bluuebunny/crossref_metadata_2025 huggingface dataset:
A Systematic Approach for Optimal Mounting System Design of Truck Body
Authors: Jiang Dongying , Cui Yushun , Ma Zheng-Dong , Hadi Rod
Published: April 2008

Body mount system is utilized for isolating dynamic load and vibration into the cab from the rest of vehicle system. The behavior of the mount system not only depends on the performance of individual mounts but also on the complete system configuration. A systematic approach is proposed for optimal design of the truck body mount system. Design variables include the mount locations and mechanical properties of each individual mount. First, an advanced component mode-based substructuring method is utilized for developing reduced-order models of the cab body and the other related subsystems, such as the chassis frame, from the original detailed finite element models. An optimization procedure is then developed, which can be used to determine the geometric distribution of the mounts and their mechanical characteristics (e.g., dynamic stiffness and damping) for minimizing vibration amplitudes at the given locations in the body structure over a frequency range of interest. To determine the optimal mount distribution, a path variable is introduced at the interface of cab and frame, which allows each individual mount moving along the chassis frame in the permitted range. The optimal mount location design problem is thus transformed to an equivalent problem that determines the optimal path variables of each mount. MATLAB codes are developed for the mount system design problem. An example mount system design is given to illustrate the effectiveness and efficiency of the proposed approach, in which the mount stiffness and the mount locations are optimized simultaneously. The developed optimization tool can be extended for optimizing other general mounting systems, such as an engine mount system.
Uncertainity Analysis for the Fiducial Calibration System
Authors: Woody Bethany A. , Smith K. Scott , Hocken Robert J. , Miller Jimmie A.
Published: April 2008

Previous work has established the Fiducial Calibration System (FCS), a technique, which, for the first time provides a method that allows for the accuracy of a CMM to be transferred to the shop floor. This paper addresses the range of applicability of the FCS, and provides a method to answer two fundamental questions. First, given a set of machines and fiducials, how much improvement in precision of the finished part can be expected? And second, given a desired precision of the finished part, what machines and fiducials are required? The achievable improvement in precision using the FCS depends on a number of factors including, but not limited to: the type of fiducial, the probing system on the machine and CMM, the time required to make a measurement, and the frequency of measurement. In this paper, the sensitivity of the method to such items is evaluated through an uncertainty analysis, and examples are given indicating how this analysis can be used in a variety of cases.
Finite Element Analysis of Kinematics and Dynamics of Linkages
Authors: Zhao Jiaxin
Published: April 2008

The kinematics and dynamics of two dimensional linkages is analyzed using an uniformed finite element approach in this paper. Each link in the linkage is a naturally discretized finite element and the joints are the nodes connecting elements. The analysis consists of two parts, namely the kinematics part and the dynamics part. In the first kinematics part, positions, linear velocities and linear accelerations of the joints are used as the solution variables in the finite element formulation. In order to have close-form solutions, the linkage must have only one degree of freedom. These joint variables are then solved for each input link configuration of angular position, velocity and acceleration. The angular positions, velocities and accelerations of the other links are then calculated from the joint variables. The position, linear velocity and acceleration of any point on the linkage, like the center of gravity for a particular link, can also be determined if desired. The second dynamics part uses joint forces as the solution variables in the finite element formulation. In each element, a third node is also defined to allow an external force or torque to be applied. Based on the solutions in the first kinematics part, the joint forces are solved for each input configuration. The forces inside each link can then be determined from the joint forces. A MATLAB program is developed for this finite element analysis on general four bar linkages and is posted on the author’s webpage.
Dynamic Model of Planar Solid Oxide Fuel Cells for Both Steady State and Transient Performance Analysis
Authors: Xi Handa , Sun Jing
Published: April 2008

With its high efficiency and low emissions, Solid Oxide Fuel Cell (SOFC) is a promising alternative solution for many applications including both stationary power plants and mobile Auxiliary Power Unit (APU) systems. In this paper, a dynamic model is developed for planar co-flow SOFCs for both transient and steady-state performance analysis. Finite volume method with user-defined grid is adopted to deal with the spatial distributions of current densities, pressures, temperatures and gas compositions in the SOFC. Simulations of both transient and steady state behaviors are performed to analyze the system performance. Fuel utilization, air excess ratio, air inlet temperature and current density are identified as critical operating parameters for steady-state performance in terms of cell efficiency, maximum temperature and temperature gradient in the Positive electrode-Electrolyte-Negative electrode (PEN) structure. Dynamic responses to step changes of fuel and air flow rates (two important control variables) and responses to the step change in load (the main disturbance) are analyzed to shed lights on feedback control design.
Framework for Modeling the Components of a Fuel Processing System for Fuel Cell Applications
Authors: Sampara Chaitanya , Depcik Christopher , Assanis Dennis
Published: April 2008

