bluuebunny/crossref_metadata_2025 huggingface dataset:
Liquid Metal Based Miniaturized Chip-Cooling Device Driven by Electromagnetic Pump
Authors: Liu Jing , Zhou Yi-Xin , Lv Yong-Gang , Li Teng
Published: April 2008

Conventional methods for thermal management of computer chips are approaching their practical application limit for recently emerging high integrity and high power processors. There is a strong demand to develop alternative approaches to accommodate to the trend of increasing industrial need. In this paper, a prototype of the newly proposed liquid metal based chip cooling device using electromagnetic pump as the flow driving force was fabricated and demonstrated. The technical routes to build up the new miniaturized system were illustrated. Being flowing based, completely electricity-controllable, and almost entirely made of metal, the new cooling device has a rather strong heat dissipation capability compared with that of the conventional forced liquid or air cooling approaches. A series of experiments successfully showed that the EM pump designed and fabricated in this paper is very flexible in driving the circulation flow of the liquid gallium, and the cooling device thus built up can significantly reduce the temperature of a simulating heating module. Further, promising strategies to optimize the present device were suggested and discussed. A series of new issues concerning the heat and fluid transport, and electromagnetic field effect of liquid metal in developing the micro/nano scale cooling devices were raised by interpreting the theoretical models established for characterizing the running behaviors of the present system. The liquid metal based cooling device would find exciting applications in the heat dissipation area where extremely high heat flux and very small geometry were seriously requested.
Fabrication and Characterization of NEMS-Based Single Nanotube Emitter Arrays
Authors: Dong Lixin , Subramanian Arunkumar , Nelson Bradley J.
Published: April 2008

Arrays of individual carbon nanotube (CNT) emitters for nanoelectromechanical systems (NEMS) are constructed and characterized. Vertically aligned single multi-walled carbon nanotubes (MWNTs) are realized using a combination of e-beam lithography and plasma-enhanced chemical vapour deposition (PECVD) growth. Field emission properties of the arrays are investigated inside a scanning electron microscope (SEM) using scanning anode field emission microscopy (SAFEM) realized from a scanning anode actuated by a 3-DOF nanorobotic manipulator with sub-nanometer resolution. With the SA-FEM and the arrays of single MWNTs, a linear nano encoder is proposed. Vertical position is detected by the change in emission current, whereas the horizontal position of the scanning anode is sensed from the emission distribution. A resolution of 98.3 nm in the vertical direction and 38.0 nm (best: 12.9 nm) in the lateral direction has been achieved. Failure mechanisms of the emitters are systematically investigated in theory and experiment. Failure modes include opening, shortening, breaking, eradicating, and telescoping, which can be identified/monitored with I-V curves and Fowler-Nordheim plots of field emission. Controlled “failures” can find applications in length modification of individual tubes in an array. As an example, selective eradication for fabricating a patterned emitter array is demonstrated. Such techniques will in turn enable applications in NEMS such as field emission based sensor and actuator arrays, nanoelectronics such as wiring or in situ construction of functional elements.
Unsteady MHD Couette Flow and Heat Transfer Between Parallel Porous Plates With Exponential Decaying Pressure Gradient
Authors: Attia Hazem A.
Published: April 2008

The unsteady Couette flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel non-conducting porous plates is studied with heat transfer. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to an exponential decaying pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the magnetic field and the uniform suction and injection on both the velocity and temperature distributions is examined.
DEPP Co-Extruded Functionally Graded Piezoceramics
Authors: Alexander Paul W. , Brei Diann , Halloran John W.
Published: April 2008

Functionally Graded Piezoceramics (FGP) offer performance similar to conventional piezoceramic actuators while reducing the problems associated with their bonded construction (high stress levels, large stress discontinuities, delamination, etc.). This paper presents the Dual Electro/Piezo Property (DEPP) gradient method and the tools necessary for designing, modeling, and producing DEPP FGP actuators including: material property gradient maps, a Micro-Fabrication by Co-eXtrusion (MFCX) process, and experimentally validated analytic and numeric performance and stress modeling methodologies that account for continuous and layered material gradients and complex electric field profiles. These models predict a dramatic internal stress reduction achieved by the DEPP method. Preliminary reliability testing confirm this with an increase in piezoelectric actuator lifetimes over 1010 cycles, improvement of almost four orders of magnitude compared to conventional piezoceramic actuation.
Effect of Voids on Thermo-Mechanical Durability of Pb-Free BGA Solder Joints: Modeling and Simulation
Authors: Ladani Leila Jannesari , Dasgupta Abhijit
Published: April 2008

