bluuebunny/crossref_metadata_2025 huggingface dataset:
Framework for Network Based Manufacturing Training Through Telehaptics
Authors: Joshi Dhananjay , Kesavadas T.
Published: May 2008

Use of force feedback, or haptics, has increased the realism of virtual reality simulation systems over the last few years. In this research we propose a framework for the communication of haptic sensation in a shared environment over the Internet for developing novel manufacturing training system. This framework allows re-experiencing the sensation at geographically remote location by transmitting the haptic information over a TCP/IP network. We call this Tele-haptics. Using Tele-haptics, we propose a system where we can capture skill sets commonly associated with complex tasks such a die and tool polishing and communicate this to trainee over the internet. The trainee, using a Phantom Haptic system, can experience the process of polishing based on the master’s input. The framework for haptic communication is experimentally evaluated. The results of the experimental evaluation suggest that it is possible to transmit and recreate haptic features such as geometry and force characteristics.
Integration of Modern Software Tools for Virtual Prototyping and Intelligent Control of Mechanical Systems
Authors: Nagchaudhuri Abhijit
Published: May 2008

Modern software tools have enhanced modeling, analysis and simulation capabilities pertaining to control of dynamic systems. In this regard MSC. Software’s Working Model and Mathwork’s MATLAB software environments have been extensively utilized in recent years in the industry as well as in academia. In this paper simulation studies involving PID (Proportional + Integral + Derivative) control and fuzzy logic control of simple mechanical devices are reported. The simulations are performed by integrating virtual prototyping capability of Working Model and the computational engine of MATLAB. The integration of the two software tools provide a powerful platform for studying different control algorithms for a variety of mechanical and mechatronic devices.
An Evaluation of Thermal Enhancements to Flip-Chip-Plastic Ball Grid Array (FC-PBGA) Packages
Authors: Ramakrishna K. , Lee T.-Y. Tom
Published: May 2008

Flip-chip plastic ball grid array (FC-PBGA) packages are fast becoming the industry norm, in particular in the performance and cost driven consumer electronics sector. Since high thermal conductivity (k∼15–20 W/(m K)) ceramic substrate is replaced by a low conductivity (k∼0.2–0.5 W/(m K)) organic substrate in the FC-PBGA packages, enhancement of thermal performance of these packages to meet ever increasing demands is crucial for their wide spread use. In this study, enhancements to thermal performance of FC-PBGA packages due to material and design changes and external means such as heat spreaders and overmolding of the packages have been evaluated by solving a conjugate heat transfer models using the methods of computational fluid dynamic. The thermal enhancements evaluated in this study include the effect of thermal conductivity of the chip to package interconnect due to change in underfill material and the C4 bump pitch, effect of package to printed wiring board (PWB) interconnection through the use of thermal balls, effect of a heat spreader on the backside of the die, and overmolding the die without and with a heat spreader. Thermal performance of the FC-PBGA packages have been studied using junction to ambient thermal resistance, Θja, junction-to-board thermal resistance Ψjb, and junction to case thermal resistance ΨjT under natural and forced convection for freestream velocities up to 2 m/s and the for following ranges of parameters: Substrate size: 25 to 35 mm, die size: 6.19×7.81 mm (48 mm2 area) and 9.13×12.95 mm (118 mm2 area), C4 pitch: 250 mm, 150 mm and below, underfill material thermal conductivity: 0.6 to 3.0 W/(m K), no thermal balls between the package and the PWB to 9×9 array of thermal balls on 1.27 mm square pitch, and with copper heat spreader on the back of the bare and overmolded die. Based on previous experience, predictions in this study are expected to be within ±10% of measured data. The following conclusions are drawn from this study: 1. It is concluded that the thermal conductivity of the underfill materials in the range 0.6 to 10 W/(m K) is negligible. 2. It is also concluded that the bump pitch can decrease thermal resistances by 12 to 15 %. The change may be smaller with large die area. 3. Thermal balls (C5) connected to the PTHs in the PWB can decrease thermal resistance by about 10% to 15% as the number of thermal balls & PTHs increase zero to 9×9 on 1.27 mm pitch. The effect die size on this thermal enhancement is more noticeable on Ψjb. 4. Heat spreader on the back of the die decreases Θja by a small amount (6–7%) in natural convection and a large amount, about 25% in forced convection. 5. Overmolded die with heat spreader on the top of the overmold provides better thermal enhancement than heat spreader alone up to about 1 m/s. Beyond 1 m/s, heat spreader (without overmold) performs slightly better.
Time and Frequency Domain Investigation of the Static and Dynamic Characteristics of Micro-Drilling
Authors: Guo Anping , Batzer Steve , Roth John
Published: May 2008