The present work describes models for predicting concentration profiles of various species in each of the reactors present in a fuel processing system including a steam reformer, water gas-shift reactor and a preferential oxidation reactor. These reactor models incorporate phenomenological reaction schemes in power law format in order to predict the conversion of the species as a function of concentration and temperature. A surface film approach is used rather than the more traditional two-dimensional boundary layer in order to model the gas on the surface of the catalyst. The modeling framework is built within the Matlab Simulink environment to take advantage of available numerical schemes and optimization algorithms. Only steady state operation is considered for the reactors with validation occurring against experimental data obtained from the literature. In addition, temperature gradients within the reactors are imposed in order to eliminate the need to model the energy equation of motion. Parametric studies are performed on each of the individual reactors by varying the length, catalyst loading, catalyst dispersion and the effect of temperature drop across the reactor.
Automated Risk Scenario Generation Using System Functional and Structural Knowledge
Authors: Nejad Hamed , Mosleh Ali
Published: April 2008

Simulation may be the most practical way to assess the risk of systems with complex behaviors such as those that include hardware, software and human elements. However, since under normal design conditions human-designed systems generally perform in familiar and expected ways, a typical simulation will frequently lead to known and anticipated results. As such, the simulation program wastes a lot of time on familiar results without generating new knowledge about the system’s vulnerabilities. In order to increase our knowledge of risk, it would be preferable to push the system toward its limits to test the system’s ability to handle more difficult situations. Such an approach can help system designers to better understand risky situations and close the vulnerability gaps in their design. The primary objective of this study is to develop a risk simulation Planner (SimpraPlan) which generates scenarios that can explore the system’s vulnerabilities and offer a superior assessment of the risks involved. The Planner uses high level engineering knowledge (including the functional requirements and physical structure of the system) to generate scenarios that can exploit the system’s vulnerabilities. In this paper, the scenario generation process is explained in detail and scenarios generated by the SimpraPlan are compared with those generated by classical approaches to risk assessment.
Engine Control Using Estimated Parameters From a Real Time Model of an Engine With Variable Valve Actuation
Authors: Lahti John L. , Moskwa John J.
Published: April 2008

A real time model of an engine was developed and integrated with engine control software to provide better engine control with less calibration effort. The model uses one-dimensional compressible gas wave equations for the intake and exhaust system along with a thermodynamic model of the cylinder to provide real time estimation of the cylinder air charge, exhaust gas residual mass fraction, cylinder pressure, cylinder temperature, and various other states along the intake and exhaust system. Information from the model is used to control the fuel injection, spark advance, valve timing, and throttle position on the actual engine. The system does not use any volumetric efficiency tables. Since the real time model responds like the actual engine there is no need for transient fuel or transient spark advance correction factors. The estimated cylinder pressure is used to calculate the instantaneous indicated engine torque and engine efficiency. Using the model it is possible to optimize efficiency, control the torque output, and regulate the exhaust gas residual mass fraction. The system offers many control advantages and is easy to calibrate.
Effects of Carbon Nanotube Structure on Protein Adsorption
Authors: Kim Sungwon S. , Huang Tom T. , Fisher Timothy S. , Ladisch Michael R.
Published: April 2008

Outstanding transport characteristics and high surface-to-volume ratios are several advantages that carbon nanotubes possess that make them attractive candidates for protein immobilization matrices in biosensor applications. A further advantage of using carbon nanotubes is that their structure (e.g., diameter, length, density) can potentially be controlled during synthesis. In the present study, the effects of carbon nanotube structure on enzyme immobilization onto carbon nanotube arrays are investigated. Bovine serum albumin (BSA) serves as both a blocking agent for prevention of nonspecific adsorption and as a support for anchoring bioreceptors. BSA, a globular protein having a 4 to 6 nm characteristic dimension, is stably adsorbed through mechanisms that involve hydrophobic interactions between surfaces presented by the carbon nanotubes and the spacing between the nanotubes with the protein. Protein adsorption is confirmed by fluorescence microscopy of surfaces that have been exposed to fluourescein isothiocyanate (FITC) labeled BSA. The adsorption of biotinylated BSA can be used, through a sandwich immobilization scheme, to provide an anchor for streptavidin, which in turn has at least one other adsorption site that is specific for other biotinylated proteins such as glucose oxidase that would form a biorecognition or catalytic element in a functional biosensor. Correlation between carbon nanotube structure and protein adsorption at the nano-bio interface could eventually lead to growth conditions that yield carbon nanotubes for biosensor applications with optimal protein adsorption characteristics.
Surface Tension Measurement at High Temperatures by Using Numerical and Theoretical Drop Profiles
Authors: Moradian A. , Mostaghimi J.
Published: April 2008

Interfacial tension measurement is studied for the case of high melting point materials. Atmospheric radio-frequency Inductively Coupled Plasma (rf-ICP) is used as the high temperature heat source for the new containerless method. Dynamics of melting is compared with the numerical simulations by using an image analysis procedure. A numerical model solves the axisymetric Navier-Stokes equations for both the melt and the surrounding gas. Good agreement between the dynamics of the pendant drops of copper obtained by the experiments and the simulations. Therefore, reasonable surface tensions measured based on the method shows the applicability of the method to ceramics and alloys.
Vibration Study of the Piezo-Driven Pipettes Immersed in Viscous Liquids
Authors: Fan Mingxuan , Agca Yuksel , Critser John , Feng Z. C.
Published: April 2008

