bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Supplier Selection for Changing Product Architectures
Authors: Tenneti Bhanumathi , Allada Venkat
Published: April 2008

Today, a noticeable trend in the US industries is the growing reliance of companies on their supply chain to provide competitive components/sub-assemblies with the desired functionality to not only meet current needs and demands but also the anticipated ones of the future. Supplier consolidation through reduction of the total number of suppliers is being widely practiced by many companies. The increasing dependence on a few key suppliers makes supplier selection critical to a company’s success. Another distinct industry trend is shortening of product and technology lifecycles along with market demands for greater product variety. The direct implication of these trends is continually changing product architectures, which the manufacturers and their suppliers have to manage effectively. Thus, manufacturers need to base their supplier selection process on the robustness of suppliers to deliver components that are compatible with changing product architectures along with the other criterion such as price, reliability, quality, delivery time, etc. Supplier robustness, in the context of this paper, is defined as supplier ability to effectively cater to varying product architectures at minimum supplier costs. The current paper proposes an Ant Colony Optimization (ACO) based methodology for robust supplier selection by extending the robust engineering techniques to the supply chain domain. Taguchi’s quality loss concept is used to evaluate how well the individual components/subsystems supplied by the suppliers’ cost-effectively meet the customer needs. The objective is to select suppliers capable of meeting varying product architecture needs over a given planning horizon at optimal costs. The proposed methodology is demonstrated using an example of a cell phone product family.
Applying Information Economics and Imprecise Probabilities to Data Collection in Design
Authors: Aughenbaugh Jason Matthew , Ling Jay , Paredis Christian J. J.
Published: April 2008

One important aspect of the engineering design process is the sequence of design decisions, each consisting of a formulation phase and a solution phase. As part of the decision formulation, engineers must decide what information to use to support the decision. Since information comes at a cost, a cost-benefit trade-off must be made. Previous work has considered these trade-offs in cases in which all relevant probability distributions were precisely known. However, engineers frequently must estimate these distributions by gathering sample data during the information collection phase of the decision process. In this paper, we introduce principles of information economics to guide decisions on information collection. We present a method that enables designers to bound the value of information in the case of unknown distributions by using imprecise probabilities to characterize the current state of information. We illustrate this method with an example material strength characterization for a pressure vessel design problem, in which we explore the basic performance, subtleties, and limitations of the method.
Research on Steer-by-Wire System With Ideal Steering Ratio and 4WS
Authors: Zong Changfu , Mai Li , Hu Bo , Gao Zhenhai
Published: April 2008

This paper has studied the variable steering ratio for steering-by-wire (SBW) based on the 29 DOF vehicle dynamic model, which kept the steering gain of vehicle constant. And the steering ratio varied with the vehicle velocity and hand wheel angles. We have proposed three control strategies for SBW including front wheel control, yaw rate feedback control and yaw rate & acceleration feedback control. We compared these three control methods by simulation and simulator tests. We have researched the forward and feedback control methods in the four wheels (4WS) for SBW system. And compared with 2WS for SBW and the classical 4WS. The results indicated that 4WS for SBW could improve the vehicle handling.
Uncertain Demand Driven Resource Platform Design for a Service Center
Authors: Hariharan Smitha , Allada Venkat
Published: April 2008

Service centers can be viewed as facilities wherein service calls from customers relating to various service families cascade into work packages involving a set of service tasks. A service family is defined as a set of service type variants that have similar or common service tasks and hence may use a common set of resources (called the resource platform) over a given time horizon. In this paper, we present a methodology for determining cost-effective and robust resource platform configuration(s) for a given set of service families offered by a service center. The robust resource platform would be able to handle demand fluctuations from various service types within reasonable limits over a given planning horizon. Several successful studies have been reported in the manufacturing domain on successful application of product platforms to generate customizable product variants with cost advantages. In this paper, we extend the product platform concept to the service domain. The critical parts of the proposed Service Resource Platforming System (SRPS) methodology are: (1) generate rough cut resource selection using dynamic programming and create a resource schedule using linear programming; (2) generate final resource selection using uncertainty linear programming model proposed by Ben-Tal et al. (2003); and (3) construct resource platform using resource sub-sequence clustering concept. The objective for the rough cut and final resource selections is the maximization of the difference between the benefits and costs associated with in-house service processing and outsourcing. The proposed SRPS methodology is applied to an industry motivated problem.
A Novel Batch Production Technique of Metal Embedded Thin Film Microsensors for Applications in Manufacturing
Authors: Datta Arindom , Choi Hongseok , Li Xiaochun
Published: April 2008

