bluuebunny/crossref_metadata_2025 huggingface dataset:
A Combined PLIF/PIV System for Simultaneous Gas-Phase Temperature/Velocity Imaging
Authors: Kearney Sean P. , Grasser Thomas W. , Bourdon Christopher J.
Published: June 2008

This paper reports non-intrusive temperature and velocity imaging measurements in gas-phase flows using acetone planar laser-induced fluorescence (PLIF) thermometry and particle image velocimetry (PIV). The details of the combined PLIF/PIV instrument and the demonstration flow facilities are provided and results are presented from a turbulent Rayleigh-Be´nard convection flow (PLIF only) and from an unsteady laminar impinging jet flow (combined PLIF/PIV). The data show that PLIF temperature imaging at laboratory scales is most effective for characteristic temperature differences on the order of 100 K of more. Simultaneous gas-phase temperature-velocity images are presented which show that PLIF-PIV holds promise for detailed laboratory scale measurements for gas-phase convective heat-transfer applications at high temperature differences.
Fundamental Issues and Latest Development in Holographic Particle Image Velocimetry
Authors: Pu Ye , Cao Lujie , Meng Hui
Published: June 2008

Holographic PIV (HPIV) is currently the most promising technique for truly instantaneous, three-dimensional (3D), three-component (3C) velocity field measurements for complex flows including turbulent and multiphase flows. This paper reports new understanding on some fundamental issues and challenges in HPIV including the complex 3D imaging characteristics, the extraction of full particle information (intensities, sizes, and locations) in 3D space, the extraction of particle displacements, and the huge data volume to process. The latest off-axis HPIV system will be presented, which incorporates the new understanding of imaging characteristics of particle holography, careful development of data processing algorithms, and a well-designed distributed parallel processing system. We will demonstrate capabilities of HPIV by a semi-time-series measurement of instantaneous 3D, 3C velocity fields in highly 3D vortical flow.
Time-Resolved Spray-Droplet Velocity and Size Measurements via Single Camera Laser Sheet Imaging and Planar DPIV
Authors: Brady Michael R. , Abiven Claude , Vlachos Pavlos P. , Papadopoulos George
Published: June 2008

This paper describes a first effort to investigate the feasibility of droplet size and shape characterization by direct laser sheet imaging using time resolved Digital Particle Image Velocimetry. A 60-degree conical, high-pressure spray generated a poly-dispersed droplet distribution. Measurements were preformed for seven planes parallel to the spray axis, and separated by 4mm. A CMOS camera recorded the DPIV images at sampling rate of 10 KHz. Advanced image processing techniques were employed to identify the droplets and individually resolve their velocity using a hybrid cross-correlation particle-tracking algorithm. Subsequently, the size distribution of each droplet was quantified using geometric optics theory to convert the droplet image information to the true droplet size. Finally, the entire volume of the spray velocity and size distributions was reconstructed in a time-averaged sense. The droplet sizes from our direct imaging DPIV system were validated using a Phase Doppler Particle Analyzer (PDPA). The calculated sizes from the direct imaging methodology were found to agree with the measured PDPA results for droplets images larger than the diffraction limited diameter. Resolution limitations introduced inaccuracy for smaller droplets. In addition, the shedding frequency of the spray ligament was observed to be on the order of 1KHz, demonstrating the feasibility of using a high speed, direct imaging system in the characterization of unsteady, liquid sheet breakup properties. This preliminary effort illustrates the potential of performing global time resolved velocity and size measurements using a simple DPIV configuration based on CMOS imaging technology.
Fatigue Performance of AAR Class B Railroad Wheel Steel at Ambient and Elevated Temperatures
Authors: McKeighan Peter C. , McMaster Fraser J. , Gordon Jeffrey E.
Published: June 2008

Classical stress-life (S-N) curves were developed for AAR Class B wheel steel with specimens removed from the tread area of an as-forged railcar wheel. The specimen geometry was a standard hourglass fatigue test specimen with a low stress concentration (Kt) of 1.05. Fatigue testing was performed at stress ratios of −1.0, 0.05, 0.5 and 0.7. Testing was performed at ambient, 500°F and 1000°F using high current resistance or convection methods. Endurance limit data was obtained for all R-ratios, although for the 1000°F condition there did not appear to be a clear endurance limit transition. These endurance limit data were used to estimate the Sines parameters, A and α.
Development of a Self-Contained Sensor Bearing for Rail Applications
Authors: French Michael L. , Williams Samuel R.
Published: June 2008

This paper discusses bearing borne sensor system development efforts for use in monitoring the rail bearing and connected mechanical system. The measurement of speed, temperature, and vibration are considered. In the area of vibration analysis, particular emphasis is placed on the use of computationally efficient algorithms for use in parameterization of the vibration signal. Results from laboratory test data are presented. Finally, the relative merits of a wired versus a wireless communication channel, at the bearing level, are discussed.
2001–2002 Report of Survey Committee: Progress in Passenger Rail Vehicle and Component Engineering
Authors: Hesser Kenneth R.
Published: June 2008

