bluuebunny/crossref_metadata_2025 huggingface dataset:
Computerized Modeling and Simulation of Duplex Worm-Face Gear Drives Manufacturing Process
Authors: Napau Ioan , Napau Ileana D. , Napau Mircea , Maties Vistrian , Napau-Stoica Radu C. , Sudrijan Mihai
Published: April 2008

For mechanical transmissions, CAD systems provide flexibility and tools that can be used to perform analysis on components and to measure their performance even before they are manufactured. This paper represents an analytical study on a novel type of worm-face gear drive in which the worm is of duplex ZK-type. Such a gear set has two teeth flanks with different pitches, that facilitate stepless compensation of the tooth flank backlash or wear by means of the simple readjustment of the worm shaft. It can be used in applications that require an exact and even transmission of rotary movements or exact maintenance of a specific defined position, beside a high gear ratio in a compact space, high-load and shock capability, and reduced operating noise. The study was limited to mathematical modeling and numerical simulation of a gear set generation process using a novel 3D CAD simulation method. The method, suitable for the manufacturing process simulation of any type of gears provides a virtual 3D visual output with the ability to validate, within the precision limits of the CAD software, the accuracy of the calculation results. Some numerical examples showing 3D CAD teeth generation simulation of a duplex worm-face gear drive are presented. Numerical results relating to the analysis of virtually generated gear-set components are also provided in order to illustrate the developed theory.
Optical Fiber Sensor for Non-Contact Monitoring of ICSI-Pipettes
Authors: Ergenc Ali Fuat , Olgac Nejat
Published: April 2008

The injection of cells (e.g., sperm), subcellular organelles (e.g., nucleus), and solutes into cells (e.g., eggs) for cloning, embryology and molecular biology purposes are broadly practiced biological procedures. These cellular micro-injection operations are performed using drawn glass pipettes of microscopic diameters (as small as a few microns), which are extremely compliant structures. The pipette is pressed on the cell membrane causing a dimple until a predetermined tension is created. In the next phase, the membrane is pierced using various forcing techniques, and the pipette is driven into the cell. A non-contact sensor with high motion sensitivity is needed to monitor this delicate microscopic motion. We present an optical micro-device in this paper to achieve this objective. The main principle of the sensor is to detect the position and the orientation of a laser beam, which emanates from the pipette that is being monitored. We provide the technical specifications and the experimental verification of the concept.
Monitoring of FRP Strengthened Structures Using a Modified Time of Flight Interferometer
Authors: Jiang Guoliang , Van Vickle Patrick , Peters Kara
Published: April 2008

In this paper, we demonstrate a modified time of flight fiber optic sensor interferometer that provides global strain information for large-scale FRP strengthened structures with significantly increased strain sensitivity. With the originally continuous signals being reconstructed from the discretely sampled points using a sinc interpolation function, the sensing resolution of the interferometer is demonstrated to be significantly higher than through direct interrogation. To easily embed the FOS in structures and effectively increase the fiber sensing length, a commercially available prefabricated fiber ribbon is used. The results of bending tests of FRP beams with the embedded ribbon demonstrate the increase in strain sensitivity as well as no detectable loss in strength of the FRP plates due to the embedded fiber ribbons. Results from static loading test of a FRP strengthened beam with embedded fiber ribbons show the feasibility of this technique for self-monitoring FRP retrofits.
Senior Project: Soloflex Machine Resistance Curve Calculations
Authors: Hubbard Boyd , Janna William S.
Published: April 2008

A senior interested in body building completed a project involving the analysis of a Soloflex machine. The objective of the project was to involve the senior in a research project, and to determine the resistance curve for a bench press exercise using a Soloflex Exercise machine. In completing this project, the student obtained dimensions of the components of the machine, and made appropriate calculations to determine the resistance curve. To perform an exercise, the barbell arm is attached with a pin to the loading piece. Weight straps of equal rating are placed on both sides of the load and barbell arm pins. Pushing upward on the barbell arm will stretch the weight straps which provides resistance to the motion of the barbell arm. The straps were stretched with a Tinius-Olsen machine to determine the force vs. deflection behavior for one pair each of 2.5 lbf, 5 lbf, 10 lbf, 25 lbf, and 50 lbf weight straps. Once known, these data are then used to calculate the force required at the barbell arm to perform a bench press exercise for a particular resistance or "weight." Note that several different exercises can be performed with this machine due to its versatility, but the focus here is on a simple bench press, for which the resistance curve was determined. This study was completed by a senior at the University of Memphis. Data were obtained for a number of matched weight straps, but all data are not presented here. The essential components of a senior project from project planning to project management to project completion are described.
Size Effect on Adiabatic Gas-Liquid Two-Phase Flow Map and Void Fraction in Micro-Channels
Authors: Xiong Renqiang , Chung J. N.
Published: April 2008

