bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibration Analysis of Rotors in Rolling Contact: Laboratory Application and Scaling Group
Authors: Cotsaftis Michel , Keskinen Erno , Miettinen Juha , Nuutila Olli , Salmenpera Pekka
Published: June 2008

It is mainly shown that, from their basic origin, vibration rotor modes are following a fixed pattern which has been theoretically analyzed. Various perturbation effects related to geometrical or physical defects are evaluated. Three main classes of modes are distinguished which correspond to different origins: global “outside” modes, “static” rotating rotor deformation modes, and real dynamic excited deformation modes representing the only power sink strictly related to rolls deformation. Good agreement is found for measurements from an industrial paper mill plant operating unit and for experimental observations from a laboratory experiment with large mode coupling. In both cases, most of observed modes are belonging to the first two classes, which can be cured aside by appropriate respective frame shielding and roll grinding. For the last class, a continuous three parameter transformation group is constructed so that the industrial unit and the university apparatus both belong to it, allowing to study properties of the first one on the more manageable second one. Because the modes are sharply peaked due to metal stiffness and weak damping, there exists broad rotation frequency windows where the total mode amplitude is small enough for the system to be preferentially operated.
Levy Flights Over Quantum Paths
Authors: Laskin Nick
Published: June 2008

An impact of integration over the paths of the Le´vy flights on the quantum mechanical kernel has been studied. Analytical expression for a free particle kernel has been obtained in terms of the Fox H-function. A new equation for the kernel of a partical in the box has been found.
Kernel and Offspring Concepts for the Stability Robustness of Multiple Time Delayed Systems (MTDS)
Authors: Sipahi Rifat , Olgac Nejat
Published: June 2008

A novel treatment for the stability of linear time invariant (LTI) systems with rationally independent multiple time delays is presented. The independence of delays makes the problem much more challenging compared to the systems with commensurate time delays (where the delays have rational relations). It is shown that the imaginary characteristic roots can all be found along a set of curves in the domain of the delays. They are called the “kernel curves”, and it is proven that their number is small and bounded. All possible time delay combinations, which yield an imaginary characteristic root, lie on a curve so called the offspring of the kernel curves within the domain of the delays. We also claim that the root tendencies show a very interesting invariance property as a test point crosses these curves. An efficient, exact and exhaustive methodology results from these outstanding characteristics. It is unique to the new methodology that, the systems under consideration do not have to possess stable behavior for zero delays. Several example case studies are presented, which are prohibitively difficult, if not impossible to solve using any other peer methodology.
A State-Time Formulation for Multibody Systems Dynamics Simulation: Part I — Extension to Systems With General Topology
Authors: Oghbaei Mojtaba , Anderson Kurt S.
Published: June 2008

This paper presents an extension of a newly developed multibody system dynamics formulation to systems with general topology. The State-Time dynamic formulation, which has been recently developed by the authors, provides the means to yield significantly reduced simulation turnaround time through its ability to better exploit massively parallel computing resources. The rules provided in this article are useful in automating the generation of system’s equations of motion and in determining the final form of the system tangent matrix arising in this formulation. A priori knowledge of this structure assists one to find a proper ordering for the rows and columns of this matrix such that the final structure is optimized from data storage and solution expense perspectives. Also, the extended formulation enables one to eliminate the constraint forces or to bring only the desirable ones into evidence and as such results in a reduced set of equations and unknowns. Examples are provided to demonstrate application of the given rules.
Calculation of Analytic Approximations to the Periodic Solutions of a “Truly Nonlinear” Oscillator Equation
Authors: Mickens Ronald E.
Published: June 2008

We consider a “truly nonlinear oscillator” (TNLO) equation x¨ + x3 = 0 and calculate analytic approximations to its periodic solutions by the method of harmonic balance, a homotopy-type procedure, and an iteration technique. The corresponding angular frequencies and ratio of the first two Fourier coefficients are calculated and compared.
Auto-Parametric Vibration of a Cable-Stayed-Beam Structure Under Stochastic Loads
Authors: Fujino Yozo , Xia Yong
Published: June 2008

In this paper, auto-parametric vibration of a cable-stayed beam structure under stochastic excitation is studied. Linear as well as nonlinear coupling terms between the cable and beam is considered in a simplified model to capture of interaction of the cable’s local motion and the beam’s global motion. The general equivalent linearization method is applied to obtain the stochastic response. Results show that when the vertical excitation to the beam exceeds a critical value, the horizontal motions of the cable and beam are excited due to the autoparametric nonlinear coupling. The structural response possesses non-stationary characteristic, even though the load is stationary.
An Adaptive Sequential Linear Programming Algorithm for Optimal Design Problems With Probabilistic Constraints
Authors: Chan Kuei-Yuan , Skerlos Steven J. , Papalambros Panos Y.
Published: June 2008

