bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow in a Co-Axial Control Valve
Authors: An Hailing , Suh Jungsoo , Plesniak Michael W. , Frankel Steven H.
Published: May 2008

An experimental and computational investigation of the complex flow inside a co-axial flow control valve with various piston configurations was performed. A transparent full-scale prototype of a control valve was installed into an instrumented flow loop. The acrylic test article allows optical access for diagnostics, such as flow visualization and Particle Image Velocimetry (PIV). Global performance was assessed in terms of the valve flow coefficient for various piston configurations in the control valve at various flow rates by measuring the pressure drop across the valve using an electronic manometer. These results were compared to those for conventional control valves, and as expected, the co-axial design exhibited considerably lower losses (up to 30 times lower). However, the differences in piston geometry designed for different valve characteristics, such as linear, fast-opening, etc. led to different flow coefficients. Investigation of the mechanisms leading to the differences in the global performance involved PIV measurements of the velocity field in several planes within the valve. Complex piston geometries caused regions of separated flow and vortical structures to form. Companion computational studies were performed for the same valve geometries as installed in the flow loop using a commercial CFD package, FLUENT. A fully 3-D Reynolds Averaged Navier-Stokes (RANS) model employing on the order of 800,000 cells was used with a Renormalized Group theory (RNG) k-ε turbulence model. The computational results were compared qualitatively to the experimental data. The CFD results were then used to investigate details of the flow that were not accessible to the experiments, including streamlines, distributions of the static pressure and turbulent kinetic energy throughout the flow field.
Prediction of Boundary-Layer Transition Effects on Turbine Airfoil Profile Losses
Authors: Walters D. Keith , Leylek James H.
Published: May 2008

A previous paper by these authors demonstrated the ability of CFD simulations to accurately resolve profile losses — both with and without film cooling — for a test case in which the airfoil boundary layers were turbulent over the entire airfoil surface. The same paper highlighted the inability of currently available methods to properly resolve losses for cases in which the airfoil boundary layer undergoes transition. This paper presents new CFD results for the identical test case of flow through a linear turbine airfoil cascade. This test case matches an experimental study documented in the open literature, and the measured data is used for validation of the computational results. The Reynolds-averaged Navier-Stokes simulations were performed using a new three-equation eddy-viscosity turbulence model previously developed and documented by the authors. The new model has been developed specifically to provide accurate resolution of boundary-layer transition, without any need for empirical correlations or problem-dependent user input. Results obtained with the new model on the uncooled airfoil show a significant improvement in loss prediction over currently available models that cannot resolve boundary-layer transition. Results for the film-cooled cases show improvement over more traditional models, but highlight the need to incorporate the physics of separated shear-layer transition in addition to attached boundary-layer transition.
Development of a Novel Model System to Study Remodeling of ECM Scaffolds in Response to Cyclic Stretching
Authors: Gilbert Thomas W. , Wang James H.-C. , Badylak Stephen F. , Woo Savio L.-Y.
Published: May 2008

In an effort to better understand the role of mechanical loading on the healing and remodeling of biological tissues, a number of in vitro models have been developed to apply either static or cyclic mechanical load to cell-seeded scaffolds (Huang 1993, Langelier 1999, Cacou 2000). The current study describes the validation of a new system designed to facilitate the study of matrix remodeling in cell seeded scaffolds, as well as the formation of tissue engineered scaffolds for potential use in repair of healing ligaments and tendons. Our objective was to develop a system that would allow a cell seeded scaffold to remain viable under cyclic loading for long periods of time, with the capability to apply complex loading regimes to the scaffold while monitoring the load in the scaffold.
Error Assessment and Error Reduction in Production-Level RANS-Based Drag Predictions
Authors: Davis Donald W. , Slimon Scot A.
Published: May 2008

Assessments of the effects of several numerical parameters on RANS-based drag prediction accuracy are presented. The parameters include grid cell size adjacent to solid walls, grid stretch ratio, grid stretch transition, artificial dissipation scheme, and artificial dissipation coefficient. Results from extensive parametric studies on a two-dimensional flat plate are reported. Based on the results of these studies, guidelines for high-accuracy drag predictions using both second- and fourth-order accurate, finite-difference-based solvers are proposed. In addition, error assessments obtained with a single grid using second- and fourth-order accurate solutions are compared to multiple-grid Richardson’s extrapolation approaches. The single-grid approach is shown to provide a significant improvement in both accuracy and error assessment relative to the multiple-grid approach.
Biomimetic Compliant System for Smart Actuator-Driven Aquatic Propulsion: Preliminary Results
Authors: Trease Brian P. , Lu Kerr-Jia , Kota Sridhar
Published: May 2008