Effective monitoring and diagnosis of manufacturing processes is of importance in reducing operation costs, improving product quality, and reducing process time. If conditions of manufacturing tools are continuously monitored, problems can be detected and solved during the processing cycle, resulting in less tool damage, higher productivity, and less energy consumption. In-situ monitoring of the basic operating conditions (e.g. temperature and strain) of certain mechanical tools and components can be accomplished by placing microsensors in some critical locations. Thin film microsensors (e.g. thermocouple, strain gauge) have drawn considerable attention recently due to their small size, fast response and lower cost [1]. Since most tools and components in manufacturing process are metallic, metal embedded thin film microsensors are very attractive. A new batch fabrication technique based on electroplating and wet chemical etching of silicon has been developed. Microsensors were directly fabricated on an etch stop layer grown on silicon wafer. A multilayer dielectric is deposited to insulate sensor areas followed by seed layer deposition, and electroplating a thicker metal layer. After silicon wafer is etched out, the microsensors are transferred from silicon to electroplated metal substrate directly. After plasma etching of the etch stop layer, these sensors can be further embedded into another electroplated metal layer from the top after insulation by dielectric multilayer. Metal embedded strain gauge array was fabricated successfully. Thin film Ni/Cr strain gauges were fabricated on LPCVD silicon nitride layer grown on a 3-inch silicon wafer. Each strain gauge unit was insulated by Al2O3/PECVD SixNy/Al2O3 multilayer before seed layer deposition and electroplating a thick nickel layer on whole wafer. Si wafer was then etched out in KOH solution to transfer all microsensors to electroplated nickel layer. LPCVD nitride layer covering the sensors was dry etched and same multilayer dielectric was selectively deposited over the sensors except pad areas. These microsensors were finally embedded into another electroplated nickel layer leaving the pads uncovered for external connection. This process offers a novel way to realize batch production of metal embedded microsensors for use in hostile manufacturing environment.
A PIV Analysis Around a Thermal Breathing Manikin
Authors: Marr David , Sheth Ritesh A. , Glauser Mark , Higuchi Hiroshi
Published: April 2008

We present a Particle Image Velocimetry (PIV) database on a benchmark test case involving a thermal manikin exposed to a displacement ventilation and a separate breathing only experiment. This database can be used for calibration/validation of Large Eddy Simulation (LES) and unsteady RANS (Reynolds-averaged Navier-Stokes) techniques for prediction of such biological/environmental flows. Since this is also a multipoint database, we can utilize it for application of Proper Orthogonal Decomposition (POD) based low dimensional tools. This is particularly useful in regions of the flow where there are steep gradients. By picking out the energy containing structures of the exhaled and inhaled air of a breathing manikin via the POD, we can observe such structures in this flow as we progress along the breathing waveform. With only a few POD modes we are able to capture the essential structure of the flow field through the breathing cycle. This is important as we try to understand and ultimately control such environments. There are multiple benefits to this research, including CFD validation in the case of the standing manikin, and characterization of the unsteady behavior in the complex flow of the breathing zone using low dimensional tools. While not presented here, this dataset is also being used for a multi-window analysis in order to compare the different spatial scales of the flow.
Velocity Regulation of a Solid Fuel Ramjet Using Neural Networks and Adaptive Sliding Control
Authors: Durali Mohammad , Alemohammad Hamidreza
Published: April 2008

This paper presents velocity control of a Solid Fuel Ramjet (SFRJ) in variable flight conditions. Since SFRJ is classified as an air breathing propulsion system its performance depends on the air flow over the solid fuel. Dynamic modeling of internal ballistics of SFRJ is developed using gas dynamic relations. This results in a set of nonlinear differential equations. The nonlinearity of equations comes from the fact that gas dynamic relations are generally nonlinear and since the value of some ballistic properties of SFRJ are inaccurate, uncertainties are available in dynamic equations. Then, an adaptive sliding controller is designed for velocity regulation of SFRJ. In order to design the controller the dynamic model is first identified using neural networks. Then the identified model is used to design the control system with the concept of sliding surfaces. The results show the effective performance of controller in velocity regulation of SFRJ in variable flight conditions. Also, the controller showed a good performance in disturbance rejection which proves its robustness.
Response of MEMS Devices Under Shock Loads
Authors: Younis Mohammad I. , Miles Ronald
Published: April 2008

There is strong experimental evidence for the existence of strange modes of failure of MEMS devices under shock. Such failures have not been explained with conventional models of MEMS. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. This work presents a model and simulation of MEMS devices under the combination of shock loads and electric actuation, which will shed the light on the influence of these forces on the pull-in instability. Our results indicate that the reported strange failures can be attributed to early dynamic pull-in instability. The results show that the combination of a shock load and an electric actuation makes the instability threshold much lower than the threshold predicted considering the effect of shock alone or electric actuation alone. Several results are presented showing the response of MEMS devices due to half-sine pulse, triangle pulse, and rectangular pulse shock loads of various durations and strengths. The effects of linear viscous damping and incompressible squeeze-film damping are also investigated.
A Fully-Compliant, In-Plane Rotary, Bistable Micromechanism
Authors: Luharuka Rajesh , Hesketh Peter J.
Published: April 2008

