bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed Sensors for Active Structural Acoustic Control Using Large Hierarchical Control Systems
Authors: Kidner Mike , Johnson Marty , Batton Brad
Published: May 2008

The active structural acoustic control of sound radiation in large structures, such as launch vehicle payload fairings, can require very complex control systems if the control architecture is centralized. For this reason hierarchical, decentralized, control architectures have been suggested as one method of simplifying the complexity of the system and improving the robustness of the system to failures. In a hierarchical configuration, individual actuators or groups of actuators act on local information and use this information to drive the system locally. Higher level, slower acting, master controllers can then be used to observe the global performance and adapt the behavior of the local control systems. The local control units can use feedforward, feedback or hybrid feedforward/feedback techniques. It has been previously shown that good performance can only be achieved if the non-radiating high order wavenumber components are removed from sensor signals. This paper develops both analytically and experimentally a two dimensional distributed structural sensor designed as a wavenumber filter. Filtering in the wavenumber domain is made more attractive since it does not cause the phase problems associated with filtering in the time domain. A numerical method for combining ring shaped sensors is presented. It is shown that low and band pass sensors can be created with relatively few ring elements. Experimental results using a two dimensional ring sensor (with eight rings) attached to a large plate structure is presented. Results show that by carefully combining the outputs from the sensor rings both low pass two dimensional wavenumber filters can be created.
Finite Element Stress Response Analysis of Butt Adhesive Joints of Hollow Cylinders Subjected to Impact Bending Moments
Authors: Sawa Toshiyuki , Suzuki Yoshihito , Kido Shoichi
Published: May 2008

The stress variation in butt adhesive joints of hollow cylinders subjected to impact bending moments was analyzed in elasto-plastic deformation ranges using finite element method. The impact bending moments were applied to the loading side adherend of the joint by dropping a weight. The name of FEM code employed was DYNA3D. The effects of Young’s modulus of the adhesive and the effect of the adhesive thickness on the stress variations at the interfaces were examined. In addition, the characteristics of joints subjected to the impact bending moments were compared with those of the joints under static bending moments, and the strength of the joints under impact bending moments was estimated by using the interface stress distributions. As the results, it was found that (1) the maximum value of the maximum principal stress σ1 occurred at the outside edges of the fixed side adhesive interface under the impact bending moments; (2) The maximum value of maximum principal stress σ1 increased as Young’s modulus of the adhesive increased when the joints were subjected to impact bending moments; (3) The maximum value of σ1 increased as the adhesive thickness decreased; (4) the characteristics of joints subjected to the impact bending moments were opposed to those subjected to the static bending moments. In addition, experiments were carried out to measure the strain response of butt adhesive joints subjected to impact bending moments using strain gauges, and the joint strengths were also measured. The measured strain response was compared with the numerical results. A fairly good agreement was found between the numerical and the measured results concerning the strain responses.
Modular Design: A Basis for the Successful Application of Mechatronics to Heavy Machinery
Authors: Dierneder Stefan , Scheidl Rudolf
Published: May 2008

Mechatronics—the functional interaction and spatial integration of mechanics, electronics, and informatics [1]—in this strict form is reality in precision engineering, several components in a motor car, robots, and other specific devices or machines. Though functional interaction is reality in most heavy machinery today due to high level automation, spatial integration at first glance seems ridiculous simply due to the dimensional discrepancies between the heavy mechanical and the tiny electronic components. The question is, what improvements can mechatronics, i. e. the spatial integration in addition to functional interaction, bring?
Using Tuned Mass Dampers to Silence a Coordinate Measuring Machine
Authors: Myszka David H.
Published: May 2008

Nearly every manufacturing operation relies on servo-controlled automation and inspection machines. The design of these machines requires close attention to the relationships of the mechanical system with the electronic control system. Often, the attributes of one component can augment the weaknesses of another, and vice versa. For example, linear motions are traditionally produced with a rotary motor and ball screw. Recently, linear motors have gained popularity because of their numerous advantages. However, the servo-controls can, more easily, excite resonant frequencies in the machine structure. Therefore, controlling the machine at various speeds can produce excessive structural vibrations as different modes are excited. Thus, improvement in one component causes difficulties with another. An efficient solution is a tuned mass damper (TMD). This is a simple, modular device that consists of a weight, mounted on a spring along with a viscous energy absorber. The tuned mass damper is placed where the undesired vibratory motion is greatest. The size of the mass, spring and damper are adjusted, or tuned, so they oscillate out-of-phase with the structure and reduce the amplitude of vibration. This paper will review the theory of tuned dynamic dampers, and illustrate an application of integrating them into the design of a coordinate measuring machine.
Porous Materials as Fluid Distributors in Polymer Electrolyte Fuel Cells: A Computational Performance Analysis
Authors: Senn S. M. , Poulikakos D.
Published: May 2008