Biomimetic design takes principles from nature to employ in engineering problems. Such designs are hoped to be quiet, efficient, robust, and versatile, having taken advantage of optimization via natural selection. However, the emulation of specific biological devices poses a great challenge because of complicated, arbitrary, and over-redundant designs. Compliant mechanisms are of immediate appeal in addressing the problem of complex, biomimetic deformation because of their inherent flexibility and distributed compliance. The goal of this research is to develop a biologically-inspired hydrofoil for aquatic propulsion, by assembling planar compliant mechanism building blocks to generate complex 3-D deformations. The building block is a rib structure generated from topology optimization. An ADAMS model is then created to quickly visualize motion and estimate system characteristics. System refinement is achieved through further size and shape optimization of individual ribs. Testing of a single-rib and dual-actuator system is currently in progress. The preliminary results have demonstrated the potential of this combined approach to quickly identify and evaluate new applications that may result from building blocks.
Using an Electrically Scale Model to Evaluate Control Strategy for Damping of Hydraulically Driven Off-Highway Vehicles
Authors: Hansen Michael Rygaard , Andersen Torben Ole , Pedersen Henrik Clemmensen
Published: May 2008

In the current paper the oscillatory nature of nonsuspended vehicles is examined with special reference to skid steer vehicles. For this type of application the oscillations represent one of the main difficulties to be overcome in order to increase marching speed. The basic idea of the control strategy is to accelerate the vehicle when it is pitching forward and vice versa with a view to keep the derivative of the pitch angle substantially zero. Physically, the traction system is employed as the controlling system with the developed torque as the manipulated variable. An accelerometer provides the signal related to the controlled variable. The overall control strategy is evaluated by a scale model that is driven by means of two permanent magnet dc-motors, and then applied to a hydraulically driven skid steer loader.
Turbulent Heat Transfer in a Horizontal Enclosure With a Thin Porous Obstruction in the Middle
Authors: Braga Edimilson J. , de Lemos Marcelo J. S.
Published: May 2008

Turbulent natural convection in a horizontal two-dimensional square cavity, isothermally heated from below and cooled at the upper surface, is numerically analyzed using the finite volume method and a generalized coordinate system. The enclosure has a thin horizontal porous obstruction located at the cavity mid height. Governing equations are written in terms of primitive variables and are recast into a general from. In general, the porous obstruction decreases the heat transfer across the heated walls showing an overall lower Nusselt numbers when compared with those without the same porous obstruction. However, the presence of a porous obstruction. However, the presence of a porous obstruction in a square cavity seems to force an earlier transition from laminar to turbulent regime due to higher generation rates of turbulent kinetic energy into the porous matrix.
Nusselt Number and Temperature Distribution in an Horizontal Cavity Containing a Layer of Porous Material at the Bottom
Authors: de Lemos Marcelo J. S. , Magro Viviani T.
Published: May 2008

Horizontally-layered porous media in enclosures represents an important configuration with many technological applications in mechanical and aerospace engineering. This work presents numerical solutions for flow and heat transfer in square cavities partially obstructed with porous material. The microscopic flow and energy equations are integrated in a representative elementary volume in order to obtain a set of equations valid in both the clear flow region and in the porous matrix. A unique set of equations is discretized with the control volume method and solved with SIMPLE algorithm. Heat transfer enhancement across the porous cavity is calculated as the permeability or the porosity of the porous substrate increase.
Negative Wake and Velocity of a Bubble Rising in a Viscoelastic Fluid
Authors: Pillapakkam Shriram B. , Singh Pushpendra
Published: May 2008

A three-dimensional finite element based numerical method is used to simulate the rise of a bubble in a viscoelastic fluid modeled by the Oldroyd-B model. The rise velocity is studied as a function of the bubble volume on a log-log plot. The dependence of rise velocity on the bubble shape and the viscoelastic properties of the ambient fluid are also investigated. In simulations, rather than a jump in the rise velocity at a critical volume as observed in experiments, we find that there is a steep, but continuous, change in the rise velocity over a very small range of bubble volumes. Interestingly, this steep increase in the rise velocity is exaggerated when a parameter, which is a measure of the polymer concentration, is increased, while keeping the zeroshear viscosity fixed. The wake is ‘negative’ in the sense that the direction of fluid velocity behind the bubble for this parameter range is the opposite of that for a Newtonian fluid.
Dynamic Modeling and Design of a High Frequency Micro Vacuum Pump
Authors: Astle Aaron , Bernal Luis P. , Washabaugh Peter , Kim Hanseup , Najafi Khalil
Published: May 2008