The effect of process-induced voids on the durability of Sn-Pb and Pb-free solder interconnects in electronic products is not clearly understood. Experimental studies have provided conflicting ambiguous conclusions, showing that voids may sometimes be detrimental to reliability, but they may sometimes even increase the reliability of joints, depending on the size and location. Because of the higher level of process-induced voids in Pb-free solders, this debate is more intensified in Pb-free joints. This study presents Finite Element Analysis of the influence of voids size, location, and spacing on the durability of Pb-free solders. A three dimensional, global-local, visco-plastic FEA is conducted for a CTBAG132 assembly under thermal cycling. The displacement result of the global FEA at the top and bottom of the critical ball is used as the boundary condition in a local model which focuses on the details of a single ball of the CTBGA package under temperature cycling. Parametric study is conducted to model a solder ball with voids of different sizes, and locations. The maximum void size modeled is up to 6% of the ball volume. An energy-partitioning model for cyclic creep-fatigue damage is used to estimate the damage and monitor the trends as the size and location of voids are varied. Potential sites for maximum damage and crack initiation are identified. Strain based and energy based damage models are compared, for later verification with experimental studies in a future paper.
Two Phase Flow Study in Direct Methanol Fuel Cell
Authors: Ge Jiabin , Liu Hongtan
Published: April 2008

A three dimensional, two-phase, multi-component model has been developed for a liquid-fed DMFC. Both liquid and gas phases are considered in the entire anode, including the channel, the diffusion layer and the catalyst layer; while at the cathode, two-phases are considered in the gas diffusion layer and the catalyst layer but single gas phase is considered in the channel. For the electrochemical kinetics, the Tafel equation incorporating the effects of two phases is used at both the cathode and anode sides. At the anode side, the presence of gas phase reduces the active catalyst areas; at the cathode side, the presence of liquid reduces the active catalyst areas. The mixed potential effects due to methanol crossover are also included in the model. The modeling results showed that the porosity of the anode diffusion layer played a very important role in the DMFC performance. With a low porosity, the produced carbon dioxide cannot be removed effectively from the catalyst layer, thus reducing the active catalyst area as well as blocking methanol from reaching the reaction zone. A similar effect exits in the cathode for the liquid water. The modeling results also show that the single-phase flow models over-predict methanol cross-over.
Multi-Spectral Image Fusion Using Intensity Modulation and Non-Separable Wavelet Frame
Authors: Yang Xuhong , Jing Zhongliang , Li Jian-Xun
Published: April 2008

A fusion approach is proposed to refine the resolution of multi-spectral images using the corresponding high-resolution panchromatic images. The technique is based on intensity modulation and non-separable wavelet frame. The high-resolution panchromatic image is decomposed by the non-separable wavelet frame. Then the wavelet coefficients are used as the factor of modulating to modulate the multi-spectral image. Experimental results indicate that, comparing with the traditional methods, the proposed method can efficiently preserve the spectral information while improving the spatial resolution of remote sensing images.
Intrinsic Localized Modes and Nonlinear Normal Modes in Micro-Resonator Arrays
Authors: Dick A. J. , Balachandran B. , Mote C. D.
Published: April 2008

In the solid-state physics literature, nonlinear phenomena such as localizations have been studied for a number of decades in lattice structures. These localizations, which occur in periodic and strongly nonlinear discrete systems, have been found to result from a combination of the discreteness and the strong nonlinearity rather than the defects or impurities in the system. Intrinsic Localized Modes (ILMs), which are defined as spatial localization due to strong nonlinearity within arrays of oscillators, have been studied recently in the context of coupled micro-scale cantilevers. Within this paper, the hypothesis that an intrinsic localized mode may be realized as a nonlinear normal mode is explored in order to gain a better understanding of this nonlinear phenomenon. It is believed that an understanding of this phenomenon would be valuable for the design of piezoelectric micro-scale resonator arrays that are being developed for signal processing, communication, and sensor applications.
Analytical and Numerical Predictions of Thermoelastic Properties of Carbon Single-Walled Nanotubes
Authors: Veedu Vinod P. , Askari Davood , Ghasemi-Nejhad Mehrdad N.
Published: April 2008

The objective of this paper is to develop constitutive models to predict thermoelastic properties of carbon single-walled nanotubes using analytical, asymptotic homogenization, and numerical, finite element analysis, methods. In our approach, the graphene sheet is considered as a non-homogeneous network shell layer which has zero material properties in the regions of perforation and whose effective properties are estimated from the solution of the appropriate local problems set on the unit cell of the layer. Our goal is to derive working formulas for the entire complex of the thermoelastic properties of the periodic network. The effective thermoelastic properties of carbon nanotubes were predicted using asymptotic homogenization method. Moreover, in order to verify the results of analytical predictions, a detailed finite element analysis is followed to investigate the thermoelastic response of the unit cells and the entire graphene sheet network.
Chemical Mechanical Polishing of Silicon Wafers: Finite Element Analysis of Wafer Flatness
Authors: Zhang X. H. , Pei Z. J. , Fisher Graham R.
Published: April 2008

