bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Electromagnetic Induction Systems for Powering “Smart” Actuation Systems
Authors: Ritchie Erin , Koo Jeong-Hoi
Published: April 2008

The primary goal of this project is to design and test of a novel electromagnetic induction (EMI) system that is capable of converting ambient vibration energy into valuable electric energy for use in powering "smart" actuation systems. The principle of the EMI system is based on the Faraday's Law of Induction: the magnitude of the electromotive force (emf) induced in a circuit is proportional to the rate of change of the magnetic flux that cuts across the circuit. The converted electric energy (i.e., emf) from the EMI system will power a semi-active damping control device called a Magnetorheological (MR) damper. The project has been separated into two phases: (1) Optimal design of EMIs, (2) Performance evaluation of MR-EMIs. To identify an "optimal" EMI configuration, several prototype EMIs were designed and constructed. The performance of each EMI was then experimentally evaluated using a spring-mass system. The effects of the number of turns, coil length, number of phases and type of phase connection of the EMIs were evaluated by comparing maximum output voltages. Analysis of the output voltages revealed that generally increases in the number of turns and the number of phases causes an increase in the output voltage while increases in length caused decreases in voltage. In the second phase of the project, a prototype was built that integrated the EMI systems with an existing MR damper, making an MR-EMI system. The dynamic performance of the MR-EMI was experimentally evaluated using a dynamic force frame and a load cell. The results revealed that the current EMI design generated a force equivalent to that produced by a 2 volt battery.
On Transverse Vibrations of Rotating Non-Uniform Beams
Authors: Caruntu Dumitru I.
Published: April 2008

Several evaluations of natural frequencies of rotating structural elements such as windmill rotors, aircraft propellers, space frames and turbine blades have been published. Lateral vibration of centrifugally tensioned uniform Euler-Bernoulli beam, and transverse deflections of a straight tapered symmetric beam attached to a rotating hub as model for bending vibration of blades in turbomachinery have been reported in the literature. This paper presents the factorization of the fourth-order linear differential equation of motion of bending vibrations of rotating nonuniform Euler-Bernoulli beams into a pair of second-order differential Sturm-Liouville equations. Two classes of such rotating beams are reported.
Flexure-Based Two Degree-of-Freedom Legs for Walking Microrobots
Authors: Mehta Ankur M. , Pister Kristofer S. J.
Published: April 2008

This work examines the design of legs for a walking microrobot. The parameterized force-displacement relationships of planar serpentine flexure-based two degree-of-freedom legs are analyzed. An analytical model based on Euler-Bernoulli beam theory is developed to explore the design space, and is subsequently refined to include contact between adjacent beams. This is used to determine a successful leg geometry given dimensional constraints and actuator limitations. Standard comb drive actuators that output 100 μN of force over a 15 μm bi-directional throw are shown able to drive a walking gait with three legs on a 1 cm2 silicon die microrobot. If the comb drive suspensions cannot withstand the generated reaction moments, an alternate pivot-based leg linkage is proposed.
Rubber-Assisted Hot Embossing for Structuring Thin Polymer Film Polymeric Films
Authors: Nagarajan Pratapkumar , Yao Donggang
Published: April 2008

Precision structured polymer thin films with microstructures comparable to or greater than the film thickness are highly desired in many applications. Such micro-patterned thin films, however, are difficult to fabricate using the standard hot embossing technology where both halves of the mold are made of hard materials. This study investigated a rubber-assisted embossing process for structuring thin polymer films. The advantages of the rubber backup instead of a hard support include but are not limited to 1) simplifying the embossing tool, 2) protecting the embossing master, 3) facilitating embossing pressure buildup, and 4) accommodating conformal forming of microscale shell patterns. Several design and process variables including rubber hardness, embossing temperature, embossing pressure and holding time were carefully studied. Thin polystyrene films in a thickness of 25 μm were accurately patterned with microgrooves of characteristic dimensions on the order of 100 μm.
The Vehicle Autopilot: Simultaneous Robust Control Through Parametric Adaptation
Authors: Hailu Haftay , Brennan Sean
Published: April 2008

This work considers the problem of robustly controlling systems that have an implicit parametric coupling, and specifically considers the problem of lateral control of passenger vehicles at highway speeds. Passenger vehicles collectively have a wide range in dynamic behaviors mainly due to the ranges in size between different models. However, as vehicle size increases, the length, mass and mass moments of inertia also increase in predictable relationships that strongly couple these parameters to each other. The proposed control technique exploits this inherent parametric coupling in order to design a single robust controller that can be easily adapted parametrically from vehicle to vehicle. Parameter decoupling in the design model is achieved in the control synthesis step using a dimensional transformation. The resulting design model presents a system representation suitable for robust control of a very wide range of passenger vehicles using only a dimensional rescaling. This method is distinguished from prior work in that the structure of parametric dependence is included in the controller synthesis. The resulting design is tested on a scaled vehicle test setup developed at Pennsylvania State University. Both simulation and experimental results have shown the effectiveness of the technique for the proposed application.
A Testbed for Attitude Control Using Cold Gas Thrusters
Authors: Brousseau Julien , Maynard Rachel , Singaraju Anil , Richter Hanz
Published: April 2008

