bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Transparent Indenter Measurement System and Indentation Analysis for Material Mechanical Property Evaluation
Authors: Kang Bruce S. , Feng Chuanyu
Published: April 2008

Since Tabor showed the application of spherical indentation approach to obtain material post-yielding true stress-strain curves, the indentation technique has been investigated to determine mechanical properties besides hardness measurement. Accurate measurement of indentation parameters is critical in the determination of surface mechanical properties using indentation method. In this research, an in-situ optical Transparent Indenter Measurement (TIM) method was developed for material inspection and mechanical property measurement. Using spherical indentation, residual surface deformation after spherical indentations was first investigated on IN783 superalloy samples using phase-shifting Twyman-Green and moire´ interferometry. The elastic-plastic boundary was identified based on the characteristic of the out-of-plane deformation fringe patterns. Then using the measured in-plane deformation, yield strength of the tested material was obtained. Using the TIM system, real-time in-situ measurement of indentation-induced out-of-plane deformation and contact radius were directly measured during an indentation process. Coupled with elastic recovery theories and 2D finite element analyses, a procedure was developed to determine the material stress-strain curve. It is also demonstrated that the TIM method is suitable for debonding inspection of thin film materials.
The Aerodynamics of an Actively Twisted Wing
Authors: Sonnenmeier James R. , Onipede Oladipo , Detar Andrew J. , Myers Heather L.
Published: April 2008

Aerodynamic performance of aircraft can be changed by moving separate surfaces which are mechanically connected to the main wing and moved with complex linkages. A possible alternative method of changing performance with less mechanical complexity is presented. Instead of separate control surfaces, the shape of complete aerodynamic structures can be changed with shape memory alloy (SMA) materials as part of the structure. In this work SMA wire is wrapped around a simple test wing. When activated by heating, the wire contracts which results in twisting the wing. The angle of attack along the wingspan changes which changes the aerodynamic forces on the wing. This could be used to optimize the flight condition. Results are presented from initial wind tunnel experiments which show the change in lift due to twisting. Aerodynamic models that account for the variable angle of attack along the span are also developed. The results from the experiments and aerodynamic model are compared.
Viscoelastic Wave Analysis of Hopkinson Split Bar System
Authors: Keskinen Erno , Vuoristo Taina , Kuokkala Veli-Tapani , Martikainen Matti
Published: April 2008

Axially elastic rods are basic machine elements in hydraulic hammers, pilers and percussive drills. The problem to analyze the motion history of such mechanisms is a very complex one, because the rods are simultaneously in large amplitude axial motion superimposed with a small amplitude elastic wave motion. The wave motion experiences division to reflected and transmitted components at each rod-rod interface depending on the current boundary stiffness. The wave motion in each rod can be computed by finite elements or alternatively in space of semidefinite eigenfunctions. The feasibility of these methods in solving wave propagation problems in multi-rod systems with nonlinearly behaving rod-rod interfaces has been investigated and evaluated. The object of the case study is a classical Hopkinson split bar apparatus used in experimental analysis of material response to shock pulses.
Nanostructured Materials by Machining
Authors: Swaminathan Srinivasan , Shankar M. Ravi , Rao Balkrishna C. , Brown Travis L. , Chandrasekar Srinivasan , Compton W. Dale , King Alexander H. , Trumble Kevin P.
Published: April 2008

Large strain deformation, a key parameter in microstructure refinement by Severe Plastic Deformation (SPD) processes, is a common feature of chip formation in machining. It is shown that the imposition of large plastic strains by chip formation can create metals and alloys with nanocrystalline or ultra-fine grained microstructures. The formation of such nanostructured materials is demonstrated in a wide variety of material systems including pure metals, light-weight aluminum alloys, and high strength steels and alloys. Nanocrystalline microstructures with different morphologies are demonstrated. The hardness and strength of the nanostructured chips are significantly greater than that of the bulk material. The production of nanostructured chips by machining, when combined with comminution and powder processing methods, may be expected to lead to the creation of a number of advanced materials with new and interesting combinations of properties. These materials are expected to find wide-ranging applications in the discrete products sector encompassing ground transportation, aerospace and bio-medical industries.
Comparative Study on the Dynamics of Rotating Paramagnetic Particles Simulated by Particle Dynamics, Stokesian Dynamics and Lattice Boltzmann Methods
Authors: Krishnamurthy S. , Yadav A. , Phelan P. E. , Calhoun R. , Vuppu A. K. , Garcia A. A. , Hayes M. A.
Published: April 2008