Optimal design problems with probabilistic constraints, often referred to as Reliability-Based Design Optimization (RBDO) problems, have been the subject of extensive recent studies. Solution methods to date have focused more on improving efficiency rather than accuracy and the global convergence behavior of the solution. A new strategy utilizing an adaptive sequential linear programming (SLP) algorithm is proposed as a promising approach to balance accuracy, efficiency, and convergence. The strategy transforms the nonlinear probabilistic constraints into equivalent deterministic ones using both first order and second order approximations, and applies a filter-based SLP algorithm to reach the optimum. Simple numerical examples show promise for increased accuracy without sacrificing efficiency.
Effect of Tangential Dither Signal on Friction Induced Oscillations in the SDOF Model
Authors: Michaux Michael A. , Ferri Aldo A. , Cunefare Kenneth A.
Published: June 2008

This work examines how friction-induced oscillations are affected by high-frequency excitations, commonly referred to as dither signals. The traditional mass-on-moving-belt system is studied using two different friction models, both exhibiting a negative friction coefficient-velocity relationship. The method of averaging is implemented and compared with numerical simulations. It is shown that there is qualitative agreement between the two approaches, but there are significant quantitative differences. This study also demonstrates how tangential dither is capable of suppressing friction-induced oscillations in many cases. However, it is also shown that dither can destabilize an initially stable system in some circumstances.
Numerical Scheme for the Solution of Fractional Differential Equations of Order Greater Than 1
Authors: Kumar Pankaj , Agrawal Om P.
Published: June 2008

This paper presents a numerical scheme for the solutions of Fractional Differential Equations (FDEs) of order α, 1 < α < 2 which have been expressed in terms of Caputo Fractional Derivative (FD). In this scheme, the properties of the Caputo derivative are used to reduce an FDE into a Volterra type integral equation. The entire domain is divided into several small domains, and the distribution of the unknown function over the domain is expressed in terms of the function values and its slopes at the node points. These approximations are then substituted into the Volterra type integral equation to reduce it to algebraic equations. Since the method enforces the continuity of variables at the node points, it provides a solution that is continuous and with a slope that is also continuous over the entire domain. The method is used to solve a simple FDE using two different types of polynomials, namely cubic order and fractional order. Results obtained using both types of polynomials agree well with the analytical results. However, the fractional order polynomials give more accurate results than the cubic order polynomials do. This suggests that for the numerical solutions of FDEs fractional order polynomials may be more suitable than the integer order polynomials. A series of numerical studies suggests that the algorithm is stable.
Reliability Assessment Based on the Concept of Failure Surface Frontier
Authors: Shan Songqing , Wang G. Gary
Published: June 2008

This work proposes a novel concept of failure surface frontier (FSF), which is a hyper-surface consisting of the set of the non-dominated failure points on the limit states of a given failure region. FSF better represents the limit state functions for reliability assessment than conventional linear or quadratic approximations on the most probable point (MPP). Assumptions, definitions, and benefits of FSF are discussed first in detail. Then, a discriminative sampling based algorithm was proposed to identify FSF, from which reliability is assessed. Test results on well known problems show that reliability can be accurately estimated with high efficiency. The algorithm is also effective for problems of multiple failure regions, multiple most probable points (MPP), or failure regions of extremely small probability.
In-Situ Quantitative Analysis of Tumor Suppressor Protein (hDMP1) Using a Nanomechanical Cantilever Beam
Authors: Mallakin Ali , Inoue Kazushi , Guthold Martin
Published: June 2008

This study is focused on testing “immuno-sensors” of micro-cantilever beams for the purpose of future design of high-throughout bioassays. We currently study the aberrant expression, deletion and mutation of hDMP1 (Human DMP1) in human lung cancer. Lung cancer is the leading cause of cancer deaths among men and women in North America. There are four major histological subtypes of human lung cancer: small-cell carcinoma (SCC), adenocarcinoma (AC), squamous cell carcinoma (SCC), and large-cell carcinoma (LCC). The hDMP1 locus is localized on chromosome 7q21, a region frequently deleted as part of the 7q-minus and monosomy 7 abnormalities of acute myeloid leukemia and myelodysplastic syndrome. Recent data demonstrate the critical role of Dmp1 in Ras-Raf-Arf signaling and cellular senescence. In order to study the interactions of hDMP1 gene product and selected tumor markers with BioMEMS devices, protein coating (Antibody) conduct on cantilevers with silicon nitride (SiNx) surfaces. Silicon nitride surface has the potential to provide a good interface for BioMEMS devices, due to enhanced adherence of substances on this surface. The cantilever biosensors coated with hDMP1 antibody were used for the detection of hDMP1 antigen, which is known to be a tumor suppressor protein. Results revealed that the changes in nano-mechanical forces provided sufficient differential torque to bend the cantilever beam upon injection of the antigen. Theoretical models have been developed for the prediction of the vibrational responses of atomic force microscope (AFM) cantilevers before and after antigen/antibody interaction. Exposure of the proteins to micro-cantilever (MC) resulted in un-reversible large stress. Static deflection of micro-cantilever appeared as a result of the surface stresses that are induced by changes upon antibody-antigen interaction. This indicated that the micro-cantilever approach is useful for detecting proteins and tumor markers, and this system is applicable as a model to design miniaturized biosensor systems. We also applied gene micro-array to identify unknown targets for hDMP1 and extend our observation of the complicated process of carcinogenesis.
Stability and Contact Analysis of a Flexible Bladed-Rotor
Authors: Lesaffre Nicolas , Sinou Jean-Jacques , Thouverez Fabrice
Published: June 2008