Intracytoplasmic Sperm Injection (ICSI) is regarded as one of the most useful assisted reproductive technology (ART). During ICSI, a single spermatozoon is mechanically injected into cytoplasm of an oocyte using a glass needle, called a micro-injection pipette. The micro-injection pipette is usually controlled by a micromanipulator for the precise movement. In the case of rodent ICSI the Piezo-driven pipette is needed. However, one undesirable aspect of the Piezo-driven pipette is that the technicians have to use mercury in the micro-injection pipette in order to achieve consistent results. It is commonly held that the large density of mercury strongly affects the pipette vibration. In this work, we analyze the effect of mercury on the vibration characteristics of the Piezo-driven pipette. The pipette is modeled as a cantilever beam immersed in a viscous liquid. The forces on the pipette by the surrounding liquid include both inertial force and viscous force. The steady state response of the pipette is obtained by the finite element method together with the numerical integration method. We investigate the pipette dynamic responses when different fluids are used as the plug inside the pipette and as the fluid surrounding the pipette. Based on the analysis, we conclude that the effect mercury has on the vibration is not the main reason that it facilitates the ICSI.
Design Options for a Reconfigurable Automotive Engine Assembly Pallet
Authors: Shen Chi-Hung , Gosselin Clement M.
Published: April 2008

The paper describes the functional requirements of an agile pallet in the high volume assembly of automotive engines. Three design approaches to enable the locating pins and the rest pads be reconfigured quickly and accurately in the 3D workspace of the pallet have been identified. The technology options investigated are: a) compact magnetic chucks with high attractive force, b) special fast bonding/debonding adhesives, and c) 3-DOF parallel kinematic mechanisms (PKM). Finite element model analysis, experimental test data, and various system operating issues and economic cost effectiveness are also discussed.
Intrinsic Polymer Optical Fiber Sensors for High-Strain Applications
Authors: Kiesel Sharon , Van Vickle Patrick , Peters Kara , Hassan Tasnim , Kowalsky Mervyn
Published: April 2008

This article proposes intrinsic polymer fiber sensors for the performance-based assessment and health monitoring of civil infrastructure systems. Such sensors would allow the dynamic measurement of large strains as required for structures during earthquake loading. Furthermore, the interferometric nature of the sensor permits high accuracy for such measurements. However, the use of the polymer fiber sensors at large strain magnitudes is not without significant challenges as compared to conventional silica optical fiber sensors due to the finite deformation of the fiber and nonlinear photoelastic effects. This article analyzes the implications of the large deformations on the opto-mechanical response of the sensors, derives the sensor opto-mechanical properties to be obtained through sensor calibrations, and demonstrates the data acquisition method to be utilized for the new sensors.
Counterflow Heat Exchanger Model for Thermal Management of a Compact Catalytic Fuel Processor System
Authors: Dhingra Amit , Im Hong G.
Published: April 2008

Recent progress in the fuel cell technology has attracted research interests in providing hydrogen in a safe and efficient manner. One of viable approaches is to develop on-board catalytic fuel processors which converts higher hydrocarbon fuels into hydrogen. While this is a promising method and the level of catalytic material development is mature, the compact fuel processor system suffers from relatively low efficiency primarily due to the large surface-to-volume ratio causing excessive heat loss to the ambient. In this paper, a systematic modeling approach is presented as an effective tool to undertake extensive parametric study to identify crucial design parameters to accomplish optimal thermal management of the fuel processor system. By adopting a canonical counterflow heat exchanger system, effects of key system parameters, such as reactant and control flow rates, and inlet temperatures, on the system efficiency, conversion, and reactive length are investigated. The model is applied to a partial oxidation reactor and results are discussed.
Evaluation of Bare Die Chip Reliability Due to Underfill Materials During Mechanical Actuation and Thermal Cycling
Authors: Sinha Arv
Published: April 2008

Use of underfill materials to encapsulate ball grid arrays (BGAs) or chip scale packages (CSPs) have become very important in increasing the reliability of area array packages [1]. Underfill enhances the reliability of flip-chip devices by distributing the thermo-mechanical stresses [2, 3]. These stresses are generated due to mechanical actuation and coefficient of thermal expansion mismatch (CTE) [3]. They are required due to high power density of the current chip design to achieve fine bond line at the thermal interface material in order to dissipate heat. In this paper, details of reliability assessment using the finite element method and actual test data will be presented and discussed.
The Advisor, a Fuzzy Knowledge-Based System for Rapid Instrumentation and Control Using a Taguchi-Based Quality Function: Part I — Theory
Authors: Tantra Riko , Masada Glenn Y.
Published: April 2008