Paramagnetic particles, when subjected to external unidirectional rotating magnetic fields, form chains which rotate along with the magnetic field. In this paper three simulation methods, namely particle dynamics (PD), Stokesian dynamics (SD) and Lattice Boltzmann (LB) methods, have been used to study the dynamics of these rotating chains. SD simulations with two different levels of approximations—additivity of forces (AF) and additivity of velocities (AV)—for hydrodynamic interactions have been carried out. The effect of hydrodynamic interactions between paramagnetic particles under the effect of a rotating magnetic field is analyzed by comparing the LB & SD simulations, which include hydrodynamic interactions, with PD simulations in which hydrodynamic interactions are neglected. It has been found that for macroscopically observable properties like average chain length as a function of Mason number (Ma), reasonable agreement is found between all the three methods. For microscopic properties like the force distribution on each particle along the chain, inclusion of hydrodynamic interaction becomes important to understand the underlying physics of chain formation. This has been validated by the fact that when the phase angle is calculated as a function of Ma using PD and SD simulations, PD simulations showed higher values compared to SD simulations at lower Ma. A comparison with experimental data showed SD method to be more accurate at low Ma. Further comparison between the two approximations of SD simulations revealed that the AF method reproduces hydrodynamic interactions more accurately.
The Pedagogy of Green Engineering in Undergraduate Heat Transfer
Authors: Flynn Ann Marie , Naraghi Mohammad H. N. , Austin Nicole , Helak Sean , Manzer Jarrod
Published: April 2008

The work provides an outline for instructors who wish to incorporate green engineering concepts into a typical non-green engineering course. The outline is the result of the assessment of the incorporation of green engineering concepts into a traditional, design and analysis oriented heat transfer course offered to chemical engineering students in the fall semester of their junior year. This work not only incorporates the instructor’s assessment of the newly greened course but also assessment of the same course by a student task force. This work includes portions of the instructor’s assessment, the student task force’s independent assessment of the course as well as the task force’s assessment of the instructor’s proposed modifications to the course. Finally, the student task force has identified 5 critical elements to the successful integration of green engineering concepts into a traditional, design-oriented, non-green engineering course. Even though this study focuses on green engineering as it relates to heat transfer, the assessment and suggestions are relevant to all engineering courses that have integrated green engineering topics.
Thermo-Mechanical Analysis of Composites Under Combined Conduction Heating and Large Deflection Bending
Authors: Ju Jaehyung , Morgan Roger J. , Reddy J. N.
Published: April 2008

A novel conduction heating apparatus that combines thermal loading with large deflection bending is introduced, and its effectiveness for thermo-mechanical stress analysis was investigated. By clamping composite specimens (M40J/PMR-II-50, [0,90]s, a uni-tape cross-ply) on the radial sides of half cylinders having two different radii (78.74mm and 37.96mm), three different in-plane strains including a no strain condition were applied to the composites. Three different thermal loading experiments, 1) 23°C to −196°C to 250°C, 2) 23°C to 250°C, and 3) 23°C to −196°C were performed as a function of mechanical in-plane strain levels. The apparatus was excellent enough to generate cracks related to the in-plane stresses (or strains) on plies. The quadratic failure criteria solution based on the thermal residual stresses shows a good agreement with the experimental results at low temperatures, but does not supply a good agreement at high temperatures. A weak adhesion of fiber/matrix interface at high temperatures (250°C) might cause the de-bonding at the interface and subsequent exposure to −196°C caused the intensive crack propagation.
Vibration Control of a Flywheel Energy Storage Device Using a DC Motor as a Radial Force Actuator
Authors: Leuschke Rainer , Fabien Brian C.
Published: April 2008

This paper presents a technique for vibration suppression in a rotordynamic system. The approach implemented involves using a DC motor for simultaneous torque and radial force actuation. Here, the rotor is supported via passive permanent magnetic bearings. The permanent magnets are arranged so that, for small motions, the rotor can be treated as a spinning top that is supported radially by linear springs. The device includes an axial flux, three phase, brushless DC motor that is used to produce a torque. The same motor is also used to develop radial forces to control the vibration of the rotor. This is accomplished by using two phases of the motor for torque generation, and one phase to produce radial forces. The paper develops a set of equations that can be used to predict the radial force generated by the motor coils. These equations are used to implement a feedback control system to regulate the radial position of the rotor. Experiments are conducted to verify the coil force equations and demonstrate the effectiveness of the feedback control scheme.
Passive and Active Shock Absorbing Prostheses for Lower Limb Amputees
Authors: Howell Eric B. , Klute Glenn , Devasia Santosh
Published: April 2008

