bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration of the Vertical Rigid Rotor Supported by a Repulsive-Type Magnetic Bearing: Effects of Both the Axial Displacement and the Magnetical Anisotropicities of Magnets
Authors: Inoue Tsuyoshi , Ishida Yukio , Sugai Tomohiro
Published: May 2009

Magnetic bearing is considered for the usage in various industries. This paper investigates vibration of the rotating shaft supported passively by a repulsive-type magnetic bearing. The permanent magnet on the market not only has strong nonlinear force characteristics, but also may have a few percents of non-uniform magnetization characteristics. Also nonlinear force characteristics change as axial displacement of the shaft. Restoring force of a repulsive-type magnetic bearing is evaluated numerically considering the effects of both the axial displacement of the shaft and the magnetical anisotropicities of the inner and outer magnets. The occurrences of not only the linear and nonlinear parametric characteristics, but also the excitational forces for each pattern of magnetical anisotropicities are observed and they are evaluated in terms of the axial displacement. Furthermore, the influence of each magnetical anisotropicity pattern on the occurrences of various resonance phenomena is clarified.
Updating Uncertainty Assessments: A Comparison of Statistical Approaches
Authors: Aughenbaugh Jason Matthew , Herrmann Jeffrey W.
Published: May 2009

The performance of a product that is being designed is affected by variations in material, manufacturing process, use, and environmental variables. As a consequence of uncertainties in these factors, some items may fail. Failure is taken very generally, but we assume that it is a random event that occurs at most once in the lifetime of an item. The designer wants the probability of failure to be less than a given threshold. In this paper, we consider three approaches for modeling the uncertainty in whether or not the failure probability meets this threshold: a classical approach, a precise Bayesian approach, and a robust Bayesian (or imprecise probability) approach. In some scenarios, the designer may have some initial beliefs about the failure probability. The designer also has the opportunity to obtain more information about product performance (e.g. from either experiments with actual items or runs of a simulation program that provides an acceptable surrogate for actual performance). The different approaches for forming and updating the designer’s beliefs about the failure probability are illustrated and compared under different assumptions of available information. The goal is to gain insight into the relative strengths and weaknesses of the approaches. Examples are presented for illustrating the conclusions.
Slow-Time Changes in Human Muscle Fatigue Are Fully Represented in Movement Kinematics
Authors: Song Miao , Segala David B. , Dingwell Jonathan B. , Chelidze David
Published: May 2009

Muscle fatigue is exhibited in individuals who partake in repetitive movements for an extensive duration of time. The objective of this study was to identify correlation, if any, between movement kinematics and muscle electrical activity (EMG). Movement kinematics and EMG signals were measured and recorded from the lower extremities of stationary elite cyclists. Standard statistical metrics (SSM) and phase space warping (PSW) based features were extracted from the recorded fast-time time series for consecutive intermediate time intervals. The SSM based features were composed of higher moments, fractal dimension, correlation sum, power spectral density, and cross-correlation. The PSW based features were subject to quantifying short-time differences between the fatigued and unfatigued reconstructed phase spaces. The slow-time manifolds describing global fatigue dynamics in these feature spaces were extracted using smooth orthogonal decomposition (SOD). Mean and median frequencies from the EMG data were calculated to describe the local fatigue dynamics in each muscle. There were very close correlations between the EMG and kinematics data based global fatigue features. Also, the 4 and 5 dimensional slow time manifolds (corresponding to PSW and SSM based features, respectively) fully represented the local fatigue dynamics in all the muscles as described by the EMG data. Therefore, for this particular context, the fatigue information present in the standard EMG analysis was fully represented in the SOD based slow-time features extracted from the kinematic data. Furthermore, the SOD based analysis gave estimates of effective dimensionality of muscle fatigue dynamics.
Meshing Theory and Simulation of Noninvolute Beveloid Gears With Crossed Axes
Authors: Yu Guangbin , Shi Yuxiang , Wang Wei , Li Guixian
Published: May 2009

Based on the space engagement theory, a special type of non-involute beveloid gears meshing with line contact between crossed axes has been studied in this paper. The engagement equation and tooth profile equation have been presented by applying the theory of gearing. Meanwhile the tooth profile errors and axial errors have been calculated by means of numerical analysis in this paper. The changes of these errors and the main factors have been studied. As a numerical example, the three-dimensional simulation of beveloid gears between crossed axes has been finished by means of the CAD system, Pro/Engineer. A new way of gear tooth modification is developed based on the space engagement theory for the first time in this paper. By improving the wheel gear grinder of large plane grinding, the paper has provided the tooth modification method of manufacturing noninvolute beveloid gears meshing with line contact between crossed axes. Finally, an example and its calculation results are presented.
Reconstructing Polyhedral CAD Models by Recognizing Extrusion Features From Single-View Drawings
Authors: Suh Yong S.
Published: May 2009