A portable testbed is designed and built to demonstrate attitude control using cold gas thrusters. The main components are a high-pressure Nitrogen tank, solenoid valves, nozzles and a data acquisition and control interface. The device is small enough to be operated on a desktop, facilitating classroom demonstrations. The device can be commanded from a laptop computer having the necessary interfacing software. A rotary encoder provides angular position information for use in model generation and calibration or in feedback control evaluations. Only bang-bang, pulse-width modulation and similar control strategies are possible to be implemented in this system due to the on/off nature of thruster operation. The paper describes the design and construction of the platform, the procedures followed to estimate key dynamic parameters and includes a sample run using a time-fuel optimal control law based on a nominal double integrator plant.
Parametric Study of Circular Micro Flexure Hinge Design
Authors: Shrestha Sarin , Yee Raymond K.
Published: April 2008

Compliant mechanism is a monolithic device that utilizes flexible elements, instead of pins, to transform the input to a useful output position, and flexure hinge is an integral part of a compliant mechanism. Flexure hinge design is important because it provides a means for motion actuation in a mechanism. An ideal design of a flexure hinge for a displacement output mechanism is that it provides maximum displacement output with minimum input. The objective of this study is to establish a design guide based on stiffness, displacement, and stresses for a generalized circular micro flexure hinge model using finite element method. Parametric study of a circular flexure hinge was performed using ABAQUS finite element code. The finite element results were compared with relevant analytical model from literature. Micro flexure hinge finite element models with selected range of dimensions for study were evaluated, and the optimal dimensions for flexure hinge design for maximum output displacement and minimum stresses were identified. From this study, the following parameters were established as design guide for a circular micro flexure hinge. With the width (w) of a circular flexure from 300 to 500μm range, our recommended flexure hinge height (h) is twice of the width, and the flexure hinge thickness ratio (b/t) is about 10.
Steam Condensation in a Vertical Passive Condenser
Authors: Gao Haijing , Oh Seungmin , Revankar S. T.
Published: April 2008

A set of steam condensation experiments is conducted to evaluate the heat removal capacity of a vertical passive condenser. A condensing tube is submerged in a water pool where condensation heat is transferred by secondary boiling heat transfer. Condensation heat transfer coefficients (HTC) are obtained under various test conditions, such as different primary pressure (150 - 450 kPa), inlet steam flow rate (1 - 5 g/s), air mass fraction (0 - 20%) and tube size (26.6 mm and 52.5 mm ID). The effects of these parameters to condensation performance are evaluated in this paper. Experimental data are compared with code predictions from RELAP5 with 2 condensation models. The comparison result shows that an improved condensation model is needed in RELAP5.
Self-Powered Magnetorheological Dampers
Authors: Choi Young-Tai , Wereley Norman M.
Published: April 2008

This paper addresses the feasibility and effectiveness of a self-powered magnetorheological (MR) damper operated by the energy harvested from vibration and shock environment. For doing so, an energy-harvesting device is theoretically constructed and added to an MR damper. This energy-harvesting device consists of a stator, a permanent magnet and a spring, and works as an energy-harvesting dynamic vibration absorber (DVA). The dynamic equation for the self-powered MR damper is derived theoretically. In order to theoretically evaluate the vibration isolation capability of the self-powered MR damper, a single-degree-of-freedom engine mounting system using the MR damper is constructed. The governing equation of motion for the engine mounting system is theoretically derived. A parametric study is conducted to find the optimal stiffness of the energy-harvesting DVA for the engine mounting system. Under various excitation displacements and a shock load, the vibration isolation performance of the engine mounting system with the self-powered MR damper is theoretically evaluated in frequency and time domains.
Dynamic Modeling of Magnetostrictive Hydraulic Pump
Authors: Chaudhuri A. , Yoo J.-H. , Wereley N. M.
Published: April 2008