A fully compliant bistable micromechanism (hereafter identified as an in-plane rotary bistable micromechanism or IPRBM) is designed to accomplish in-plane rotary motion with two stable positions. The micromechanism consists of four individually bistable mechanisms arranged in a cyclically symmetric geometry about a central proof mass. This class of bistable mechanism can be used in gate valve, optical shutter, and other switching applications. Two classes of IPRBMs are investigated in this paper. The bistable micromechanism size is less than 1 mm and fabricated by electroplating a soft magnetic material — Permalloy (80% Ni, 20% Fe) in a positive photoresist mold. Minimum feature size in the IPRBM, which corresponds to the width of flexible linkages, is 4 μm. The fabricated IPRBMs have been tested for their force-deflection response using an image based force sensing method. The test results were then compared with the simulated results obtained from a finite element model of the IPRBM. The IPRBM are shown to reversibly undergo 10 to 20 degrees of in-plane rotation and required a maximum torque of 1 to 2 μNm depending on the design. The experimental results showed good overall agreement with the design. A comparison within and between the two classes of IPRBM have been completed for three different design cases between which the tether width and aspect ratio was varied. The study showed a relative advantage of slender tethers with high aspect ratio in minimizing out-of-plane deflection. Also, the radial separation of the individual bistable mechanisms is important.
Study of Fracture Behavior of Molybdenum Alloys Using Moire´ Interferometry
Authors: Feng Chuanyu , Kang Bruce S. , Ma Ning , Cooper Bernard R.
Published: April 2008

Molybdenum-based intermetallics are currently being developed for high temperature application (>1000°C) in advanced fossil energy combustion systems. The goal is to maintain the desired high-temperature mechanical properties while also achieving the required high-temperature oxidation/ hot corrosion resistance. In this research, molybdenum alloys were investigated using high temperature moire´ interferometry. Three-point-bending tests were conducted, and detailed fracture behavior around crack tip was investigated at both room temperature and elevated temperature. Grain boundary sliding was observed through high resolution in-plane deformation fields. For each test, a follow-up fractography and microstructural analyses were carried out. Test results showed that molybdenum alloy with silicide has higher toughness and enhanced grain boundary strength at elevated temperature. The effect of oxygen on grain boundary cohesive strength of Mo alloy was also studied using atomistic modeling and simulations.
Regulating a Formation of a Large Number of Vehicles
Authors: Okamoto Akira , Edwards Dean B.
Published: April 2008

Various control algorithms have been developed for fleets of autonomous vehicles. Many of the successful control algorithms in practice are behavior-based control or nonlinear control algorithms, which makes analyzing their stability difficult. At the same time, many system theoretic approaches for controlling a fleet of vehicles have also been developed. These approaches usually use very simple vehicle models such as particles or point-mass systems and have only one coordinate system which allows stability to be proven. Since most of the practical vehicle models are six-degree-of-freedom systems defined relative to a body-fixed coordinate system, it is difficult to apply these algorithms in practice. In this paper, we consider a formation regulation problem as opposed to a formation control problem. In a formation control problem, convergence of a formation from random positions and orientations is considered, and it may need a scheme to integrate multiple moving coordinates. On the contrary, in a formation regulation problem, it is not necessary since small perturbations from the nominal condition, in which the vehicles are in formation, are considered. A common origin is also not necessary if the relative distance to neighbors or a leader is used for regulation. Under these circumstances, the system theoretic control algorithms are applicable to a formation regulation problem where the vehicle models have six degrees of freedom. We will use a realistic six-degree-of-freedom model and investigate stability of a fleet using results from decentralized control theory. We will show that the leader-follower control algorithm does not have any unstable fixed modes if the followers are able to measure distance to the leader. We also show that the leader-follower control algorithm has fixed modes at the origin, indicating that the formation is marginally stable, when the relative distance measurements are not available. Multi-vehicle simulations are performed using a hybrid leader-follower control algorithm where each vehicle is given a desired trajectory to follow and adjusts its velocity to maintain a prescribed distance to the leader. Each vehicle is modeled as a three-degree-of-freedom system to investigate the vehicle’s motion in a horizontal plane. The examples show efficacy of the analysis.
Formation of Highly Aligned Grooves on the Inner Surface of Semi-Permeable Hollow Fiber Membrane for the Directional Axonal Outgrowth
Authors: Long Yu , Zhang Changhong , Zhang Ning , Huang Yong , Wen Xuejun
Published: April 2008