At the conceptual product design stage, designers prefer sketching initial design ideas on paper before using more sophisticated 3D CAD systems for their creativity and flexible design changes. At the later detailed design stages, however, precise 3D CAD modeling is a better choice for design analyses and downstream manufacturing applications. For an integrated digital product development, the 2D drawings need to be converted to 3D CAD models manually through some laborious and time-consuming processes. For decades, many researchers have contributed to the studies on reconstructing 3D geometric models from 2D sketches, but few describe constructing parametric feature-based CAD models that are currently widely used in the detailed design stages. In this paper, a procedure for constructing a feature-based 3D CAD model directly from a single-view 2D drawing is presented. The input sketch is assumed to be an exact orthogonal projection of a 3D model viewed at a general orientation. The model geometry is limited such that it can be constructed by a Boolean combination of extrusions of polygonal profiles.
A Proposed Method to Preserve Knowledge and Information by Use of Knowledge Enabled Engineering
Authors: Sandberg Stefan , Na¨sstro¨m Mats
Published: May 2009

Today’s automotive industry produces more new car models in a shorter time than ever before. Every car model comes in many different versions regarding number of doors, engine, transmission etc while being built on a platform strategy. This leads to a lot of different knowledge and information that needs to be tracked for the different components in addition to other information e.g. what function does design features have, why is this radius not smaller etc. Volvo Car Corporation (VCC) is in need of an effective method to save and present all this knowledge and information today. This paper describes a new method, to gather and save knowledge and information about car body parts also called body-in white, which was implemented in a demonstrator and tested and evaluated on VCC.
A Framework for Automatic Causality Extraction Using Semantic Similarity
Authors: Kim Sanghee , Bracewell Rob H. , Wallace Ken M.
Published: May 2009

Textual documents are the most common way of storing and distributing information within organizations. Extracting useful information from large text collections is therefore the goal of every organization that would like to take advantage of the experience encapsulated in those texts. Entering data using a free text style is easy, as it does not require any special training. However, unstructured texts pose a major challenge for automatic extraction and retrieval systems. Generally, deep levels of text analysis using advanced and complex linguistic processing are necessary that involve computational linguistic experts and domain experts. Linguistic experts are rare in engineering organizations, which thus find it difficult to apply and exploit such advanced extraction techniques. It is therefore desirable to minimize the extensive involvement of linguist experts by learning extraction patterns automatically from example texts. In doing so, the analysis of given texts is necessary in order to identify the scope and suitable automatic methods. Focusing on causality reasoning in the field of fault diagnosis, the results of experimenting with an automatic causality extraction method using shallow linguistic processing are presented.
Thermoelastic Growth of an Auxiliary Bearing Surface Due to Repeated Rotor Dynamic Contact and Rubbing
Authors: Yong Woon Yik , Keogh Patrick S.
Published: May 2009

There are a number of important issues relating to rotor/auxiliary contact in magnetic bearing systems. Primarily, an auxiliary bearing must prevent rotor/stator contact during events such as system power failure and large scale input disturbances. The auxiliary bearing may experience repeated contacts ranging from short timescale transient events to longer timescale rubs. While many studies of the rotor dynamic responses have been undertaken and reported in the open literature, the associated problems relating to thermoelastic distortion have received relatively little attention. These are important since high initial slip speeds will lead to localized heating that may cause large and highly transient surface temperature changes. Repeated contact events or repeated rubbing over a surface deformation may also lead to an accumulative increase in the level of surface distortion. This paper presents a study of the methodology that could be used to assess the overall thermoelastic distortion between a rotor and an auxiliary bearing. It shows that an assessment of the dynamic accumulation of distortion is possible from fundamental studies of individual contact events. The results from case studies highlight the possible problems that could be caused by clearance reductions during operation.
Parametric Resonances of Nonlinearly Viscoelastic Rings Subject to a Pulsating Pressure
Authors: Lacarbonara Walter , Antman Stuart S.
Published: May 2009

Refined theories are employed for accurate predictions of the onset of the parametric instabilities of nonlinearly viscoelastic rings subject to a hydrostatic pressure. The breathing motions are first investigated and closed-form conditions ensuring motions of the hardening or softening type are derived showing that this mode nonlinearity depends on the constitutive law and the static part of the hydrostatic pressure. The parametric instability regions and the ensuing 2-period breathing motions are obtained employing an asymptotic approach. Thereafter, the parametric instabilities of the flexural motions are investigated via a direct asymptotic approach and it is shown that these motions can also be softening or hardening depending on the low-order parts of the constitutive law. The parametric instabilities cause high-amplitude coupled-mode flexural motions involving simultaneously the directly excited mode and its companion mode.
Stability Analysis and Computation of Solutions of Nonlinear Delay Differential Algebraic Equations With Time Periodic Coefficients
Authors: Deshmukh Venkatesh
Published: May 2009