A dynamic model of MEMS-fabricated multistage micro vacuum pumps for use in a highly-integrated chemical monitoring system is described. A thermodynamic analysis shows that in order to meet the performance requirements of the system, the micro pump must be operated at very high frequency of approximately 50 kHz. At these frequencies, dynamic effects and resonances due to the interaction of the valves and the pump cavities can play an important limiting role in pump performance. Dynamical effects can also increase the pressure difference between pump cavities increasing the required actuation voltage. The present dynamic model uses integral forms of the momentum and mass conservation equations. Key components of the model are the viscous and inertial terms of the pump’s “checkerboard” microvalves, which are evaluated using a CFD model of the valves. At low frequencies, the model results show increased mass flow rate with increased frequency in good agreement with a thermodynamic model. Maximum performance is reached at frequencies of the order of the resonant frequency of the micro pump. The model is also used to study the effect of valve timing and operating point on mass flow rate and power consumption at high frequency.
A Novel Approach to a Control Systems Laboratory
Authors: Watkins John M. , O’Brien Richard T.
Published: May 2008

In controls education today, a significant gap exists between the material covered in the typical undergraduate classroom and the skills that students need to be practicing control system engineers. In order to help bridge this gap, a control systems laboratory was developed in the Systems Engineering Department at the United States Naval Academy (USNA) with the following design objectives. The first objective was to provide the students the opportunity to apply control theory to physical systems. The second objective was to develop labs where each student works through the complete control system design process. The third objective was to increase the students’ exposure to sampled-data control. The paper begins with a discussion of the Quanser rapid control prototype development system and laboratory experiments. Modeling and system identification are discussed next. Key areas that areas that are emphasized include the use of a dynamic signal analyzer for frequency domain identification and the identification of Coulomb friction for simulation purposes. A unified approach for root locus and Bode design that is used through out the course is discussed next. Finally, analog and digital controller implementations are discussed.
Melting and Resolidification of a Two-Component Metal Powder Layer Heated by a Moving Gaussian Heat Source
Authors: Chen Tiebing , Zhang Yuwen
Published: May 2008

Melting and resolidification of a subcooled mixed metal powder layer that contains a mixture of two metal powders with significantly different melting points heated by a moving Gaussian heat source is investigated numerically. The phase change is modeled using a temperature-transforming model and shrinkage induced by melting is also taken into account. The problem appears to be steady-state since it is formulated in a coordinate system moving with the Gaussian heat source and the size of the powder is much larger than that of the heat source. The results show that the powder layer thickness, moving heat source intensity and scanning velocity have significant effects on the sintering depth.
Vast DOF Wet Shape Memory Alloy Actuators Using Matrix Manifold and Valve System
Authors: Mascaro Stephen , Asada Harry
Published: May 2008

A system is presented for allowing a large number of fast and powerful actuators to be placed within a compact volume. Shape Memory Alloy (SMA) wires on the order of 0.25 mm in diameter are embedded within a large array of compliant, fluid-filled vessels on the order of 1 mm in diameter. The SMA wires are contracted using resistive heating. However, the fluid flowing through these vessels allows the SMA wires to be rapidly cooled by convection without adding too much weight to the system. Thus the power to weight ratio is still higher than conventional actuators (i.e. greater than 1kW/kg) while the speed of response is significantly higher (greater than 1 Hz) than is normally achievable with dry SMA actuators. By arranging these wet SMA actuators in a two-dimensional matrix, the electric current and fluid flow can be controlled by one-dimensional manifolds of electric switches and fluidic valves located at either end. For a system with N2 actuators, only 2N switches and valves are required, thus making the system easily scalable to a vast number of actuators. This paper presents the design and experimental analysis of a prototype for this system, which contains 16 actuators in a volume measuring only 100 mm × 100 mm × 200 mm. Tendon cables can be attached to each actuator to distribute the actuation to the various extremities of a robot or machine. Each actuator is capable of up to 8 mm linear stroke, generating a force on the order of 10 N. The force can be increased by using a thicker SMA wire or by connecting multiple actuators to a tendon cable in parallel. Even though the actuators are located physically in parallel, they can be connected to a tendon cable in a mechanically serial configuration in order to increase the total stroke by up to 8 times. Although the matrix manifold and valve (MMV) system allows only a subset of the actuators to be addressed simultaneously, this system would be ideal for robots or machines where the number of actuators required is large but only a fraction are needed at any given time.
Shape Optimization of an Artificial Hip Prosthesis With 3D-FEM
Authors: Ishida Toshimasa , Nishimura Ikuya , Higa Masaru , Tanino Hiromasa , Ito Hiroshi , Mtasuno Takeo , Mitamura Yoshinori
Published: May 2008

A multiobjective optimization was used to solve several failure problems of cemented total hip arthroplasty. The objective functions were three; the principal stress in the bone cement, the shear stress of stem/cement interface and cement/bone interface. In the results, the cement stress was reduced by 49%, the stem-cement stress was reduced by 68%, and the cement-bone stress was reduced by 43%, compared with the basic model.
Natural Frequencies of Thick Rotating Annular Discs Using an Integrated Method
Authors: Huang Yuan Mao , Lai C. C.
Published: May 2008