Excessive transient forces arising from foot-ground during gait can be related to increased incidence of degenerative joint disease, residual limb blisters and ulceration, muscle tears, stress fractures, and chronic low back pain. For the lower extremity amputee with only residual capacity to attenuate transient forces, effective protective interventions are an essential element of the prosthetic prescription. To facilitate understanding of the components and design variables that may influence shock absorption, a lumped parameter model simulating the movement of the human body, prosthetic components, and footwear for the first 150 ms following initial foot-ground contact is developed in conjunction with a cost function relating dose, magnitude and frequency with adverse health effects. The prosthetic foot was found to have the greatest potential for attenuating impact forces compared to the pylon and socket liner. Using the model to explore the design space, optimal passive designs were able to reduce the adverse-health-effects, cost function by 20% from those of seven different, commercially available, prosthetic feet. Optimal passive designs at the pylon and socket liner produced smaller reductions in cost while at the same time creating undesirably large displacements that could potentially lead to asymmetrical gait and secondary disabilities. While optimal passive designs were able to provide a significant cost reduction over existing prosthetic feet, further exploration of the design space reveals active shock absorbing feet have the potential to reduce the adverse health effects cost function by 57%.
Analysis of Short Pulse Radiation Transport Through Tissues for Tumor Detection
Authors: Basu Soumyadipta , Pal Gopalendu , Mitra Kunal , Grace Michael S.
Published: April 2008

The objective of this paper is to perform a comprehensive experimental and numerical study to analyze short pulse laser propagation through animal tissue samples and phantoms with inhomogeneities imbedded in them. Initially a parametric study of different absorption and scattering coefficients of the tissue phantoms and of inhomogeneities imbedded in them, size and location of the inhomogeneities is performed in order to optimize the time resolved optical detection scheme. Tissues can be modeled primarily as having two main layers-skin and the underlying muscle. To study the interaction of light with the tissue layers, experiments are next performed on freshly excised rat tissue samples to validate the time varying optical signatures of rat skin and muscle with the numerical model. The next step is to perform in vivo imaging of anaesthetized rats with tumors injected on the skin as well as below the skin surface in order to test the optical detection scheme. The goal is the detection and characterization of tumors in rats.
Design and Performance Evaluation of Advanced Window Systems
Authors: Butterfield Amy , Wilk Richard D.
Published: April 2008

This paper presents the results of a study to compare the heat transfer characteristics of silica aerogels to that of air. A small window unit was made with a section having monolithic silica aerogels sandwiched between two plates of window glass. Another section had just an air space in between. Upon constant heating, steady state temperature measurements were made across the window unit. These data were used to infer apparent thermal resistance values for each case. The measured results showed that the aerogel insulation had a thermal resistance approximately 20% greater than that of air alone. A numerical heat transfer model of the system was developed in Cosmosworks. The model was used to match the experimental results and determine calculated thermal conductivity values for each of the interface cases: silica aerogel and air. The calculated thermal conductivity value of the aerogel matched well with typical values for this material. The calculated value for air though was approximately four times higher than the published value. This difference was attributed to the occurrence of free convection in the air space which was not accounted for in the model.
Refinement of Reduced Chemical Mechanisms for the Modeling of the Rapid Compression Combustion of Heptane and Octane
Authors: Goldthwaite Donald , Metghalchi Mohamad , Keck James C.
Published: April 2008

Reduced chemical mechanisms for heptane and octane, originally developed by Keck and Hu, have been shown to give excellent agreement with experimental ignition delay times obtained using a rapid compression machine. These mechanisms consist of 20 species and 41 reactions with 10 reactions detailing the initial breakdown sequence of the alkane, 2 global reactions leading to the formation of end products, and the remaining reactions specifying the path to equilibrium products. Until recently, the success of these mechanisms in matching experimental data rested in large part on the fine tuning of forward rates, and the inclusion of specified reverse rates. For a given reaction, the calculation of the reverse rate from the forward rate and the equilibrium constant—detailed balancing—is the technically correct approach, and the focus of this work was the elimination of the specified reverse rates in favor of this approach. Elimination of the specified reverse rates was found to depend on the accuracy of the thermodynamic property data generated with NASA style polynomial coefficients. Both mechanisms are now able to match experimental data generated with the M.I.T. rapid compression machine with impressive agreement, by employing detailed balancing for the calculation of reverse rates. Current computation techniques include the Detailed and Rate Controlled Constrained Equilibrium methods. However, at the present time, only the detailed method includes the algorithm to model the rapid compression sequence. Work to incorporate the algorithm into the RCCE computation is now underway.
Cost Estimation and Quality Comparison for Sound Welds
Authors: Qureshi Ejaz. M. , Ahmad Jamil , Malik Afzaal M. , Khan Iqbal , Dar Naeem Ullah
Published: April 2008