Commonly used ribbed flow-fields such as parallel and serpentine flow-fields in polymer electrolyte fuel cells (PEFC) exhibit limited mass transfer to the part of the diffusion and catalyst layer which is not covered by flow channels, leading to a considerably reduced reactant concentration and increased overpotential losses under the current collector shoulders. In this study, a novel concept is investigated, according to which the traditional ribbed flow delivery systems are replaced with permeable porous fluid distributors, which circumvent drawbacks such as those mentioned earlier. A complex mathematical model, including the conservation of mass, momentum, energy, species and electric current, using Butler-Volmer kinetics for electrochemical reaction rates, is numerically solved in three dimensions, to investigate the impact of different flow configurations on the performance of hydrogen fuel cells. It is found that cells with porous gas distributors generate substantially higher current densities and therefore are more advantageous with respect to mass transfer. Reduction in stack weight is another strong argument for using porous flow distributors in future applications.
Collaborative Development of a Structural Damper Utilizing Ultra-High-Damped Elastomer
Authors: Sweeney Shannon K. , Michael Robert J.
Published: May 2008

This paper defines a current applied research project in mechanical engineering technology, describes the roles of the principles, provides a status report of year one work, and provides the major goals for year two. The purpose of the project is to develop a marketable viscoelastic structural damper utilizing ultra-high-damped elastomer to protect buildings from seismic and wind events. The project is a collaboration of Penn State Erie, Lehigh University, and Lord Corporation that is funded by a grant from the Pennsylvania Department of Community and Economic Development through the Pennsylvania Infrastructure Technology Alliance.
Three-Dimensional Finite Element Prediction of Machining-Induced Stresses
Authors: Marusich T. D. , Usui S. , McDaniel R. J.
Published: May 2008

Controlling residual stress in machined workpiece surfaces is necessary in situations where service requirements subject structural members to cyclic fatigue loading. It is desirable to have a predictive capability when attempting to optimize machined parts for cost while taking into account residual stress considerations. One such method of machining modeling is application of the finite element method (FEM). A three-dimensional FEM model is presented which includes fully adaptive unstructured mesh generation, tight thermo-mechanically coupling, deformable tool-chip-workpiece contact, interfacial heat transfer across the tool-chip boundary, momentum effects at high speeds and constitutive models appropriate for high strain rate, finite deformation analyses. The FEM model is applied to nose turning operations with stationary tools. To substantiate the efficacy of numerical and constitutive formulations used, metal cutting tests are performed, residual stress profiles collected, and validation comparison is made.
Optimal Feed-Rate Scheduling for High-Speed Contouring
Authors: Dong J. , Stori J. A.
Published: May 2008

The majority of efforts to improve the contouring performance of high-speed CNC systems have focused on advances in feed-back control techniques at the single-axis servo level. Regardless of the dynamic characteristics of an individual system, performance will inevitably suffer when that system is called upon to execute a complex trajectory beyond the range of its capabilities. The intent of the present work is to provide a framework for abstracting the capabilities of an individual multi-axis contouring system, and a methodology for using these capabilities to generate a time-optimal feed-rate profile for a particular trajectory on a particular machine. Several constraints are developed to drive the feed-rate optimization algorithm. First, simplified dynamic models of the individual axes are used to generate performance envelopes that couple the velocity vs. acceleration capabilities of each axis. Second, bandwidth limitations are introduced to mitigate frequency related problems encountered when traversing sharp geometric features at high velocity. Finally, a dynamic model for the instantaneous following error is used to estimate the contour-error as function of the instantaneous velocity and acceleration state. We present a computationally efficient algorithm for generating a minimum-time feed-rate profile subject to the above constraints, and demonstrate that significant improvements in contouring accuracy can be realized through such an approach. Experimental results are presented on a conventional two-axis X-Y stage executing a complex trajectory.
The Effect of Harmonic Force Components on Regenerative Stability in End Milling
Authors: Wang J.-J. Junz , Zheng C. M. , Huang C. Y.
Published: May 2008

In a systematic manner, this paper investigates the effects of harmonic force components on the regenerative stability of an end milling process. By representing the milling force pulsation in a Fourier series expansion form, the dynamic force components and the average forces due to bi-directional dynamic feed rates are both included in the generalized system dynamics formulation. In the resulting expression for the stability criterion, the spectral features of the milling forces are integrated with the dynamics of the structure, showing the significance or insignificance of the dynamic components of the milling forces in affecting the stability of the milling process. Key system parameters discussed include the magnitude of the average and harmonic forces, the cutter helix angle and the spindle speed. It is shown that a low helix angle and a smaller number of cutting flutes increase the effect of dynamic forces on the system stability. The significance of the harmonic forces is exemplified by the special cutting conditions where the average force becomes zero and the stability limits would be infinite as predicted by models using the average force alone. Improvements in the accuracy of stability lobes resulting from the inclusion of the dynamic forces and the validity of the presented model in general will be illustrated by numerical simulation and verified by experiments as well as by comparison with published results.
A Pole/Zero Placement Approach to Reducing Structure Vibration in End Milling
Authors: Wang J.-J. Junz , Huang C. Y.
Published: May 2008

