bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustically Generated Micromachined Jet Arrays for Micropropulsion Applications
Authors: Mu¨ller Michael O. , Bernal Luis P. , Washabaugh Peter D. , Chou Tsung-Kuan A. , Kim Hanseup S. , Najafi Khalil
Published: June 2008

Theory, manufacturing and experimental results of acoustically generated micromachined jet arrays for micropropulsion applications are presented. A reduced order theoretical analysis is found to be an accurate performance predictor. Scaling laws derived from the theory suggest the performance benefits derived by reducing the geometric size of the resonators, specifically the application of MEMS technologies. A novel manufacturing method is employed to construct the devices, incorporating an electrostatically actuated membrane to drive the acoustic jets. Experimental results of the MEMS devices demonstrate a structurally sound design, and a performance commensurate with expectations.
3D Finite Element Analysis for the High Speed Machining of Hardened Steel
Authors: Ng Eu-gene , El-Wardany Tahany I. , Dumitrescu Mihaela , Elbestawi Mohamed A.
Published: June 2008

The objective of this research is to illustrate the importance of modeling the right/similar chip formation with experimental results. When machining ‘difficult to cut’ materials at high cutting speeds, segmented chips are usually formed. When modeling the cutting process, it is important to consider the type of chip formed, as this affects the stress field generated in the workpiece. The modeled chips have to be the same type as those obtained during experimental work. However very few published models were capable of modeling the 3D oblique cutting with segmented chip formation. This paper presents a finite element model that includes a user customized catastrophic slip criterion and crack propagation module to model segmented chip formation in orthogonal & oblique machining of hardened AISI 4340 steel (52±2 HRC). Predicted cutting forces and chip thickness for segmented chips were in close agreement with experimental data. The modeled plastic strain and temperature distribution/magnitude were very different for continuous and segmented chip formation.
Design and Testing of a Micro Bubble-Pumped Heat Pipe
Authors: Takahashi Koji , Yoshino Kouichiro , Ikuta Tatsuya , Nagayama Kunihito , Asano Tanemasa
Published: June 2008

Micro thermal management devices using bubble in microchannel are under development. The heat removal mechanism of this device consists of phase change and forced convection which occur simultaneously and harmonically. Bubble expension in horn-shaped microchannel gives directional purnping by low-energy consumption. Several kinds of chips are built and tested. The uncontrollable phenomena of bubbly flow in microchannels and the key factors for further improvement are discussed.
Tool Performance in High Speed Finish Milling of Ti6Al4V
Authors: Barnett-Ritcey D. , Elbestawi M. A.
Published: June 2008

High feed rates may be achieved when finish milling titanium (Ti6AI4V) alloy (300HB) at speeds of 152–305 m/min (500–1000sfm). Three tool materials (micro-grain C2 carbide, fine-grained C2 carbide, and a TiAIN coated carbide) were tested using liquid (flood and through-spindle coolant (TSC) at pressures of 2.07 MPa), pressurized air (69–689 kPa (10–100psi)), and dry (no coolant) coolant conditions to prolong tool life. Tool wear manifested itself in two distinct patterns, gradual flank wear or micro-chipping leading to gross fracture. Which of these will lead to tool failure, will depend largely on the ability of the coolant to cool the tool (retard flank wear) without inducing thermal shock. Typically, under pressurized air, speeds up to 267 m/min (875sfm) and chip loads of 0.057–0.114 mm (0.00225–0.0045") may be attained.
An AI-Based Model for Predicting Instananeous Cutting Force in End Milling
Authors: El-Mounayri Hazim , Tandon Vipul
Published: June 2008

An Artificial Neural Network (ANN) model is developed to accurately predict the instantaneous cutting forces in flat end milling. A unique frequency domain approach is presented and is seen to simulate instantaneous cutting forces reasonably well. A set of eight input variables is chosen to represent the machining conditions and frequency domain parameters of the cutting force signal are generated. Three input parameters are varied, namely Feed, Speed and Depth of Cut. Four output parameters are suggested as a sufficient set to adequately reproduce the instantaneous cutting forces. Exhaustive experimentation is conducted to collect data (consisting of Fx, Fy, and Fz) to train and validate the model.
Temporal Response of Porous Glass Electroosmotic Pumps
Authors: Yao Shuhuai , Zeng Shulin , Santiago Juan G.
Published: June 2008

Sintered glass electroosmotic pumps have been fabricated that provide maximum flow rates and pressure capacities exceeding 14 ml/min and 1.4 atm, respectively, at 150 V, with an active pumping volume of less than 2 cm3. These compact devices with no moving parts have the potential to impact a variety of applications including microelectronics cooling systems and bioanalytical applications. We present here a preliminary a study of the response of the pumps to changes in fluidic load, including their short-term transient performance. A 0.5 mM borate buffer (pH = 9.2) is used to stabilize pump performance, with nearly optimal flow rate capacity. The experiments are conducted for working electrolytes of varying ion concentration. These performance characteristics are critical to applications that aim to use feedback control of flow rate and pressure over varying conditions.
Two-Phase Flow Characterization of an Expandable Polystyrene Injector for Use in the Lost Foam Casting Process
Authors: Wall K. F. , Bhavnani S. H. , Overfelt R. A. , Sheldon D. S. , Williams K.
Published: June 2008

