bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Conical Indenter Shape on TBC Interfacial Toughness Measurements
Authors: Ma Q. , Beuth J. L. , Meier G. H. , Pettit F. S.
Published: May 2009

Thermal barrier coatings (TBCs) are thin ceramic coatings used to insulate gas turbine hot section components. The degradation of interfacial fracture toughness between the coating and the metallic substrate is a key concern for TBC systems. Previous research by the authors has explored the use of conical (Brale) indentation to measure the interfacial fracture toughness of electron beam physical vapor deposition (EB-PVD) TBCs. However, indentation using a standard 120° Brale indenter can fail to yield an ideal debond size for accurate measurement for poorly adhered coatings subjected to long-term thermal exposures, or for as-processed coatings that are well-adhered to the metallic substrate. These limitations of existing conical indentation tests have lead to the study of different shapes of indenters to obtain optimal debond sizes. In this paper, the differences in measuring the interfacial fracture toughness in thermal barrier coating systems due to indentation by rigid cones with various tip angles, namely, 60°, 90°, 120°, and 150° are addressed. Interfacial stress intensity factor distributions, i.e., curves of the interfacial stress intensity factor (K) vs. normalized radial distance (R/a), are obtained through numerical simulations coupled with thin film fracture mechanics relations. Results from experimental studies on an exposed EB-PVD TBC specimen are presented. The goal of this work is to obtain larger debond sizes for high toughness specimens and smaller debond sizes for low toughness specimens, while maintaining an adequate indentation depth.
Effects of Heat Treatment on Thermal Conductivity of Highly Porous Copper/Silver Systems
Authors: Murtha Brian A. , Kulkarni Anil K. , Singh Jogender
Published: May 2009

The phenomenon of sintering has a significant impact on the thermal conductivity of a highly porous material. Particle diffusion greatly reduces the number of grain boundaries that are normally present in porous materials. In turn, fewer grain boundaries imply fewer sites for phonon scattering during conductive heat transfer. Therefore, during heat treatment of a highly porous material, particle diffusion accounts for a changing thermal conductivity. This occurs with no bulk densificiation of the material. In fact, SEM images show that the microstructure of a porous material changes from many individual particles with small pores between the particles to diffused particles with large pores in between large chunks of material. To model such a phenomenon, standard equations were scaled with unitless weighting functions to account for variable microstructures during heating. By weighting standard equations, the effects of microstructure could be more accurately described as a function of porosity and time.
A New Method for Sensor Degradation Detection, Isolation and Compensation in Linear Systems
Authors: Jiang Li , Djurdjanovic Dragan , Ni Jun
Published: May 2009

The performance of machines and equipment degrades as a result of aging and wear. This decreases performance reliability and increases the potential for faults and failures. To ensure proper functionality of complex systems, advanced technologies for performance diagnosis and control are being incorporated into engineering designs, which requires an ever-increasing number of sensors and measurement devices. Nevertheless, a sensor, just as any other dynamic system, degrades and fails. A faulty sensor may cause process performance degradation, process shut down, or even a fatal accident because it is no longer able to deliver accurate information about the monitored system. Therefore, it is essential to assess sensor performance to ensure system reliability. In this paper, a method is proposed to detect, isolate, and compensate sensor degradation. The numerical algorithm for subspace state space system identification is used to track the changes of the time constants and gains of the sensor and the monitored system. Without imposing requirements for redundant sensors and measurement devices, this method utilizes the fact that sensor readings depict dynamic characteristics of the sensors as well as those of the monitored system. The newly proposed method is verified in angular sensor degradation detection using high-fidelity simulations of an automotive electronic throttle system.
Process Optimization for Releasing of MEMS/NEMS Devices and Coating of Anti-Stiction SAM
Authors: Popat Ajay M. , O’Neal Chad B.
Published: May 2009

Micro electromechanical systems (MEMS) or nano electromechanical systems (NEMS) have higher surface-to-volume ratio, and hence they are susceptible to unintentional adhesion and subsequent failure to function. Although there are many classes of liquid phase anti-stiction coatings for silicon MEMS / NEMS, alkene based monolayer films with hydrogen terminated silicon coatings were chosen since this process has some important advantages over other SAM processes, such as fluorine or chlorine based films. An engineering challenge of scaling up liquid-phase anti-stiction and release processes is met by designing and fabricating a semi-automated and portable MEMS release station, which enables 20 – 40 dice or a wafer up to 100 mm in diameter to be released and coated at one time. This optimized release and coating process reduces processing time and chemical processing volume drastically compared to releasing and coating dice individually. The simultaneous processing of multiple dice was enabled through an inert FEP - Teflon dice-holder-clamp. The clamp is adaptable to hold varied sizes of dice with no lost die. The successful elimination of the secondary HF rinse for hydrogen termination has resulted in additional saving of expensive HF, additional saving of process time, and reduced exposure to the dangerous chemical - HF. The increase in hydrophobicity resulted from the optimized release and SAM coating process was confirmed through the average increase, from 68.2° to 109.3°, in water contact angle of SAM coated Si (100). The increase in the average surface roughness from 0.4 nm for source procedure to ∼ 4 nm using optimized release and SAM coating process became evident through the AFM scanned images. The increase in hydrophobicity and surface roughness using the optimized release and SAM coating process play vital roles in preventing the stiction of MEMS / NEMS devices. This scalable process has good yield and is easier to use and train personnel than a typical SAM coating process.
Two-Phase Flow Regime Modeling and Pressure Drop Behavior
Authors: McDermott Braden A. , Shedd Timothy A.
Published: May 2009

