bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer Correlations in an Air-Water Fin-Tube Compact Heat Exchanger by Symbolic Regression
Authors: Pacheco-Vega Arturo , Cai Weihua , Sen Mihir , Yang K. T.
Published: May 2008

In the present study we propose the application of evolutionary algorithms to find correlations that can predict the performance of a compact heat exchanger. Genetic programming (GP) is a search technique in which computer codes, representing functions as parse trees, evolve as the search proceeds. As a symbolic regression approach, GP looks for both the functional form and the coefficients that enable the closest fit to experimental data. Two different data sets are used to test the symbolic regression capability of genetic programming, the first being artificial data from a one-dimensional function, while the second are data generated by previously determined correlations from experimental measurements of a single-phase air-water heat exchanger. The results demonstrate that the correlations found by symbolic regression are able to predict well the data from which they were determined, and that the GP technique may be suitable for modeling the nonlinear behavior of heat exchangers. It is also shown that there is not a unique answer for the best-fit correlation from this procedure. The advantage of using genetic programming as symbolic regression is that no initial assumptions on the functional forms are needed, which is contrary to the traditional approach.
Noise Control of a Chamber Core Cylinder Using Cylindrical Helmholtz Resonators
Authors: Li Deyu , Vipperman Jeffrey S.
Published: May 2008

Previous investigations have determined that the noise transmission into a finite cylindrical structure at low frequencies is dominated by the cavity resonances. Therefore, noise control at the first several cavity resonances for a Chamber Core cylinder can significantly reduce the noise level at low frequencies inside the cylinder. This work explores the feasibility of noise control for the Chamber Core cylinder using cylindrical Helmholtz resonators. The targeted frequencies are the first four cavity resonances. Detailed considerations of the resonant frequency calculation, resonator design, and experimental verification are presented. The effects on the noise reduction spectrum of two closely spaced resonators are experimentally studied. The optimal position of the resonators is also discussed. The noise control results indicate that the Helmholtz resonators can significantly attenuate the noise level at the targeted frequency bands.
Optimization of Shear Driven Droplet Generation in a Microfluidic Device
Authors: Collins John , Tan Yung-Chieh , Lee Abraham P.
Published: May 2008

Hydrophilic and lipophilic interfaces of fluids play an important role in the formation of droplets. A large collection of droplets constitutes emulsions of water dispersive phase into oil continuous phase. Since droplet generation forms the basis of the manufacturing of emulsion, great efforts have been made to understand the science, technological and industrial problems associated with the generation of droplets. This paper presents the optimization of a novel method of droplet generation [1] in a microchannel resulting from the laminar co-flow of water and oil in a T type channel. Water in oil droplets are formed with olive oil (interfacial tension 28mN/m, viscosity 84mPa/s, density 918Kg/m3). At the T-junction, the water stream sent through the middle channel is sheared and cut by the oil stream sent through the outer channel. Competition between interfacial tension and the Laplace pressure at the oil/water interface results in droplets of finite diameter. Fluid properties such as density, viscosity and surface tension and the flow parameters such as pressure, mass flow rate and velocity are varied at the inlets and outlets to optimize size, frequency and periodicity of droplets using CFD-ACE+, a multiphysics modeling tool (CFDRC, Huntsville, AL).
Application of the Extended Kalman Filter to Control of a Shape Memory Alloy Arm
Authors: Elahinia Mohammad H. , Ashrafiuon Hashem , Ahmadian Mehdi , Inman Daniel J.
Published: May 2008

This paper presents a robust nonlinear control that uses a state variable estimator for control of a single degree of freedom rotary manipulator actuated by Shape Memory Alloy (SMA) wire. A model for SMA actuated manipulator is presented. The model includes nonlinear dynamics of the manipulator, a constitutive model of the Shape Memory Alloy, and the electrical and heat transfer behavior of SMA wire. The current experimental setup allows for the measurement of only one state variable which is the angular position of the arm. Due to measurement difficulties, the other three state variables, arm angular velocity and SMA wire stress and temperature, cannot be directly measured. A model-based state estimator that works with noisy measurements is presented based on the Extended Kalman Filter (EKF). This estimator predicts the state vector at each time step and corrects its prediction based on the angular position measurements. The estimator is then used in a nonlinear and robust control algorithm based on Variable Structure Control (VSC). The VSC algorithm is a control gain switching technique based on the arm angular position (and velocity) feedback and EKF estimated SMA wire stress and temperature. The state vector estimates help reduce or avoid the undesirable and inefficient overshoot problem in SMA one-way actuation control.
Relay Feedback PID Tuning of a Parallel Manipulator
Authors: Wang Zhonghua , Surgenor Brian , Mann George
Published: May 2008