In this paper, the dynamic characteristics of micro-drilling process under different cutting conditions and the resulting correlation to tool wear have been studied. Two types of drills, three spindle speeds and two kinds of workpiece materials were used. In-process cutting forces and accelerations were measured. The signals were analyzed in both the time and frequency domains. Some interesting phenomena were observed in the dynamic time-history response during drilling. Progressive functions with the proper order were obtained to describe the curve of the average thrust force with the number of the holes drilled. Dynamic features which were sensitive to tool wear were found. The changing trends of these dynamic features as the drill wear progresses show a feasibility to develop an on-line drill wear monitoring system by evaluating the changes in dynamic features.
Dynamic Reduced Electrothermal Model for Integrated Power Electronics Modules (IPEM): Part I — Thermal Analysis
Authors: Herna´ndez-Mora M. , Gonza´lez J. E. , Ve´lez-Reyes M. , Orti´z J. M. , Pang Y. , Scott E.
Published: May 2008

This paper presents a reduced mathematical model using a practical numerical formulation of the thermal behavior of Integrated Power Electronics Modules (IPEM). This model is based on the expanded Lumped Thermal Capacitance Method (LTCM), in which the number of variables involved in the analysis of heat transfer is reduced to only time. Applying this procedure a simple, non-spatial, but highly non-linear model is obtained. Steady and transient results of the model are validated against results from a thermal analysis software tool, FLOTHERM 3.1™. A comparison between thermal results obtained with the reduced model and experimental data is presented indicating a need for incorporating the dynamic electrical performance in the reduced model. The development of this model presents an alternative to reduce the complexity level developed in commercial multidimensional and transient software for power electronics applications.
Teaching Capstone Design to a Multiple Location Team
Authors: Todd Beth A. , Shepard W. Steve
Published: May 2008

The Department of Mechanical Engineering at the University of Alabama offers its BSME degree through distance education to students in Dothan, Alabama, located approximately 240 miles from the campus in Tuscaloosa. These off-site students are full-time employees, many are machinists or technicians working swing shift, with the desire to become engineers. The goal of the program described here is to provide these non-traditional students with the same technical and professional content in their courses as students on campus. As the first group of students finished their degree program, the lates challenge has been to create a team-based design experience with traditional student team members and these distance education students. The purpose of this paper is to discuss the challenges and solutions for teaching capstone design to teams with members at multiple locations. For companies with multiple and multi-national locations, these students should be seen as having an important skill set as new employees.
A Port-Controlled Hamiltonian Approach to Control of an Electrostatic MEMS Actuator
Authors: Maithripala D. H. S. , Berg Jordan M. , Dayawansa W. P.
Published: May 2008

While mechanical, electrical and electromechanical systems may exhibit complex nonlinear dynamics, their behavior is typically governed by relatively simple underlying principles of energy transfer. Modeling methodologies that seek to capture this underlying order give rise to a special form of the equations of motion, called a port controlled Hamiltonian structure with damping (PCHD). Often the natural behavior of a system is unacceptable for a desired application, and must be modified. A body of work on passivity-based control exists that shows how to use Casimir functions—certain invariant quantities of the open-loop PCHD—to reshape the natural dynamics in a desired way. We seek to apply this approach to an electrostatically-actuated MEMS device subject to the saddle-node bifurcation known as snap-through. We show that the equations describing this system do not have an appropriate Casimir function, but that they can be suitably modified through an implementable output feedback. We fully characterize the Casimirs of the modified system, and show how they may be used to eliminate snap-through. Unfortunately the transient behavior of the resulting closed-loop system is governed by the damping of the mechanical subsystem, which may or may not provide adequate performance.
Influence of Unsteady Vortex Structures on Noise Reduction of Windscreens
Authors: Zheng Z. Charlie , Zhang N.
Published: May 2008

The effects of windscreens on low-frequency wind noise reduction were previously investigated using a steady-state computational fluid dynamics model. The current concentration is on higher frequencies where the wind noise reduction is no longer independent of frequencies, and unsteady fluid dynamics is required to provide pressure fluctuation information on the windscreen surface. Flow across an oscillating cylinder is studied as a model problem. An immersed boundary method has been developed to compute the fluid flow. Pressure fluctuations on the surface of a rigid, impermeable windscreen are obtained from the flow computation. Noise reduction effects inside of the windscreen are then calculated based on the integration of surface pressure distributions caused by unsteady vortex structures. The results show that for a cylinder oscillating at a frequency close to the natural vortex shedding frequency, the peak noise sensed at the center of the cylinder is at twice of the oscillation frequency and its second and third harmonics. For a non-oscillating cylinder, the peak noise sensed at the center is at the vortex shedding frequency itself and its second harmonic.
A New Fusion Tracking Algorithm Based on Extended Adalines Model
Authors: Hu Shiqiang , Jing Zhongliang
Published: May 2008