Stability theory of Nonlinear Delay Differential Algebraic Equations (DDAE) with periodic coefficients is proposed with a geometric interpretation of the evolution of the linearized system. First, a numerical algorithm based on direct integration by expansion in terms of Chebyshev polynomials is derived for linear analysis. The proposed algorithm is shown to have deeper connections with and computationally less cumbersome than the solution of the underlying semi-explicit system via a similarity transformation. The stability of time periodic DDAE systems is characterized by the spectral radius of a finite dimensional approximation or a “monodromy matrix” of a compact infinite dimensional operator. The monodromy operator is essentially a map of the Chebyshev coefficients of the state form the delay interval to the next adjacent interval of time. The monodromy matrix is obtained by a similarity transformation of the momodromy matrix of the associated semi-explicit system. The computations are entirely performed in the original system form to avoid cumbersome transformations associated with the semi-explicit system. Next, two computational algorithms are detailed for obtaining solutions of nonlinear DDAEs with periodic coefficients for consistent initial functions.
Cardiac Alternans Arising From an Unfolded Border-Collision Bifurcation
Authors: Zhao Xiaopeng , Schaeffer David G. , Berger Carolyn M. , Krassowska Wanda , Gauthier Daniel J.
Published: May 2009

Following an electrical stimulus, the transmembrane voltage of cardiac tissue rises rapidly and remains at a constant value before returning to the resting value, a phenomenon known as an action potential. When the pacing rate of a periodic train of stimuli is increased above a critical value, the action potential undergoes a period-doubling bifurcation, where the resulting alternation of the action potential duration is known as alternans in the medical literature. In principle, a period-doubling bifurcation may occur through either a smooth or a nonsmooth mechanism. Previous experiments reveal that the bifurcation to alternans exhibits hybrid smooth/nonsmooth behaviors, which is due to large variations in the system’s properties over a small interval of bifurcation parameter. To reproduce the experimentally observed hybrid behaviors, we have developed a model of alternans that exhibits an unfolded border-collision bifurcation. Excellent agreement between simulation of the model and experimental data suggests that features of the unfolded border-collision model should be included in modeling cardiac alternans.
Generalization of Topological Sensitivity and Its Application to Defeaturing
Authors: Turevsky Inna , Gopalakrishnan Sankara Hari , Suresh Krishnan
Published: May 2009

A particularly challenging problem in CAD/CAE is the handling of small geometric details during finite element analysis (FEA). The presence of such details can significantly increase the computational complexity of FEA, while hindering its automation. Therefore, designers typically resort to defeaturing or detail removal, where the offending geometric details are suppressed prior to analysis. However, an inevitable consequence of defeaturing is that it can significantly alter the behavior of the CAE model. In this paper, we address the following question: Given the behavior of the defeatured CAE model, how does one estimate the behavior of the original (reference) CAE model? In this paper, we extend the concept of topological sensitivity, and apply to defeaturing analysis, in the following sense. Classic topological sensitivity captures the first-order change in quantities of interest when small spherical holes are created within an existing geometry. Here, we consider an arbitrary cluster of small internal & boundary features, and provide a fundamental theory and specific algorithms to compute the net impact of deleting such features. The theory and algorithm are illustrated through numerical experiments.
Design of a High-Speed Spherical Four-Bar Mechanism for Use in a Motion Common in Assembly Processes
Authors: Murray Andrew P. , Pierrot Franc¸ois
Published: May 2009

In this paper, we present the mechanical design of a spherical four-bar mechanism for performing a motion common in manufacturing and assembly processes. The mechanism is designed to create, in a single, smooth motion, the combined rotation of a body by 90 degrees about one axis with a 90 degree rotation about an axis perpendicular to the first. A spherical four-bar mechanism is pursued as the basis for the design because the reorientation is produced mechanically rather than via a control scheme typical when higher degree of freedom systems are utilized. The design initiates with the kinematic synthesis of the spherical mechanism to guide a body through two orientations. The next step in the design is to refine the spherical fourbar based on manufacturing and operational concerns. As one of the challenges of utilizing these four-bars is tuning the starting and ending angle for the mechanism’s motion, a sensitivity analysis is performed to gauge the needed accuracy. Finally, there are details and a discussion of the proposed mechanical design.
A Multi-Level Freeform Surface Feature Model
Authors: Nyirenda Paulos J. , Bronsvoort Willem F.
Published: May 2009

