bluuebunny/crossref_metadata_2025 huggingface dataset:
An Object Oriented Approach for Robust Guided Spatial Motions
Authors: Ta¨ndl Martin , Kecskeme´thy Andre´s
Published: June 2008

The article presents an object-oriented framework for representing guided spatial motion in multibody systems. In this setting, the spatial track is regarded as a kinetostatic transmission element transmitting motion and forces as in a generic joint. For vector decompositions along the path, three different parametrizations (Frenet and Darboux frames, respectively, as well as the ODE generation proposed by Bishop) are analyzed. It is shown that for the Frenet frame parametrization, it is possible to avoid singularities at the points of inflection by a special blending technique. Track geometry is globally smoothed up to fifth order using B-Splines and Dierckx optimization routines, thus allowing for non-jerky acceleration layout. Roll-angle or banking information is additionally generated by globally smooth splines, thus also allowing for non-jerky rotations along the track. Local editing is made possible through the use of exponential blending functions. The result is a robust and easily applicable software that can be integrated in general environments. All concepts have been implemented in a multibody simulation program and tested within an industrial application of roller coaster design.
Filleting and Rounding Using a Point-Based Method
Authors: Chen Yong , Wang Hongqing , Rosen David W. , Rossignac Jarek
Published: June 2008

Rounds and fillets are important design features. We introduce a new point-based method for constant radius rounding and filleting. Based on the mathematical definitions of offsetting operations, discrete offsetting operations are introduced. Steps of our approach are discussed and analyzed. The methodology has been implemented and tested. We present the experimental results on accuracy, memory and running time for various input geometries and radius. Based on the test results, the method is very robust for all kinds of geometries.
A Comparative Study of Approaches to Dynamics Modeling of Contact Transitions in Multibody Systems
Authors: Modarres Najafabadi Seyed Ali , Ko¨vecses Jo´zsef , Angeles Jorge
Published: June 2008

This paper presents detailed discussions and a potential grouping of various approaches to the dynamic analysis of the transition phase in multibody contacts. The methods considered are able to address the general case of multiple-point contact. The main grouping principle relies on the fundamental unilateral nature of the contact between two bodies in a multibody system. Based on this, three main classes of modeling techniques are considered.
A Network Approach to Define Modularity of Product Components
Authors: Sosa Manuel E. , Agrawal Anupam , Eppinger Steven D. , Rowles Craig M.
Published: June 2008

We consider complex products as a network of components that share technical interfaces in order to function as a whole. Building upon previous work in graph theory and social network analysis, we define three measures of component modularity that consider how components may share direct interfaces with other adjacent components, how design interfaces may propagate to all other components in the product, and how components may act as “bridges” between other components. We calculate and interpret all three measures of component modularity by studying the actual product architecture of a large commercial aircraft engine. We illustrate how to use these measures to test their impact on component redesign. Directions for future work are discussed.
Integrated Design and Minimum Sensitivity Design of Controlled Multibody Systems
Authors: Carrigan Jason , Kelkar Atul , Krishnaswami Prakash
Published: June 2008

The design methods that have been traditionally used for controlled mechanical systems suffer from three major drawbacks. First, the design process is generally sequential, with the mechanical design being done first and frozen before the control system design is done. Secondly, the design is usually tuned to improve performance only without worrying about the sensitivity of the system’s performance to small variations in the system parameters. Third, there is a lack of systematic guidance for traversing the design space and arriving at a high quality design. In this work, we propose a design approach that addresses all three of these concerns. This approach first extends the constrained multi-element formulation for multibody systems to include a generic controller model. This gives the basic capability to simulate controlled multibody systems in a general way by numerically solving a set of differential-algebraic equations (DAE’s). A direct differentiation technique is then applied to the unified mathematical model to obtain a set of DAE’s in the sensitivities of the system variables. This is then used to compute the sensitivity of any performance function of interest. The system analysis and sensitivity analysis are then treated as inputs to a suitable nonlinear programming problem (NLP). The NLP serves as a vehicle to unify mechanical system and control criteria in the design process, and to incorporate sensitivity considerations along with performance considerations. The NLP also provides the means for automating the solution process through the use of optimization algorithms. Two representative example, including an industrial problem, are solved using this method. The results clearly show that the methodology is feasible and leads to a vast improvement in the quality of the final design, whatever the design considerations may be.
Recognition of Interacting Turning Features for Mill/Turn Parts
Authors: Li Shiqiao , Shah Jami J.
Published: June 2008

