bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer-Aided Power Requirements
Authors: Vavrek Edward M.
Published: May 2008

The power requirement of machinery is a necessary consideration for the sizing and selection of machine elements in the design process. The decision process of designing gears, belt drives, clutches, brakes, and bearings are designed and sized based on the power requirement of the application. I have written a software program that calculates the power requirements for three different design applications. This software program simplifies and streamlines the design and selection process by allowing the student to calculate the horsepower and torque requirement.
Secondary Instabilities of Convective Rolls in Porous Media
Authors: Neel M. C. , Nisse L.
Published: May 2008

Necessary and sufficient conditions are presented for spectral instability of convective rolls in a horizontal porous layer of infinite extent, just above the onset of convection. The analytical method, based upon the notion of Bloch wave, takes account of three dimensional perturbations, without any restriction concerning the wave vector. The Lyapunov-Schmidt method allows to compute higher orders in the expansion of the dispersion relation, involving growth rates and parameters of the disturbances. They are necessary for to arrive at a sufficient condition for spectral stability of rolls. Amplifying Bloch waves are determined.
Static Analysis of Thin Film Piezoelectric Micro-Accelerometer Using Analytical and Finite Element Modeling
Authors: Yang Zhaochun , Wang Qing-Ming , Smolinski Patrick , Yang Hongbo
Published: May 2008

On-chip microaccelerometers using piezoelectric thin films has attracted much interest due to their simple structure and potentially high sensitivity. However, the relationships between the structure of the microaccelerometer and its performance still need to be further developed in more details. In this paper we present a theoretical model for a microaccelerometer with four suspended flexural PZT/silicon beams and a central proof mass configuration. The model takes into account the effect of device geometry and elastic properties of the piezoelectric film, and is supported by the finite element analysis. The good agreement of the results demonstrates the validity of the modeling assumptions. This study shows that the accelerometer sensitivity decreases with increasing the width and thickness of the bilayer beams, and elastic modulus of the mechanical microstructure, while increasing the length of the beam, increases sensitivity. For a fixed beam thickness, a maximum sensitivity exists for appropriate PZT/Si thickness. In addition, it is found that the sensitivity is also proportional to the magnitude of the input acceleration. The results of this study can be readily applied to for on-chip piezoelectric microaccelerometer design and its structural optimization.
Optimal Design of Structural Parameters of Flexible Linkage Mechanisms for Noise Attenuation
Authors: Zhang Xianmin , Lu Jianwei
Published: May 2008

Optimal design of structural parameters of flexible linkage mechanisms for noise attenuation is studied in this paper. The sum of weighted mass of the structure and weighted measure of acoustic radiation energy is taken as the performance index, and the thickness of the links of the mechanism is taken as the design variable. Optimization is carried out based on the modified constrained variable metric method. Simulation demonstrates that the proposed method is valid.
Applicability of Pump Models for Varying Operational Conditions
Authors: Kauranne Heikki O. J. , Kajaste Jyrki T. , Ellman Asko U. , Pietola Matti T.
Published: May 2008

It is commonly known that the characteristics of a fluid power pump depend on pump type, pressure, rotational speed and displacement. But in addition to these, also all the other parameters or factors associated with the operating conditions may have a significant effect on the characteristics. The most important of these are the pump construction and size, operating point temperature and the characteristics of the oil, which also depend on temperature and pressure. The aim of this study is to show the effects that the varying operational conditions have on the characteristics of a axial piston pump, to compare the measured characteristics with other published characteristics of axial piston pumps and to study the capability of pump models to represent these characteristics. The results include information of the effects of fluid temperature, type of fluid and the setting value of the displacement on the pump characteristics along with the effects of pressure and rotational speed. The sensitivity of the pump to each of the parameters is discussed. The effect of limited information of pump characteristics on the reliability of simulation results is studied using the Schlo¨sser models.
Design and Fabrication of a High Frequency Thin Film Resonator Using Low Acoustic Impedance Reflective Layer
Authors: Lin Chung-Hsien , Chen Hong-Ren , Du Chen-Hsun , Fang Weileun
Published: May 2008

A high frequency thin film resonator using single reflective layer is presented. The reflective layer is chosen to have a low acoustic impedance to reflect acoustic waves, which is generated by the piezoelectric layer above it. With an air interface serves as a free boundary at the other end of piezoelectric layer, a high frequency resonator can be formed. Since the fabrication process included no bulk etching and multi-layer, a high manufacturability can be achieved. Moreover, the novel device and its applications can be designed to be suit many mobile communication applications.
Formation of Hexagonal Monolayers by Flow of Bead Suspensions Into Flat Microchambers
Authors: Grumann Markus , Schippers Patric , Dobmeier Michael , Ha¨berle Stefan , Geipel Andreas , Brenner Thilo , Zengerle Roland , Ducre´e Jens , Kuhn Claus , Fritsche Michael
Published: May 2008