It is generally believed that organized neural architecture is essential for both nervous system development, function, and regeneration. In the absence of guidance cues, regenerating axons may lose their directions and become misaligned, resulting in the formation of neuromas and/or misappropriate connections. To help regenerate axons across damaged regions and guide them to appropriate targets, some bridging devices such as microgrooves are being intensively researched to achieve a better directional axonal growth. This paper reports a novel fabrication process to generate a highly aligned groove texture on the inner surface of semi-permeable hollow fiber membranes (HFMs). HFMs were shown to be one of the most promising results in guiding axonal regeneration [1]. The fabrication process utilized a wet phase inversion procedure with polyurethane as model polymer, dimethyl sulfoxide (DMSO) as solvent, and water as nonsolvent. Data indicated that highly aligned groove texture could be formed on the HFM inner surface by carefully controlling phase inversion conditions such as the polymer solution flow rate, and/or nonsolvent flow rate, and/or polymer solution concentration ratio. The texture forming mechanism is qualitatively explained using a polyurethane (PU)-DMSO-water ternary phase diagram and the process dynamics. Axonal outgrowth on the HFM with aligned grooves showed the highly aligned orientation and improved axonal outgrowth length. This study will eventually lead to a new and effective way to engineer nerve grafts based on a highly aligned three dimensional scaffold for the spinal cord injury and nerve damage treatment.
Capital and Operating Cost as Driving Forces of the First Stage of Heavy Water Production
Authors: Cha´vez R. Hilda , de J. Guadarrama Javier , Herna´ndez-Guerrero Abel
Published: April 2008

The present paper describes the behavior of the capital and operating cost as driving forces for the design of the first stage of enrichment of heavy water production by the Girdler Sulfide (GS) process. A very useful procedure for analyzing a process or control system is by means of the Second Law of Thermodynamics. Determining where the irreversibilities of a process or control systems are generally indicates where the greatest improvements can be made, particularly as they relate to operating cost. Thermodynamic analyses based on the concepts of irreversible entropy increase have frequently been suggested as pointers to sources of inefficiency in chemical processes. Furthermore, this study shows a generalized discussion of the cost with respect to the optimization parameters, it points out where the irreversibilities of the process are located, and provides a generalized discussion from the successful application of the technique.
Investigation of Microporous Coatings and Meso-Scale Structures for Two-Phase Cooling of Electronic Components
Authors: Trautman Mark A. , Tirumala Murli , You S. M.
Published: April 2008

An empirical study of pool nucleate boiling enhanced with a microporous coating was conducted within the context of microprocessor cooling. A thermal test vehicle (TTV) emulated the heat load from a general purpose microprocessor and was used to deliver a non uniform heat flux density distribution at the boiling surface. The TTV was affixed to a copper test coupon that formed the bottom surface of a sealed boiling chamber containing FC-72 at atmospheric pressure. A design of experiments was conducted on multiple test coupons to identify how the microporous coating, the base thickness of the coupon, and the height of small pin fins affect the combined conduction and boiling heat transfer from the test coupon. The data revealed that the presence of the microporous coating was the most significant factor of the three tested and that very short fins (0.5 mm) were sufficient to manage hysterisis in the boiling curve.
VBA/EXCEL: An Alternative Computer Programming Tool for Engineering Freshman
Authors: Naraghi Mohammad H. N.
Published: April 2008

VBA/EXCEL is incorporated in an Engineering Freshman course in computer programming. The course presents generic programming concepts such as variables, arrays, loops, decisions and sub procedures. VBA/EXCEL and Visual Basic are used as the language of choice. This course involves a semester-long project which forces students to research some engineering, mathematics and scientific concepts at the same time as learning computer programming skills. This paper presents a description of this course and sample projects that are suitable for an engineering freshmen course in computer programming.
A Statistical Method to Obtain Material Properties From the Orientation Distribution Function for Short-Fiber Polymer Composites
Authors: Jack David A. , Smith Douglas E.
Published: April 2008

Material behavior of short-fiber composites can be found from the fiber orientation distribution function, with the only widely accepted procedure derived from the application of orientation/moment tensors. The use of orientation tensors requires a closure, whereby the higher order tensor is approximated as a function of the lower order tensor thereby introducing additional computational errors. We present material property expectation values computed directly from the fiber orientation distribution function, thereby alleviating the closure problem inherent to orientation tensors. Material properties are computed from statistically independent unidirectional fiber samples taken from the fiber orientation distribution function. The statistical nature of the distribution function is evaluated with Monte-Carlo simulations to obtain approximate stiffness tensors from the underlying unidirectional composite properties. Examples are presented for simple analytical distributions to demonstrate the effectiveness of expectation values and results are compared to properties obtained through orientation tensors. Results yield a value less than 1.5% for the coefficient of variation and suggest that the orientation tensor method for computing material properties is applicable only for the case of non-interacting fibers.
Enhancing Combustion in a Dump Combustor Using Countercurrent Shear: Part 1 — Nonreacting Flow Control and Preliminary Combustion Results
Authors: Forliti David J. , Behrens Alison A. , Strykowski Paul J. , Tang Brian A.
Published: April 2008