Forced vibration or the steady state vibration in a milling process inevitably occurs due to the periodic excitation of the intermittent cutting engagement of the milling cutter on the work and the structure, and it almost always exist even in the absence of chatter in a stable milling system, leading to dimensional and surface error and premature wear in tool and machine components. In this paper, an analytical model for the forced vibration in an end milling process is derived and criteria in selecting cutting conditions to reduce the forced vibration are presented. The analytic expression for the forced vibration due to the periodic milling force is obtained as the product of the Fourier transform of the milling force and the frequency transform of the structure dynamics. Analysis of the vibration model shows that the structure vibration can be reduced by selecting cutting parameters so that the zeroes of the frequency transform of the milling process function are near the poles of the structure dynamics. A design equation in terms of cutter geometry, axial depth of cut and structure natural frequency is obtained for the conditions when the forced vibration can be minimized. The presented analysis is illustrated through numerical simulation and verified by experimental results.
FE Approach: Electro-Mechanical-Fluid Interaction of Jet Pipe Electrohydraulic Flow Control Servovalve
Authors: Hiremath Somashekhar S. , Singaperumal M. , Krishna Kumar R.
Published: May 2008

Jet pipe electrohydraulic servovalve finds main application in feedback control system working on jet engine and fighter aircrafts. The analyzed jet pipe electrohydraulic servovalve is used in precise fuel control applications in gas turbine engine. This paper gives a new approach for servovalve modeling with the hydrostatic fluid elements in achieve steady state operation. The actual flow required to achieve the force balance is presented analytically. FE model gives the relationship between the spool and jet pipe position in achieving the steady state operation. The spool end cavity volume changes are presented.
Impact of Prognosis on Asset Life Extension and Readiness
Authors: Macheret Yevgeny , Christodoulou Leo
Published: May 2008

Fatigue response of structural components is determined by environmental conditions, material microstructure, and loading history. Variation of these factors results in significant scatter in fatigue-crack growth rates and component life. In this paper, the impact of prognosis capability on asset life extension and readiness is evaluated. Fatigue-crack growth data on aluminum samples under controlled spectrum loading are used to describe the statistics of the crack-size distribution. Several sensors with different probability of detection (POD) characteristics are considered for detecting cracks of critical size, and the effect of the POD on the component life extension is evaluated. Although the crack-detection capability leads to the asset life extension, it is not sufficient to maintain required mission readiness. On the other hand, the prognosis capability, which is based on the knowledge of the component’s current damage state, damage evolution laws, and upcoming mission loading, allows required mission readiness to be maintained.
Micro-Structronics and Control of Hybrid Electrostrictive/Piezoelectric Thin Shells
Authors: Chai W. K. , Tzou H. S. , Arnold S. M.
Published: May 2008

Certain ferroelectric materials possess dual electrostrictive and piezoelectric characteristics, depending on their specific Curie temperatures. These materials exhibit piezoelectric characteristics in the ferroelectric phase when the temperature is below the Curie point. However, they become electrostrictive in the paraelectric phase (non-polar phase) as the temperature exceeds the Curie point. The (direct) electrostrictive effect is a quadratic dependence of stress or strain on applied electric field. The nonlinear electromechanical effect of electrostrictive materials provides stronger actuation performance as compared with that of piezoelectric materials. Due to the complexity of the generic ferroelectric actuators, micro-electromechanics and control characteristics of generic electrostrictive/piezoelectric dynamics system deserve an in-depth investigation. In this study, electro-mechanical dynamic system equations and generic boundary conditions of hybrid electrostrictive/piezoelectric double-curvature shell continua are derived using the energy-based Hamilton’s principle, elasticity theory, electrostrictive/piezoelectric constitutive relations, and Gibb’s free energy function. Moreover, the second converse electrostrictive effect and the direct piezoelectric effect are all considered in the generic governing equations. Simplifications of the generic theory to other common geometries or specific materials are demonstrated and their electromechanical characteristics are also evaluated.
A Methodology for an Integrated (Electrical/Mechanical) Design of PWBA
Authors: Novotny Shlomo , Ahn Wonkee , Agonafer Dereje
Published: May 2008

This paper describes a general methodology an electrical circuit design data is mapped into an intermediate analyzable representation which supports the information requirement of several thermo-mechanical analyses including product optimization/idealization. This paper describes other issues encountered such as how to integrate product data that spans more than one tool, how to modify and add analysis data that is necessary during analysis, and how to use data stored in the analysis module from different programming environments. The advantage the process offers is also described by considering a PWBA design such as layout and layup in electrical design system.
MEMS-Based Spatial and Temporal Thermal Management of High Heat Flux Electronics
Authors: Amon Cristina H. , Yao S. C.
Published: May 2008