This paper demonstrates modified relay feedback PID tuning as applied to a 6-DOF Gough-Stewart Platform (GSP) based parallel manipulator. The nature of the GSP is such that analytical approaches to obtain the PID controller gains do not apply, and a trial and error approach is commonly used. Simulation results demonstrate that a modified relay approach can be successfully applied to the PID tuning of a GSP. The modification involves the weighting of the critical period.
Linear and Nonlinear Stability of Melt Flows in Induction Channels
Authors: Ai X. , Li B. Q.
Published: May 2008

A linear and nonlinear stability analysis is presented of melt flows in induction channels, which are induced by traveling electromagnetic waves. The problem formulation within the framework of magnetodynamics for flow stability studies is discussed. The linear analysis entails the numerical solution of the Orr-Summerfield equation, which is solved by using the high order finite difference technique and combined with the QR method for eigenvalue solutions. The eigenvalue spectrum, the linear stability characteristics and time average Reynolds stresses are obtained from the linear stability analysis. Based on the linear analysis, the nonlinear stability is studied by direct numerical solution of the magnetohydrodynamic equations using the high order finite difference method. Starting from the linear critical Reynolds number, the weakly nonlinear analysis is performed to determine the nonlinear bifurcation phenomena associated with the induction channel flows. Results show that the flow exhibits the typical Hopf bifurcation behavior and the subcritical instability occurs with high perturbation amplitudes.
Apex Seal Design for the MEMS Rotary Engine Power System
Authors: Martinez Fabian C. , Knobloch Aaron J. , Pisano Albert P.
Published: May 2008

Design, modeling, and analysis of a novel in-plane cantilever apex seal for maintaining high compression ratios in a MEMS-based rotary internal combustion engine are presented. This work is part of an effort to create a portable, MEMS-based Rotary Engine Power System (MEMS REPS) capable of producing power on the order of tens of milliwatts and with an energy density better than that of a conventional battery. A Wankel-type rotary engine is advantageous for a MEMS-based internal combustion engine due to its planar geometry, self-valving operation, and few moving parts. Large scale rotary engines typically incorporate a complex apex and face sealing system composed of many parts and involved assembly. A MEMS-based apex seal system can be incorporated as part of the rotor in order to eliminate manual assembly. The seal system must also have a minimal footprint and closely follow the epitrochoid profile in order to effectively integrate with the other engine systems. Based on these objectives, an integrated in-plane cantilever apex seal system can be integrated into the rotor with a small footprint. The first step in the development of the MEMS REPS is an air-powered expander which can be used to demonstrate electrical generator operation, engine rotation, and apex seal operation. The apex seals discussed here are optimized for use in an air-powered expander. A performance analysis of this flexure apex seal design is performed which examines 4 major performance constraints: resonant frequency, strain, pressure, and power dissipation. In addition, the seal design also accounts for fabrication tolerances of thick deep reactive ion etching (DRIE). During operation, dynamic effects due to combustion process and mechanical translation may drive the flexures into resonance, leading to galloping of the cantilever tips. Galloping will result in large leakage paths, thereby, reducing the compression ratio. A 0.25% strain limit is imposed to minimize the effect of fatigue on seal performance. Pre-compressed apex seals are used to counteract forces generated on the apex seal due to a pressure differential. The apex seal is also designed to minimize the power dissipated due to frictional losses. To model the cantilever apex seal, two different loading conditions are examined. One condition is distinguished by point loading at the tip, when contact is made between the seal and housing wall. Another condition is characterized by a distributed loading, due to the changing pressure by both the compression and the combustion events. Analytical models in addition to a finite element analysis were performed.
Impact of Environmental Preconditioning and Composition Parameters on Constitutive Behavior of Underfills
Authors: Islam Saiful , Lall Pradeep , Suhling Jeffrey C. , Johnson R. Wayne
Published: May 2008

The use of underfills in electronic applications is becoming more prevelant with the decrease in package pitch to 0.5 mm and the increase in I/Os. Underfill encapsulation is typically used in flip chip on laminate assemblies to more evenly distribute and minimize the solder joint strains, thus improving thermal cycling fatigue life. The material constitutive and damage behavior of underfills is however poorly understood. Typical underfill material data sheets often do not provide the parameters required for development of accurate predictive models. In this paper a new methodology for preparation of thin uniaxial test samples for mechanical testing of underfills has been used to better understand the non-linear constitutive behavior of underfills. Bulk underfill samples exhibit different behavior because of non-uniform curing and the effect of sample thickness on the response of underfill layers. A microscale tension-torsion testing machine has been used to measure stress-strain, creep, and stress relaxation behavior if several underfills as a function of temperature. Thermal-fatigue reliability response of various permutation of underfill materials have been analyzed using statistical models. The effect of thermal aging, thermal cycling, and moisture preconditioning on the constitutive behavior of materials have been analyzed. Models have been developed to represent the underfill behavior in an operating range of −40 to 125C.
Experimental Investigation and Numerical Simulation of Glass-Silicon Bonding by Localized Laser Heating
Authors: Theppakuttai S. , Shao D. B. , Chen S. C.
Published: May 2008