Silicon is the primary semiconductor material used to fabricate integrated circuits. The quality of microchips depends directly on the quality of silicon wafers. A series of processes are required to manufacture the high-quality silicon wafers. Chemical mechanical polishing is a necessary step to achieve the required wafer flatness. In this paper, a finite element analysis has been conducted to study the effects of influencing factors (including Young’s modulus and Poisson’s ratio of the polishing pad, thickness of the pad, and polishing pressure) on the wafer flatness.
Elasto-Hydrodynamic Analysis of Human Artificial Hip Joint Prostheses
Authors: Youness Abdel-Latif , Abde-Latif L. A. , El-Butch A. M. A.
Published: April 2008

Hip joint is one of the most important human joints that should be fully understood. The present research work aims at improving the tribological performance of the human artificial hip joint prostheses to help in producing reliable ones using design charts. An elasto-hydrodynamic model of the hip joint is proposed and numerical solution of the governing equations using finite difference technique is used to predict the elasto-hydrodynamic behavior of such joint. Parametric study has been conducted and results have shown that, thicker cup gives better tribological performance and the increase in the femoral head radius results in decreasing the non-dimensional maximum pressure and decreasing the non-dimensional minimum film thickness. Also, increasing the angular velocity doesn’t affect the tribological behavior considerably.
Measurement of Mass Flow Rate by Employing Thermometry
Authors: Machado Jean F. B. , Negra˜o Cezar O. R. , Junqueira Silvio L. M. , Mazza Ricardo A. , Morales Rigoberto E. M.
Published: April 2008

Sudden changes of flow temperature along a tube are common in industrial applications. One may suggest those changes can be related to the flow rate. The current work presents a feasibility analysis to evaluate the mass flow rate by measuring changes of temperature at two positions along a tube wall separated by a known distance. The ratio of the distance and the time to change the temperature at the two points may be related to the average flow speed. This is a convection-conduction heat transfer phenomenon at the flow and tube wall. This conjugated heat transfer is modeled by the energy conservation equation that is solved numerically. The study identifies the ranges of parameters, such as, Reynolds and Biot numbers, wall thickness, etc., on which the technique can be applied. The model results are compared to an analytical solution and preliminary experimental results.
Direct Micro Mechanical Testing Method for MEMS Materials
Authors: Li Bo , Chen Quanfang
Published: April 2008

Mechanical properties of MEMS materials are crucial for MEMS performance and reliability. Micro scale mechanical test has been challenging to MEMS community, due to the difficulties in handling micro scale specimens. In this article, a novel micro mechanical tensile testing method has been developed in combining a stiff microscale specimen developed with MTS Tytron Micro Force Tester. The advantages of this method include that it is a standard direct test of micro machined specimens, simple boundary conditions, and easy specimen handling/mounting in characterization. A novel specimen with micro features has been designed and fabricated for the direct mechanical testing. The specimen consists of three micro beams in parallel. The width of the center beam is 40 μm and the outer two beams’ width is 90 μm. The length of all three beams is 4 mm long. An optimized design has been achieved with finite element analysis, which shows that 98% of the total deformation occurs on the beams’ gage length. The stress is uniformly distributed over the three beams with a difference less than 0.5% among them. Both UV-LIGA fabricated nickel and SU-8 specimens have been tested. The UV-LIGA fabricated nickel has fracture strength of 1000±70 MPa and the results of SU-8 show a brittle behavior with fracture strength of 48±3 MPa.
Controlled Vehicle Exchange and Allocation in Dynamic Teams
Authors: Ruths Justin A. , Girard Anouck R. , Borges de Sousa Joa˜o
Published: April 2008

Here, we present a solution for safe switching amongst dynamic teams of autonomous vehicles. By team, we mean a collection of vehicles that have a common mission, or objective. The design of our solution involves a distributed hierarchical control architecture. It contains five levels that successively abstract the motion of a single vehicle into maneuvers, coordinated maneuvers, tasks and team objectives. We do this in the framework of dynamic networks of hybrid automata and sliding mode control. We establish an information interchange protocol that minimizes bandwidth use and ensures robustness in the switching process, yet allows for communications at all levels of the control architecture. We present results from simulations to demonstrate and implement these ideas.
Sliding Mode Controller and Filter Applied to a Model oft an Electrohydraulic Actuator System
Authors: Wang Shu , Burton Richard , Habibi Saeid
Published: April 2008

A new robust state and parameter estimation strategy called the Variable Structure Filter (VSF) has recently been proposed and used for state and parameter estimation. A very common problem of linear stochastic systems is to design a combined robust control and estimation strategy, given system and noise uncertainties. Variable Structure Control (VSC) and its special form of Sliding Mode Control (SMC) show superb robustness. This paper proposes a new strategy involving the Sliding Mode Control and the Variable Structure Filter. Both the estimator and controller are based on the concepts of Variable Structure Systems (VSS). In the presence of bounded parametric uncertainties and noise, a robust stability is guaranteed. Further more, the combined strategy can be used to achieve high regulation rates or short settling times. The object of this paper is to introduce this combined VSF and SMC strategy and to demonstrate its application to a third order model of a high precision hydrostatic system, referred to as the Electrohydraulic Actuator System (EHA).
Process Control System Design Experiences: A Real World Approach
Authors: Mountain Jeffrey R. , Riddick Angela D.
Published: April 2008