This presentation describes the development of EDIFICE: Embedded Droplet Impingement For Integrated Cooling of Electronics. The EDIFICE project seeks to develop an integrated droplet impingement cooling device for removing chip heat fluxes over 100 W/cm2, employing latent heat of vaporization of dielectric fluids. Micro-manufacturing and MEMS (Micro Electro-Mechanical Systems) will be discussed as enabling technologies for innovative cooling schemes recently proposed. Micro-spray nozzles are fabricated to produce 50–100 micron droplets coupled with surface texturing on the backside of the chip to promote droplet spreading and effective evaporation. A novel feature to enable adaptive on-demand cooling is MEMS sensing (on-chip temperature, remote IR temperature and ultrasonic dielectric film thickness) and MEMS actuation. EDIFICE is integrated within the electronics package and fabricated using advanced micro-manufacturing technologies (e.g., Deep Reactive lon Etching (DRIE) and CMOS CMU-MEMS). The development of EDIFICE involves modeling, CFD simulations, and physical experimentation on test beds. This lecture will then examine jet impingement cooling of EDIFICE with a dielectric coolant and the influence of fluid properties, micro spray characteristics, and surface evaporation. The development of micro nozzles, micro-structured surface texturing, and the system integration of the evaporator is discussed. Results of a prototype testing of swirl nozzles with dielectric fluid HFE-7200 on a notebook PC are presented. This paper also reviews liquid and evaporative cooling research applied to thermal management of electronics. It outlines the challenges to practical implementation and future research needs.
Development of a Transabdominal Anchoring System for Trocar-Less Laparoscopic Surgery
Authors: Fernandez Raul , Bergs Richard A. , Eberhart Robert C. , Baker Linda A. , Cadeddu Jeffrey A.
Published: May 2008

Compared with open surgery, laparoscopy results in significantly less pain, faster convalescence, and less morbidity. However, eye-hand dissociation, a two-dimensional field-of-view and fixed instrumentation with limited degrees of freedom contribute to a steep learning curve and demanding dexterity requirements for many laparoscopic procedures. One of the main limitations of laparoscopy is the fixed working envelope surrounding each trocar, often necessitating placement of multiple ports to accomodate changes in position of the instruments or laparoscope to improve visibility and efficiency. The placement of additional working ports contributes to post-operative pain and carries a small risk of bleeding or adjacent organ damage. In order to provide for greater flexibility of endoscopic viewing and instrument usage and to further reduce morbidity, a novel adjunct laparoscopic system has been developed consisting of a platform capable of supporting various laparoscopic tools which is secured magnetically to the abdominal wall and subsequently positioned within the abdominal cavity through surgeon-controlled, external magnetic couples on the patient’s abdomen. Using this technique, instruments such as miniature endoscopic cameras used to augment the surgical field of view and surgical retractors have been successfully evaluated in a dry laboratory as well as in porcine models, with several others currently under investigation. This document elaborates on the theoretical and empirical process which has led to anchoring designs optimized for size, strength and surgical compatibility, as well as the benefits, limitations and prospects for the use of incisionless, magnetically-coupled tooling in laparoscopic surgery.
Electro-Dynamics and Micro-Actuation of Ultrasonic Curvilinear Arc Stators
Authors: Smithmaitrie P. , Tzou H. S.
Published: May 2008

Driving mechanisms basically deliver two fundamental motions, i.e., the linear and the curvilinear motions. A piezoelectric laminated circular arc can serve as a curvilinear arc stator to deliver curvilinear motion on a spherical surface. This study is to evaluate ultrasonic vibration characteristics and microscopic membrane/bending actuation forces of piezoelectric actuators laminated on a curvilinear circular arc. Mathematical model and governing equations of circular arcs bonded with piezoelectric actuator patch are derived, followed by analysis of actuator control forces and moments and microcontrol actions in the modal domain. Study of vibration characteristics is conducted to design optimal actuator configuration, e.g., size and location. Then, distributed control forces and micro-control actions of the curvilinear arc stator are analyzed with respect to key design parameters (i.e., arc radius, arc thickness and actuator thickness). Study of stator vibration behavior clearly suggests an optimal actuator size and location to efficiently excite the desirable ultrasonic natural mode dominated by the micro-bending control action.
Hydraulic Spool Valve Metering Notch Characterization Using CFD
Authors: Yang Roger
Published: May 2008