A number of new materials are being developed for advanced applications like nuclear pressure vessels, missile casing and pressurized chambers for space launching vehicles. These newly developed high strength alloys demanding high strength joining, put rigorous requirements on the manufacturers to weld smartly i.e. sound welds at competitive cost. Welding is a very complex phenomenon and the quality and cost of the weldment is a function of interaction between a number of variables, making it more difficult but still indispensable to estimate the cost effects of different welding processes for smart welds. The primary objective of this research work is to develop, apply and evaluate state of the art methodical approach to compare and select welding processes in a productive environment based on market requirements of quality and costs for aerospace and nuclear applications. A case study based on several welding processes: SMAW, GTAW, pulsed GTAW, GMAW with CO2 and Argon shielding gases and pulsed GMAW is conducted both from quality and cost aspects. For quality analysis, geometrical aspects of the weld beads and for cost analysis, welding parameters and prices of consumables are considered. In appendage to that, sensitivity analysis of the cost for different variables is also conducted to evaluate the effects of variation in the values of significant variables on the cost.
Ontologies and Fine-Grained Control Over Sharing of Engineering Modeling Knowledge in a Web Based Engineering Environment
Authors: Kanuri Neelima , Grosse Ian R. , Wileden Jack C. , Chiang Wei-Shan
Published: April 2008

Within the knowledge modeling community the use of ontologies in the construction of knowledge intensive systems is now widespread. Ontologies are used to facilitate knowledge sharing, reuse, agent interoperability and knowledge acquisition. We have developed an ontology for representing and sharing engineering analysis modeling (EAM) knowledge in a web-based environment and implemented these ontologies into a computational knowledge base system, called ON-TEAM, using Prote´ge´1. In this paper we present new object-oriented methods that operate on the EAM knowledge base to perform specific tasks. One such method is the creation of a flat technical report that describes the properties or class relationships of an engineering modeling analysis class and/or the modeling knowledge involved in the development of a specific engineering analysis model. This method is a JAVA application that accesses the EAM knowledge base application using the Prote´ge´ application programming interface. It presents the user a graphical user interface for selecting the EAM class or specific analysis model instance and then exports the appropriate knowledge to a text file to form the basis of a technical report. Secondly, a method controlling knowledge access and sharing is under development which allocates permissions to portions of the knowledge base according to accessibility permissions. This method controls as efficiently as possible fine grain knowledge sharing. Both the methods acting together enable automatic generation of recipient-specific technical reports based on the recipient’s security permissions, customized knowledge viewing, and customized knowledge exporting through various knowledge exchange formats such as XML Walsh [1], RDF Klyne [2], etc. Finally, implementation of these methods and our EAM knowledge base application as components within commercial web-based distributed software architecture is presented.
An Analysis of Elastic Deformation Induced by Gradient Residual Stresses in Multilayered MEMS Structures
Authors: Huang Shusen , Zhang Xin
Published: April 2008

This paper presents an elastic analysis of a multilayered system due to the gradient residual stresses. Given the residual strain distribution, the elastic deformation of a multilayered structure can be determined using the derived general solution. Bimaterial cantilevers are widely used as sensing and actuation components in MEMS devices. Assuming the residual strain in each layer of such a bimaterial cantilever is linearly distributed, the error induced by evaluating its curvature without the gradient item is studied. The distributions of normalized deformation strain and real strain in a bilayered cantilever is also given. The positions of deformation plane and neutral plane in that cantilever as well in three more cases are summarized. The presented results in this paper shows that missing the gradient residual stress in multilayered systems may lead to serious misunderstanding of the deformation, and therefore, the model built in this paper may help in the development of multilayered structures in MEMS devices.
Design Methodology for Assembly and Disassembly Based on Rating Factors
Authors: Shetty Devdas , Coimbatore Vishwesh , Campana Claudio
Published: April 2008

Design engineers need an automated tool to effectively analyze the ease of assembly & disassembly of the subassemblies and the innovative products they create. A good assembly design makes it easier to service, easier to repair and maintain. Due to current environmental regulations the designers are forced to think about the life cycle of a product, recycling and reuse aspects of the products from the very beginning. This creates an environment for efficient implementation of design for manufacturing tools and techniques. A New Design for Assembly / Disassembly (DFA/DFD) Evaluation methodology explained here enables the designer to review the design for assembly and disassembly difficulties by considering several contributing factors and their importance to successful product creation. The technique is based on the criteria of “Rating Factors”. A spreadsheet format is used to create the front end interface for the user and to include all the influencing factors. The major parameters considered for the study are access, tool, task, re-use, removal, recyclability. Since the product maintenance is an important factor additional maintenance related issues such as spare parts, waiting time, priority and cost are considered as rating factors. The new methodology was compared with other existing techniques and found to be valid and useful to manufacturing industries.
Electrolytic Micro Machining Technology
Authors: Risko Donald G.
Published: April 2008

The electrolytic machining process that has been used for many years to machine airfoil surfaces in turbine engine applications and critical features in diesel injection nozzles is emerging as a machining process for features in the 1 to 100 micron range. Like Electrochemical Machining (ECM), Electrolytic Micro Machining is a very fast area based machining process. In most cases, all features can be machined simultaneously in two to three seconds or less. The technology draws upon the basics of ECM which is an application of Faradays Law to metal removal. Tooling that consists of precise cathodes and fixtures are critical to the machining outcome, as are other factors such as electrolyte parameter selection. Using pulsed direct current to achieve high current densities with necessary “relaxation” time, can enable the process to machine in a predictable manner. Tooling is not consumed in the traditional sense, therefore, the economics of the process for medium to high volume production is very attractive.
Evaporative Heat Transfer From Ten-Micron Micro-Channels
Authors: Quy T. A. , Carpenter D. A. , Richards C. D. , Bahr D. F. , Richards R. F.
Published: April 2008