This paper focuses on efficient automatic recognition algorithms for turning features. As with other domains, recognition of interacting features is a difficult issue, because feature interaction removes faces and alters the topology of the existing turned features. This paper presents a method for efficiently recognizing both isolated (without interaction with other features) and interacting rotational features from geometrical CAD model of mill/turn parts. Additionally, the method recognizes Transient Turned Features (TTFs) that are defined as maximal axisymmetric material volumes from a non-turning feature that can be removed by turning. A TTS may not share any faces with the finished part. First, the rotational faces on a solid model are explored to extract isolated rotational features and some of the interacting ones. Then portions of the 3D model where no rotational faces can be used to recognize turning features are cut out and processed by a novel algorithm for finding their transient turning features.
Control Bifurcations of a Magneto-Rheological Fluid Based Active Suspension System
Authors: Shukla Amit
Published: June 2008

Design of active suspension systems is well known, however the notion of control bifurcations for the design of such systems has been introduced recently. A nonlinear active suspension system consisting of a magneto-rheological damper is analyzed in this work. It is well known that a parameterized nonlinear differential equation can have multiple equilibria as the parameter is varied. A local bifurcation of a parameterized nonlinear system typically happens because some eigenvalues of the parameterized linear approximating differential equation cross the imaginary axis and there is a change in stability of the equilibrium. The qualitative change in the equilibrium point can be characterized by investigating the projection of the flow on the center manifold. A control bifurcation of a nonlinear system typically occurs when its linear approximation loses stabilizability. In this work the control bifurcations of a magneto-rheological fluid based active suspension system is analyzed. Some parametric results are presented with suggestions on how to design nonlinear control based on the parametric control bifurcation analysis as applied to the design of an active suspension system.
On the Use of Metric-Dependent Methods in Robotics
Authors: Zlatanov Dimiter , Nenchev Dragomir N.
Published: June 2008

It is little known that the popular application of generalized inverses, singular value decomposition, conditioning numbers, and grasp and motion measures to many robotics problems involves the addition of different physical units. To redefine such techniques for proper use, meaningful screw scalar products must be used. The paper studies the use of both frame dependent positive-definite metrics and invariant, indefinite or degenerate, screw products for this purpose. Special attention is given to the diagonalization of the Jacobian matrix.
Faster Generation of Feasible Design Points
Authors: Yannou Bernard , Moreno Faysal , Thevenot Henri J. , Simpson Timothy W.
Published: June 2008

Design space exploration during conceptual design is an active research field. Most approaches generate a number of feasible design points (complying with the constraints) and apply graphical post-processing to visualize correlations between variables, the Pareto frontier or a preference structure among the design solutions. The generation of feasible design points is often a statistical (Monte Carlo) generation of potential candidates sampled within initial variable domains, followed by a verification of constraint satisfaction, which may become inefficient if the design problem is highly constrained since a majority of candidates that are generated do not belong to the (small) feasible solution space. In this paper, we propose to perform a preliminary analysis with Constraint Programming techniques that are based on interval arithmetic to dramatically prune the solution space before using statistical (Monte Carlo) methods to generate candidates in the design space. This method requires that the constraints are expressed in an analytical form. A case study involving truss design under uncertainty is presented to demonstrate that the computation time for generating a given number of feasible design points is greatly improved using the proposed method. The integration of both techniques provides a flexible mechanism to take successive design refinements into account within a dynamic process of design under uncertainty.
An Enrichment Scheme for Polynomial Chaos Expansion Applied to Random Eigenvalue Problem
Authors: Ghanem Roger , Ghosh Debraj
Published: June 2008

For a system with the parameters modeled as uncertain, polynomial approximations such as polynomial chaos expansion provide an effective way to estimate the statistical behavior of the eigenvalues and eigenvectors, provided the eigenvalues are widely spaced. For a system with a set of clustered eigenvalues, the corresponding eigenvalues and eigenvectors are very sensitive to perturbation of the system parameters. An enrichment scheme to the polynomial chaos expansion is proposed here in order to capture the behavior of such eigenvalues and eigenvectors. It is observed that for judiciously chosen enrichment functions, the enriched expansion provides better estimate of the statistical behavior of the eigenvalues and eigenvectors.
Design of a Combined Radial and Axial Magnetic Bearing
Authors: Kim Ha-Yong , Kim Seung-Jong
Published: June 2008