Adiabatic gas-liquid two-phase flow patterns and void fractions in micro-channels were experimentally investigated. Using nitrogen gas and water, experiments were conducted in near-square micro-channels with hydraulic diameters of 0.209mm, 0.412mm and 0.622 mm, respectively. The main objective was focused on the effects of micro-scale channel sizes. Gas and liquid superficial velocities were varied from 0.06-72.3 m/s and 0.02-7.13 m/s, respectively. Four defined flow patterns including bubbly-slug flow, slug-ring flow, dispersed-churn flow and annular flow were observed in both micro-channels of 0.412 mm and, 0.622 mm in hydraulic diameter. In the micro-channel of 0.209 mm, the bubbly-slug flow turned into the slug-flow and the dispersed-churn flow was not observed. The current flow regime maps showed that the transition lines shifted towards higher gas superficial velocity due to the stronger surface tension effect as the channel size was reduced. The micro-channel flow regime maps were found to be quite different from those of mini-channels. Measured time-averaged void fractions in our micro-channels held a non-linear relationship with the homogeneous void fraction as oppose to the relatively linear trend for the mini-channels. A new correlation was proposed to predict the non-linear relationship that fits most of the experimental data of the current three micro-channels and those of the 0.1 mm diameter tube reported by Kawahara et al. within ± 15%.
Impact of Non-Newtonian Drops on Pharmaceutical Tablet Surfaces
Authors: Dechelette Alexis , Sojka Paul E. , Wassgren Carl R.
Published: April 2008

This study discusses the spreading of a non-Newtonian, power-law, film formed after a drop impinges on a flat surface (i.e., a pharmaceutical tablet). Non-Newtonian drop spreading is described by a model based on the one of Roisman et al. [2002]. The effects of variations in non-Newtonian liquid rheological parameters m (the consistency index) and n (the fluid behavior index) are shown to be significant. In either case, changes leading to a reduction in viscous forces result in enhanced spreading of the film, followed by more rapid recession. Both are expected. Of interest is the observation that an increase in consistency index can be compensated for by a reduction in flow behavior index since the sensitivity of film recession to a change in n is larger than that to variations in m.
Parametric Modeling of a Highly-Adjustable Race Damper
Authors: Emmons Shawn , Boggs Chris , Ahmadian Mehdi
Published: April 2008

As sanctioning bodies impose more restrictions on the number of days race teams are allowed to test, the successful use of component models and simulation becomes the division between a winning team, and all the rest. One of the main components race teams use to adjust the handling characteristics of their racecar is the damper. Damper adjustments allow the team to control body attitude, maximize the grip of the tires and fine-tune the car for driver feel. During track testing, teams make multiple damper adjustments based on the dampers they have characterized on their dynamometers back at the shop. To help expedite this process, a damper model is developed so a large range of adjustments can be quickly characterized without having to rebuild the damper and then run each adjustment on the dynamometer. This paper considers modeling of a highly-adjustable race damper made by Penske Racing Shocks for the NASCAR Nextel Cup Series. In addition to flow through piston bleed orifices, and valves in the piston, as considered in previous models, this model also considers flows through a head valve. With the completed model, a parametric study is conducted to investigate the effects of varying different damper parameters. The results of this study will show the effects various parameters have on the damper's output force. The final model will not only allow race teams to see the results of a damper adjustment, but will also aid in damper design and give an improved damper model for vehicle simulation.
Optical Properties of Nanocomposite Thin-Films
Authors: Garahan Anna , Pilon Laurent , Yin Juan , Saxena Indu
Published: April 2008

This paper aims at developing numerically validated models for predicting the through-plane effective index of refraction and absorption index of nanocomposite thin-films. First, models for the effective optical properties are derived from previously reported analysis applying the volume averaging theory (VAT) to the Maxwell's equations. The transmittance and reflectance of nanoporous thin-films are computed by solving the Maxwell's equations and the associated boundary conditions at all interfaces using finite element methods. The effective optical properties of the films are retrieved by minimizing the root mean square of the relative errors between the computed and theoretical transmittance and reflectance. Nanoporous thin-films made of SiO2 and TiO2 consisting of cylindrical nanopores and nanowires are investigated for different diameters and various porosities. Similarly, electromagnetic wave transport through dielectric medium with embedded metallic nanowires are simulated. Numerical results are compared with predictions from widely used effective property models including (1) Maxwell-Garnett Theory, (2) Bruggeman effective medium approximation, (3) parallel, (4) series, (5) Lorentz-Lorenz, and (6) VAT models. Very good agreement is found with the VAT model for both the effective index of refraction and absorption index. Finally, the effect of volume fraction on the effective complex index of refraction predicted by the VAT model is discussed. For certain values of wavelengths and volume fractions, the effective index of refraction or absorption index of the composite material can be smaller than that of both the continuous and dispersed phases. These results indicate guidelines for designing nanocomposite optical materials.
Trampoline Enclosure Safety Engineering Analysis
Authors: Brickman Dennis B.
Published: April 2008