A fuzzy knowledge-based software system, called The Advisor, is developed for mechanical designers to rapidly select instrumentation and control system solutions. Its knowledge-based system uses application constraints to select feasible solutions, and its fuzzy logic algorithms rank those solutions based upon user preferences. A new Quality Function, inspired by the Taguchi Quality Function, is proposed to combine quantitative and linguistic information in the fuzzy decision-making inference engine to better capture human tradeoff behavior in the equipment selection process. To date, a Motor Advisor and a Temperature Sensor Advisor have been developed and successfully tested. Part I of this paper presents the theory and methodology of The Advisor, its component algorithms to support the selection of motor systems, and the implementation of the new Quality Function in the Motor Advisor. Part II tests The Advisor in the selection of a load motor, motor driver, and motor controller in a motor failure design project.
Tailored Nanoscale Contrast Agents for Magnetic Resonance Imaging
Authors: Barker Alex J. , Cage Brant , Russek Stephen , Garg Ruchira , Shandas Robin , Stoldt Conrad R.
Published: April 2008

Two potential molecular imaging vectors are investigated for material properties and magnetic resonance imaging (MRI) contrast improvement. Monodisperse magnetite (Fe3O4) nanocrystals ranging in size from 7 to 22 nm are solvothermally synthesized by thermolysis of Fe(III) acetylacetonate (Fe(AcAc)3) both with and without the use of heptanoic acid (HA) as a capping ligand. For the resulting Fe3O4 nanocrystals, X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and superconducting quantum interference device magnetometry (SQUID) is used to identify the average particle size, monodispersity, crystal symmetry, and magnetic properties of the ensembles as a function of time. The characterization study indicates that the HA synthesis route at 3 hours produced nanoparticles with the greatest magnetic anisotropy (15.8 × 104 J/m3). The feasibility of Fe8 single molecule magnets (SMMs) as a potential MRI contrast agent is also examined. SQUID magnetization measurements are used to determine anisotropy and saturation of the potential agents. The effectiveness of the Fe3O4 nanocrystals and Fe8 as potential MRI molecular probes is evaluated by MRI contrast improvement using 1.5 mL phantoms dispersed in de-ionized water. Results indicate that the magnetically optimized Fe3O4 nanocrystals and Fe8 SMMs hold promise for use as contrast agents based on the reported MRI images and solution phase T1/T2 shortening.
Automated Optimal Design for Manufacturability of Sheet/Plate Assemblies
Authors: Guidea Sorin , Nye T. J.
Published: April 2008

A wide variety of products are manufactured from raw materials that are in the form of sheets or plates. Once the product is designed, parts are unfolded or flattened into flat blanks, which are nested onto the raw material for cutting. Optimization of nesting and packing problems has been an active research field for many years, and many good algorithms have been created. These algorithms have a fundamental limitation, however, in that they assume the set of blanks to be nested is fixed. In this work we relax this assumption, and by linking a parametric CAD system, a part-unfolding module and a sheet-nesting module that all intercommunicate, nests are created which maintain the parametric dimensions of the assembled product. Given a nest of the set of required blanks, dimensions of the blanks are optimized for a particular objective, such as maximizing raw material utilization or minimizing total use of raw material, subject to assembly, part dimension, part and blank dimension constraints. Once optimized, these blank dimensions are returned to the CAD system to update the product model. Through the use of this system, a designer can simultaneously optimize all the dimensions within a product to minimize manufacturing costs early in the design phase while maintaining acceptable product performance. This paper will demonstrate a prototype of this DFM system, discuss issues such as performance improvement through randomized trials, and suggest how additional design objectives (e.g., strength to weight ratio, stiffness, etc.) can be integrated with the reduced manufacturing cost objective.
Suppression of Edge Delamination Through Meso-Scale Structuring
Authors: Baucom J. N. , Qidwai M. A. , Pogue W. R. , Thomas J. P.
Published: April 2008

We are developing a new class of fiber-reinforced polymer composite materials to facilitate imbedding multifunctional features and devices in material systems, and to manage interlaminar stresses at free edges and cut-outs. The idea is centered on introducing one more level of design space by composing plies with individual tiles possessing the same degrees of design freedom that are associated with individual plies. In this work, we have focused on tiling schemes that will allow blending of laminates (lay-ups), where a lay-up suitable for suppressing interlaminar stresses could be placed at necessary locations whereas another lay-up could be used for the main objective. This results in the introduction of matrix-rich tile-to-tile interface pockets in the blending region. Preliminary mechanical testing shows that uniaxially reinforced tiled composites attain stiffness levels near those of their traditional counterparts, yet with a potential degradation of strength. We used the finite element method to investigate the effects of resin-rich pocket size, the use of supporting continuous layers, tile size, and tile overlapping (interface stacking) schemes on stress distribution around interfaces in uniaxially reinforced tiled composites, with the aim to identify parameters controlling overall strength. We discovered that alignment of the resin-rich pockets through the thickness exacerbates stress-concentration and that outer continuous layers on the composite may help in better load transfer. As a first step in the application of this technique for the suppression of delamination at the free edges of holes in laminates, a bilaminate material was modeled, and the concept was shown to be effective in the suppression of edge delamination.
Bounds on Two-Phase Flow: Part II — Void Fraction in Circular Pipes
Authors: Awad M. M. , Muzychka Y. S.
Published: April 2008