Hands-on, design oriented experiences have been shown to increase the visibility of the engineering profession; inspiring pre-college students to better prepare in math and science, and pursue an engineering degree. Most of these programs are successful, but they primarily focus on the creative aspects of highly specialized industries with little regard to the detail process of real world engineering design. Many students enroll in engineering programs believing the profession is solely focused on creativity and “building stuff” from a provided set of components. Once faced with the analysis and detail-oriented aspects of engineering practice, or the reality that most engineers are not employed by NASA or in robotics related industries, many students abandon engineering programs for other degree plans. The University of Texas at Tyler is using process control systems design as a theme to expose pre-college and college-level students to “common” engineering practices. This outreach program is part of a National Science Foundation funded project to provide hands-on opportunities to design, build, and test thermal/fluid based process control systems in an effort to attract and retain increased numbers of engineering students. This paper describes the proof of concept Process Control Breadboard System developed to provide a broad spectrum of students with exposure to the design of “common” engineering systems. Pre-college students come to realize that a wide range of engineering disciplines including: agricultural, chemical, electrical, mechanical, and petroleum engineering, consider process controls a part of their discipline. In addition, middle school students get exposed to the detail oriented aspects of real world engineering design; gaining experience in CAD modeling and producing bills of material prior to the hands-on build and test of their systems. Results from a variety of outreach and university level curriculum integration activities, conducted during the first two years of grant funding, will be presented, along with a summary of lessons learned and plans for future activities.
Dynamic Modeling of an Overhead Valve Engine CAM-Follower System Using a Resistive Companion Dynamic Simulation Solver
Authors: Sloope Daniel C. , Rocheleau David N.
Published: April 2008

A computer simulation model of the valve train of a Honda GX30 engine was modeled using Virtual Test Bed (VTB), a resistive companion dynamic simulation solver. Traditionally VTB has been exclusive to solving electrical system models but using the resistive companion equivalence of through and across variables, it can be applied to mechanical systems. This paper describes a dynamic simulation of an overhead valve engine cam-follower system using the VTB software application. The model was created to show valve train position, velocity and acceleration to aid in development of a camless engine being developed at the University of South Carolina. The mathematical model was created using governing dynamic equations. Using C++ programming, the mathematical model was transformed into a Virtual Test Bed model. The VTB model successfully shows valve train component position, velocity and acceleration. The significance of this work is its novelty in using the Virtual Test Bed environment to handle dynamic modeling of mechanical systems, whereas to date, VTB has been primarily focused on resistive companion modeling of power electronic systems. This work provides the foundation for using VTB to tackle more complex mechanical models.
Numerical Analysis for Influence of Plastic and Elastic Deformation of Rough Surfaces on PEHL for Line Contacts
Authors: Niu R. J. , Huang P.
Published: April 2008

In the present paper, analysis of elasto-plasto-hydrodynamic lubrication (PEHL) in the line contact is carried out to investigate the effect of heavily loaded roll-over on the change in profile of indents. The pressure and film thickness profiles are obtained to solve the Reynolds and film thickness equations simultaneously. And, both the elastic and plastic deformations of the contact, featured with an indent, have been considered. A multi-grid numerical algorithm used in EHL of line contacts is modified and then used for the oil lubricated rolling contacts. In the program, stress and plastic deformation of the indent profile are calculated with the hardening plastic stress-strain relationship according to the theories of plasticity when pressure excesses the yield stress. The results, with and without considering plastic deformation, are compared to show the different influences on the pressure and film thickness. Analysis shows that since the plastic deformation will change the surface roughness, it will significantly change the pressure but film thickness.
Numerical Simulation Support for a Stress-Based Failure Criterion
Authors: Moondra Sumit , Sakash Aaron , Kinsey Brad
Published: April 2008

Determining tearing concerns in numerical simulations of sheet metal components is difficult since the traditional failure criterion is strain-based and exhibits strain path dependence. Recently, a stress-based, as opposed to a strain-based, failure criterion has been proposed and demonstrated both analytically for sheet materials (Arrieux, 1987 and Stoughton, 2001) and experimentally for tube hydroforming (Kuwabara et al., 2003). The next steps in this progression to acceptance of a stress-based forming limit diagram is to demonstrate how this failure criterion can be used to predict failure of sheet metal parts in numerical simulations. In this paper, numerical simulation results for dome height testing specimens are presented and compared to experimental data from Graf and Hosford (1993). Reasonable agreement was obtained comparing the failure predicted from numerical simulations and those found experimentally.
Transient Analysis of Heated Soil Vapor Extraction Process With Air Sparging
Authors: Das P. M. Mohan , Amano R. S. , Roy T. , Jatkar J.
Published: April 2008