A significant portion of casting defects in the Lost Foam Casting process can be traced back to a lack of consistency in the Expandable Polystyrene (EPS) foam pattern. The present study focuses on determining the cause of EPS foam pattern irregularities through the characterization of the two-phase flow of an EPS bead injector. The process variables studied during this experiment include fill time, fill pressure, EPS bead canister pressure, and fill hose diameter. It was found that the air flow rate under vented EPS bead canister condition using a 1.9 cm (3/4 inch) diameter fill hose increases 33% from a 276 kPa (40 psig) fill pressure to a 552 kPa (80 psig) fill pressure, and the EPS bead mass per cycle for a three second fill time increased 28% from a 276 kPa fill pressure to a 552 kPa fill pressure. The average EPS bead mass per cycle for a pressurized canister and a 1.9 cm diameter fill hose increased 71% from 55.22 grams for a 28 kPa EPS bead canister pressure to 80.21 grams for a 83 kPa EPS bead canister pressure at a fill pressure of 276 kPa. It was also discovered that the air flow rate under pressurized EPS bead canister condition is not a strong function of fill pressure but instead strongly depends on EPS bead canister pressure. The EPS bead mass per cycle for a 1.27 cm diameter fill hose exhibited a lower EPS bead mass per cycle than that for a 1.9 cm diameter fill hose for both the vented and pressurized canister conditions; however, the air flow rates and tip pressures observed for a 1.27 cm (1/2 inch) diameter fill hose showed similar behavior to those for a 1.9 cm diameter fill hose.
X-Ray CT High Density Artifact Suppression in Cryosurgery
Authors: Chen Laigao , Liang Yun , Xu Lisa X. , Wei Jikun , Sandison George A.
Published: June 2008

X-ray CT provides imaging guidance for cryosurgery that allows 3D visualization of frozen and unfrozen tissue. Temperature in the tissue water-ice interface (0 to −10 °C) may be calibrated to Hounsfield units. However x-ray CT images and their thermal calibration can be compromised by the cryoprobes generating high-density streak artifacts. A new subtraction technique for suppression of these artifacts is proposed and tested in prostate cryosurgery simulations. By subtracting the profile without cryoprobes from the profile with cryoprobes and iceballs, we can get the combined profile of the cryoprobes and a low value background. A polynomial interpolation is performed to obtain the background profile, which is then added back to the original profile without probes. The resulting profile is then fed to a conventional filtered back-projection routine to reconstruct the probe-free image. Finally the cryoprobe pixels in the originally constructed image with probes are added back to the probe-free image to get the final artifact-suppressed image. The major advantage of this subtraction technique is that it can successfully suppress the high-density artifacts in bone abundant body regions. X-ray CT images of cryoprobe arrays in a homogeneous gelatin phantom and the pelvic region of an anthropomorphic Rando phantom containing a human skeleton were generated. After suppression, cryoprobe metal artifact streaks are reduced and visualization of the positions and dimensions of the cryoprobes are well preserved. In-vivo canine studies are planned to test this new suppression technique for cryosurgery use.
Examination of the Slip Boundary Condition by µ-PIV and Lattice Boltzmann Simulations
Authors: Tretheway Derek C. , Zhu Luoding , Petzold Linda , Meinhart Carl D.
Published: June 2008

This work examines the slip boundary condition by Lattice Boltzmann simulations, addresses the validity of the Navier’s hypothesis that the slip velocity is proportional to the shear rate and compares the Lattice Boltzmann simulations to the experimental results of Tretheway and Meinhart (Phys. of Fluids, 14, L9–L12). The numerical simulation models the boundary condition as the probability, P, of a particle to bounce-back relative to the probability of specular reflection, 1−P. For channel flow, the numerically calculated velocity profiles are consistent with the experimental profiles for both the no-slip and slip cases. No-slip is obtained for a probability of 100% bounce-back, while a probability of 0.03 is required to generate a slip length and slip velocity consistent with the experimental results of Tretheway and Meinhart for a hydrophobic surface. The simulations indicate that for microchannel flow the slip length is nearly constant along the channel walls, while the slip velocity varies with wall position as a results of variations in shear rate. Thus, the resulting velocity profile in a channel flow is more complex than a simple combination of the no-slip solution and slip velocity as is the case for flow between two infinite parallel plates.
Investigation of Material Deformation by the High-Speed Water Slugs
Authors: Petrenko O. , Geskin E. S. , Atanov G. A. , Goldenberg B. , Semko A.
Published: June 2008