This annual ASME committee report covers selected worldwide developments in passenger rail vehicles components and systems. The information contained herein was obtained from responses to survey letters sent to the manufacturers of passenger rail vehicles and components, and from a review of trade and technical publications.
Nonlinear Dynamic Study of a Bistable MEMS Beam Toggled by Optical Actuation
Authors: Sulfridge Marc , Saif Taher , Miller Norman
Published: June 2008

In (Sulfridge, et al., 2001) we presented an actuation scheme for toggling a bistable MEMS from one stable state to the other using the radiation pressure of light. The experiments on radiation pressure revealed some unexpected behavior of the beam when toggled by short duration laser pulses. While long duration laser pulses reliably toggled the beam every time, short duration pulses only seemed to toggle the beam about half of the time. This paper presents a new, nonlinear dynamic analysis of the bistable beam device used in those experiments that explains this anomalous behavior.
A Micromachined Combustor and Its Application to Micro Thermoelectric Power Generation
Authors: Zhang Chunbo , Najafi Khalil , Bernal Luis P. , Washabaugh Peter D.
Published: June 2008

This paper reports a micromachined combustor and its application to micro thermoelectric power generation. The combustor chamber is covered by a ∼1.3μm thick dielectric diaphragm which is supported by a silicon support rim bonded to a glass substrate. The diaphragm is coated with Pt-catalyst and incorporates a heater for ignition. Scaling effects on self-sustained catalytic combustion are investigated for a square combustor chamber. The small size limit for self-sustained combustion at a hydrogen flow rate of ∼3sccm is found to be between 1 to 2mm. Very large temperature gradients can be achieved on diaphragm because of its low thermal conductance and the high combustion temperature. This combustor configuration is used in a micro thermoelectric power generation chip. The output power level of the generator has been measured to be ∼3μW/thermocouple at a hydrogen flow rate of 3.1sccm.
Study on Fabrication of Microrods by Cutting Process
Authors: Jin Masahiko , Kohinata Takumi , Murakawa Masao
Published: June 2008

In this study, we examine an efficient method for fabricating microrods with high accuracy, using a cutting process. Two problems exist in the fabrication of microrods using the cutting process. The first problem is low processing accuracy due to microrod deflection resulting from the cutting force acting during the process and microrod breakage at the end of the process. The second problem is deterioration of the cut surface due to low cutting speed resulting from the small diameter of the microrod. We propose the following methods to solve these problems. For the first problem, we propose a cutting method that uses a cutting-tool path and cutting sequence to achieve a minimum cutting force acting on the microrod during the process. For the second problem, we propose a cutting method that uses ultrasonic vibration to decrease the cutting force, thereby realizing good cutting surfaces under the low-cutting-speed condition. As a result, we succeeded in the fabrication of a linear microrod with a 50 μm diameter and an aspect ratio of 100, as well as a microrod for a friction wheel with a complex stepped shape of 70 μm minimum diameter. Thus, we demonstrated the effectiveness of the proposed cutting method for microrods.
Length-Scale Dependence of Elasticity in Nanocrystalline Materials for MEMS Applications
Authors: Haque M. A. , Saif M. T. A.
Published: June 2008

Length-scale dependence of the elastic properties of thin film materials bears significance in the design of Microelectronic and Micro-electro-mechanical (MEMS) systems, which are usually desired to operate in the elastic range under different operational loading conditions. In this study, we investigate elastic properties of freestanding ultra-high purity Aluminum and Gold thin films with thickness varying from 30 to 350 nanometers. Uniaxial tension test results indicate that for truly polycrystalline films, Young’s modulus can be as low as 85% and 60% of the bulk value for Aluminum and Gold respectively with average grain size of 20 nanometers. We present, for the first time, the evidence of non-linear elasticity with total strain up to 1.0% in nanocrystalline thin films and attempt to provide fundamental understanding of the length-scale dependence of elasticity in thin films with a simple model based on inter-atomic force-distance relationships.
A Micromachined Magnetometer-Accelerometer
Authors: An Seungdo , Kim Kyung Soo , Cho Ji-Man , Park HoJoon , Hahm Ghun
Published: June 2008

A new magnetometer-accelerometer is developed with the silicon micromachining. The application areas include the cellular phones providing the third generation (3G) mobile service, and 3D game devices. The structure with a current-flowing conductor changes the vibration amplitude due to the Lorentz force. Both the magnetic field and acceleration are detected from the capacitance change and separated into each signal by the modulated frequency difference in one microstructure. A new Samsung MEMS fabrication process is developed for this sensor. The process uses a silicon-on-glass (SOG) wafer, an inverted SOG wafer, and a gold-silicon eutectic bonding for the wafer-level hermetic packaging. The test shows the equivalent noise of 1.65 mg peak-to-peak (pp) acceleration and 70 μT pp magnetic flux density. The sensor performance is enough for the 10 degree electronic display of the orientation angle for the cellular phones and portable navigators.
Electromagnetic Squeezing Microactuators Using Laterally-Driven Flexible Copper Strip
Authors: Kang Tae Goo , Cho Young-Ho , Baek O. Hyun , Moon Jae Ho
Published: June 2008