An approach of multi-sensor fusion tracking with extended Adalines model and fuzzy stochastic decision is proposed in this paper. The criterion of multi-sensor fuzzy stochastic decision is presented. An optimal algorithm for weight adjustment is designed combining genetic algorithm with fuzzy reasoning. This optimal algorithm has two important features: adaptation and learning; the effectiveness of the proposed method is illustrated through computer simulation under the circumstances of multi-sensor in target tracking.
Metal Inert Gas (MIG) Welding Process Optimization for Joining Aluminum 5754 Sheet Material Using OTC/Daihen Equipment
Authors: Koganti R. , Karas C. , Joaquin A. , Henderson D. , Zaluzec M. , Caliskan A.
Published: May 2008

The development of lightweight vehicles, in particular aluminum intensive vehicles, require significant manufacturing process development for joining and assembling aluminum structures. Currently, 5xxx and 6xxx aluminum alloys are being used in various structural applications in a number of lightweight vehicles worldwide. Various joining methods, such as MIG, Laser and adhesive bonding have been investigated as technology enables for high volume joining of 5xxx, and 6xxx series alloys. In this study, metal inert gas (MIG) welding is used to join 5754 non-heat-treatable alloy sheet products. The objective of this study is to develop optimum weld process parameters for non-heat-treatable 5754 aluminum alloys. The MIG welding equipment used in this study is an OTC/Daihen CPD-350 welding systems and DR-4000 pulse power supply. The factors selected to understand the influence of weld process parameters on the mechanical properties and metallurgy (weld penetration) include power input (torch speed, voltage, current, wire feed), pulse frequency, and gas flow rate. Test coupons used in this study were based on a single lap configuration. A full factorial design of experiment (DOE) was conducted to understand the main and interaction effects on joint failure and weld penetration. The joint strengths and weld penetrations are measured for various operating ranges of weld factors. Post weld analysis indicates, power input and gas flow rate are the two signficant factors (statistically) based on lap shear load to failure and weld penentration data. There were no 2-way or 3-way interaction effects observed in ths weld study. Based on the joint strength and weld penetration, optimum weld process factors were determined.
The Symmetry Structures of Regular and Chaotic Motions in Non-Smooth Dynamical Systems Under Harmonic Excitations
Authors: Luo Albert C. J.
Published: May 2008

In this paper, the symmetry of motions in non-smooth dynamical systems with two symmetrical constraints under harmonic excitations is investigated to obtain all possible stable and unstable motions. This investigation provides a mathematical foundation for the symmetry of motions in such a class of dynamical systems. It is found that there is an invariant transformation for regular and chaotic motions in symmetrical systems with harmonic excitations. It is observed that the mapping group structures exist. The group property of mapping combinations should be further investigated.
Haptic Sculpting and 5-Axis Pencil-Cut Planning in Virtual Prototyping and Manufacturing
Authors: Zhu Weihang , Lee Yuan-Shih
Published: May 2008

In this paper, a Two-phase approach to tool collision detection and local gouging elimination is proposed for haptic pencil-cut of sculptured surfaces. Pencil-cut is a special kind of machining operation, whose purpose is to use relatively smaller tools to remove rest material on the corners or highly curved regions that are inaccessible by bigger tools. Tool orientation determination and tool collision avoidance are critical issues for 5-axis pencil-cut tool path planning. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper.
A Mechanical Model for Dynamic Behavior of Large Amplitude Liquid Sloshing in Partially Filled Tank Vehicles
Authors: Xu Liang , Dai Liming
Published: May 2008

A mechanical model of liquid sloshing is developed to investigate the longitudinal dynamic characteristics of partially filled liquid cargo tank vehicles during typical straight-line driving. The dynamic liquid motion is modeled by utilizing a mechanical system that describes the behavior of the liquid motion as a linear spring-mass model augmented with an impact subsystem for longitudinal oscillations. Computer simulation of tank vehicles under rough road conditions is performed by incorporating the forces and moments caused by liquid motion into the pitch plane vehicle model. The fifth wheel loads and the normal axle loads, which are key factors to vehicle structure design, fatigue analysis and vehicle performance characteristics, are computed using the mechanical system approach in order to investigate the influence of liquid motion. This study presents a new approach to investigate the longitudinal dynamic behavior of partially filled tank vehicles under large amplitude liquid sloshing.
Density and Compressibility Effects on the Structure of Supersonic Mixing Layer: Experimental Results and Similarity Analysis
Authors: Menaa M. , Dussauge J. P.
Published: May 2008

Self-similar solutions for mixing layers in supersonic flow and in subsonic flow with variable density are examined. The equation for the velocity profile is derived for a unity turbulent Prandtl number and/or prescribed density distributions. It is found that the shape of the velocity profile is not sensitive to Mach number and is nearly the same for supersonic layers with moderate convective Mach numbers and in low speed flows with variable density: in such conditions, the only compressibility effect is found on the rate of spread. It is also found that turbulent friction is a function of Mach number and of velocity and density ratios. The effect of these last parameters on turbulent friction in low speed layers is proposed. Finally the scaling for turbulent shear stress last parameters on turbulent friction in low speed layers is proposed. Finally the scaling for turbulent shear strees in supersonic mixing layer is discussed. A simple formulation is proposed, in which the effects of density ratio and convective Mach number can be sepearated, as it is usually done for the rate of spread.
Thermal Modeling of a Liquid-Cooled PM Traction Motor
Authors: Jih Edward , Abraham Thomas , Stella Stephen , Davis Roy , Dinger Bert , Ong Raymond
Published: May 2008