An integrated method that combines the first order plate theory, Hamilton’s principle, the finite element method and the subspace iteration method is used to calculate the natural frequencies of thick rotating annular discs. The shear deformation and the rotary inertia of elastic discs with the uniform thickness are considered. Interactive software is generated for personal computers, and the effects of the disc rotational speed, the ratio of the disc thickness to the disc outer radius and the ratio of the disc inner radius to the disc outer radius on natural frequencies are analyzed. Comparison of calculated natural frequencies of discs shows good correlation with existing data. It is expected that this method can provide more accurate results compared with existing methods.
Thermal Property Measurement of Thin Aluminum Oxide Layers for Giant Magnetoresistive (GMR) Head Applications
Authors: Behkam Bahareh , Yang Yizhang , Asheghi Mehdi
Published: May 2008

In recent years, the magnetic recording storage industry has developed a growing interest in increasing recording density of the magnetic disks. Since dimensions of the recording head read transducer have been scaled down to increase areal density, all other parameters being equal, the energy required to cause damage by an ElectroStatic Discharge (ESD) event is reduced substantially. The reduction of insulator thickness between the leads and shields, to increase linear density, further lowers the threshold for ESD breakdown voltage. This problem will become increasingly acute with use of a large number of new and exotic passivation materials having low dielectric constants and thermal conductivities. The present work characterizes the thermal transport properties of Al2O3 Gap layer, which are essential to address the ESD failure in GMR head. This study provides data for out-of-plane (normal) thermal conductivity of thin Al2O3 layers. Thermal conductivity data is obtained using steady-state Joule heating and electrical-resistance thermometry technique.
Combined Experimental and Theoretical Study of Femtosecond Laser Based Micro/Nano Machining of Ultra Thin Metallic Films
Authors: Chimmalgi Anant , Grigoropoulos Costas P.
Published: May 2008

The effectiveness of ultra-short pulsed laser radiation for high-precision material processing and surface micro-modification, owing to the minimal thermal and mechanical damage, has been shown. Micro/Nano structuring of thin films is gaining widespread importance owing to ever-increasing applications in a variety of fields. The present study details femtosecond laser interaction with ultra thin metallic films at the micro and nano scales. Results of Microablation studies, carried out with an 800nm wavelength, 80fs pulse duration, femtosecond laser focused tightly using a long working distance objective lens, are discussed. A parametric study of single shot ablation and subsequent atomic force microscope characterization of the ablation craters is presented. The formation of elevated convex hillock structures at low laser pulse energies and considerable delamination at higher energies evinces a stress driven modification mechanism. Further, nanostructuring results on thin films carried out with femtosecond laser in conjunction with an atomic force microscope are presented. Various nanofeatures were machined with high spatial resolution (∼10–12nm), flexibility and repeatability by utilizing the local field enhancement in the near-field of the scanning probe tip irradiated with the laser beam. Attempting to understand the modification mechanism and the physics involved, numerical simulation studies were performed to evaluate the field enhancement underneath the tip and the ‘femtosecond laser–thin film’ interaction dynamics in general. Possible applications of thin film structuring may be in the areas of high-resolution nanolithography, controlled nanodeposition, ultra high-density data storage, high-resolution mask production and repair, nanoelectronics, nanophotonics and various nanobiotechnology related applications.
Processing and Simulation of Consolidation of Amorphous Aluminum-Based Powder Material
Authors: Ma Li , Zahrah Tony F. , Fields Richard
Published: May 2008

Amorphous aluminum-based materials are light yet much stronger than conventional materials, which offers opportunities in aerospace applications. However, processing the aluminum-based powder into a bulk amorphous material requires relatively low temperature and high pressure, which presents significant challenges. A two-step approach is being explored to reach the goal of a fully dense bulk amorphous or partially amorphous material. First, isostatic pressing is used to partially consolidate the material. Second, extrusion is used to take the partially dense material to full density. Process models are used to design the extrusion process, including the extrusion ratio and extrusion length, to limit the temperature increase during extrusion as a result of adiabatic heating, and to avoid excessive heating to limit devitrification of the amorphous material. A parametric study of extrusion parameters was completed and processing parameters were recommended. The use of process modeling is aimed at understanding the results from the extrusion experiments and limiting the number of iterations during extrusion.
A Comparison Between Three- and Two-Dimensional Thermal Finite Element Analysis of the Gas Metal Arc Welding Process
Authors: Davoud Mohammad S. , Deng Xiaomin
Published: May 2008

Predictions of transient temperature distributions in welding can help the selection of welding process parameters that minimize residual stresses. A three-dimensional (3D) thermal finite element model of bead-on-plate gas metal are welding (GMAW) is presented and is used to evaluate a cross-sectional, two-dimensional (2D) counterpart model. While the thermomechanical problem of welding is 3D in nature, it is shown that the 2D model can provide temperature field predictions comparable to those of the 3D model, even though the 2D model tends to predict peak temperatures higher than those of the 3D model. Both types of model predictions are compared to welding test measurements.
Weaving Loom Integration in Textile Enterprise
Authors: Hu Xudong , Yuan Yanhong , Shen Weiping
Published: May 2008