Evaporative heat transfer from ten-micron square open-top micro-channels is investigated experimentally. The channels are fabricated by spinning ten microns of SU-8 on a two micron thick silicon membrane and using a photolithography process to create micro channels in radial and annular patterns. The working fluid, FC77, is pumped by capillary forces into the channels from a reservoir at the edge of the silicon membrane. Electrical power is dissipated in a thin-film heater in the center of the membrane. The liquid front of working fluid in the channels is visualized with a long-distance microscope and CCD camera. Sensible heat conducted radially out of the membrane is measured with two concentric annular PRT’s. The mass of working fluid evaporated from the micro-channels is determined gravimetrically. A global energy balance including latent and sensible heat transfer out of the system is then tabulated. The study shows that only five to ten percent of the power going into the membrane is carried away by evaporation while the remaining ninety to ninety-five percent of the power is conducted out along the membrane.
Numerical Modeling of EPS Foam Decomposition in the Lost Foam Casting Process
Authors: Liu X. J. , Bhavnani S. H. , Overfelt R. A.
Published: April 2008

The importance of smooth mold filling in the lost foam casting process has been recognized for a long time. The more uniform the filling process, the better the quality of the casting products that are produced. Successful computer simulations can help reduce the number of trials and cut down the lead time in the design of new casting products by better understanding the complex mechanisms and interplay of different process parameters in the mold filling process. In this study, a computational fluid dynamics (CFD) model has been developed to simulate the fluid flow of molten aluminum and the heat transfer involved at the interfacial gap between the metal and the expanded polystyrene (EPS) foam pattern. The commercial code FLOW-3D was used because it can track the front of the molten metal by a Volume of Fluid (VOF) method and allow complicated parts to be modeled by the Fractional Area/Volume Ratios (FAVOR) method. The code was modified to include the effects of varying interfacial heat transfer coefficient based on gaseous gap pressure which is related to foam degradation and coating permeability. The modification was validated against experimental studies and the comparison showed better agreement than the basic model. Process parameters such as initial metal temperature, foam pattern property, and gating system were investigated. The defect prediction model was also used to study the dependence of defect formation on the process variables.
Modeling of Web Slip on a Roller and Its Effect on Web Tension Dynamics
Authors: Dwivedula Ramamurthy V. , Pagilla Prabhakar R.
Published: April 2008

This paper considers the effect of web slip over the rollers on the span tension dynamics. In classical development of the web span tension dynamics, it is assumed that there is strict adhesion between the web and the surface of the roller and thus, there is no slip-page between the web and the roller. As a result of this assumption, effect of tension disturbances in downstream spans on the upstream span tension is precluded. However, in practice, perfect adhesion between the web and roller surface is seldom achieved and tension disturbances propagate upstream also. Though web span tension dynamic models that include slippage between web and roller are proposed, these models rely to a great extent on numerical computation of slip arc angles and are prohibitively complex to be of practical use. This paper proposes an alternative, simple approach for developing web span tension dynamics to include the effect of web slip.
Moisture Effects on Copper Thin Film Adhesion
Authors: Waters Patrick J. , Volinsky Alex A.
Published: April 2008

The effects of moisture on copper thin film adhesion have been investigated using a modified version of the superlayer indentation test. Copper films up to 100 nm thick were sputter deposited on thermally oxidized silicon wafers. A 1 μm tungsten superlayer with 1 GPa compressive residual stress was sputter deposited on top of Cu films, providing extra energy for interfacial debonding upon indentation. The samples were first indented to a depth just greater than the thickness of the W/Cu bi-layer and then unloaded. Water was introduced to the indent, and a second higher load indent was made in the exact same location as the first one to drive crack propagation in the wet environment. For the indents made to the same maximum load, there was a dramatic increase in blister size in the wet environment compared to the blister size in the dry environment. Copper film adhesion in the presence of water was up to 20 times lower than in the dry environment (0.1 J/m2 vs. 2 J/m2). Chemical reactions at the crack tip along with the surface energy minimization by water are thought to be the causes for the adhesion reduction.
Multi-Scale Analyzer for Assessing Processing Uncertainty on Marine Composite Structures
Authors: Lua Jim , Hess Paul E. , Lopez-Anido Roberto , Dagher Habib J.
Published: April 2008