The electric motor plays a critical role for the applications of the Hybrid Electric Vehicle and Fuel Cell Electric Vehicel. It is also well known that thermal constraints represent one of the main limitations in the performance of the electric motor. For example, the electric motor will be short-circuited if the insulation coatings of the copper wire bundles fail. Furthermore, the performance of the permanent magnet electric motor reduces significantly as the rotor magnet temperature increases. In this study, a series of Computational Fluid Dynamics analyses were performed for the design of a liquid-cooled permanent magnet electric motor to achieve better thermal performance. Several thermal tests of a partial permanent magnet traction motor assembly (stator and housing only) were also performed to determine effective properties of the stator slot and thermal contact resistance between stator and housing that may vary due to the manufacturing process. A simplified thermal network model of this system was established from the Computational Fluid Dynamics analyses. Then the critical heat transfer path of this system was identified.
Effect of Manufacturing and Assembly Process Variations on the Crash Behavior of a Hybrid Aluminum Front-End Structure
Authors: Caliskan Ari G. , Koganti Rama P.
Published: May 2008

In this work, the crash behavior of a hybrid aluminum front-end structure was studied. From the test results, it was shown that overall the structure absorbed the required impact energy. An initial CAE model, which was created prior to the test, predicted the initial portion of the impact pulse. However, beyond the point where weld and joint failure initiated the model over predicted the results. Since the model did not simulate the weld failures, a more detailed model of the front-end structure was created to account for these failures. Unlike steel, the Heat-Effected-Zone (HAZ) around the welds in heat-treatable aluminum alloys exhibit significantly lower yield and ultimate stress than the base material. However, the degree to which the properties are reduced and size of the HAZ vary as a function of welding speed, heat input, weld alloy, etc. A series of analysis using a range of the properties around the HAZ showed a corresponding variation in the crash pulse. The range of properties used was based on coupon level tests of the yield and ultimate strength variation around the HAZ. To better understand the effect of the HAZ and other variations within the structure, a stochastic analysis methodology is proposed. This type of analysis will point to significant source(s) within the structure or components that affect the variations in the crash pulse. It is hoped that this information can be used to improve the manufacturing process or aid in the redesign of the structure to lessen the effect of variations.
A Silicon Rate Sensor With Closed-Loop Drive and Sense Circuits
Authors: Wang Frank , Smith Marc , Hobbs Larry , Yan Hai
Published: May 2008

A micromachined vibrating gyroscope rate sensor with closed-loop drive and sense circuits is presented. In addition, the quadrature cancellation implementation is discussed. In order to improve the sensitivity of the rate sensor, frequency tuning of the drive and sense circuits is employed.
An Investigation of Copper Dissolution and Microstructural Development in Lead-Free Solders
Authors: Faizan M. , McCoy R. A. , Lin D. C. , Wang G.-X.
Published: May 2008

Copper dissolution and intermetallic compound (IMC) formation during reflow of soldered joints are critical issues for joint reliability. Most of studies in the literature aimed at the coarsening and growth of the IMC layer of the soldered joints during service and only limited data is available during soldering process. This is particularly true for lead-free solders, which have attracted the attention of researchers just recently. This paper presents an experimental study of copper dissolution and IMC growth of lead-free solders during the reflow process. Solder buttons of either Sn or Sn-3.5wt%Ag were reflowed over a copper (99.9% pure) substrate for various reflow time periods ranging from 10 seconds to 10 minutes. Four reflow temperatures were selected, 232°C, 250°C, 275°C and 300°C for pure tin and 221°C, 250°C, 275°C and 300°C for Sn-3.5%Ag respectively. The average thickness of the grown IMC layer and the amount of copper dissolved during reflow were determined using the images obtained from the metallurgical microscope. The kinetics of IMC growth and Cu dissolution were then quantified and the estimated kinetics parameters can be used to determine the copper dissolution and IMC layer thickness during reflow soldering.
Heat Recovery From Commercial On-Site Power Generation System: Desiccant Dehumidification vs. Absorption Cooling
Authors: Czachorski Marek , Kelly John , Olsen Kevin
Published: May 2008