Recently, there has been substantial research on the development of a hybrid hydraulic pump driven by various smart materials. Piezo-hydraulic actuators have already been developed for potential use in smart rotor applications. However, at high actuation frequencies, piezo-stacks generate significant heat mainly due to the hysteresis losses that can deteriorate their performance and permanently damage the piezo material. In contrast, magnetostrictive materials are more robust than piezostacks, especially at high temperatures, while offering almost the same bandwidth and higher maximum induced strain when compared with piezoelectric stacks. Also, the magnetostrictive material usually has a particular frequency range where the hysteretic losses taking place are minimum and consequently the operation results in least heat generation. As a result, to operate the pump with higher flow rate with minimum heat generation and maximum efficiency, we need to know the system resonance. Moreover, the hybrid pump with smart material is mechanically more complex than a single rod actuator; consequently, it can have more than one resonant frequency depending on the number of degrees of freedom of the system. A hybrid pump using the magnetostrictive material Terfenol-D has been developed in our laboratory with hydraulic oil as the working fluid. Several key design parameters, which include output cylinder size, diaphragm thickness, reed valve thickness and tubing diameter, along with operational conditions, like input current and bias pressure within the fluid, have been varied to identify a set of optimum driving conditions. Tests at no-load have been carried out for unidirectional motion of the output piston. In this paper, we develop a dynamic model of the hydraulic hybrid actuator to show the basic operational principle and compare the simulated data with test results. The final target of this study is to find optimal operational frequency to get highest performance and also to predict the pump sizing for a desired output velocity and load lifting capability.
Development of a Prototype for Transfer of Drawing Annotations Into the ASME Y14.41 Standard
Authors: Conover Jonathan S. , Zeid Ibrahim
Published: April 2008

The ASME Y14.41-2003 standard for Digital Product Definition Data Practices provides for representation of design data as an entirely digital package. One central requirement of the standard is storage of all design content, especially annotations, directly in the 3D model. Companies maintaining a library of models and drawings in their chosen CAD system will benefit from being able to quickly and reliably transfer drawing annotations into 3D models. This paper describes the design and development of a prototype conversion tool that will be capable of automatically converting existing drawing annotations into ASME Y14.41-2003 compliant 3D model annotations. The paper covers the mathematical formulation used for transfer of annotations from the drawing to the 3D model and the abstract software development model for the base classes and conversion algorithm. The paper presents examples for how the conversion tool was implemented within a commercial CAD system.
Transmissibilities of Two-Degree-of-Freedom Systems for Semi-Active Vibration Control
Authors: Lam H. F. , Liao W. H.
Published: April 2008

Transmissibilities for two-degree-of-freedom (2DoF) passive systems have been extensively investigated in the past. However, for semi-active control systems, the transmissibilities are rarely analyzed. The expressions of non-dimensional transmissibilities for the semi-active control systems are not found. There are no closed-form transfer functions for general semi-active control systems. The control algorithms for semi-active systems need to be specified first. Therefore, three reference systems (skyhook, groundhook, and their hybrid) are proposed. These equivalent systems are the references for the semi-active control systems to achieve. In this paper, the 2DoF skyhook, groundhook and hybrid systems for semi-active control are studied. The displacement and acceleration transmissibilities of those three reference systems are formulated and analyzed. Their transmissibilities are also compared with the passive system. Each of reference systems is classified as Ideal and Non-Ideal systems. The differences between the Ideal and Non-Ideal systems are also discussed. The optimal systems and their corresponding parameters are identified.
Control Issues of Digital Clay: Massive Hydraulic Actuator Array for Man-Machine Communication
Authors: Zhu Haihong , Paul Brittyn , Book Wayne J.
Published: April 2008

Digital Clay is an NSF funded project for human machine communication through a tangible haptic surface actuated by fluid power. Digital Clay's hardware can be divided into three subsystems: massive actuator-sensor array, fluidic driving system, and control system. The main focus of this paper is on the control issues of the massive actuator array of Digital Clay. Categorized by the function of control algorithms, the control system can be further divided into three levels: cell control, surface control, and user application interface. Analysis and testing results of above introduced topics are provided based on a 5×5 actuator array prototype. Most of the topics discussed in this paper are widely applicable not just for this specific device.
Environmental Impact of Fuel Spills on Land
Authors: Badr O. , Marafi A. , Ben P.
Published: April 2008