In this paper, we present the design, fabrication and testing of an electromagnetic squeezing microactuator, which generates a laterally-driven squeezing motion for application to the microinjectors. A set of electroplated flexible copper microstrip pairs is fabricated by using the thick PR micromold. In the experimental study, we measured the static response of the electromagnetic squeezing microactuators as well as the dynamic response in the vacuum, air and water environments. We also measured the pumping volume of the present electromagnetic squeezing microactuators as 20pl/cycle for DI water.
Integrated Surface Micromachining: A Mechanical Engineering Window Into Nanotechnology
Authors: Sulouff Bob
Published: June 2008

This paper examines the engineering challenges created by integrated surface micromachining, which is the combination of MEMS and electronics on the same silicon substrate. It then goes on to explore the future trends in this area from both the technical challenges as well as an applications and business perspective. The low level signals that are detectable and processed make dimensional changes in the nanometer range a common aspect of this technology. The mechanical engineer is faced with structures that have millimeter dimensions with deflections from 10 nanometers to subnanometer ranges. It is therefore possible to sense acceleration, magnetic forces, and acoustic energy as well as steer light in a fully intergrated system on a chip. The applications from a technical perspective seem endless however the need to develop both a process and a product make the time to market a significant consideration. The paper concludes by highlighting promising areas such as communications, displays, and sensing, for future development from both a technical and business perspective.
A Variable Optical Attenuator With Tunable Mirror Curvature
Authors: Lin Cheng-Hsuan , Wen Shih-Yi , Hu Chieh , Lee Hsiao-Wen , Hsu Wensyang
Published: June 2008

A novel variable optical attenuator is proposed, fabricated, and tested here. The attenuation effect is achieved by changing the curvature of a reflection mirror membrane. In order to demonstrate the proposed principle, concave mirrors with different radii are first used to confirm the attenuation effect. Then a thermal bimorph structure with membrane is used to deform the mirror membrane at different input voltages to show the variable attenuation effect. The size of the mirror membrane, which is made of low-stress Nitride (1.0 μm) with Cr/Au (0.4 μm) on the top surface, is 800 μm × 800 μm. The major two materials in bimorph actuator are low-stress Nitride and Al (1.2 μm). Two other materials, Poly-Si (0.4 μm) and SiO2 (0.5μm), act as the heating and insulation layers in the bimorph beams, respectively. The minimum insertion loss of the attenuator is found to be 0.74 –dB. The attenuation and deflections of the mirror membrane at the central part are calibrated at different input voltages. It shows that and the attenuation is more than 40 –dB at input voltage of 44 V when the central displacement of the mirror membrane is about 16 μm.
Application of MEMS to National Security Needs
Authors: Scott Marion W.
Published: June 2008

Sandia National Laboratories is a multi-program Department of Energy (DOE) National Laboratory with a broad spectrum of national security missions. Microsystem technology offers a number of possible solutions to national security needs that can be categorized in the areas of: • Remote sensing; • Point sensing; • Forensic investigation; • High consequence surety of devices and information. This paper will discuss sample applications within these areas and will identify new capabilities that will be needed to meet future mission challenges.
Integration of Single Multi-Walled Carbon Nanotube on Micro Systems
Authors: Chung Jaehyun , Lee Junghoon , Ruoff Rodney S. , Liu Wing Kam
Published: June 2008

This paper presents new techniques for depositing single multi-walled carbon nanotube (MWCNT) on metal electrodes based on micro-fabrication and an electric-field-guided assembly technique. It was demonstrated that a single MWCNT can be directionally deposited across a microscale gap guided by a biased AC electric field. The biased AC method could effectively avoid the deposition of undesirable particles, and yet maintained highly ordered deposition results. A specific AC frequency component was applied to attract only desired CNTs into a gap and a DC component was used to diminish electric field significantly when the first CNT is deposited. This method can be easily combined with other micromachining process and possibly applied to batch production.
Modeling of Unstable Regimes in a Rijke Tube
Authors: Matveev K. I. , Culick F. E. C.
Published: June 2008

In the ducts with mean flows and heat sources, excitation of acoustic eigen modes is possible when unsteady heat release is coupled with pressure perturbations. The simplest device for studying the fundamental principles of thermoacoustic instabilities in the presence of a mean flow is a Rijke tube. In this work a series of experiments was carried out to determine the conditions for the transition to instability and the non-linear characteristics of a Rijke tube, such as limit-cycle amplitudes and frequencies of the dominant mode. Sound, excited in the tube, affects the heat transfer process; that leads to modifications of the acoustic mode shapes and steady state properties. It was observed in the experiment that the thermoacoustic system possesses hysteresis. A mathematical model incorporating heat transfer, acoustics, and thermoacoustic interactions is developed for determining the transition to instability. The dominant nonlinear factor in the system, defining the limit-cycle characteristics, is the nonlinearity of the heater transfer function. Two approximate and generally applicable nonlinear models are considered, and results of the modeling are compared with the experimental data for one position of the heater. The influence of noise on the transitions between stable and unstable regimes is discussed.
Excitation by Flow Over an Obstructed Opening
Authors: Zoccola Paul J.
Published: June 2008