Feature modelling is a valuable technology to define and manipulate product models through advanced operations. Parameters and constraints can be included in feature models to represent particular design intent. In this way, entire families of shapes, not just specific instances, can be modelled. Freeform surface feature modelling, which extends the concept of feature modelling to freeform shapes, still suffers from a number of shortcomings as regards parametric modelling. In particular, it lacks good facilities to add new parameters to a model. We present a multi-level freeform surface feature model that can be used to implement such facilities. The model contains an unevaluated, a partially evaluated and an evaluated level. The paper describes the three levels and how these are generated.
Analysis of Perceived Creativity and Design Team Interaction
Authors: Kim Myung Sook , Kim Yong Se
Published: May 2009

Creativity is an influential factor to change the world. With the information explosion and changing the social environment, the development of innovation will increasingly require team interaction in the process of problem solving. The present research was to explore about subjective perception on creativity in relation to personal creativity modes, and to analyze team interaction and the process of problem solving from the perspective of personal creativity modes. We provided team activities promoting self-awareness about creativity mode and idea generation for problem solving, and analyzed team member’s self-description on perceived own personal creative characteristics. The results indicated correspondence between perceived personal creativity characteristics and personal creativity mode identified through Personal Creativity Mode Test (PCMT). Also, the analysis of team interaction and problem solving process reflected some patterns according to diverse personal creativity modes. These findings confirm that people can perceive their own creativity in accordance with the results of a test and that PCMT can be useful in selecting and forming design teams and it helps understanding characteristics of individual members in their team activities. Such understanding could provide a guidance to develop training programs to improve design team creativity.
An Open Source Application for Archiving Product Design Information
Authors: Bohm Matt R. , Vucovich Jayson P. , Stone Robert B.
Published: May 2009

This paper describes an open source computer application developed at the University of Missouri - Rolla (UMR) for archiving product design information. The Repository Entry application is designed to work with the UMR design repository to record and upload product information. Written in C++, the application and user interface is compiled in Qt allowing for native Macintosh and Windows executables. The Repository Entry application can record all of the design information types allowed by the repository including: artifact-, function-, failure-, physical-, performance-, sensory- and media-related information types. By using XML, files can be seamlessly transferred between the Windows and Macintosh entry application versions as well as the online repository. Through an example product the procedure of using the entry application to record and upload design information is demonstrated. The result of this research is a fully functional, easy to use and multi-platform application to aid in the design information archival and reuse process.
A Perspective Projection Tutoring System With Motivation Diagnosis and Planning
Authors: Kim Yong Se , Cha Hyun Jin , Yoon Tae Bok , Lee Jee-Hyoung
Published: May 2009

Motivation is a paramount factor to student success. Although it is well known that the learner’s motivation and emotional state in educational contexts are very important, they have not been fully addressed in intelligent tutoring systems (ITS). In this paper, a method for integrated motivation diagnosis and motivational planning is described in a manner applied to an operable system. For the motivational diagnosis rules, three different channels of data (performance from interaction with the system, verbal communication, and feedbacks) are combined. For the motivational planning rules, four different strategies (different learning process, helps, different teaching strategies, and arousal questions or feedbacks) are combined. By applying the mechanisms, a tutoring system for the topic of perspective projection with motivation diagnosis and motivational planning on a multiagent system with fuzzy logic has been implemented.
Mechanical Considerations for Modeling of Vibration-Based Energy Harvesters
Authors: Erturk Alper , Inman Daniel J.
Published: May 2009

The idea of supplying energy for low-power devices such as MEMS and remote sensors by converting the ambient vibrations to electrical energy through energy harvesters has been subject to many papers in recent years. One typical energy harvester is a cantilevered beam with one or more layers of piezoelectric material (PZT) connected to a harvesting circuit by means of electrodes. The literature includes attempts to provide the electromechanical model of this type of energy harvesters and one frequently used approach is the single-degree-of-freedom (SDOF) modeling which is only applicable for the case of excitation around the resonance frequency. In this work, the exact analytical solution of the base excitation problem is given for a clamped-free Euler-Bernoulli beam since the excitation of the harvester is generally due to its base motion in real life applications. The base motion is described by translation and small rotation and is not restricted to be harmonic in time. The general solution is then reduced to the case of harmonic base excitation for comparison with the corresponding SDOF model. It is shown that the commonly accepted form of the SDOF model may yield highly inaccurate results. A correction factor, which should also appear in the electromechanically coupled equations, is introduced for improving the SDOF model.
Conservative Estimations of Reliability With Limited Sampling
Authors: Picheny Victor , Kim Nam-Ho , Haftka Raphael T.
Published: May 2009