To realize a highly parallel optical detection in bead-based bioanalytical assays, we investigate the hydrodynamic aggregation of bead suspensions in a hexagonally periodical monolayer by a pressure-driven flow through a microfluidic structure. This device consists of one inlet channel connected to a shallow chamber with a depth that only slightly exceeds the diameter of the beads. To enforce the aggregation of the beads, the flow leaves the chamber via outlet channels possessing a depth smaller than a bead diameter. This way the outlets act as barriers to the beads and force them to accumulate in the chamber. Benchmarking different chamber and outlet designs we found an optimum filing behavior for a rhombus-like aggregation chamber connected to a single outlet channel at the same width as the chamber. Here, the aperture angle of 60° fosters hexagonal aggregation patterns which leads to the highest packaging density. Reproducible filling ratios of more than 94% have been achieved. The rhombus-like chamber also shows the shows the smallest increase of the hydrodynamic resistance during filling and the best rinsing behavior which allows to minimize the volume of washing detergents used for a bioassay. Zones of accumulated beads redistribute the hydrodynamic flow through the device during the filling process. CFD-simulations, embedded in an iterative master-routine, are carried out to describe the complete process of filling and to assist the process of design optimization.
A Theoretical and Experimental Investigation of the Scaling of Micro Fan Performance
Authors: Grimes Ronan , Quin David , Walsh Ed , Davies Mark , Kunz Stefan
Published: May 2008

Mobile phones and palm top computers are following trends of increased functionality and processor speed. To allow these trends to continue, compact cooling solutions are required. One potential solution is to introduce cooling fans. However, no fan currently exists which is small enough. This paper investigates the feasibility of producing a fan on the micro scale, which could be used. Theoretical analysis predicts a reduction in efficiency as fan size is reduced. A series of geometrically similar fans was produced so that the scaling could be experimentally investigated. These fans varied in size from the macro to the micro scale. The macro scale fan, which was used as a datum, is typical of those used to cool macro scale electronic systems. The authors developed techniques for the fabrication of the smaller scale fans. These included micro electro discharge machining. Methods for testing the performance of each of these fans were also developed. The pressure flow performance of each of the fans is measured, and confirms that as the micro scale is approached fan efficiency decreases. The observed decrease in efficiency is in agreement with theoretical prediction.
Laminar Flow Around a Sinusoidal Interface Between a Porous Medium and a Clear Fluid
Authors: de Lemos Marcelo J. S. , Silva Renato A.
Published: May 2008

A number of natural and engineering systems can be characterized by some sort of porous structure through which a working fluid permeates. Atmospheric boundary layers over tropical forests and vegetation can be modeled as flow over a porous layer of irregular surface. In addition, in engineering systems one can have components that make use of a working fluid flowing over irregular layers of porous material. This paper presents numerical solutions for such hybrid medium, considering here a channel partially filled with a sinusoidal porous layer saturated by a fluid flowing in laminar regime. One unique set of transport equations is applied to both regions. Effects of Reynolds number, porosity and permeability on mean and turbulence fields are investigated. For a fixed inlet mass flow rate, increase of either porosity or permeability reduced the strength of the recirculating motion over the porous layer.
Evaluation of a Distributed Energy System Combined With Heating, Cooling and Power Generation Through Multi-Criteria Optimization
Authors: Li Hongwei
Published: May 2008

In this paper, multi-criteria analysis and thermo-economic optimization approach is applied to the analysis of a distributed energy system in an urban residential area in Beijing. System Net Present Value (NPV) is taken as the objective to be maximized with simultaneous consideration of the thermodynamic, economic and emission criteria with regarding to CO2 and NOx emissions. Technologies as gas turbine, internal combustion engine, absorption chiller and gas boiler are included in the plant superstructure. For comparison, case with gas boilers for heating, decentralized electric chillers for cooling and all power imported from grids is chosen as the reference.
Response of a Compliant Beam in a Constricted Channel Wall
Authors: Thomson Scott L. , Mongeau Luc , Frankel Steven H.
Published: May 2008

The flow through a compliant-walled channel or tube is analogous to human systems, such as blood vessels (Holt, 1969), the trachea during forced expiration (Elad and Kamm, 1989), and, with some limitations, the glottis (Conrad, 1980). Typical studies involving collapsible channels have used a rigid channel with a longitudinal section of the channel wall replaced with a deformable structure, such as a membrane. Numerical and analytical studies of the flow and accompanying wall deformation have used 1-dimensional or lumped-parameter models (e.g., Shapiro, 1977; Cancelli and Pedley, 1985) as well as detailed flow and structural models using the finite element method (e.g., Rast, 1994; Luo and Pedley, 1995, 1996; Shim and Kamm, 2002; Cai and Luo, 2003).
Measurement of the Transverse Apparent Elastic Modulus in Mammalian Cardiac Myocytes
Authors: Lieber Samuel C. , Aubry Nadine , Pain Jayashree , Diaz Gissela , Kim Song-Jung , Vatner Stephen S.
Published: May 2008