An 18 month old boy died when he became entrapped in a gap formed between the bottom of a trampoline net safety enclosure and the top of the trampoline structure. Accident statistics survey, safety literature review, standards research, and alternative trampoline safety enclosure design evaluation are approaches utilized in the safety engineering analysis. The primary goal of this investigation is to make trampoline enclosure designers, retailers, customer service providers, and users more aware of the entrapment and strangulation dangers and to identify design alternatives to prevent similar injuries from occurring.
Assessment of Acoustical Measurement Methods and Standards on Rubber Asphalt Roads
Authors: Lee Huay Seen , Dai Liming , Sachakamol Punnamee
Published: April 2008

This paper focuses on the availability of reliable and widely recognized standards for measuring the tyre/pavement noise by determining the existence for a common or certified standard for measuring the asphalt rubber road noise and the possibilities of establishing a common standard or making enhancement to the current standard for accurately measuring the noise. A noise measurement study is conducted using one of many methodologies recognized internationally on both conventional and asphalt rubber road. The noise measurement study is based on the Statistical Pass-by method which is described in detail in the International Standards Organization ISO 11819-1. Certain modifications have been made in order to suit the local environmental condition during the measurement. The most significant modification from the ISO 11819-1 is the distance of the microphone location that is used in the noise measurement from the center of the test road. The ISO 11819-1 stated the microphone position as 7.5m distance from the test road. However, in North America, 15m distance is commonly used. The proportions between noise source dimensions and microphone distance are affected in such a way as to reduce the potential difference between LAmax (maximum sound pressure level) and LAE (Single-event sound exposure level) [2]. Simulations can be done to find out the influence of the microphone distance to the accuracy and reliability of the test measurement readouts besides the advantages and the disadvantages on using both microphone distances from the test road. To further prove the reliability of the study, the results are then analyzed and compared to the predicted noise level using the Traffic Noise Model (TNM) developed by the Federal Highway Administration (FHWA). The FHWA's TNM that computes highway traffic noise is constructed based on the large amount of vehicle noise-emissions database and has been made comparisons to at least five other different model results or real noise measurement study to verify the accuracy of the model.
Noise Prediction Model Development for the Traffic Noise on Asphalt Rubber Roads
Authors: Sachakamol Punnamee , Dai Liming
Published: April 2008

Traffic noise prediction techniques are important tools for assessing the effects of noise mitigation. A number of noise prediction models are available for predicting noise levels at a receptor point. Traditionally, these noise predictions are limited to road side areas, where the effects of building and other infrastructure act as a barrier impediment to noise propagation are not considered. This paper describes the application of simulation and modeling of a simplified traffic noise prediction method based on the U.S. FWHA highway and existing traffic noise prediction models. The simplification has been achieved mainly by using the assumption that traffic flow speeds of various vehicle classes are correlated and similar in magnitude Also, an assumption is made that ground attenuation depends not only on the type of ground cover but also on a horizontal distance between the source and the receiver. Finally, the research intends to numerically evaluate the tire-pavement noise of the road with Asphalt Rubber (AR) pavement to minimize the traffic noise generated by the pavement. The application of simulation and modeling by packaged software will be introduced for utilizing the results, planning purposes and preliminary prediction of the traffic noise level on the AR pavement road section in Saskatchewan. This traffic noise prediction model will be simple to use by any end users, particularly environmental planners, acoustic engineers, and non-specialists.
Development of a Draft Heavy Vehicle Rear Underride Guard Specification
Authors: Atahan Ali O. , Bonin Guido , El-Gindy Moustafa , Allen James
Published: April 2008

This paper summarizes results of a large research program intended to develop a draft rear underride guard specification for heavy vehicles. Results of a series of laboratory and full-scale crash tests performed at the Transport Canada Research Center were used in the development of these specifications. A total of eleven full-scale crash tests was carried out to evaluate the effectiveness of different underride guards. The first ten of these tests were performed on a simulated trailer attached guard. Four different underride guard designs were used in these ten full-scale crash tests. Three different vehicle models traveling at 48, 56 and 65 km/h speeds were used to impact underride guards head on. Results of the first ten crash tests show that the currently used US FMVSS 223 standard is far from adequate in preventing the occurrance of rear underride. Based on findings obtained from these crash tests, an improved guard design was developed and tested using a 16-meter trailer. This final crash test verified the effectiveness of improved guard design in reducing the undesirable effects of rear underride crashes. Based on the results, a draft heavy vehicle rear underride guard specification was developed.
Real-Time Estimation of Engine Torque Using Speed Wheel Information
Authors: Franco J. , Franchek M. A. , Grigoriadis K. M.
Published: April 2008