The objective of this paper is to provide a method of safely estimating reliability based on small samples. First, it is shown that the commonly used estimators of the parameters of the normal distribution function are biased, and they tend to lead to unconservative estimates of reliability. Then, two ways of making this estimation conservative are proposed: (1) adding constraints when a distribution is fitted to the data to bias it to be conservative, and (2) using the bootstrap method to estimate the bias needed for a given level of conservativeness. The relationship between the accuracy and the conservativeness of the estimates is explored for a normal distribution. In particular, detailed results are presented for the case when the goal is 95% likelihood to be conservative. The bootstrap approach is found to be more accurate for this level of conservativeness. It is then applied to the reliability analysis of a composite panel under thermal loading. Finally, we explore the influence of sample sizes and target probability of failure on estimates quality, and show that for a constant level of conservativeness, small samples and low probabilities can lead to a high risk of large overestimation while this risk is limited to a very reasonable value for samples above.
Impact of Tool Geometry on Cutting Dynamics
Authors: Dassanayake Achala V. , Suh C. Steve
Published: May 2009

Machining stability in response to changing tool geometry is studied using a 3D turning model that considers coupled tool-workpiece dynamics subject to nonlinear regenerative cutting forces [1]. As tool geometry varies with the specified tool angles, values of tool rake angle, side cutting edge angle, and inclination angle are considered in the study as the controlled parameters. In the presented model, cutting force components in the X, Y, and Z directions vary with the variations of tool geometry, thus resulting in changes in cutting dynamics — a major feature not attainable using 1D models. It is found that tool geometry does have a significant effect on machining stability. In contrast to commonly used stability charts that are created by considering varying cutting speed and depth-of-cut (DOC), the study makes an observation that tool geometry can be a variable effective in restoring an unstable system back to stability without having to resort to changing cutting speed, feed rate or DOC.
Identifying Risk at the Conceptual Phase of Product Design: A Software Solution
Authors: Sundaram Karthik , Chakravarty Abhishek , Grantham Lough Katie , Ditch Derek
Published: May 2009

This paper introduces RED (Risk in Early Design) software developed by the R.I.S.K by Design Lab at University of Missouri-Rolla. The RED software is a risk analysis tool that enables failure prevention to begin during the conceptual phase of product design. The main focus of the paper is describing the software architecture and application. Its unique graphical user interface allows designers to simply select the functions of the system being designed and the software immediately generates a risk analysis report. This analysis categorizes risk likelihood and consequence elements for a product by translating the recorded information about function and failure. An example describing the software’s use in the design process is also presented.
Parameter Optimization of a Vibration-Based Energy Harvester With an RL Electric Circuit
Authors: Renno Jamil M. , Daqaq Mohammed F. , Farmer Justin R. , Inman Daniel J.
Published: May 2009

An alternative circuit to improve the performance of a vibration-based energy harvester is proposed. The harvesting device considered consists of a piezoceramic element operating in the {33} direction. In normal operating conditions, piezoceramics experience small deflection and hence the small signal linear constitutive law of piezoelectricity is adopted for the scope of this work. Typically, vibration-based energy harvesters are designed to operate at the resonance or antiresonance frequencies. This condition might be tolerable in many cases, but is often difficult to realize in real-life applications. In this work, the authors propose adding an inductor to the harvesting circuit. It is shown that the addition of this simple electric element modifies the performance remarkably in a qualitative and quantitative manner. The maximum power values obtained at the resonance and antiresonance frequencies can be achieved at any frequency ratio if optimal electric elements are used. This allows for harvesting a constant optimal power everywhere in the frequency domain. Further investigation reveals the existence of a singularity at low damping ratios (below a bifurcation damping ratio). In that case, the optimization scheme yields a negative value for the optimal inductance between the resonance and antiresonance frequencies. However, this singularity is not experienced at a high damping ratio (beyond a bifurcation damping ratio). Moreover, for high damping ratios, it is shown that the proposed circuit is superior to a circuit that does not deploy an inductor.
A Genetic Algorithm Based Procedure for Extracting Optimal Solutions From a Morphological Chart
Authors: Tiwari Santosh , Summers Joshua , Fadel Georges
Published: May 2009

A novel approach using a genetic algorithm is presented for extracting globally satisfycing (Pareto optimal) solutions from a morphological chart where the evaluation and combination of “means to sub-functions” is modeled as a combinatorial multi-objective optimization problem. A fast and robust genetic algorithm is developed to solve the resulting optimization problem. Customized crossover and mutation operators specifically tailored to solve the combinatorial optimization problem are discussed. A proof-of-concept simulation on a practical design problem is presented. The described genetic algorithm incorporates features to prevent redundant evaluation of identical solutions and a method for handling of the compatibility matrix (feasible/infeasible combinations) and addressing desirable/undesirable combinations. The proposed approach is limited by its reliance on the quantifiable metrics for evaluating the objectives and the existence of a mathematical representation of the combined solutions. The optimization framework is designed to be a scalable and flexible procedure which can be easily modified to accommodate a wide variety of design methods that are based on the morphological chart.
An Investigation on New Numerical Methods for Molecular Dynamics Simulation
Authors: Schafer Nick , Serban Radu , Negrut Dan
Published: May 2009