A unique horizontal two-phase flow facility has been fabricated in an effort to understand the dynamics of two-phase flow in small pipes. The fluid chosen for study is the low pressure refrigerant R-123. In this work, two-phase pressure drop data were obtained for two-phase flow of refrigerant R-123 in a 17.0 mm inner diameter tube over a wide range of quality, from .015–1, and mass fluxes that were varied from 50 kg m−2 s−1 to 550 kg m−2 s−1. These data have been compared, as a whole and by regime, against four frequently-used two-phase frictional pressure drop prediction correlations. Flow regimes were visualized using a quartz tube at the end of the test section over this wide range of conditions, which ranged from stratified to annular flow. Each condition was mapped on the Mandhane, Taitel-Dukler, and Kattan-Favrat-Thome flow regime maps in an attempt to understand the applicability of each. Some discrepancies exist between the current data and the published flow maps, and recommendations are made based on these observations. The pressure drop data appear to be dependent upon the flow regime, suggesting that an entire set of correlations is necessary based upon flow regime for accurate prediction of pressure drop.
Entropy and Efficiency in Laser Cooling of Solids
Authors: Ruan Xiulin , Rand Stephen C. , Kaviany Massoud
Published: May 2009

The thermodynamics of laser cooling of solids is analyzed. Using the general theory of radiation entropy, the important roles of the optical frequency and the photon distribution function in determining the radiation entropy are identified. The usefulness of a narrowband approximation is established for a wide range of radiant sources. This approximation is then applied to compare the entropies of different light sources, including blackbody radiation, lasers, fluorescence, and the emerging class of random lasers. Based on these results, the Carnot efficiency for laser cooling of solids is determined, for emission fields with various entropy characteristics. It is shown that fluorescent emission is the most efficient form of the radiated field for laser cooling of solids, and cooling schemes based on any stimulated emission process (including random laser action) are inherently less efficient. The influence of luminescence quantum yield on cooling is also considered.
High-Performance Impingement-Based Ultracompact Heat Exchanger
Authors: Rivera-Hernandex Yaixa L. , Shedd Timothy A.
Published: May 2009

Significant advances have been made in compact liquid-liquid heat exchangers in the recent past, such as the brazed plate heat exchanger with enhanced plate geometries. However, additional improvements in heat exchanger performance may be realized by incorporating impinging jet flow rather than flow parallel to the heat exchange surface. It has been recognized for some time that highly efficient heat transfer over large areas can be attained using impinging jets with nearby drains, but no design model is available for this configuration. This paper presents a relatively simple theory for the heat transfer performance of jet-drain arrays based on the concept of transient heat transfer to the liquid. This theory is verified by comparison to experimental data. Next, the design and implementation of a liquid-liquid heat exchanger based on jet-drain arrays is presented and the performance of this novel device is directly compared with that of a brazed-plate heat exchanger. In addition, computational fluid dynamics simulations are used to design an enhanced impingement plate that virtually eliminates interactions between neighboring jets, further improving performance. Using the theory developed in this paper, very high performance compact liquid-liquid heat exchangers can be designed with relatively large orifices (approx. 1 mm), allowing for low pressure loss and the ability to pass a significant amount of solids through without clogging.
Characterization of (La0.9Sr0.1)0.95Cr0.85Mg0.10Ni0.05O3−δ Ceramics for Perovskite Related Membrane Reactor
Authors: Yarmolenko Sergey , Gordon Kristofer , Hancock Brandon , Kharton Vladislav , Sankar Jag
Published: May 2009

(La0.9Sr0.1)0.95Cr0.85Mg0.10Ni0.05O3 (LSCMN) ceramics sintered at temperatures 1100–1700°C in air were characterized using powder x-ray diffraction, field emission scanning electron microscopy coupled with energy dispersive x-ray spectroscopy, transmission electron microscopy, differential scanning calorimetry, and inductively-coupled plasma spectroscopic analysis. Pervoskite ceramics with the highest density (porosity between 2–5%) were sintered at 1650°C for 24 hours. Secondary phases at a level of 3–5% porousity have been detected in the LSCMN initial powder received and sintered samples. LSCMN initial powder and ceramics exist in orthorhombic phase at room temperature and exhibits a first order phase transition into rhombohedral phase in the temperature range 70–95°C. Temperature of phase transition depends on grain size. Hardness and fracture toughness of LSCMN were studied by nanoindentation and microindentation methods. At low indentation depths hardness values depend significantly on the number of grains effected by the indent and crack formation. Indentation size effect was quantified in terms of Nix-Feng and power-low models. At high loads the apparent hardness is almost two times less than hardness of LSCMN monocrystalls.
Acoustic Emission Monitoring for Rolling Contact Fatigue Damage of Machined Components by Hard Turning vs. Grinding
Authors: Warren A. W. , Guo Y. B.
Published: May 2009

