bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Microscopic Voids in Resin Transfer Molded Composites
Authors: Hamidi Youssef K. , Aktas Levent , Altan M. Cengiz
Published: May 2008

Performance of composite materials usually suffers from process-induced defects such as dry spots or microscopic voids. While effects of void content in molded composites have been studied extensively, knowledge of void morphology and spatial distribution of voids in composites manufactured by resin transfer molding (RTM) remains limited. In this study, through-the-thickness void distribution for a disk-shaped, E-glass/epoxy composite part manufactured by resin transfer molding is investigated. Microscopic image analysis is conducted through-the-thickness of a radial sample obtained from the molded composite disk. Voids are primarily found to concentrate within or adjacent to the fiber preforms. More than 93% of the voids are observed within the preform or in a so-called transition zone, next to a fibrous region. In addition, viod content was found to fluctuate through-the-thickness of the composite. Variation up to 17% of the average viod content of 2.15% is observed through-the-thicknesses of the eight layers studied. Microscopic analysis revealed that average size of voids near the mold surfaces is slightly larger than those located at the interior of the composite. In addition, average size of voids that are located within the fiber preform is observed to be smaller than those located in other regions of the composite. Finally, proximity to the surface is found to have no apparent effect on shape of voids within the composite.
Radical Innovative CVT Technology: A Transmission Replacement Example
Authors: Naude Johannes Jacobus
Published: May 2008

Currently the automotive CVT (Continuous Variable Transmission) market is dominated by CVT’s that work on a friction drive principle operating in a traction fluid. This paper presents a new CVT concept based on a unique mechanical joint unit. These units are used in parallel as an intermittent drive to produce a CVT. A mathematical model of the mechanical joint is derived and its suitability to operate within the CVT is discussed. The extension of the ratio range of the CVT via a planetary gear arrangement is demonstrated. The integration of the CVT with AMT (Automated Manual Transmission) technology is discussed and an example of such integration is presented. The efficiency of the system is estimated from related published information. In the summary the advantages of the CVT are discussed by comparison to traction fluid based CVT’s.
Acoustic Properties of Auxetic Foams With MR Fluids
Authors: Scarpa F. , Bullough W. A. , Ruzzene M.
Published: May 2008

This paper presents an experimental investigation on the acoustic properties of novel concepts of auxetic (Negative Poisson’s ratio) open cell polyurethane gray foams. The acoustic absorption coefficients and real and imaginary part of the specific acoustic impedance for the considered foams are measured with an ASTM standard impedance tube using a transmissibility technique. The auxetic foams show a significant increase of the absorption properties in the low frequency range compared to equivalent conventional open cell foams. Their acoustic properties are identified using an empirical model to describe the main structural characteristic. In addition, measurements for auxetic foams seeded with a magnetorheological fluid are also presented. The results show the capability of the seeded foam of shifting the peak acoustic absorption coefficient within a given frequency bandwidth when concentrated magnetic fields are applied.
Fatigue Behavior of VARTM Manufactured Biaxial Braided Composites
Authors: Tate Jitendra S. , Kelkar Ajit D.
Published: May 2008

Braided composites have good properties in mutually orthogonal directions, more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. Another benefit is reduced manufacturing cost by reducing part count. Because of these potential benefits braided composites are being considered for various applications ranging from primary/secondary structures for aerospace structures [1]. These material systems are gaining popularity, in particular for the small business jets, where FAA requires taken off weights of 12,500 lb. or less. The new process, Vacuum Assisted Resin Transfer Molding (VARTM), is low cost, affordable and suitable for high volume manufacturing environment. Recently the aircraft industry has been successful in maufacturing wing flaps, using carbon fiber braids and epoxy resin and the VARTM process. To utilize these VARTM manufactured braided materials to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under different loading and environmental conditions. This will reduce uncertainty and hence reduce the factor of safety in the design. Any typical structural member made of composite material is subjected to different types of loading such as static, impact, cyclic causing fatigue, and environmental effects such as change in temperature and exposure to moisture and other corrosives. It is well known that cyclic loading reduces the strength of a material and its useful life or, the fatigue strength of a material is lower than its static strength. This is true of all materials—metals, plastics, composite materials, etc. In structural applications, fatigue loading is unavoidable especially in aerospace and ground transportation applications. This research addresses the tensiontension fatigue behavior of biaxial braided composites.
Single Pumper Semi-Active Fluid Mount
Authors: Vahdati Nader , Ahmadian Mehdi
Published: May 2008