In any high-performance turbo-machinery, instabilities and damage are commonly occurring problems. This paper presents a fully-bladed flexible rotor and outlines the associated stability analysis. Starting with the complete energies and potentials for a rotating cantilever beam in a centrifugal force field, a system of equations is derived for the rotor. This later one is made of a hollow shaft supported by a set of bearings and modelled by an Euler-Bernoulli beam connected to a rigid disk having a rotational inertia. A full set of flexible blades is also modelled by Euler-Bernoulli beams clamped in the disk. The flexural vibrations of the blades as well as those of the shaft are considered. A stability detection method, bringing coalescence and loci separation phenomena to the fore, in case of an asymmetric rotor, is made in order to determine a parametric domain where turbo-machinery cannot encounter damage. Moreover, extensive parametric studies including for instance the length and the stagger angle of the blades are presented in order to obtain robust criteria for stable and unstable areas prediction. Finally, rotor/stator contact is introduced, first with a rigid casing and then with a flexible stator. The effect of the radial load acting on the blades when rubbing against a casing is considered.
Investigations on a Base Excited Rotor
Authors: Driot N. , Lamarque C. H. , Berlioz A.
Published: June 2008

In this study, the dynamic behavior of a flexible rotor system under support excitation (imposed displacements of its base) is analyzed. The effect of an excitation on lateral displacements is investigated from an experimental and a theoretical point of view. The study focuses on the behavior in bending. An experimental set-up is developed to observe the dynamic behavior that permits to measure the lateral displacements when the support of the system is submitted to a sinusoidal rotation. A mathematical model with two gyroscopic coupled equations is then derived using Rayleigh-Ritz method. The theoretical study is based on both the multiple scale method and the normal form approach. The experimental results are favorably compared with the analytical and numerical results.
Nonlinear Dynamic Behaviour of a Motorcycle’s Forecarriage During Braking
Authors: Pezzola M. , Braghin F. , Brembilla M. , Brambilla G.
Published: June 2008

An experimental and numerical experience was carried out to investigate the nonlinear dynamic response of the forecarriage of a motorcycle, paying attention to a particular type of vibration that occurs during the braking. In fact, it was found that, in particular conditions of load on the handlebar, braking pressure, speed and temperature, the first flexural mode of the front fork is strongly excited. Thanks to the numerical model, solutions to these undesired vibrations were identified. Experimental tests were carried out modifying the design parameters of the motorcycles and of the braking system as suggested by the numerical model thus verifying that the purposed solutions were effective.
Reliability Optimization Involving Mixed Continuous-Discrete Uncertainties
Authors: Gunawan Subroto , Papalambros Panos Y.
Published: June 2008

Engineering design problems frequently involve a mix of both continuous and discrete uncertainties. However, most methods in the literature deal with either continuous or discrete uncertainties, but not both. In particular, no method has yet addressed uncertainty for categorically discrete variables or parameters. This article develops an efficient optimization method for problems involving mixed continuous-discrete uncertainties. The method reduces the number of function evaluations performed by systematically filtering the discrete factorials used for estimating reliability based on their importance. This importance is assessed using the spatial distance from the feasible boundary and the probability of the discrete components. The method is demonstrated in examples and is shown to be very efficient with only small errors.
Numerical Investigation on the Impact Strength Properties of Weldox Steel, Pure Copper, 2024-T3 Aluminum Alloy, Ti-6Al-4V Titanium Alloy and Some Composites
Authors: Venkataraman Rengaa , Elbella Abdalla , Potluri Krishna Sai
Published: June 2008

In recent times as civilian technology has grown more sophisticated, more demands are being made on the study of behavior of materials under very short duration loading. This paper describes a numerical comparison of the penetration and perforation of circular plates, struck by blunt projectile based on Johnson-Cook failure model and isotropic failure model. Explicit finite element code (ABAQUS) is used for the simulation. The better of the two failure models is used to investigate the penetration and perforation behavior of four different plate materials namely Weldox Steel, Pure Copper, 2024-T3 Aluminum alloy and Ti-6Al-4V Titanium alloy, struck by blunt and conical shaped projectiles. Nominal hardness, diameter, and mass of the projectile are kept constant in all simulations. The thickness of the plates is varied from 8mm to 40mm. The initial and residual velocities are determined from the numerical simulations. The ballistic limit velocity and the residual velocity curves are obtained for each target thickness tested. The plastic dissipation and strain energy curves are also obtained for each target thickness and plotted for different thickness-to-diameter ratios. Finally the numerical modeling of composite laminates of AS4 Carbon/Epoxy, Kevlar 149/Epoxy, AS4 Carbon/Peek and Kevlar 149/Peek are also compared for different thickness-to-diameter ratio to predict the composite laminate that has the highest impact strength.
Modeling and Vibration Analysis of Deployable Space Boom Structures
Authors: Yang Bingen , Ding Hongli , Fang Houfei , Lou Michael
Published: June 2008

