bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Noise Reduction Liner for a 4T MRI Scanner
Authors: Mechefske Chris K.
Published: June 2008

High-field, high-speed Magnetic Resonance Imaging (MRI) can generate high levels of acoustic noise. There is ongoing concern in the medical and imaging research communities regarding the detrimental effects of high acoustic levels on auditory function, patient anxiety, verbal communication between patients and health care workers and ultimately MR image quality. In order to effectively suppress the noise levels inside MRI scanners, the sound field needs to be accurately measured and characterized. This paper presents the results of measurements of the sound radiation from a gradient coil cylinder within a 4 Tesla MRI scanner under a variety of conditions. These measurement results show; 1) that noise levels can be significantly reduced through the use of an appropriately designed passive acoustic liner, and 2) the true noise levels that are experienced by patients during echo planer imaging (EPI).
Evolution of Rotations of a Rigid Body Under the Action of Restoring and Control Moments
Authors: Akulenko L. D. , Leshchenko D. D. , Kozachenko T. A.
Published: June 2008

Perturbed rotations of a rigid body close to the regular precession in the Lagrangian case under the action of a restoring moment depending on slow time and nutation angle, as well as a perturbing moment slowly varying with time, are studied. The body is assumed to spin rapidly, and the restoring and perturbing moments are assumed to be small with a certain hierarchy of smallness of the components. A first approximation averaged system of equations of motion for an essentially nonlinear two-frequency system is obtained in the nonresonance case. Examples of motion of a body under the action of particular restoring, perturbing, and control moments of force are considered.
A Study on Stiffness Characteristics of Air Spring With FEM
Authors: Ye Zhen-Xia , Zhu Hai-Chao , He Lin
Published: June 2008

The vertical and transversal stiffness of the air spring with multi-layer composite material were studied using the nonlinear finite element analysis. The geometrical non-linearity, the nonlinear elasticity and the contacting nonlinearity were analyzed. The finite element model was built in Marc software, and the nonlinear stiffness characteristics were calculated. The influence of parameters on the stiffness characteristics was analyzed.
On Providing Formal Manufacturability Information to Upstream Product Development Processes: Methodology and Case Study
Authors: Opiyo Eliab Z.
Published: June 2008

Process planning is a key product development activity that links design and manufacturing, and is traditionally carried out based on the outcome of the design process. One of the consequences of conducting process planning after design is that the process planning (manufacturability) information needed in the execution of upstream activities is in most cases not available formally. Using informal manufacturability information in the early phases of the product development process can lead to e.g. untrustworthy feasibility study or unnecessary design iterations. As an attempt to solve this problem, a modular procedure for execution of process planning activities is proposed in this paper. It allows for the execution of some of the process planning activities to commence as soon as the details of the order and the requirements for the product are known. The goal is to ensure that formal manufacturability information is available in various stages of the product development process, including to those activities that take place prior to process planning. The new modular process planning procedure has been applied, and it has been found that the design iterations caused by lack of manufacturability information can be avoided. This paper first defines the problem and presents related works. It then introduces the modular process planning procedure, and presents an application case study.
Application of Data-Mining to Factor Analysis of Micro-Drilled Hole Quality for Multi-Layer PWBs
Authors: Hirogaki Toshiki , Aoyama Eiichi , Ogawa Keiji , Mori Kenichi
Published: June 2008

Recently, the demand for miniaturization and enhanced performance of printed wiring boards (PWBs) is growing more and more intense with the rapid popularization of information devices. Processing with micro-drills is generally used to make smaller diameter through-holes in PWBs, which are desired for the miniaturization of the equipment. However, the nail heading is one of the problems in the formation of the micro-through-holes. The purpose of this study is to apply a data-mining, which is used to statistically analyze given factors, to the obtained nail heading data of micro-drilled hole walls, and to elucidate the factors that influence the nail heading of the micro-drilled hole walls. The following conclusions were obtained. (1) It was clear that the height of the nail heading was affected by the drill cutting distance of copper foils and the amount of the drill tool wear more than the number of drilling hits or the drill cutting distance of the PWB number of drilled holes. (2) Data-mining was found to be effective to analyze factors which influence on the micro-drilled hole quality in the manufacturing field of PWBs.
Fractional Generalization of Ginzburg-Landau and Nonlinear Schroedinger Equations
Authors: Zaslavsky George M. , Tarasov Vasily E.
Published: June 2008

The fractional generalization of the Ginzburg-Landau equation is derived from the variational Euler-Lagrange equation for fractal media. To describe fractal media we use the fractional integrals considered as approximations of integrals on fractals. Some different forms of the fractional Ginzburg-Landau equation or nonlinear Schro¨dinger equation with fractional derivatives are presented. The Agrawal variational principle and its generalization have been applied.
Application of Air Spring in Controlling Line Spectra
Authors: He Qi-Wei , Zhu Shi-Jian , Lou Jing-Jun , He Lin
Published: June 2008