In this paper, we report a method to bond silicon and glass wafers directly using localized laser heating (pulsed Nd:YAG laser, 1064 nm, 12 ns). Laser energy was transmitted through the glass wafer and absorbed by the silicon wafer, resulting in a localized high temperature area. Pressure was applied upon the silicon and glass wafers to ensure immediate contact and good heat conduction between them. Scanning electron microscope (SEM) and chemical analysis were used to study bonding area and bonding mechanism. Numerical simulation was carried out in parallel using finite element method to predict the local temperature change of both the glass wafer and the silicon wafer during laser heating. The simulation was validated to some extent by the matching of melting time, which was obtained by using an additional probing laser (He-Ne, 633 nm, 20 mW) during the transient melting and re-solidification of the silicon. This bonding process is conducted locally while the entire wafer is maintained at room temperature, making it advantageous over traditional anodic bonding or fusion bonding.
Development of a Reference Enterprise Model for Fixture Design Information Support in Integrated Manufacturing
Authors: Mervyn Fathianathan , Kumar A. Senthil , Hwee Bok Shung , Ching Andrew Nee Yeh
Published: May 2008

A crucial factor in the success of developing integrated manufacturing systems lies in the ability to exchange information among the various computer-aided systems. Although a vast amount of research has been conducted on computer-aided fixture design systems, the need for information exchange between a fixture design system and other manufacturing systems has not been dealt with thoroughly. Models for the exchange of information within an enterprise or within an extended enterprise depend on the functionality and behaviour of individual enterprises. One means of developing an information model for an enterprise is to determine the information requirements by modelling the enterprise. However, this results in a monolithic model that is only applicable to that enterprise. As a solution to this drawback, we describe the development of a reference model for fixture design information support, which can be instantiated to be applied to different types of enterprises. We concentrate on machining fixtures and information form the fixture design domain to other domains.
Thermal Cycling Reliability of Chip Resistor Lead Free Solder Joints
Authors: Islam N. , Suhling J. C. , Lall P. , Shete T. , Gale H. S. , Johnson R. W. , Bozack M. J. , Seto P. , Gupta T. , Thompson J. R.
Published: May 2008

In this study, we have examined the thermal cycling reliability of several lead free chip resistor solder joint configurations. Five sizes of resistors (2512, 1206, 0805, 0603, 0402), 2 temperature ranges (−40 to 125°C and −40 to 150°C), and five different solder types have been examined. The solders include the normal SnAgCu alloy recommended by earlier studies (95.5Sn-3.8Ag-0.7Cu), and several variations that include small percentages of Bismuth and Indium to enhance fatigue resistance. Results have been compared to data for standard 63Sn-37Pb joints.
Thermal Optimization of Microchannel Heat Sink With Pin Fin Structures
Authors: Kim Duckjong , Kim Sung Jin
Published: May 2008

In the present work, a novel compact modeling method based on the volume-averaging technique and its application to the analysis of fluid flow and heat transfer in pin fin heat sinks are presented. The pin fin heat sink is modeled as a porous medium. The volume-averaged momentum and energy equations for fluid flow and heat transfer in pin fin heat sinks are obtained using the local volume-averaging method. The permeability, the Ergun constant and the interstitial heat transfer coefficient required to solve these equations are determined experimentally. To validate the compact model proposed in this paper, 20 aluminum pin fin heat sinks having a 101.43 mm × 101.43 mm base size are tested with an inlet velocity ranging from 1 m/s to 5 m/s. In the experimental investigation, the heat sink is heated uniformly at the bottom. Pressure drop and heat transfer characteristics of pin fin heat sinks obtained from the porous medium approach are compared with experimental results. Upon comparison, the porous medium approach is shown to predict accurately the pressure drop and heat transfer characteristics of pin fin heat sinks. Finally, surface porosities of the pin fin heat sink for which the thermal resistance of the heat sink is minimal are obtained under constraints on pumping power and heat sink size. The optimized pin fin heat sinks are shown to be superior to the optimized straight fin heat sinks in thermal performance by about 50% under the same constraints on pumping power and heat sink size.
A New Role of CFD Simulation in Thermal Design of Compact Electronic Equipment: Application of Build-Up Approach to Thermal Analysis of a Benchmark Model
Authors: Nakayama Wataru , Matsuki Ryuichi , Hacho Yukari , Yajima Kiyoko
Published: May 2008