Passive fluid mounts have been in use in the automotive and aerospace applications for the purpose of cabin noise and vibration reduction since 1940s. Cabin noise and vibration isolation is provided at a frequency coined “notch frequency”. The design location of the notch frequency depends on the application, but with most applications, it is designed to coincide with the longest period of constant speed. To obtain greater cabin noise and vibration reduction at any desired frequency, the notch frequency needs to be as close to that desired frequency as possible. Unfortunately, due to tolerances on all the fluid mount dimensions, material property variations, and variation in elastomer molding processes, the notch frequency never ends up at the right location on the first manufacturing pass. Since none of the passive fluid mount parameters are controllable, the only way to tune the mount is to redesign the mount by changing fluid, changing inertia track length or diameter, or changing rubber stiffness. This trial and error manufacturing process is very costly. To reduce the fluid mount notch frequency tuning cycle time, a new fluid mount design is proposed. In this paper, the new design concept, and its mathematical model and simulation results will be presented.
Mixed Convection of Impinging Air Cooling Over Heat Sink in Telecom System Application
Authors: Alshuqairi Musa S. , Refai-Ahmed Gamal , Agonafer Dereje
Published: May 2008

The current numerical investigation will examine the effect of an impinging mixed convection air jet on the heat transfer rate of a parallel flat plate heat sink. A three-dimensional numerical model was developed to evaluate the effects of the nozzle diameter (d), nozzle-to-target vertical placement (H/d), Rayleigh number and the jet Reynolds number on the heat transfer rates from a discrete heat source. Simulations were performed for a Prandtl number of 0.7 and for Reynolds numbers ranging from 100 to 5000. The governing equations were solved in the dimensionless form using a commercial finite-volume package. Average Nusselt numbers were obtained, at H/d = 3 and two jet diameters, for the bare heat source, for the heat source with a base heat sink and for the heat source with the finned heat sink. The heat transfer rates from the bare heat sources surface have been compared with the ones obtained with the heat sink in order to determine the overall performance of the heat sink in an impingement configuration.
Dynamic Pipe Stresses During Water Hammer: V — Applications
Authors: Leishear Robert A. , Morehouse Jeffrey H.
Published: May 2008

Theoretical equations to describe dynamic stresses during water hammer were developed in the first four parts of this series of papers, and this fifth paper applies those equations to analyze piping failures in a nuclear waste facility. The pipe failures were shown to be coincident to valve closures and pump shut downs, which caused fluid transients in the system. Magnitudes of the pressure increases during the transients were calculated and implemented in dynamic stress analyses for the piping. The maximum pipe stresses were then compared to the fatigue stresses of the pipes, and the failure mechanisms were thus established. By slowly closing valves, the effects of the fluid transient can be nearly eliminated. Using the closed from equations, the minimum time of valve closure may be calculated to prevent recurrent pipe failures. This application of the original closed form solutions provides further insight into the use and validity of the new dynamic stress equations.
System Architecture and Control of Vast DOF Array Actuators
Authors: Cho Kyu-Jin , Asada Harry
Published: May 2008

Systems with a large number of actuators can be built more efficiently by reducing the number of drive amplifiers. System architecture and control strategies of such systems with a reduced number of drive amplifiers are presented. Switch matrix network architecture is used to reduce the number of drive amplifies. The system with network drive architecture has a limited capacity in terms of power related resources. In order to deal with such systems, a limited power resource problem is converted to a problem of transmitting signals through a channel with limited capacity. Pulse Width Modulators change the analog outputs of the conventional controller of each actuator to digital signals, and a Network Modulator encodes those signals into signals suitable for networked drive amplifies. Different control strategies based on different modulation protocols are presented. The performance of the protocol is analyzed with a limit of the duty ratio where the instability occurs.
Airfoil Deformation Analysis During Stator Repair Process
Authors: Alam Shazia M. , Allam Mahdy , Sahay Chittaranjan
Published: May 2008

The compressor stator assembly of a jet engine normally consists of stainless steel and Inconel alloys. Nickel based alloys can be also used as brazing material. Mechanical distortion of the stator assembly components may result during the brazing process. The coefficient of thermal expansion of the component materials, thermal history of manufacturing and operation also contribute to the stator deformation. The purpose of this work is to study the factors causing the distortion in vane stages. The study uses Finite Element Analysis tool ANSYS 5.7 for modeling the engine stator assembly. A finite element structural analysis of a single airfoil model is conducted at various repair points to assess the airfoil deformation and stress levels, before and after the brazing process. It is then used to identify materials and brazing parameters responsible for the observed distortion. The model analyzed shows general agreement between the numerical results and observations from the repair process. The probable causes of distortion are found and recommendations for fixing the distortion problem are also made.
Reducing Noise and Instabilities Produced by the Blades of Rotordynamic Impellers
Authors: Yedidiah S.
Published: May 2008