Water constitutes an attractive manufacturing tool It is readily available and clean. The waterjets are conventionally used for surface cleaning, material removal, and surface modification. The intrinsic shortcomings of such an application are the need in the use of expensive and heavy pumping facilities and, what are more important, peculiarities of the waterjet-substrate interaction which limit material deformation by the incoming jet. These shortcomings are eliminated if the workpiece is impacted by the array of the water slugs, generated by the direct injection of high-intensity energy pulses into the water vessel (barrel) and ejection the portion of the water via the nozzle attached into the barrel. Such a device (barrel-nozzle combination) will constitute an effective and versatile manufacturing tool. Understanding of the phenomena that occur in the course of the energy injection into the water is necessary for the design of the desired device. The phenomena in question are determined by the ratio between the speed of the water in the barrel in the course of the energy injection and the speed of the shock waves in the water. If this ratio is much less than unity, the exit velocity is determined by the ratio between the cross section areas of the nozzle exit and the barrel. If the ratio in question approaches the unity, the water velocity at the nozzle exit is determined by the impact pressure. The device utilizing this principle is termed the water extruder. If however, the ratio is much more than unity the exit water velocity is determined by the superposition of shock waves developed in the fluid. This device termed the water cannon is able to accelerate the water slug to the speed far exceeding 1,000 m/sec. The numerical and experimental studies of water extruder were carried out. The numerical models were constructed and the variation of the water velocity and the water pressure in the barrel were investigated. Experimental setup for the study of the water extruder was constructed by the modification of Remington power tool. The experiments involved the piercing of metal strips. The effect of operational conditions on the maximal depth of the piecing was determined. Another series of experiments involved the study of the slug impact on plastic (lead) and brittle (concrete) materials. The effect of the stand off distance on the removal of both kinds of material was investigated. As the result the suggestions about the way of construction of the water extruders and their practical applications were made.
Comparison of Methods for Simulating Gas Forces on Moving Microbeams
Authors: Torczynski J. R. , Gallis M. A. , Piekos E. S.
Published: June 2008

The force produced by the surrounding gas on a moving cantilevered microbeam is analyzed using the Reynolds equation, the Navier-Stokes equations, and the Direct Simulation Monte Carlo (DSMC) method (i.e., molecular gas dynamics). It is found that the Reynolds equation underpredicts the damping coefficient compared to the Navier-Stokes equations, particularly when the gap width becomes comparable to the beam half-width. The accuracy of the Reynolds equation can be significantly improved for these conditions by modifying the pressure boundary condition applied at the edge of the beam (this modified boundary condition reverts to the original boundary condition as the gap width becomes much smaller than the beam half-width). Since continuum methods with slip boundary conditions are of uncertain accuracy for large slip velocities, DSMC simulations are performed to compare to Reynolds-equation results and Navier-Stokes simulations. The damping coefficients from DSMC simulations are generally somewhat lower than the corresponding Navier-Stokes values.
Measurements for Turbulent Channel Flow Containing Microbubbles Using PIV/LIF Technique
Authors: Nagaya Shigeki , Hishida Koichi , Kodama Yoshiaki , Kakugawa Akira
Published: June 2008

It is known that local skin friction can be reduced by injecting microbubbles into a trubulent boundary layer. However, so far the mechanism of the reduction has never been understood. In the present study, the objective is to understand the characteristics of a turbulent flow field containing microbubbles with an experimental approach in order that the mechanism for the skin friction reduction is clearly elucidated. In order to measure the flow with the microbubbles, a combination of PIV and LIF methods is developed. Measurements are carried out for a horizontal channel flow with microbubbles by which the skin friction is reduced. Modifications of the wall turbulence due to the injection of the microbubbles are discussed.
Scaled Room Three-Dimensional Velocity Measurements Using Particle Image Velocimetry
Authors: O’Halloran Steven P. , Beck B. Terry , Hosni Mohammad H. , Gielda Thomas P.
Published: June 2008

A stereoscopic particle image velocimetry (PIV) system was used to measure flow within a one-tenth-scale room. The dimensions of the scaled room were 732 × 488 × 274 mm (28.8 × 19.2 × 10.8 in.). The measurements were made under isothermal conditions and water was used as the fluid instead of air. Six equally spaced vertical planes along the length of the room were captured and symmetry was utilized so that measurements were only made on one side of the room. A sample size of 50 pairs of PIV images were collected and averaged to determine average velocity. Turbulent kinetic energy was also calculated from the collected data. The equipment configuration, measurement information and the velocity and turbulent kinetic energy results are presented in this paper. The measurements provide detailed three dimensional velocity profiles that could be used to validate numerical simulations.
Stack and Mechanical System Effects on Dispersion of Biological Agents in a Tall Building
Authors: Musser Amy , Kowalski Wladyslaw , Bahnfleth William
Published: June 2008

Multizone network airflow analysis is used to analyze stack and mechanical system effects on the distribution of three representative biological agents in a prototype 40 story building. This approach relies on mass balances to compute airflow and contaminant transfer between the building zones. The analysis considers stack effects caused by cold outdoor temperatures, unintended positive and negative pressurization of the floor on which the release of the agent occurs, and three levels of contaminant removal using a combination filter/UVGI system. The results show that vertical shafts, such as stairwells and elevator shafts provide significant routes for contaminant transfer between floors, even when these floors are served by different air handling systems. Because the air moving through these pathways does not pass through an air handling system, this type of transport is not as easily reduced by filtering. However, commercially available filters were able to reduce contaminant concentrations substantially in zones that receive contaminants primarily due to recirculation through the air handling system.
Heat Transfer of Solid Particulate and Gaseous Heat Carrier in an Airlift Apparatus
Authors: Sheyman Vladimir , Rathod Mulchand S.
Published: June 2008