Computational Fluid Dynamics (CFD) codes have proved their high potential as a tool of thermal design of electronic equipment. However, as the product development cycle is shortened, the CFD-based thermal design needs a new format that allows the packaging designer fast and versatile searches for better design options. The most serious factor that slows the CFD-based design is geometric complexity created by various components packed in a tight space of the system box. In a proposed methodology coined ‘Build-up Approach (BUA)’ CFD simulations are conducted in advance of the start of actual hardware design to develop a body of temperature distribution solutions for possible components placements in the system box. Two algorithms are introduced before and after CFD simulations. One defines the geometric parameters through singular value decomposition (SVD) of components placement patterns, and the other identifies important geometric parameters for thermal management through application of the Taguchi method. A case study was conducted on a simple hardware model (benchmark model) that embodies essential features of portable electronic equipment. The results proved the effectiveness of these algorithms in measuring the relative importance of geometric parameters, and weeding out unimportant geometric details contained in actual equipment.
Application of Cryogenics to Electronics
Authors: Smith Joseph L.
Published: May 2008

One of the impediments to the application of cryogenics to electronic apparatus is the incompatibility of equipment developed for operation in an ambient environment with a cryogenic environment. The need for the development of cooling and packaging concepts optimized for operation at cryogenic temperature is discussed The opportunities for high efficiency cryocoolers for temperatures of 10 K and below are presented. An entropy flow view of refrigerated cooling is presented. The available methods of refrigeration for operating electronic components at cryogenic temperature are outlined briefly. The three-stage modular Collins-cycle cryocooler that is being developed at the MIT and AMTI is described.
A Case Study in Laboratory-Based Online Courses: Teaching CNC Programming
Authors: Higley James B. , McLees David A. , Zahraee Mohammad A.
Published: May 2008

Asynchronous web based instruction, more commonly known as online education or distance learning, has been available for some time. This technology has brought education within the reach of many who would otherwise be unable to attend live classes. Time schedules and distance no longer have a bearing on attending a course. Even group projects are manageable with email and discussion groups. Many courses convert quite well to the online format, and studies have shown that students can learn as much from online courses as from live courses. In many cases, multiple course certificate programs and even some complete degree programs are offered online. As inviting as online courses may be, they do have their limitations, especially classes with a laboratory component. A number of institutions have offered laboratory-based classes in an online format with varying degrees of complexity and success. In some cases, students travel to the institution a limited number of times for extensive laboratory experiences while other institutions use what might best be described as virtual reality based systems. This paper discusses Purdue University Calumet’s first laboratory-based online course, MFET 275, Computer Numerical Control Programming Application. A combination of technologies makes this course successful and effective. Development procedures for this course along with technology used, online pedagogy issues, and course assessment are covered in this paper. Suggestions for future course development complete the discussion.
Energy Absorption Properties of Various Square FRP Tubes
Authors: Okano Masanori , Saito Hiroshi , Nakai Asami , Hamada Hiroyuki
Published: May 2008

In this study, the static and impact energy absorption characteristics and crushing mechanism based on precise cross-sectional observation of crush zone in two kinds of square FRP tube were investigated. The specific energy absorption value of unidirectional tube showed higher value than that of knitted fabric tube in both static and impact test. Energy absorption mechanism changed from central crack progressive mode with fiber fracture to delamination mode without fiber fracture for unidirectional tube, and from central creck progressive mode to collapse mode with large fragments of inner fronds for knitted fabric tube with the change in testing speed from static to impact.
FEM Stress Analysis and Sealing Performance in Non-Circular Flange Connections With Gaskets Subjected to Internal Pressure
Authors: Sawa Toshiyuki , Maezaki Wataru
Published: May 2008

The contact gasket stress distributions of a non-circular flange connection with a compressed asbestos sheet gasket subjected to internal pressure were analyzed taking account a hysteresis of the gasket by using finite element method (FEM). Leakage tests were also conducted using an actual non-circular flange connection with a compressed asbestos sheet gasket under internal pressure. By using the contact gasket stress distributions and the results of the leakage tests, the new gasket constants were calculated. A difference in the new gasket constants between the values obtained from the present study and those by the PVRC procedure was substantial. In addition, a method to determine the initial clamping bolt force (bolt preload) for a given tightness parameter was demonstrated. abstract text here.
Finite Element Stress Response Analysis of Stepped-Lap Adhesive Joints of Similar Adherends Under Impact Tensile Loadings
Authors: Sawa Toshiyuki , Oomori Takahiro , Ichikawa Kohei , Kido Shoichi
Published: May 2008