This paper specifies, discusses, and offers practical solutions to two transient effects which are caused by the motion of the impeller-blades. These are: 1. Noise generated the passage of the impeller-blades past the volute-tongue, and 2. Instabilities which appear at the inlet of an inducer, at reduced flow-rates and low NPSH.
Applying CHP to the Ventilation Air of Buildings
Authors: Cowie Matthew , Liao Xiaohong , Radermacher Reinhard
Published: May 2008

There is a strong industry focus on packaged CHP systems for small scale applications where the design time for unique installations cannot be justified. Distributed generators such as microturbines, reciprocating engines and fuel cells can all now be purchased as CHP products. The development of these products will bring the energy, environmental and economic savings realized in larger applications to the smaller consumers. CHP systems traditionally operate most effectively and give the shortest payback when operated continuously at full output in a baseloading application. This is in conflict with a typical commercial building whose energy requirements vary extensively over daily, weekly and seasonal time periods. Just as CHP is not expected to supply the entire energy requirements of the industrial sector, so CHP should be looked at as merely part of the energy mix for the commercial sector as the capital cost of CHP equipment is typically higher compared to its alternatives and there are technical complications to supply a heating or cooling to power ratio away from design values. An economic CHP system must therefore have a capacity much lower than the peak load of the building to ensure high utilization of the system so that the larger capital investment can be recovered through energy cost savings as quickly as possible. In the absence of a year round continuous demand for either hot or chilled water a commercial CHP system must offer a diverse range of outputs so that the waste heat from the generator can be utilized as mush as possible particularly since the generator component is likely to dominate the capital cost of the installation. This paper proposes that the outdoor, or ventilation air stream into a building provides an excellent capacity match for CHP equipment packaged as a CHP Dedicated Outdoor Air System (CHPDOAS). Ventilation air has the largest temperature and humidity difference with indoor air of any stream of air in the building and so reduces the heat and mass transfer surface areas in the equipment. Also since the ventilation air is only a fraction of the total air flow rate that is being conditioned the CHP system can overcool the air in the summer or overheat the air in the winter and the effect is simply the reduce the cooling or heating workload of the conventional equipment since the ventilation air is then mixed with the bulk of the air remaining in the building before being conditioned. This means that the CHP system can run its generator for longer hours and at higher loads than would have been possible if the outlet conditions were set at space neutral or space supply conditions.
A Computational Study on Mixing of Two-Phase Flow in Microchannels
Authors: Bondar Farshid , Battaglia Francine
Published: May 2008

The passive mixing of water and alcohol, as two fluids with different densities, is carried out computationally in three-dimensional microchannels. Four designs of microchannels are considered to investigate the efficiency of mixing for Reynolds numbers ranging between 6 and 96. In a straight-type microchannel, mixing is very poor. In a square-wave-type microchannel, mixing is marginally better than the straight one. Mixing in the serpentine-type and twisted-type microchannels develops considerable better than the first two microchannels, especially at higher Reynolds numbers. However, in the twisted microchannel, the mixing index is substantially larger compared to the serpentine microchannel for the Reynolds number of 35. The higher mixing index implies the occurrence of spatially chaotic flows with a higher degree of chaos compared to the case of the serpentine microchannel. The results are compared quantitatively and qualitatively in Eulerian and Lagrangian frameworks and a correlation between Lagrangian chaos and Eulerian chaos is concluded.
Computational Modelling of Continuous Casting
Authors: Sinton D. A. , Baliga B. R.
Published: May 2008

Computer simulations of fluid flow and heat transfer phenonmena in a continuous casting process with direct-chill (DC) boundary conditions are presented and discussed in this paper. The investigation is limited to a steady-state, two-dimensional axisymmetric system, used for DC continuous casting of a zero-freezing-range aluminum-magnesium alloy (A6063). An adaptive-grid numerical method is used in these simulations. The grid is designed to delineate the solid-liquid interface using a structured adaptation technique. The fluid flow and thermal fields are predicted using a control-volume finite element (CVFEM). Comparisons of the calculated solid-liquid interface geometries with those reported in earlier experimental and numerical studies are presented in this paper. In addition, the role of natural convection in this casting process is investigated and presented.
Design of an Emergency Egress System for Locomotive Cabs
Authors: Gertler Judith B. , Carter James , Punwani Swamidas
Published: May 2008