This paper considers the heat transfer process between solid particulates with heat source and gaseous heat transfer carrier in airlift apparatus during the pneumatic transportation. This case has many important practical applications in heat transfer systems where heat is generated within or absorbed by the particulate. Examples of such processes include drying processes, chemically reacting systems, and combustion processes. The two most important parameters in the thermal treatment of solid particulates in this case are the temperatures of solids and the gaseous heat carriers. Traditionally, these temperatures are considered as functions of x-ordinate along the heat transfer duct of the apparatus. Such an approach leads to the subsequent difficulties because it is necessary to solve simultaneously the differential equations of particulates and gaseous heat transfer carrier motion and the equations of heat transfer. This paper considers a deviation from this traditional approach and presents a set of differential equations in which the parameter is a heat transfer surface of the particulates. This approach reduces the number of differential equations describing the process and significantly simplifies the analytical formulation of the problem and hence the solution itself. The provided solutions allow for determining the temperatures of both the solids and the gaseous heat carriers as a function of particulate heat transfer surface. Two specific cases addressed here are heat transfer and heat and mass transfer when heat is generated within or absorbed by the particulates.
Integrating Optimal Truss Design Methodologies Into Mechanical Engineering Technology
Authors: Szaroletta William K.
Published: June 2008

The author has previously shown that single criterion optimization methodologies can be effectively integrated into lower-division mechanical engineering technology courses using single beam elements and a variety of load cases. In that paper, multiple methodologies of varying beam cross-section to minimize weight of the beam or to approach a constant stress state in the beam were described and their use investigated. This paper describes the application of these single criterion optimization methodologies to multiple-part assemblies, specifically engineering trusses. Although the optimization methodologies are similar, they are all far more complex in multiple-part assemblies than in single beam element optimization problem. The truss optimization theory, analysis, and testing that were utilized in the classroom and laboratory will be discussed in this paper. The correlation between optimization results from both spreadsheet solver and finite element analysis (FEA) solutions is presented. Also, the subsequent correlation between the analysis results and the experimental verification from photoelastic studies of prototype trusses is presented.
Flow-Induced Vibration of Anisotropic Cylindrical Shells
Authors: Toorani M. H. , Lakis A. A.
Published: June 2008

This paper deals with the vibration analysis of anisotropic laminated cylindrical shells conveying fluid. We focus on the axi-symmetric (n=0) and lateral (beam-like, n=1) vibration modes of the anisotropic cylindrical shells. Particularly important in this study is to obtain the natural frequencies of the fluid-structure coupled system and also to estimate the critical flow velocity at which the structure loses its stability. The coupled equations between the shell and the fluid are derived from a refined shell theory by taking into account the shear deformation effects. The displacement functions are obtained from the exact solution of refined shell equations and therefore the mass and stiffness matrices of the shell are determined by precise analytical integration. The added mass, stiffness and damping matrices of the fluid are obtained by an analytical integration of the fluid pressure over the liquid element. Thereafter, these matrices are coupled with the dynamic equation of the empty shell. The natural frequencies obtained with the shell partially or completely filled with liquid are in good agreement with those obtained experimentally and from other theories. The stability of the shell subjected to a flowing fluid is also studied. The shell’s anisotropy is discussed.
Large-Amplitude Vibrations of Empty and Fluid-Filled Circular Cylindrical Shells With Imperfections: Theory and Experiments
Authors: Amabili M. , Pellegrini M. , Pellicano F.
Published: June 2008

The large-amplitude response of perfect and imperfect, simply supported circular cylindrical shells to harmonic excitation in the spectral neighbourhood of some of the lowest natural frequencies is investigated. Donnell’s nonlinear shallow-shell theory is used and the solution is obtained by Galerkin method. Several expansions involving 16 or more natural modes of the shell are used. The boundary conditions on the radial displacement (simply supported shell at both ends) and the continuity of circumferential displacement are exactly satisfied. The effect of internal quiescent, incompressible and inviscid fluid is investigated. The nonlinear equations of motion are studied by using a code based on arclength continuation method. A series of accurate experiments on forced vibrations of an empty and water-filled stainless-steel shell have been performed. Several modes have been intensively investigated for different vibration amplitudes. A closed loop control of the force excitation has been used. The actual geometry of the test shell has been measured and the geometric imperfections have been introduced in the theoretical model. Several interesting nonlinear phenomena have been experimentally observed and numerically reproduced, as: softening-type nonlinearity, different types of travelling wave response in the proximity of resonances and amplitude-modulated response. For all the modes investigated, the theoretical and experimental results are in strong agreement.
Numerical Simulations of Vortex-Induced Vibration of Flexible Cylinders
Authors: Yamamoto Cassio T. , Fregonesi Rodrigo A. , Meneghini Julio R. , Saltara Fabio , Ferrari Jose´ A.
Published: June 2008