Explicit integrators have found common use in Molecular Dynamics (MD) simulations because they are easy to implement and work well under many conditions. However, in other classical mechanics applications that require the numerical solution of the equations of motion for complex systems, explicit methods have encountered major difficulties. In these cases, the state of the art relies on implicit methods, which are stable under large time steps and therefore can be used to decrease the number of integration steps necessay for a simulation. This in turn results in an overall reduction of CPU time that opens the door to an increase in the dimension of the problem that can be considered. The premise of this work is that numerical methods that are suitable for efficient simulation of mechanical systems will lead to significant gains when used in MD. The goal of the proposed work is to investigate this assumption by comparing in terms of accuracy and efficiency the Hilber-Hughes-Taylor (HHT) integrator against current explicit MD integrators for a set of two benchmark problems.
Bayesian Reliability Based Design Optimization Using Eigenvector Dimension Reduction (EDR) Method
Authors: Wang Pingfeng , Youn Byeng D. , Wells Lee J.
Published: May 2009

In the last decade, considerable advances have been made in Reliability-Based Design Optimization (RBDO). It is assumed in RBDO that statistical information of input uncertainties is completely known (aleatory uncertainty), such as a distribution type and its parameters (e.g., mean, deviation). However, this assumption is not valid in practical engineering applications, since the amount of uncertainty data is restricted mainly due to limited resources (e.g., man-power, expense, time). In practical engineering design, most data sets for system uncertainties are insufficiently sampled from unknown statistical distributions, known as epistemic uncertainty. Existing methods in uncertainty based design optimization have difficulty in handling both aleatory and epistemic uncertainties. To tackle design problems engaging both epistemic and aleatory uncertainties, this paper proposes an integration of RBDO with Bayes Theorem, referred to as Bayesian Reliability-Based Design Optimization (Bayesian RBDO). However, when a design problem involves a large number of epistemic variables, Bayesian RBDO becomes extremely expensive. Thus, this paper presents a more efficient and accurate numerical method for reliability method demanded in the process of Bayesian RBDO. It is found that the Eigenvector Dimension Reduction (EDR) Method is a very efficient and accurate method for reliability analysis, since the method takes a sensitivity-free approach with only 2n+1 analyses, where n is the number of aleatory random parameters. One mathematical example and an engineering design example (vehicle suspension system) are used to demonstrate the feasibility of Bayesian RBDO. In Bayesian RBDO using the EDR method, random parameters associated with manufacturing variability are considered as the aleatory random parameters, whereas random parameters associated with the load variability are regarded as the epistemic random parameters. Moreover, a distributed computing system is used for this study.
An Investigation of the Influence of Shaft Misalignments on Bending Stresses of Helical Gear With Lead Crown
Authors: Hotait M. A. , Talbot D. , Kahraman A.
Published: May 2009

In this study, combined influence of shaft misalignments and gear lead crown on the load distribution and tooth bending stresses is investigated experimentally. A set of helical gear pairs having various amounts of lead crown was tested under loaded, low-speed conditions with varying amounts of tightly-controlled shaft misalignments. Gear teeth were instrumented through strips of strain gauges along the face width of gears at the tooth fillet region near the start of active profile. Variations of root strains along the face width were recorded for different levels of shaft misalignments and gear lead crown. At the end, the experimental results were correlated to the predictions of a gear load distribution model and recommendations were made on how much lead crown is optimal for a given misalignment condition.
Type Synthesis of Six-DOF Wrist-Partitioned Fully Parallel Manipulators
Authors: Kong Xianwen , Gosselin Cle´ment M.
Published: May 2009

A six-DOF wrist-partitioned fully parallel manipulator is a parallel manipulator in which three of the six actuated joints are used to control the position of a point on the moving platform while the other three are further used to control the orientation of the moving platform. Such parallel manipulators are in fact the parallel counterparts of the wrist-partitioned serial manipulators, which are widely used in industry. Unlike parallel manipulators of a general structure, a six-DOF wrist-partitioned fully parallel manipulator usually has simple kinematic characteristics such as its forward displacement analysis and singularity analysis are easy to solve. This paper deals with the type synthesis of six-DOF wrist-partitioned fully parallel manipulators. An approach is first proposed for the type synthesis of this class of parallel manipulators. Using the proposed approach, six-DOF wrist-partitioned fully parallel manipulators can be constructed from the types of three-DOF non-overconstrained spherical parallel manipulators. A large number of six-DOF wrist-partitioned fully parallel manipulators are then obtained, and several types of practical relevance are also identified.
Vibration Behavior of Thick Composite Laminated Plates Subject to In-Plane Pre-Stress Loading
Authors: Fiedler Lars , Lacarbonara Walter , Vestroni Fabrizio
Published: May 2009