During the last decade, countercurrent shear has been established as an effective flow control technique for increasing turbulent mixing in a variety of flow configurations and operating regimes. Based on the robust mixing enhancement observed for jets and shear layers, the technique appears to have many potential benefits for enhancement and control for turbulent combustion flows. Countercurrent shear flow control has been applied to a planar asymmetric rearward-facing step dump combustor. A nonreacting flow study on the implementation of suction-based countercurrent shear at the dump plane provided insight into the flow control mechanisms. Control of turbulence velocity and length scales occurs through two mechanisms, the development of a countercurrent shear layer near the dump plane, and enhanced global recirculation caused by the removal of mass at the dump plane. Parametric studies on the geometry of the suction slot indicate that the enhancement of the global recirculation zone is the primary mechanism for increasing global turbulence levels within the combustor. Turbulence energy and length scales both increase in a manner such that the spatially-filtered strain rates as measured with particle image velocimetry remain nominally constant, a desirable characteristic for premixed turbulent combustion. Connections will be made to a recent study on fully-developed turbulent countercurrent shear layers showing additional attractive features of countercurrent shear including enhanced turbulent energy production, entrainment, and three dimensionality. Preliminary reacting flow results for the dump combustor operating while burning premixed/prevaporized JP-10 illustrate qualitative changes in the turbulent combustion process within the combustor. The companion paper will describe the quantitative effects of countercurrent shear on the global heat release rates within the combustor.
The Effects of Feeding Configurations to Water Flooding and General Performance of a Proton Exchange Membrane Fuel Cell
Authors: Hasan A. B. Mahmud , Guo S. M. , Ekkad S. V.
Published: April 2008

The performance of a Proton Exchange Membrane Fuel Cell (PEMFC) using different feeding configurations has been studied. Three bipolar plates, namely serpentine, straight channel and interdigitated designs, were arranged in different combinations for the PEMFC anode and cathode sides. Nine combinations in total were tested under different flow rates, working temperatures and loadings. The cell voltage versus current density and the cell power density versus current density curves were obtained. After operating the PEMFC under high current densities, the cell was split and the water flooding in the feeding channels was visually inspected. Experimental results showed that for different feeding configurations, interdigitated bipolar plate in anode side and serpentine bipolar plate in cathode side had the best performance in terms of cell voltage-current density curve, power density output rate, percentage of flooded area in the feeding channels, the pattern of flooding and the fuel utilization rate.
Enhancing Combustion in a Dump Combustor Using Countercurrent Shear: Part 2 — Heat Release Rate Measurements and Geometry Effects
Authors: Behrens Alison A. , Anderson Matthew J. , Strykowski Paul J. , Forliti David J.
Published: April 2008

Research to advance our understanding of the countercurrent shear flow has been conducted, with particular emphasis on those characteristics of countercurrent shear that are beneficial for combustion applications. Studies carried out in a backward-facing step combustor burning prevaporized JP10-air mixtures, have examined the implementation of counterflow as a means to enhance turbulent burning velocities, with the overall objective of increasing volumetric heat release rates and thereby create a more compact combustion zone. The dump combustor is characterized by a nominally two-dimensional primary flow mixture of prevaporized fuel and air, entering a rectangular channel before encountering a 2:1 single-sided step expansion. Flow separation over the sudden expansion and the resulting recirculation set up a countercurrent shear layer downstream of the dump plane and a low velocity zone conducive to flame anchoring. Combustion control strategies aim to increase turbulent kinetic energy and flame three-dimensionality in an effort to increase flame surface area and thus burning rates. A secondary flow is created via suction at the dump plane as a fluidic control mechanism to enhance the naturally occurring countercurrent shear layer. Counterflow is shown to elevate turbulence levels and volumetric heat release rates downstream of the step in the base geometry while concomitantly reducing the scale of the recirculation zone[1]. Modifications to the rearward-facing step geometry are investigated using Particle Image Velocimetry (PIV) under isothermal flow conditions in an effort to extend the near field interaction between the recirculation zone and the incoming primary flow, thus exploiting the benefits of counterflow as seen in the base geometry. Using chemiluminescence, relative heat release rates are shown to increase by 90% with a counterflow level of 6% of the primary flow by mass in the base geometry, and a 150% increase with a counterflow level of 2.4% in the modified step geometry.
A CFD Model for Cargo Compartment Smoke Detection
Authors: Papa Ramon , Pustelnik Marcelo , de C. Santos Luis C.
Published: April 2008