Lightweight booms are being developed as a basic building element of deployable space structures for future NASA missions. This paper presents an analytical modeling and solution technique, namely the Distributed Transfer Function Method (DTFM), for synthesis and design of deployable boom structures. A space boom structure in consideration is modeled as a space frame that is enhanced by springs. In the DTFM, the distributed transfer functions describing the bending, torsion, and longitudinal deformations of frame members are first derived. A global dynamic equilibrium equation of the boom structure is assembled from the member transfer functions. Solution of the global equilibrium equation leads to free vibration solution and frequency response of the boom structure. The accuracy and efficiency of DTFM is demonstrated in a numerical example.
Affordances in Product Architecture: Linking Technical Functions and Users’ Tasks
Authors: Galvao Adriano B. , Sato Keiichi
Published: June 2008

Developing usable and desirable products requires an understanding of how users build close relationships with objects and how these relationships can be controlled by developers. This paper discusses the importance of the concept of affordances as an instrument useful for understanding the relationships between technical functions and user tasks. The approach introduces a Function-Task Design Matrix to link technical functions with user tasks and to capture relevant affordance-level requirements throughout the product architecture generation. Functional and Operational Affordance levels are introduced to help determine the product attributes necessary to optimize the ease with which users can undertake technical functions. The paper uses functional language, focusing attention towards the use of the product, rather then merely its workings. The tools for describing affordances are described first, followed by a step-by-step description of how they can be used to improve decisions during product architecture generation. The mechanism is illustrated in a case study on a kitchen appliance.
Unbalance Response Control of Rotor by Magneto-Rheological Fluid Based Squeeze Film Damper
Authors: Kim Keun-Joo , Lee Chong-Won
Published: June 2008

In this work, a magneto-rheological fluid based semi-active squeeze film damper (MR-SFD) is successfully applied to attenuate the excessive vibrations, especially unbalance responses, of a flexible rotor-bearing system. Using the linearized dynamic stiffness model of the MR-SFD, the optimal design and control algorithms that can effectively control excessive unbalance responses of flexible rotors are also proposed; the optimal damper location considering several flexible modes is systematically explored by means of the Structural Dynamics Modification technique. A simple, yet effective, control algorithm is also established in which the optimal input current levels are scheduled by using the singular value analysis. It is shown that the simulation and experimental results with a test rotor are in good agreement and that the proposed design and control algorithms of the MR-SFD are very effective in attenuation of unbalance response of the test rotor up to the second critical speed.
Modelling Sheave Elasticity in CVT Drives
Authors: Lebrecht Wolfram , Ulbrich Heinz , Pfeiffer Friedrich
Published: June 2008

This contribution presents the modelling of chain and belt CVT drives used in numerical simulations, under special consideration of the elasticity of the pulley sheaves. The system is subdivided into the pulleys, the power transmitting chain or belt and different types of contacts. Since the deformation of the CVT is of major importance for the mechanical behaviour, the elasticity of the colliding bodies has to be taken into account. Due to elasticity and clearance of the shaft-to-collar connection the pulley sheaves tilt. This effect is modelled by a force element. Furthermore as a consequence of the asymmetrical loading, the elastic sheaves deform. Therefore different approaches exist to take this into account, in which the most efficient way is the use of Castigliano’s Strain Energy Theorem. The system contains a large number of contacts. First of all there are three dimensional contacts between the pulley sheaves and the belt or chain elements. In case of belt systems there are further contacts between two adjacent elements, between elements and rings and between two adjacent rings. There exist simulation models for both types of CVTs (chain and belt drives), which are used in industrial applications.
Numerical Integration Method to Determine Periodic Solutions of Nonlinear Systems
Authors: Torii Takao , Morita Nobuyoshi , Yasuda Kimihiko
Published: June 2008

A new method to obtain periodic solution of nonlinear systems is proposed by combining secant method with numerical integration. This method can be applied to nonlinear systems with discontinuous characteristics without special treatment. To check the validity of the proposed method, we applied this method to nonlinear systems with discontinuous characteristics, such as piecewise linear spring system, system with Coulomb’s friction and impact damper system. Comparing the results by the proposed method with the results by simple numerical integration or experimental results, the validity of the proposed method is confirmed.
Analytical Formulation and Damping Analysis of Beams With Enhanced Active Constrained Layer Treatments Under Various Boundary Conditions
Authors: Gao J. X. , Liao W. H.
Published: June 2008