The main purpose of this paper is to acquire a better understanding of the hydroelastic interactions, which take place between oscillating flexible cylinders and fluid forces. The cylinders are subjected to currents and shear flow, and the hydrodynamic forces are estimated by CFD tools. This article presents the results of an investigation being carried out at the University of Sa˜o Paulo, in which a discrete vortex method is used to simulate the flow around a flexible cylinder. The calculations are compared with results obtained employing the quasi-steady theory, as proposed by Ferrari [2]. Also, the calculations are compared with experiments of a cantilever flexible cylinder immersed in a current, see Fujarra [6]. The reduced velocity vs. non-dimensional amplitude curve obtained in our calculations is compared with the experimental results. Visualizations of the wake indicate a hybrid mode of vortex shedding along the span. A 2S mode is found in regions of low amplitudes, changing to a 2P mode in the regions of larger amplitudes. The position of the transition of the modes varies with the reduced velocity. Our intention is to apply this model to problems occurring in the offshore industry. In this industry fluids are conveyed from the seabed to the platform through slender structures called risers. These risers are subject to shear and oscillatory flows due to currents and waves, respectively, flows with a very high degree of complexity, with changes of intensity and direction the deeper the water depth. A finite element structural model based on the Euler-Bernoulli beam theory was developed. In order to evaluate the dynamic response, a general equation of motion is solved through a numerical integration scheme in the time domain. The hydrodynamic forces are evaluated in two-dimensional strips. The technique used is the Discrete Vortex Method, which is a Lagrangian numerical scheme to simulate an incompressible and viscous fluid flow. A practical case of marine risers is also presented. In this case the results for various uniform currents acting on a single, flexible cylinder, representing a riser of 120m with 100m under water, are shown. Envelopes of maximum and minimum in-line and transverse displacements are presented. There is also a comparison of a shear flow case between the CFD numerical code with the quasi-steady theory code developed by Ferrari [2].
Numerical Modelling of the Three-Dimensional Slamming Problem
Authors: Tourbier Matthieu , Peseux Bernard , Donguy Bundi , Gornet Laurent
Published: June 2008

This paper deals with the slamming phenomenon for deformable structures. In a first part, a three-dimensional hydrodynamic problem is solved numerically with the Finite Element Method. The results for a rigid body are successfully compared to the analytical solutions. After the numerical analysis, an experimental investigation is presented. It consists in series of free fall drop-tests of rigid, deformable cones shaped models with different deadrise angle and thickness. Distribution of the pressure and its evolution are analyzed. Numerical and experimental results are compared and present good agreement.
Computation of a Propagating Interface in Multiphase Flows Using an Adaptive Coupled Level Set Method
Authors: Liang Ruquan , Komori Satoru
Published: June 2008

We present a numerical strategy for a propagating interface in multiphase flows using a level set method combined with a local mesh adaptative technique. We use the level set method to move the propagating interface in multiphase flows. We also use the local mesh adaptative technique to increase the grid resolution at regions near the propagating interface and additionally at the regions near points of high curvature with a minimum of additional expense. For illustration, we apply the adaptive coupled level set method to a collection of bubbles moving under passive transport. Good agreement has been obtained in the comparision of the numerical results for the collection of bubbles using an adaptative grid with those using a single grid. We also apply the adaptive coupled level set method to a droplet falling on a step where it is important to accurately model the effect of surface tension force and the motion of the free-surface, and the numerical results agree very closely with available data.
Crashworthiness Performance of Mass-Efficient Extruded Structures
Authors: Mayer Robert R. , Chen Weigang , Sachdev Anil
Published: June 2008

Theoretical, numerical and experimental studies were conducted on the axial crushing behavior of traditional single-cell and innovative four-cell extrusions. Two commercial aluminum alloys, 6061 and 6063, both with two tempers (T4 and T6), were considered in the study. Testing coupons taken from the extrusions assessed the nonlinear material properties. A theoretical solution was available for the one-cell design, and was developed for the mean crushing force of the four-cell section. Numerical simulations were carried out using the explicit finite element code LS-DYNA. The aluminum alloy 6063T4 was found to absorb less energy than 6061T4, for both the one-cell and four-cell configurations. Both 6061 and 6063 in the T6 temper were found to have significant fracture in the experimental testing. Theoretical analysis and numerical simulations predicted a greater number of folds for the four-cell design, as compared to the one-cell design, and this was confirmed in the experiments. The theoretical improvement in energy absorption of 57% for the four-cell in comparison with the one-cell design was confirmed by experiment. The good agreement between the theoretical, numerical and experimental results allows confidence in the application of the theoretical and numerical tools for both single-cell and innovative four-cell extrusions. It was also demonstrated that these materials have very little dynamic strain rate effect.
Rails Deformation Pattern in Frontal Impact
Authors: Hassan Joseph , Nusholtz Guy , Ding Ke
Published: June 2008