This paper presents the Heated Soil Vapor Extraction (HSVE) that has gained significant attention during the past few years. HSVE along with Air sparging has been found to be an effective way of remediating soil of various pollutants including solvents, fuels and Para-nuclear aromatics. The combined system consists of a heater/boiler that pumps and circulates hot oil through heating wells, a blower that helps to suck the contaminants out through the extraction well, and air sparging wells that extend down to the saturated region in the soil. Both the heating wells and extraction wells are installed vertically in the saturated region in contaminated soil and is welded at the bottom and capped at the top. With this technology the soil is heated by means of conduction and convection. This heating of soil results in vaporization of the gases, which are then absorbed by the extraction well. Soil vapor extraction cannot remove contaminants in the saturated zone of the soil that lies below the water table. In that case air sparging may be used. In air sparging system, air is pumped into the saturated zone to help flush the contaminants up into the unsaturated zone where the contaminants are removed by SVE well. In this analysis an attempt has been made to predict the behavior of different chemicals in the unsaturated and saturated regions of the soil. This analysis uses the species transport and discrete phase modeling to predict the behavior of different chemicals when it is heated and absorbed by the extraction well. Such an analysis will be helpful in predicting the parameters like the distance between the heating and extraction wells, the temperature to be maintained at the heating well and the time required for removing the contaminants from the soil.
An Investigation on Cutting Tool Temperatures in Composite Machining Assisted With Heat-Pipe Cooling
Authors: Liu Jie , Chou Y. Kevin , North Mark T. , Bennett Kirk A.
Published: April 2008

Metal matrix composites (MMC) are difficult to cut materials, and yet only diamond tools have been successfully utilized for such machining applications. Wear of diamond-coated tools is characterized by catastrophic coating failure (peeling off) due to the adhered work materials at the flank wear-land surface and the high stress developed at the coating-substrate interface, associated with high temperatures, because of very different thermal expansion coefficients. Temperature reductions, therefore, may delay the onset of the coating failure and offer tool life extension. A passive heat-dissipation device, heat-pipe, has been tested for cutting temperature reductions in MMC machining. Though it is intuitive that heat pipes may enhance heat transfer and plausibly reduce the tool temperatures, heat pipes may also increase heat partitioning into the tool, and complicate its effects on the heat removal and temperature reduction efficiency. This paper reports aluminum composite machining by diamond-coated tools and investigates the heat-pipe effects on tool temperature reductions. Numerical simulation of heat conduction in the cutting tool system was performed to evaluate cutting tool temperatures without and with a heat-pipe. A 3-D thermal model of the cutting tool system including coating, insert substrate, and tool holder was established. The heat source was characterized as a heat flux, a portion of the frictional heat flux at the rake face, over the chip-tool contact area. To determine the heat-partition coefficient, a separate 2-D chip model was established with a heat flux, balanced the total rake-face heat flux, over the contact and moving with the chip speed. With the tool and chip thermal models and by matching the average temperature at the tool-chip contact of the two models, the heat partition coefficient can be numerically determined. The model has been used to evaluate how the heat-pipe modifies the cutting tool temperatures. Applying heat-pipe cooling inevitably increases the heat partition into the tool despite the enhanced heat dissipation. However, the heat pipe still effectively reduces the tool-chip contact temperatures, depending upon machining conditions. Cutting tool temperatures have also been measured in machining using thermocouples. The simulation results reasonably agree with the experimental measurements.
Spray Cooling of IGBTs Under High Heat Flux
Authors: Mertens Robert G. , Rini Daniel P. , Turek Louis , Chow Louis , Sundaram Kalpathy B. , Cregger Brian
Published: April 2008

In this investigation, high current levels were applied to an IGBT and, using spray cooling, a heat flux of 825W/cm2 at the die was achieved. Current and heat flux levels achieved during this investigation could not have been done using ordinary cooling methods. The techniques used in this investigation clearly demonstrate the superior cooling performance of spray cooling over traditional cooling methods.
Retrieving Assembly Part Design Using Case-Based Reasoning and Genetic Algorithms
Authors: Chang Guanghsu A. , Su Cheng-Chung , Priest John W.
Published: April 2008

Artificial intelligence (AI) approaches have been successfully applied to many fields. Among the numerous AI approaches, Case-Based Reasoning (CBR) is an approach that mainly focuses on the reuse of knowledge and experience. However, little work is done on applications of CBR to improve assembly part design. Similarity measures and the weight of different features are crucial in determining the accuracy of retrieving cases from the case base. To develop the weight of part features and retrieve a similar part design, the research proposes using Genetic Algorithms (GAs) to learn the optimum feature weight and employing nearest-neighbor technique to measure the similarity of assembly part design. Early experimental results indicate that the similar part design is effectively retrieved by these similarity measures.
Numerical and Experimental Study on Oblique Collision of Water Droplet With a Solid Substrate
Authors: Fujimoto Hitoshi , Shiotani Yu , Tong Albert Y. , Takuda Hirohiko
Published: April 2008