This paper presents some results from an attempt to characterize hydraulic oil flow inside spool valves with different spool metering notches using Computational Fluid Dynamics (CFD). Hydraulic spool valve oil flow under different conditions has been simulated using a commercially available CFD software program. The fluid flow is assumed steady-state, incompressible, isothermal and normally in a turbulent mode. A complete simulation procedure is presented from parametric geometry creation with a 3-D solid CAD program through final post-processing of CFD results. Main focus of this study is to explore the effects of geometric parameters of notches on important hydraulic oil flow characteristics, such as flow force and discharge coefficients. Formulas, intended for predicting such flow forces and discharge coefficients at different stage of spool notch openings, have been generalized and summarized under certain conditions based on a CFD result database from groups of same types of notches. Results comparison to experimental data is also presented.
Manufacturability Analysis of Multi-Material Objects Molded by Rotary Platen Multi-Shot Molding Process
Authors: Li Xuejun , Gupta Satyandra K.
Published: May 2008

This paper describes a systematic approach for manufacturability analysis of multi-material objects molded using rotary platen multi-shot injection molding process. In this paper we first identify potential manufacturability problems that are associated with objects molded by the rotary platen process. Identified problems include infeasibility of molding sequences, unnecessary mold complexity, undesired friction during mold opening and closing, and undesired material flash on finished faces. These problems are unique to multi-material molding and do not occur in traditional injection molding. For each of the above four potential manufacturability problems, this paper also describes geometric algorithms for detecting the potential occurrence of the problem based on the object and mold design, finding its causes, and offering appropriate redesign suggestions. We expect that these algorithms will help in decreasing the product development time and improving the product quality for molded multi-material objects.
Micro Four-Point Probe With Metal Tip
Authors: Shin Heungjoo , Hesketh Peter J.
Published: May 2008

A fabrication method for a metal micro four-point probe with metal tip and measurements made using this probe are presented. A novel conical metal tip etching method using silicon dioxide chamber is also introduced. Four-point-probe resolution is decided by the electrode spacing because the effective probing depth is proportional to the electrode spacing [1]. AFM (Atomic Force Microscope) cantilever type micro four-point probe can be installed in the commercial AFM to measure the sample resistivity with low contact force and high resolution [2]. The integration of a vertical tip extends the useful application of micro four-point-probe. A conductive tip can be fabricated by coating a dielectric cantilever with conductive material. However, solid electric contact between sample and cantilever tip cannot be ensured because of the possibility of tip coating material wear. The effect of conductivity loss due to wear can be reduced with a solid metal tip.
A Rear-End Protection Device for Heavy Vehicles
Authors: Atahan Ali O. , Joshi Abhishek S. , El-Gindy Moustafa
Published: May 2008

Rear underride crashes, particularly with heavy vehicles, constitute a serious safety concern for passenger cars. Several solutions to this emerging concern have been proposed by responsible agencies. Recent rear-end crashes with heavy vehicles show that a properly used rear underride guard devices can slow down impacting vehicle in a controlled manner. Moreover, with the use of these devices, the severity of crashes can be reduced and loss of lives can be prevented. In this paper, a special underride guard device is designed for heavy vehicle use. The height of the device from ground and support conditions are varied to evaluate and compare the crash performances. Finite element models of these particular designs are constructed and models are impacted by a passenger car model traveling at two different speeds of 48 km/h and 64 km/h. LS-DYNA, a non-linear finite element code capable of analyzing large deformations is used for the analysis. Vehicle decelerations, energy dissipations and passenger car crush characteristics are compared to determine the acceptability of each design. Based on the simulation study, an optimum height from ground and support condition are determined for acceptable impact performance for heavy vehicle mounted rear -end underride guard devices against passenger vehicle impacts.
Molecular Dynamics Simulations of Nanotube-Polymer Composites for Use as Thermal Interface Material
Authors: Mahajan S. , Subbarayan G. , Sammakia B. G. , Jones W.
Published: May 2008

Thermal management in microelectronics is an important issue due to the projected increase in power dissipation in the electronic devices over the next 5–10 years. We seek a solution to this problem by exploring carbon nanotube-polymer matrix composites for use as thermal interface materials because of the reported high thermal conductivity and other remarkable thermal and mechanical properties of nanotubes. As an intermediate step to finding the composites’ conductivity, it is important to validate the use carbon nanotubes by calculating its diffusivity and conductivity first. This would facilitate later the estimating of important design parameters for thermal interface materials such as thermal diffusivity and conductivity. As polymer molecules are on the same size scale as nanotubes and the interaction at the polymer/nanotube interface is highly dependent on the molecular structure and bonding, Molecular Dynamic (MD) simulation is used to estimate the nano-scale properties. In this paper, until cell model consisting of a carbon nanotube was used and the diffusivity was measured. These findings would have implications in improving the thermal management efficiency and consequently improve the performance and reliability of future microelectronic devices.
Development and Validation of a Control-Oriented Model of a Spark-Ignition Direct-Injection Engine
Authors: Lee Byungho , Guezennec Yann , Rizzoni Giorgio , Trombley Doug
Published: May 2008