During a vehicle crash stress waves can be generated at the impact point and propagate through the vehicle structure. The generation of these waves is dependent, in general, on the crash type and, in particular, on the impact contact characteristics. This has consequences with respect to different crash barrier interfaces for vehicle evaluation. The two barriers most commonly used to evaluate the response of a vehicle in a frontal impact are the rigid barrier and the offset deformable barrier. They constitute different crash modes, full frontal and offset. Consequently it would be expected that there are different deformation patterns between the two. However, an additional possible contributor to the difference is that an impact into a rigid barrier generates waves of significantly greater stress than impacts with the deformable one. If stress waves are a significant component of real world final deformation patterns then, the choice of barrier interface and its effective stiffness is critical. To evaluate this conjecture, models of two types of rails each undergoing two different types of impacts, are analyzed using an explicit dynamic finite element code. Results show that the energy perturbation along the rail depends on the barrier type and that the early phase of wave propagation has very little effect on the final deformation pattern. This implies that in the real world conditions, the stress wave propagation along the rail has very little effect on the final deformed shape of the rail.
Automated Finite Element Modeling of Tube Frame Structure Parametric Design
Authors: Mayer Robert R. , Vaishnav Ashok
Published: June 2008

This research was intended to address the last step in the development of a tube-frame (termed B2B) parametric crashworthiness model - automated finite element modeling of the parametric design. We have added the generation of finite element models to the previously built Unigraphics Version 16 (UG V16) parametric model, so that finite element models could be quickly built. UG/WAVE was used to design the vehicle parametrically and UG/SCENARIO, a pre- and post-processor integrated in UG, was used to automatically construct the finite element mesh. We established the quality of the finite element meshes, generated for two new designs, which were created by changing overall dimensions of the vehicle. This was done using objective criteria for the finite element mesh. The component data was added to the automatically generated mesh, and the results from the crashworthiness analysis of this model compared favorably with the ‘hand-built’ model using traditional model building techniques. The results from this work will be useful in the development of the parametric design process. The use of automatically generated finite element meshes will also be useful for the automated evaluation of these parametric designs.
Closed-Loop Feedback Control of Production Part Errors
Authors: Bering Tom , Veldhuis Stephen C. , Bryson Greg , Detmers Peter
Published: June 2008

This paper presents a new supervisory controller, designed to meet or exceed the tight quality specifications required of high-volume production parts. The process optimizing controller takes Co-ordinate Measuring Machine (CMM) data collected on Statistical Process Control (SPC) samples. It analyses the data and updates the program on a Computer Numerically Controlled (CNC) milling machine to optimize the overall production process. Part specifications, including dimensions between cast and machined features, are controlled through feedback. The controller improved process capability (Cp), and by targeting the mean on the nominal dimension it significantly improved the capability index (Cpk).
A Study on the High Speed Face Milling of Ti-6Al-4V Alloy
Authors: Rao Balkrishna , Shin Yung C.
Published: June 2008

This paper is concerned with the experimental and numerical study of the high speed face milling of Ti-6Al-4V titanium alloy. Machining is carried out by uncoated carbide and polycrystalline diamond cutters in the presence of an abundant supply of coolant. Experimental analysis is conducted in terms of cutting forces, chip morphology, surface integrity and tool wear. The experimental analysis is supplemented by simulations from the finite element analysis where needed. The highest cutting speed realized for both the cutting tool materials is 600 sfpm with the diamond cutter operating at feeds lower than that for carbide. Good surface integrity in terms of residual stress and surface finish is achieved under the machining conditions used with limited tool wear. Residual stresses imparted to the machined surface are compressive with the diamond tool yielding higher values and are the most sensitive to feed. Tool wear patterns are described in terms of various cutting conditions.
Modeling of Deformations in a Ring Shaped Workpiece Due to Chucking and Cutting Forces
Authors: Malluck John A. , Melkote Shreyes N.
Published: June 2008

This paper presents a theoretical model for predicting the elastic deformations of ring-type workpieces due to in-plane chucking and cutting forces applied in turning processes. The model is derived from classical elasticity theory for bending of thin rings. Experimental results are presented to verify the strengths and limitations of this model. The results from a finite element model are also presented for comparison. For the ring diameters and radial chucking loads considered in this work, it is shown that the theoretical model is accurate to within 11% of the measured radial deformations for rings with inner-to-outer diameter ratio (Din/Dout) of 0.881. The finite element model is shown to yield slightly better results. The applicability of the theoretical model is illustrated by using it to predict the surface error produced in turning of a ring.
Effects of Radial Immersion and Cutting Direction on Chatter Instability in End-Milling
Authors: Bayly Philip V. , Mann Brian P. , Schmitz Tony L. , Peters David A. , Stepan Gabor , Insperger Tamas
Published: June 2008