Presented is a real-time steady state engine torque estimation algorithm executed in the spatial domain (crank angle domain) using speed wheel information. The torque estimation algorithm consists of a notch-filter and a steady state model which is identified using an orthogonal least squares estimation algorithm. The inputs to this model include the amplitude of the nth frequency component (n is the number of cylinders) of the crankshaft signature and average engine speed. Notch filters executed in the crank-angle domain are employed to extract the nth frequency component directly from the instantaneous engine speed signal. This approach is applied to a calibrated engine model for an in-line six cylinder diesel engine. A discussion of the results is also provided.
Solving Beam Deflection Problems Using the Traditional Approach to Solve Axial and Torsion Problems
Authors: Rencis Joseph J. , Grandin Hartley T.
Published: April 2008

This paper presents a new approach to solving beam deflection problems. The approach involves the direct application of derived force-deformation formulas, a procedure commonly used with axial and torsion bar problems. This direct application of derived force-deformation formulas, referred to by the authors as Method of Segments, is extended to beam deflection analysis in order to provide a solution procedure for beams that is consistent in philosophy and application with that presented in most mechanics of materials textbooks for axially loaded bars and torsionally loaded shafts. The beam force-deformation formulas, involving slope and displacement, are derived by double integration for a beam of uniform cross-section, material and distributed loading with end shear forces and couples. Application of the formulas is direct and requires no integration or continuity equations. Furthermore, by identifying segments of uniform geometry, material and distributed loading, this approach can easily be applied to beams of discontinuous geometry and material that supports both concentrated and distributed loading.
A New Mathematical Model of the Force in Pneumatic Tire-Snow Chain Systems
Authors: Botero Juan C. , Gobbi Massimiliano , Mastinu Giampiero
Published: April 2008

In this paper a new theoretical model to estimate the transmitted force in a snow-chain safety device is presented. Starting with a detailed analysis of the significant external forces acting on the system, the mathematical model is developed using some basic concepts of the contact mechanics theory. A MATLAB® code was developed in order to perform numerical simulations and experimental tests were carried out to validate the model. The results obtained show that for certain conditions of the driving surface and the tire's tread the force transmitted along the chain can be several times the longitudinal traction force applied to the tire itself. The importance of the interaction between the blocks on the tire and the chain segments is discussed. Some conclusions and recommendations are made in order to improve the design process of this kind of devices.
Orientational Distributions and Rheological Properties of a Non-Dilute Colloidal Dispersion Composed of Rodlike Particles With Magnetic Moment Normal to the Particle Axis
Authors: Sakuda Yasuhiro , Satoh Akira
Published: April 2008

We have considered a semi-dense dispersion composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis to investigate the rheological properties and particle orientational distribution in a simple shear flow as well as an external magnetic field. We have adopted the mean field approximation to take into account magnetic particle-particle interactions. The basic equation of the orientational distribution function has been derived from the balance of the torques and solved numerically. The results obtained here are summarized as follows. For a very strong magnetic field, the magnetic moment of the rodlike particle is strongly restricted in the field direction, so that the particle points to directions normal to the flow direction (and also to the magnetic field direction). This characteristic of the particle orientation distribution is also valid for the case of a strong particle-particle interaction, as in the strong magnetic field case. To the contrary, for a weak interaction between particles, the particle orientation distribution is governed by a shear flow as well as an applied magnetic field. When the magnetic particle-particle interaction is strong under circumstances of an applied magnetic field, the magnetic moment has a tendency to incline to the magnetic field direction more strongly. This leads to the characteristic that the viscosity decreases with decreasing the distance between particles, and this tendency becomes more significant for a stronger particle-particle interaction. These characteristics concerning the viscosity are quite different from those for a semi-dense dispersion composed of rodlike particles with a magnetic moment along the particle direction.
Velocity Field Measurements in a Near-Wall Flow of Drag Reducing Solution in Microchannel
Authors: Ogata Satoshi , Sakai Kohei , Kanda Kensuke , Yang Ming
Published: April 2008

The velocity profile of a dilute polymer solution and a surfactant solution near the wall surface in a microchannel was clarified using evanescent wave illumination and a particle tracking velocimetry system. Fluorescent particles with a diameter of 100 nm were used as tracer particles. The test fluids were polyethylene-oxide (Peo15) solution at 5 ppm, oleyl-bihydroxyethyl methyl ammonium chloride (Ethoquad O/12) solution at 200 ppm and distilled water. The results obtained for the velocity profiles for distilled water and surfactant solution were found to agree well with the two-dimensional Poiseuille velocity profile. On the other hand, the velocity profile of the dilute polymer solution decreases significantly compared with that of water within 200 nm of the wall surface. These data provide the first velocity profile measurements of a dilute polymer solution and a surfactant solution in the near-wall region.
Research on the Principle and Characteristic of Compound Switch-Mode Hydraulic Power Supply
Authors: Cao Jianwei , Gu Linyi , Wang Feng , Chen Ying
Published: April 2008