As commercial building on-site power generation technologies mature to the point of becoming “off-the-shelf” products, the importance of effective heat recovery is demonstrated time and time again in applications where three to six year paybacks typically are necessary to convince building owners to purchase and install these new technologies. This paper explores the effectiveness and economic benefit of different methods of utilizing recoverable heat from on-site power generation equipment in commercial buildings (Cooling, Heating and Power systems – CHP). An optimal configuration of heat recovery options is explored based on analysis of heat recovery from microturbine(s) exhaust to support commercial building heating and cooling/dehumidification needs. Benefits of recovering heat for space heating/domestic hot water production and to support desiccant dehumidification vs. absorption cooling are studied in five different building types (large supermarket, large retail store, medium size office building, full service restaurant and quick service restaurant). Buildings are evaluated at four different geographical locations, allowing additional study of the climatic conditions on the optimum heat recovery system configuration for specific building types. A sophisticated model, incorporating performance algorithms of state-of-the-art power generation, dehumidification and absorption cooling equipment, is used for calculating annual energy/cost savings for CHP systems and optimization of basic parameters, such as generator size/number and heat recovery equipment selection.
Nonlinear Dynamics in Tomlinson’s Model of Atomic Scale Friction
Authors: Conley W. G. , Raman A. , Krousgrill C. M.
Published: May 2008

This work presents a detailed computational and analytical investigation of Tomlinson’s model for atomic scale dry friction. The model describes a prototypical mechanism of energy dissipation from an atom dragged across a periodic atomic lattice and is often used to model the dynamics of friction force microscope tips. While a number of articles in the literature utilize this model, there is little work in the literature that utilizes the computational and theoretical tools of modern nonlinear dynamics in analyzing this model. This research demonstrates that the use of computational nonlinear dynamics techniques provides a deep insight into the mechanisms of chaotic stick-slip phenomena and the speed dependence of frictional forces of atomic scale friction.
The Spatial Motion of a Compliantly Suspended Rigid Body Constrained by Multi-Point Frictional Contact
Authors: Huang Shuguang , Schimmels Joseph M.
Published: May 2008

This paper addresses methods for determining the motion of an elastically suspended rigid body interacting with frictional surfaces at multiple locations. The methods developed assume: 1) that the motion of the base from which the body is suspended and the elastic behavior of the suspension are known, 2) that inertial forces are negligible (motion is quasi-static), and 3) that the interaction is characterized by Coulomb friction. The derived coupled sets of spatial rigid body equations are used to determine both the unknown direction of the friction force (at each point of contact) and the unknown motion of the rigid body.
Assembly Variant Design Methodology
Authors: Wang Aihu , Nagi Rakesh
Published: May 2008

The distributed and horizontally integrated manufacturing environment in Agile Manufacturing (AM) paradigm demands for new product development methods that posses favorable advantages over conventional manufacturing approaches developed for vertically integrated environments. To cater for this need, this paper discusses the assembly variant design methodology. First, the complementary assembly modeling concept is briefly introduced, which is further materialized as two kinds of assembly models: assembly variants model (AVM) and assembly mating graphs (AMG). The former explicitly captures the hierarchical and functional relationships between constituent components while the latter explicitly captures the mating relationships at the manufacturing feature level. Then the assembly variant design methodology, which is based on these assembly models, is developed based on the concept of Constraint Group (CG). The matching components are searched and retrieved from the AVM and then the CGs are identified by manipulating the AMGs. Finally, the assembly variant design process is formulated as a Mixed Integer Linear Programming (MILP) problem which is solved using a standard solver. Numerical examples are given to verify the feasibility of this method. This framework provides a systematic approach to facilitate the variant design of complex assembly products in the agile manufacturing environment.
Compliant Mechanical Amplifier Design Using Multiple Optimally Placed Actuators
Authors: Bharti Smita , Frecker Mary
Published: May 2008

The paper discusses a methodology for designing compliant mechanisms with piezoelectric actuation to obtain maximized deflection and force at output. The focus is on design of compliant mechanisms with multiple optimally placed and sized piezoelectric actuators. Thus the number, length and position of actuators in the body of the compliant mechanism are optimized in addition to maximizing the output deflection and force. Results demonstrate that compliant mechanisms with multiple, optimally placed actuators outperform those with a single actuator placed at a predetermined location.
LES of Particle-Laden Flow With Inter-Particle Collisions
Authors: Gorokhovski Mikhael , Chtab Anna
Published: May 2008

By analogy with kinetic approach, the gas-solid turbulent flow was considered as an ensemble of interacting both stochastic liquid and solid particles. In this way, the motion equation for the solid particle along a smoothed trajectory has been derived. To close this equation, the statistical temperature of particles has been introduced and expressed by statistical properties of turbulence. The smoothed particles dynamics was then computed along with large-eddy simulation (LES) of turbulent channel gas flow with “two-way” coupling of momentum. The calculated results are compared with the experiment of Kulick et. al. (1994) and with computation of Yamomoto et. al. (2001), where the inter-particle interaction has been simulated by hard-sphere collisions with prescribed efficiency. It has been shown that our computation with smoothed motion of particle is relatively in agreement with experiment and computations of Yamomoto et. al. (2001). At the same time, the model presented in the paper has a following advantage: it, practically, does not require an additional CPU time to account for inter-particle interactions. The turbulence attenuation by particles and the preferential concentration of particles in the low-turbulence region have been shown.
Mechanical Engineering Program at the University of Guanajuato in Mexico
Authors: Hemmye Jerome H. , Aguilera Luz Antonio
Published: May 2008