Low radial immersion end-milling involves intermittent cutting. If the tool is flexible, its motion in both the x- and y-directions affects the chip load and cutting forces, leading to chatter instability under certain conditions. Interrupted cutting complicates stability analysis by imposing sharp periodic variations in the dynamic model. Stability predictions for the 2-DOF model differ significantly from prior 1-DOF models of interrupted cutting. In this paper stability boundaries of the 2-DOF milling process are determined by three techniques and compared: (1) a frequency-domain technique developed by Altintas and Budak (1995); (2) a method based on time finite element analysis; and (3) the statistical variance of periodic 1/tooth samples in a time-marching simulation. Each method has advantages in different situations. The frequency-domain technique is fastest, and is accurate except at very low radial immersions. The temporal FEA method is significantly more efficient than time-marching simulation, and provides accurate stability predictions at small radial immersions. The variance estimate is a robust and versatile measure of stability for experimental tests as well as simulation. Experimental up-milling and down-milling tests, in a simple model with varying cutting directions, agree well with theory.
Code Development and Validation of RANS Solvers for Flows Around Bluff Bodies
Authors: Khashan Saud , Alteraifi Abdullatif M.
Published: June 2008

A steady state simulation for the flow past a circular cylinder at the sub-critical Reynolds number of 3900 is conducted using a variety of non-linear eddy viscosity-based two-equation κ-ε models. Although, this simulation compromises the transient characteristics of the flow, the solution obtained using a steady state simulation showed qualitative relevance. Steady state results were closely comparable to the far more expensive and supposedly more correct time-averaged solutions obtained using transient simulations. The dissipative effect due to such turbulence modeling by far overweighs the effect of the numerical dissipation. Such dissipation dampened the intrinsic self-excited unsteadiness known to exist in such flow and enabled steady state-like solution. In-house developed finite volume based code along with a commercial finite-element code, were used. Qualitative agreement is attainable for the surface-pressure distribution over the cylinder and the centerline streamwise velocity in the wake regions. For this type of problems, the time-averaged solutions obtained using transient simulation that employs the non-linear eddy viscosity-based two-equation κ-ε type models, offered marginal improvement over those obtained using steady state simulations.
Meeting the MEMS “Design-to-Analysis” Challenge: The SUMMiT® V Design Tool Environment
Authors: Yarberry Victor R.
Published: June 2008

This paper describes the SUMMiT® V Design Tools, a suite of CAD tools that enable a SUMMiT® (Sandia Ultra-Planar Multilevel MEMS Technology) MEMS designer to meet the ‘Design-To-Analysis’ challenge. Sandia has developed a MEMS design tool suite integrated with a commercial 3D mechanical CAD tool, AutoCAD®. Designed for use with the SUMMiT® process, it includes in-house written design tools: a 2D Process Visualizer [2], a fast 3D Visualizer, a detailed 3D Model Generator [3], a finite element mesh generator [4], a library of standard components [5], and a Design Rule Check system [6].
Simulations and Statistical Analyses of the Alignment of Patterned Optical Waveguides
Authors: Shih Min-Yi , Nielsen Matt , Balch Ernie , Douglas Leonard
Published: June 2008

In this paper we investigate the tolerances required to achieve high transmission efficiencies given two planar waveguides with misalignments in both offset and overlap. More specifically, simulations of two types of waveguides, embedded and deep-ridge, with defects created during a multi-exposure lithographic process are presented along with statistical analyses results. Average efficiencies as high as 99% can be achieved with both waveguides having misalignment deviations in position as great as 0.3 μm. Overlap misalignment in the regime we explored was found to be much less critical for the planar waveguide coupling.
Nanowire Composite Thermoelectric Devices
Authors: Abramson Alexis R. , Kim Woo Chul , Huxtable Scott T. , Yan Haoquan , Wu Yiying , Majumdar Arun , Tien Chang-Lin , Yang Peidong
Published: June 2008

This paper discusses the design, fabrication and testing of a novel thermoelectric device comprised of arrays of silicon nanowires embedded in a polymer matrix. By exploiting the low thermal conductivity of the composite and presumably high power factor of the nanowires, a high figure of merit should result. Arrays were first synthesized using a vapor-liquid-solid (VLS) process leading to one-dimensional growth of single-crystalline nanowires. To provide both structural support and thermal isolation between nanowires, parylene, a low thermal conductivity and extremely conformal polymer, was embedded within the arrays. Mechanical polishing and oxygen plasma etching techniques were used to expose the nanowire tips and a metal contact was deposited on the top surface. Scanning electron microscopy pictures illustrate the results of the fabrication processes. Using the 3ω technique, the effective thermal conductivity of the nanowire matrix was measured.
Prediction of Rate-Independent Constitutive Behavior of Pb-Free Solders Based on First Principles
Authors: Sharma Pradeep , Dasgupta Abhijit , Ganti Surya , Loman James
Published: June 2008