Due to the increasing demands on improved fuel economy and stringent government regulations on tailpipe emissions, many automotive industries and research institutes have been looking for alternative solutions, such as diesel engines, hybrid-electric vehicles, and fuel cell technologies, over conventional port fuel injection (PFI) gasoline engines to meet the demands. On the other hand, many people in the automotive community also realize that there are still a lot of room for improvements in gasoline engine technologies, such as utilizing direct injection and/or variable valve actuation. In order to fully realize the potential benefits of such advanced technologies in gasoline engines, a well-coordinated complex control system design is essential. This paper describes the development and validation of a control-oriented mean-value model for a spark-ignition direct-injection (SIDI) engine to assist and accelerate such coordinated control system design and calibration processes via use of an engine model. The performance and accuracy of the dynamic engine model are evaluated and validated against a set of data for an engine running on a transient driving cycle.
Reduced Order Model Analysis for Two Dimensional Molecular Dynamic Chain Structure Attached to an Atomic Force Microscope
Authors: Tang Deman , Dowell Earl H.
Published: May 2008

Dynamic analysis and numerical simulation of a protein-ligand chain structure connected to a moving atomic force microscope (AFM) has been conducted. The elements of the chain are free to extend and rotate relative to each other in a two-dimensional plane. Sinusoidal base excitation of the cantilevered beam of the AFM is considered in some detail. Reduced order (dynamic) models are constructed using global modes for both linear and nonlinear dynamic systems with and without the “nearest neighbor assumption”. The agreement between the original and reduced order models (ROM) is very good even when only one global mode is included in the ROM for either the linear case or for the nonlinear case, provided the excitation frequency is lower than the fundamental natural frequency of the linear system. For higher excitation frequencies, more global modes are required. The computational advantage of the reduced order model is clear from the results presented.
Magnetic Field-Induced Nonlinear Vibration of an Unbalanced Rotor
Authors: Wang Yuefang , Sun Ganyun , Huang Lihua
Published: May 2008

The free and forced flexural vibrations are investigated for rotors of electric motors operating in unsymmetrical magnetic fields. The magnetic potential energy reserved in the air-gap is analytically derived and the unbalanced magnetic pull is obtained through the law of energy conservation. With this excitation, the equations of motion of the unbalanced rotor are developed for nonlinear displacements response. For small dynamic eccentricities, the equations of motion are simplified and the rotor is compared to a free Duffing oscillatory system. The analytic solution for forced vibrations subject to residual mass-unbalance excitations is also obtained. Jump phenomenon in the solution is pointed out, and the effects of initial eccentricity and flux density on the natural frequency are also investigated.
Product-Based Internet 3D-CAD Design Education
Authors: Sakamoto Haruo , Tsuneishi Takuya , Sakamoto Masaoki
Published: May 2008

This paper describes 3D-CAD design education for mechanical engineering students at the Kochi University of Technology. For such a design education, several examples of design exercises are given as sample subjects as well as elective subjects, which students can select. In the next step, products, such as wind power generators that have already been manufactured, were selected as the design goals. From the viewpoint of research interests, wind power generators using rareearth material permanent magnets were studied. 3D-CAD design education using such a real product is considered to be an important step in their fudamental understanding of design. This needs to be carried out before students start creating their own new products in industry. On the other hand, internet multi-station design will be realized in the very near future in industry. 3D-CAD and internet design are expected to be a part of the new design curriculum in universities. As an example of students’ product design work, a small-sized hand-made electric vehicle is also introduced.
The Effects of the Crack Surfaces Interaction and the Crack Tip Plasticity on the Dynamic Response of the Circumferentially Cracked Turbo Generator Shafts
Authors: Vaziri A. , Nayeb-Hashemi H. , Hamidzadeh H. R.
Published: May 2008

Turbo generator shafts are often subjected to complex dynamic torsional loadings, resulting in generation and propagation of circumferential cracks. These cracks can severely affect the vibration characteristics of the shafts. The effects of a circumferential crack, its size and location on the torsional dynamic response of a shaft is obtained, considering the local energy loss at the crack tip due to the cyclic plasticity and the crack surfaces interaction. The crack is taken to be normal to the shaft axis and the shaft is subjected to a harmonic torsional load. The shaft material is assumed to be elastic perfectly plastic. The local flexibility is calculated by evaluating the resistance of the un-cracked region of the shaft to the rotational displacement. The effective damping constant is evaluated by considering the frictional energy loss due to the crack surfaces interaction and energy loss due to the plasticity at the crack tip. The energy loss due to the crack surfaces interaction is evaluated by assuming a pressure distribution between mating fracture surfaces. The pressure distribution parameters are obtained by considering the fracture surface roughness (asperities height and width), and crack opening displacements in Modes I and III. The Energy loss due to the plasticity at the crack tip is related to the plastic zone size. The effects of the applied Mode III stress intensity factor on the energy loss due to the friction and the energy loss due to the plasticity at the crack tip are investigated. The results show that depending on the amplitude of the applied Mode III stress intensity factor, one of these energy losses may dominate the total energy loss. The results further indicate that the vibration characteristics of the shaft are significantly affected by considering these two sources of the local energy loss.
Multivariable Control Design for a Bilateral Telemanipulator
Authors: Fite Kevin B. , Goldfarb Michael
Published: May 2008