This study considers the toxicity and flammability of emitted fuel vapor from un-ignited pools of spilled chemicals on land. It also estimates the thermal radiation levels emitted from such pools in case they catch fire. A software based on EPA dispersion models was utilized to estimate the size and location of the dangerous clouds. The 3D dangerous clouds were presented in downwind, crosswind, and vertical directions from the source of the spill. The growth and decay of the formed dangerous zones with time were also investigated. Among other input data required by the above-mentioned software, the transient evaporation rate from the spilled fuel pool and its area were determined by considering the equations of conservation of mass and energy. The study also considered the situation when the spill is followed by ignition causing a pool fire. In such a case, the main concern for impact assessment was the US EPA-specified limiting radiation levels to which humans or facilities can be exposed. Exposure to 5.1 kW/m2 for more than 30 seconds can cause 2nd degree burns while exposure to the wood charring radiation level of 12.6 kW/m2 for more than one minute can cause fatality for humans. To facilitate this analysis a fire model developed by the US Gas Research Institute was used to find out safe distances from which fire fighting personnel can work towards extinguishing the fire. The application of such techniqus to a case study of an instantaneous accidental spill from a typical mobile gasoline tanker supplying fuel to local petrol stations showed that the toxic and flammable zones may extend to downwind distances of 561m and 399m, respectively. For ignited pools, on the other hand, the dangerous zones corresponding to radiation levels of 5.1 and 12.6 kW/m2 were 199 and 120 meters, respectively. For the case study of gasoline spill from a typical storage tank in a refinery resulted in the possible formation of toxic clouds extending to about 40,000 m and 48 m in the downwind and vertical directions, respectively. The flammability zone, however, was restricted to the pool area only. For most cases considered, parametric studies were performed to investigate the effects of wind speed, atmospheric stability, and vertical height on the size of dangerous zones. An interface between the dynamic results of the dispersion software and the static data of the Doha Geographical Information System (GIS) allowed the immediate identification of the major landmarks affected by the considered accidents. This data would be of a great help in developing an emergency evacuation plan for such accidents.
Examples of Academic Support Systems to Improve Student Success
Authors: Karimi Amir
Published: April 2008

The University of Texas at San Antonio (UTSA) has implemented a number of academic support systems to address obstacles to student success and to improve student retention. This paper describes the student demographics at UTSA, provides tracking data on student enrollment and retention, and includes discussion of the underlying causes of student attrition. It will describe some of the programs that are implemented to improve student success. Data is provided to measure the level of success of some of the programs that have implemented for the student success.
Design Aspects and Simulations of a Modified Micro-Scale Electrophoretron
Authors: Elmajdoub Nada , Nikitopoulos Dimitris E. , Soper Steven A. , Murphy Michael C.
Published: April 2008

This paper presents theoretical analysis and numerical simulations of a modified micro-scale electrophoretron previously realized on the macro-scale by Choi et al. (2001)1 and adapted here for cycling reaction applications (e.g. PCR, LDR). A window of operation in the device's design parameter space is determined using simple analytical solutions for electrokinetic flow with induced pressure gradients. Numerical simulations, including the effect of bends, electrodes and surface property discontinuities as pertinent to a physical implementation of the device, verify the expected behavior in a rectangular channel loop. The numerical results are used to provide insights to flow phenomena influencing the operation of the device and the dispersion of charged species.
Economic Optimization of a Distributed Generation System for an Orifice Building
Authors: Douglas M. E. , Sahm Michael K. , Wepfer William J.
Published: April 2008

Methodologies have been developed to aid in selection of a candidate distributed generation system for use in meeting a building's electrical demand. The systems studied are comprised of a combination of microturbines and/or natural gas reciprocating engines. These systems could also be used as prime movers in a combined heat and power application. Economic optimizations have been performed in order to identify distributed generation/prime mover combinations and operating strategies that yield the lowest electrical generation cost. These optimizations take into account a finite set of operating scenarios and equipment combinations. In addition to the economic optimizations, a direct comparison of customer design considerations has been made, highlighting the advantages and disadvantages of both microturbines and reciprocating engines. In this study, the optimal system for a 9290 m2 (100,000 ft2) office building in New York City at today's natural gas prices was determined to be a combination of natural gas reciprocating engines and microturbines. This system yielded a 5% reduction in generation costs over other cases examined including all homogeneous composition systems. With an increase in natural gas prices, the optimal case changes to be comprised solely of natural gas reciprocating engines. It has been shown that many factors are important to selection of optimal equipment including the specific end use load profile, cost of fuel, and system operating strategy.
Sustainable and Market-Based Analyses of Cooking Technologies in Developing Countries
Authors: Johnson Nathan G. , Hallam Arne , Conway Stuart , Bryden Mark
Published: April 2008

Over two billion persons worldwide use biomass as their primary form of energy in household cooking. This creates significant adverse consequences to families in developing nations that use stoves made without technical advancements commonly used in the industrialized world. The often simple, ad-hoc stoves lead to harmful side effects including disease, pollution, injury, and deforestation. Further negative consequences arise in household economics when considering losses in labor, time spent gathering fuel, and high fuel costs relative to income. Because of this much research over the past 10-20 years has been conducted with developing better household cooking methods. Findings from these efforts produced more effective stoves to accommodate the needs of impoverished families. Many of these projects began with philanthropic interests and grants to aid the world's poor. However outside of lump-sum funds for materials and labor there is often be little available to sustain the technical or human resources needed for continued stove utilization. One method to approach sustainability involves a market-based approach to better insure continuation of the benefits of improved cookstoves. This paper provides an assessment of the benefits of advanced cooking devices to both consumers and producers. Further investigations demonstrate consumer and producer impediments in collaborating for mutual benefit. Through realization of the interests and constraints facing both sides, plausible processes can be drawn for holistic improvement of communities in relation to household cooking. This paper also provides various options for intervention and start-up as potential methods in creating sustainable markets for safe, cost-effective, and efficient stoves.
Experimental Characterization and Static Modeling of McKibben Actuators
Authors: Kothera Curt S. , Jangid Mamta , Sirohi Jayant , Wereley Norman M.
Published: April 2008