The vibration behavior of rectangular laminated composite plates subject to in-plane loading is investigated employing a global higher-order theory. The displacement field is expanded in the thickness direction in a complete polynomial series with arbitrary degree whereas the series coefficients, function of the in-plane coordinates, are expressed, according to Ritz’s method, as a superposition of admissible functions. The elastic and geometric stiffness matrices as well as the mass matrix are obtained from the energy functionals in terms of the generalized coordinates. The problem is suitably nondimensionalized so as to single out the independent parameters. Variations of the lowest frequencies with the width-to-thickness ratio and with the ratio between the in-plane elastic moduli are investigated to ascertain the sensitivity of the vibration behavior with respect to these parameters. Effects of the lamination scheme on the vibration properties are assessed.
A Comparative Study of Uncertainty Propagation Methods for Black-Box Type Functions
Authors: Lee Sang Hoon , Chen Wei
Published: May 2009

It is an important step in deign under uncertainty to select an appropriate uncertainty propagation (UP) method considering the characteristics of the engineering systems at hand, the required level of UP associated with the probabilistic design scenario, and the required accuracy and efficiency levels. Many uncertainty propagation methods have been developed in various fields, however, there is a lack of good understanding of their relative merits. In this paper, a comparative study on the performances of several UP methods, including a few recent methods that have received growing attention, is performed. The full factorial numerical integration (FFNI), the univariate dimension reduction method (UDR), and the polynomial chaos expansion (PCE) are implemented and applied to several test problems with different settings of the performance nonlinearity, distribution types of input random variables, and the magnitude of input uncertainty. The performances of those methods are compared in moment estimation, tail probability calculation, and the probability density function (PDF) construction. It is found that the FFNI with the moment matching quadrature rule shows good accuracy but the computational cost becomes prohibitive as the number of input random variables increases. The accuracy and efficiency of the UDR method for moment estimations appear to be superior when there is no significant interaction effect in the performance function. Both FFNI and UDR are very robust against the non-normality of input variables. The PCE is implemented in combination with FFNI for coefficients estimation. The PCE method is shown to be a useful approach when a complete PDF description is desired. Inverse Rosenblatt transformation is used to treat non-normal inputs of PCE, however, it is shown that the transformation may result in the degradation of accuracy of PCE. It is also shown that in black-box type of system the performance and convergence of PCE highly depend on the method adopted to estimate its coefficients.
A Pseudo-Rigid-Body Model for Rolling-Contact Compliant Beams
Authors: Mackay Allen B. , Magleby Spencer P. , Howell Larry L.
Published: May 2009

This paper presents a pseudo-rigid-body model (PRBM) for rolling-contact compliant beams (RCCBs). The loading conditions and boundary conditions for the RCCB can be simplified to an equivalent cantilever beam that has the same force-deflection characteristics as the RCCB. Building on the PRBM for cantilever beams, this paper defines a model for the force-deflection relationship for RCCBs. The definition of the RCCB PRBM includes the pseudo-rigid-body model parameters that determine the shape of the beam, the length of the corresponding pseudo-rigid-body links and the stiffness of the equivalent torsional spring. The behavior of the RCCB is parameterized in terms of a single parameter defined as clearance, or the distance between the contact surfaces. RCCBs exhibit a unique force-displacement curve where the force is inversely proportional to the clearance squared.
Sensitivity Analysis of Dynamic Equilibrium Positions in Multibody Systems Undergoing Prescribed Rotational Motions
Authors: Choi Dong Hwan , Yoo Hong Hee , Wickert Jonathan A.
Published: May 2009

Multibody systems that undergo a prescribed rotational motion arise in such engineered systems as robots, spacecraft, propulsion and power generation systems, and certain sensors and actuators. The sensitivity of the system’s response to changes in the design variables is important for optimization and trade-off studies, as well as for understanding the implications of manufacturing tolerances. A general formulation is developed for analytically calculating the first-order design sensitivities of coordinate values for a multibody system’s dynamic equilibrium state during prescribed rotational motions. The method is based upon the use of relative coordinates, and a velocity transformation technique, and it is applicable to multibody systems having open or closed loop configurations. To illustrate effectiveness, accuracy, and computational efficiency, the present method is applied in three examples, and the sensitivities obtained analytically are compared with those obtained by the standard finite difference method. The finite difference approach is particularly sensitive to the choice of step size near a critical speed, and its implementation is generally more costly that the present method. In particular, there is a zero-sensitivity point at which the equilibrium configuration is insensitive to small perturbations in the design parameter’s value. That condition can be a useful design point to the extent that manufacturing tolerance and variation in design parameter’s values have no effect on dynamic equilibrium positions.
Loads on a Harmonically Oscillating Cylinder
Authors: Marzouk Osama A. , Nayfeh Ali H.
Published: May 2009