This paper presents an architecture and control methodology for a multi-degree-of-freedom teleoperator system. The approach incorporates impedance control of the telemanipulator pair and formulates the system as a single feedback loop encompassing the human operator, telemanipulator, and remote environment. In so doing, multivariable Nyquist-like techniques are used to design compensation for enhanced stability robustness and performance. A measure of the transparency exhibited by the multivariable teleoperator system is attained using matrix singular values. The approach is experimentally demonstrated on a three degree-of-freedom scaled telemanipulator pair with a highly coupled environment. Using direct measurement of the power delivered to the operator to assess the system’s stability robustness, along with the proposed measure of multivariable transparency, the loop-shaping compensation is shown to improve the stability robustness by a factor of almost two and the transparency by more than a factor of five.
Springback Analysis for Metal-Polymer-Metal Laminates
Authors: Liu Li , Wang Jyhwen
Published: May 2008

Metal-polymer-metal laminate is an emerging material that has many potential applications. The laminated structure consists of two outer layers of sheet metal and a polymeric center core. The material offers an excellent sound deadening properties and is being introduced to applications where noise reduction is desired. Part manufacturing for laminates involves converting a flat sheet into a deformed body. Springback has been a major concern in shape control. While bending of a single layered sheet metal does not exhibit significant sidewall curl, the problem is pronounced in bending laminates. This paper presents an analytical approach to predict springback and sidewall curl of laminates due to simple bending. Based on the models, springback factor Ks is calculated. It is shown that the prediction is in good agreement with the published experimental data.
Micro, Internal-Combustion Engine Fabrication With 900 µm Deep Features Via DRIE
Authors: Knobloch Aaron J. , Wasilik Matt , Fernandez-Pello Carlos , Pisano Albert P.
Published: May 2008

New results are presented for the development of a micro, internal-combustion engine fabricated in a process that achieves 900 μm deep features via deep reactive ion etching (DRIE). A single-sided 900 μm deep etch process with high mask selectivity is used to generate straight sidewall structures with low sidewall roughness. This research 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 milliwatts with an energy density better than that of a conventional battery. The MEMS REPS is based on the planar geometry and self-valving operation of a Wankel engine with an integrated electrical generator. A generator and stator colocated within the engine rotor and housing eliminates the need for any external shafts, couplings, or seals. The rotary internal combustion engine is composed of 5 major comonents: a 900 μm deep rotor with soft magnetic poles and 25 μm wide in-plane cantilever beams which act as apex seals, a 900 μm deep epitrochoid housing with intake and exhaust ports, rear plate with spur gear, a top plate, and a shaft. This configuration was chosen in order to eliminate the effect of beaching during timed DRIE etches and to minimize engine leakage while maximizing spur gear teeth resolution, and simplifying engine fabrication. However, this configuration requires some assembly and optimization of DRIE parameters for each component. The rotor and epitrochoid housing are co-fabricated on the same wafer to minimize deviation in thickness and match etch behavior between mating components. This approach forces the generation of a mask with narrow, deep trenches (to define the cantilever apex seals on the rotors) in proximity to large “tub” etches (to define the engine housing). High etch cycle pressures improved etch selectivity to over 350:1 with respect to oxide and 150:1 to photoresist which is necessary for 900 μm deep features. High pressure also improved sidewall profile of the etched structures. Engine cross-sections show an 8 μm wall deviation on either side of a 250 μm trench through an etch depth of 867 μm. In addition to good sidewall straightness, these etch parameters give a low sidewall roughness through the generation of small size scallops on the sidewalls. However, the side effects of these etch parameters include silicon “grass” at the bottom of the trench, poor etch uniformity across the wafer, and increased effect of aspect ratio dependent etching. Some strategies to overcome these effects are discussed.
Experimental Measurement of Steady 3-D Thermal Green’s Functions
Authors: Ortega Alfonso , Wodrich Justin , Radtke Gregg
Published: May 2008