Application of air spring in controlling line spectra in the radiated noise of marine vessels was studied. Starting with the route to chaos and the scaling property of the power spectrum in the cascade of period-doubling bifurcations, the method of chaotic vibration isolation was advanced. The performance indices for the presented method were also given. The method was experimentally verified.
Remote Machine Monitoring Through Internet and Mobile Communication Using XML
Authors: Wang Wanbin , Tse Peter W.
Published: June 2008

XML is a markup language developed by the WWW Consortium. It has become a standard for data representation and exchanging over the Internet. This paper introduces the application of XML on a remote machine monitoring and fault diagnostic system through Internet and mobile communication, such as mobile phones and PDAs. The remote monitoring system takes XML as a core and uses it to encode diagnostic data. The capabilities provided by XML on Internet and mobile communication include the display of different contents in a XML file based on different requirements; the enquiry of current running conditions of an inspected machine via an Internet connected PC, or a mobile phone, or a PDA; the import of diagnostic data to a remote client program by using the XML based structure. Using XML makes all these capabilities become possible. Indeed, XML makes the sharing of data between different applications and the broadcasting of diagnostic data easier. It also uplifts the expandability and sustainability of the remote monitoring system.
Shock Analysis and Design Method of Vibration Isolating System in the Time Domain
Authors: Zhao Yinglong , He Lin , Lv Zhiqiang , Wang Yu
Published: June 2008

Choosing the equipment with good shock-resistant performance and taking shock protection measures while designing the onboard settings, the safety of onboard settings can be assured when warships, especially submarine subjected to non-contact underwater explosion, that is, these means can be used to limit the rattlespace (i.e., the maximum displacement of the equipment relative to the base) and the peak acceleration experienced by the equipment. Using shock-resistant equipments is one of shock protection means. The shock-resistant performance of the shock-resistant equipments should be verified in the design phase of the equipments. The shock design analysis methods used before and now includes shock design number method (static g-method), dynamic analysis in the time domain and dynamic design analysis method (DDAM). The FEA (Finite Element Analysis) software, for example, MSC.NASTRAN®, can be used for shock design analysis of the shock-resistant equipments. MSC.NASTRAN are used for shock design analysis of floating raft vibration isolating equipment with dynamic analysis method in the time domain in this paper, and the analysis results are in agreement with the test results. The shock design analysis method used in this paper can be used to analyze the shock-resistant performance of onboard shock-resistant equipments.
A CAD-Integrated System for Automated Idealization of CAD-Models for Finite Element Analysis
Authors: Stolt Roland
Published: June 2008

The work described in this paper seeks to minimize the time spent on manually reducing thin-walled CAD-geometry into surface idealizations. The purpose of the geometrical idealizations is the creation of shell element meshes for FE-calculations. This is motivated by time and thereby cost savings and also to make the results of the calculations available earlier in the product development process allowing the results to guide the designs to a larger extent. Systems for automated geometry idealization and creation of FE-models already exist, but this paper describes a novel approach with the working principle of analyzing how the CAD-specific features of the CAD-file history tree are constituted. This information is used to automatically create the best practice geometrical idealization in the same CAD-model. Evaluation of the performance of the system in an industrial example is also presented.
A New Multi-Pulse Chaotic Motion for Parametrically Excited Viscoelastic Axially Moving String
Authors: Zhang Wei , Yao Ming-Hui , Bai Li-Lai
Published: June 2008

In this paper, the Shilnikov type multi-pulse orbits and chaotic dynamics of parametrically excited viscoelastic moving string are studied in detail. Using Kelvin-type viscoelastic constitutive law, the equation of motion for viscoelastic moving string with the external damping and parametric excitation is given. The four-dimensional averaged equation under primary parametric resonance is obtained by directly using the method of multiple scales and Galerkin’s approach to the partial differential governing equation of viscoelastic moving string. The Shilnikov type multi-pulse chaotic motions of viscoelastic moving string are also found by using numerical simulation. A new phenomenon on the multi-pulse jumping orbits and a new strange attractor are observed from three-dimensional phase space for the first time.
Nonlinear Dynamics and Control of Ultrasonically Assisted Machining
Authors: Babitsky Vladimir , Astashev Vladimir
Published: June 2008

Nonlinear models of cutting process with superposition of ultrasonics are proposed and investigated. It is confirmed that under the influence of high frequency vibration, the phenomenological plasticisation of brittle materials and fluidisation of dry friction occurs. The mechanical characteristics of transformed machining processes are obtained. It is shown that excitation of the high-frequency nonlinear mode of tool-workpiece interaction is the most effective way of ultrasonic influence on dynamic characteristics of machining. The exploitation of this mode needs a new method of nonlinear control called as autoresonant one. An autoresonant system with supervisory computer control was developed and successfully used for the control of the piezoelectric transducer during ultrasonically assisted cutting.
A Study on the Fatigue Life Prediction of OHT Vehicle Structures Using the Modal Stress Recovery Method
Authors: Jung Il-Ho , Park Tae-Won , Seo Jong-Hwi , Jun Kab-Jin , Yim Hong Jae , Kim Hyuk , Park Joong-Kyung
Published: June 2008