Improving the survivability of a locomotive crew in the event of an accident has been a concern of the Federal Railroad Administration in the past decade. Locomotive crashes can injure the crew as well as deform the locomotive cab. Exiting from a deformed cab can be difficult, particularly for injured crewmembers. Egress becomes an even greater challenge if the locomotive is toppled. From an initial list of emergency egress concepts, the following three were chosen for further development: 1) hand/footholds to aid climbing inside a toppled locomotive, 2) roof-mounted escape hatch, and 3) externally removable windshield. As the potential users of the egress system, train crews and emergency rescue workers were interviewed to provide feedback on the design concepts. Focus groups with locomotive engineers and conductors provided information about train crew perceptions of the three concepts. Interviews with rescue personnel provided a perspective on the concerns of emergency rescue operations. Based on the user feedback, the roof-mounted escape hatch with hand/footholds was selected as the preferred concept. Construction of a system mockup facilitated evaluation of this concept. The utility of the overall concept was evaluated using untrained personnel in the full-scale mockup of a toppled road locomotive cab. A preliminary examination of the cost implications of incorporating the hatch system into new locomotives indicated that the initial engineering costs, rather than the recurring manufacturing costs, are the issue. As such, the overall cost for implementing the hatch is likely to be low.
Modeling and Numerical Simulation of Gaseous Flows in Micro Geometries
Authors: Xue Hong
Published: May 2008

In this paper, our recent work in studying gaseous flow and heat transfer in micro geometries are summarized. Both continuum-based approaches and DSMC method is used to predict characteristics of micro flow in slip and transition flow regime. A new analytic solution for micro channel flow is proposed. The results in micro Couette flow, channel flow and backward facing step flow show that the rarefied flow in micro geometries exhibit unique and complicated behaviors. Our efforts in exploring the flow and heat transfer mechanism for micro gaseous flow are useful in broad engineering applications of micro mechanical devices and system.
Analysis of High Frequency Squeal in a Disc-Brake System Using a Stick-Slip Friction Model
Authors: Paliwal Manish , Mahajan Ajay , Filip Peter
Published: May 2008

This paper presents a two degree of freedom (2-DOF) stick-slip friction model for studying the effect of contact stiffness on the stability of the system. It is shown that the stability is not only a function of non-linear variation in the friction force provide by stick-slip but also depends on the variation in stiffness of contact due to the formation of friction layers on the surface of the rotor and the brake pad. Parametric studies have been presented to show the effect of variation in coefficient of friction and contact stiffness on the system stability.
The Theory of Osmosis
Authors: Howlett Larry D.
Published: May 2008

A fresh view for explaining the process of osmosis and the phenomenon of osmotic pressure is presented. The process of osmosis was identified and modeled more than 100 years ago. Others have unsuccessfully challenged the original model developed by J.H. van’t Hoff. We revisit the basic equations and assumptions used in the thermodynamic derivation of the osmosis model. And, we propose a small but significantly different view of the traditional theory of osmosis. From this new view of osmosis and the osmosis experiment, we conclude that osmosis occurs at atmospheric pressure. In cellular membranes, flow from the solvent to the solution is related to the vapor pressure difference determined from the concentration difference with Raoult’s law. Furthermore, we suggest that osmotic pressure as determined from the osmosis experiment is related to both the solution properties and the membrane characteristics. We suggest that the difference between experimental and theoretical determination of osmotic pressure can be attributed to capillary action that may occur in some man made membranes.
A Design Approach to Risk Engineering
Authors: Luthringer Kristin L. , Lalk T. R.
Published: May 2008

This article discuss the characteristics of the risk engineering process that would need to be generated in order to properly bring a designed system to market. First, the current status of risk engineering will be discussed from a design perspective by defining and explaining what is meant by key words such as “risk” and “risk engineering process”. The general goals of the risk engineering process for an example fuel cell-based distributed cogeneration system (FC-Based DCG) will be noted before finally discussing the specific objectives, functions, procedure, & expected results of the risk engineering process for the system.
Performance of a Masterflux Compressor in a Refrigeration Unit for High End Computer System Application
Authors: Makwana Yasin , Agonafer Dereje , Manole Dan
Published: May 2008

The combination of increased power dissipation and increased packaging density has led to substantial increases in chip and module heat flux in high-end computers. Challenge has been to limit the rise in chip temperature above the ambient. In the past, virtually all-commercial computers were designed to operate at temperatures above the ambient. However researchers have identified the advantages of operating electronics at low temperatures. Until recently large scale scientific computers used direct immersion cooling of SCM’s. The current research focuses on mainframe (computer system), which uses conventional system to maintain chip temperatures below that of comparable air-cooled systems, but well above cryogenic temperatures. Multivariable control of compressor speed along with Thermostatic expansion valve opening can give better stability performance. Compressor is the only mechanical-working component in the Refrigeration cycle that circulates refrigerant through the system in a continuous cycle. Hence, the role of a compressor in the unit is significant and should be carefully studied. The control objective is defined as improving the transient behavior of the vapor compression cycle for the Refrigeration System around operating an evaporator set point temperature. The control system can give the better performance stability in regulating Evaporator Temperature. Also the interface temperature (temperature between the evaporator and heat dissipation device) should be maintained within a tolerance range. In this paper, first, the characteristics of the thermostatic expansion valve with the Masterflux compressor, the effect of variation of evaporator outlet superheat on the flow through the TXV at varying evaporator temperature, and effect of sudden changes in evaporator heat load and condenser pressure variation on the temperature oscillations at the evaporator is examined to determine the appropriateness of the compressor for such an application. Once that has been determined, the effect of Multivariable controlled compressor speed working with TXV and the advantages it offers regarding the steadiness of the unit will be reported.
The Kinematic Basis for an Improved Friction Wedge Model
Authors: McKisic A. D.
Published: May 2008