In this paper, an energy-based approach is developed to investigate damping characteristics of beams partially covered with enhanced self-sensing active constrained layer (ESACL) damping treatments. Analytical formulations for the active, passive, and total hybrid modal loss factors of partially covered beams with ESACL under various boundary conditions are derived. The results show that the edge elements in the ESACL can significantly improve the system damping performance as compared to the active constrained layer treatment. The effects of other key parameters and the boundary conditions have also been investigated.
Organizational Applications of Failure Knowledge Management
Authors: Terabe Masahiro , Yabuta Naohiro , Kawai Jun , Ohashi Takeo , Nakao Masayuki
Published: June 2008

In and after about the year 2000, organizations have started to build databases of workers’ accidents, troubles in the production processes, and customer complaints to make positive use of such failure information. For quantifying such organizational applications and clarifying their problems, we developed a new worksheet, “Failure Knowledge Application Evaluation Sheet (FKAES)”, and conducted a survey by having members of the Association for the Study of Failure fill out the worksheet. Our research disclosed the following facts with organizations. They properly feedback failures that require action in the production and inspection processes, however, do not identify those that require action in the planning or development processes as failures because they have organizational causes rather than technical. Large corporations with 1,000 or more employees practice more applications than smaller ones, and some even publicize their failure applications to customers and stockowners.
An Efficient Multibody Divide and Conquer Algorithm
Authors: Critchley James H.
Published: June 2008

A new and efficient form of Featherstone’s multibody Divide and Conquer Algorithm (DCA) is presented. The DCA was the first algorithm to achieve theoretically optimal logarithmic time complexity with a theoretical minimum of parallel computer resources for general problems of multibody dynamics, however the DCA is extremely inefficient in the presence of small to modest parallel computers. The new efficient DCA approach (DCAe) demonstrates that large DCA subsystems can be constructed using fast sequential techniques and realize substantial speed increases in the presence of as few as two parallel processors. Previously the DCA was a tool intended for a future generation of parallel computers, this enhanced version promises practical and competitive performance with the parallel computers of today.
Effects of Axial Load on Wave Propagation in Double-Walled Carbon Nanotubes Used as a Flexible Tip in AFM
Authors: Dalir H. , Akbari J. , Hatsuzawa T. , Farshidianfar A.
Published: June 2008

This paper is concerned with the effect of axial load, shear deformation and rotary inertia on wave propagation in double-walled carbon nanotubes (DWCNTs) within terahertz range. Our analysis is based on Timoshenko-beam model and Euler-beam model. The present models predict some terahertz critical frequencies at which the number of wave speeds changes. In these models the amounts of wave speed is unique only when the frequency is below the lowest critical frequency. When the frequency is equal to the lowest critical frequency, there can be one or two (for CNTs of smaller radii) wave speeds. Furthermore, when the frequency is higher than the lowest critical frequency, more than one wave speed exists and waves of given frequency could propagate at various speeds. It can be seen that rotary inertia and shear deformation have a significant effect on both the wave speeds and the critical frequencies. Hence, terahertz wave propagation in CNTs should be better modeled by Timoshenko-beam model, instead of Euler-beam model.
Limiting Stiffness and Damping Coefficients of Foil Bearing
Authors: Sawicki Jerzy T. , Rao T. V. V. L. N.
Published: June 2008

The limiting values of load capacity, stiffness and damping coefficients for a foil bearing are presented. The necessary conditions for high bearing numbers (journal operating at high speed) are obtained by simplifying the compressible Reynolds equation. Linearized stiffness and damping coefficients are obtained using infinitesimal perturbation method. Results of load capacity, stiffness and damping coefficients, for foil bearing are compared with those obtained for a rigid gas journal bearing. The limiting values of dynamic characteristics for a foil bearing are constant for all eccentricity ratios.
Development of a Robust Design Process Using a New Robustness Index
Authors: Hwang K. H. , Park G. J.
Published: June 2008

In product design and manufacturing, robust design leads to a product that has good quality. Robust design is reviewed in two categories: one is the process and the other is the robustness index. The process means efficient manipulation of the mean response and the variance. The robustness index indicates a measure of insensitiveness with respect to the variation. To improve existing methods, a three-step robust design (TRD) is proposed. The first step is “reduce the variance,” the second is “find multiple candidate designs,” and the third is “select the optimum robust design by using the robustness index,” Furthermore, a new robustness index is introduced in order to accommodate the characteristics of the probability of success in axiomatic design and the Taguchi’s loss function. The new robustness indices are compared with the existing ones. The developed robust design process is verified by examples and the results using the robustness index are compared with those of other indices.
Effects of Nonlinear Damping Washers on the Automatic Ball Balancer for Optical Disk Drives
Authors: Sung Cheng-Kuo , Chao Paul C. P. , Yo Ben-Cheng
Published: June 2008