This paper presents a CFD model for fire and smoke generation inside a cargo compartment in case of fire. The model can provide information on smoke transport under various conditions. The flexibility of the model allows the simulation of numerous fire scenarios in a short period of time. The conservation equations of heat, mass and momentum transfer were solved in the FLUENT software suite for an advanced CFD simulation. The model formulation is given in detail including a description of the wall treatment of the equations, which was found to be of major importance for accurate heat transfer predictions. In order to validate the whole procedure, the results of the simulations with FLUENT are compared with experimental data for the 707 cargo compartment and also the results of a CFD code developed by Sandia National Laboratories. In order to verify the sensitivity of the results three successively refined grids were created to allow for a “grid refinement study”. Grid convergence was ensured by comparison of the results on the two finest grids. It is shown that the proposed method provides accurate results.
Braking Impact of Normal Dither Signals
Authors: Badertscher Jeff , Cunefare Kenneth A.
Published: April 2008

Dither control is a method of introducing high frequency control efforts into a system to suppress a lower frequency disturbance. One application of dither control is the suppression of automotive brake squeal. Brake squeal is a problem that has plagued the automotive industry for years. Placing a piezoceramic stack actuator in the piston of a floating caliper brake creates an experimental normal dither system. Many theoretical models indicate a reduction in the braking torque due to the normal dither signal. Using a Hertzian contact stiffness model the loss in friction is due to lowering the average normal force. There are also theories that the dither signal eliminates the ‘stick-slip’ oscillation causing an effective decrease in the friction force. Yet another theory indicates that the effective contact area is reduced, lowering the mean coefficient of friction. A particular approach considering a single degree of freedom friction oscillator predicts a maximum friction reduction of 10%, occurring at the primary resonance of the system. This paper will concentrate on validating this claim by experimentally determining braking torque reduction for a variety of dither control signals. Several dither control frequencies were chosen at system resonances, while others were chosen at frequencies most likely to provide control of the system. These frequencies were chosen based on previous squeal suppression research. The results indicate that dither control frequencies at system resonances have a greater impact on the braking system’s performance. In general, dither control reduces braking torque by no more than 2%.
Experimental Characterization of MFDC/CHC Resistance Spot Welding
Authors: Li Wei , Cerjanec Daniel , Grzadzinski Gerald A.
Published: April 2008

Resistance spot welding is widely used for joining sheet metal materials in the automotive industry. Most of the existing resistance spot welding systems are single-phase AC-based, and with constant current control. The medium frequency DC (MFDC) system with constant heat control (CHC) is new technology in the resistance spot welding industry. This system promises dramatic improvement on the spot weld quality. However, many of the CHC features are still not known and need to be explored. This paper presents an experimental study on a new MFDC/CHC spot welding system. The goal is to characterize the MFDC/CHC welding process in terms of the process parameters, including the target energy level, force, and welding time. Real time process signals such as force, current, and tip voltage were also collected and analyzed to compare with the traditional spot welding process.
Low Velocity Impact of Carbon/Zylon and Carbon/Kevlar Composite Laminates
Authors: Yusuff Kamaldeen , Mahinfalah Mohammad , Salehi-Khojin Amin , Alimi Mohammad
Published: April 2008

The response of composite laminates to low velocity impact at different energy levels for carbon fiber, carbon/Zylon and carbon/Kevlar composites were investigated in this study. The samples consisted of impact-side face sheet having different combination of 8-layer carbon, 6-layer carbon/2-layer Zylon and 6-layer carbon/2-layer Kevlar laminates. Tests were conducted at energy levels of 8J, 15J, 25J, and 50J. The aim of this study was to investigate the impact of adding a high modulus fiber or low modulus fiber to carbon fiber with respect to Low velocity impact at different energy levels. Results and overall conclusions for each of the composite laminates are presented in detail.
On Analog Simulation of Liquid-Metal Flows in Space Rankine-Cycle Power-Systems
Authors: Zhang Nengli , Chao David F. , Sankovic John M. , McQuillen John B. , Lekan John F.
Published: April 2008

In the development of liquid metal Rankine cycle system, experiments using liquid metals generally cannot be conducted on the International Space Station (ISS) or the space shuttles due to a number of issues including safety. Some other fluids must be used to simulate potassium flows in a Rankine cycle. In this paper an analysis for the simulation using surrogate fluids is made. The results of the analysis indicate that single-phase liquid metal flows, either liquid or vapor, can be simulated using surrogate fluids both in ground and space experiments. For two-phase liquid-metal flow, a credible simulation with a surrogate fluid is currently not possible. For the problem of vapor-production efficiency in a boiler, a simulation using a surrogate fluid whose properties are similar to potassium is workable. A high concentration of copper nanoparticles in water (Cu-water nanofluid) is considered a potential possibility for a fluid to simulate liquid-metal turbulent flow and the boiling process. In the final stage of developing the liquid-metal Rankine-cycle system, experimental tests in a subscale liquid-metal system are still indispensable.
Direct Simulation of Transport in Open-Cell Metal Foams
Authors: Krishnan Shankar , Murthy Jayathi Y. , Garimella Suresh V.
Published: April 2008