Switch-mode hydraulic power supply is a hydraulic pressure converting unit made of some distributed hydraulic components, which can boost or buck hydraulic pressure steplessly, with low power loss (about 20%) and continuous flow-rate[1][2]. There are two types of switch-mode hydraulic power supply. One is pressure boost type and the other is pressure buck type. For the pressure boost power supply, changing of the pressure is realized through instantaneous braking of the large inertia load in the hydraulic inductor. For the buck power supply, changing of the pressure is realized through pulse flow-rate and low-pressure hydraulic complement (see "Switch-mode Hydraulic Power Supply Theory", 2005 ASME, IMECE-FPST No.79019)[2]. Because the output pressure is determined by the load, pressure buck is still requisite in pressure boost power supply. At the same time the system is unstable and with low efficiency. To deal with the problem that the pressure boost type switch mode hydraulic power supply is unfit for the low pressure load, the principle and the structure of a compounded switch-mode hydraulic power supply are proposed in this paper. In the compounded switch-mode hydraulic power supply, a pressure buck power supply is cascaded after a pressure boost power supply. At the same time, the output hydraulic capacitor of the pressure buck power supply and the input hydraulic capacitor of the pressure boost power supply are removed, which leads to the direct connection of the hydraulic inductors of the two power supplies Because of the same working principles of the two power supplies, one of the hydraulic inductors can be removed. Pressure boost and pressure buck are realized through the synchronically control of the two high - speed switch valves using PWM signal. No matter the outer load determined pressure is higher or lower than the pump pressure, compounded switch-mode hydraulic power supply can provide the proper power (not flow rate) matching actuators' consumption through regulating the duty ratio of the control signal. Therefore the optimal energy -saving is realized. Experimental research shows that the compounded switch-mode hydraulic power supply can realize a continuous bucking and boosting pressure with different duty ratio and the whole efficiency is at least 80%.
Fatigue Property of Steel Q235 Based on Metal Magnetic Memory Testing
Authors: Xing Hai Yan , Zhang Jia Zhong , Zhao Zun Bao , Xu Min Qiang , Wang Ri Xin , Wu Da Bo
Published: April 2008

Fatigue damage is the most common kind of failure for metal materials. Traditional non-destructive testing (NDT) methods fail to predict early fatigue damage. Magnetic Metal Memory (MMM) Testing, a new NDT technology, has the potential of fatigue damage evaluation. This paper aims to investigate fatigue mechanical property of ferromagnetic material with the MMM method. Steel Q235 samples with different depth and breadth artificial crack are tested in rotary bending fatigue machinery. The MMM fatigue features are as follows: the tangent component Hp(x) of magnetic induction intensity is gradually increasing up to the peak value while the fatigue crack is initiating and growing; after that peak, Hp(x) is descending with the crack deepening. Furthermore, the features have been studied theoretically.
Refrigerant Subcooling Correlations for Different Expansion Devices for a Non-Intrusive Charge Indicator
Authors: Gao Z. , Mei V. C.
Published: April 2008

The most common problems affecting residential and light commercial heating, ventilation, and air-conditioning (HVAC) systems are slow refrigerant leaks. Equipment users are usually not aware of the problem until most of the refrigerant has escaped. A low-cost, non-intrusive refrigerant charge indicator has been developed, based on temperature measurements and correlations formed to interpret the measured temperatures. It can be used to provide real time warnings to the equipment users before the majority of refrigerant is escaped. It could be inexpensive and easy to incorporate into existing heat pumps and air conditioners. Extensive laboratory experimental work was performed on a 2-ton window air conditioner and on a 2.5 ton split heat pump system. It was found that the heat pump was not sensitive to slow refrigerant leak because of the long liquid line. Liquid subcooling was measured to determine the system charge status before a substantial amount of refrigerant was leaked. This study reports the finding of correlations formed for liquid subcooling for the orifice plate and thermal expansion valve used on the heat pump system for both heating and cooling mode operation.
On the Transiant Response of Convective Extended Surface Heat Transfer: A New Approach
Authors: Razelos P. , Michalakeas G.
Published: April 2008

