command shaping has shown remarkably effective ways to reduce the swing of a suspended payload providing the motion of the trolley is not constrained. However, the development of a command shaper where the trajectory of the trolley is constrained to follow a fixed curvilinear path has not been explored. This paper will present the development of a simple feedforward command shaper for fast, low vibration, point-to-point movement of a payload suspended from a trolley constrained to follow a fixed generalized path. The command shaping method involves modifying the command signal by convolving it with a series of impulses. Prior work has suggested command shaping to be very effective for fast, low-vibration movement of flexible systems. In this paper, command shaping methods are applied to an overhead conveyor system constrained to move along a fixed curvilinear path. Two new command shapers are presented for canceling payload vibration induced by motion of the trolley along the path. The designed Tangential Vibration (TV) shaper reduces payload vibrations induced by tangential accelerations of the trolley along the path, while the Centripetal-Tangential Vibration (CTV) shaper reduces vibrations induced by both tangential and centripetal accelerations. A key result of this study is that a command shaper having at least three impulses is required to yield zero residual vibration for motion along a curvilinear path. A simple pendulum payload attached to an actual small-scale overhead trolley following a constrained path is used to evaluate the performance of the designed command shapers. It is shown that the designed shapers significantly reduce payload swing compared to unshaped performance. An experimental sensitivity analysis shows the designed shapers are robust to system modeling errors and variations in path parameters.
A Successful Model of Undergraduate Research at Milwaukee School of Engineering
Authors: Kumpaty S.
Published: May 2009

Undergraduate research performed at Milwaukee School of Engineering (MSOE) has contributed significantly to the development of independent, well-rounded engineers by providing opportunities for students’ professional growth, knowledge, experience, creativity and confidence. Through a decade-long and continuing, summer Research Experience for Undergraduates (REU) program sponsored by the National Science Foundation, we have demonstrated extraordinary success at the MSOE interdisciplinary Rapid Prototyping Center and the closely associated Center for BioMolecular Modeling—hubs of activity with faculty, staff, students and industry working together in a variety of programs. Specifically, we have provided integrated research opportunities for technically diverse groups of undergraduate students to experience the growing technological trends and opportunities in rapid prototyping (RP) leading to newly created, complex and miniature structures and models. We have continued the principle of diversity in successful recruiting of minorities, women and students with disabilities, enabling them to become professional graduates with extraordinary capabilities. We developed interdisciplinary approaches, enabled by research and development in rapid prototyping, in the fields of biomedical, biomolecular, manufacturing, mechanical, electrical, architectural and aerospace engineering. We continue to publish the findings from the research projects in national conferences and journals. Our success at fostering undergraduate research is showcased through the nature of student activities and specific projects, the research/mentoring environment and facilities, student recruitment history including diversity, evaluation results, samples of program impact and highlights of summer REU program at MSOE.
Heat Transfer for Annular Flow in Microchannel Bends: A Free Energy Minimization Model for Square Channels
Authors: Beaini Sara , Carey Van P.
Published: May 2009

For annular liquid-vapor two-phase flow in straight microchannels, effects of gravity are generally small compared to viscous and/or inertia forces. In serpentine evaporator or condenser passages with semicircular return bends, the bend radius may be so small that large centrifugal body forces are generated as the fluid flows through the bend region of the passage. This paper summarizes a model analysis based on the premise that flow morphology in the bend is dictated by radial acceleration forces and the thermodynamic Second Law requirement that the established two-phase flow morphology minimizes the free energy at the local temperature and pressure. An analytical model is derived relating the dependence of the free energy on vapor core geometry, and the geometry that minimizes free energy is determined numerically. This provides a prediction of the mean thickness of the liquid surrounding the vapor core, and the mean heat transfer coefficient for annular flow vaporization or condensation, as a function of flow parameters and physical properties. When this relation is cast in dimensionless form, the effect of centrifugal acceleration is quantified in terms of a Weber number (We) that represents the ratio of centrifugal body force to surface tension force. The analysis indicates that centrifugal acceleration acts to displace the vapor towards the inside of the curved passage and distort the liquid-vapor interface. Displacement occurs at any level of acceleration. Significant distortion is found to occur only for We > 1. The effects of these morphology changes on heat transfer are analyzed and the implications of these predictions for designing microchannel evaporators and condensers are explored.
Numerical Modeling of a Double Fired Process Heater With Different Internal Wall Configurations
Authors: Yeates Devin R. , Jian Christopher Q. , Lorra Michael
Published: May 2009