One of the reasons the three-piece truck is the dominant design in the North American freight rail industry is the efficiency of the friction wedge damping system. Even with the proliferation of the system there is a limited understanding of the mechanics of its operation and an absence of mathematical models capable of accurately simulating systems employing friction wedges. This paper presents the kinematic basis for an improved two-dimensional friction wedge model that is capable of more accurately simulating the system.
Performance of a Track Geometry Car-Based Real-Time Dynamics Simulator Using Multiple Vehicle Types
Authors: Bonaventura Clifford S. , Palese Joseph W. , Zarembski Allan M.
Published: May 2008

A real-time dynamic simulation system designed to identify sections of track geometry that are likely to cause unsafe rail vehicle response is discussed. Known as TrackSafe, this system operates onboard a track geometry vehicle where the geometry measurements are passed as inputs to the dynamic model of one or more rail vehicle types. In order to comprehensively analyze the effect of the existing geometry on rail vehicle behavior, the system is capable of simultaneously simulating the response of several vehicle models, each over a range of traveling speeds. The resulting response predictions for each modeled vehicle and each simulated traveling speed are used to assess the track geometry condition and to identify locations leading to potentially unsafe response. This paper presents the latest work in the development of TrackSafe, specifically, the development and testing of eight new vehicle models is presented. The new car types modeled include a box car, flat car, and both a long and short tank car. Each can be simulated in a fully loaded or empty condition. Accuracy of the models is discussed in detail.
An Application of Holographic Interferometry for Nondestructive Vibration and Structural Analysis of High Precision Miniature Mechanical Components
Authors: Fein Howard
Published: May 2008

Advanced Holographic techniques were applied to characterize the behavior and structure of a series of different experimental disk drive suspension arm components. The goal was to determine if dynamic vibration behavior and structural characteristics, as well as certain flaws and anomalies could be identified. The method employed depends on introducing low level, nondestructive structural stresses via vibration and thermal or mechanical actuation which propagate to induce corresponding minute displacements of the structure. Holograms of a various components with different applied vibration, mechanical, or thermal stress geometries are shown to illustrate the analytic comparisons which are made possible employing these techniques.
Advanced Locomotive Propulsion System (ALPS) Project Status 2003
Authors: Herbst John D. , Caprio Matthew T. , Thelen Robert F.
Published: May 2008

The University of Texas at Austin Center for Electromechanics (UT-CEM) is currently engaged in the development of an Advanced Locomotive Propulsion System (ALPS) for high speed passenger rail locomotives. The project is sponsored by the Federal Railroad Administration as part of the Next Generation High Speed Rail program. The goal of the ALPS project is to demonstrate the feasibility of an advanced locomotive propulsion system with the following features: • Operation up to 150 mph on existing infrastructure; • Acceleration comparable to electric locomotives; • Elimination of $3–5M per mile electrification costs; • Fuel efficient operation with low noise and exhaust emissions. The propulsion system consists of two major elements: a gas turbine prime mover driving a high speed generator and an energy storage flywheel with its associated motor/generator and power conversion equipment. The 2.5 MW high speed generator is a three phase, eight pole synchronous machine designed to directly couple to a 15,000 rpm gas turbine. Power from the turbine/alternator system feeds the locomotive dc bus through a conventional full bridge rectifier. The energy storage flywheel features a graphite/epoxy composite rotor operating on active magnetic bearings and is designed to store 480 MJ at 15,000 rpm. An induction motor/generator and variable frequency motor drive provide the link to the dc bus and are used to control power flow into and out of the flywheel. In addition to design and fabrication of the propulsion system components, the project is also developing a distributed control system with power management algorithms to optimize the hybrid propulsion system. Fabrication of the major components of the propulsion system is nearing completion and some preliminary testing of the flywheel and high speed generator has been completed. After completion of the laboratory testing, the propulsion system will be integrated onto a locomotive platform for rolling demonstrations at the Transportation Technology Center test track in Pueblo, Colorado. The paper presents an overview of the propulsion system operation and control strategies, gives detailed descriptions of the major components, and presents component test results.
Revenue Service Demonstration of On-Board Condition Monitoring System
Authors: Donelson John , Zavis Wayne M. , Toth David G. , Punwani S. K. , Stewart Monique Ferguson , Edwards Mark C.
Published: May 2008