McKibben actuators are pneumatic actuators with very high force to weight ratio. Their ability to match the behavior of biological muscles better than many other actuators has motivated much research into characterization and modeling of these actuators. The purpose of this paper is to experimentally characterize the behavior of McKibben artificial muscles with basic geometric parameters and present a model that is able to predict the static behavior correctly in terms of blocked force and free displacement. A series of experiments aimed at understanding the static behavior of the actuators was conducted. The results for three different lengths (4, 6, 8 in), three diameters (1/8, 1/4, 3/8 in) and two wall thicknesses (1/32 and 1/16 in) at pressures ranging from 10 psi to 60 psi show the expected trends (for example, block force increasing with diameter) as predicted by models presented in the literature. However, these models do not accurately predict static behavior. Corrections to the Gaylord equation are explored in order to obtain a more accurate model. Consideration of elastic energy storage in the rubber tube has been shown to significantly improve the models. Apart from this, the effect of non-cylindrical tips and elastic energy storage in the braid are also considered. To increase model accuracy, another set of experiments was used to characterize the elasticity of the rubber tubes and fibers of the braid. The improved model is able to predict static behavior correctly. Incorporating, various corrections, a model is presented that is more accurate in predicting the static behavior. Finally, in order to possibly obtain larger force output from the McKibben actuators, a series of experiments were performed to study the impact of an applied pre-strain. The results presented show large increases in blocked force with pre-strain. For the largest diameter actuator of 6 inch length, the blocked force at 12% pre-strain is as high as 270 N, while the amplification is higher at lower pressures. The model is tested to predict the pre-strain characteristics. A number of factors are identified that may improve the model and incorporate dynamic behavior.
Glutamate Dynamics in the PFC-NAC Synapse
Authors: Mohan A. , Gall J. , Nair S. , Kalivas P.
Published: April 2008

A computational model of glutamate dynamics in the PFC-NAc syapse is developed. The mechanisms considered are release of glutamate into the synapse, diffusion of synaptic glutamate into the extracellular space, Glu added by cystine-glutamate exchanger, Glu removal via transporters, and binding to mGluR's. The model will be used to determine the relative impact of the different mechanisms on Glu homeostasis, by using information about Glu levels and ranges for the known parameters and kinetic constants. The model will then be integrated with a PFC cell firing model to investigate the effects of cocaine-induced cellular adaptations in the PFC-NAc glutamatergic pathway.
Results From a Novel Insert Design for High Strain-Rate Compression of a Bulk Metallic Glass
Authors: Sunny George P. , Prakash Vikas , Lewandowski John P.
Published: April 2008

Liquidmetal-1 (LM-1, Zr41.25Ti13.75Cu12.5Ni10Be22.5) is a bulk metallic glass that can be processed in large thicknesses (e.g. 10 mm) because of its low critical cooling rate (e.g. 1 K/s). Like other bulk metallic glasses, this material exhibits near theoretical strength and large elastic strains (~2%) under quasi-static loading conditions. In this work, the Split-Hopkinson Pressure Bar (SHPB) was employed to perform high strain-rate compression tests on annealed LM-1. An ultrahigh-speed camera was also employed to perform in-situ video of the deformation process of the experiments, and the macroscopic fracture behavior was examined after testing. In addition, a new insert design was developed to reduce the effects of stress concentrations on the specimen. SHPB testing, combined with in-situ video, was performed on as-cast LM-1 using this new experimental configuration to determine the failure modes. The results of these experiments are compared to previous results to understand better the effects of stress concentration on high strain-rate behavior of bulk metallic glass.
Mechanical Property Study of the Fiber-Matrix Interface in SiC/SiC Composites
Authors: Jones Eric L. , Yarmolenko Sergey , Pai Devdas , Sankar Jag
Published: April 2008