In this paper, a computer aided analysis method is proposed for a durability assessment in the early design stages using the Modal Stress Recovery (MSR) and the linear damage rule. From a dynamic analysis of the OHT vehicle system with some flexible bodies, modal displacement time histories of vehicle structure components are calculated. From finite element analysis of components, modal stresses are calculated. With the modal displacement time history and the modal stress of the component, the dynamic stress time history at the critical location is produced using the superposition principle. Using the linear damage rule and the cycle counting method, the fatigue life is predicted from the dynamic stress time history. The process of predicting the fatigue life using the proposed computer models in this paper may be applied to structures of various dynamic systems.
Interaction of Neonates With a Bubble Oscillation System
Authors: Manilal P. I. , Al-Jumaily A. M.
Published: June 2008

The aim of this research is to predict the interaction of neonates suffering from Respiratory Distress Syndrome (RDS) with high frequency pressure oscillations (HFPO) such as those produced by a bubble oscillation (BO) system. Many different postulations exist as to why pressure oscillations enhance respiratory performance; however, the scope of this work focuses on the speculation that the vibrations produced by the pressure oscillations cause the neonatal airway walls to resonate at their natural frequencies, thereby helping to relax the respiratory walls and give the neonate a better chance of recovery.
System Data Management: An Inter-Disciplinary Collaboration Architecture for Systems Engineering
Authors: Gomes Jose´ , Singh Man-Mohan , Keren Mila , Zeng Sai , Rubin Julia , Balmelli Laurent , Boier-Martin Ioana
Published: June 2008

This paper presents a novel approach to integrating systems engineering (SE) artifacts and methods with discipline-specific detailed design artifacts and processes, for the purpose of facilitating inter-disciplinary collaboration. In particular, it addresses the lifecycle management of complex products involving mechanical, electrical, electronics and software aspects, and being designed following a formal product development methodology. The primary motivation of the approach is to capture and maintain the traceability between the concrete artifacts stored in discipline-specific “repositories” and the abstract artifacts used to support system-level decisions as well as system integration. The proposed approach acknowledges the fundamental differences that exist between the various engineering disciplines and therefore favors a loose coupling based on a process-centric management of the artifacts traceability links. These considerations lead to an inter-disciplinary collaboration and infrastructure pattern called “system data management” (SDM), with the role of enforcing the integrity of the inter-disciplinary traceability between artifacts. As a byproduct, this approach suggests a novel perspective on product data management (PDM) and software configuration management (SCM) integration that sharply contrasts with point-to-point integration solutions. The authors have implemented a prototype based on a service-oriented architecture (SOA) and existing PDM and SCM technologies.
Damping in a Fractional Relaxor-Oscillator Driven by a Harmonic Force
Authors: Narahari Achar B. N. , Hanneken John W.
Published: June 2008

It is shown that the so called fractional Relaxor-Oscillator, characterized by an index of fractional order, alpha, exhibits interesting relaxation-oscillation characteristics when subjected to a sinusoidal forcing. For the range of values 0 < alpha <1, the system exhibits some characteristics of a regular relaxor, and for the range 1 < alpha <2, some characteristics of a damped harmonic oscillator. But in the dynamic response to a sinusoidal forcing, there are characteristic features which have no parallel either in the regular relaxor or the damped harmonic oscillator. The system is characterized by a frequency dependent “relaxation time constant” in the range 0< alpha <1, and an associated phase lag. In the range 1 < alpha <2, there is a frequency dependent damping parameter and an associated phase lag. The two phase lags approach each other in the limit (alpha approaching 1) from either side of 1. Furthermore, there is a different power-law tail associated with each of these cases.
Contact Parameter Estimation With a Space Robot Verification Facility
Authors: Agar Julie , Sharf Inna , Lange Christian , Gonthier Yves
Published: June 2008