The fundamental knowledge of fatigue damage mechanism is necessary for understanding manufacturing process effects. However, the artificial defects on the test samples in traditional fatigue tests will change the surface integrity and therefore may not reflect the nature of fatigue damage. This paper studies the fatigue damage resulting from real-life rolling contact tests and finite element analysis of AISI 52100 steel and identifies the possible mechanisms for fatigue failure in the presence of process induced surface integrity. Rolling contact fatigue damage was real-time monitored using an acoustic emission (AE) sensor. Surface and subsurface fatigue damage of the samples was then characterized using optical and scanning electron microscopy (SEM) and surface profiling. The results suggest that shear stress induced Mode II crack is the dominant fatigue mechanism. Two types of subsurface cracks were observed: main cracks that propagate parallel to the surface due to subsurface shear stress induced fracture/debonding of inclusions or second phase particles. Shear stress induced surface cracks propagate at shallow angles (∼35°) from the surface. Branching cracks eventually form and connect the main crack to surface. The formation of main cracks and surface cracks may be parallel processes, and spalling occurs as a combined effect of the main, surface, and branching cracks. The relationship between AE signals and fatigue damage was been established.
Finite Element Modeling of Random Multiphase Materials for Micromachining
Authors: Guo Y. B. , Anurag S.
Published: May 2009

Compared with lithographic techniques, mechanical micromachining is a potential competitive process for fabricating 3D micro/meso components or macro parts with micro-features from diverse materials at high accuracy, efficiency, and low costs, but the size effect induced by the comparable size of microstructures, cutting edge radius, and depth-of-cut results in a plowing dominated process. A methodology to incorporate model random microstructure in finite element analysis (FEA) of micromachining multiphase materials has been developed to understand the plowing, tribological, and heat transfer mechanisms. An internal state variable plasticity model has been developed to model the dynamic mechanical behavior including the effect of randomly distributed microstructure, materials damage and evolution. The simulated process variables including chip morphology, forces, and temperatures agree well with the observed experimental phenomena. The simulation recovers the shearing-plowing transition and increased specific energy in micromachining.
Design and Analysis of a MEMS Based Auto-Focusing System
Authors: Yeh Wu-Feng , Wang Junlan
Published: May 2009

This paper presents the design and analysis of a novel MEMS (Micro-Electro-Mechanical System) based auto-focusing system. By combining a folded in-plane optical path design and MEMS microfabricated optical components and comb drive actuator, the auto-focusing function is achieved in a compact system with continuously adjustable imaging distances. Theoretical analysis and numerical simulation validated the feasibility of the design. The auto-focusing system presented in this work is applicable to a wide range of technological fields where high resolution imaging is desired while the space is limited.
Fabrication of ITO Nanofibers as Gas Sensor
Authors: Xu Shiyou , Shi Yong
Published: May 2009

This paper presents the fabrication of ITO nanofibers as gas sensor. ITO nanofibers are fabricated by electrospinning process. Sensors based on ITO nanofibers were prepared on Si substrate and silver paste was used as electrode. The morphology and crystal structure of ITO nanofibers were studied by SEM and XRD, respectively. The optimal working temperature and sensitivity of ITO nanofiber sensors were investigated. The sensitivity of ITO nanofiber sensor has been found to increase to a peak of 9.8 at 160°C for 50 ppm NO2, which suggests that ITO nanofibers sensor provides significantly better sensitivity for NO2 at lower temperature.
Managing New Technologies in Conceptual Engineering Design, Demonstrated on Innovative Positive Displacement Device
Authors: Roser H. M. , Dartnall W. J.
Published: May 2009

In this work, a simple method is presented, assisting engineering designers in dealing with innovative technologies during the conceptual phase of engineering design. The technique emphasises on determining Critical Design Issues, as well as evaluating new technologies early on in order to define a Critical Design Path. Since time and budget constraints often demand prompt design decisions, a systematic, easy-to-follow concept analysis and evaluation framework is introduced, allowing engineers to quickly identify critical design issues. The proposed method is demonstrated using the conceptual development of an innovative positive displacement device as a case study. The study indicates that, particularly in absence of essential knowledge within early development stages, experimental design can provide a cost effective method of identifying potential design problems, and thus, reducing design iterations, development time and risk, as long as a suitable design process is also in place. The evaluation of potential design solutions can be achieved by conceptual prototypes, which may represent a specific critical technology, or embody initial ideas to quickly gain knowledge that is crucial for the development of new design concepts. This allows the designer to reduce intuition and guesswork, whilst detecting unanticipated effects and phenomena, delivering deeper insight and communicating ideas. The method proved to be a significant tool for rapid and goal-oriented conceptual design. Through the proliferation of recent prototyping technologies, along with a reduction of design iterations, the concepts could be developed and verified on a low budget over a short development time.
Numerical Analysis of Cold Injury of Skin in Cryogen Spray Cooling for Dermatologic Laser Surgery
Authors: Li Dong , He Ya-Ling , Wang Guo-Xiang , Xiao Jie , Liu Ying-Wen
Published: May 2009