The Office of Research and Development of the Federal Railroad Administration (FRA) is sponsoring a project to develop and demonstrate an on-board condition monitoring system for freight trains. The objective of the system is to improve railroad safety and efficiency through continuous monitoring of mechanical components in order to detect defects before they cause breakdowns and accidents. The project, which commenced in June 1999, is part of the Rolling Stock Program Element in FRA’s Five-Year Strategic Plan for Railroad Research, Development and Demonstrations [1]. Science Applications International Corporation (SAIC) and Wilcoxon Research (WR) designed and developed a prototype system in 2000. The prototype system was tested during the period Nov. 2000–Nov. 2001 on a vehicle provided by the Research and Tests Department at Norfolk Southern Corporation. A Revenue Service Demonstration is scheduled to commence in October 2003. The monitoring system will be installed on five coal hopper cars and tested in revenue service. Southern Company Service is providing the test cars. The train will operate on a Norfolk Southern line between a coalmine near Berry, AL and an electric power plant, located 35 miles southeast of Birmingham. The demonstration is scheduled to run for six months. The demonstration will showcase some of the latest technologies in wireless communications and railroad bearings. A tri-mode cell telephone will be used for data telemetry between the on-board monitoring system and a web-accessible database. The Timken Company has developed two innovative systems that will be deployed in the demonstration — a permanent magnet generator mounted inside a Class F railroad bearing and bearing health monitoring system featuring temperature and vibration sensors, a tachometer, a micro-controller and an RF transmitter mounted inside a Class F bearing.
Assessment of Failure Modeling With Thinning Strain Criterion in LS-DYNA
Authors: Cheng Ching-Shan
Published: May 2008

Element deletion based on various failure criteria has been implemented in commercial finite element analysis packages, e.g. LS-DYNA. However, due to the localized and nonlinear nature of the material failure, especially for the ductile materials, a good failure criterion needs to be robust for different mesh definitions and loading conditions. In the present work, the material model with enhanced failure criterion in LS-DYNA, material type 123 (MAT123), is investigated. The equations for determining the parameter of the thinning strain failure criterion are derived based on the assumptions that Yeh et al. [7] proposed. Simulations of different tests using MAT123 with the thinning strain at failure calculated show better correlation with the experimental results than the other material models examined.
Energy Efficient Refrigerators: The Effect of Door Gasket and Wall Insulation on Heat Transfer
Authors: Hessami Mir-Akbar , Hilligweg Arnd
Published: May 2008

The energy efficiency of refrigerators not only depends on the efficiency of the various components used in the cycle but also on their thermodynamics cycle efficiency as well the thermal efficiency of the cabinet housing the components. Efficiency improvements to the thermodynamics cycle and refrigerator components have been the subject of various papers published in the open literature. Not many researchers have looked at reducing the heat leakage into the refrigerator cabinet with the explicit objective of reducing the power consumption of the unit and hence improving its thermal efficiency. This paper is based on an experimental study of this topic, and includes information on the experimental rig used and the results obtained. This research was performed in two stages: The first stage was focused on improving the energy efficiency by changing wall insulation while the second stage was to study the heat transfer through the doors’ gaskets. For the first part, a domestic refrigerator was instrumented with many thermocouples and heat flux meters to measure the inside and outside air temperatures and the heat transfer through the wall of the unit, respectively. These measurements were taken under different environmental conditions as well as different insulation thickness in the walls of the cabinet. For the second part, using a specially designed and manufactured experimental rig, various door gaskets were placed between a warm and a cold chamber and heat transfer through the gasket was measured. The results showed that by adding 30 mm polystyrene insulation to the walls of the refrigerator, the heat transfer through the walls reduced by around 35%. The power consumption data agreed very well with the measured heat flux through the walls. The percentage heat transfer through the doors’ gaskets was confirmed to be about 13% of the total heat transferred into the unit.
A Modeling Analysis of Non-Melting Solid Fuel Particle Heating
Authors: Rostami Ali A. , Wrenn Susan E. , Hajaligol Mohammad R.
Published: May 2008