The stress variations and stress distributions in stepped-lap adhesive joints of similar adherends under impact tensile loadings were analyzed in elastic range using three-dimensional finite element method (DYNA3D). The impact loadings were applied to the lower adherend by dropping a weight. The stress distributions in stepped-lap adhesive joints of similar adherends under static tensile loadings were also analyzed using FEM (MARC). The effects of Young’s modulus of the adherends, the adhesive thickness, and a number of steps in the adherends on the stress variations and the stress distributions at the interfaces between the adherends and the adhesive were examined under both impact and static loadings. As the results, it was found that (1) the maximum value of the maximum principal stress σ1 occured at the outside edge of the butted interface between the adhesive and the lower adherend to which impact loadings were applied; (2) The maximum value of stress σ1 increased as Young’s modulus of the adherends increased; (3) The maximum value of stress σ1 increased as the adhesive thickness decreased, and it increased at the butted parts of joints as the adhesive thickness decreased. The maximum value of stress σ1 increased at the lapped parts of joints as the adhesive thickness increased; (4) The maximum value of stress σ1 increased as the numbers of steps in the adherends increased. The characteristic of the joints under static loadings were also clarified. In addition, the experiments to measure the strain response of joints subjected to impact tensile loadings were carried out using strain gauges. A fairly good agreement was found between the numerical and the measured results concerning the strain responses.
Development of a Small-Scale Collins Type Cryogenic Refrigerator
Authors: Hannon C. L. , Gerstmann J. , Smith J. L. , Brisson J. G. , Traum M. J.
Published: May 2008

The feasibility of a compact, reliable, low-cost, and efficient cryocooler capable of delivering 1 Watt of cooling at 10K using less than 1kW of input power has been demonstrated analytically. The technology promises to provide highly efficient refrigeration for temperatures as low as 4K, and to be particularly beneficial for temperatures below 30K. The technical approach is to apply a high-efficiency thermodynamic cycle to a compact and reliable small-scale system by implementing a modern microprocessor into a mechanically innovative machine. The innovations of the design include “floating” piston expanders and electro-magnetic “smart” valves, which eliminate the need for mechanical linkages and reduce the input power, size, and weight of the cryocooler in an affordable modular design. It is predicted that a three-stage cryocooler operating with 15-bar helium could produce 2W of cooling at 10K while requiring less than 1kW of compressor power. A laboratory prototype is currently under development, with testing to be completed in the Fall of 2003.
Geometrical Inspection Point Reduction Based on Combined Cluster and Sensitivity Analysis
Authors: Carlson Johan S. , So¨derberg Rikard , Lindkvist Lars
Published: May 2008

Analyzing inspection data is an important activity in the geometry assurance process, which provides vital information about product and process performance. Since inspection is related to a significant cost, it is desirable with an intelligent inspection preparation where the motive is to gather as much information as possible about the product and the process with a minimum number of inspection points. In many situations, a large number of inspection points are used despite the fact that only a small subset of points is needed. The reason for this redundancy is that most systems have only a few principal causes affecting groups of variables. In this paper, we use methods of cluster analysis to find these natural groupings of inspection points and to select one representing point from each cluster. Furthermore, if the relationship between some of the process parameters and inspection points are known from experiments or from computer simulations, then the cluster analysis is combined with sensitivity-based reduction. In this way, an efficient reduced inspection plan is built up. The practical relevance of the proposed methodology for reduction is verified on an industrial case study and by computer simulations.
Innovative Applied Research Projects Using Industry Collaboration
Authors: Foroudastan Saeed , Hardymon Linda
Published: May 2008

Partnerships between the Middle Tennessee State University Engineering Technology Department and the local industrial community are well adapted to research and development projects for the students. Resulting interactions between engineering technology programs and industry are advanced in many ways, including long-term partnerships, informal contacts between faculty members and industrial personnel, consulting, and collaboration on training opportunities, discussions, seminars, and teaching programs. Foremost, however, are the many ways students benefit from the related assignments. Through applied research projects, students focus on innovative project developments that provide practical solutions to complex problems. They learn to initiate, design, and implement new initiatives within the university and industrial partnerships and to profit from the opportunities to explore new technologies and practice skills that meet real world challenges. MTSU modified its introductory engineering course to incorporate not only the fundamentals required to the support basic engineering course learning experience, but to include a choice of hands-on design projects. At present, a solar powered vehicle and a moon buggy have been designed, constructed, and entered into national races to test the decisions and capabilities of the projects as a result of this innovative laboratory approach. The laboratory atmosphere centered on these applied research projects features the opportunity to work at the university and/or take advantage of the industrial partner’s equipment and expertise. Partnerships with industry are essential in providing access to the latest equipment and technology. Applied research projects are important for students to gain a much better “sense” of engineering and to progress to higher levels of project interaction that offer design and design problem issues, use of knowledge, physical application, and comprehension of engineering principles.
Development of Virtual Automated Transit System (VATS) Software for Use in Simulation and Feasibility Analysis of BRT
Authors: Solomon Joseph H. , Gonzalez-Mohino Pedro , Amirouche Farid
Published: May 2008

The steps involved in creating automated BRT (Bus Rapid Transit) simulation software with Matlab and Simulink are explained, incorporating CVHAS (Cooperative Vehicle-Highway) Automation systems) technologies. Methods of concise and efficient route definition, realistic passenger flow simulation, engine dynamics, lateral/longitudinal control and overall program structure are suggested.
Dynamics and Active Control of Largely Deflected Active Structures Using the Finite Element Technique
Authors: Wang D. W. , Tzou H. S. , Arnold S. M. , Lee H.-J.
Published: May 2008