Computer simulations play an important role in the design and verification of space robotic operations since on-orbit tests are impossible to conduct before launch. Thus, accurate computer modeling and simulation of space robotic tasks is essential. Of particular difficulty are the space manipulator operations, that involve constrained or contact tasks. Here, the contact dynamics capability in the modeling tools becomes critical for high fidelity simulations. This in turn implies a need for accurate determination of contact parameters, which are used as inputs to contact dynamics simulation. In this work, the identification of contact dynamics parameters based on sensor data obtained during robotic contact tasks is considered. In particular, the contact parameter estimation problem is addressed for simple contacting geometries using the SPDM Task Verification Facility Manipulator Testbed (SMT) at the Canadian Space Agency, where SPDM is the Special Purpose Dexterous Manipulator. The SMT is a robotic simulation facility, which also features gravity compensation algorithms to support the emulation of space robots. Single point SMT contact experiments were performed with six different payloads. Eight unique single point contact parameter estimation algorithms were used as part of the process of identifying payload stiffness from SMT experimental data.
Initialization Issues of the Caputo Fractional Derivative
Authors: Narahari Achar B. N. , Lorenzo Carl F. , Hartley Tom T.
Published: June 2008

The importance of proper initialization in taking into account the history of a system whose time evolution is governed by a differential equation of fractional order, has been established by Lorenzo and Hartley, who also gave the method of properly incorporating the effect of the past (history) by means of an initialization function for the Riemann-Liouville and the Grunwald formulations of fractional calculus. The present work addresses this issue for the Caputo fractional derivative and cautions that the commonly held belief that the Caputo formulation of fractional derivatives properly accounts for the initialization effects is not generally true when applied to the solution of fractional differential equations.
Fractal-Agent Based Cooperation Style of Industrial Alliance
Authors: Dong Hongzhao
Published: June 2008

Internet technology provides a convenient and low-cost platform for the cooperation among two or more manufacturers. Industrial alliance is a networked cooperative enterprise group linked by the similar product and technology relying on such an Internet platform coupled with supporting cooperation system. However, with increasing bulkiness and complexity of the cooperation system, it is a significant issue in industrial alliance to simplify the cooperation style among these manufacturers. The hierarchical industrial alliance is always classified into alliance level, enterprises level and departments level. Based on the self-similarity principle of fractal, the paper analyzes the similarity concerning both function structure and workflow of the industrial alliance. To describe these self-similar organizations at different levels while developing information system, fractal-agent theory is raised here. Moreover, based on the fractal-agent theory, a new cooperation style of industrial alliance is put forward, by which a cooperation pool of fractal-agents and the multi-level nested dynamic sub-alliance can be established to simplify their cooperation activities. It’s practically proved that the technology can efficiently enable the industrial alliance to fulfill rapid reconfiguration.
Nonlinear Stochastic Optimal Control of Quasi Hamiltonian Systems
Authors: Zhu W. Q.
Published: June 2008

In recent years, a class of nonlinear stochastic optimal control strategies were developed by the present author and his co-workers for minimizing the response, stabilization and maximizing the reliability and mean first-passage time of quasi Hamiltonian systems based on the stochastic averaging method for quasi Hamiltonian systems and the stochastic dynamic programming principle. This review summaries the basic idea, procedures and applications of these strategies and pointes out necessary further work.
Drift Turning of Lateral Guided Vehicle With Sensor Steering Mechanism: Variable Kinetic Friction Model
Authors: Takita Yoshihiro , Date Hisashi
Published: June 2008

In a previous paper, the simulated loci of high-speed cornering did not correspond with experimentally obtained results because the tire model used only the sticking in the Coulomb friction model. If the centrifugal force becomes larger than the cornering force of the tires, then the vehicle does not maintain the desired course. The cornering force is affected by the sticking or slipping condition of the tires. In order to simulate the high-speed cornering trajectory, the present paper assumes three stages of friction: low kinetic friction force at the beginning of slipping, the period of kinetic friction force, and the return to the static friction condition at small slip angles. In addition to the Rear motor Rear drive (RR) type vehicle, the Front motor Front drive (FF) type vehicle with a Sensor Steering Mechanism (SSM) and a 4-wheel steering mechanism is developed. In the experiments of present paper, both of these robots are run on an oval course at high speed. Numerical simulation and experimental results indicate effective prediction by the friction model.
Study on the Sensitivity of Controllable Parameters in an Active Vibration Isolation System of Air Spring With Rubber Bellow
Authors: Shuai Chang-Geng , He Lin , Lv Zhi-Qiang
Published: June 2008

The characteristics of control parameters of air spring with rubber bellow are analyzed through finite element method and thermodynamic equation respectively. The analysis results indicate that the vertical stiffness of air spring is sensitive to the varying of vertical displacement and volume, and nonlinearly varies with vertical displacement. When the air spring is pressed down or pulled up under the exterior excitation, the height of air spring can be controlled to keep stable through adjusting the volume of air spring by the use of hydraulic transformer.
Degenerate Bifurcation Scenarios in the Dynamics of Coupled Oscillators With Symmetric Nonlinearities
Authors: Gendelman O. V.
Published: June 2008