The effect on flow-induced cavity resonance of the presence of an obstruction, or a grid made up of regularly spaced obstructions, in the cavity opening is considered. The presence of a single obstruction or of a grid generally alters the flow so that the excitation occurs on the smaller length scale created by the obstruction. However, discussion of resonant excitation on the length scale encompassing the obstructions has not been found in the literature. For this study, measurements of cavity pressure due to flow over a cavity with obstructions or grids of varying dimensions in the opening were made. Measurements of the flow field around a single obstruction were also made. The cavity pressure measurements show that flow over an opening with a grid does result in the occurrence of classical resonant excitation at the large length scale. The frequency of the excitation and the amplitude of the response at the large length scale are reduced, depending on the dimensions of the obstruction. Flow field results show the effects that an obstruction has on the flow, including effects on the vortex convection velocity and the energy production distribution.
Study of the Acoustic Oscillations by Flows Over Cavities: Part 1 — Internal Flows
Authors: Amandole`se Xavier , He´mon Pascal , Regardin Clotilde
Published: June 2008

We present a study of acoustic oscillations induced by an internal airflow over a shallow and a deep cavity. The Kelvin-Helmholtz instability is interacting with an acoustic mode of the duct, leading to a resonance which produces a very high sound level. The influence of upstream boundary layer thickness and neck thickness is studied. Some results obtained by modifying the upstream lip shape, by crenel addition, are also given. It is also shown that the numerical simulations using a lattice-gas method give relatively good results by comparison with the experiments. Especially the resonance with the duct acoustics was qualitatively reproduced.
Thermoacoustically-Based Combustion Oscillation in a Gas Turbine: A Brief Note
Authors: Eisinger Frantisek L. , Sullivan Robert E.
Published: June 2008

Thermoacoustic combustion oscillation and vibration experienced in a gas turbine at operation is reported. The oscillation manifested itself at two distinct frequencies representing the first and second mode frequencies of the combined hot and cold (combustion chamber/burner air) Rijke type thermoacoustic model. The first mode was a lower amplitude thermoacoustically driven free Rijke mode. The higher frequency second Rijke mode coupled with the second acoustic mode of the combustion chamber resulted in high amplitude oscillation. Modifications to the burner cold air components are considered which would eliminate the oscillation. The paper will present and discuss the principal parameters which caused the oscillation and changes which would eliminate it.
SCREAM for Multi-Level Movable Structures by Inductively Coupled Plasma Process
Authors: Lin Yu-Hsin , Yin Hung-Ling , Hsu Yung-Yu , Hu Yi-Chiuen , Chou Hsiao-Yu , Yang Tsung-Hsun
Published: June 2008

A novel fabrication process to etch, to passivate, and to release single-crystal silicon structures totally in just only one process by inductively coupled plasma reactive ion etching (ICP-RIE) has been presented in this paper. Several kinds of movable actuators such as relay, comb-drive, and capacitance with thickness of 30 μm have been fabricated successfully to demonstrate this fabrication process. Here, experimental investigations about fabrication parameters to get well profile and suspension structures are performed in a STS ICP-RIE system.
Reversible Stepwise Motion by a Novel Symmetric Scratch Drive Actuator
Authors: Chen Shawn , Hsu Wensyang
Published: June 2008

A novel symmetric scratch drive actuator (SSDA) capable of two-way motion is proposed here. An analysis scheme is presented, and also can be applied to the conventional scratch drive actuator (SDA). The analysis derived here is the first to be able to relate the step increment and driving voltage with given geometrical parameters and material properties for SSDA or SDA. In order to verify the analysis, the simulation results are compared to experimental data of SDA in previous literature [1], and it shows good agreement. In the analysis of SSDA, it is found that SSDA can provide the same order of step increment with the same driving voltage, and it may move in two directions by one device.
Axiomatic Design of a Chemical Mechanical Polishing (CMP) Wafer Carrier With Zoned Pressure Control
Authors: Melvin Jason W. , Suh Nam P.
Published: June 2008

Axiomatic Design was used to develop a complete platform for chemical mechanical polishing (CMP) of silicon wafers. A functional requirement of the machine emerging from the axiomatic design process is the control of the wafer-scale polishing uniformity. Mechanisms to maintain control of the uniformity were designed, and integrated into a wafer carrier, which holds the wafer during polishing and applies normal pressure to the polishing interface. The wafer carrier is capable of controlling the pressure in four annular zones on a 200 mm wafer, as well as the pressure of the surrounding retaining ring. Initial testing of the wafer carrier indicates a successful design, offering removal non-uniformity of 1.7% after polishing 5,700 Å of SiO2 from the surface of a silicon wafer.
Fine Grinding of Silicon Wafers: Grinding Marks
Authors: Pei Z. J. , Strasbaugh Alan
Published: June 2008