Theoretical and empirical models for the gas void fraction (α) are reviewed. Simple rules are developed for obtaining rational bounds for the void fraction in two-phase flow. The lower bound is based on the separate cylinders formulation for turbulent-turbulent flow that uses the Blasius equation to predict the Fanning friction factor. The upper bound is based on the Butterworth relationship that represents well the Lockhart-Martinelli correlation. These two bounds are reversed in the case of liquid fraction (1−α). The bounds models are verified using published experimental data of void fraction versus mass quality at constant mass flow rate. The published data include different working fluids such as R-12 and R-22 at different pipe diameters, different pressures, and different mass flow rates. It is shown that the published data can be well bounded for a wide range of mass qualities, pipe diameters, pressures and mass flow rates. Further comparisons are made using the published experimental data of void fraction (α) and liquid fraction (1−α) versus the Lockhart-Martinelli parameter (X), for different working fluids such as R-12, R-22 and air-water mixtures.
Robust Control for Networked Control Systems With Admissible Parameter Uncertainties
Authors: Ji Kun , Kim Won-Jong
Published: April 2008

In this paper, robust H∞ control problems for networked control systems (NCSs) with network-induced time delays and subject to norm-bounded parameter uncertainties are presented and solved. Based on a new discrete-time model, two approaches of robust controller design are proposed—design of a memoryless state-feedback controller and design of a dynamic state-feedback controller. The proposed memoryless state-feedback controller design method is given in terms of linear matrix inequalities (LMIs), and the delay bound can be computed by using the standard LMI techniques. A numerical example is given to illustrate the feasibility and effectiveness of this methodology. The proposed dynamic state-feedback controller design method is based on a discrete-time Artstein transform. With the sufficient conditions for robust stability and H∞ control developed in this paper, we also derive the upper bound of network-induced time delays and the lower bound of the network date-transmission rate that can be used as a guideline in choosing proper networks as communication media for NCSs. We constructed an NCS test bed to experimentally verify the feasibility and effectiveness of proposed design methodologies.
Immunomagnetic Separation in Microchannels: From MEMS to BioNEMS
Authors: Sinha Ashok , Ganguly Ranjan , Puri Ishwar K.
Published: April 2008

Conventional methods of monitoring and testing water quality involve collection of the sample to be tested and its subsequent analysis in a research laboratory for which some procedures may not be feasible or even accessible under certain field situations. Therefore, next generation sensors are required. Herein, an innovative concept that combines a micromixer and microparticle trap is proposed that should enable more rapid pathogen detection in contaminated water. In it, immunomagnetic separation (a procedure [1,2] that is well practiced in the field of immunochemistry) is scaled down from the benchtop to the microscale. Our design is generic, i.e., design is not limited to the detection of waterborne biological agents, but can be used for other forms of chemical analysis. Testing for waterborne bacteria requires analysis methods that must meet a number of challenging criteria. Time and sensitivity of analysis are the more important limitations. Bacterial detection methods have to be rapid and very sensitive since the presence of even a small pathogenic sample may sometimes constitute an infectious or otherwise harmful dose. Selective detection is also required because small numbers of pathogenic bacteria are often present in a complex biological environment along with many other nonpathogenic organisms. As an example, the infectious dosage of a pathogen such as E. coli O157:H7 or Salmonella is as low as 10 cells and the existing coliform standard for E. coli in water is 4 cells: 100 ml [3].
The Influence of the Bauschinger Effect on the Combined Stress Intensity Factors for 3-D Internal Radial Cracks in a Fully or Partially Autofrettaged Gun Barrel
Authors: Perl M. , Levy C. , Rallabhandy V.
Published: April 2008