We study the degenerate bifurcations of the nonlinear normal modes (NNMs) of an unforced system consisting of a linear oscillator weakly coupled to an essentially nonlinear one. Both the potential of the oscillator and of the coupling spring are adopted to be even-power polynomials with nonnegative coefficients. By defining the coupling parameter ε, the dynamics of this system at the limit ε → 0 and for finite ε is investigated. Bifurcation scenario of the nonlinear normal modes is revealed. The degeneracy in the dynamics is manifested by a ‘bifurcation from infinity’ where a saddle-node bifurcation point is generated at high energies, as perturbation of a state of infinite energy. Another (nondegenerate) saddle-node bifurcation points (at least one point) are generated in the vicinity of the point of exact 1:1 internal resonance between the linear and nonlinear oscillators. The above bifurcations form multiple-branch structure with few stable and unstable branches. This structure may disappear (for certain choices of the oscillator and coupling potentials) by mechanism of successive cusp catastrophes with growth of the coupling parameter ε. The above analytical findings are verified by means of direct numerical simulation (conservative Poincare sections). For particular case of pure cubic nonlinearity of the oscillator and the coupling spring good agreement between quantitative analytical predictions and numerical results is observed.
Bushing Model for Vehicle Dynamics Analysis Using Bouc-Wen Hysteretic Model
Authors: Ok Jin-Kyu , Sohn Jeong-Hyun , Lee Seung-Kyu , Park Su-Jin , Yoo Wan-Suk
Published: June 2008

In this paper, a new bushing model for vehicle dynamic analysis is proposed. Bushing components of a vehicle suspension system are tested to capture the nonlinear and hysteretic behavior of typical rubber bushing elements and the test results are used to develop bushing model using Bouc-Wen hysteretic model. ADAMS program is used to generate the Bouc-Wen hysteretic bushing model. The parameter identification through the sine excitation input is carried out in the time-domain. VisualDOC program is employed to find the optimal coefficients of the model. A numerical example is suggested to verify the performance of the proposed model.
Static and Dynamic Response of a Beam on a Winkler Elastic Foundation
Authors: Nusirat Timour M. A. , Hamdan M. N.
Published: June 2008

This paper is concerned with analysis of dynamic behavior of an Euler-Bernoulli beam resting on an elastic foundation. The beam is assumed to be subjected to a uniformly distributed lateral static load, have an initial quarter-sine shape deflection. At one end, the beam is assumed to be restrained by a pin, while at the other end, the beam is assumed to be restrained by a torsional and a translational linear spring. The beam is modeled by a nonlinear partial differential equation where the nonlinearity enters the governing equation through the beam axial force. In the static case, because of a unique feature of governing equation, the analysis was carried out using the theory of linear differential equations, but takes into account the effect of actual deflection on the induced axial thrust. In the dynamic case, stability analysis of the beam is carried out by calculating the nonlinear frequencies of free vibration of the beam about its static equilibrium configuration. The assumed mode method is used to discretize and find an equivalent nonlinear initial value problem. Then the harmonic balance is used to obtain an approximate solution to the nonlinear oscillator described by the equivalent initial value problem. The analyses of results were carried out for a selected range of values of the system parameters: foundation elastic stiffness, lateral load, and maximum beam edge deflection. In the static case the results are presented as characteristic curves showing the variation of the beam static deflection and associated bending moment distribution with each of the above system parameters. In the dynamic case, the presented characteristic curves show the variation of the nonlinear natural frequency corresponding to the first and the second modes over a range of each of the above system parameters.
Complicated Regular and Chaotic Motions of the Parametrically Excited Pendulum
Authors: Butikov Eugene I.
Published: June 2008

Several new types of regular and chaotic behavior of the parametrically driven pendulum are discovered with the help of computer simulations. A simple physical explanation is suggested to the phenomenon of subharmonic resonances. The boundaries of these resonances in the parameter space and the spectral composition of corresponding stationary oscillations are determined theoretically and verified experimentally. A close relationship between the upper limit of stability of the dynamically stabilized inverted pendulum and parametric resonance of the non-inverted pendulum is established. Most of the newly discovered modes are still waiting a plausible physical explanation.
Optimize Engineering Processes With Simultaneous Engineering (SE) and Concurrent Engineering (CE)
Authors: Vajna Sa´ndor , Guo Haiying , Schabacker Michael
Published: June 2008

The appropriate handling of time becomes one of the most important factors for industry to success because of globalization and market competition. Engineering processes should be optimized to achieve shorter “time to market”. This paper deals with Simultaneous Engineering (SE), which means parallelizing formerly serial executed product development processes, and Concurrent Engineering (CE), which means to cut processes into smaller sub processes or activities and parallelize them, both to achieve less product development time. The parallelization degree of processes depends on the dependencies between these processes. Therefore, the dependency between processes is defined and quantified. Processes are parallelized according to the result of the dependency calculation. Related concepts, methods and possible results are described in detail. An example is given about a home appliance product design processes to explain how the method works. The result shows that, with SE and CE, industry can reduce its product throughput time. The result depends also on how processes are modeled and how Concurrent Engineering is achieved.
Geometry-Based Similarity Assessment: A Method for Mistake-Proofing the Assembly of Complex Products
Authors: Cheldelin Brent , Ishii Kosuke , Wiggs Gene , Soman Narendra
Published: June 2008