Flows in porous media may be modeled using either a macroscopic approach, where volume-averaged semi-empirical equations are used to describe flow characteristics, or a microscopic approach, where small-scale flow details are simulated by considering the specific geometry of the porous medium. A direct simulation of the transport in an open-cell metal foam is carried out in the present study using a periodic unit cell. The foam geometry is created by assuming the pore to be spherical. The spheres are located at the vertices and at the center of the unit cell. The periodic foam geometry is obtained by subtracting the unit cell cube from the spheres. Fluid and heat flow are computed in the periodic unit cell. The objective of the present study is to obtain the effective thermal conductivity, pressure drop and local heat transfer coefficient from a consistent direct simulation of the open-cell foam structure. The computed values compare well with the existing experimental measurements and semi-empirical models. The results and the merits of the present approach are discussed.
Rate-Dependent Cohesive Zone Modeling of Unstable Crack Growth in an Epoxy Adhesive
Authors: Makhecha Dhaval P. , Kapania Rakesh K. , Johnson Eric R. , Dillard David A. , Jacob George C. , Starbuck J. Michael
Published: April 2008

This paper presents the development and numerical implementation of a rate dependent fracture model of an epoxy adhesive. Previous mode I fracture tests conducted under quasistatic, displacement controlled loading of an aluminum double cantilever beam (DCB) bonded with the epoxy exhibited unstable crack growth in the adhesive. Results from mode I fracture tests of compact tension specimens made from bulk adhesive at increasing cross head opening speeds are reported in this paper. The compact tension tests results showed a decreasing critical strain energy release rate with increasing cross head speed, with the critical energy release rate at 1 m/s cross head speed equal to about 20% of its quasi-static value. Two rate dependent cohesive zone models are formulated based on the compact tension test data. A cohesive de-cohesive relationship was postulated between the tractions acting across the crack faces and the opening displacement and opening velocity. These rate dependent cohesive zone models are implemented in a interface finite element to model discrete crack growth in the adhesive. The reaction force history from simulation of the DCB test is in good agreement with the test data using only the rate dependent interface element to model the adhesive.
Numerical Study of Temperature and Incandescence Intensity of Nanosecond Pulsed-Laser Heated Soot Particles at High Pressures
Authors: Liu Fengshan , Snelling David R. , Smallwood Gregory J.
Published: April 2008

Histories of temperature and incandescence intensity of nanosecond pulsed-laser heated soot particles of polydispersed primary particles and aggregate sizes were calculated using an aggregate-based heat transfer model at pressures from 1 atm up to 50 atm. The local gas temperature, distributions of soot primary particle diameter and aggregate size assumed in the calculations were similar to those found in an atmospheric laminar diffusion flame. Relatively low laser fluences were considered to keep the peak particle temperatures below about 3400 K to ensure negligible soot particle sublimation. The shielding effect on the heat conduction between aggregated soot particles and the surrounding gas was accounted for based on results of direct simulation Monte Carlo calculations. After the laser pulse, the temperature of soot particles with larger primary particles or larger aggregates cools down slower than those with smaller primary particles or smaller aggregates due to smaller surface area-to-volume ratios. The effective temperature of soot particles in the laser probe volume was calculated based on the ratio of thermal radiation intensities of the soot particle ensemble at 400 and 780 nm. Due to the reduced mean free path of molecules with increasing pressure, the heat conduction between soot particles and the surrounding gas shifts from the free-molecular to the transition regime. Consequently, the rate of conduction heat loss from the soot particles increases significantly with pressure. The lifetime of laser-induced incandescence (LII) signal is significantly reduced as the pressure increases. At high pressures, the time resolved soot particle temperature is very sensitive to both the primary particle diameter and the aggregate size distributions, implying the time-resolved LII particle sizing techniques developed at atmospheric pressure lose their effectiveness at high pressures.
A Transient Single Cylinder Test System for Engine Research and Control Development
Authors: Lahti John L. , Snyder Matthew W. , Moskwa John J.
Published: April 2008