Transverse mechanical properties of mammalian cardiac myocytes, was determined by using atomic force microscopy (AFM). The AFM can be used as a nano-indentation device allowing transverse stiffness measurements to be conducted on biological cells in a physiological environment. This enables real-time biomechanical and physiological processes to be monitored with nano-scale resolution. Cellular mechanical properties were determined by indenting the cell’s body, and analyzing the indentation data with classical infinitesimal strain theory (CIST). This calculation was accomplished by modeling the AFM probe as a blunted cone. The blunted cone geometry fits the AFM force indentation data well and was used to calculate the apparent elastic modulus of the cardiac myocyte body. The mechanical properties of male 344 x Brown Norway F1 hybrid (F344×BN) rat cells was measured and an apparent elastic modulus of 35.1 ± 0.7 kPa (n = 53) was calculated. Further studies are being conducted on myocytes isolated from aged hearts to determine whether age effects cardiac mechanical properties at the level of the single myocyte.
Robust Signal Recovery From Distorted Nonlinear Sensor Data
Authors: Suranthiran Sugathevan , Jayasuriya Suhada
Published: May 2008

In an attempt to facilitate the design and implementation of memory-less nonlinear sensors, the signal reconstruction schemes are analyzed and necessary modifications are proposed to improve the accuracy and minimize errors in sensor measurements. The problem of recovering chirp signal from the distorted nonlinear output is considered and an efficient reconstruction approach is developed. Model uncertainty is a serious issue with any model-based algorithms and a novel technique, which uses a norminal model instead of an accurate model and produces the results that are robust to model uncertainty, is proposed.
Stability Analysis of Multiple Time Delayed Systems Using the Direct Method
Authors: Sipahi Rifat , Olgac Nejat
Published: May 2008

A novel treatment for the stability of a class of linear time invariant (LTI) systems with rationally independent multiple time delays using the Direct Method (DM) is studied. Since they appear in many practical applications in the systems and control community, this class of dynamics has attracted considerable interest. The stability analysis is very complex because of the infinite dimensional nature (even for single delay) of the dynamics and furthermore the multiplicity of these delays. The stability problem is much more challenging compared to the TDS with commensurate time delays (where time delays have rational relations). It is shown in an earlier publication of the authors that the DM brings a unique, exact and structured methodology for the stability analysis of commensurate time delayed cases. The transition from the commensurate time delays to multiple delay case motivates our study. It is shown that the DM reveals all possible stability regions in the space of multiple time delays. The systems that are considered do not have to possess stable behavior for zero delays. We present a numerical example on a system, which is considered “prohibitively difficult” in the literature, just to exhibit the strengths of the new procedure.
Temperature Sensitive Packaging Development for the Biotechnology Industry
Authors: Heroux Adam M. , Cummings Joel W.
Published: May 2008

The necessity of robust temperature packaging is critical as more biotechnology products are being brought to market globally. This paper will outline the steps necessary to develop temperature sensitive packaging. Development of temperature sensitive packaging is a complex process, especially for new products. The steps to develop robust packaging start and end with good design control. There are many regulating bodies that can give guidance on this topic, but the majority of the work remains with the company. Well defining the design requirements dramatically shortens the design time of any packaging. Acceptance of any developed packaging must include process verification that all product release criteria are still met at the end of the product shelf life. Once the package has been tested, and meets all of the design requirements, validation testing can begin. Validation consists of testing the package in its final configuration, against worst case scenarios. A successful temperature sensitive package would hold the required temperature range for greater than the duration of the shelf life. All validation testing must incorporate high and low temperature challenges to simulate the year round shipping that the product will face. Following these steps will aid in development of a robust package that will protect your product during transit to the final destination.
Structural and Acoustic Noise Sources Due to Turbulent Flow Through an Elbow: Formulation of Analysis Methods
Authors: Hambric Stephen A. , Peltier L. Joel , Fahnline John B. , Boger David A. , Poremba John E.
Published: May 2008

The low-frequency structure- and fluid-borne noise from elbows excited by fluctuating forces within turbulent fluid flow is investigated. Computational Fluid Dynamics (CFD) Reynolds Averaged Navier Stokes (RANS) analyses of the flow through a piping elbow with a radius to diameter ratio of 2.8 compare favorable to measurements made by previous investigators. The CFD RANS solutions are post-processed to estimate the spectra of the fluctuating wall pressures beneath the turbulent boundary layer (TBL) flow. The CFD RANS solutions are also used to identify regions within the core flow that might excite acoustic modes within the piping fluid. A finite element (FE) model of the piping walls is coupled with a boundary element (BE) model of the interior acoustic fluid and is excited by the fluctuating wall and fluid forces estimated from the CFD RANS solutions. The power transmission through the inlet and discharge ports of the elbow is computed and separated into its structure-borne and fluid-borne components. The influence of both structural and acoustic resonances on the power transmission is evident for both excitation mechanisms. The power transmission curves at the elbow ports may be used as source inputs to transfer matrix models of piping systems that contain elbows.
Parallel-Modulated Neural Network Friction Component Model for Automotive Powertrain Systems
Authors: Cao M. , Wang K. W. , Fujii Y. , Tobler W. E.
Published: May 2008