The material uncertainty resulting from variability in VARTM composite material processing has driven the present design based on the “knock-down factor (factor of safety)” approach. The coarseness of marine-grade composites has prevented development of a useable process model by which the effects of the processing parameters may be predicted. There is an immediate need to assess the effect of processing uncertainty on thermal-mechanical properties and their subsequent impact on structural response, damage accumulation, and ultimate failure. In this paper, a multi-scale, probabilistic analyzer is developed by integrating the existing micromechanics-based woven fabric analysis module (TMAT) and a laminated plate solver with a probabilistic analysis framework. The effects of processing induced random constituent and microstructural parameters on the ply properties are determined first and then propagated into the laminated composite plate model. The sensitivities of these random parameters on the variability of ply and laminate stiffness matrices are also determined to identify the dominant contributor to enhance the ply/plate stiffness.
Effective Thermal Diffusivity of Porous Media in the Wall Vicinity
Authors: Sakamoto Hitoshi , Kulacki Francis A.
Published: April 2008

Transient conduction on a vertical, constant heat flux surface in a saturated porous medium is studied experimentally and analytically with a focus on determining near-wall thermal diffusivity. For combinations of different particulate solid and interstitial fluid, which give a range of conductivity ratios, ks/kf, from 0.5 to 2400, the present study finds that early-time transient temperature profiles can be analytically predicted using the thermal conductivity of the interstitial fluid because the near-wall porosity approaches 1.0. The conjugate heat transfer analysis accurately predicts the time the conductive front takes to travel through the impermeable wall. The present study also finds that conductive heat transfer along the wall is dependent on the wall thickness and must be taken into account when assessing measurement of local and overall Nusselt numbers. The present results raise the possibility of reinterpretation of much of the porous medium heat transfer experiments that make up the current database.
A Method to Demonstrate the Importance of Homework
Authors: Penrod James P.
Published: April 2008

Many educators utilize homework as an important component of the learning process. The problem is that often times their students may not recognize the importance as well. To rectify this problem, a number of strategies were tested while instructing undergraduate engineering technology students. These experiments met with limited success including outright failure. Recently, a method that appears to clearly demonstrate the importance of homework to students was used. This paper outlines this method and provides case study data supporting the assertion that the method can be effective.
Piezoelectric Thin Film AlN Annular Dual Contour Mode Bandpass Filter
Authors: Stephanou Philip J. , Piazza Gianluca , White Carolyn D. , Wijesundara Muthu B. J. , Pisano Albert P.
Published: April 2008

The following work presents the analytical, numerical and experimental characterization of a novel piezoelectric Aluminum Nitride MEMS bandpass filter. In contrast to multipole filters employing distinct mechanically or electrically coupled resonator building blocks, the passband of the device in the present work is defined by the proximity of two natural contour modes of vibration in a single annular resonator. The proposed implementation, albeit currently limited to dual-pole filters, results in smaller form factors and reduces device sensitivity to across wafer fabrication tolerances.
Thermal Design of a DWDM Optical Network System
Authors: Hendrix W. Mark
Published: April 2008

DWDM optical transport systems are an important link in communications networks. These systems are the backbone of telecommunications infrastructures and carry large volumes of telecom traffic. As a result, their reliability is critical. Thermal performance is key to meeting this reliability requirement and is therefore a major component of DWDM system development. The resulting thermal design process must balance opposing requirements such as high product density, thermal sensitivity of optical components, cooling fan noise limits, and high ambient temperature and altitude requirements. This paper describes both a thermal design approach for DWDM system development, and a thermal design solution that demonstrates high product density and field-proven reliability.
Design and Analysis of a Double Superimposed Chamber MEMS Micropump
Authors: Zordan Enrico , Amirouche Farid
Published: April 2008

The mathematical model of a double chamber pump is obtained by dividing the problem in two separate ones. The first that considers inertia force and viscous loss in relation of actuation pressure and frequency is obtained, and then a model of the nozzle/diffuser elements is introduced. The value of the flow rate obtained from the first model is then introduced in the second to determine the loss coefficients starting from geometrical properties and flow velocity. Then the loss coefficients obtained are used in the first model to obtain a new value of flow rate. These two models have been implemented in a Matlab® code that numerically reaches convergence repeating the cycle above. Using this model is possible to predict performances of the micropump only from geometrical properties and actuation parameters, without assumptions about the loss coefficients. A similar model is obtained for a single-chamber pump with geometrical dimensions equal to each chamber of the double chamber pump, and the results from both the models are then compared for equal applied actuation pressure and frequency. Results gives for our pump a max flow working frequency that is about 30% lower than the single chamber design, with the same applied pressure on the membrane, same geometry of parts and materials, and a max flow rate that is about 140% of the single chamber max flow in max flow conditions. For lower frequencies flow rate is more than twice, and maximum membrane deflection smaller up to 20% less. These results can change due to geometrical and material properties. Finally the influences of every significant geometrical property on flow rate, maximum flow frequency, loss coefficients and membrane strain are examined, and the nozzle/diffuser initial width and chamber side length are founded to be the most important dimension.
Non-Destructive Evaluation (NDE) of Space Application Panels Using Piezoelectric Wafer Active Sensors
Authors: Cuc Adrian , Tidwell Zeb , Giurgiutiu Victor , Joshi Shiv
Published: April 2008