This paper presents a methodology for the theoretical estimation of rate-independent plastic constitutive properties of Pb-free solders using three approaches. The first approach is based on a Nonlinear Effective Medium Theory (NEMT) that is scale independent. The second approach is based on the micromechanics and physics of plastic slip in heterogeneous alloys (henceforth called the physical model). This approach explicitly includes microstructural features such as grain size, particle size etc. The third approach is a combination of NEMT and the physical model. Our estimates involve no adjustable calibration parameters and are based on first principles and constituent properties. Parametric studies are conducted to show that the physical model is more effective for small particles sizes, small particle spacing and low volume fractions; while NEMT performs well for large volume fractions, large particle sizes and large particle spacing. The proposed hybrid approach, however, is valid for all particle sizes and volume fractions. Limited comparison with experimental data is also made and implications of our work in the economical design of novel Pb-free solders is discussed.
Prototyping With SUMMiT™ Technology, Sandia’s Ultra-Planar Multi-Level MEMS Technology
Authors: Shepherd Ellen
Published: June 2008

Sandia National Laboratories, a world leader in the development and application of surface micromachining technology, offers its ultra-planar, multi-level SUMMiT™ technology for prototyping devices for microelectromechanical systems (MEMS). By incorporating advanced fabrication processes, such as chemical mechanical polishing and five levels of polysilicon (four mechanical and one ground), in a well-characterized, base-lined technology, the SUMMiT™ (Sandia’s Ultra-planar, Multi-level, MEMS Technology) process offers a virtually limitless range of microelectromechanical systems that can be fabricated for both commercial and military applications [1]. Sandia’s SUMMiT™ process, licensed to industry for volume production, is available from Sandia for agile prototyping through the SAMPLES™ Program. The SAMPLES™ (Sandia’s Agile MEMS Prototyping, Layout tools, Education, and Services) Program, offers participants the opportunity to access state-of-the-art MEMS technology to prototype an idea and produce hardware that can be used to sell a concept. The four components of the SAMPLES™ Program provide: • Education and training on Sandia’s SUMMiT™ designand visualization tools, fabrication process, and reliability issues; • Layout tools for design including visualization and checking of design rules; • Fabrication in the 5-level SUMMiT™ technology; • Post-fabrication services such as release, packaging, reliability characterization, and failure analysis. This paper discusses the SUMMiT™ technology, its capabilities, and the infrastructure for prototyping within the technology through the SAMPLES™ Program.
Component Failure Analysis in MEMS Packaging
Authors: Zou J. , Waelti M. , Bowman A. , Marchetti J. , Mastrangelo C. H.
Published: June 2008

A finite element analysis (FEA) method used to determine the limits of package failure criteria is described. The failure criteria for the micro-electro-mechanical system (MEMS) packages presented here include von Mises, Mohr’s theory, and micro-crack phenomena. In addition, we explore the limits of micro-scale failure criteria on brittle MEMS assemblies. The paper describes stress source identification methods and failure mechanisms for packaged assemblies that can guide MEMS package designers to reduce potential failure modes and improve reliability.
Process-Induced Thermal Effect on Packaging Yield of RF MEMS Switches
Authors: Mercado Lei L. , Kuo Shun-Meen , Lee Tien-Yu Tom , Lee Russ
Published: June 2008

RF MEMS switches offer significant performance advantages in high frequency RF applications. The switches are actuated by electrostatic force when voltage was applied to the electrodes. Such devices provide high isolation when open and low contact resistance when closed. However, during the packaging process, there are various possible failure modes that may affect the switch yield and performance. The RF MEMS switches were first placed in a package and went through lid seal at 320°C. The assembled packages were then attached to a printed circuit board at 220°C. During the process, some switches failed due to electrical shorting. More interestingly, more failures were observed at the lower temperature of 220°C rather than 320°C. The failure mode was associated with the shorting bar and the cantilever design. Finite element simulations and simplified analytical solutions were used to understand the mechanics driving the behaviors. Simulation results have shown excellent agreement with experimental observations and measurements. Various solutions in package configurations were explored to overcome the hurdles in MEMS packaging and achieve better yield and performance.
Locally Heated Low Temperature Wafer Level MEMS Packaging With Closed-Loop AuSn Solder-Lines
Authors: Seo Young Ho , Kang Tae Goo , Cho Young-Ho , Kim Seong-A. , Kim Geun Ho , Bu Jong Uk
Published: June 2008

In this paper, locally heated closed-loop AuSn solder-line bonding method was proposed and evaluated for a low-temperature, high strength, and hermetic MEMS packaging. We fabricated two different test specimens including substrate-heated specimen and locally heated specimen in order to verify the performance of locally heated method. In air tightness test, the substrate-heated specimen and locally heated specimen show the maximum leak rate of 13.5±9.8×10−10mbar-l/s and 18.8±9.9×10−10mbar-l/s with the same internal volume of 6.89±0.2×10−6l, respectively. In the critical pressure test, any fracture was not found in the bonded specimens at applied pressure of 10±2bar. From these results, we approximately extracted the bonding strength of the proposed bonding process of 3.53±0.07MPa. By EDS (Energy Dispersive X-ray Spectrometer) analysis at bonded interface, we found that bonded interface (between AuSn solder and Ti/Au layer) of substrate-heated specimen was stronger than that of locally heated specimen.