The fiber-matrix interface between ceramic fibers and ceramic matrix plays a major role in the fatigue properties and toughness of continuous fiber reinforced ceramic matrix composites (CMCs). Boron Nitride (BN) is a widely used fiber coating material that provides a weak bond between the fiber and matrix. A weak fiber-matrix interface increases the strength and toughness of the overall CMC. Single fiber push-out tests were performed to study interfacial shear strength as a main parameter defining fatigue properties and toughness of SiC/SiC composites. The fiber-matrix interfacial shear strength was studied in melt infiltrated Hi-Nicalon/BN(CVI)/SiC composites exposed to various temperature and loading conditions, similar to those that are used in actual applications. Hi-Nicalon fibers with diameters of 13-14.5 μm were pushed out from samples with thicknesses ranging from 125-280 μm using a spherical tip with a 1 μm radius and 90° conical shape. Interfacial shear strength was calculated from sliding load, fiber diameter and sample thickness. Due to significant scattering, 30 individual push tests in every sample were used to obtain the average interfacial shear strength. The virgin sample has a shear strength of 20 MPa which is higher than tensile tested samples (12 MPa). Annealing of a virgin specimen for 100 hours at 1000°C slightly increased shear strength up to 21.5 MPa while annealing at 1100°C and 1200°C led to significant increase of shear strength up to 29 and 39 MPa correspondingly. This effect is associated with BN degradation at temperatures >1000°C.
Dynamical Stress Distribution Analysis of a Non-Uniform Cross-Section Beam Under Moving Mass
Authors: Ahmadian M. T. , Esmailzadeh E. , Asgari M.
Published: April 2008

One of the engineers concern in designing bridges and structures under moving load is the uniformity of stress distribution. In this paper the analysis of a variable cross-section beam subjected to a moving concentrated force and mass is investigated. Finite element method with cubic Hermitian interpolation functions is used to model the structure based on Euler-Bernoulli beam and Wilson-Θ direct integration method is implemented to solve time dependent equations. Effects of cross-section area variation, boundary conditions, and moving mass inertia on the deflection, natural frequencies and longitudinal stresses of beam are investigated. Results indicates using a beam of parabolically varying thickness with constant mass can decrease maximum deflection and stresses along the beam while increasing natural frequencies of the beam. The effect of moving mass inertia of moving load is found to be significant at high velocity.
Underfill Assessments and Validations for Low-k FCBGA
Authors: Kao Nicholas , Lai Jeng Yuan , Jiang Jase , Wang Yu Po , Hsiao C. S.
Published: April 2008

With the trend of electronic consumer product toward more functionality, high performance and miniaturization, IC chip is required to deliver more I/Os signals and better electrical characteristics under same package form factor. Thus, Flip Chip BGA (FCBGA) package was developed to meet those requirements offering better electrical performance, more I/O pins accommodation and high transmission speed. For high-speed application, the low dielectric constant (low-k) material that can effectively reduce the signal delays is extensively used in IC chips. However, the low-k material possesses fragile mechanical property and high coefficient of thermal expansion (CTE) compared with silicon chip, which raises the reliability concerns of low-k material integrated into IC chip. The typical reliability failure modes are low-k layer delamination and bump crack under temperature loading during assembly and reliability test. Delamination is occurred in the interface between low-k dielectric layers and underfill material at chip corner. Bump crack is at Under Bump Metallization (UBM) corner. Thus, the adequate underfill material selection becomes very important for both solder bump and low-k chips [1]. This paper mainly characterized FCBGA underfill materials to guide the adequate candidates to prevent failures on low-k chip and solder bump. Firstly, test vehicle was a FCBGA package with heat spreader and was investigated the thermal stress by finite element models. In order to analyze localized low-k structures, sub-modeling technique is used for underfill characterizations. Then, the proper underfill candidates picked from modeling results were experimentally validated by reliability tests. Finally, various low-k FCBGA package structures were also studied with same finite element technique.
Risk Management Models for Flip-Chip Electronics in Extreme Environments
Authors: Lall Pradeep , Hariharan Ganesh , Tian Guoyun , Suhling Jeff , Strickland Mark , Blanche Jim
Published: April 2008

In this work, risk-management and decision-support models for reliability prediction of flip chip packages in harsh environments have been presented. The models presented in this paper provide decision guidance for smart selection of component packaging technologies and perturbing product designs for minimal risk insertion of new packaging technologies. In addition, qualitative parameter interaction effects, which are often ignored in closed-form modeling, have been incorporated in this work. Previous studies have focused on development of modeling tools at sub-scale or component level. The tools are often available only in an offline manner for decision support and risk assessment of advanced technology programs. There is need for a turn key approach, for making trade-offs between geometry and materials and quantitatively evaluating the impact on reliability. Multivariate linear regression and robust principal components regression methods were used for developing these models. The first approach uses the potentially important variables from stepwise regression, and the second approach uses the principal components obtained from the eigen-values and eigen-vectors, for model building. Principal-component models have been included because if their added ability in addressing multi-collinearity. The statistics models are based on accelerated test data in harsh environments, while failure mechanics models are based on damage mechanics and material constitutive behavior. Statistical models developed in the present work are based on failure data collected from the published literature and extensive accelerated test reliability database in harsh environments, collected by center of advanced vehicle electronics. Sensitivity relations for geometry, materials, and architectures based on statistical models, failure mechanics based closed form models and FEA models have been developed. Convergence of statistical, failure mechanics, and FEA based model sensitivities with experimental data has been demonstrated.
Chaos Control Using PID and Lead Compensator Based on Fuzzy Gain Scheduling Technique
Authors: Tafti Sayyed Rouhollah Jafari , Radparvar Yousha , Salarieh Hassan , Alasty Aria
Published: April 2008