This study is concerned with the collision behavior of water droplets impacting onto a solid. Three-dimensional computer simulations are performed to understand the physics of phenomena. The Navier-Stokes equations for unsteady, incompressible, viscous fluid in a three-dimensional Cartesian coordinate system are approximated and solved by a finite difference method. The VOF (Volume-of-Fluid) technique is used to track free liquid surface. The effects of liquid viscosity, surface tension, gravity, and wettability between liquid and solid are taken into account. Normal and oblique collisions of droplets with the substrate are simulated at relatively low impact inertia of droplets. Experiments are also carried out in order to validate the numerical results. The numerical results agree reasonably well with experiments. The physics of phenomena is discussed in detail from theoretical aspects.
Dynamic Instability in a High Speed Drilling Process
Authors: Huang Bo-Wun , Kuang Jao-Hwa
Published: April 2008

The variation of dynamic instability in a high speed drilling process was investigated in this article. A pre-twisted beam is used to simulate the drill. The time dependent thrust force and drilling depth are considered in the equation of motion. A moving Winkler-Type elastic foundation assumption is employed to the drill tip to approximate the time varying boundary conditions in the drilling process. The Galerkin method is used to formulate the characteristic equation in a discrete form. The variation of instability regions of the drill system is solved and analyzed by employing the multiple scales perturbation method. Numerical results indicate that unstable regions are enlarged and shifted toward a lower frequency suddenly at the moment when the drill attaches the work piece. The effects of spinning speed, pre-twisted angle and thrust force of the drill on the variation of the dynamic instability in a high speed drilling process are also studied.
Hybrid Method for Modeling Parison Extrusion in Blow Molding
Authors: Huang Han-Xiong , Miao Yan-Sheng
Published: April 2008

As the third largest plastics processing technique, blow molding is one of the fastest growing industries worldwide. In this paper, a series of simulations on the parison formation in plastics extrusion blow molding were implemented using finite element method. Then a neural network model was developed based on the numerical results. The effects of the extrusion die inclination angle, die gap, and parison length on the parison swells can be predicted using the network model. The hybrid method combining the finite element and neural network can shorten the time for the predictions drastically.
Two-Dimensional Stress Analysis and the Strength Estimation of Adhesive Butt Joints Under Static Tensile Loadings and Bending Moments
Authors: Sawa Toshiyuki , Akita Yosuke
Published: April 2008

This paper deals with a two-dimensional stress analysis of adhesive butt joints under static tensile loading and bending moments in order to contribute to an establishment of the fracture criteria of joints. Similar adherends and an adhesive bond are replaced with finite strips in the analyses. Stress distributions in adhesive joints are analyzed strictly by using the two-dimensional theory of elasticity. The effects of stiffness and thickness of adhesive bonds on the stress distributions at the interfaces are shown by numerical computations. It is found that the stress singularity occurs at the ends of the interfaces. For verification, experiments to measure the strains and the strength were carried out. The analytical results are in fairly good agreement with the experimental ones. In addition, the analytical result is also compared with the result obtained by F.E.M in order to verify the stress distributions at the interfaces. It is shown that are in a fairly good agreement.
Simulation and Active Control of Surge Instability in Axial Flow Compressors
Authors: Khaleghi H. , Boromand M. , Tousi A. M.
Published: April 2008

A one-dimensional unsteady model capable of analyzing various arrangements of turbomachinery components has been developed. Surge disturbance propagation has been captured within a turbojet engine. It is demonstrated that these instabilities can be stabilized by the use of active control strategies such as air bleeding and air injection. The effect of variable area diffuser is also studied. Two types of active control systems are considered: steady and unsteady. In steady case, mass is removed at a fixed rate from the diffuser or interstage, or mass is injected at a fixed rate into the first stage of compressor. In unsteady control, the rate of bleeding or injection is linked to the amplitude and frequency of the upstream pressure disturbances. Results show that both steady and unsteady strategies eliminate surge disturbance and suppress the instabilities. Therefore, they extend the stable operating range of compressor. It is observed that injection can reduce the amount of bleeding air. It is also shown that smaller amount of compressed air need to be removed with the unsteady control, as compared to steady case. Variable area diffuser is shown to be able of suppressing surge instabilities. Perturbations of inlet total pressure or temperature may lead the compressor to stall. Active control of instabilities caused by sinusoidal perturbations of inlet total pressure is also investigated in the present study.
Theoretical Study of Electroosmotic Flow With Replacement Solutions
Authors: Shao Zhanjie , Ren Carolyn L. , Schneider Gerry
Published: April 2008

Electroosmotic flow with solution displacement in microchannels is often encountered in many lab-on-a-chip devices where washing procedures are designed. In order to investigate the detailed flow structures for a displacement process between two different electrolyte solutions, a three-dimensional numerical model is developed in this paper. KCl solution and LaCl3 solution are mainly used as sample solutions. A 2cm long straight microchannl with a rectangle cross sectional area (height of 100μm and width of 200 μm) was employed in this study. The governing equations of applied electrical field, flow field and concentration field were numerical solved with SIMPLE algorithm, which are based on a finite control volume scheme. The observed flow structures such as back flow in the center of the channel and distortion of plug-like electroosmotic velocity profile are discussed in detail. It is found that the distortion in flow field is due to the induced pressure gradient, which is resulted from the nonuniformity of electroosmotic mobilities and electrical conductivities of two solutions. Finally, the displacement between DIUF water and LaCl3 solution is briefly studied.
A Thermo-Magneto-Mechanical Model for Ferromagnetic Shape Memory Thin Film Actuators
Authors: Lee Kwok-Lun , Seelecke Stefan
Published: April 2008