Ultrasonic guided waves inspection using Lamb waves is suitable for damage detection in metallic structures. This paper will present experimental results obtained using guided Lamb waves to detect flaws in aluminum specimens with design features applicable to space applications. Two aluminum panels were fabricated from a variable-thickness aluminum top plate, with two bolted I-beams edge stiffeners and four bonded angle stiffeners. Artificial damages were introduced in the two panels: cracks, corrosions, and disbonds. The proposed investigation methods used embedded piezoelectric wafer active sensors (PWAS) to excite and receive Lamb waves. Three wave propagation methods were used: pitch-catch, pulse-echo, and the embedded ultrasonic structural radar (EUSR). In addition, we also used a standing-wave damage detection technique, the electro-mechanical impedance method. The paper will present in detail the salient results from using these methods for damage detection and structural health monitoring. Where appropriate, comparison between different methods in detecting the same damage will be performed. The results have demonstrated the ability of piezoelectric wafer active sensors working in conjunction with guided Lamb waves to detect various types of damages present in complex geometry structures typical of space applications.
Modeling Horizontal Well Oil Production Using Modified Brinkman’s Model
Authors: Belhaj Hadi , Mustafiz Shabbir , Ma Fuxi , Satish M. , Islam M. R.
Published: April 2008

Horizontal well oil production has been numerically studied by using the Modified Brinkman’s Model. This model has been used along with the Darcy-Weisbach pipe flow equation in modeling of coupled porous medium/pipe flow. The results include seepage flow rate along the horizontal well, velocity distribution, pressure drop, and production pressure drop between the two ends of the horizontal well. They have been compared with those from Darcy model. It is found that when the fluid’s viscosity is low, there is a big difference between the results from the two models. However, when the fluid’s viscosity is high, the difference tends to vanish. In addition, two striking findings have been observed: (a) the curves for the distribution of the seepage flow rate along the pipeline are more flat than that from Darcy model. However, a higher viscosity makes the curve more uneven. This reverses the trend from Darcy model. (b) The velocity in the pipe is more uniform by MBM than that by Darcy model. The curves of V ~x become more uniform in the pipe when the fluid has a lower viscosity. This again reveres the trend from the Darcy model.
Micro-Cantilever Based Metrology Tool for Flow Characterization of Liquid and Gaseous Micro/Nanojets
Authors: Lee Jungchul , Naeli Kianoush , Hunter Hanif , Berg John , Wright Tanya , Courcimault Christophe , Naik Nisarga , Allen Mark , Brand Oliver , Glezer Ari , King William
Published: April 2008

This paper reports the development of MEMS metrology tools to characterize liquid and gaseous jets ejected from micro/nanofabricated nozzles. To date few highly local measurements have been made on micro/nanojets, due in part to the lack of characterization tools and techniques to investigate their characteristics. Atomic force microscope cantilevers are well-suited for interrogating these flows due to their high spatial and temporal resolution. In this work, cantilever sensors with either integrated heating elements or piezoresistive elements have been fabricated to measure thrust, velocity, and heat flux characteristics of micro/nanojets.
Experimental Operation and Characterization of a Free Piston Compressor
Authors: Riofrio Jose , Barth Eric J.
Published: April 2008

The ongoing design evolution of a free piston compressor (FPC) is presented in this paper. The FPC is a proposed device that utilizes combustion of a hydrocarbon fuel to compress air into a high-pressure supply tank. This device is designed to extract chemically stored energy from the fuel and convert it to potential energy of compressed air, while achieving high conversion efficiency relative to other small-scale portable power supply systems. The chemically stored energy of the hydrocarbon fuel is first converted into kinetic energy of the free piston by the end of the combustion phase. Subsequently, the moving piston acts as a pump and air compressor during a compression phase. The proposed technology is intended to provide a compact and efficient pneumatic power supply source appropriate for human-scale robots. The design and implementation of this version of the FPC is shown, and experimental results relating all phases (combustion, expansion and pumping) are discussed. The total efficiency of the system is experimentally measured and compared to its theoretical prediction.
The Effect of Irradiation on Immiscible Fluids for Increased Oil Production With Horizontal Wells
Authors: Bjorndalen Nancy , Mustafiz Shabbir , Islam M. R.
Published: April 2008