In this paper, a new method for tracking a desired path in nonlinear chaotic systems is presented. This method is based on using fuzzy gain scheduling in designing PID controller and Lead compensator. Using two standard controllers, PID and Lead, instead of complicated and costly nonlinear controllers is the main advantage of the proposed control system. PID controller has a stabilizing role whereas Lead compensator improves the performance of the system to track the desired path properly. To determine the PID and Lead gains, the nonlinear system is linearized around some working points which are the points of the desired path in specified times, and the gains are designed for each linearized system. Using a Sugeno system as a fuzzy gain scheduler, PID and Lead gains are determined in each time and are applied to the control system to make the nonlinear system track the desired path. To verify the presented method, Duffing equation as a chaotic system is considered to be controlled to which the proposed procedure is applied. Simulation results show the effectiveness of fuzzy gain scheduling in making the nonlinear system track different desired paths more smoothly.
Sound Quality Design as an Issue of Interactive Context
Authors: Schulte-Fortkamp Brigitte
Published: April 2008

When sound quality has to be evaluated a number of difficulties arise. Although there are various attempts of evaluating it, there is no definitive approach which covers the diverse requirements with respect to subjective importance. Since the subjective evaluation will be influenced by different modifiers, the methods in question have to be adapted necessarily to the various objectives that are related to certain subjective as well as to physical, psycho-acoustic, and socio-acoustic variables. The evaluation of the perception of acoustic environments needs an interactive, integrating, transdisciplinary concept. What will to be discussed up front are contextual interdependencies, socio-acoustic, and psychological methods, the significance of the modifiers within the guided decision-making process as well as the importance of sensorial modifiers as they make up the foundation of the research process. In many studies focusing on sound quality the observation of context in general becomes an issue if the experimental setup or the instruction or even the respective stages of the experiment are regarded as contextual, i.e. sound evaluation or the evaluation of product-related sound quality always implies evaluation of lifestyles depending upon acceptance and therefore intimately related to the daily routine of the tested individual. evaluations of sounds are highly sensitive contextually, but at present there is no usage-oriented experimental instruction which sufficiently defines the contextual rapport within a given sound evaluation setup. the concept of sound quality evaluation needs to be broadened to integrate a subjective and psycho-social approach. a concept and procedure will be introduced for benchmarking and target sound development in context to appropriately evaluate the sound of the corporate identity introduction
In-Plane Stretching in MEMS Actuated Deformable Mirrors
Authors: Mallela Vineel , Zhe John , Quinn D. Dane
Published: April 2008

We consider the response of a continuously deformable mirror with discrete MEMS actuators. The mirror itself is described with a geometrically exact shell model incorporating both flexural and extensional strains, while the MEMS actuators are represented as discrete elements subject to a time-dependent voltage. A reduced-order model is developed through a Galerkin reduction and the resulting equations are subjected to the method of multiple scales. The response of the system is then analyzed to uncover the ability of the system follow desired mirror profiles.
Evolution of Lead Free Solder Material Behavior During Isothermal Aging
Authors: Ma Hongtao , Suhling Jeffrey C. , Lall Pradeep , Bozack Michael J.
Published: April 2008

Solder materials demonstrate evolving microstructure and mechanical behavior that changes significantly with environmental exposures such as isothermal aging and thermal cycling. These aging effects are greatly exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In the current study, mechanical measurements of thermal aging effects and material behavior evolution of lead free solders have been performed. Extreme care has been taken so that the fabricated solder uniaxial test specimens accurately reflect the solder materials present in actual lead free solder joints. A novel specimen preparation procedure has been developed where the solder uniaxial test specimens are formed in high precision rectangular cross-section glass tubes using a vacuum suction process. The tubes are then sent through a SMT reflow to re-melt the solder in the tubes and subject them to any desired temperature profile (i.e. same as actual solder joints). Using specimens fabricated with the developed procedure, isothermal aging effects and viscoplastic material behavior evolution have been characterized for 95.5Sn4.0Ag-0.5Cu (SAC405) and 96.5Sn-3.0Ag-0.5Cu (SAC305) lead free solders, which are commonly used as the solder ball alloy in lead free BGAs and other components. Analogous tests were performed with 63Sn-37Pb eutectic solder samples for comparison purposes. In our total experimental program, samples have been solidified with both reflowed and water quenching temperature profiles, and isothermal aging has been performed at room temperature (25 °C) and elevated temperatures (100 °C, 125 °C and 150 °C). In this paper, we have concentrated on reporting the results of the room temperature aging experiments. Variations of the temperature dependent mechanical properties (elastic modulus, yield stress, ultimate strength, creep compliance, etc.) were observed and modeled as a function of room temperature aging time. Microstructural changes during. room temperature aging have also been recorded for the solder alloys and correlated with the observed mechanical behavior changes.
Seal Lubrication of an Automotive Water Pump
Authors: Antonini Massimo , Faglia Rodolfo , Remino Carlo , Pedersoli Marco
Published: April 2008