In order to ensure high quality chips with high yield, the base material, semiconductor wafers (over 90% are silicon), must have superior quality. It is critically important to develop new manufacturing processes that allow silicon wafer manufacturers to produce high quality wafers at a reasonably low cost. A newly patented technology—fine grinding of etched silicon wafers—has great potential to manufacture very flat silicon wafers more cost-effectively. This paper presents an investigation of grinding marks in fine grinding. The investigation covers (1) nature of grinding marks, (2) factors that have effects on grinding marks, and (3) approaches to reduce grinding marks. Varying chuck speed during grinding operation is shown to be a very effective approach to reduce grinding marks. Conclusions from this study have direct impacts to the silicon wafer industry.
Basic NDE of Some Nano Composites
Authors: Ayorinde Emmanuel , Islam Sadikul , Mahfuz Hassan , Gibson Ronald , Deng Feizhong , Jeelani Shaikh
Published: June 2008

The influence of the nano-sized particulate or slender structures admixed into the material of regular composite structures of various architectures is being enthusiastically studied in many places across the world, but the study is yet in its infancy because there are so many aspects to be investigated. This work is basically on foam-cored structural sandwich composites, and even here there are many variables involved, for example the nano-enhancer can be introduced into the reinforcement, the matrix or the foam. The focus of the work is on some possible effects of the presence of the nano-materials on the NDE process in testing these composites. Acoustic emission is emphasized in these studies, as it appears to hold promise for non-destructively testing materials of this nature, and basic and standard mechanical test methods are employed.
3-D Woven Composites Instrumented With EFPI Fiber Optic Sensors
Authors: Bogdanovich Alexander , Wigent Donald , Whitney Thomas J. , Clark Paul A.
Published: June 2008

A novel approach to continuous health monitoring of polymeric composite materials and structural elements using embedded Extrinsic Fabry-Perot Interferometers (EFPI) is proposed and validated. The proof of concept includes several consecutive steps. First, it is verified that simple optical wave guides survived a regular 3-D weaving process. Then EFPI sensor assemblies are manually incorporated into the preforms and it is verified that they are functional. Next step is resin infusion of instrumented preforms using VARTM method, followed by investigation of possible mechanical damage to sensor leads. Finally, test specimens are fabricated, and four-point bending tests are performed. The internal strain monitoring results provided by the embedded fiber optic sensors are compared to the data from surface foil gages. The developed approach validates, particularly, the possibility of continuous through-thickness strain monitoring, which is crucial for composite bonded and bolted joints, components with holes, openings, stiffeners, and other cases of high strain gradients.
Active Wave Modulation for Bond Evaluation
Authors: Wu Hwai-Chung
Published: June 2008

Many recent studies have indicated that externally bonded Fiber Reinforced Plastic (FRP) composite sheets can be used effectively to strengthen concrete structures. Composite action suggests that the individual parts of a composite work together as one. Stresses must be transferred from one constituent to the other through some interface. If there is little or no bond at the interface then there is little or no transfer of stress and therefore poor composite action. In this study, we intend to develop a NDE tool for evaluating such interfacial bond conditions. Attention is placed on an innovative active modulation approach, Nonlinear Wave Modulation Spectroscopy. In this procedure, a probe wave will be passed through the system. Simultaneously, a second, modulating wave will be applied to the system to agitate the state of damage in the materials. The resulting frequency modulations will be analyzed, and will be correlated to the presence of the interfacial flaws between a FRP thin sheet and concrete substrate.
Design and Analysis of a Heat Conduction-Based Continuous Flow Polymerase Chain Reaction System
Authors: Li Shifeng , Chen Shaochen
Published: June 2008

Miniaturized ploymerase chain reaction (PCR) systems have attracted increasing interest in medicine and biology for its reduced sample volume and faster thermal cycling compared to conventional PCR device. The thermal cycling in a PCR device involves three temperatures: 95°C to 90°C for DNA denaturation, 50°C to 65°C for hybridization, and 72°C to 77°C for replication. In this work, a completely new concept of obtaining a temperature zone is presented, i.e., some temperature zone is not created by direct micro-heater heating, by natural heat conduction. Finite element method (FEM) is employed to analyze the temperature distribution in the new PCR designs. Three different designs were compared: (1) three heaters, (2) one heater, and (3) two heaters. For the three-heater design, the FEM simulation shows that large space must be reserved between heaters in order to avoid thermal cross-talking maintain a relatively uniform heating zone. For the single heater design, we have only one heater to reach 92 °C. Due to heat conduction, the temperature reduces gradually along the length of the device. We can setup the hybridization and replication zones at certain locations (along the direction of heat conduction) without using a micro-heater. The PCR device based on this design is easy to fabricate. But FEM simulation shows that the temperature gradient is about 8°C/ram. To overcome this “rapid” temperature gradient problem, we proposed to use two heaters. This design involves two heaters both sides. One heater is controlled to be 92°C for denaturation, and on the other end we use another heater set to 75°C for replication. The hybridization temperature (50 °C ∼ 65°C) is obtained from thermal conduction. In PCR operation, the time ratio for denaturation: hybridization: replication is about 4:4:9. For a continuous flow with a width of 80 μm and a depth of 30 μm and flow ranging from 5 nl/s to 80 nl/s, the 20-cycle PCR can be fabricated within an area of 56 mm × 28 mm area, which is smaller than previous design (Kopp et al., 1998). The length of the microchannel is about 0.6 m, which yields a cycling time from 22 seconds to 6 minutes.
Passive Control of the Two-Dimensional Jet Using a Rectangular Notch
Authors: Fujita Shigetaka , Harima Takashi , Osaka Hideo
Published: June 2008