In laser dermatologic surgery, cryogen spray cooling (CSC) is used to avoid laith damage such as scars from skin burning due to the melanin absorption of the laser beam. As the cryogen is fully atomized from the nozzle, evaporation of the droplets may quickly drop the cryogen temperature below −60 °C, depending on the spray distance from the nozzle. Such a low temperature is potential to cold injury for skin. Therefore, spray process should be accurately controlled during clinical practice to achieve sufficient protection and to avoid cold injury. This study presents a numerical analysis of cold injury of skin in cryogen spray cooling for dermatologic laser surgery. The model for cryogen spray cooling of skin, developed early, is extended to include the freezing of skin cells. The model predictions include the movement of the lethal isothermals. The severity of cold injury is then quantified under various clinical conditions. The effect of initial temperature and the spurt duration on possible cold injury of skin are also investigated.
Micro/Nanoscale Structure Fabrication by Direct Nanoimprinting of Metallic and Semiconducting Nanoparticles
Authors: Park Inkyu , Ko Seung H. , Pan Heng , Pisano Albert P. , Grigoropoulos Costas P.
Published: May 2009

In this paper, we present our recent development of direct nanoimprinting of metal and semiconductor nanoparticles for a simple but high-throughput fabrication of micro/nanoscale structures. Nanoparticle suspension with self-assembled-monolayer (SAM) protected-nanoparticles (Au, Ag, and CdSe-ZnS core-shell quantum dots) suspended in alpha-terpineol carrier solvent are used as solutions for direct nanoimprinting. Polydimethylsiloxane (PDMS)-based soft imprinting molds with micro/nanoscale features are used. Process and material flexibility enable a very low temperature (80°C) and low pressure (5psi) nanoimprinting process and results in superfine features from micrometers down to ∼100nm resolutions. We will show the geometrical and electrical characterization of nanoimprinted structures and demonstrate working electronic components such as resistors or organic field effect transistors (OFET).
Fuzzy Condition Monitoring System for Aviation Gas Turbine Engines
Authors: Abdullayev P. S. , Pashayev A. M. , Sadiqov R. A. , Mirzoyev A. J.
Published: May 2009

In this paper is shown the efficiency of the new Soft Computing technology application at different diagnosing stages of aviation gas turbine engine (GTE) technical condition with using Fuzzy Logic and Neural Networks methods, when the flight information has property of a fuzzy, limitation and uncertainty. On the fuzzy statistical data basis and with high accuracy is made the training of Fuzzy Multiple Linear and Non-Linear models (Fuzzy Regression Equations). Thus for GTE technical condition more adequate model making are analysed dynamics of skewness and kurtosis coefficients’ changes. Researches of skewness and kurtosis coefficients values’ changes show that, distributions of GTE work parameters have fuzzy character. Hence consideration of fuzzy skewness and kurtosis coefficients is expedient. Investigation of the basic characteristics changes’ dynamics of GTE work parameters allows to draw conclusion on necessity of the Fuzzy Statistical Analysis at preliminary identification of the engines’ technical condition. Researches of correlation coefficients values’ changes shows also on their fuzzy character. Therefore for models choice the application of the Fuzzy Correlation Analysis results is offered. For checking of models adequacy is considered the Fuzzy Multiple Correlation Coefficient of Fuzzy Multiple Regression. With a view of completeness of GTE technical condition diagnosing in this paper are considered Fuzzy Thermodynamic Models. As output parameter of these models the outlet gas temperature of gas turbine (turbine exhaust gas temperature -EGT) expediency is considered. In view of limitation of controllable parameters’ structure are used also semiempirical models. The developed GTE condition monitoring system provides stage-by-stage estimation of engine technical conditions. As application of the given technique the estimation of the new operating aviation engine temperature condition was made.
Effect of Nano-Particles on Cellular Structure of Foamed PP-HDPE Blend Using Supercritical Fluid
Authors: Huang Han-Xiong , Sun Xiao-Hui , Wang Jian-Kang
Published: May 2009

Microcellular foaming of general polypropylene (PP) is a hot subject, but there are some difficulties in its foaming due to its low melt strength, narrow foaming temperature window, and so on. This work attempted to the improvement of PP microcellular foaming by adding nano-montmorillonite and nano-calcium carbonate into PP-high-density polyethylene (HDPE) blend. The nanocomposites were prepared using a twin-screw extruder. The foaming was carried out by a batch process with supercritical carbon dioxide as a blowing agent. Microstructure of the nanocomposites was examined using transmission electron microscopy. The cellular structure of foams was examined using a scanning electron microscope. The effects of nano-particle concentration and type on the cellular structure, cell density, cell diameter, and sample density were investigated. The results showed that the main factor controlling the cellular structure of foamed nanocomposites is the distribution of nano-particles.
Development of a Blast and Fragment Model for Simulating Land Explosives
Authors: Jiang Dongying , Liu Yuanyuan , Ma Zheng-Dong , Raju Basavaraju
Published: May 2009