Mixed model production is the assembly of multiple products on a common assembly line (see Fig. 1). Companies are moving to mixed-model production environments to: 1) reduce production investment, 2) provide increased customization and respond to globalization, 3) reduce response time and variability (order → delivery), and 4) reduce risk and uncertainty. This transition to a more chaotic production environment increases the chance of using incorrect parts as the number of “similar” parts increases dramatically. Many companies do not have systems in place to identify and prevent usage of the wrong part until after errors have occurred and are found in inspection or, worse yet, at the customer. CAD systems are invaluable for designing products of ever-increasing complexity. Design for Assembly (DFA) techniques are essential for minimizing product complexity to reduce product and manufacturing costs. New techniques such as Assembly FMEA and Mixed-model FMEA, can reduce the potential of using the wrong part. However, they require “experts” to identify potential interchangeability and, being human-dependent, are not 100% accurate. Most companies rely on assembly error-proofing technology (barcodes, visual inspection), part presentation simplification (kitting, lean manufacturing), or automation to prevent using the wrong part. Unfortunately, this approach does not prevent the design and installation of physically interchangeable parts. Instead, it prevents defects from escaping to the customer. This not only leads to unnecessary rework during production, but also significantly increases the chance of errors during service as many prevention approaches such as kitting and automation are not available. With product life-cycles shrinking (Shibata, 2001) and development times shortening even more severely, companies cannot afford to fix problems after they find them in production. Companies need to address the problem in the design stage. To address usage of wrong parts, the authors propose a geometry-based pairwise comparison that alerts designers to this potential error. By interacting with the CAD system or Visualization environment directly, the system provides accurate feedback to designers when their proposed parts are “too similar” to existing parts; without requiring additional time from the designer. This paper describes the new method, details various implementation approaches and their limitations, and concludes with difficulties of implementation. Several examples are explored along with the limitations of the approach.
Exploring the Relationship Between Lexical Behavior and Concept Formation in Design Conversations
Authors: Dong Andy , Davies Kevin , McInnes David
Published: June 2008

Designers bring individual knowledge and perspectives to the team. The hypothesis tested in this research is that semantic and grammatical structures (the language through which concepts are expressed) enable designers to bridge relations among ideas stored in each designer’s mind and from this to generate design concepts. This paper describes a linguistic and a computational method to examine the grammatical and semantic structure of design conversations and the linguistic processes by which individuals bridge their knowledge to the group’s ongoing knowledge accumulation. To test the hypothesis, we conducted a linguistic (systemic functional linguistics) and computational linguistic (lexical chain analysis) analysis of a design team conversation The computational analysis revealed hypernym relations as the primary lexico-syntactic pattern by which designers offer, interrelate and develop concepts. The linguistic analysis highlighted the grammatical linguistic features that actively contribute to the generation of design content by teams. These analyses point to the prospect of a functional correspondence between language use and a team’s ability to construct knowledge for design. This interrelation has implications both for computational systems that assess design teams and design teamwork education.
A Web-Based Design Tool for Snap-Fit Features
Authors: Ruan Tieming , Luscher Anthony F.
Published: June 2008

This paper describes an interactive web-based design tool, developed by using a web-based server application, for the three most common snap-fit features that are the cantilever hook, post & dome and bayonet & finger. Response surface equations that predict each snap-fit feature’s performance were applied in this web-based design tool. This web-based design tool also applied constraint management (CM), which helps the designers switch the input and output on the fly and prevent over-constraint. Two other constraint management modules were applied. The first one is sensitivity analysis module used to determine the input’s dependency to a specified output also applied in the design tool. The second one is correction advisor module used to see how much each dependent input’s value should change if one output changes to a new value. Two optimization modules, single-objective optimization and multiple-objective optimization, are applied to optimize the performance of snap-fit features. Finally a real design case for cantilever hook was conducted and the results were compared to experiment results.
Effective Model Reduction for Magnetically Levitated Flexible Rotors Including Contact Dynamics
Authors: Abulrub Abdul-Hadi G. , Sahinkaya M. Necip , Keogh Patrick S. , Burrows Clifford R.
Published: June 2008