Gold and Silver mining was begun in Mexico within fifty years of the Spanish conquest. The Mining Engineering and the Chemical Engineering needed to extract those valuable metals from the ore have been taught in Mexico from those early colonial days. To meet the colony’s needs for roads and structures, Civil Engineering followed as an academic discipline. Textiles and much later petroleum extraction and refining followed as important industries and they too were included in several Mexican university programs. The gradual industrialization of what is now Mexico brought with it a critical need for engineering education on a broader scale than was traditionally available. Less than forty years ago there was no Mechanical Engineering program in the State of Guanajuato, Mexico. The immediate needs of a Federal Oil Refinery and a Fossil Fuel Power Plant led to the establishment of a modest program utilizing practicing engineers as faculty, on loan part time, from the refinery. The evolution of the program from its earliest days is traced to the present program which includes a doctoral program which is rated among the top three public programs in Mexico.
Analysis and Optimization Design of Pressure Compensated Flow Control Valves
Authors: Wu Duqiang , Burton Richard , Schoenau Greg , Bitner Doug
Published: May 2008

A pressure compensated valve (PC valve) is a type of flow control device that is a combination of a control orifice and a compensator (often called a hydrostat). The compensator orifice modulates its opening to maintain a constant pressure drop across the control orifice. In other words, the PC valve is so designed that the flow rate through the valve is governed only by the opening of the control orifice and is independent of the total pressure drop across the valve. Because of the high non-linearities associated with this type of valve, it is impossible, in practice, to design such a valve where the flow rate is completely unaffected by the pressure drop across the valve. In this paper, the effect of the non-linerities on the performance of the PC valve is investigated. First, a generic non-liner model of a PC valve is developed. Using this model, all possible operating conditions can be determined. Then a linearized model is developed and used to analyze the dynamic behavior of the PC valve. The model can then be used to optimize the design and operation of the valve for specific applications.
Maglev 6-DOF Stage for Nanopositioning
Authors: Kim Wong-Jong , Verma Shobhit , Gu Jie
Published: May 2008

This paper presents a novel magnetically levitated (maglev) stage with nanoscale positioning capability in all six degrees of freedom (DOFs). The key aspect of this device is that its single moving part has no mechanical contact with its stationary base, which leads to no mechanical friction and stiction, and no wear particle generation. We present herein the mechanical design, instrumentation, and test results of this maglev stage. Currently it shows position resolution of 4 nm, position noise of 2 nm rms, hundreds-of-micrometer translational travel range, a-few-milliradian rotational travel range, and power consumption less than a fraction of a Watt per axis. This maglev stage can be used in numerous applications such as manufacture of nanoscale structures, assembly and packaging on micro-size parts, vibration isolation for delicate instrumentation, and telepresence microsurgery.
A Numerical and Experimental Analysis of Cardiovascular Stent Design Considerations
Authors: Charonko John J. , Ragab Saad A. , Vlachos Pavlos P.
Published: May 2008

Stents have proven very effective in opening the lumens of blocked and diseased arteries, leading to an increased quality of life for thousand of patients. Due to their success, stents have grown into a $1.5 billion dollar industry, but unfortunately still suffer from failure rates of 20–30% in the first year. Many of these failures can be traced back to restenosis or thrombosis of the stented arteries, a problem which conventional self-expanding or balloon-expanded stents have not proved effective in combating. Mathematical and experimental research shows that stents create adverse flow conditions and increase the stresses found around the implants, and trials of designs intended to reduce these effects have proven effective in combating restenosis. The goal of this research was to investigate mathematically design considerations for an improved stent that can reduce these negative effects. This was accomplished through the construction of a onedimensional numerical model for the fluid mechanics of the artery that was implemented using FEA and a combination of WENO and Runge-Kutta methods. The output from this model was compared with solutions from the literature and with in-vitro experimental results. Based on these tests it was concluded that the model accurately predicted the behavior of the pressure waves in a vessel. These numerical models were then used to evaluate several proposed designs. The pressure wave reflection was found to be controlled entirely by the design of the stent ends; mid-length variations in stent compliance provided no change in the model behavior. Also, a region of gradual transition between the low stiffness of the artery and the increased stiffness of the stent, while useful for reducing wall stresses, proved ineffective in reducing the magnitude of the reflected pressure waves. The best design for minimizing pressure wave reflection was found to be one that minimized total stent length.
Development of a Process to Generate 3D CAD Models for Re-Engineering of Components for Aging Systems
Authors: Siddique Zahed , Ochs Robert
Published: May 2008