Weaving technique represents the development of textile industry. After 25 years of open gate and reform of industry construction, textile manufacturing in China has been developed to a higher level. China had imported many modern weaving machines from Italy, Switzerland, Belgium, Japan, and other countries. The domestic textile machine manufacturers and research institutes developed and manufactured many kinds of shuttleless looms. According to the statistical calculation, the total number of shuttleless looms is more than shuttle looms in use in China currently [1]. The wide use of the shuttleless loom demonstrates a strong technical support to the modernization of textile industry in China. These kind of shuttleless looms are equipped with advanced mechanisms like electronic let-off motion, electronic shedding motion, computer based monitoring, electronic dobby and jacquard machine. They are modern textile machines. Due to the labor denseness of the textile industry and unbalanced development of information technology (IT) in China, the manufacturing organization mode of textile is still old fashioned. Modern machines did not get the most economic and technical benefits. This situation was called “Automation Island”. In this paper, the author will describe his research in the integration of weaving machines through a local net. In the author’s project, which is being supported by the Natural Science Foundation of Zhejiang in China, a research team tries to reform the original computer-based loom controller. The required hardware modification and software programming was added. All looms of the workshop were linked to a central control computer through PROFIBUS to make a local net. Now weaving information of every single loom can be monitored through this central computer. Weaving machine integration is very important textile enterprises. There are a lot of applications using this technology. Web-based (mass customization, MC) customized produce is the future of advanced manufacture. An integrated workshop is a good platform for the enterprisers to expose their business to worldwide market. In this article, the author will discuss effort in this area, including experiments and results.
The Effects of Various Cooling Scenarios on a System of Integrated Circuits
Authors: Minter Dion L. , Pang Ying Feng , Scott Elaine P.
Published: May 2008

The focus of this paper is on the system-level cooling of integrated circuits and the effect of various cooling scenarios on the temperature response. Specifically, this paper addresses the thermal response of a system of integrated circuits when the heat sink fin arrangement and the fan location are varied in order to optimize the effects of conduction and forced-convection heat transfer to cool the system.
The Role of Uncertainty Analysis in Model Validation
Authors: Hills Richard G. , Leslie Ian H.
Published: May 2008

Our increased dependence on mathematical models for engineering design, coupled with our decreased dependence on experimental observation, leads to the obvious question — how do we know that our models are valid representations of physical processes? We test models by comparisons between model predictions and experimental observations. As our models become more complex (i.e., multiphysics models), our ability to test models over the range of possible applications becomes more difficult. This difficulty is compounded by the uncertainty that is invariably present in the experimental data used to test the model, the uncertainties in the parameters that are incorporated into the model, and the uncertainties in the model structure itself. When significant uncertainties of these types are present, evaluating model validity through graphical comparisons of model predictions to experimental observations becomes very subjective. Here we consider the impact of uncertainty and the role of uncertainty analysis in model validation. We focus on uncertainty in the model predictions due to parameter uncertainty, and on experimental uncertainty due to measurement noise. We show that characterizing these uncertainties allows us to use a meaningful metric for model testing that is less subjective than the traditional “view graph norm” or the evaluation of correlation coefficients. We demonstrate this methodology through its application to a model and experimental observations of thermally induced foam decomposition.
Degraded Mode Vehicle Lateral Control Under Fault in Rear Sensors
Authors: Huang Jihua , Tomizuka Masayoshi
Published: May 2008

This paper is concerned with vehicle lateral control for Automated Highway Systems (AHS) studied as a part of the California PATH (Partners for Advanced Transit and Highways) Program. In the PATH lateral control system, magnetometers are installed under both the front and the rear bumpers of the vehicle; these magnetometers measure the lateral deviation of the vehicle relative to the magnets buried along the centerline of each automated lane. Lateral controllers have been designed and tested successfully provided that there is no fault in magnetometers. It has been argued that these controllers are NOT tolerant to the fault in magnetometers. The focus of this paper is the degraded mode lateral control under fault in rear magnetometers. The aim of the controller design is to accomplish adequate performance with the remaining set of magnetometers: the front magnetometers. The effects of the fault are examined, and the significance of the linear time varying (LTV) property of the front magnetometer based vehicle lateral dynamics is recognized. Popular control methods for LTV systems generally involve gain scheduling by switching between several LTI controllers. Such controllers are complicated and it is difficult to prove the stability of the switching mechanism. To derive a simple, effective LTV controller, feedback linearization is applied to approximately cancel out the time varying terms in the plant and to function as a gain scheduler. However, due to the weakly damped zeros of the plant, feedback linearization with state feedback or matched observer state feedback results in weakly damped internal dynamics. In order to tune the internal dynamics, a mismatched observer is designed based on H-infinity optimal control techniques. Experimental results are presented to show the effectiveness of the controller design.
A Novel Maskless Post-CMOS Bulk Micromachining Process
Authors: Chiou Jing-Hung , Dai Ching-Liang , Chen Jen-Yi , Lu Michael S.-C.
Published: May 2008