Reduced order models are required for controller design purposes to allow practical realization and implementation in real-time applications. In the rotor dynamics field, the controllers associated with magnetic bearings are classic examples of such a requirement. A technique is introduced to reduce the order of a finite element rotor model to one involving only the required rectilinear displacements in sensor and controller nodal planes. The reduced order model is shown to predict a number of natural frequencies and responses to step changes in unbalance with considerable accuracy. A simulation of the rotor making contact with a rigid retainer bearing is also established using a constrained Lagrangian multiplier. Again, the differences between the full and reduced order model rotor orbits are shown to be small.
Modeling Squeeze-Film Damping of Electrostatically Actuated Microplates Undergoing Large Deflections
Authors: Younis Mohammad I. , Nayfeh Ali H.
Published: June 2008

A model for the dynamics of electrostatically actuated microplates undergoing large deflections under the effect of squeeze-film damping is presented. The model predicts the quality factors of microplates under a wide range of gas pressures and applied electrostatic forces up to the pull-in instability. The model utilizes the nonlinear Euler-Bernoulli beam equation, the von Ka´rma´n plate equations, and the compressible Reynolds equation. The static deflection of the microplate is calculated using the beam model. Analytical expressions are derived for the pressure distribution in terms of the plate mode shapes around the deflected position using perturbation techniques. The static deflection and the analytical expressions are substituted into the plate equations, which are solved using a finite-element method. Several results are presented showing the effect of the pressure and the electrostatic force on the structural mode shapes, the pressure distributions, the natural frequencies, and the quality factors.
Homogenization of Vibrating Periodic Lattice Structures
Authors: Gonella Stefano , Ruzzene Massimo
Published: June 2008

The paper describes a homogenization technique for periodic lattice structures. The analysis is performed by considering the irreducible unit cell as a building block that defines the periodic pattern. In particular, the continuum equivalent representation for the discrete structure is sought with the objective of retaining information regarding the local properties of the lattice, while condensing its global behavior into a set of differential equations. These equations can then be solved either analytically or numerically, thus providing a model which involves a significantly lower number of variables than those required for the detailed model of the assembly. The methodology is first tested by comparing the dispersion relations obtained through homogenization with those corresponding to the detailed model of the unit cells and then extended to the comparison of exact and approximate harmonic responses. This comparison is carried out for both one-dimensional and two-dimensional assemblies. The application to three-dimensional structures is not attempted in this work and will be approached in the future without the need for substantial conceptual changes in the theoretical procedure. Hence the presented technique is expected to be applicable to a wide range of periodic structures, with applications ranging from the design of structural elements of mechanical and aerospace interest to the optimization of smart materials with attractive mechanical, thermal or electrical properties.
Design and Validation of a Component Head Injury Criteria Tester for Aerospace Applications
Authors: Lankarani Hamid M. , Koshy C. S. , Thorbole C. K.
Published: June 2008

The compliance with Head Injury Criteria (HIC) specified in 14 CFR 23.562 [1] and CFR 25.562 [2] poses a significant problem for many segments of the aerospace industry. The airlines and the manufacturers of jet transports have made claims of high costs and significant schedule overruns during the development and certification of 16G seats because of the difficulties encountered in meeting this requirement. The current practice is to conduct Full Scale Sled Tests (FSST) on impact sleds. This approach can be expensive, since a new seat may be needed for each test. Moreover, some consider the HIC sensitive to changes in the test conditions, such as sled pulse, seat belt elongation, etc., resulting in HIC results from FSSTs showing poor repeatability. These difficulties make it desirable to devise a cheaper, faster, and more repeatable alternative to FSSTs. This paper describes an attempt to address these issues by designing a device, the National Institute for Aviation Research (NIAR) HIC Component Tester (NHCT) using various multibody tools. This device was then fabricated and its performance evaluated against FSSTs conducted under similar test conditions for some typical impact events that occur in an aircraft cabins e.g. impact with bulkheads. The factors compared for this evaluation are the head impact angle, head impact velocity, HIC, HIC window, peak head C.G. resultant acceleration, average head C.G. resultant acceleration, and head C.G. resultant acceleration profiles. The results of these evaluations show that the NHCT already produces test results that correlate significantly with FSST results for impact targets such as bulkheads and its target envelope is expected eventually to include objects such as seat backs.
Motion Patterns at Rotor Stator Contact
Authors: Ehehalt Ulrich , Hahn Eric , Markert Richard
Published: June 2008

The present paper discusses the various movement patterns during rotor stator contact. Both rotor and stator are assumed to be flexible damped single degree of freedom systems. The contact is described by a flexible viscoelastic model. Dry friction between rotor and stator is taken into account. Despite strong non-linearity due to contact, rotor unbalance causes purely synchronous motions. However, in some circumstances, the synchronous motion may become unstable and the rotor motion turns into a non-synchronous state, which can be very destructive. Non-synchronous motions include backward whirl, sub- and super-harmonic vibration and chaotic motion. The influence of various system parameters on the different types of motion is investigated by numerical simulation. The transients between synchronous to non-synchronous motions are exemplarily demonstrated by run-up and run-down processes. It is shown that different motion types may co-exist. Even in speed regions where the synchronous whirl is stable, non-synchronous motions with rotor stator contact are possible.
A Methodology for Active Control of Multibody Test-Rig for Virtual Simulation of Vehicles Through Acceleration Inputs
Authors: Braccesi Claudio , Cianetti Filippo , Landi Luca
Published: June 2008