A double fired process heater with combination oil/gas burners has been modeled with computational fluid dynamics (CFD). The process heater was simulated with two configurations: 1) with internal walls, and 2) without internal walls. The purpose of this study is to understand the effect of the internal walls on flame shape and process tube heat flux. As a result of removing the internal wall, furnace currents are allowed to have a large influence on the flame patterns and the flames lean toward the tubes. It is also shown that higher localized heat fluxes occur on the process tubes with the walls removed. This study demonstrates that the primary function of the internal walls is to isolate cells within the furnace which create satisfactory process tube heat fluxes.
Effects of Tandem Pulse on Stone Comminution in an Electromagnetic Shock Wave Lithotripter
Authors: Smith Nathan , Simmons W. Neal , Sankin Georgy N. , Zhong Pei
Published: May 2009

Despite recent innovations in lithotripter design and technology, the first generation Dornier HM-3 electrohydraulic lithotripter remains the most effective clinical, non-invasive modality for comminuting stones. Understanding the fundamental differences between the HM-3 and more clinically practicable lithotripters is critical to achieving meaningful improvements in future models. This study aims to further clarify the role of the second, weaker pulse of the HM-3 in stone comminution by introducing a similar pulse in the pressure profile of an electromagnetic lithotripter. Additionally, this study investigates the potential for this tandem shock technique to improve comminution in electromagnetic lithotripters through optimization of the interpulse delay time.
Composite Scarf Repair Patch Optimization Under Uniaxial Loading Conditions
Authors: Breitzman T. D. , Cook B. M. , Schoeppner G. A. , Iarve E. V.
Published: May 2009

Simplex optimization algorithm was applied to predict the fiber orientations of the scarf repair patch for a given quasi-isotropic panel to maximize strength retention of the repair. The optimal stacking sequence of the repair patch avoids 0 degree plies in the direction of the load. Such a stacking sequence prolongs the life of the adhesive and results in a predicted 13% strength increase as compared to the traditional ply-by-ply replacement. The second optimization problem solved was one of finding the least favorable stacking sequence of the repair patch. Such stacking sequence inserts stiff plies into the patch and leads to the failure of the repair patch as early as 20% below the reference failure load of the repair patch with traditional ply-by-ply replacement. The strength prediction model consisted of nonlinear constitutive modeling of adhesive behavior and fiber failure prediction loads in the adherents based on critical failure volume (CFV) (see [8]) strength prediction method. Benchmark analysis was performed on the virgin, scarfed, and repaired (ply-by-ply replacement) panels and was in good agreement with experimental data.
Process Optimization Studies on Ni-YSZ Anode Material for Solid Oxide Fuel Cell Applications
Authors: Rajaram Gukan , Desai Salil , Xu Zhigang , Pai Devdas M. , Sankar Jag
Published: May 2009

The characteristics of the Ni/YSZ anode material for the solid oxide fuel cells (SOFCs) were investigated in order to study the relation between the porosity and the conductivity of the cell. The nano-sized Yittria Stabilized Zirconia (YSZ) (∼ 60 nm), Nickel Oxide (NiO) (∼ 40 nm) and graphite (∼ 40 nm) particles were used as the raw materials. The graphite particles act as a pore former. The experiments were planned based on a response surface design (central composite design matrix). The graphite content and the sintering temperatures were varied based on the design chart, while the other variables like NiO/YSZ ratio, ball milling time, powder compaction pressure and reduction temperature values were fixed. Porosity and conductivity measurements were performed on the sintered and reduced anode material. The results indicated that the porosity values got decreased by increasing sintering temperature values, while the conductivity values were on the reverse scale. The conductivity values increase with increasing temperature. The scanning electron microscope (SEM) images showed that the sintering temperature had a visible impact on the microstructure. At elevated temperature, the microstructure showed visible particle growth and it formed a better Ni-network along the structure, compared to samples sintered at lower temperature. It is believed that the enhanced Ni-network at elevated temperature helps to increase the electrical conductivity of the Ni-YSZ anode cermet.
Structural Analyses and Experimental Activities Supporting the Design of a Lightweight Rigid-Wall Mobile Shelter
Authors: Cavallaro Paul V. , Jee Melvin
Published: May 2009