This work describes a new post-CMOS (Complementary Metal Oxide Semiconductor) bulk micromachining process for fabrication of various microstructures. The important feature of the post-CMOS process is the use of wet etching without an addition mask, to form various microstructures and deep cavities in the silicon substrate. The post-CMOS process starts with wet etching to remove sacrificial layers, which are stacked layers of metals and vias, to expose the silicon substrate. Then, KOH or TMAH solution is employed to etch the silicon substrate to form various deep cavities and suspended structures. Many suspended structures, which include beams, bridges and plates, are fabricated using the standard 0.35-μm SPFM (Single Polysilicon Four Metal) CMOS process and the post-CMOS process. Experimental results reveals that a plate with an area of 200×200 μm2, a bridge with a length of 300μm, and various beams with lengths from 100-μm to 400-μm suspended on a deep cavity were fabricated successfully.
Computer Aided Manufacturing of Marine Propellers by Parallel Kinematics Machine
Authors: Chen Hui , Wang Zhixing
Published: May 2008

Techniques of manufacturing integral marine propellers by Parallel Kinematics Machine (PKM) are discussed in this paper, and complete CAD/CAM steps for manufacturing propellers using UG CAD/CAM system are presented. The designed propeller model is defined by a series of aerofoil sections data, so UG/CAD module are used to create the 3-dimensional model of propeller, and tool paths are generated in UG/CAM module. Vericut is adopted to simulate the tool paths generated by UG/CAM and to check interferences. NC postprocessor for PKM is developed on the basis of UG/Post. It is invoked in UG/CAM and converts tool path data into NC program to drive PKM. Finally, machining experiments based on all the techniques discussed in this paper are made. Not only does it puts forward a new scheme and machine to manufacture marine propellers, but also can push the industrialization and practicality of PKM.
A Distributed Parameter Pseudo Bond Graph for Heat Conduction Modelling: Notion of Cellular Bond Graph
Authors: Nakrachi Aziz , Dauphin-Tanguy Genevieve
Published: May 2008

The paper presents a new procedure for building a pseudo bond graph model representing 1D and 2D heat conduction phenomena, in their distributed parameter form. The heat conduction equation is written in such a way that conjugate variables, temperature T(t,x,y) and heat flow rate Q⃗˙(t,x,y), and their space derivatives appear explicitly in the equation. New conjugations between variables are introduced as (T,div(Q⃗˙)) and (gradT,Q⃗˙). We define new bond graph elements named “distributed C- and R-elements”, and we build a “Distributed Parameter Bond Graph” (DPBG), with a form slightly different from the classical one. The approximation of the space derivatives leads to submodels we call “cellular bond graphs”, new notion which could be compared to the cellular automata. Moreover, we show how this representation enables to easily build classical finite difference or finite volume schemes.
Boiling Performance of Single-Layered Enhanced Structures
Authors: Ghiu Camil-Daniel , Joshi Yogendra K.
Published: May 2008

A study of pool boiling at atmospheric pressure from single-layered enhanced structures was conducted for a dielectric fluorocarbon liquid (PF 5060). The enhanced structures were fabricated in copper with an overall size of 10 mm × 10 mm and 1 mm thickness. Parallel microchannels were cut on the bottom surface. The top surface also had parallel microchannels, aligned 90 degrees to those on the bottom surface. This resulted in an array of pores at the intersection of the microchannels. The structures were included in a natural circulation flow loop, consisting of an evaporator section, connecting tubes and a condenser. The transparent evaporator chamber contained the boiling enhancement structure. A cartridge heater embedded into a square copper rod (9 mm × 9 mm in cross section) provides heat to the enhanced structure from the bottom. The parameters investigated in this study were: a) heat flux (0.5–35 W/cm2); b) confinement (the open top and closed top cases have been studied); c) width of the microchannels (65μm–105μm). The boiling performance of the enhanced structures was evaluated by comparison with that of a flat surface with the same overall dimensions.
Prediction of Rate-Dependent Constitutive Behavior of Pb-Free Solders
Authors: Zhang Qian , Sharma Pradeep , Dasgupta Abhijit
Published: May 2008