This study is devoted to explore the effect of nonlinear dynamics of damping washers on the dynamic performance of automatic ball balancer (ABB) system installed in optical disc drives. The ABB is generally used on rotational system to reduce vibration. Researches have been conducted to study the performance of the ABB by investigating the nonlinear dynamics of the system; however, the model adopted often consider the damping washer in a typical ABB suspension system as a linear one, which does not reflect the fact that the practical washers are inevitably exhibit nontrivial nonlinear dynamics at some range of operation, deviating the ABB performance away from the expecteds. In this study, a complete dynamic model of the ABB including a detailed nonlinear model of the damping washers based on experimental data for practical wahers is established. The method of multiple scales is then applied to formulate a scaled model to find all possible steady-state ball positions and analyze stabilities. It is found that with reasonable level of nonlinearity, the balancing balls of the ABB are still reside at the desired positions at steady state, rendering expected vibration reduction; however, jump phenomena also occurs as the spindle operated through natural frequency of the suspension, causing unwanted system vibrations. Numerical simulations and experiments are conducted to verify the theoretical findings. The obtained results are used to predict the level of residual vibration, with which the guidelines on choices of the nonlinear damping washers are distilled to achieve desired performance.
Walking Pattern Generation for a Biped Robot Using Polynomial Approximation
Authors: Kang Yun-Seok , Yim Hong Jae , Lee Ki-Joo , Park Jung-Hun , Park Joong-Kyung , Kim Hyuk , Sung Hak-Kyung
Published: June 2008

In this paper, a stable walking pattern generation method for a biped robot is presented. A biped robot is considered as constrained multibody system by several kinematic joints. The proposed method is based on the optimized trunk motion along the moving direction. Foot motions can be designed according to the ground condition and walking speed. To minimize the deviation from the desired ZMP, the trunk motion is generated by the fifth order polynomial approximation. Walking simulation for the virtual biped robot is performed to demonstrate the effectiveness and validity of the proposed method. The method can be applied to the biped robot for stable walking pattern generation.
A Direct Approximation of Cole-Cole-Systems for Time-Domain Analysis
Authors: Haschka Markus , Krebs Volker
Published: June 2008

Cole-Cole-systems are important in electrochemistry to represent impedances of galvanic elements like fuel cells. Fractional calculus has to be applied for system analysis of Cole-Cole-systems in the time-domain. The representation of fractional differential equations of Cole-Cole-systems is addressed in this contribution. Usually, the fractional derivation is approximated, to ensure that the fractional system can be represented by conventional differential equations of an integer order. This article presents a new opposite approach, which results by direct approximation of the Cole-Cole-systems by conventional linear time invariant systems. The method considered is based on the distribution density function of relaxation times of first order Debye-processes. This distribution density is an alternative representation of the transfer behavior of such a system. Several approximation methods, based on an analysis of the distribution density, are presented in this work. The feasibility of these methods will be demonstrated by a comparison of simulated data of the approximation models to ideal data and reference values, respectively.
Modeling and Simulation of an Elastic Ship-Mounted Crane
Authors: Al-Sweiti Yousef , So¨ffker Dirk
Published: June 2008

This paper deals with development and simulation of the nonlinear model of an elastic ship-mounted crane equipped with the Maryland Rigging. The model contains three inputs to control the planar vibrations due to the planar base excitation; the luff angle is proposed to control the elastic vibration in the boom, and the length of the upper cable in conjunction with the position of its lower suspension point are proposed to control the pendulation of the payload. It is observed, through static and dynamic testing of the derived model, that moving the lower suspension point of the upper cable provides strong controllability of the horizontal displacement of the payload, while changing the length of the cable can be employed to compensate for the vertical displacement. Simulation results show that within a considerable range of pendulation displacements of the payload, the nonlinear model and the linearized one reflect nearly equivalent responses. Hence, with the property of strong controllability, the linear model can be used efficiently to design the control system, which will be discussed later in another paper.
Evaluation of Friction Control Between Wheel/Rail by Simulation and Experiment
Authors: Suda Yoshihiro , Iwasa Takashi , Fujii Takeshi , Matsumoto Kosuke , Tomeoka Masao , Nakai Takuji , Sato Yoshi , Tanimoto Masuhisa , Kishimoto Yasushi
Published: June 2008

Controlling the friction between wheel and rail is direct and very effective measures to improve the curving performances of railway trucks, because the curving performances depend much on friction characteristics. Authors have proposed a method, “friction control”, which utilizes friction modifier (specialized for wheel / rail contact) with onboard spraying system. With the method, not only friction coefficient, but also friction characteristics can be controlled as expected. In this paper, authors introduce a very interesting finding that revolution difference between leading and trailing axles depends on effectiveness of friction control which was found in the procedure of simulation. In order to certify the reality of the finding, authors carried out experiments with 1/10-scaled model vehicle. And as the result, the potential use of revolution difference between the leading and trailing as a means to evaluate effectiveness of friction control was recognized.
Bifurcations of a Planar Pendulum Driven at a Tilted Angle
Authors: Koplow Mike A. , Mann Brian P.
Published: June 2008