This work is devoted to the study of the extended surfaces transient response. Although, the steady-state fin analysis has attracted considerable attention for a very long time, the interest in the transient response started in the last quarter of the past century. Several publications have appeared since, either analytical using the 1-D, conduction model, or experimental. Perusing the pertinent literature, however, we have observed that, in all previous published papers the authors treat the transient response of extended surfaces, or fins, like regular solids. However, fin endeavors rest on certain fundamental concepts, leading to some simplified assumptions, that we shall briefly discuss in the next section, which allows using the 1-D conduction model, and affect their steady-state operation. Therefore, the need for re-examining and revising the previously used methods becomes apparent. However, the authors are indebted to the pioneer workers on this topic that opened new avenues in the field of extended surface heat transfer. The aim of this work is to offer a different point of view to this problem, by introducing a new spatial coordinate system, and a new time scale. The solutions presented here, rest on the previously mentioned certain fundamental concepts developed recently. In the following we show step by step, how the existing pertinent equations and formulas of fins' transient response, are transformed to new simpler forms, expressed in terms of more appropriate dimensionless parameters, in accord with those appearing in recent publications. In the following, we confine to the analysis of constant thickness longitudinal and pin fins subject to specific1 boundary conditions. Each case is accompanied with an example that, for reasons of comparison are taken from the literature. We also discuss what is meant by "the time required for transient response to attain the steady-state condition."
An Experimental Study on Voids in Mixed Alloy Assemblies
Authors: Bruno Felix , Damodaran Purushothaman , Srihari Krishnaswami , Subbarayan Guhan
Published: April 2008

The electronics manufacturing industry is gradually migrating towards to a lead-free environment. During this transition, there will be a period where lead-free materials will need to coexist with those containing lead on the same assembly. The use of tin-lead solder with lead-free parts and lead-free solder with components containing lead can hardly be avoided. If it can be shown that lead-free Ball Grid Arrays (BGAs) can be successfully assembled with tin-lead solder while concurrently obtaining more than adequate solder joint reliability, then the Original Equipment Manufacturers (OEMs) will accept lead-free components regardless of the attachment process or material used. Consequently, the Electronics Manufacturing Service (EMS) providers need not carry both the leaded and the unleaded version of a component. Solder voids are the holes and recesses that occur in the joints. Some say the presence of voids is expected to affect the mechanical properties of a joint and reduce strength, ductility, creep, and fatigue life. Some believe that it may slow down crack propagation by forcing a re-initiation of the crack. Consequently, it has the ability to stop a crack. The primary objective of this research effort is to develop a robust process for mixed alloy assemblies such that the occurrence of voids is minimized. Since there is no recipe currently available for mixed alloy assemblies, this research will study and 'optimize' each assembly process step. The difference between the melting points of lead-free (217°C) and tin-lead (183°C) solder alloys is the most important constraint in a mixed alloy assembly. The effect of voids on solder joint reliability in tin-lead assembly is well documented. However, its effect on lead-free and mixed alloy assemblies has not received due attention. The secondary objective of this endeavor is to determine the percentage of voids observed in mixed alloy assemblies and compare the results to both tin-lead and lead-free assemblies. The effect of surface finish, solder volume, reflow profile parameters, and component pitch on the formation of voids is studied across different assemblies. A designed experiments approach is followed to develop a robust process window for mixed alloy assemblies. Reliability studies are also conducted to understand the effect of voids on solder joint failures when subjected to accelerated testing conditions.
Assessment of Flow Boiling Heat Transfer Correlations for Application to Mini-Channels
Authors: Olayiwola Nurudeen O. , Ghiaasiaan S. Mostafa
Published: April 2008

Cooling systems that consist of mini-channels (channels with hydraulic diameters in the 0.5 mm to 2.0 mm range) and micro-channels (channels with hydraulic diameters in the 100 μm-500 μm range) can dispose of large volumetric thermal loads that are well beyond the feasible range of conventional cooling methods. Mini/micro-channel systems that utilize boiling fluids are particularly useful due to the superiority of boiling heat transfer mode over single-phase flow convention. Flowing boiling in mini and micro channels has been investigated experimentally by several research groups recently, and a number of empirical correlations have been developed, usually based on only a single set of experimental data. In this study, the capability of a number of widely used forced flow boiling correlations for application to mini channels is examined by comparing their predictions with experimental data from three separate sources. The tested correlations include well-established methods for conventional boiling systems, as well as correlations recently proposed for mini-channels. The experimental data all represent mini-channels. Based on these comparisons, the most accurate existing predictive methods for the tested mini-channel boiling data are identified.
Development of a Novel Electro-Hydraulic Laboratory
Authors: Fenstermacher David G. , Krishnamurthy K. , Landers Robert G. , Patel Jigar D.
Published: April 2008

This paper describes an Electro-Hydraulics Laboratory (EH Lab) at the University of Missouri - Rolla (UMR), which was recently established with a gift from Caterpillar Inc. The goal of this laboratory is to provide students the opportunity for hands-on experience with signal processing, dynamic modeling, and real-time control of industrial-grade electro-hydraulic systems. Unlike most comparable educational laboratories, nearly all of the components used in this laboratory were originally intended for industrial use, yielding a much more real-world experience for students. The laboratory utilizes the xPC Target software for rapid prototyping and execution of real-time data acquisition and control systems using Simulink. Several laboratories, as well as a course project, that utilize the EH Lab are presented.
Progressive Damage of Solder Joints: Modeling, Implementation and Verification
Authors: Qian Zhengfang
Published: April 2008