This paper focuses on the vibration, sensing and distributed control of laminated electro/elastic nonlinear plate structures based on newly developed nonlinear shell piezoelastic finite elements. The generic governing electromechanical finite element equations for nonlinear piezoelastic shell structures are developed for the curved hexahedral and triangular piezoelectric shell elements based on the layerwise constant shear angle theory. The nonlinear system equations are linearized to enhance computational feasibility. Equations of electric potential output and feedback control force defined in a matrix from are derived. The modified Newton-Raphson method is adopted for nonlinear dynamic analysis of large and complex piezoelectric/elastic/control structures. A finite element code for vibration sensing and control analysis of nonlinear active piezoelectric structronic systems is developed. Standard structural problems involving geometrical nonlinearity are tested to validate the current finite element code and verify the accuracy of the proposed hexahedral and triangular elements. Vibration control of constant-curvature electro/elastic plate structures is studied. Time-history responses of free and controlled largely deflected nonlinear electro/elastic plate systems are presented and nonlinear effects discussed.
A System Level Thermal Analysis of Large Telecommunication Racks
Authors: Yeh L. T.
Published: May 2008

A system level thermal analysis is performed by employing the computational fluid dynamics (CFD) method on a large telecommunication rack. Each rack consists of two identical shelves located on the top-to-bottom orientation. Each shelf includes one fan tray with 6 fans, 3 card cages with a total of 50 printed circuit boards (PCBs). Air enters from the front of the shelf, and then makes a 90-degree turn upwards through PCBs, and finally turns another 90-degree to exit the system from the back of the shelf. The system level analysis is performed independently on each shelf. The main purpose of the analysis is to determine the air flow rate to individual printed circuit boards as well as the air temperature distribution in the system. The computed flow rate for individual PCBs is then used for a detailed board analysis to predict the component temperatures of individual boards.
Stress Analysis of the Polyethylene Component in Total Ankle Arthroplasty: Effect of Thickness
Authors: Galik Karol , Smolinski Patrick , Conti Stephen F. , Miller Mark C.
Published: May 2008

A three-dimensional finite element model was constructed of the distal tibia and fibula and a semi-constrained ankle prosthesis (Agility™ system). Contact elements were used at the interface between the talar component and the polyethylene liner and the proximal tibia and fibular were loaded in the in vertical direction. The minimal thickness of the polyethylene liner was varied from 3 mm to 8 mm in 1 mm increments. The results showed that the liner contact pressure in the sagittal plane mid-line decreased from 20 MPa to 14 MPa with increasing thickness while the medial edge contact pressure increased from 26 MPa to 30 MPa.
Stability of a Spinning Rotor Subjected to a Distributed Traction
Authors: Kang Bongsu
Published: May 2008

In this paper, the stability of a spinning rotor loaded by a circumferentially distributed frictional traction is examined. Typical engineering applications include automotive and aircraft disc brakes and circular saws. The frictional traction, which is always directed tangent to the instantaneous deflection curve of the rotor, is decomposed into in-plane and transverse components. The in-plan component is equilibrated by the in-plane stresses while the transverse component is a slope-dependent nonconservative followertype force that is the major source of dynamic instability of the rotor in this study. The rotor is modeled as a spinning annular plate that includes the effects of rotary inertia and shear deformations in the context of the Mindlin thick plate theory. A thick plate model is employed to ensure an accurate estimation of the eigenvalues when the rotor vibration involves high circumferential modes (eighth or ninth) that are often observed in unstable automotive disc brakes. The pad or stator is represented as a viscoelastic subgrade that reacts to both transverse and shearing motion of the rotor. The degree of instability is measured by examining the resulting complex eigenvalues. Effects of various system parameters such as frictional traction, geometry of the rotor, pad size, spinning speed, and viscoelastic properties of the pad on the dynamic instability are discussed. Results, when compared with those from the classical thin plate model of the rotor, are significantly different.
Dimensional Tolerancing and Control in Molded Products
Authors: Kazmer David , Manek Kaushik , Lotti Cybele , Bretas Rosario E. S. , Zhu Liang
Published: May 2008

Design and manufacturing of engineered products are subject to uncontrolled variation (noise) and unknown performance behavior and/or requirements (uncertainty). Skilled practitioners currently utilize robust design and Six Sigma techniques for tolerance specification and parametric optimization to control the mean and variance of the performance characteristics. Even after several design iterations, however, the final product and process design may not be optimal and result in unacceptable performance or quality levels. This paper explores the validity of current Six Sigma practices for dimensional tolerancing and process optimization in the manufacturing of an injection molded plastic part. Specifically, the use of process capability indices and aggregate performance measures are discussed relative to the shrinkage behavior of isotactic polypropylene, i-PP. The results indicate that uncertainty and covariance between multiple part dimensions can invalidate standard practices. While current best practices may be better than completely unstructured approaches, the resulting product and process designs provide suboptimal product characteristics, broad performance distributions, and low manufacturing yields.
Tolerance Analysis and Synthesis for Composite Assemblies of Resin Transfer Molded Components
Authors: Dong Chensong , Zhang Chuck , Liang Zhiyong , Wang Ben
Published: May 2008