This paper examines the bifurcation behavior of a planar pendulum subjected to high-frequency parametric excitation along a tilted angle. Analytical and numerical results show that small deviations from either a perfectly vertical or horizontal excitation will result in symmetry breaking bifurcations. This behavior is confirmed through a series of experimental tests. Additionally, a multiple scales analysis is used to obtain an approximate solution for the free oscillations of a viscously damped planar pendulum. System identification is performed by comparing the approximate solution to transient experimental data.
Multiple Bifurcations of Synchronized Oscillators With Delays
Authors: Yuan Yuan Y.
Published: June 2008

The synchronized oscillator with two discrete time delays is considered. The local stability of the zero solution of this system is investigated by studying the distributions of the eigenvalues of the system. A complete bifurcation analysis is given by employing the center manifold theorem, normal form method and bifurcation theorem. It is shown that the trivial fixed point may lose stability via a transcritical/pitchfork bifurcation, Hopf bifurcation or Bogdanov-Takens bifurcation. Some numerical simulation examples are given for justify the theoretical results.
A Study on Numerical Solution Method for Efficient Dynamic Analysis of Constrained Multibody Systems
Authors: Lim Jae-Hwan , Yim Hong Jae , Park Jung Hun , Park Tae-Won , Kang Minseok , Jang Siyoul , Lee Yong-Kwun , Hur Deog-Jae
Published: June 2008

An efficient computational method for the constrained multibody systems is proposed. In the proposed method, local parametrization method is employed to apply the same solution method for position, velocity, and acceleration analyses since the coefficient matrices for each analysis have an identical matrix pattern. The skyline solution method is used to overcome numerical inefficiency when solving large scaled equations. Subsystem partitioning method is derived systematically to perform parallel processing for the real time simulation. To show the numerical accuracy and efficiency of the proposed method, three numerical problems are solved.
A Nonlinear Viscoelastic Model of a Hydraulic Bushing for Multi-Body Vehicle Models
Authors: Braghin Francesco , Leo Elisabetta , Sabbioni Edoardo
Published: June 2008

The present paper deals with the development and identification of a new dynamic model of an hydraulic bushing. The peculiarity and the difficulty of such a bushing is its highly nonlinear behavior. In fact, common linear rheological models are not able to realistically reproduce the relation between applied displacements and reaction forces. A nonlinear viscoelastic model presents significant difficulties in the identification of its parameters since no frequency based approach is feasible. Thus, special multi-step identification procedures have to be implemented. The adoption of such a nonlinear viscoelastic model inside a multi-body vehicle model significantly increases the computational cost of the entire vehicle model. It is therefore necessary to optimize the model not only from a reliability point of view but also from a computational cost point of view. The best compromise has therefore to be chosen.
Collaborative Conceptual Design Thinking and Software Aids: A Review
Authors: Okudan Gu¨l E. , Rao Girish
Published: June 2008

This paper reviews recent research on collaborative design thinking and software aids. The review has two foci: 1) collaborative design thinking, and 2) software aids. Recent developments regarding these foci are discussed for their contribution to collaborative design performance. The paper concludes with recommendations for future research.
A New Class of Analytical Solutions to Nonlinear Boundary Value Problems
Authors: Venkataraman P.
Published: June 2008

This paper establishes a new class of analytical solutions for nonlinear boundary value problems defined by systems of ordinary differential equations. This class uses Bezier functions derived from Bezier curves. Three engineering examples, (1) a fully developed laminar flow in a pipe with constant surface temperature; (2) a three dimensional flow over a rotating disk; (3) a three dimensional rotating flow over a stationary disk, are solved and the analytical solution is provided. These solutions are graphically indistinguishable from the exact or numerical solutions used for comparison. The solutions are obtained through standard design optimization techniques. The approach is simple. The set up is direct. No state space formulation is necessary for handling the set of differential equations. The procedure is independent of the type or the discipline the problem belongs to. The procedure is adaptive through the selection of the order of the Bezier functions.
Two-Dimensional Modeling of Multilayer Multimaterial Circuit Boards by Using an EQLAM Multilayer Model
Authors: Wang Yuqi , Low K. H. , Hoon K. H.
Published: June 2008

The materials used in the field of printed circuit boards are becoming increasingly complex as they are common to make use of numerous combination of metallic and composite plies. The potential for utilization of circuit boards is generally verified through the numerical simulation, especially for the multilayer printed circuit boards with high electronic density. This paper provides a numerical model intended to describe numerically the behavior of multilayer multimaterial circuit boards. Two parts are considered in the developed model: one is elastic-plastic damaging model that is presented to describe the metallic ply in the multilayer circuit boards; another is degenerated bi-phase model that is presented to describe composite ply. With the combination of equivalent laminate (EQLAM) method, the degenerated bi-phase successfully models the woven glass-fiber/epoxy-resin composite ply. These two plies are the basic components of multilayer circuit boards. Meanwhile, with the verification of static tests and dynamic tests, the reliability of presented model is confirmed.
Sound-Radiation Analysis for Boat Hull Based on Hammering Test and BEM
Authors: Tomatsu Taro , Otsuka Tetsuya , Okuma Masaaki , Okada Takeshi , Ikeno Tetsuro , Shiomi Kazuyuki
Published: June 2008