The last decade has witnessed the discovery of materials combining shape memory behavior with ferromagnetic properties (FSMAs), see, e.g., James & Wuttig1, James et al.2. These materials feature the so-called giant magnetostrain effect, which, in contrast to conventional magnetostriction, is due to the motion of martensite twins. It was first observed in NiMn2Ga single crystals, Ullakko et al.3, but later discovered in polycrystals as well, see Ullakko4. This effect has motivated the development of a new class of active materials transducers, which combine intrinsic sensing capabilities with superior actuation speed and improved efficiency when compared to conventional shape memory alloys. The effect has also been found in thin films, Rumpf et al.5, and this technology is currently being developed intensively in order to pave the way for applications in micro- and nanotechnology. As an example, Kohl et al.6,7, recently proposed a novel actuation mechanism based on NiMnGa thin film technology, which makes use of both the ferromagnetic transition and the martensitic transformation allowing the realization of an almost perfect antagonism in a single component part. The implementation of the mechanism led to the award-winning development of an optical microscanner8. Possible applications in nanotechnology arise, e.g., by combination of smart NiMnGa actuators with scanning probe technologies. The key aspect of Kohl’s device is the fact that it employs electric heating for actuation, which requires a thermo-magneto-mechanical model for analysis. The research presented in this paper aims at the development of a model that simulates this particular material behavior. It is based on ideas originally developed for conventional shape memory alloy behavior, (Mueller & Achenbach9, Achenbach10, Seelecke11, Seelecke & Mueller12) and couples it with a simple expression for the nonlinear temperature-and position-dependent effective magnetic force. This early and strongly simplified version does not account for a full coupling between SMA behavior and ferromagnetism yet, and does not incorporate the hysteretic character of the magnetization phenomena either. It can however be used to explain the basic actuation mechanism and highlight the role of coupled magnetic and martensitic transformation with respect to the actuator performance. In particular will we be able to develop guidelines for desirable alloy compositions, such that the resulting transition temperatures guarantee optimized actuator performance.
Prediction of the Sugar Mill Shaft Failure Using a Fracture Mechanics Method
Authors: Arzola Nelson , Goytisolo Rafael , Perez Ramon , Fernandez Ariel
Published: April 2008

This paper presents a new analysis scheme and the procedure used to calculate the internal forces and the stresses in the sugar cane mill shafts. One of the contributions of this research is to consider the top roller as a beam on elastic foundation. The reaction of the bagasse layer on the top roller was determined considering it as a beam on elastic foundation. A fracture mechanics based method is presented for determining the residual life of large sugar mill shafts with semi elliptical cracks. Due to the multi axial stress field, an equivalent strain energy release rate stress intensity solution is used in the Paris law to predict crack growth. Ultrasonic inspection intervals for the shafts are established. The crack zone evaluated is located in the shoulder of the bearing nearest to the square box coupling where about 85% of the service failure these types of shafts are observed [1, 2, 3].
New Mathematical Model for the Form Factor of Involute Spur Gear’s Teeth
Authors: Quinones Aisman , Goytisolo Rafael , Moya Jorge , Ocampo Roger
Published: April 2008

In this paper, a theoretical research is made on the influence of the friction force, the profile shift coefficient and the radial component of the normal force in the Form Factor applicable to the stress on spur gears’ teeth. A Gear’s FEM model was establish with the best approach to the real physical models, for the validation of the New Form Factor Model elaborated and then, the stress calculation in gear tooth root. Finally Using FEA and Multiple Lineal Regression, a new expression for the calculation of the stress concentration coefficient in the feet of the tooth, in function of the number of teeth and of the correction coefficient, was found.
Efficiency Increase in the Extraction of Sugar Cane Juice in the Sugar Cane Mills by Means of the Regulation of Hydraulic Pressures
Authors: Arzola Nelson , Goytisolo Rafael , Suarez Lester D. , Fernandez Ariel
Published: April 2008

In this paper, the distribution of pressure on the bagasse layer in the sugar cane mills and an automatic regulation proposal to increase the efficiency in the extraction of sugar cane juice is approached. An analysis that considers the top shaft-roller as a beam on elastic foundation is carried out. It is possible to determine the pressure distribution on the bagasse layer and the mill bearing reactions. The behavior of the bagasse layer reaction is analyzed for different hydraulic pressures in each side of the mill; being demonstrated, an optimal relationship of pressures to achieve a uniform compression on the bagasse layer. The optimal hydraulic pressure rate is calculated with the help of the outlined method. Finally, once this pressure relation is known, a control strategy is developed for each hydraulic cylinder.
Analysis of a Tunable Piezoelectric Resonator Using Interdigitated Electrodes
Authors: Frederick Amanda A. , Hu Hsin-Hua , Clark William W.
Published: April 2008