In this paper, a new hybrid neural network friction component model is developed for dynamic powertrain (PT) analysis. With improvement over the previous hybrid network modeling techniques, the structural information of the available physical and empirical correlations is utilized to construct a parallel-modulated neural network (PMNN) architecture. The new neural network consists of small-sized parallel subnetworks reflecting specific mechanisms of the friction component engagement process. The network is successfully trained and tested using both experimental and analytical data. The PMNN-based friction component model isolates the contribution of engagement pressure on engagement torque while identifying the nonlinear characteristics of the pressuretorque correlation. Furthermore, it provides a simple torque formula that is scalable with respect to engagement pressure. All these features make the PMNN model a better tool for the purpose of powertrain system simulation and controller design, as compared to a conventional neural network model.
A Novel Compact Method for Thermal Modeling of On-Chip Interconnects Based on the Finite Element Method
Authors: Gurrum Siva P. , Joshi Yogendra K. , King William P. , Ramakrishna Koneru
Published: May 2008

Prediction of the temperature field generated with Joule heating in multilayer interconnect stacks is of critical importance for the design and reliability of future microelectronics. Interconnect failure due to electromigration is strongly dependent on its temperature. Simple models fail to capture thermal interaction between layers and within the layer. Detailed simulations on the other hand, take tremendous time and require large storage. This paper describes a threedimensional compact thermal modeling methodology that captures thermal interactions at a lower computational cost and storage requirements. The method is applicable for arbitrary geometries of interconnects due to the use of the finite element method. Case studies with three interconnects placed on a single level at a pitch of 1.0 μm generating different heat rates are reported. The compact model predicts a temperature rise of 4.11 °C at a current density of 10 MA/cm2 for 6.0 μm long interconnects of 0.18 μm width and an aspect ratio of 2. The error in maximum temperature is about 5% when compared with detailed simulations. The compact model for the current cases consists of 219 nodes whereas the detailed model has 99,000 nodes where temperature is computed.
Sensitivity Analysis of the Material Flow Stress in Machining
Authors: Fang Ning
Published: May 2008

Among the effects of strain hardening, strain-rate hardening, and temperature softening, it has long been argued about which effect is predominant in governing the material flow stress in machining. This paper compares four material constitutive models commonly employed, including Johnson-Cook’s model, Oxley’s model, Zerilli-Armstrong’s model, and Maekawa et al.’s model. A new quantitative sensitivity analysis of the material flow stress is performed based on Johnson-Cook’s model covering a wide range of engineering materials, including plain carbon steels with different carbon contents, alloyed steels, aluminum alloys with different chemical compositions and heat treatment conditions, copper and copper alloys, iron, nickel, tungsten alloys, etc. It is demonstrated that the first predominant factor governing the material flow stress is either strain hardening or thermal softening, depending on the specific work material employed and the varying range of temperatures. Strain-rate hardening is the least important factor governing the material flow stress, especially when machining aluminum alloys.
An Actuator for Controlling the Area of Dielectric Layer of the Tunable Capacitor by Commercial CMOS Fabrication
Authors: Chiou Jing-Hung , Lin Ran-Jin , Dai Ching-Liang , Yen Kai-Hsiang , Shih Yu-Ching , Chung Chen-Kuei
Published: May 2008

This study describes the fabrication of an actuator of controlling the area of a dielectric layer using the commercial 0.35μm Single Polysilicon Four Metals (SPFM) Complementary Metal Oxide Semiconductor (CMOS) process and a post-process. The post-process requires wet and dry etching without using a mask to etch sacrificial layers and release the structures suspended in the actuator. The actuator is composed of a top suspended plate, a bottom fixed plate, and a laterally yielding cantilever beam, and two fixed curved electrodes. One end of the cantilever beam is anchored whereas the other end is connected to the suspended plate. The fixed curved electrodes and the cantilever beam are stacked layers of metals and via layers, formed by the CMOS process. The cantilever beam is deflected over a large distance using electrostatic force and the suspended plate swings laterally to increase or decrease the area of overlap between itself and the bottom fixed plate. The dimensions of the actuator are: suspended plate diameter = 100 μm; cantilever beam width = 2 μm, height = 6 μm, and length = 300 μm. The moved end of the cantilever beam, connected to the suspended plate, is deflected by 25 μm when a dc power supply of 60V is applied to it.
Contact Reliability of Innovative Compliant Interconnects for Next Generation Electronic Packaging
Authors: Ma Lunyu , Zhu Qi , Sitaraman Suresh K.
Published: May 2008