With the increasing demand for composite products to be affordable, net-shaped and efficiently assembled, tight dimension tolerance is critical. Due to lack of accurate process models, dimension analysis and control for resin transfer molding (RTM) processes are often performed using trial-and-error approaches based on engineers’ experiences or previous production data. Such approaches are limited to specific geometry and materials and often fail to achieve the required dimensional accuracy in the final products. This paper presents an innovative dimension variation prediction approach. First a dimension variation model was developed based on process simulation, the classical laminate theory (CLT) and finite element analysis (FEA). The FEA-based dimension variation model was validated against experimental data. The deformations of common features in typical composite structures were analyzed using the FEA-based dimension variation model. Design parameters were identified and the regression-based dimension variation model was developed. The model provides a fast, practical and proactive tool to predict and control dimension variations in RTM processes. The structural tree method (STM) is presented for design optimization and tolerance analysis/synthesis of composite assemblies.
Modeling and Control of Magnetorheological Dampers for Vibration Isolation
Authors: Narimani A. , Golnaraghi M. F.
Published: May 2008

Semi-active isolators offer significant improvement in performance over passive isolators. These systems benefit from the advantages of active systems with the reliability of the passive systems. In this work we study a vibration isolation system with a magnetorheological (MR) damper. The experimental investigation of the mechanical properties of a commercially available linear MR damper (RD-1005-3) was conducted next. The mathematical Bouc-Wen model was adopted to predict the performance of MR damper. In addition, a modified Bingham model has been developed to characterize the damper behavior more accurately and efficiently. The measured hysteresis characteristics of field-dependent damping forces are compared with the simulation results from the described mathematical models. The accuracy of a damping-force controller using the proposed method is also demonstrated experimentally. Finally, a scaled quarter car model is set up to study the performance of the control strategy. The experimental results show that with the semi-active control the vibration of the quarter car model is well controlled.
A Study on the Characteristics of a Nonlinear Oscillatory System With Dry Friction
Authors: Dai Liming , Xu Liang
Published: May 2008

Nonlinear oscillatory system involved with friction is very common in nonlinear dynamics of engineering fields. This paper is to investigate the motions a nonlinear oscillatory system with involvement of dry friction. The cases of weakly and highly nonlinearity of the system are considered. Approximate and numerical solutions for the system are developed via the author’s newly developed P-T method. As demonstrated in the present work, the properties of the weakly and highly nonlinear systems exhibit great differences, though the governing equations of the two systems employ identical system parameters. The approximate solutions developed for the system are continuous everywhere on the time range considered. Under the conditions of weakly nonlinearity, the approximate solutions developed can therefore be conveniently implemented for the purpose of an analytical studying the properties of the system with numerous system parameters and various initial conditions. Taking this advantage, the behavior of motion of the weakly nonlinear system is analyzed and compared with the corresponding solutions developed with Van der Pol’s method. It is found in the present work, the system may undergo a self-excited oscillation under certain conditions. The highly nonlinear system is a physically much involved one. Its behavior is thus much complex in comparing with that of the weakly nonlinear system. Based on the approximate solutions developed for the highly nonlinear system, recurrence relations are generated for numerical calculations. For the sake of comparison with the oscillation of the weakly nonlinear system, numerical simulations for the highly nonlinear system are performed under the same initial conditions and identical system parameters. The conditions of convergence and divergence of the weakly nonlinear system are also established for application. Behavior of the oscillatory motion of the highly nonlinear system is investigated on the basis of the corresponding numerical solutions developed.
An Analytical Model to Predict Chatter in Multi-Dimensional Periodically Time-Varying Machining Processes
Authors: Corpus William T. , Endres William J.
Published: May 2008

An approach is presented to determine the stability limits for machining processes that exhibit periodic time variation and multi-dimensional structural dynamics. The approach leverages the solution for the single-dimensional case, which identified an added set of stability lobes in addition to those corresponding to the time-invariant case. The solution is developed for two-dimensional dynamics for both a damped system and an undamped system; it may be expanded to any order and extended to three-dimensional dynamics. The undamped solution provides a mathematical description of the stability lobe locations along the speed axis and asymptotes for the damped case. Numerical time-domain simulation is used to confirm the analytical solution. While the agreement is good even for a first-order analytical result, yet another extra stability lobe, not seen in the one-dimensional case, is now seen in the numerical simulation results. Some of its characteristics are noted; however, further study is needed to understand its source.
Automotive Hydraulic Valve Fluid Field Estimator Based on Non-Dimensional Artificial Neural Network (NDANN)
Authors: Cao M. , Wang K. W. , DeVries L. , Fujii Y. , Tobler W. E. , Pietron G. M. , Tibbles T. , McCallum J.
Published: May 2008