This paper presents a damage mechanics-based methodology for the progressive damage and virtual qualification of advanced electronic packages such as BGAs, DCAs, CSPs, and Flip-chips. The key technique is to implement the material nonlinearity into commercially available software tools. A unified viscoplastic constitutive framework with the damage evolution and failure criteria has been successfully implemented into the ABAQUS® code to model time-rate-temperature dependent material properties. The framework has been successfully applied to solder alloys, polymer films, and underfill encapsulants. The mathematical structure and numerical algorithm development of the unified constitutive framework as well as the key implementation techniques for commercial FEA codes have been summarized in this paper. Both crack initiation and propagation of a solder joint with damage evolution under mechanical cyclic loading have been demonstrated. Virtual simulations of TSOP component failure under mechanical cyclic loading and BGA package under thermal cyclic loading have also been presented.
Impact Properties of Syntactic Foams and Effect of Microballoon Wall Thickness
Authors: Lin Tien-Chih , Gupta Nikhil
Published: April 2008

Hollow particle (microballoon) filled polymeric composites, called syntactic foams, are tested for impact properties in the present work. Izod type pendulum impact testing is carried out on eight types of foams, which are made of four types of microballoons used in volume fractions of 0.5 and 0.6. Variation in the volume fraction of microballoons leads to a difference in the total energy absorbed during fracture of different types of foams. Results show that syntactic foams containing microballoons of lower density show lower impact strength because of the lower strength of these microballoons. An increase in microballoon volume fraction leads to decreased energy absorption and strength.
Detailed Electrochemistry and Gas Transport in a SOFC Anode Using the Lattice Boltzmann Method
Authors: Grew Kyle N. , Joshi Abhijit S. , Peracchio Aldo A. , Chiu Wilson K. S.
Published: April 2008

A coupled electrochemical reaction and diffusion model has been developed and verified for investigation of mass transport processes in Solid Oxide Fuel Cell (SOFC) anode triple-phase boundary (TPB) regions. The coupled model utilizes a two-dimensional (2D), multi-species Lattice Boltzmann Method (LBM) to model the diffusion process. The electrochemical model is coupled through localized flux boundary conditions and is a function of applied activation overpotential and the localized hydrogen and water mole fractions. This model is designed so that the effects of the anode microstructure within TPB regions can be examined in detail. Results are provided for the independent validation of the electrochemical and diffusion sub-models, as well as for the coupled model. An analysis on a single closed pore is completed and validated with a Fick's law solution. A competition between the electrochemical reaction rate and the rate of mass transfer is observed to be dependent on inlet hydrogen mole fraction. The developed model is presented such that future studies on SOFC anode microstructures can be completed.
An Experimental Investigation of Brake Squeal Suppression of Air Brake Systems for Electric Passenger Trains Using Oil Damper
Authors: Kanki Hiroshi , Adachi Kazuhiko , Takahashi Tadahiro , Nozaki Nobuyo , Asano Yoshio
Published: April 2008

Recently, the brake noise reduction is one of the most important environmental issues for not only passengers both inside and outside train but also people who live close to railway stations. In this paper, a friction-induced self-excited oscillation and accompanying noise of a tread brake system are experimentally investigated by using a brake dynamometer. The squeal phenomenon occurs in the frequency range over 2000Hz by the test stand and generates high intensity noise up to 120dBA. In order to suppress brake squeal successfully, a simple oil damper attaching to the system is proposed. Since the proposed oil damper is a kind of Houde damper, damping augmentation capability is obtained in broadband of frequencies. The experimental brake test results demonstrate the brake squeal elimination capability of the proposed damper.
Experimental Investigatoin of Flow Fields in a Square Channel Roughened With Various Ribs on One Wall
Authors: Wang L. , Verbeek M. M. J. F. , Burgers S. S. , Sunde´n Bengt
Published: April 2008

The present work studies the separated flow in a square channel with ribs on one wall by using the PIV method. In this study, the spacing between ribs is kept constant and the heights of rib are varied in order to investigate the influence of the pitch-to-height ratio, P/e on the flow structures. Depending on the various pitch ratios, the enclosure between ribs can be regarded as closed or open cavity. Results are included for mean velocity, streamlines, skin-friction coefficient, anisotropy parameter, turbulent kinetic energy production and two-point correlation. It is found that the separated shear layer in the closed cavity has strong momentum exchange with the mainstream. By contrast, the fluid contained in the open cavity is self-sustained and the outside streamlines are almost parallel to the bottom wall. Moreover, for the open cavity, the velocity fluctuations become vigorous as the flow reattaches directly on the trailing edge.
Nonlinear Normal Modes for Multi-Degree-of-Freedom Nonlinear Vibration Isolation System
Authors: Yu Xiang , Zhu Shi-Jian , Liu Shu-Yong
Published: April 2008