This paper examines a potential microscale mechanism that contributes to rate-dependent creep of Sn3.9Ag0.6Cu Pb-free solders. The experimentally measured transient and steady-state creep constitutive properties are first presented. Empirical constitutive models are derived, based on this data. Finally, a microstructural model, based on thermally activated dislocation detachment, is explored as a possible source of the creep behavior. This approach explicitly includes microstructural features such as grain size, particle size, particle spacing, etc. The model is calibrated by using the steady-state creep test results to estimate the dislocation density as a function of the stress and temperature. The behavior of the model is explored for different dispersoid sizes as the particle sizes of Cu6Sn5 and Ag3Sn intermetallics are known to vary between 5 and 50 nm [Wiese, et. al., 2001]. The results indicate that dislocation detachment can only dominate over a limited range of particle sizes and stress magnitudes at each temperature. Other competing rate-governing mechanisms are Coble creep at low stresses and dislocation climb at high stresses.
A Study of the “Optimum” Hybridization Ratio for SUVs and Heavy Trucks
Authors: Madireddy Madhava R. , Kremer Gregory G.
Published: May 2008

In conventional vehicles the entire power is derived from the IC engine, so it is obligatory to size the engine larger than necessary for its cruising speed. The engine must be designed to account for peak power requirements like acceleration. This oversizing of the engine shifts the operating point from its efficient zone and this adversely affects the fuel economy and emissions. The idea of hybridization is that a part of the total power required can be replaced by an auxiliary power source, generally a motor powered by batteries. Hence, the IC engine can be designed for average load and can be operated with better fuel efficiency. A simulation tool called ADVISOR (Advanced Vehicular Simulator) is used for this study. The software takes the vehicle input and the drive cycle from the user, simulates the vehicle drive and gives fuel economy, acceleration performance and emissions. In this study, each of the three vehicle platforms (average SUV, full size SUV and heavy truck) is selected and a reasonable power level for that vehicle platform is taken from the data of the current conventional vehicle type. The powertrain is then hybridized by replacing part of the total power by an equivalent motor power and a set of simulations are run in ADVISOR at three different battery charge capacities to understand the effect of on-board charge. A weighted combination of performance and fuel economy results is recorded for each run, and the simulations are then repeated at a higher level of hybridization. The results for a range of “percent hybridization” levels are then evaluated to determine the optimum level. A cost optimization is also done by adding weighted factors based on cost effect of the motor, batteries, and the projected lifetime fuel costs. The penalty due to the weight of the batteries is reflected in the simulated performance and fuel economy of the vehicle, and the space effect of the batteries is also considered. The results of this thesis support the conclusion that parallel hybridization of the drive train could help SUVs and heavy trucks to improve fuel efficiency. Depending on the assumptions made for replacement battery costs and total mileage over the lifetime of the vehicle, the increased initial cost of a hybrid SUV can be justified by the operating cost savings; the benefits of hybridization are even more pronounced for heavy trucks. The “optimum” hybridization percentages are reported for each platform, with and without cost considerations.
Experimental Study on the Possibility of Electric Power Generation by Using a Thermosyphon System
Authors: Hosokawa Tsutomu , Tomita Masafumi , Sakamoto Isamu , Omura Masaru
Published: May 2008

Generally, a thermosyphon is utilized as a heat exchanger. Then, it is an effective equipment for one of the solutions of today’s resource conservation and saving energy problems. The thermosyphon is able to transport heat between small temperature gradients without the need for the outside power. The system has three parts, an evaporator zone, adiabatic zone and condensed zone. The efficiently cycle of the thermal hydraulics system observed in the three zones of this thermosyphon is structurally examined for energy-conversion. The authors installed a power generator in the insulation zone of the thermosyphon, and examined the possibility of electric power generation and the heat transfer characteristics of the thermosyphon. The adiabatic zone was made of an acrylic tube. A turbine and a nozzle were set in the adiabatic zone. Water was used as working fluid. As a result, we confirmed that the output of the electric power and the heat transport rate of about 70–90% for this system were obtained.
Parametric Control of Combustion Thermo-Acoustic Instabilities
Authors: Al-Masoud Nidal , Singh Tarunraj
Published: May 2008

In this paper, a theoretical analysis and syntheses of a parametric controller for thermo-acoustic combustion instabilities in a liquid-fueled propulsion system is developed. A generalized wave equation describes the dynamic behavior of second order nonlinear oscillations. The control algorithm is developed based on the first two modes using the time-averaged simplification of the governing coupled nonlinear system equations. The closed loop control law design is based on finding an optimal phase angle such that the heat release produced by secondary oscillatory fuel injection is out of phase with the mode’s pressure oscillations, and on finding the limits on the controller gain, to ensure the system stability. Theses gains are then optimized using three different performance indices, namely, integral of the time absolute error, ITAE, integral of the absolute error, IAE, and finally, integral of square of the error, ISE. Simulations illustrate the proposed technique capability to effectively attenuate the unwanted oscillations.
Consolidating Electrorefined Spent Nuclear Fuel Waste: Analysis and Experiment
Authors: Bateman K. J. , Capson D. D.
Published: May 2008