A transient test system was developed for a single cylinder research engine that greatly improves test accuracy by allowing the single cylinder to operate as though it were part of a multi-cylinder engine. The system contains two unique test components: a high bandwidth transient hydrostatic dynamometer, and an intake airflow simulator. The high bandwidth dynamometer is used to produce a speed trajectory for the single cylinder engine that is equivalent to that produced by a multi-cylinder engine. The dynamometer has high torque capacity and low inertia allowing it to simulate the speed ripple of a multi-cylinder engine while the single cylinder engine is firing. Hardware in loop models of the drivetrain and other components can be used to test the engine as though it were part of a complete vehicle, allowing standardized emissions tests to be run. The intake airflow simulator is a specialized intake manifold that uses solenoid air valves and a vacuum pump to draw air from the manifold plenum in a manner that simulates flow to other engine cylinders, which are not present in the single cylinder test configuration. By regulating this flow from the intake manifold, the pressure in the manifold and the flow through the induction system are nearly identical to that of the multi-cylinder application. The intake airflow simulator allows the intake runner wave dynamics to be more representative of the intended multi-cylinder application because the appropriate pressure trajectory is maintained in the intake manifold plenum throughout the engine cycle. The system is ideally suited for engine control development because an actual engine cylinder is used along with a test system capable of generating a wide range of transient test conditions. The ability to perform transient tests with a single cylinder engine may open up new areas of research exploring combustion and flow under transient conditions. The system can also be used for testing the engine under conditions such as cylinder deactivation, fuel cut-off, and engine restart. The improved rotational dynamics and improved intake manifold dynamics of the test system allow the single cylinder engine to be used for control development and emissions testing early in the engine development process. This can reduce development time and cost because it allows hardware problems to be identified before building more expensive multi-cylinder engines.
Flexural Behavior of Biaxial Braided Composites
Authors: Tate Jitendra S. , Kelkar Ajit D.
Published: April 2008

Braided composites have more balanced properties than traditional tape laminates, and have potentially better fatigue and impact resistance due to the interlacing. The natural conformability of biaxial braided tubes makes it the ideal preform for three-dimensional complex components. Braid tube fits on complex components with ease just like pulling socks on feet. Thus cutting, stitching, or manipulation of fiber placement is not needed, as in the use of woven fabrics. Biaxial braided composites find applications in aerospace, automotive, construction, medical, and recreational industry. Some of the products are automobile cross beams, lamp and utility poles, prosthetic limbs, hockey sticks, baseball bats, and bicycle components. Vacuum assisted resin transfer molding (VARTM) is a low-cost manufacturing process with the capability of manufacturing complex parts with higher fiber volume fractions than those from hand lay-up. To utilize the braided composites to the fullest advantage (and hence to avoid underutilization), it is necessary to understand their behavior under flexural, impact, and fatigue loading. Flexural loading is dominant in the above-mentioned applications of braided composites. This research addresses the effect of braid angle on flexural behavior and failure mechanisms of biaxial braided composites manufactured using VARTM.
The ASME Student Design Contest as a Transitional Design Experience
Authors: Choate Robert , Schmaltz Kevin
Published: April 2008

Teams of Mechanical Engineering students at Western Kentucky University (WKU) participate in the ASME Student Design Contest (SDC) as a component of a Junior Design course. The required course activities include a design review, a mock contest at WKU, and project documentation. Students are also given the option of attending the Regional Conference SDC. Over the past two years, every team has participated at the Regional SDC, with 19 of 27 students attending. Both the 2004 and 2005 WKU teams won the regional competition. The Junior Design course uses the SDC as an intermediate component of a Professional Plan developed and implemented by the WKU ME faculty to assure that program graduates have experienced key areas of the engineering profession and demonstrated the ability to perform in a professional manner. The Professional Component consists of Engineering Design, Professional Communications, Professional Tools, and Ethics. Students receive instruction and practice in all four areas at least once per academic year. With the Engineering Design sequence, freshmen individually build an artifact, sophomores function in design teams, and juniors extend the design experience to an external audience. Technical rigor and faculty expectations obviously rise at each level. The goal is for seniors to be prepared to implement an industry-based project subject to realistic constraints and customer needs. As one of the two design projects in the Junior Design course, the SDC provides a structured design experience with an external flavor. Student teams must demonstrate both problem solving under constraints as well as creativity. To reinforce the economic aspects of design, teams are given a budget, and must fund over expenditures themselves. In addition to the design component of the SDC, the project also includes Professional Communications in the form of design reviews and design notebooks, and Professional Tools such as software for communication, CAD and analytical calculations. The 2005 class has been effective producing rapid prototype components of their designs from CAD models. The Junior Design implementation of the SDC has evolved over the past three years guided by ongoing assessment of both the course and the Professional Component program outcomes. The milestones and associated requirements in the ASME SDC project provides a definitive set of deliverables throughout the progression of the semester long experience. Individual and team performance can be monitored and evaluated with timely feedback, and course outcomes map well into program level assessment. This is a strength of the Professional Component framework that allows for building upon previous coursework, assessing student progress, and adjusting course coverage based on prior assessments to assure that graduating ME students are capable of practicing as engineers.