Dynamic simulation through Multibody Systems is more and more used for the design of new industrial products to avoid long and expensive experimental tests on them. The research presented in this paper deals with the realization of an actively controlled virtual test-rig, functional for comfort and durability tests of entire vehicles. The virtual test rig, is capable to impose any experimental acceleration to the centers of the four vehicle wheels through four imposed displacements to the actuators. The active control is implemented with four independent degrees of freedom, one for every actuator. In the paper the active controller logic and its automatic setup will be fully explained. Moreover it will be also explained how to avoid the aliasing and the so called “random signal drift” problems. Finally the results of some virtual pave road experiments to an existing vehicle will be presented.
Random Loads Fatigue: The Use of Spectral Methods Within Multibody Simulation
Authors: Braccesi Claudio , Cianetti Filippo , Landi Luca
Published: June 2008

The evaluation of the fatigue damage performed by using the Power Spectral Density function (PSD) of stress and strain state is proving to be extremely accurate for a family of random processes characterized by the property of being stationary. The present work’s original contribution is the definition of a methodology which extracts stress and strain PSD matrices from components modelled using a modal approach (starting from a finite element modelling and analysis) within mechanical systems modelled using multibody dynamic simulation and subject to a generic random load (i.e. multiple-input, with partially correlated inputs). This capability extends the actual stress evaluation scenario (principally characterised by the use of finite element analysis approach) to the multibody dynamic simulation environment, more powerful and useful to simulate complex mechanical systems (i.e. railway, automotive, aircraft and aerospace systems). As regards the fatigue damage evaluation, a synthesis approach to evaluate an equivalent stress state expressed in terms of the PSD function of Preumont’s “equivalent von Mises stress (EVMS)”, starting from the complete stress state representation expressed in terms of PSD stress matrix and easily usable in the consolidated spectral methods, is proposed. This approach allows and has allowed the use of the above methods such as the Dirlik formula as a damage evaluation method. An additional result is the conception and implementation of a frequency domain method for the component’s most probable state of stress, allowing quickly identification of the most stressed and damageble locations. The described methodologies were developed and embedded into commercial simulation codes and verified by using as a test case a simple reference multibody model with a simple flexible component.
A Review of Software Solutions for the Management of New Product Development and Product Family Planning
Authors: Byron Bethany M. , Shooter Steven B.
Published: June 2008

The field of new product development has a number of difficult challenges with which it must contend: shortened production time, greater market share demand, and geographically dispersed teams. Several software systems have been developed to ease these challenges. A representative cross-section of work in the fields of document management, project management, product lifecycle management, and conceptual and family design is examined, including past and current academic work and commercially available software. The scope and features of these projects are examined and compared on a software taxonomy. The potential application of these systems to product families is discussed throughout.
Control of Time-Delay Systems Using Robust Fractional-Order Control and Robust Smith Predictor Based Control
Authors: Lanusse Patrick , Oustaloup Alain
Published: June 2008

Many modifications have been proposed to improve the Smith predictor structure used to control plant with time-delay. Some of them have been proposed to enhance the robustness of Smith predictor based controllers. They are often based on the use of deliberately mismatched model of the plant and then the IMC method can be used to tune the controller. This paper compares the performance of two Smith predictor based controllers including a mismatched model to the performance provided by a fractional order Crone controller which is well known for managing well the robustness and performance tradeoff. It is shown that even if it can simplify the design of (robust) controller, the use of an improved Smith predictor is not necessary to obtain good performance.
Modeling and Simulation of a Laser-Powered Lightcraft Using Advanced Simulation Tools
Authors: Evans John A. , Oghbaei Mojtaba , Anderson Kurt S.
Published: June 2008

This paper outlines efforts toward implementation of a new state-time methodology for dynamic simulation of a six-degree of freedom (6-DOF) model of the Type 200 laser-powered lightcraft. The lightcraft problem is a well-suited application demonstrating the potential advantage of using the state-time formulation as the craft’s temporal domain is much larger than its spatial domain. Indeed, while relatively few processors can be effectively utilized in modeling the vehicle via traditional state-type algorithms, more than 105 processors may be potentially exploited in a state-time dynamic simulation. In this paper, a modified state-time methodology is derived in order to account for impulsive characteristics. This impulsive formulation allows for parallelization not only between impulses but also across impulses. Furthermore, an aerodynamic model fully compatible with the state-time formulation is presented. Validation of the proposed method is obtained by comparing the state-time simulation results with the results of a traditional state-type dynamics algorithm using Autolev software.