A conventional automatic transmission (AT) hydraulic control system includes many spool-type valves that have highly asymmetric flow geometry. An accurate analysis of their flow fields typically requires a time-consuming computational fluid dynamics (CFD) technique. A simplified flow field model that is based on a lumped geometry is computationally efficient. However, it often fails to account for asymmetric flow characteristics, leading to an inaccurate analysis. In this work, a new hydraulic valve fluid field model is developed based on a non-dimensional neural network (NDANN) to provide an accurate and numerically efficient tool in AT control system design applications. A “grow-and-trim” procedure is proposed to identify critical non-dimensional inputs and optimize the network architecture. A hydraulic valve testing bench is designed and built to provide data for neural network model development. NDANN-based fluid force and flow rate estimator are established based on the experimental data. The NDANN models provide more accurate predictions of flow force and flow rates under broad operating conditions compared with conventional lumped flow field models. The NDANN fluid field estimator also exhibits input-output scalability. This capability allows the NDANN model to estimate the fluid force and flow rate even when the design geometry parameters are outside the range of the training data.
Temperature Distribution in a Finite Solid Due to a Moving Laser Beam
Authors: Gutierrez Gustavo , Araya Juan Guillermo
Published: May 2008

Laser machining has been gaining a wider field in industrial applications. One of the key factors in this process is to understand accurately the temporal evolution of the temperature field during laser-material interaction, in order to omptimize the input parameters of the process such as laser power and cutting speed. In the present study, a numerical simulation of the temperature distribution generated by a moving laser beam is analyzed in detail for a finite domain. The transient heat conduction is discretized using a control volume approach. The laser source is modeled as a concentrated heat source. Due to high-energy concentration of the laser beam, the region around the laser need to have a finer grid in order to achieve accurate results. A constant grid is generated in the direction of the moving source and a variable grid in the other two directions to obtain a better resolution around the position of the heat source. Radiation and convection effects are also discussed.
A Wavelet-Based Fuzzy Data Fusion Scheme for Bearing Defect Severity Classification
Authors: Sheng Shuangwen , Gao Robert X.
Published: May 2008

This paper presents a fuzzy data fusion scheme for bearing defect severity classification. Instead of using time-domain features (e.g. peak value, root mean square, kurtosis) of the original signal as the inputs, wavelet transform was applied to the original signals as a data pre-processor. Defect-related features were filtered out from the corresponding wavelet coefficients. Next, fuzzifications on individual input features were performed to obtain individual decisions. Finally, data fusion was peformed to achieve an overall bearing defect severity classification. Three data fusion methods: voting, weighted decision, and fuzzy inference, were investigated. Experimental results have shown that the presented fuzzy data fusion scheme is more effective than traditional approaches using raw signals as the input features. In particular, the presented scheme has resolved conflicting decisions arising from single feature-based classification, thus improving the reliability of defect severity assessment.
Discrete Sliding Mode Controller Design Based on the Suboptimal LQR Approach
Authors: Yu Wen-Chun , Wang Gou-Jen
Published: May 2008

A systematic and simple discrete sliding mode controller design scheme based on the suboptimal approach is presented. The behaviors of the control system can be determined through a preferred performance index. The AC servomotor position control is obtained using only the q-axis voltage control loop. The proposed method is simulated and experimented to verify the capability of this new sliding mode control algorithm. Properties such as easy implementation, fast resonse, and robust to external loads are demonstrated.
A Unified Approach for Independent Manipulator Joint Acceleration Control and Observation
Authors: ElBeheiry ElSayed M. , Zaki Ahmed S. , ElMaraghy Waguih H.
Published: May 2008

The ultimate goal of a manipulator control design is to combine the design of both the controller and the observer into one procedural approach. Hence, the stability of the global system, namely, the manipulator dynamics, controller, and observer is guaranteed. This paper presents a new, unified approach in combining the control and observation problem for robotic manipulators. It links the design of an independent joint acceleration controller to the design of a variable structure state observer that is used to estimate the joint acceleration. Since both the joint acceleration controller and the observer introduced in this paper are likely to implement high gains to improve tracking, the effects of the time delay between the measurement of the output and the control loop response has been investigated. The observer design also considers the observation robustness against unknown but bounded disturbances using the theory of variable structure systems. A simulation study to investigate the performance of the joint acceleration controller and observer is conducted on a PUMA 560 robot. Simulation results showed that the proposed combination of observer and controller are robust to the change in the payload and small time delays.