The heating of fuel particles is generally the first step in the process of gasification or combustion of solid fuels such as coal and biomass. The particle heating that is achieved via combined convection and radiation effects requires a rigorous analysis of heat transfer within as well as outside of the particle, which makes the lumped capacity approximation unsuitable. A more adequate representation of the heating-up process requires the inclusion of the internal convection within the solid particle, the blowing effects on the particle surface, the spatial and temporal variations of the solid thermal conductivity as well as the heat of pyrolysis reactions. The internal convection tends to equalize the temperature distribution within the solid, while the blowing effect contributes to the boundary layer thickening and eventually to a reduction in the convection heat transfer to the particle. To include the above-mentioned effects, a kinetic model for the total weight loss of the solid material was coupled with the heating model. A simple first-order reaction model for the total weight loss was utilized in this study. For materials with high moisture contents, the heat of pyrolysis reactions is an important factor in the heating rate and non-uniform heating of the solid particle. Thermal equilibrium between the solid and evolved gases was assumed within the particle and the equations for the conservation of mass and energy were solved numerically. Results show that surface blowing which is due to the devolatilization of the particle tends to reduce the convection heat transfer from the hot gases to the particle. Internal convection contributes to thermal uniformity in the particle. Heat of pyrolysis reactions plays an important role in the heating profile of the particle. It delays the temperature rise of the particle until most of the volatile materials is released.
Application of a CFD-Based Program for the Optimization of a Centrifugal Impeller
Authors: Pazzi Simone , Martelli Francesco , Giachi Marco , Testa Michela
Published: May 2008

A typical centrifugal impeller characterized by a low flow coefficient and cylindrical blades is redesigned by means of an intelligent automatic search program. The procedure consists of a Feasible Sequential Quadratic Programming (FSQP) algorithm [6] coupled to a Lazy Learning (LL) interpolator [1] to speed-up the process. The program is able to handle geometrical constraints to reduce the computational effort devoted to the analysis of non-physical configurations. The objective function evaluator is an in-house developed structured CFD code. The LL approximator is called each time the stored database can provide a sufficiently accurate performance estimate for a given geometry, thus reducing the effective CFD computations. The impeller is represented by 25 geometrical parameters describing the vane in the meridional and s-θ planes, the blade thickness and the leading edge shape. The optimisation is carried out on the impeller design point maximizing the polytropic efficiency with more or less constant flow coefficient and polytropic head. The optimization is accomplished keeping unaltered those geometrical parameters which have to be kept fixed in order to make the impeller fit the original stage. The optimisation, carried out on a cluster of sixteen PCs, is self-learning and leads to a geometry presenting an increased design point efficiency. The program is completely general and can be applied to any component which can be described by a finite number of geometrical parameters and computed by any numerical instrument to provide performance indices. The work presented in this paper has been developed inside the METHOD EC funded project for the implementation of new technologies for optimisation of centrifugal compressors.
Range Versus Efficiency: A Dilemma for Compressor Designers and Users
Authors: Sorokes James M.
Published: May 2008

The paper describes the compromises that compressor designers must make between peak attainable efficiency and overall operating range. The paper described how component designs such as impellers, diffusers, and return channels impact the balance between efficiency and overall flow range. Similarly, the importance of proper aerodynamic matching of these components within a stage or from stage-to-stage within a compressor is emphasized.
Pilot for a National Detector Database to Enhance Safety and Promote Preventive Maintenance
Authors: Punwani S. , Irani Firdausi , Wiley R. B. , Tunna John
Published: May 2008

The Federal Railroad Administration has embarked on a pilot project to demonstrate the feasibility of using and linking defect detector systems for rail vehicles across North America. The goal of this project is to develop a national database that will enable the railroad industry to engage in predictive maintenance. These detectors measure equipment performance parameters such as the forces between the wheel and rails. The Integrated Railway Remote Information Service or InteRRIS™, an Internet-based system designed and developed by Transportation Technology Center, Inc. (TTCI), was used to aggregate, interrogate, and store data from field-deployed detector systems. TTCI is a wholly owned subsidiary of the Association of American Railroads (AAR). A key task of this program was the determination and implementation of appropriate access to a National Rail Corridor Vehicle Performance Database (VPD). The VPD can draw performance-based data from InteRRIS™ for the FRA and the railroads responsible for the safe operation of cars and locomotives as needed to enable effective performance-based safety monitoring. The VPD has been populated with data from a number of Truck Performance Detectors (TPD) and Wheel Impact Load Detectors (WILD™) in order to capture representative and geographically diverse traffic from freight, mixed freight/commuter/passenger lines, and hazardous materials lines. Both the AAR and FRA have a mutual interest in promoting the implementation of performance-based maintenance. It is hoped that this detector network and associated national database reduces the need for visual inspections on cars and locomotives, thereby focusing more efforts on preventive action and making repairs. This could greatly enhance the efficiency with which railroads make critical repairs in a timely manner. Such tools, with detector data in a central database, should they prove feasible, could eventually lead to the development of performance-based inspection standards.
Industry Focused Courses Utilizing Collaborative Learning Approach
Authors: Honda Hiroshi , Fukuda Shuichi
Published: May 2008