The influence of the Bauschinger Effect (BE) on KIN — the combined, Mode I, 3-D Stress Intensity Factor (SIF) distributions for arrays of radial, internal, surface cracks emanating from the bore of a fully or partially autofrettaged gun barrel is investigated. A thorough comparison between the combined SIFs for a “realistic” - Bauschinger Effect Dependent Autofrettage (BEDA) and those for an “ideal” - Bauschinger Effect Independent Autofrettage (BEIA) is performed. The 3-D analysis is performed via the finite element (FE) method and the submodeling technique, employing singular elements along the crack front. Both autofrettage residual stress fields, BEDA and BEIA, are simulated using an equivalent temperature field and more than 1200 different crack configurations are analyzed. SIFs for numerous crack arrays (n=1 to 64 cracks), a wide range of crack depth to wall thickness ratios (a/t=0.01 to 0.2), various ellipticities (a/c=0.5 to 1.5), several values of the yield-stress to pressure ratio (ψ=σyp/p=1.93 to 3.55) and different levels of autofrettage (ε=30% to 100%) are evaluated. The level of autofrettage efficiency for all BEDA cases is determined, and is thoroughly compared with that of BEIA. The largest combined SIF KNmax can be found at any angular location along the crack front and can reach its largest values for arrays of any number of cracks from 1 to 16, and therefore needs to be evaluated for each particular case. The Bauschinger Effect is found to have a dramatic detrimental impact on the fatigue life of the gun barrel. Even in the case were autofrettage has its minimal beneficial effect, (ψ=1.93), the BE can reduce the fatigue life of the barrel by a factor of 2 to 5. In other cases this factor can reach orders of magnitude, and in extreme cases, when autofrettage completely overcomes the pressure yielding a nil KNmax, this factor might become infinite, i.e., an infinite fatigue life for BEIA versus a finite fatigue life for BEDA. For a partially autofrettaged barrel, it is found that the lower the level of autofrettage, the smaller the Bauschinger Effect is. Increasing the level of autofrettage beyond ε=60% is found to be counterproductive, and therefore, it is not recommended.
Design Implementation and Assessment of a Suite of Multimedia and Hands-on Active Learning Enhancements for Machine Design
Authors: Jensen Dan , Wood John , Dennis Scott , Wood Kristin , Campbell Matthew
Published: April 2008

Over the last eight years, the Machine Design courses at the United States Air Force Academy and at the University of Texas, Austin have evolved through the development, implementation and assessment of extensive active learning methods. In particular, the courses have evolved to include extensive hands-on projects that are integrated throughout the course as well as a significant multimedia component. The hands-on educational innovations, which promote experiential investigation using devices such as remote controlled cars, Lego RoboLab, and reverse engineering of consumer products, have received very positive assessment. The multimedia content, which includes extensive foundational content on Mechanics of Materials as well as a separate multimedia experience for learning about planetary gear systems, has also been assessed and received very affirmative feedback. The assessment of these active learning educational innovations has been multifaceted. Quantitative components of the assessment have included student end-of-course critiques, homework, specific exam questions and survey data. Qualitative assessment has been achieved through focus groups as well as both written and verbal feedback from students and professors using the active learning aids. Although the majority of the assessment has been positive, we have also received important constructive criticism during the development of these educational enhancements. The “iterative” development of these active learning techniques has involved responding to these criticisms and reassessing the program’s effectiveness. In this paper, we first provide an overview of the previous work done in this area, then move on to show new developments and related assessment. In particular, new assessment, which is correlated with Myers Briggs personality types, is reported, showing results of the current integrated use of active learning techniques, including hands-on and multimedia experiences. In this light, the current paper should work as a roadmap for others who desire to integrate active learning into their courses, whether they are courses in Machine Design or not.
Analog and LabView-Based Control of a Maglev System With NI-ELVIS
Authors: Sinha R. , Nagurka M. L.
Published: April 2008

This paper investigates the control of a low cost vertical-axis maglev system for mechatronics and controls education. The tabletop maglev system consists of an electromagnetic coil that levitates a ferrous object using an infrared sensor to determine the object’s position. Based on the sensor output, the controller adjusts the coil current, thus changing the magnetic field controlling the levitated object’s position. A second electromagnetic coil is used to provide known disturbances. The paper develops the underlying theory for magnetic levitation and presents the results of experiments with classical controllers implemented both as analog circuits and in software-based virtual instruments. Analog controllers, such as PID-type controllers, were implemented as simple circuits on National Instruments’ Educational Laboratory Virtual Instrumentation Suite (NI-ELVIS) prototyping board. NI-ELVIS offers a LabVIEW-based prototyping environment for readily experimenting with different controller circuits. It consists of a multi-function data acquisition device and a custom-designed bench-top workstation with a prototyping board. In addition to analog control circuits, a suite of LabVIEW-based controllers were developed which offer in software a rapid way to change control strategies and gains and explore the effect on the physical system.
Minimum-Zone Circularity Evaluation Using Particle Swarm Optimization
Authors: Ramaswami Hemant , Kovvur Yashpal , Anand Sam
Published: April 2008

Robust and accurate evaluation of form tolerances is of paramount importance in today’s world of precision engineering. Present-day Coordinate Measuring Machines (CMMs) operate at high speed and have a high degree of accuracy and repeatability which are capable of meeting the stringent measurement requirements. However, the evaluation algorithms used in conjunction with them are not robust and accurate enough, because of the highly non-linear nature of the minimum-zone circularity formulation. Evolutionary algorithms have proved effective in solving constrained non-linear optimization problems. In this paper, Particle Swarm Optimization (PSO), which is one of the most recent and popular evolutionary algorithms, is employed to evaluate the minimum-zone circularity. The PSO approach imitates the social behavior of organisms such as bird flocking and fish schooling. It differs from other well-known Evolutionary Algorithms (EA) in that each particle of the population, called the swarm, adjusts its trajectory toward its own previous best position, and toward the previous best position attained by any member of its topological neighborhood. The constrained nonlinear model is rewritten as an unconstrained non-linear model using the penalty-function approach. The methodology is validated by testing on several simulated and experimental datasets and yields better results than other existing minimum-zone algorithms.
Acquisition of High Precision Images for Non-Contact Atomic Force Microscopy via Direct Identification of Sample Height
Authors: Pishkenari H. N. , Jalili Nader , Meghdari A.
Published: April 2008