The accurate prediction of the sound power radiated from complicated structures, whose precise models are practically difficult to be made by the finite element method, is performed by an experimental-based approach combining impulse vibration testing and the boundary element method. This approach is applied to a small boat hull comprising of some panels with some longitudinal bending stiffeners and ribs as a basic research work in the series of a research for establishing an integrated analysis and optimization of mechanical systems to be assembled some components such as boat hulls and outer engines by means of using both experimental and theoretical modeling. It is verified that the predicted sound power level radiated from the hull is in a good agreement with an experiment. The parts of the hull radiating the noise dominantly can be identified.
Dynamic Behaviour Characterization of a Brake Disc by Means of Electronic Speckle Pattern Interferometry Measurements
Authors: Zanarini Alessandro
Published: June 2008

A complete experimental approach is here carried out to obtain the dynamic characterization of an automotive brake disc fixed on its grounded knuckle. The operative deflection shapes (ODS) were measured under harmonic excitation in the 1–23 kHz frequency range. Electronic Speckle Pattern Interferometry (ESPI) [1, 2] technology was exploited to measure high spatially defined full field displacement maps at each frequency by means of optical non-contact techniques. The harmonic excitation source was an electrodynamic shaker. The displacement maps acquired depict the dynamic behavior of the brake disc with high accuracy in the whole range, from the global bending modes at low frequency to the arising of small lobes at high frequency, with particular attention paid to the transition over resonance frequencies. Results are reported and discussed in detail.
Chaotic Motions of a Parametrically Excited Pendulum With Non-Exponentially Small Parameters
Authors: Lu Chunqing
Published: June 2008

The paper mathematically proves that a pendulum with oscillatory forcing makes chaotic motions for certain parameters. The method is more intuitive than using the Poincare’ map. It provides more information about when the chaos occurs.
Time-Varying and Non-Linear Dynamical System Identification Using the Hilbert Transform
Authors: Feldman Michael
Published: June 2008

The objective of the paper is to explain a modern Hilbert transform method for analysis and identification of mechanical non-linear vibration structures in the case of quasiperiodic signals. This special kind of periodicity arises in experimental vibration signals. The method is based on the Hilbert transform of input and output signals in a time domain to extract the instantaneous dynamic structure characteristics. The paper focuses on the dynamic analysis and identification of three groups of dynamics systems: • Forced vibrations of linear and non-linear SDOF systems excited with quasiperiodic force signal. • Combined forced vibrations of quasiperiodic time varying linear and non-linear SDOF systems excited with harmonic signal. • Combined self-excited and forced vibrations of non-linear SDOF systems excited with harmonic signal. The study focuses on signal processing techniques for nonlinear system investigation, which enable us to estimate instantaneous system dynamic parameters (natural frequencies, damping characteristics and their dependencies on a vibration amplitude and frequency) for different kinds of system excitation.
Effective Architecture for Web-Based Maintenance System and Its Security
Authors: Cheuk Alan N. , Leung Jacko T. , Tse Peter W.
Published: June 2008

Keeping machine running without failure is vital to maintain manufacturing productivity. Any loss in production and service due to equipment malfunction is unacceptable. The use of Web-based maintenance helps to detect defective machine in its early stage and thus avoid costly failure. It provides an easy way for the operator to evaluate the performance of the distant located machines. The architecture of our proposed Web-based maintenance has been redesigned to reduce the burden of the main server. The heavy loading situation which often occurs in the main server can be avoided. Beside architecture, several crypto mechanisms have been added to the system. With the aids of those crypto mechanisms, the security of the Web-based maintenance has been significantly enhanced. The data can be transferred safely and the accuracy of the results can be verified. Our Web-based maintenance is well equipped with Web-enabled and advanced fault diagnostic tools. It works more effectively and securely as compared to conventional Web-based maintenance.
Neurodynamical Control of the Heart of Healthy and Dying Crustacean Animals
Authors: Yazawa Toru , Tanaka Katsunori , Katsuyama Tomoo
Published: June 2008

We analyzed the heartbeat-interval recorded from crustacean animals, using detrended fluctuation analysis (DFA) and delayed-time embedding method. EKG was obtained from freely moving animals in normal condition and then in terminal condition; we kept recording until the life was coming to an end. Our experimental purpose was to know whether DFA and embedding methods characterize quantitatively conditions of the cardiac control network, either in the brain or in the heart, or both, the brain and heart. We concluded that DFA exponents represent whether the subjects are under sick or healthy conditions. Here we show how the controller conditions of the brain changed and how pacemaker neural network in the heart deteriorated from time to time. This report demonstrates relationship between DFA and electro-physiological of the heart.