Argonne National Laboratory has developed a process to immobilize waste salt containing fission products, uranium, and transuranic elements as chlorides in a glass-bonded ceramic waste form. This salt was generated in the electrorefining operation used in the electrometallurical treatment of spent EBR-II fuel. The ceramic waste process culminates with an elevated temperature operation. The processing conditions used by the furnace, for demonstration scale and production scale operations, are to be developed at Argonne National Laboratory. To assist in selecting the processing conditions of the furnace and to reduce the number of costly experiments, a finite difference model was developed to predict the consolidation of the ceramic waste. The model accurately predicted the heating as well as the bulk density of the ceramic waste form. The methodology used to develop the computer model and a comparison of the analysis to experimental data is presented.
A Study of Unsteady Natural Convection in Cryogenic Storage Tanks for Densified Propellants
Authors: Manalo L. , Akyuzlu K. M.
Published: May 2008

A two-dimensional, unsteady, two domain (liquid and vapor) mathematical model is adopted to investigate the thermo-hydrodynamic behavior of a propellant in a cryogenic storage tank. The physics based mathematical model consists of conservation of mass, momentum, and energy equations for the liquid subjected to variable boundary conditions at the liquidvapor interface and constant heat flux boundary condition at the walls of the container. The density of the liquid is assumed to be temperature dependent only in the buoyancy term of the momentum equation (Boussinesq approximation). The vapor in the ullage is assumed to be an ideal gas with uniform thermodynamic properties and is modeled by single node conservation equations for mass and energy. The two domains are coupled through a set of interface equations for mass and energy exchange between the liquid and the vapor. The resulting nonlinear governing equations for the liquid domain are solved by an implicit finite difference technique (where the pressure distribution is determined by solving the Poisson’s equation) to predict the transient temperature and velocity fields inside the propellant. The equations for the vapor are solved by a simple explicit finite difference technique. The model is tested for a benchmark case (numerically and experimentally) to verify the accuracy of the numerical scheme. Finally, the model is used to predict the transient circulation patterns and resulting thermal stratification in a densified cryogenic propellant for a constant wall heat flux boundary condition.
Impulsive Forming of Shell Structures With Apertures
Authors: Sabelkin V.
Published: May 2008

Different modern shell structures are exposed to impulsive loading very often. Some of them may have different imperfections such as apertures, welds, and irregular thickness. These structures can be made by static or impulsive loading. To know fractureless dynamic response of shell structures with apertures is important in many cases, especially for forming processes, because of the first appeared fracture can extend through a shell blank especially if material is brittle with low plastic properties. The tooling for impact and static loading of flat and shell structures was developed. Dynamic response of shell structures with unsupported apertures on internal impulsive loading by point high explosive charges is described. Strain state of shaped shell structures with apertures after explosive forming is shown. The limit aperture diameter for dynamic fractureless response is determined. Distributions of strain intensities on a sample cross section for different aperture diameters, static and dynamic loading are shown. Different jet engine parts were made using developed technology.
Event Data Recorder Pre-Crash Data Sources for General Motors Vehicles
Authors: Steiner John C.
Published: May 2008

The Event Data Recorder (EDR) found in some 1994 model year and newer General Motors (GM) passenger vehicles has the ability to record up to five seconds of pre-crash data. Such as vehicle speed, engine speed, percent throttle application and brake application before a predetermined deceleration event as well as crash data such as delta-v’s. The pre-crash and crash data can be downloaded by properly equipped and trained personnel using the Vetronix Crash Data Retrieval (CDR) System. However, this data must not simply be taken at face value; the Accident Analyst must be aware of the nature of the differing types and sources of the data, and must ensure that the systems supplying the data was in a normal operating mode and not in a default mode or in a “limp home” mode due to pre existing problems. This paper discusses how different environments and scenarios that the vehicle can be operated in changes how the vehicle will respond to driver inputs thus effecting pre-crash data recorded by the Event Data Recorder.
Experimental Validation of Computer Models for Food and Polymer Extrusion
Authors: Jaluria Yogesh
Published: May 2008

The accuracy and validity of the mathematical and numerical modeling of extruders for polymers and for food are considered in terms of experimental results obtained on typical full-size single and twin-screw extruders. The fluid is treated as non-Newtonian and with strong temperature-dependent properties. The chemical conversion of food during extrusion is also considered. The numerical modeling is employed for steady-state transport, for a range of operating conditions. Following grid-independence studies, the results obtained are first considered in terms of the expected physical behavior of the process, yielding good agreement with observations presented in the literature. The results are then compared with detailed and qualitative experimental results available from previous investigations to evaluate their accuracy. Good agreement with experimental data is obtained, lending strong support to the mathematical and numerical models.