Oil recovery using horizontal wells gives an undeniable benefit to the petroleum industry. One of the problems of using this method is that the wells can plug due to pressure and temperature changes. The components of crude oil such as asphaltene and paraffin wax can precipitate in the horizontal section of the well causing a loss of productivity and profit. Microwave or irradiation has been proposed to remove these precipitates remotely. The effect of microwaves on crude oil properties has been studied and a numerical model is presented to gain an understanding of the effect of the rise in temperature. These results include temperature increases for various concentrations of crude oil, and paraffin wax under different exposure times. The effect that different media (bentonite and gypsum) has on the temperature of these components has also been studied. By understanding the temperature rise, one can determine the effect that irradiation will have on oil production. Overall, the agreement between experimental and numerical results was acceptable.
A Case Study in Assessing Team-Based Design Courses That Integrate Industry-Sponsored Projects
Authors: Keefe M. , Glancey J. , Cloud N.
Published: April 2008

In general, assessing the learning process is difficult because objective measures are not readily available, and the time needed to fully evaluate is considerable. This problem is perhaps exacerbated in team-based courses, where learning is unstructured in large part and the body of knowledge expected to be learned is variable. Additional issues that complicate assessment include cross-disciplinary teams, project variability and the involvement of external mentors including industrial sponsors, guest lecturers and consultants. Collaborative learning in a team setting is beneficial to improving undergraduate science and engineering courses; however, no specific assessment tool has been used to evaluate its validity. As a result, novel techniques need to be developed to assess the value of team-based learning. This paper describes the experiences and lessons learned in assessing student performance in team-based project courses culminating in a senior capstone experience that integrates industry-sponsored design projects. Analysis of assessment data collected over the last four years indicates that student performance, measured by faculty grades and industry sponsor evaluations, is not significantly affected by the faculty advisor, project type or sponsoring company size. This is attributed to the focus on assessing student performance in executing the design process, and less on project results. However, faculty assessments of student performance do not correlate very well with industry sponsor assessments.
Numerical Time Reversal Processing for Impact Detection Using Surface Bonded Piezoceramic
Authors: Adachi Kazuhiko , Sakai Yousuke , Sakota Kinya
Published: April 2008

Time reversal processing for measured sensor signal can be applied to detect not only structural damage but also impact loading of the structure. In this study, a model based impact detection method for structural health monitoring is proposed. Impact identification capability of the numerical time reversal processing is demonstrated by using a rectangular aluminum plate with nine surface bonded piezoceramic sensors. Illustrative numerical simulation results indicate that the proposed method can be successfully identifying both exact impact point and time.
On Noise Control in Turbomachinery Using an Automated Multidisciplinary Design Optimization System
Authors: Idahosa Uyigue , Golubev Vladimir
Published: April 2008

In this work, we review our recent efforts to develop and apply an expanding database of aerodynamic and aeroacoustic prediction technologies for exploring new conceptual designs of propulsion system turbomachinery components optimized for high-efficiency performance with minimum noise radiation. In this context, we first discuss construction of our automated, distributed, industry-like multi-disciplinary design optimization (MDO) environment used in all the studies. The system was developed on the basis of commercially available optimization modules, and involves a user-friendly interface that provides an easy link to user-supplied response analysis modules. We address various issues in the automated optimization procedure with focus on turbomachinery design, including proper geometry parameterization, algorithms selection, and transparent interconnections between different elements of the optimization process. In a benchmark study testing the performance of the system in application to aero/acoustic optimization, we consider a problem of optimal blade design to minimize fan noise, a dominant source of sound radiation both in high-speed fan applications (such as high-bypass-ratio turbofans, propellers of turboprop and IC engines in general aviation, and helicopter rotors) and low-speed ones (including applications in automotive, computer, air-conditioning and other industries). Two approaches are investigated, with the first relying on commercial CFD software coupled with an unstructured mesh generator, and the second employing a panel-based aerodynamic code integrated with an integral acoustic solver. Success of various optimization algorithms (including gradient-based and evolutionary) in finding global minima of the objective function for a noise metric in both unconstrained and constrained optimization processes is examined.
Rupture Process During Drop Coalescence
Authors: Aryafar H. , Kavehpour H. P.
Published: April 2008

During the coalescence of a drop with a planar interface, a hole is generated in a microscopic film that separates the drop from the interface. An experimental study has been performed to investigate the time dependent behavior of the radius of the hole generated during coalescence. The study consisted of placing drops of various sizes and physical properties on a planar interface. The coalescence process was recorded from underneath the interface with the aid of a high speed digital camera and a prism. The experiment captured two separate processes, film rupture and the closing of the hole. During the film rupture, the hole radius demonstrated a power law time dependence. Dimensional analysis showed the percentage of time the hole used to reach its maximum radius was approximately constant for all drops. Moreover, all dimensionless drop rupture radii and times fit onto a single master curve and were independent of their physical properties during the opening. However during the closing of the hole, the dimensionless time and radii did not fit a master curve analogous to the hole rupture. The closing of the hole is an entirely different event from the opening and is governed by different parameters.