The ongoing research work at Georgia Institute of Technology, PARC, Inc., and Nanonexus, Inc. funded by NIST/ATP, aims to develop a novel compliant interconnect technology based on stress-engineering of thin-film metal deposition. The minimum pitch size can reach as small as 6 μm. The fabrication of the stress-engineered compliant interconnect is compatible with the standard IC fabrication processes. Therefore, the compliant interconnect fabrication can be fully integrated into front-end semiconductor process. Also, thousands of interconnects can be fabricated on the wafer in one batch, which can greatly reduce the cost, improve the yield, and facilitate wafer level packaging (WLP). Based on the mechanical advantage of the stress-engineered compliant interconnect, a non-soldering assembly process has been developed. In the non-soldering assembly process, compliant interconnects are pressed against the bonding pads to establish the electrical connection. Test vehicles with such non-soldering contact interconnect have been assembled and subjected to thermal cycling. Although the assembled test vehicles have shown reliability over 1000 cycles, the primary mode of failure occurs at the contact interface between the compliant interconnect tip and the bonding pad. This contact interface is studied using analytical and numerical models to understand the reliability of freestanding sliding-contact compliant interconnect assembly.
Experimental Characterization of Low Voltage Field Emission From Carbon-Based Cathodes in Atmospheric Air
Authors: Peterson M. S. , Fisher T. S. , Garimella S. V. , Schlitz D. J.
Published: May 2008

Nanoscale carbon-based field-emitter materials exhibit excellent electron field emission properties, characterized by low turn-on voltages and high current densities. The use of these materials has not been previously considered for ion generation in air, yet these properties suggest that substantial ionization may occur at low voltages compared to conventional methods involving glow or arc gas discharges. Electron field emission from carbon-based materials, including polycrystalline diamond and carbon nanotubes, in atmospheric pressure air is experimentally characterized. Electric fields between 30 V/μm and 100 V/μm applied between the two terminals produce field-emitted electrons via quantum tunneling. These electrons then travel through the electric field colliding with neutral air molecules and occasionally ionizing them. This process can produce a self-sustained current flow (from fractions of picoamperes to microamperes) between the anode and cathode. The current remains stable at voltages lower than those predicted by Paschen’s curve for gaseous breakdown and ionization. Results indicate the presence of field emission from the cathode that aids in sustaining current at low voltages. The observed behavior suggests that this method can achieve efficient generation of ions for air purification and ionic flow pumping.
Synthesis of Shape Morphing Compliant Mechanisms Using Load Path Representation
Authors: Lu Kerr-Jia , Kota Sridhar
Published: May 2008

Synthesis of shape morphing compliant mechanism is inherently different from typical single output problems, due to the multiple output points along the morphing boundary. Two synthesis approaches, using a fixed initial discretization mesh and using a load path representation, have been developed previously to simultaneously address the topology, size, and geometry aspects of a compliant mechanism. Due to insufficient diversity in later generations, pre-matured convergence to sub-optimal solution is observed in the load path approach. In this paper, additional genetic operation strategies are introduced to enhance the design diversity in each Genetic Algorithm population. The capabilities and limitations of the fixed mesh approach and the improved load path approach are studied through several examples. The results show that the load path approach can achieve better quality solution with less computation time than the fixed mesh approach. The load path representation can potentially lead to a fully systematic synthesis approach due to the absence of a prespecified initial discretization mesh. Boundary conditions are currently being incorporated into the design variable to understand their importance in structural topology.
MEMS Gyro Modal Analysis and Design Tool
Authors: Chiou J. Albert
Published: May 2008

A gyroscope is used to measure angular rates for may applications such as automotive applications, navigation applications, military applications, consumer electronics applications, and robotics applications, etc. For our specific automotive applications, the gyro is used to sense the yaw, roll, and pitch angular rates for ride stabilization and rollover detection. The tuning-fork gyro device used is a double gimbaled vibratory gyroscope supported by flexures with the vibrating mechanical element made of silicon. In order to drive the gyro device with a low voltage and a high quality factor (Q), the sensing element is sealed in a high-vacuumed package. The operational resonant frequencies are very critical to the ASIC control circuit. The purpose of this study is to perform modal analyses, validate the simulation results with testing data, and provide a design tool for quick gyro element resonant frequency predictions in order to reduce design and product development cycle time. The process tolerance and design limit can also be quickly evaluated before the wafer is built.
Advanced Multi-Mode Control Strategy for a Parallel Hybrid Electric Vehicle Based on Driving Pattern Recognition
Authors: Jeon Soonil , Lee Jang-Moo , Park Yeong-Il
Published: May 2008