Atomic force microscopes (AFM) can image and manipulate sample properties at the atomic scale. The non-contact mode of AFM offers unique advantages over other contemporary scanning probe techniques, especially when utilized for reliable measurements of soft samples (e.g., biological species). The distance between cantilever tip and sample surface is a time varying parameter even for a fixed sample height, and hence, difficult to identify. A remedy to this problem is to directly identify the sample height in order to generate high precision, atomic-resolution images. For this, the microcantilever is modeled by a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Since in most practical applications only the microcantilever deflection is accessible, this measurement is utilized to identify the sample height in each point. Using the proposed approach for identification of the sample height, the scanning speed can be increased significantly. Furthermore, for taking atomic-scale images of atomically flat samples, there is no need to use the feedback loop to achieve setpoint amplitude. Simulation results are provided to demonstrate the effectiveness of the approach and suggest the most suitable technique for the sample height identification.
Tolerance Analysis Considering Weld Distortion by Use of Pregenerated Database
Authors: Lee Dongyul , Kwon Ki Eak , Lee Jaeyeol , Jee Haeseong , Yim Hyunjune , Cho Seong Wook , Shin Jong Gye , Lee Gyubong
Published: April 2008

A general and efficient methodology has been developed to analyze dimensional variations of an assembly, taking into account of the weld distortion. Weld distortion is generally probabilistic because of the random nature of welding parameters such as the welding speed, maximum welding temperature, ambient temperature, etc. The methodology is illustrated by a very simple example of two perpendicular plates fillet-welded to each other. Two steps comprise the methodology: establishment of a weld-distortion database, and tolerance analysis using the database. To establish the database, thermo-elasto-plastic finite element analyses are conducted to compute the weld distortion for all combinations of discrete values of major welding parameters. In the second step of tolerance analysis, the weld distortion retrieved from the database is used in addition to the dimensional tolerances of the parts. As a result of such an analysis, sensitivities of the assembly’s dimensional variations to the part tolerances and weld distortion are obtained, which can be help improve the dimensional quality of the assembly.
System Hierarchy Optimization Method for MEMS Applications
Authors: Liu Nan , Manoochehri Souran
Published: April 2008

A new design optimization methodology for Micro-Electro-Mechanical Systems (MEMS) application is presented. The optimization approach considers minimization of several uncertainty factors on the overall system performance while satisfying target requirements specified in the form of constraints on micro-fabrication processes and materials system. The design process is modeled as a multi-level hierarchical optimal design problem. The design problem is decomposed into two analysis systems; uncertainty effects analysis and performance sensitivity analysis. Each analysis system can be partitioned into several subsystems according to the different functions they perform. The entire problem has been treated as a multi-disciplinary design optimization (MDO) for maximum robustness and performance achievement. In this study, the analysis results are provided as optimized device geometry parameters for the example of the selected micro accelerometer device.
Assessing Hypercube Sampling Techniques for Risk Assessment
Authors: Manteufel Randall D. , Pleming Jason B.
Published: April 2008

Two variations of hypercube sampling techniques are introduced and computationally tested using benchmark problems. The methods are variations of the Latin hypercube sampling (LHS) and incremental-fractional LHS scheme. Both can be described as stratified sampling with one sample per strata. Because they ensure uniform marginals, they are observed to have computational advantages for linear problems where weighted response statistics are sought. Advantages are less pronounced for non-linear responses and sorted statistics, which is often the case for risk analysis. The complementary cumulative distribution is identified as being helpful in assessing a methods performance. Both methods are applied to an application problem having multiple responses of interest and 48 uncertain inputs. The hypercube methods are noted to produce estimates of the mean with orders-of-magnitude lower variance than that of simple random sampling.
Aerodynamic Losses of a Cambered Turbine Vane: Influences of Surface Roughness and Freestream Turbulence Intensity
Authors: Zhang Qiang , Ligrani Phillip M.
Published: April 2008