Many systems are designed for useful life that go beyond decades. In most cases, especially when they are expensive, these systems need maintenance. Maintenance of aging systems, that are more than a decade old, requires improvement and/or replacement of components. In most instances new technologies became available, after original design and development, that can be applied to improve the existing aging components and sub-systems. Re-engineering of existing components is usually initiated from existing components. In many instances data packages, which include geometrical and manufacturing information, for these components are not available or incomplete. For mechanical systems, CAD tools provide flexibility and tools that can be used to perform analysis on components to measure performance before they are manufactured. Generation of parametric CAD models is essential to perform analysis and specify manufacturing processes for these components. Reverse engineering process can be used to develop surface and solid models of components from scanned point data for re-engineering. In this paper a general process to generate appropriate CAD models using reverse engineering for re-engineering applications is presented. A B-52 power pot tube is used as an example to demonstrate the steps, tools and techniques involved in development of models for re-engineering to generate surface and parametric solid models from point cloud data.
Wear Measurement of a Large Hydraulic Fluid Power Pump Using Radioactive Tracer Wear Technology
Authors: Treuhaft Martin B. , Timmons Suzanne A. , Eberle Douglas C. , Wendel Glenn R.
Published: May 2008

Real-time wear measurement is possible in fluid lubricated components utilizing radioactive tracer technology (RATT). This technology has been applied to internal combustion engines since the 1950’s, but has only recently been applied to hydraulic components. This paper presents the application of radioactive tracer technology to measure wear rate of pistons and slippers in a large variable displacement, high pressure, axial piston pump under various operating conditions. To apply this technology, new piston and slipper assemblies were exposed to thermal neutrons in a nuclear reactor to produce characteristic radionuclides (isotopes) in the slippers and pistons. These isotopes act as tracers, which when worn off in an operating pump can be measured by monitoring the gamma-ray activity in the circulating fluid. The accumlation of wear particles in the unfiltered circulation loop is monitored continuously as the pump is operated under various transient and steady state conditions. The steady state wear rate is determined by the rate of accumulation of radioactive wear particles in the loop over a period of time, usually less than a few hours. This first time application of RATT for wear analysis in a large hydraulic pump has shown positive results. This technology can be applied to determine wear sensitivity of hydraulic pump parts for an endless array of factors, such as speed, pressure, displacement, temperature, contamination level and composition, and duty cycle. Break-in, start-up, and transient wear affects can also be observed. Comparisons can also be made between the wear of different design features and materials.
Preliminary Investigations of a High Temperature Cu-13.3%Al-4%Ni Shape Memory Alloy Single Crystal
Authors: Trigwell Steve , Kumara K. Ganesh , Bhattacharyya Abhijit , Qidwai Muhammed A.
Published: May 2008

Preliminary investigations on the constitutive response of a Cu-13.3%Al-4%Ni (wt%) shape memory alloy single crystal with stress-free transformation temperatures around 100 to 150°C are reported. Room temperature stress cycling tests were carried out at very low deformation rates. Reproducible stress/strain curves of up to 9% strain due to detwinning (martensitematensite phase transformations) with no plastic deformation were obtained. The data also indicated that a period of stress cycling is required to stabilize the material before reproducible stress-strain curves are obtained due to martensite reorientation.
Thermal Management in Laser Assisted Machining: A Preliminary Study
Authors: Jen Tien-Chien , Jadhav Rajendra , Chen Yau-Min , Omari Samih
Published: May 2008

The use of laser in manufacturing has gained considerable attention recently. In non-reactive processes, the laser beam is used either to machine, to weld, or to modify the target material structure by local heating. In addition to elevating the surface temperature of the target, this local heating may significantly alter the material crystalline structure; change its phase, and thus the electrical, mechanical and thermal properties. For reliability and consistency, it is necessary to control effectively the laser-based manufacturing processes. Specifically, the induced micro-structural changes due to the heat transfer mechanisms have to be analyzed. Most importantly, the thermal effect on the sub-surface microstructures and the generated thermal stress distribution need to be well quantified. The application of lasers in manufacturing has distinctive advange when dealing with ceramic material. The use of advanced ceramics has doubled in the past ten years, and is expected to grow at an even faster pace in the new millennium. The superior properties, such as low weight, high temperature strength and wear/corrosion resistance, of these structural ceramics make them the preferred materials in various applications including bearings, rollers/followers, valves, engines, cutting tools and even artificial joints in the human body. The major goal of this study is to develop an innovative laser-assisted drilling process through innovative tool design and cooling method. A preliminary investigation of the effect of donut-shaped laser heat input on the temperature distribution in the workpiece is studied numerically and experimentally.
Thermomechanical Characterization of SMA Actuators Under Cyclic Loading
Authors: Lagoudas Dimitris C. , Entchev Pavlin B. , Kumar Parikshith K.
Published: May 2008