The adaptive multi-mode control strategy (AMMCS) is defined as the control strategy that switches control parameters for the purpose of adjusting vehicles to diverse traffic conditions and driver’s habits. This strategy is composed of off-line and on-line procedures. In the off-line procedure, several sets of control parameters are optimized under representative driving patterns (RDP). In the on-line procedure, the control parameter switching or interpolation is periodically activated based on the driving pattern recognition (DPR) algorithm, assuming that the driving pattern during the future control horizon doesn’t change significantly compared to the past pattern. The AMMCS is conceptually similar to one of predictive control theories, namely the receding horizon control which is also known as model predictive control. The AMMCS is expected to be applied well to hybrid electric vehicle (HEV) system which is very sensitive to driving patterns. Furthermore, the AMMCS can be combined with the two conventional control strategies using global and local optimization techniques to improve performances further. The design goal of the AMMCS is to minimize fuel consumption and NOx for a pre-transmission single shaft parallel HEV.
An Experimental Method to Measure Q-Parameter for Two Parameter Theory of Ductile Fracture
Authors: Kim Dong-Hak , Lee Jeong-Hyun , Kang Ki-Ju
Published: May 2008

In the two parameter approaches, one of the second parameters, T-stress, Q and A2 is used together with J-integral to describe the constraint loss near the crack tip under large scale yielding states. Among the second parameters, Q seems to be most promising from a practical point of view because it applies for three-dimensional geometries. In order to determine the Q for a given geometry and load, however, three-dimensional elastic-plastic finite element analysis, which is time consuming and costly, has had to be performed so far. In this work an experimental method to measure Q-parameter insitu is described. The basic idea comes from the fact that side necking near a crack tip indicates the loss of stress triaxiality, which can be scaled by Q. From the out-of-plane displacement and the in-plane strain measured on the surface of side necking near the crack tip, stress field averaged through thickness is calculated and then Q is determined from the difference between the stress filed and the HRR field corresponding to the identical J-integral. To prove the validity, three-dimensional finite element simulation has been performed for a CT configuration with side-grooves. Q-value which was calculated directly from the near-tip stress field is compared with that determined by simulating the experimental procedure according to the proposed method, that is, the Q-value determined from the lateral displacement and the in-plane strain. Also, the effect of location where the displacement and strain are measured is explored. Moreover, an easy way for measuring the displacement and strain simultaneously is described. That is based on Stereoscopic Digital Photography and high resolution Digital Image Correlation (DIC) software, and can be performed along with conventional fracture tests. A case study for a CT specimen of ferritic steel is presented.
Nonlinear Vibration Properties of a Current-Controlled Attractive Type Maglev System
Authors: Xu Zhixiang , Feng Zhengjin , Seto Kunisato , Tamura Hideyuki
Published: May 2008

Because maglev system has very complicated dynamic properties due to nonlinearity of the magnetic force, it is a very interesting study subject for dynamics researchers. We, in this paper, focused our study interest on a current-controlled attractive type maglev system, and analyzed its nonlinear vibration properties by numerical simulation method. The current-controlled attractive type maglev system is a feedback system based on a PD-controller that adjusts the current of the electromagnet to stably levitate a body with constant gap. The ranges of the system’s feedback gains with which the system will be stable are determined by nonlinear system dynamics analysis. From the numerical simulation results, we found out that when the system is excited by a harmonic motion, the levitated body of the system shows many kinds of vibration phenomena with the variation of the system’s feedback gains in their available ranges. Especially, chaotic vibrations can also occur in this maglev system for some suitable system’s feedback gains.
Investigation of Shape Recovery Characteristics on Ferrous Shape Memory Alloy
Authors: Wada Manabu , Naoi Hisashi , Tsukimori Kazuyuki
Published: May 2008

Aims of this study are to clarify the shape recovery characteristics on ferrous shape memory alloy in order to utilize one as a many kinds of mechanical components. In this study, Fe-Mn-Si-Cr shape memory alloy is used. The fundamental characteristics and the shape recovery characteristics are investigated in this alloy. From the result of this investigation, shape recovery strain without training process reaches to maximum value of 2% at the amount of 5∼7% work-strain. That with the training process reaches 3.5% in the maximum, which is 1.8 times of that without training process. In addition, the shape recovery characteristic under constant stress which is given during the heating process is investigated. The microstructure of the deformed material is observed. The Widmanstatten structure is generated. This structure is attributed to the transformation from austenite to ε-martensite. In order to enable the prediction analysis of the shape recovery behavior, the relationship between shape recovery strain and work-strain is formulated by the regression analysis in cubic equation.
Effect of Moisture on the Elastic Modulus and Interfacial Adhesion of Polymer-Metal Components in Microelectronic Assemblies
Authors: Ferguson Timothy P. , Qu Jianmin
Published: May 2008

Moisture poses a significant threat to the reliability of microelectronic assemblies and can be attributed as being one of the principal causes of many premature package failures. It is a multi-dimensional concern in electronic packaging, having an adverse effect on package reliability by changing both the mechanical properties and interfacial adhesion of the microelectronic assembly. In this paper, a study has been conducted to evaluate the moisture-induced degradation of both the elastic modulus of a commercially available no-flow underfill and the interfacial adhesion of the underfill to a copper alloy substrate. Three different levels of moisture preconditioning, 85C/50%RH, 85C/65%RH, and 85C/85RH%, were implemented in this study. Diffusion coefficient test specimens were constructed to experimentally measure the moisture diffusivity into the underfill resin and obtain the moisture saturation concentration for each level of moisture preconditioning. Flexural bend test specimens were made to characterize the effect of moisture on the elastic modulus of the underfill adhesive. Last, interfacial fracture toughness specimens with prefabricated interface cracks were used in a four point bending test to quantify the effect of moisture on interfacial fracture toughness. The results of this study will aid in the development of more robust microelectronic assemblies, demonstrating how both the elastic modulus and interfacial toughness change as a function of moisture concentration.
Effect of Angle and Separation Distance on Heat Transfer on an Inclined Surface Subject to Airflow
Authors: Rasipuram Srinivasan C. , Nasr Karim J.
Published: May 2008