A numerical simulation model was proposed for predicting blast loading and soil fragmentation on composite structures against land explosives. In the proposed landmine-soil interaction model, both blast overpressure and soil debris/explosive fragment movements can be predicted using an approach that decouples the complicated landmine-soil interaction problem into a series of simplified simulation processes. First, the soil is discretized using a statistical scheme that can represent soil structure and texture in a statistical way based on experimental data. An empirical model is then utilized to model the blast air, which interacts with the debris and contributes to the overall pressure/impact force on the composite structure. Using this discretization scheme, the inhomogeneous property of soil, interactions between the blast wave and soil debris, and loading condition of the composite can be accounted for in blast load prediction so that the composite structure can be optimized with more complete loading conditions. Example simulation problems were given to illustrate the effectiveness and efficiency of the simulation model developed.
Conformal Tumor Treatment by the Combined Cryosurgical and Hyperthermic System: Optimal Configuration of the Multiple Probes
Authors: Deng Zhong-Shan , Liu Jing
Published: May 2009

Recently, a minimally invasive probe system capable of performing both cryosurgery and hyperthermia treatment for deep tumor was developed. With the increasing applications of such combined system, it becomes apparent that without optimal configuration of the multiple probes during multiple freeze/heat cycles, it is difficult produce a conformal lesion in the tumor tissue, which may lead to either insufficient or excessive freezing/heating and consequently, to tumor recurrence or to destruction of healthy tissue. In this study, a comprehensive three-dimensional numerical investigation is performed to design optimal configurations of the multiple probes used in the combined cryosurgical and hyperthermic treatment. The results presented in this study will be useful for treatment planning of the combined cryosurgical and hyperthermic treatment.
Research on the Startup Control for the Closed-Circuit Hydraulic System Based on Expert Control Method
Authors: Hu Dongming , Xu Bing , Yang Huayong
Published: May 2009

The closed circuit hydraulic system is a typical nonlinear and time-varying system. In order to get excellent startup performance, the controller based on expert control method was designed. The theoretical and experimental research of the controller was carried out. Firstly, the working principle of the closed circuit hydraulic system was introduced. The difficulties of pressure pre-balanced control and closed-loop speed control for the system starting were indicated because of its friction, high-inertia and time delay. The influence of nonlinear friction on the startup performance of the system was analyzed. And the initial model of the friction was established through experiments. Then, the intelligent controller was designed basing on expert control method. The startup performance was evaluated by the integral of difference between the desired and the practical speed while the system ran. The static friction model and the parameters of the controller can be modified by the expert controller according to the last two results. Finally, experiments were carried out under different work conditions, namely variable loads and oil-temperatures. The results show that the startup performance of the system is excellent. The robustness of the expert controller is strong under different work conditions. That is, the proposed method is robust in the presence of nonlinearities and uncertainties.
Multiscale Analysis for Virtual Prototyping and Performance Testing of Protective Fabrics
Authors: Swan Colby C. , Man Xiaolin , Yang Jun , Rasmussen Matthew , Williams Rob
Published: May 2009

In this paper we describe novel computational methods being used to facilitate analysis and design of textile fabrics used in functional clothing systems to protect people from threats such as extreme temperatures, radiation, ballistics, and hazardous chemicals. A multi-scale modeling approach is taken to attack this challenging problem. Beginning at the length scale of individual fiber diameters (tens to hundreds of microns), we use unit-cell methods to model frictional stick-slip interactions under various modalities of loading which give rise and contribute to the nonlinear and dissipative characteristics of textile fabrics. After assimilating these micro-scale interactions into mesoscale material models, we again use unit-cell methods to study the mechanical interactions between yarns with diameters on the order of millimeters. In particular, the nonlinear, anisotropic, and irreversible behaviors of fabrics are explored at finite deformations under various modalities of loading with these mesoscale unit cell models. Finally, we discuss how material models that integrate all of these structure-dependent behaviors are incorporated into macroscopic clothing models which are ultimately draped onto active digital human models.
“Heat Transfer” Traveling Engineering Activity Kit: Designed by Engineering Students for Middle School Students
Authors: Bailey Margaret B. , DeBartolo Elizabeth
Published: May 2009

A 2005–06 Multidisciplinary Senior Design team created a series of classroom activities designed to teach middle school students about engineering topics related to energy and the environment. This Traveling Engineering Activity Kit (TEAK) consists of five smaller kits, each based on a different energy-related theme: Heat Transfer, Electrical Energy, Wind and Water, Solar Power, and Chemical Energy. Each kit contains an Academic Activity to teach a background concept, a Hands-On Activity to allow students to apply the concepts learned, and a Take-Home Activity that can be done independently at home. The design team also developed instruction manuals suitable for non-engineers, lesson plans, handouts, and post-activity quizzes to assess participants’ learning. To date, the kits have been used by several hundred middle school students either in their classroom setting or while participating in on-campus outreach programs. This paper highlights the Heat Transfer TEAK including an overview of the intended learning outcomes; physical materials and set-ups included within the interactive kit; as well as details related to the development of the kit by a multi-disciplinary team of senior engineering students. Program and kit assessment progress is discussed based on feedback from design team members; middle school students and teachers. Future plans for refining current kits and expanding kit offerings are also discussed.
Solenoid Damping of the Pilot Poppet in a Forced-Feedback Metering Poppet Valve
Authors: Cline C. Harvey O. , Fales Roger
Published: May 2009