In many areas of applied mathematics, the Green’s function is the solution to a field problem due to the application of a potential or a gradient of a potential at a point or line in space on the solution domain. In heat transfer, the ‘thermal’ Green’s function (TGF) is the temperature field that would arise as a result of the application of a point source of heat within or on the surface of a medium. We have been exploring the possible use of the thermal Green’s function as a new way of characterizing the convective heat transfer from the surface of a solid that is cooled by a flow. An experiment was designed to explore possible ways in which the thermal Green’s function can be measured in the laboratory. A small heated spot was created on the wall of a flow channel to approximate a point source of heat. The resulting temperature field was measured by the use of thermochromic liquid crystal thermography, and was compared to an analytical solution derived from the 3-D thermal Green’s function. This paper reports progress towards understanding the limitations in creating and digitally photographing the temperature field from a small heat source on the wall of a convective flow.
An Improved Thermoeconomic Diagnosis Procedure for the Detection of Different Malfunctions of Complex Energy Systems
Authors: Verda Vittorio
Published: May 2008

Diagnosis of energy systems mainly consists of detecting and locating anomalies that cause reduction in the system efficiency or can cause major failures. This is an important task due to its economic implications. The attention is here focused on the anomalies that affect the system efficiency. The problem of their location is not easy to solve, due to some ‘disturbs’ that make propagate the effects of an anomaly throughout the system. These effects are caused by the dependence of the components’ behavior on their operating conditions. Moreover they can be amplified by the intervention of the control system and the variations in ambient conditions, fuel quality and plant load. A technique for highly complex system has been proposed in [1]. This procedure, based on the hypothesis of small malfunctions, consists of the progressive elimination of the disturbs, so that the anomalies could be more clearly highlighted. In this paper, a procedure particularly suitable for the application to operating plants is adopted to overcome the hypothesis of small malfunction. It consists of a combination of two techniques: 1) the use of neural networks for the elimination of the malfunctions [2] induced by the dependence of efficiency of components on the operating conditions and 2) the successive application of the analysis to several operating conditions selected within the plant case history.
A Common Approach to Risk Analysis for Homeland Security Decision-Making
Authors: Sims J. Robert , Ayyub Bilal M. , Balkey Kenneth R. , Feigel Richard E.
Published: May 2008

For many years, risk analysis has been used extensively to inform decisions by government and industry. Different methodologies have been employed, resulting in differences in terminology and approach that make it difficult to compare the results of analyses in different fields. Dealing with terrorist threats requires prioritizing the allocation of resources across a broad spectrum of possible targets. Therefore, a common approach is needed to allow comparison of risks. This paper provides a brief outline of an approach that will allow the results of risk analyses performed using current methodologies to be expressed in a common format and terminology to facilitate resource allocation decisions. The results of a risk analysis should never be the only basis for decision-making, but a decision made without employing risk analysis will probably not result in the best outcome.
Design of Three-Dimensional Active Noise Control Systems With Random Excitations
Authors: Chaghajerdi Amir H. , Shoureshi Rahmat A.
Published: May 2008

This paper addresses a general case of an active noise control problem with bandlimited random excitations. This study has concentrated on a combined adaptive feedforward/feedback (hybrid) active noise control architecture. Feedforward control is to attenuate the noise with frequency contents correlated to a reference signal, provided by the sensory output, and feedback is to attenuate the residual noise. Theoretical analysis of this hybrid control, and the required software and hardware designs for implementation of the proposed system are presented. The resulting controller has been applied to a common noise control problem, i.e. acoustic radiation. Experimental results from the implementation of this controller are discussed, and two-dimensional and three-dimensional quiet zones are illustrated.
GPC-Based Stable Reconfigurable Control
Authors: Shi Jianjun , Kelkar Atul G. , Soloway Donald
Published: May 2008

This paper presents development of multi-input multi-output (MIMO) Generalized Predictive Control (GPC) law and its application to reconfigurable control design in the event of actuator saturation. The stability of the GPC control law without reconfiguration is first established using Riccati-based approach and state-space formulation. A novel reconfiguration strategy is developed for the systems which have actuator redundancy and are faced with actuator saturation type failure. An elegant reconfigurable control design is presented with stability proof. A numerical example with application to reconfigurable flight control is presented to demonstrate the results presented in the paper.
Heat Pump Applications in Dedicated Outside Air Systems (DOAS)
Authors: Dhamshala Prakash R.
Published: May 2008

This paper deals with application of a heat pump as a part of the dedicated outside air system (DOAS) unit. DOAS systems are known to provide the energy cost savings by dehumidifying the fresh ventilating air in conjunction with the energy and heat recovery systems and also in parallel with the sensible cooling system. The energy cost savings associated with these systems results from operating the sensible cooling systems at higher evaporating temperatures which results in a higher coefficient of performance for the sensible chiller, lower pumping costs and lower capital costs. It is found that the operation of DOAS unit with the radiant panel cooling systems raises the energy cost savings even more significantly. Using hourly weather data, the energy cost saving analysis is performed for several geographical locations and estimated cost savings exceed well above 30 percent of the corresponding commercial building operational costs using the traditional VAV systems for most of the locations in USA.