Impinging jets may be used to achieve enhanced local heat transfer for convective heating, cooling, or drying. The issuing jet may contact the surface normally or obliquely. Factors such as jet attachment, surface angle, jet angle, separation distance between jet orifice and surface of impingement, and trajectory influence heat transfer dramatically. This study addresses the thermal problem of jet impingement on an inclined surface. This investigation is motivated by the practical application of air jets issuing out of a defroster’s nozzles and impinging on the inclined windshield surface of a vehicle. Effect of incoming fluid velocity, angle that the inclined surface makes with the horizontal plane and angle of impinging jet on heat transfer will be examined. The results are correlated in terms of governing dimensionless parameters. The end-result will be a numerically-based correlation that is capable of predicting heat transfer on an inclined surface subject to impinging airflow.
Design of Radio Frequency (RF) MEMS Switches: Modeling
Authors: Zhu Yong , Espinosa Horacio D.
Published: May 2008

Mechanical modeling of RF MEMS switches is important for performance optimization and device reliability. 1-D, 2-D, and 3-D linear analytical models have been proposed to analyze the electrostatic pull-in of a fixed-fixed beam at small deflection. However, most RF MEMS switch structures work at large deflection range. In this paper, 1-D, 2-D, and 3-D nonlinear analytical models suitable for large structural deflection are developed in a generalized form. In some practical applications, finite element models are required to account for the effects of all the design parameters: switch geometry, non-uniform state of residual stress, temperature and etc. A 3-D finite element model between structural, electrical and thermal domains is developed. This 3-D model is applicable to the design of all types of electrostatic actuators, though that of a capacitive coupling switch was examined.
A Multigrid Based Multi-Scale Thermal Analysis Approach for Conjugate Problems Involving Discrete Heating
Authors: Tang Lan , Joshi Yogendra K.
Published: May 2008

A multi-grid enhanced multi-scale analysis approach is presented for conjugate heat transfer systems with a large range of length scales of interest. The multi-scale analysis involves a sequential two-step “zoom-in” approach to resolve both the large length scale associated with the enclosure and the smaller length scale associated with fine spatial structures of heat sources. Significant computation time saving with this approach is realized compared to conventional computational fluid dynamics/computational heat transfer (CFD/CHT) modeling. Performance of the multi-scale approach is further enhanced by integrating the multi-grid technique as the CFD/CHT solver. Implementation of the enhanced approach is demonstrated for the thermal analysis of an array of discrete heat sources cooled by mixed and forced convection. It is found that the multi-grid enhanced multi-scale thermal analysis reduces simulation run time by 90% compared to multi-grid with SIMPLER. And the temperatures computed from the approach are in good agreement with measurements, deviate by no more than 8% from measurements.
Active Torsion Bar Body Roll Minimization System: Design and Testing
Authors: Cimba David , Gilbert Kyle , Wagner John
Published: May 2008

Sport utility and light-duty commercial vehicles exhibit a higher propensity for rollover during aggressive driving maneuvers, emergency scenarios, and degraded environmental conditions. A variety of strategies have been proposed to reduce vehicle body roll including active suspensions, comprehensive yaw stability systems, and active torsion bars. The active torsion bar systems have recently gained popularity due to their cost effective design and adaptability to existing chassis systems. However, the development of new control algorithms, design of subsystem components, and the evaluation of parameter sensitivity via testing a full scale vehicle is not always practical due to cost and safety concerns. Thus, a modular simulation tool and bench top testing environment is required to facilitate design and performance studies. In this paper, a series of mathematical models will be introduced to describe the vehicle dynamics and the roll prevention system. Representative numerical results are discussed to investigate a vehicle’s transient response with and without an active torsion bar system, as well as the impact of torsion bar and hydraulic component design parameters. Finally, a hardware in-the-loop test environment will be presented.
Configuration Analysis of a Novel Zero CO2 Emission Cycle With LNG Cryogenic Exergy Utilization
Authors: Zhang Na , Lior Noam
Published: May 2008