A harmonic motion of a cylinder acts as a forcing source to the near wake. Depending on the amplitude and frequency of this motion, the lift exerted on the cylinder may be synchronized or not synchronized with the frequency of the motion. Here, we numerically investigate the behavior of the wake, particularly the induced forces on the cylinder, at a low Reynolds number when the forcing frequency is varied from half to twice the shedding frequency of the wake. Within the synchronization region, an abrupt change in the wake, reflected in a discontinuity in the lift, leads to two different flow modes. In the first mode, increasing the motion frequency causes the lift to increase; whereas in the second mode, this relation is reversed. We analyzed the behavior outside the synchronization region, where the lift is not synchronized with the motion. Poincare´ sections, phase portraits, and spectral analysis were used to characterize different behaviors (e.g., period-n, quasi-periodic, and chaos) of the lift and drag. Also, we performed nonstationary analysis in which the cylinder frequency was varied with different rates and observed typical nonstationary responses in which the jumps were eliminated.
Assessment Criteria for the Conceptual Design of Six-Bar Linkages
Authors: Soh Gim Song , McCarthy J. Michael
Published: May 2009

The synthesis of six-bar linkages can yield a number of design candidates for a variety of linkage structures. Assessment criteria that sort prospective candidates are needed to assist the designer in finding effective linkage designs for further study. In this paper, we present the criteria based on easily computed measures that describe the shape and size of the linkage. These criteria are used to sort designs in four case studies, where we had previously found successful linkages by exhaustive examination.
Kinematic Synthesis With Contact Direction and Curvature Constraints on the Workpiece
Authors: Robson Nina Patarinsky , McCarthy J. Michael
Published: May 2009

In this paper, we consider the synthesis of a planar RR chain that guides a rigid body, or workpiece, such that it does not violate normal direction and curvature constraints imposed by contact with objects in the environment. These constraints are transformed into conditions on the velocity and acceleration of points in the moving body. We use this to formulate the synthesis equations for an RR chain, which are solved by algebraic elimination. An example of the design of a planar RR linkage and a four-bar chain in which the coupler maintains in contact with two objects in two locations is used to illustrate the results.
An Extension of the Commonality Index for Product Family Optimization
Authors: Khajavirad Aida , Michalek Jeremy J.
Published: May 2009

One critical aim of product family design is to offer distinct variants that attract a variety of market segments while maximizing the number of common parts to reduce manufacturing cost. Several indices have been developed for measuring the degree of commonality in existing product lines to compare product families or assess improvement of a redesign. In the product family optimization literature, commonality metrics are used to define the multi-objective tradeoff between commonality and individual variant performance. These metrics for optimization differ from indices in the first group: While the optimization metrics provide desirable computational properties, they generally lack the desirable properties of indices intended to act as appropriate proxies for the benefits of commonality, such as reduced tooling and supply chain costs. In this paper, we propose a method for computing the commonality index introduced by Martin and Ishii using the available input data for any product family without predefined configuration. The proposed method for computing the commonality index, which was originally defined for binary formulations (common / not common), is relaxed to the continuous space in order to solve the discrete problem with a series of continuous relaxations, and the effect of relaxation on the metric behavior is investigated. Several relaxation formulations are examined, and a new function with desirable properties is introduced and compared with prior formulations. The new properties of the proposed metric enable development of an efficient and robust single-stage gradient-based optimization of the joint product family platform selection and design problem, which is examined in a companion paper.
A Magnetorheological Actuation System: Part I — Testing
Authors: John Shaju , Yoo Jin-Hyeong , Wereley Norman M.
Published: May 2009

There is a demand for compact hybrid actuation systems which combines actuation and valving systems in a compact package. Such self-contained actuation systems have potential applications in the field of rotorcraft (as active pitch links) and automotive engineering (as active vibration control devices). Hybrid hydraulic actuation systems, based on frequency rectification of the high frequency motion of an active material, can be used to exploit the high bandwidth of smart material to design devices with high force and stroke. Magnetorheological (MR) fluids are active fluids whose viscosity can be changed through the application of a magnetic field. By using MR fluids as the hydraulic fluid in such hybrid devices, a valving system with no moving parts can be implemented. Such a system will be attractive in rotorcraft applications with large centrifugal force loading. Thus, MR fluids can be used to control the motion of an output cylinder. The MR fluid based valves can be configured in the form of a Wheatstone bridge to produce bi-directional motion in an output cylinder by alternately applying a magnetic field in the two arms of the bridge. In this study, the actuation is performed using a compact Terfenol-D stack driven actuator. The frequency rectification of the stack motion is done using reed valves. This actuator and valve configuration form a compact hydraulic system with fluidic valves. The advantages of such systems are that part count is low, absence of moving parts and the possibility of continuous controllability of the output cylinder. By applying varying magnetic fields in the arms of the bridge (by applying different currents to the coils), the differential pressure acting on the output cylinder can be controlled. The description of the experimental setup, the tests performed and the experimental results are presented in this paper.