The mean and turbulent flow properties of turbulent jet issuing from a quasi two-dimensional (2-D) nozzle with a rectangular notch (aspect ratio: AR=12.5) perpendicular to the two-dimensional nozzle at the midspan, have been measured. The exit Reynolds number was kept constant 13000. The aim of this study is to examine the effects of the rectangular notch on the mean and turbulent flowfields of the two-dimensional jet, and to clarify a possibility of a passive control of the two-dimensional jet using a rectangular notch. From the experiments, it was revealed that the potential core region existed until the section of x/d=25. In the upstream region, the entrainment rate was smaller than that of the two-dimensional jet due to the inward secondary flow on the y and z axes. Furthermore, the streamwise development of the turbulent intensity was delayed.
Process and Properties Control in Laser Aided Direct Metal/Materials Deposition Process
Authors: Choi J.
Published: June 2008

Laser aided direct metal/material deposition (DMD) process, one of the technologies based on laser cladding, has demonstrated the ability to make a metal component directly from a 3-D CAD model. DMD process is achieved with a laser system combined with a NC machine tool or laser-robot system. Making metallic parts directly, designer can reduce unnecessary steps such as mock-up and molding. In the sense, DMD process is rather a rapid production technique than a rapid prototyping process. With continued advancement, DMD process, one of the leading solid freeform fabrication techniques, has demonstrated the ability to make a metal part with heterogeneous components directly from a CAD model. One unique advantage of the process is that building different metallic parts in same object can be achieved alternating metal powders. The advantage gives designers better quality of products than others can offer. Another attractive point is that some features such as cooling channel, heat sinks, sensors, fibers, and even hard phases for composites can be embedded during the process. This paper summarizes the fundamentals of the process, process control and influence of process parameters, and reports some examples produced utilizing the technique with the characteristics of fabricated parts.
A Perturbation Technique for Flow-Induced Vibration Control
Authors: Cheng L. , Zhou Y. , Zhang M. M.
Published: June 2008

This paper presents a novel technique to perturb the vortex shedding from a bluff body and subsequently suppress the flow-induced structural vibration. The essence of the technique is to create a local perturbation on the surface of a bluff body using piezoelectric actuators. Experiments were carried out in a wind tunnel. A square cylinder of a height h, flexibly supported on springs at both ends, was allowed to vibrate only in the lift direction. Three actuators were embedded underneath one side, parallel to the flow, of the cylinder. They were simultaneously activated by a sinusoidal wave, thus causing the cylinder surface to oscillate. The structural displacement Y and flow velocity u were simultaneously measured using a laser vibrometer and a single hot-wire, respectively. When the vortex shedding frequency ƒs synchronized with the natural frequency of the dynamic system, Y was estimated to be about 0.08h. This displacement collapsed to 25% once the actuators were excited at a normalized frequency ƒh/U∞ = 0.1 (U∞ is the free-stream velocity) and amplitude of 0.028h. The laser-illuminated flow visualization captured drastically weakened vortices shed from the cylinder. Spectral analysis of the Y and u signals points to the fact that the imposed perturbation has altered the spectral phase at ƒs between fluid excitation and structural vibration from 0 to π, and meanwhile decreased the spectral coherence at ƒs from 0.65 to 0.15. It is expected that the perturbation technique presently investigated will have an important role to play in the flow-induced vibration control, especially with the active control element assimilated into the system.
Spatial Impact of a Slender Beam
Authors: Barbulescu Horatiu , Marghitu Dan B. , Vaidya Uday
Published: June 2008

In this paper, the dynamics of the spatial impact of a slender beam is analyzed. The equations of motion are calculated using Kane’s impact method. The generalized momentum and generalized impulse of the beam are considered to find the equations of motion of the beam. The frictional phenomenon at the contact point is analyzed. For the case of impact without slipping, it is used the assumption that the tangential component of the velocity of separation is null. In the case with slipping, the tangential impulse (at the plane of impact) is computed. The sliding direction after impact is calculated. A simulation of the impact of beam with a surface is developed and the velocity of separation, force of impact and kinetic energy of the beam after impact are studied for different incident angles of the beam. The incident angle is varied from 0° to 57°. The results are function of the incident angle of impact. The results can be used to calculate the coefficient of restitution and friction for composite materials.
Pneumatically Controlled Pallet Conveying and Accumulation System
Authors: Beikmann Mel , Kuecker Jim
Published: June 2008