Nonlinear vibration isolation system (VIS) plays an important role for improving the capability of hydroacoustic stealth of naval vessels. In engineering, Nonlinear VIS is generally a multi-degree-of-freedom system and its mathematical model is a set of coupled differential equations. Nonlinear normal mode (NNM) is an effective tool for decoupling and analyzing the dynamics of this coupled system. In this paper, taking the flexibility of the base into consideration, the equations of motion of an on-board VIS with quadric and cubic nonlinearities is formulated. The NNMs of this multi-degree-of-freedom nonlinear VIS are constructed by using the invariant manifold approach. The invariant surfaces of the NNMs and the decoupled oscillators are presented.
Study on the Computation Method of Bilinear System With Piecewise Damping
Authors: He Qiwei , Zhu Shijian , Lou Jingjun
Published: April 2008

An "inverse" integration method to solve the piecewise linear system numerically is discussed. A bilinear system with piecewise damping is calculated using this method and compared with the results using interpolation scheme and direct integration method. Taking the displacement and the contact force as integration variables, the "inverse" integration method can evaluate the critical time when the non-smoothness occurs more precisely than other direct integration method and interpolation scheme.
Proposal of a Load Sensing Two-Way Valve Model, Applying “Design of Experiments” Techniques to Simulations
Authors: Vacca Andrea
Published: April 2008

This paper defines an analytical model, based on results of simulations, for the description of the actual behaviour of a particular load sensing valve. The component considered for the analysis is typically applied in steering systems, with a load sensing control strategy, in presence of other actuators. Controlling the primary port flow rate is the valve's scope, the exceeding flow being discharged to the secondary port. A simple analytical model of the valve is commonly used in the industrial field and is useful for the understanding of its operation in a generic hydraulic system. However, experiments show that the actual behaviour is strongly influenced by the flow rate through the valve, and depends also on many geometrical parameters (i.e. shape of spool grooves, spool edges distance, etc.). The simple empirical model presented in this paper is defined considering only parameters primarily affecting the valve operation. As it often happens in searching for new models, the discovery of the most influencing factors presents several difficulties, because of their large number and, mainly, because it is difficult to consider all possible mutual interactions. Therefore, in this analysis, a stochastic-based method has been chosen, according to a technique known as "Design of Experiments" (DOE). In the first part of the paper, the author presents a screening analysis of the valve, under all the possible operating conditions. This procedure allows the identification of the most influencing parameters, for the development of the enhanced model of the valve. The configurations examined were chosen defining an optimal experimental plan, that allows an high significance of results with a restricted number of tests, through fractional factorial strategies. Further, this analysis gives a lot of useful information for the improvement of the valve design. In the remaining section of this paper, the author presents a correlative model of actual valve behaviour. This is generalized to a wide range of possible spool geometries, and is characterized by a simple formulation, accounting for only a few parameters, highlighted by the screening analysis. All results processed by DOE algorithms, implemented with MATLAB® scripts, are evaluated through simulations, instead of experiments. For this purpose, a previously developed AMESim® model of the valve (validated on the basis of laboratory tests) has been utilized.
Polymer Chain Alignment in Shape Memory Polymer
Authors: Beblo Richard , Weiland Lisa Mauck
Published: April 2008

Since their development, shape memory polymers, urethanes, styrenes, and the like, have been of increasing interest in advanced material and structure design. The following is an experimental investigation into the effect polymer chain alignment has on the mechanical properties of a particular styrene shape memory polymer, Veriflex®. Aligning the polymer chains results in several material anisotropies; giving rise to the possibility of controllable, directional shape memory and modulus behavior and a basis for a multitude of prospective design concepts.
Multi-Axial Homogenized Energy Model for Ferroelectric Materials
Authors: Oates William S. , Smith Ralph C.
Published: April 2008

A multi-axial homogenized energy model is developed to account for nonlinear and hysteretic ferroelectric constitutive behavior induced by multi-axial electric field loading. The modeling approach extends a one-dimensional multi-scale modeling framework developed for ferroic materials [1, 2]. A three-dimensional energy function is introduced at the mesoscopic length scale and subsequently approximated as piecewise polynomial approximations to improve computational efficiency. Multi-scale field relations are then developed by introducing a distribution of effective electric fields and coercive fields that govern the nucleation of localized domain switching in polycrystalline ferroelectric materials. The distribution of field relations is used to relate the localized domain switching processes to observed macroscopic behavior by utilizing a stochastic homogenization technique. It is demonstrated that a simplified stochastic distribution of effective fields and coercive fields is sufficient to predict multi-axial ferroelectric switching in ferroelectric ceramics. Examples are given to validate the model in comparison to multi-axial loading experiments given in the literature. The model reduction provides a simple and efficient multi-scale modeling approach that is important for developing reliable piezoelectric actuator systems as well as implementation in model-based control of two and three dimensional structures.