Forced-feedback metering poppet valves offer several advantages over spool valves as metering elements in hydraulic circuits. Despite these advantages, dynamic instabilities in their performance could limit their acceptance in this role. The pilot poppet damping is a source of uncertainty in dynamic response at certain operating conditions. Presently, in the forced-feedback metering poppet valve, the pilot poppet is damped by the flow of hydraulic fluid through a channel or orifice running through the poppet. Here, it is proposed that the solenoid be used to provide damping to the pilot poppet. The damping input to the solenoid is determined using the pilot poppet velocity. In practice, this is a readily unavailable variable and is estimated according to the self-sensing actuator concept. The proposed damping method is developed and analyzed in simulations. Simulations development and analysis occurred via a simplified, reduced order model of the pilot poppet stage.
A Review on Oil and Gas Pipeline Safety
Authors: Yarlagadda Rakesh , Badar M. Affan , Blyukher Boris
Published: May 2009

The safety of oil and gas pipelines has increasingly considered day by day to their vulnerability. Pipelines play a very critical role in the transportation of oil and natural-gas. As they have become the veins of oil industries, the productive design and analysis became more important. This made them more vulnerable to terrorist attacks. Although it is impossible to design pipelines to withstand any conceivable damage due to external (terrorist attacks, seismic effects) and internal effects (design and manufacturing defects), it is possible to improve the performance of pipelines. By understanding the design criteria, it saves lots of money and more over human lives and also protects the product in pipelines, which cannot be recovered and which is more and more scares day by day. This research aims: 1) to understand the different types of pipeline damages, reasons for their occurrence and their effects on the pipelines, such as mechanical damages, material defects, cracks, manufacturing defects, 2) to understand the explosions in pipelines, internal or external explosions and seismic distress, 3) to do research and literature review in analytical and numerical methods which allow researching the influence of shock waves (explosions, seismic), 4) to develop description of experimental research of pipelines subjected to shock waves (explosions, seismic), 5) to establish an effective methodology (develop mathematical model) to study the risk management in pipeline exploitation which can be subjected to such conditions like shock waves (caused by explosions, seismic, as well as mining activities) on pipeline systems (buried, on surface, or underwater), and 6) to establish criteria for risk management. This paper includes a review of the related literature covering the first two goals.
Experiments in Nucleation Dynamics of High Pressure Refrigerant in Pool Boiling Using Thermo Liquid Crystals
Authors: Joo Daniel , Kumar Ranganathan
Published: May 2009

Detailed analysis of nucleating surface temperatures using thermochromatic liquid crystal technique and temporal-temperature response under various heat flux and at 813.6kPa (118Psia) and 882.5kPa (128Psia) in R134A refrigerant has been performed. Liquid crystals thermo-chromatography uses encapsulated liquid crystals that are sensitive to temperature. The visualization system uses two high resolution and fast shutter speed cameras: one to measure the temperature and another to capture the bubble dynamics. Bubble frequency is found to be linearly proportional to the heat flux between 2500W/m2 and 5000W/m2. Bubble growth and departure have been captured. As the bubble departs from the surface, it is replaced by cooler fluid. This transient effect or form of micro-convection occurs at the same rate as the bubble frequency. Results show that this phenomenon occurs in less than 2ms and experiences a temperature drop of 2.5°C. From the time of departure, the temperature slowly rises roughly 1°C until the birth of the next bubble.
Modeling of Collision Resolution Algorithm in LonWorks Networks
Authors: Kaneshiro Percy Javier Igei , Garcia Melo Jose´ Isidro , Miyagi Paulo E. , Cugnasca Carlos E.
Published: May 2009

The industrial organization of productive processes have presented a tendency for dispersion and distribution of manufacturing plants based on an increase of resources and functionality of information and mobility technology. In this sense, Local Operating Networks (LON, LonWorks) is the name of one of the leading technologies in sensor/control networking, addressed to a wide range of applications with topology free technology. In spite of its popularity, only a few design tools are available to simulate LonWorks architectures and predict their performance. In this paper, a model of the collision resolution algorithm of LonWorks is described. The approach developed in this work is based on the characterization of LonWorks networks as Discrete Event Dynamic Systems (DEDS), since dynamic behavior is defined through the discrete events and discrete states. The proposed procedure employs techniques that are derived from interpreted Petri net, which has been used as an efficient tool for modeling, analysis and control of DEDS. In this context, the media access control sublayer (MAC) is modeled in different levels of abstraction: a conceptual model which is obtained using the PFS (Production Flow Schema) technique, and a functional model by using MFG (Mark Flow Graph). The MFG abstraction level describes details in a functional form preserving the description activities of upper levels. This procedure allows the structured development of models, facilitating the modeling process of the algorithm specification. The result presented in this paper for a single network segment can be integrated into a global networks modeling, since the proposed procedure decomposes the model systematically according to a hierarchal approach into different modules. In this way, it is straightforward to integrate single segments networks models into complex networks.
Study on Flow and Turbulence Inside a Stirred Tank and Investigation on the Effects of Macroinstability on Trailing Vortex Structures
Authors: Roy Somnath , Acharya Sumanta
Published: May 2009