The use of an interdigitated electrode configuration for tunable MEMS resonators is investigated. The tuning concept utilizes a shunt capacitor concept based on the fact that the mechanical compliance (stiffness) of the system is a function of both the mechanical properties and the electromechanical coupling of the piezoelectric element. Since the electromechanical coupling is dependant on the electrical impedance of the piezoelectric element and its shunt circuit, the circuit conditions applied to the piezoelectric tuning element can be varied in such a way as to tune the vibrational frequency of the resonator [1]. By utilizing an interdigitated electrode design to elicit the d33 response of the piezoelectric, a greater electromechanical coupling is achievable, corresponding to a wider range of tunability. In this paper, a model of the resonator is presented and then used in a study to determine the parameters which result in the highest range of tunability for the resonator.
Spatial Oscillation in SHS of Ni/Al Multilayer Foils: Measurements and Models
Authors: Washington Erika B. K. , Aurongzeb Deeder , Osborne Dustin T. , Berg Jordan M. , Holtz Mark , Temkin Henryk
Published: April 2008

Spatial oscillations have been observed after self-propagating high temperature synthesis (SHS) of multilayer bi-metallic foils. These oscillations have been correlated with periodic variations in the flame front velocity. Previous researchers have reported oscillation for which the direction of the spatial oscillations coincides with the velocity vector of the flame front. In this study, we find another mechanism for creation of spatial oscillations. Experiments on Ni/Al multilayer foils show oscillations that lie normal to the propagation direction of the flame front. We observe that the effect is consistent with microstructure formation characteristic of directional solidification. The results contribute to increased understanding of SHS combustion mechanisms in thin Ni/Al films, in particular that the combustion temperature exceeds the melting point of all reactants and reaction products, and that the mechanism for formation of reaction products is solidification from a fully molten zone. Previous results from the literature have been inconclusive on these points.
Localized Constriction Resistance Effects Upon SOFC Transport Phenomena
Authors: Nelson George , Haynes Comas
Published: April 2008

Continuum level mass and electronic transport through solid oxide fuel cell (SOFC) anodes are addressed employing the analytic solution of the Laplace equation. The constriction resistance effects of conventional interconnect design upon mass and electronic transport within SOFC anodes are emphasized. Mass transfer resistance effects are created by changes in cross-sectional area between the fuel stream-anode and anode-electrolyte interfaces. Similarly, increased ohmic losses are created by the reduction in cross-sectional area from the electrolyte-anode interface to the interconnect-anode interface. These resistance effects create competing losses that may require consideration in future SOFC component designs. The following paper has pilot quantification of such effects as an introduction to performance trends and an illustration of the analytic approach applied.
Tool Selection and Path Control for Automated Anterior Teeth Coronal Canal Treatment Preparation
Authors: Dong J. , Hong S. Y. , Hasselgren G.
Published: April 2008

This paper represents a part of research plan of “Advanced Endodontic Technology Development”. In order to aid endodontic treatment a 3-D computer model of root canals has been created which shows the geometrical characteristics. The extent of work needed for root canal treatment is obtained from this 3-D model. The objective of this paper is to convert the geometrical characteristics into automatic treatment procedure planning. This computer-aided process planning for endodontic treatment determines tool selection and process method. It also calculates tool path and optimum tool movement distance. The output of this planning system is a numerical controlled program. Because of paper size limitation, only tool selection and path control during coronal canal treatment preparation for anterior teeth are discussed in the paper. The computer-aided treatment procedure planning system provides transformation from a 3-D canal model to a machine-controlled program that will yield a treated root canal ready for filling. It serves as a bridge between design (3-D canal model) and manufacturing (canal treatment). Unlike conventional methods for root canal treatment, the computer-aided treatment process planning system emphasizes a non-destructive internal tooth geometry examination and less invasive access preparation.
Two-Station Embossing Process for Rapid Fabrication of Polymer Microstructures
Authors: Yao Donggang , Yi Allen Y. , Li Lei , Nagarajan Pratapkumar
Published: April 2008

The hot embossing technique is becoming an increasingly important alternative to silicon-and glass-based microfabrication technologies. The advantage of hot embossing can be mainly attributed to the versatile properties and mass production capability of polymeric materials. However, because of the use of a large mass in thermal cycling, hot embossing is subject to substantially longer cycle times than those in traditional thermoplastic molding processes.1 The longer dwell time at elevated temperatures could further result in degradation of the embossing polymer, especially for thermally sensitive polymers. The problem exacerbates when thick polymer substrates are used. To address this problem, rapid thermal cycling of the tool is needed. One method for rapid thermal cycling is to employ a low-thermal-mass multilayer mold with electrical heating elements installed right beneath the mold surface.2 This method, however, is complex in nature and may be prone to problems caused by mismatching of thermal and mechanical properties between different layers.