Lightweight rigid-wall shelters used in mobile military operations are often constructed of sandwich panels comprised of thin face sheets and thick, yet ultra light core materials to minimize weight while maximizing structural integrity. The key structural advantage of sandwich panel construction (SPC) versus homogeneous panel construction (HPC) is the potential for up to an order of magnitude weight reduction while matching equivalent bending stiffnesses. Additional advantages include increases in damping, acoustic and thermal insulation, and possibly ballistic protection performance for a given areal weight density. However, these advantages come at a cost, which often impact the design and manufacturing complexities of critical joints used to connect the sandwich panels in a box-like assembly. Furthermore, stiffnesses of these joints are often difficult to characterize and their finite values significantly influence panel deflections and rotations. While mobile rigid wall shelters must be certified for several transport loading environments including rail impact (vehicle mounted and dismounted), drop shock, mobility and external air transport (EAT), the present effort, addresses survivability against conventional air blast effects. This study employed combined experimental and analytical approaches at the material and sub-structural levels to (1) generate accurate shelter models, (2) validate the material- and sub-structural models and (3) maximize the shelter’s global performance against a conventional air blast event early in the design stage to avoid costly physical tests. The material level tests focused on the mechanics of the assembled constituents that formed the sandwich panel and the benchmarking of an appropriate finite element to predict the displacement, stress and strain responses. The sub-structural level tests focused on loading a structurally representative shelter section to determine the joint behaviors and stiffnesses for model benchmarking purposes. Finally, a complete rigid-wall mobile military shelter model was constructed and its modal behavior was characterized followed by its complete dynamic response to an air blast event.
Applying Info-Gap Theory to Remanufacturing Process Selection Affected by Severe Uncertainty
Authors: Duncan Scott J. , Paredis Christiaan J. J. , Bras Bert
Published: May 2009

In this article, Information-Gap Decision Theory (IGDT), an approach to robust decision making under severe uncertainty, is applied to decisions about a remanufacturing process. IGDT is useful when only a nominal estimate is available for an uncertain quantity; the amount that estimate differs from the quantity’s actual value is not known. The decision strategy in IGDT involves maximizing robustness to uncertainty of unknown size, while still guaranteeing no worse than some “good enough” critical level of performance, rather than optimal performance. The design scenario presented involves selecting the types of technologies and number of stations to be used in a remanufacturing process. The profitability of the process is affected by severe uncertainty in the demand for remanufactured parts. Because nothing is know about demand except an estimate based on a different product from a previous year, info-gap theory will be used to determine an appropriate tradeoff between performance and robustness to severe uncertainty. Which design is most preferred is seen to switch depending on choice of critical performance level. Implications of findings, as well as future research directions, are discussed.
An Ablation Parameter Study and Micromachining of NiTi Based Shape Memory Alloy Using Femtosecond Laser
Authors: Uppal Nitin , Shiakolas Panos S.
Published: May 2009

The use of femtosecond lasers for the micromachining of engineering materials with micro and submicron size features is slowly but steadily increasing. This increase though presents challenges in understanding the interaction mechanism of femtosecond laser pulses with a material and defining process parameters for quality machining. This manuscript will present the setup for a 3DOF femtosecond laser microfabrication (FLM) system and its use in studying the ablation (single and multi shot) characteristics and incubation coefficient of nickel-titanium (NiTi) shape memory alloy. Understanding of these characteristics could allow for the identification of new applications of smart materials in the macro, micro, nano and MEMS domains.
Elastic Contact of Nominally Flat Rough Surfaces Containing Micron Scale Roughness
Authors: Sepehri A. , Farhang K.
Published: May 2009

A hybrid interactive/optimization technique is used to derive in approximate closed form equations relating contact load to mean plane separation. Equations governing Hertz contact for the interaction of surface asperities are considered in which asperity shoulder-to-shoulder contact results in normal and tangential components of force. The normal component of asperity force is summed statistically to find total normal force between the two surfaces. The tangential component of asperity force, summed statistically, yields zero total force due to the symmetry of the distributed tangential force components. The tangential force over a half-plane corresponding to a select direction is found accounting for the directionality of the tangential component of asperity forces. Two sets of approximate equations are found for each of the normal and half-plane tangential force components. The simplest forms of the approximate equations achieve accuracy to within five (5) percent error, while other forms yield approximation error within 0.2 percent.