Chemical process industries use stirred tank reactors (STR) for a variety of mixing and blending operations. Turbulent flow inside a baffled stirred tank reactor with a 45° pitched blade impeller is numerically studied using a large-eddy simulation (LES) technique with a body-fitted curvilinear mesh. The moving impeller geometries are modeled using an immersed boundary method (IBM). The instantaneous as well as time-averaged flow field suggests formation of trailing vortex due to the interaction of the fluid streams from the side and top edges of the blade. An enhanced distribution of turbulent kinetic energy has been observed in the vicinity of the trailing vortices. Instabilities occurring at a frequency lower than the frequency of impeller rotation are noticed from the time signal of the velocity components. The growth and break-up of the trailing vortices with this macro-instability frequency is observed. Turbulence is shown to be strongly anisotropic.
Application of High-Resolution Spatial Discretization Schemes to Volume-of-Fluid Simulations on Three-Dimensional Unstructured Meshes
Authors: Walters D. Keith
Published: May 2009

The interface capturing approach to volume-of-fluid (VOF) simulation relies on high-resolution spatial discretization of the volume fraction equation, without explicit reconstruction of the phase interface within computational control volumes. One advantage of this approach is that it may be applied on general topology meshes in a straightforward manner. This paper investigates the performance of two different high-resolution discretization schemes used for the solution of the volume fraction equation on three-dimensional unstructured meshes. The schemes are used to obtain results for several simple test problems, including convection of a round and a square phase profile in a uniform fluid stream, two-phase oil and water flow in an inclined channel, and convection of a round jet-in-crossflow. The performance of the two schemes is compared in terms of their ability to minimize the effects of numerical dissipation, which tends to “smear” the phase interface over several computational control volumes. It is shown that a recently proposed scheme that relies on maximization of the volume fraction gradient in the region of the interface yields substantially better results than a more commonly used NVD (normalized variable diagram) based scheme, as well as traditional first and second-order upwind schemes.
“Animal-Like, Sensor-Based Robot Motions: Learning From Nature”—An Interdisciplinary Project for Rising Sophomores at Lehigh University
Authors: Swann Jennifer M. , Perreira Noel D.
Published: May 2009

For the last three summers Lehigh University has sponsored a Research Experience for Undergraduates with support from the National Science Foundation, Department of Defense and Pennsylvania Infrastructure and Technology Alliance. Each year 10–12 rising sophomores were recruited from throughout the US to work with 4–5 graduate students and 2 professors from biological sciences and mechanical engineering. The project’s goal is to create a chemical sensing, mobile robot using a carbon based electronic nose developed by the California Institute of Technology for NASA and principles obtained from observations of the common housefly. To date the project has: developed protocols to train houseflies to approach or avoid a novel chemical stimulus; determined the electronic signature for a pure chemical using principal component analysis; and designed and built chambers for testing the enose and flies. Lab work and lectures are complimented by seminars from professionals in biology, engineering and robotics to expose the students to scientists from research and industry. Assessed by informal interview before and after the project indicated that the students learned basic principles in biology and engineering, and were more likely to enter these fields as a result of their participation in the project.
Phononic Band Gaps of Elastic Periodic Structures: A Homogenization Theory Study
Authors: Liu Ying-Hong , Chang Chien C. , Chern Ruey-Lin , Chang C. Chung
Published: May 2009

In this study, we investigate band structures of phononic crystals with particular emphasis on the effects of the mass density ratio and of the contrast of elastic constants. The phononic crystals consist of arrays of different media embedded in a rubber or epoxy. It is shown that the density ratio rather than the contrast of elastic constants is the dominant factor that opens up phononic band gaps. The physical background of this observation is explained by applying the theory of homogenization to investigate the group velocities of the low-frequency bands at the center of symmetry Γ.
An Experimental Characterization of the Failure Mechanisms Activated in GFRP Composites
Authors: Briggs Timothy M. , Ramulu M.
Published: May 2009

The static, flexural responses of two Glass Fiber Reinforced Plastic (GFRP) — SMC and Preform — material systems of varying fiber volume fractions were investigated. Failure mechanisms activated upon loading have been characterized through the use of numerical modeling during the damage progression. Both material systems were consolidated with a discontinuous, randomly oriented fiber distribution to give a quasi-isotropic, elastic behavior within the fiber distribution plane. Damage evolved and energy absorbed at each stage of failure is critical to the understanding of the progressive nature and the materials ability to mechanically store and dissipate energy. Preliminary experimental results show that the progressive nature of the damage is found to be consistent with the load redistribution at each stage.
A Computational Model for Pyrolysis, Gasification and Heat Transfer in an RDF Fixed-Bed Gasifier
Authors: Tsai C. Y. , Im H. G. , Kim T. Y.
Published: May 2009