Industry focused, full semester Courses A “Industry and Information Systems” and B “Overview of the Market and Introduction to Marketing” are lectured by the lead author at Tokyo Metropolitan Institute of Technology (TMIT). In these courses, overview of the global and Japanese economies and trends of each industry sector are introduced by the lecturer. Students are assigned to write a report on a specific industry sector, a specific market and other related topics of his or her interest, and opportunities for presentation and discussion on their draft reports with their classmates and the lecturer are given toward the end of the semester. Apart from these courses, a full semester Course C “Evolution of Industry, Business and Engineering Practice in the Global Economy,” utilizing collaborative learning approach, was proposed by the lead author in 1998, and was partially taught at American and Japanese universities, utilizing the Proceedings of the ASME Engineering & Technology Management Group Symposia at IMECE 2000–2002.1)–3) The surveys were conducted concerning the student’s interest of industry sectors, lecture topics, and international topics both at the beginning and at the end of the semester. In addition, surveys to sense students’ new discovery from lectures for all course modules and those to sense useful knowledge in their career planning and in general were conducted at the end of all classes. The results of surveys show that students found the discussion opportunities valuable to gain broader perspectives and insights into their own subject of study when writing their reports, by learning what their classmates are studying and from classmates’ comments. This paper also discusses what motivates students in learning, what influences students’ general, specific, and career interests, and how students’ interests may change from the beginning to the end of the semester for which these courses are given.
Inelastic Behavior of Pipe Subjected to Steady Extension and Cyclic Bending
Authors: Yao Yanping , Lu Ming-Wan , Zhang Xiong
Published: May 2008

The inelastic behavior of a pipe subjected to steady axial force and cyclic bending moment, such as shakedown, plastic fatigue, ratcheting and plastic collapse, is studied. By using two parameters c and d, which indicate the elasto-plastic interfaces of beam cross section, the boundary curve equations between various types of inelastic behavior are derived. The results are suitable for beams of any shaped cross section with two orthogonal symmetric axes. Especially, the load regime diagram for a pipe is obtained, which indicates the elasto-plastic behavior of the pipe under given combination of axial load and cyclic bending moment intuitively.
Multi-Scale Approach for Nonhomogeneous Microstructural Effects on Damage in Particulate Composites
Authors: Cho W. M. , Kwon Y. W. , Liu C. T.
Published: May 2008

This study investigated the effects of random and non-uniform particle distributions on the damage initiation and growth in particulate composites. Numerical specimens with either no crack or an existing crack were examined. For the cases with no crack, the effect of sizes of the representative area for non-uniform particle volume fractions was studied on the overall stress-strain curves and the results were compared with that of the specimen with uniform particle volume fractions. Other studies considered cracked specimens, either single edge crack or a center crack. The global-local approach was used along with multi-scale technique. The global analysis determined the deformations around the crack tip. Then, the local analysis evaluated the damage progress at the crack tip using the solution of the global analysis as boundary conditions. The results showed non-uniformed particle volume fractions in particulate composites caused the crack growth at lower applied loads than the uniform particle volume fraction. Statistical data were also plotted for the non-uniform particle volume fraction cases.
Flow Transients in Wells After Startup of Electrical Submersible Pump
Authors: Fairuzov Yuri V. , Ruiz-Maldonado Oscar , Gonzalez-Guevara Jose , Galindo Augustin
Published: May 2008

Fluid transients in the production system caused by startup of electrical submersible pump (ESP) were studied in the present paper. A numerical model of an ESP well was developed. The system model consists of three modules. The first module, the well model, predicts transient flow in the tubing and the casing. The second module describes the ESP performance characteristics. The third module is a model of single-phase flow in the reservoir. The modules developed are integrated into the whole production system model using an iterative coupling algorithm. The model predictions are compared with field data. The study revealed that the system response on the ESP startup is controlled by dynamic interaction between the well and the reservoir. Model predictions are found to agree qualitatively with field data.
A Scale Analysis Approach to Thermal Contact Resistance
Authors: Bahrami M. , Culham J. R. , Yovanovich M. M.
Published: May 2008

A new analytical model is developed for predicting thermal contact resistance (TCR) of non-conforming rough contacts of bare solids in a vacuum. Instead of using probability relationships to model the size and number of microcontacts of Gaussian surfaces, a novel approach by employing the “scale analysis methods” is taken. It is shown that the mean size of the microcontacts is proportional to the surface roughness and inversely proportional to the surface asperity slope. A general relationship for determining TCR is derived by superposition of the macro and the effective micro thermal resistances. The present model allows TCR to be predicted over the entire range of non-conforming rough contacts from conforming rough to smooth Hertzian contacts. It is demonstrated that the geometry of heat sources on a half-space for microcontacts is justifiable and that effective micro thermal resistance is not a function of surface curvature. A comparison of the present model with 604 experimental data points, collected by many researchers during the last forty years, shows good agreement for the entire range of TCR. The data covers a wide range of materials, mechanical and thermophysical properties, micro and macro contact geometries, and similar and dissimilar metal contacts.