First In / First Out (FIFO) accumulating storage systems combine high-density storage with automatic material handling. A traditional FIFO storage system is a flow-through rack which uses gravity to move the pallet from the load end to the unload end. High-density storage installations require a significant difference in height between the load end and the unload end which results in a loss of available storage space. Rack configuration in terms of slope, brake configuration, and roller density is inflexible and are a function of pallet type, size, and weight. Changes in pallet characteristics cannot be easily accommodated by traditional gravity flow storage rack systems. Alternate FIFO storage systems are available that do not use gravity but rather use rollers on a horizontal reciprocating frame with directional flippers to ensure that the load indexes from the load end to the unload end. The limitations of these existing systems have prompted the development of alternative FIFO storage system. This paper details an innovative FIFO storage/handling system and the collaborative effort between a university and private industry to develop this product.
Distributed Palletizing Using a Cam Driven Multi Track Material Handling Device
Authors: Derby Stephen J. , McFadden John
Published: June 2008

A novel palletizing/material handling device has been created. This novel design was developed by assessing the needs of many industrial companies. This device trades the unlimited flexibility and position addressibility of standard servo driven robots and material handling machines for a limited set of palletizing locations, by use of a multi track cam plate. The resulting combinations of reduced complexity degrees of freedom result in a less expensive and more marketable product.
Material Handling Throughput Using a Track Based Multihead Robot
Authors: Derby Stephen J. , McFadden John
Published: June 2008

A novel closed loop track based multi-head robot has been developed to increase material handing throughput. This robot allows for waves of robot heads to move materials in the working path by eliminating the traditional return path. Programmable clutching of a constant moving drive chain supplies the source of motion around the loop. This paper discusses the design and impact of such a system configuration, and looks at the required distributed control system.
Configuration-Space Searching and Optimizing Tool Orientations for 5-Axis Machining
Authors: Jun Cha-Soo , Lee Yuan-Shin , Cha Kyungduck
Published: June 2008

This paper presents a methodology and algorithms of optimizing and smoothing the tool orientation control for 5-axis sculptured surface machining. A searching method in the machining configuration space (C-space) is proposed to find the optimal tool orientation by considering the local gouging, rear gouging and global tool collision in machining. Based on the machined surface error analysis, a boundary search method is developed first to find a set of feasible tool orientations in the C-space to eliminate gouging and collision. By using the minimum cusp height as the objective function, we first determine the locally optimal tool orientation in the C-space to minimize the machined surface error. Considering the adjacent part geometry and the alternative feasible tool orientations in the C-space, tool orientations are then globally optimized and smoothed to minimize the dramatic change of tool orientation during machining. The developed method can be used to automate the planning and programming of tool path generation for high performance 5-axis sculptured surface machining. Computer implementation and examples are also provided in the paper.
Some Theory and Algorithms Pertaining to Machinability and Visibility
Authors: Balasubramaniam Mahadevan , Kim Taejung , Sarma Sanjay
Published: June 2008

In previous work, we and others have developed visibility-based tool path generation schemes. Almost all previous research implicitly assumes that all visible parts are machinable. Though usually true practice, this assumption hides several subtleties inherent to the geometry of the machining process. Here, we define machinability in a stricter sense, as a generalization of the robotic path planning problem. Then, we define various “tight” necessary conditions for strict machinability, and show the connections between these conditions. After demonstrating the richness of the information contained in visibility, we show how to compute visibility effectively. Visible directions constitute an approximate feasible configuration space of a cutting tool. We also address questions pertaining to the topological connectivity of the feasible space. The theoretical results of this paper lay down a firmer foundation of machining path planning.
A Curvilinear Tool-Path Method for Pocket Machining
Authors: Bieterman Michael B. , Sandstrom Donald R.
Published: June 2008

A novel curvilinear tool-path generation method is described for planar milling of pockets. The method uses the solution of an elliptic partial differential equation boundary value problem defined on a pocket region. This mathematical function helps morph a smooth low-curvature spiral path in a pocket interior to one that conforms to the pocket boundary. This morphing leads to substantial reductions of tool wear in cutting hard metals and of machining time in cutting all metals, as experiments described here show. A variable feed-rate optimization procedure is also described. This procedure incorporates path, tool engagement, and machine constraints and can be applied to maximize machine performance for any tool path.
Active Control of Sound Radiation Into Enclosures Using Structural Error Sensors
Authors: Li D. S. , Cheng L. , Gosselin C. M.
Published: June 2008