To develop a predictive modeling capability for municipal waste gasification process, a 3-dimensional simulation code is developed based on the SIMPLE algorithm with momentum interpolation for pressure-correction. The two-phase flow and heat transfer processes due to the solid waste stack is modeled by a single-equation porous medium formulation with Darcy approximation. The pyrolysis process is described by a nonlinear Eulerian pyrolysis model to determine the porosity profile as well as the corresponding pyrolysis rate of the waste material. This generalized method simplifies the multiphase governing equations into gas phase equations. Polymethyl methacrylate (PMMA) was used as a test waste material for the simulation. Combustion behavior corresponding to the waste porosity, inlet conditions is studied for a range of operating conditions.
Dynamic Analysis and Simulation of a 1-DOF Driven by a Parallel Force/Velocity Actuator (PFVA)
Authors: Rabindran Dinesh , Tesar Delbert
Published: May 2009

Some work has been done to try to combine force control and velocity control capability into the same actuator design. The objective in trying to incorporate two fundamentally distinct resources (force and motion priorities) into the same actuator is to obtain an expanded spectrum of dynamic responses at the output of the system so that the system may (ideally) operate in pure force control mode or pure velocity control mode or a combination of these modes. Presented in this paper is a design that combines two fundamentally distinct actuators (one using low reduction or even direct drive, which we will call a Force Actuator (FA) and the other with a high reduction gear train that we will refer to as a Velocity Actuator (VA)). The premise of this work is that we could obtain a variety of responses at the system’s output by integrating separate force and motion priorities (Parallel Force/Velocity Actuator) within the same system in-parallel and dynamically “mixing” their contributions. We conceptually describe a Parallel Force/Velocity Actuator (PFVA) based on a Dual-Input-Single-Output (DISO) epicyclic gear train. We then present a dynamic model formulation for a non-linear 1-DOF mechanical system (Slider-Crank Mechanism) that uses a PFVA at the input. Using this dynamic model, we present a numerical simulation. The numerical simulation focuses on two issues, (a) effect of the relative scale change (ρ) between the two inputs on the torques at the two prime-movers and (b) effect of ρ on the dynamic coupling between the inputs. It was observed that as the relative scale change (represented by ρ) was decreased (i.e. the sub-systems tend towards behaving as “equal” systems) the dynamic coupling between the systems increased. In the study of the effect of ρ on the inertia and static torques at the prime-movers, it was noticed that they follow inverse trends.
Graduates Linked With Undergraduates in Engineering (GLUE): A Case Study
Authors: Rabindran Dinesh , Berry Tricia S.
Published: May 2009

This paper presents a case study from the Graduates Linked with Undergraduates in Engineering (GLUE) Program in the College of Engineering at The University of Texas at Austin. This student mentoring program, offered in the spring semester every year, pairs undergraduate students (mentees) with graduate researchers (mentors) to foster undergraduate research. The benefits from the GLUE program are two-fold. While the undergraduate mentees get a feel for research, the participating graduate students can enhance their research mentoring skills. In this article we present a GLUE case study in the area of Robotics. The mentee in this case was a sophomore in Mechanical Engineering and the mentor (the first author) was a senior doctoral student in Mechanical Engineering. The project involved the design and development of a Dual Input Single Output (DISO) epicyclic gear train to enhance the performance of a robot joint. The system was completely designed and tested using MSC.ADAMS. While describing the project, the paper will demonstrate the improvement in research skills of the mentee using three different sets of criteria from the literature.
Electric Field-Assisted Processing of Anisotropic Polymer Nanocomposites
Authors: Banda Sumanth , Ounaies Zoubeida
Published: May 2009

The performance of nanocomposites is affected by dispersion and patterning of the nanoinclusions in the polymer matrix. In this work, electrical and mechanical properties of single wall carbon nanotube polymer composites are tailored using AC electric fields. While the electric field is applied, the polymer is cured to freeze-in the alignment. The specific objectives are: to achieve efficient dispersion of the nanoinclusions in the polymer solutions; to investigate the alignment in liquid polymers in terms of electric field magnitude and frequency; and to quantify the alignment using electrical characterization in the liquid state and mechanical characterization in the solid state.
Studying Dynamic Behaviour of Flexible Rotors With an Analytic Model That Includes Non-Linear Supports, Non-Stiff Support Structure and Torsion Flexibility
Authors: Sa´nchez A. Heller G. , Pintor B. Jesu´s M.
Published: May 2009

This article presents a mathematical formulation based on FEM for the dynamic analysis of flexible rotors that are not grounded necessary to a rigid structure. Furthermore, it uses the component synthesis in order to introduce the behavior of the structure where the rotor is grounded. The developed mathematical model calculates the model parameters stationary response.