Shape memory alloy (SMA) wire actuators have been increasingly used in various devices and applications due to their high energy density and simple design. With the use of these actuators the questions of size effects on their behavior need to be addressed. This paper presents a study on the cyclic loading behavior of large diameter SMA wires subjected to different thermo-mechanical loading paths. Wires of two different diameters are investigated in the current study—1.78 mm and 2.16 mm. The issues addressed in this work include the investigation and design of a gripping technique for the large diameter wires to avoid slippage and study of heat treatment conditions for optimized superelastic behavior. After the heat treatment, specimens are subjected to cyclic mechanical loading. Two different cyclic loading patterns have been investigated: loading up to a given value of stress or up to a given value of strain.
A New Model for Biologic Constructs: Biotensegrity
Authors: Levin Stephen M.
Published: May 2008

Present biologic models envision organisms behave like the character ‘Topsy’ in Gone with the Wind; they “just grew.” Modeled of Lego©-like components, the individual structures are linked together as if they are automobile parts that are manufactured at different plants and assembled at some central factory. For the most part, hexahedral finite element meshes are used to model structures. When tetrahedral modeling is used, no account is made of the different mechanical properties that are inherent in triangulated structures, (trusses), that make the structures behave very differently than hexahedral-based models.
Manipulation of Particle Motions and Their Segregation in Micro-Fluidics by Positive Dielectrophoresis
Authors: Khusid Borus , Markarian Nikolai , Yeksel Mike , Farmer Kenneth R. , Acrivos Andreas
Published: May 2008

We study the ac-field-driven segregation of positively polarized particles flowing through a micro-channel. Our batch fabrication technique allows one to construct an apparatus featuring a large number of mechanically robust and chemically inert micro-devices having a very low ratio of the dielectrophoretic time to the fluid residence time. Experiments were performed on dilute suspensions in microfluidics with electrodes of different sizes arranged parallel and perpendicular to the flow. The application of a high-gradient strong ac field to a flowing suspension results in trapping particles in the channel. When the channel characteristics meet certain requirements, the predictions of a single-particle model for the particle accumulation along the channel are found to be consistent with the experimental data. The model calculations required no fitting parameters because the suspension properties were measured independently. The results of our studies validate a simulation model needed for the design and operation of dielectrophoretic micro-fluidics.
A Parameter Identification Method for Road Accidents Reconstruction
Authors: Mastinu G. , Gobbi M. , Mimini M.
Published: May 2008

The paper deals with the mathematical reconstruction of road accidents. Often, many of the relevant parameters for an accurate simulation are not known. The aim of the paper is to introduce and validate a new method to identify these (many) relevant parameters, such as exact impact location, tyre-road friction, ... The velocity of the two vehicles before the impact are computed by applying the principle of conservation of momentum and angular momentum and by estimating the kinetic energy losses. The identification process is based on a Global Approximation technique. Up to 17 numerical values pertaining to both running conditions before impact and parameters can be defined accurately and in a relatively short time. The definition of the 17 numerical values is made on the basis of the known data coming from the positions of the vehicles at rest and from tyre marks (if present and measured). The method has undergone a preliminary validation. Two case studies are presented which show the effectiveness of the identification method.
In Vivo Joint Kinematics in Normal and Anterior Cruciate Ligament Injured Knees: Results of a Cine Phase Contrast Dynamic MRI Study
Authors: Barrance Peter J. , Williams Glenn N. , Buchanan Thomas S.
Published: May 2008

Cine phase contrast MRI, combined with a model-based rigid body tracking technique, was used to measure kinematics during a knee extension exercise in both knees of 16 anterior cruciate ligament (ACL) deficient surgical candidates and 16 uninjured subjects. A statistically significant increase in anterior tibial translation was observed in the ACL-deficient knees. Evidence of disruption to the screw-home mechanism was observed in the ACL-injured knees, although this was not a statistically significant result.
Quadriceps Control: A Key Factor in Coping With Anterior Cruciate Ligament Deficiency
Authors: Williams Glenn N. , Barrance Peter J. , Snyder-Mackler Lynn , Buchanan Thomas S.
Published: May 2008

Approximately 250,000 anterior cruciate ligament (ACL) injuries occur in the United States each year. Most people cannot return to sports after an ACL injury without surgical intervention (Non-copers), but some can (Copers). Recent research suggests that the ability to cope with ACL injury is most likely related to neuromuscular function. The purpose of this study was to evaluate the neuromuscular control strategies of ACL deficient (ACL-D) Non-copers, ACL-D Copers, and people with uninjured knees using an established target-matching protocol, electromyography (EMG) of 10 muscles acting at the knee, and circular statistics methods. Thirty-two people (12 Non-Copers, 8 Copers, and 12 people without a history of knee injury) volunteered to participate in the study. The ACL-D subjects demonstrated diminished neuromuscular control when their muscle activity patterns were compared to those of the uninjured subjects. The key difference between the Copers and Non-copers was that Copers demonstrated better quadriceps control than the Non-copers. This study may have important implications for the treatment of people who sustain ACL injuries.