A novel liquefied natural gas (LNG) fueled power plant is proposed, which has virtually zero CO2 and other emissions and a high efficiency. Natural gas is fired in highly enriched oxygen and recycled CO2 flue gas. The plant operates in a quasi-combined cycle mode with a supercritical CO2 Rankine-like cycle and a CO2 Brayton cycle, interconnected by the heat transfer process in the recuperation system. By coupling with the LNG evaporation system as the cycle cold sink, the cycle condensation process can be achieved at a temperature much lower than ambient, and high-pressure liquid CO2 ready for disposal can be withdrawn from the cycle without consuming additional power. The net thermal and exergy efficiencies of a base-case cycle are found to be over 65% and 50% respectively, which can be increased up to 68% and 54% when reheat is used. Cycle variants incorporating reheat, intercooling, and reheat+intercooling, as well as no use of LNG coldness, are also defined and analyzed for comparison. The approximate heat transfer area needed for the different cycle variants is also computed. Besides electricity and condensed CO2, the byproducts of the plant are H2O, liquid N2 and Ar.
Heat Transfer Coefficient for a Packed Bed of Shredded Materials
Authors: Saidi Mohammad S. , Rasouli Firooz , Hajaligol Mohammad R.
Published: May 2008

Heat transfer coefficient of packed beds of shredded materials such as biomass fuels at low Peclet numbers is of interest. Due to the dependence of flow distribution on particle shape, the application of the Nusselt number correlation of packed bed of spherical particles overestimates the rate of heat transfer. This discrepancy is even more pronounced due to channeling effect at low Peclet numbers. Here, based on applying a pore submodel and combining the numerical simulation and experimental results of a cylindrical packed bed, a new correlation is derived for apparent Nusselt number of the packed bed of shredded materials. The correlation is approximated by a power law formulation for Pecelt < 25. The Nusselt number calculated from this correlation is in a good agreement with other experimental data.
Characterization of Anisotropic Conductive Adhesives
Authors: Dasgupta Abhijit , Caers J. , Iyer Preethi , Baumgaertner Pascal , Farley Daniel
Published: May 2008

Thermomechanical stress analysis of Flip-chip-on-flex (FCOF) has been investigated. The effect of bonding pressure on the reliability is analyzed. Key findings are: shear forces are the dominant forces acting across the interconnect and govern the reliability of the package, FCOFs bonded at higher pressures develop lower shear stress and packages with higher bump heights exhibit better performance. This study encompasses testing of packages under thermal shock treatment and results being verified by a 2D linear elastic model. Parametric studies that might provide useful design guidelines are also included.
Controller Design for a Non-Redundant Cable Robot Under Input Constraint
Authors: Oh So-Ryeok , Agrawal Sunil K.
Published: May 2008

Cable-suspended robots are structurally similar to parallel actuated robots but with the fundamental difference that cables can only pull the end-effector but not push it. From a scientific point of view, this feature makes feedback control of cable-suspended robots lot more challenging than their counterpart parallel actuated robot. In this paper, we look into control design for a non-redundant cable-suspended robot under positive input constraints. The design is based on feedback linearization controllers augmented with reference signal management. Reference signal management operates in accordance with the receding horizon strategy, by generating admissible reference signals which makes system not to violate the input constraints. An important issue in implementing predictive horizon algorithm for nonlinear systems is to predict the system behavior in a computationally efficient way. We show that feedback linearization controllers with reference signal management can offer an efficient way to predict the system’s future states, using the error dynamics of inner feedback loop. Finally, the effectiveness of the proposed method is illustrated by numerical simulation and laboratory experiments on a six degree-of-freedom suspended cable robot.
Acoustically Induced Manipulation of Materials: Experimental Findings and Implications for Laser Metal Deposition
Authors: Venturelli Philip A.
Published: May 2008

This paper presents the concept of acoustic levitation as a materials manipulation enhancement for the laser metal deposition process, and outlines directions for future R&D based on work performed at the California Institute of Technology. The problem discussed in this paper is the means by which acoustic energy is used to levitate and control the motion of material. To this end, results are presented from a series of experiments, and two control parameters are compared in terms of their effect on acoustic pressure. The viability of using these control parameters for material manipulation is discussed, and existing acoustic radiation force models are presented.
Prediction of Workpiece Location Error Due to Fixture Geometric Errors and Fixture-Workpiece Compliance
Authors: Raghu Anand , Melkote Shreyes N.
Published: May 2008

Workpiece location relative to the cutting tool is affected by the accuracy of part placement in the fixture. A number of error sources are known to contribute to the resulting workpiece location error, which can lead to poor part quality. The major sources include fixture geometric error and elastic deformation of the fixture and workpiece due to fixturing forces. In this paper, workpiece location error is predicted by modeling the process of part loading (given fixture geometric variations) and clamping (given deformations at the contact points) in a machining fixture. Linear elastic models for the fixture elements, contact mechanics models at the region of contact, and the flexibility influence coefficient method for the bulk elasticity of the workpiece have been used to model the compliance of the entire fixture-workpiece system. The deformations at the contact points are obtained by solving a constrained optimization model. The effect of geometric errors and compliance on workpiece location error is examined using part response points as a measure of quality, through examples involving a 3-2-1 machining fixture.