The effects of surface roughness and freestream turbulence level on the aerodynamic performance of a turbine vane are experimentally investigated. Wake profiles are measured with three different freestream turbulence intensity levels (1.1%, 5.4% and 7.7%) at two different locations downstream of the test vane trailing edge (one and 0.25 axial chord lengths). Chord Reynolds number based on exit flow conditions is 0.9 × 106. The Mach number distribution and the test vane configuration both match arrangements employed in an industrial application. Four cambered vanes with different surface roughness levels are employed in this study. Effects of surface roughness on the vane pressure side on the profile losses are relatively small compared with suction side roughness. Overall effects of turbulence on local wake deficits of total pressure, Mach number, and kinetic energy are almost negligible in most parts of the wake produced by the smooth test vane, except that higher freestream losses are present at higher turbulence intensity levels. Profiles produced by test vanes with rough surfaces show apparent lower peak values in the center of the wake. Integrated Aerodynamic Losses (IAL) and area-averaged loss coefficient YA are also presented and compared with results from other research groups.
Planar Peg-in-Hole Insertion Using a Stiffness Controllable Pneumatic Manipulator
Authors: Zhu Yong , Barth Eric J.
Published: April 2008

This paper presents a method for the impedance control of a pneumatic manipulator for peg-in-hole tasks without using a load cell. The control methodology presented contains a sliding mode force controller and an adaptive pressure summation relationship, which enforces the controllable natural stiffness of the pneumatic actuator. This is accomplished by utilizing two three-way proportional spool valves for each degree-of-freedom instead of a four-way valve typically used in fluid power control. Combinations of intrinsic stiffness provided by the compressibility of air and closed-loop stiffness provided by impedance parameters are studied. Experimental results are shown demonstrating that gentle transition from non-contact to contact tasks can be achieved without the use of a load cell by taking advantage of the intrinsically low stiffness of a pneumatic manipulator. Experimental results are also shown demonstrating sensorless (no load cell) force-guided insertion of a planar peg-in-hole task with position uncertainties (hole location not precisely known).
A Clean Slate: Designing a Mechanical Systems Concentration Within a New Engineering Program
Authors: Danielson Scott , Henderson Mark , Kuo C. Y. , Roberts Chell , Morrell Darryl , Grondin Robert , Hinks Robert , Sugar Thomas
Published: April 2008

In July of 2003, a feasibility assessment and preliminary planning process began for creation of a new engineering program at Arizona State University’s Polytechnic campus. The process began with a blank slate and gave the founding faculty team, composed of civil, electrical, industrial and mechanical engineers, unprecedented freedom and flexibility in the design. The team adapted an engineering design process to develop the program’s curricular structure and content. A novel, flexible curriculum addressing the needs of engineering graduates in the modern, global workplace resulted. In this paper, we describe briefly the design process, the resulting curriculum structure, and, in more depth, the program’s mechanical systems concentration.
Structured Adaptive Mesh Refinement (SAMR) Simulation of a Buoyant Helium Plume
Authors: Tandon Mohit , Rawat Rajesh , Smith Philip J. , Wissink Andrew M. , Gunney Brian T. N.
Published: April 2008

Large-Eddy Simulations (LES) are done for 7.3 cm diameter helium plume using Local Mesh Refinement in the near source region i.e., X/Dp < 2. Constant coefficient Smagorinsky Model was used. The validation of code was conducted by comparing with the experimental data collected at NIST. The simulations are validated for two different inlet velocities. Simulation results of time-averaged velocity and helium concentration fields show good agreement with experimental data in the near source regions. Discrepancies were observed between the simulations and the experimental data in regions downstream the refined region. The cause of these discrepancies is attributed to unresolved vorticity generated by buoyancy.
Intralaminar Reinforcement for Biomimetic Toughening of Bismaleimide Composites Using Nanostructured Materials
Authors: Tiano Thomas , Roylance Margaret , Harrison Benjamin , Czerw Richard
Published: April 2008

Many conventional composite materials are composed of multiple layers of continuous fiber reinforced resin produced by lamination of b-staged prepreg and subsequent cure. These materials exhibit very high strength and stiffness in the plane, dominated by the properties of the fibers. The Achilles heel of such composites is the interlaminar strength, which is dependent on the strength of the unreinforced resin, often leading to failure by delamination under load. Current methods for increasing the interlaminar shear strength of composites consist of inserting translaminar reinforcement fibers through the entire thickness of a laminated composite, such as z-pin technology developed by Foster-Miller [1]. While effective, this technique adds several processing steps, including ultrasonic insertion of the z-pins into the laminate, subsequently causing a significant cost increase to laminated composites. Described in this paper is a process utilizing single-walled carbon nanotubes (SWNTs) and vapor grown carbon nanofibers as reinforcing elements promoting interlaminar shear strength and toughness in carbon fiber/bismaleimide (BMI) resin composites. The resulting composites mimic the natural reinforcing mechanism utilized in insect cuticles. Three different methods of increasing the affinity of these carbon nanofillers for the BMI matrix were explored. The mechanical properties of these composites were assessed using end notch flexure testing. The results indicated that including nanofiller at the laminae interface could increase the interlaminar shear strength of carbon fiber/BMI composites by up to 58%. SEM micrographs revealed that the nanofiller successfully bridged the laminae of the composite, thus biomimicking the insect cuticle. Composite fabrication techniques developed on this program would have a wide variety of applications in space and aerospace structures including leading and trailing edges of aircraft wings.