A noisy mechanical seal is a grave problem, especially in water pumps designed for the automotive industry. The noisiness is often caused by dynamic instability (stick-slip behavior), which occurs when the seal lubrication changes from hydrodynamic to mixed. Starting from this hypothesis, the paper shows a theoretical model that describes the interaction between the seal disks. Therefore this model correlates the acoustic emission to the working conditions of the water pump.
Influence of the Type of Oxidant in the Combustion of Natural Gas Inside an Aluminum Melting Furnace
Authors: Nieckele Angela O. , Naccache Monica F. , Gomes Marcos S. P. , Menezes Rafael C.
Published: April 2008

The fuel used as energy source for aluminum melting is of extreme importance for a better performance of the process. However, the type of oxidant can also lead to better performance, leading to a greater preservation of the equipments. Air is more abundant and cheaper, however due to the presence of nitrogen, there is undesirable NOx formation. An alternative is to employ pure oxygen. Although it is more expensive, it can lead to a cleaner and much more efficient combustion process, by significantly altering the combustion aspects inside the furnace, such as the shape of the flame and the distribution of temperature and heat flux. In the present work, numerical simulations were carried out using the commercial package FLUENT, analyzing different cases with pure oxygen and air as the oxidant for the combustion of natural gas. The results showed the possible damages caused by the process if long or too intense and concentrated flames are present.
A Multiscale Model of Composite Failure Under Impact
Authors: Oskay Caglar , Fish Jacob
Published: April 2008

We present a new computationally efficient mesoscale model aimed at predicting the dominant characteristics of failure at the microstructural level. This method combines the multiple scale asymptotic expansion method with the generalized transformation field analysis (GTFA) to reduce the computational cost of the direct homogenization approach. A computational validation methodology was devised for the validation of the proposed mesoscale model against experimental data. The proposed validation methodology permits incorporation of various types of experiments to the validation process by employing an experiment simulator repository.
Integrated Reliability Solutions: A Software Tool for Mechanical Reliability of Electronic Components
Authors: Wang Yinyan , Zhang Chuntao , Wu Xiaohua , Song Guoshu , Qian Zhengfang
Published: April 2008

A software tool, "Integrated Reliability Solutions" (IRS) has been developed, based upon the methodologies that have been applied to solving mechanical reliability problems of electronic components. The tool provides a system approach to reliability modeling. This tool enables significant reductions in design cycle time, warranty costs, and time required for experimentation and accelerated life testing. It also enables robust design and optimized manufacturing processes, and the timely and accurate innovation, evaluation and validation of new technologies.
A Multivariable Coupling Design for Variable Structure Control Using Particle Swarm Optimization
Authors: Coelho Leandro dos Santos , Mariani Viviana Cocco
Published: April 2008

This paper presents a new discrete-time sliding-mode control design for multiple-input multi-output (MIMO) systems with tuning parameters by particle swarm optimization (PSO). PSO is a kind of evolutionary algorithm based on a population of individuals and motivated by the simulation of social behavior instead of the survival of the fittest individual. Several control algorithms are presented, two decoupling design and six new approaches of the coupling design of sliding-mode control without the necessity of calculate the process interactor matrix. SMC needs a design tool for parameter configuration and efficient practically to deal with multivariable processes. Simulations are carried out using both decoupling and coupling discrete-time SMC designs. Results shown that the new proposed approach for designing the discrete-time coupling SMC is a powerful tool and it performs better than the decoupling design, usually utilized in MIMO process. The simulations are assessed on a robotic manipulator of two degree-of-freedom (2-DOF), that constitute a MIMO nonlinear coupling dynamic system, with treatment of payload mass and link length variations. Simulation results show that the application of this control strategy effectively improve the trajectory tracking precision of position and velocity variables.
A Practical CAE-Driven Approach for Weight Optimization of an Existing Vehicle Body
Authors: Deb Anindya , Naravane Ajit , Chou Clifford C.
Published: April 2008

This paper deals with weight optimization of a current vehicle body without affecting its styling, natural frequencies and front crashworthiness performance. A CAE-driven approach is adopted using commercially available OptiStruct and LS-DYNA solvers. While an automated iterative approach is used for size- and topology-based weight optimization with natural frequencies as constraints, crashworthiness requirements are incorporated into the weight-optimized model using engineering insight. It is found that significant weight reduction of an existing vehicle platform can be achieved through a methodical and ingenious utilization of optimization and crash simulation tools as demonstrated in the present study.