Active control of vibration and sound inside a structure-surrounded enclosure leads to many applications such as noise control inside vehicle cabins. Despite the extensive research carried out in the last two decades, ANVC technology is still in its infancy and has not yet been introduced massively in practical engineering applications. One of the problems to be resolved is that most of presently used techniques require the use of microphones inside the cavity, which is not practical in many situations. In addition, due to the coupling between the vibrating structure and the confined enclosure, demand for more robust control strategy is apparent. This paper tackles the aforementioned problem using a benchmark system in which only PVDF (Polymer polyvinylidene fluoride) sensors are used on the structural surface. A new method based on genetic algorithms is developed for sensor design. This design process ensures a proper consideration of the acoustic energy in the enclosure without the direct use of acoustic sensors inside the cavity. Roughly speaking, the sensor is designed to capture the most radiating motion of the structure via an automatic optimization process. In the proposed method, Genetic Algorithms and the least quadratic square optimal theory are organically combined together. For each configuration of error sensors, the amplitude of control forces, which can either be point forces or excitation generated by piezoceramic actuators, is first determined by minimizing the sum of the squared outputs of error sensors using the least quadratic square optimal theory. Then with the optimal amplitude of control forces, the acoustic potential energy of the sound cavity is computed and used as the evaluation criteria in the evolution process. Using Genetic Algorithms, the optimal configuration of the error sensors can be determined. A cylindrical shell with an internal floor partition is used as an example to illustrate the effectiveness of the proposed approach. To increase the computational efficiency, the structural surface is assumed to be covered with strip-typed PVDF sensors along both the circumferential and longitudinal directions. Both numerical and experimental results show the great effectiveness of the proposed GA-based design method. The sound reduction is achieved not only at the design frequency but also at most frequencies in the low frequency range. The proposed method demonstrates great merits in sensor design for complex structures.
Efficient NC Machining Using Off-Line Optimized Feedrates and On-Line Adaptive Control
Authors: Richards N. D. , Fussell B. K. , Jerard R. B.
Published: June 2008

A combination of off-line feedrate optimization and online adaptive force control is used to maintain a reference peak force during end milling for safe, accurate, and efficient machining. Feedrate optimization algorithms use geometry and force models to calculate feedrates for each tool move, based on a reference peak force. The adaptive controller adjusts the feedrate during machining to maintain the reference peak force. It is the combination of these methods that yields accurate force control, unobtainable with either method by itself. Adaptive control alone is inadequate to handle significant transient cut conditions because of the slow system response time. Optimization algorithms are subject to modeling errors that can lead to significant force errors when cutting. Design parameters for the adaptive controllers are selected using an experimentally validated machining process model. The adaptive controllers are implemented on an open architecture controlled (OAC) 3-axis NC milling machine, and evaluated using three experimental test cases: a sine cut, a prismatic cut, and a corner cut. Feedrates for each cut are first optimized off-line, then used in actual machining with and without controller action. Experimental results demonstrate the ability of the integrated system to effectively regulate peak forces for cutting conditions commonly encountered in end milling operations. In particular, a variable geometry sine cut that initiates chatter shows the advantages of the combined system.
Active Control of Flexible Structures Submitted to Incompressible Flows
Authors: Machado C. C. , De Bortoli A. L. , Gomes S. C. P.
Published: June 2008

This work presents a survey on the control law development to actively attenuate the vibrations of a flexible structure submitted to fluid flow. Firstly, a robust controller with LQG/LTR approach was developed. Numerical tests were carried out being robustness characteristics to flow induced vibration and to noise rejection verified, for the case of equal nominal and real plants. The same robustness was not verified, when parametric variations were introduced. Therefore, another controller, based on regulator and filter pole placement approach, was developed where the direct loop obeys stability and performance robustness criterions, allowing to obtain good numerical results, even in the presence of significant parametric variations.
Analytical Solution of the Flow Along Parallel Microchannels Separated by a Porous Membrane
Authors: Lee Changgu , Fre´chette Luc G.
Published: June 2008

This papers presents the analytical solution of the flow distribution along a porous membrane which is between two parallel microchannels, a configuration of increasing importance in microsystems for DNA sequencing, catalytic chemistry, and in micro heat exchangers. The modeling approach presented in the paper is inspired from thin film lubrication theory and would be applicable for a wide range of low Reynolds number, pressure-driven microfluidic configurations.
Parametric Design of Fixed-Geometry Microvalves: The Tesser Valve
Authors: Forster Fred K. , Williams Brian E.
Published: June 2008

A parametric description of two existing types of planar fixed-geometry micropump valves, the nozzle-diffuser and the Tesla-type, can be accomplished with surprisingly few parameters. The planform shape for the former requires only four parameters and the latter only five. Following this observation, a new valve type, the Tesser valve, was created having features of both the Tesla-type and nozzle-diffuser that required only two additional parameters, for a total of seven. Our overall goal is to utilize formal optimization techniques and computational fluid dynamics (CFD) with a experimental testing program to achieve valve efficiency that would be very difficult if not impossible to determine empirically. In this study we utilized two-dimensional computations that revealed a strong dependence of diodicity on Reynolds number in the range common for current micropump designs. The study also showed that the Tesser valve was superior at low Reynolds number 10 < Re < 100, and the Tesla-type valve superior at higher Reynolds number 100 < Re < 2000.