This paper proposes a new compact active magnetic bearing(AMB) that has both radial and axial control functions in one bearing unit, which enables the removal of the large disk unlike conventional axial AMBs. The proposed AMB consists of four U-shaped cores circumferentially connected by yokes and two-layer windings for radial and axial controls; one is configured like a homopolar AMB, and the other is the same as that of a 4-pole heteropolar AMB. Since each winding can be used for radial control, the proposed system has two kinds of operating principle according to the radial control type. As for axial control action, it uses the Lorentz force generated by the interaction of the bias flux for radial control and the axial control flux. In this paper, the proposed structure, principle, and design process based on the magnetic flux analysis are introduced, and its feasibility is experimentally verified by using a simple PD controller with a feedforward loop to compensate a coupled effect.
Integrating a Vision System With a Coordinate Measuring Machine to Automate the Datum Alignment Process
Authors: Subramanian Rajesh , de St. Germain H. James , Drake Samuel
Published: June 2008

Inspection is an important stage in the manufacturing process of machined parts. Coordinate measuring machines (CMM) have become more automatic, programmable, and capable of fulfilling the growing demands of inspection. However, fixturing (datum alignment) of parts is still done manually, consuming valuable inspection time. In this paper, we describe an automated datum alignment technique which integrates a vision system with the CMM to avoid part fixturing. The rough position of the part is estimated through image analysis. This initial reference frame drives the CMM through an automatic datum alignment procedure, thereby automatically establishing the reference frame without the use of fixtures. This technique has been demonstrated for two and a half dimensional (2.5D) machined parts with well-defined features that exhibit a stable position on a flat table.
An Integrated Model of Product, Production Process and Quality Information for Failure Prediction
Authors: Koga Tsuyoshi , Aoyama Kazuhiro
Published: June 2008

This study proposes a methodology for predicting product failures occurring due to known failures and causalities. The prediction is based on failure propagation in an integrated model of a product, production process, and quality information (PPQ). This methodology enables a designer to predict new failures. One of the concepts for failure prediction is the PPQ for compiling referring to quality-related issues. The other is an analysis methodology of the failure propagation for predicting new PPQ-based failures. The failure propagation indicates the possible failures from the production process and their causes. Three critical issues for system implementation are discussed in detail: 1) integrated PPQ model; 2) methodology for knowledge reuse by developing a PPQ-based library, and 3) an analysis methodology for failure prediction. The prototype system of the PPQ model is implemented for failure prediction in the example of a production system of Auto-Breaker.
Impact Dynamic Analysis of Elastic Multibody in an Spring Actuated System
Authors: Chung Won-Sun , Ahn Kil-Young , Park Woo-Jin , Oh Il-Sung
Published: June 2008

In this paper, the contact force between two colliding bodies is modeled by using Hertz’s force-displacement law and nonlinear damping function. In order to verify the appropriateness of the proposed contact force model, the free drop type impact test is carried out for different impact velocities and different materials of the impacting body, such as rubber, plastic and steel. The drop type impact experiment are installed to measure the velocity before impact more accurately, which verify the characteristics of contact force model. The parameters of the contact force model are estimated using the optimization technique. Finally the estimated parameters are used to predict the impact force between two colliding bodies in opening action of the spring actuated linkage system, a kind of switch mechanism for switching electric circuits.
Multigranular Molecular Dynamics Simulations of Polymer Melts Using Multibody Algorithms
Authors: Mukherjee Rudranarayan M. , Anderson Kurt S. , Ziegler John
Published: June 2008

In a multigranular approach for modeling molecular dynamics of polymer melts, different sections of the simulation box are modeled at different levels of detail viz. as particles, flexible bodies or rigid bodies. This approach eliminates high frequency localized motion while maintaining low frequency global conformational motion. This allows for longer integration time steps thus decreasing computational time. In this paper, we discuss our efforts to develop a consortium of dynamics algorithms capable of efficiently generating and solving the equations of motion at all three levels of modeling on a common software platform. A bead spring model of the polymer melt moving under the influence of truncated Lennard-Jones potential under periodic boundary conditions is pursued. Implementation issues and results from a test case consisting of 32 polymer chains of 16 beads each are presented. The paper also discusses the parallel implementation of this problem using MPI.
Interactive Scenegraph Performance Analysis, Diagnosis, and Enhancement
Authors: Kumar Shailesh , Reiners Dirk , Oliver James H.
Published: June 2008

In recent years scenegraphs have emerged as the most preferred way to represent and interact with large models in the field of computer graphics. The performance of any scenegraph application depends critically on the underlying structure of the data. Since there are many sources of 3D models and methods for constructing scenegraph data structures, poorly structured input is common. This work presents the design and implementation of an extensible performance monitoring system for a popular open source scenegraph, OpenSG. Several methods for interrogating the various factors which can affect the performance of a scenegraph are presented. A software implementation of these methods provides a tool that enables interactive exploration and diagnosis of a scenegraph to identify potential performance bottlenecks. The tool also implements some optimization techniques that can be applied to improve the structure of the scenegraph and thus the performance of the application.
A Quadrature-Based Sampling Technique for Robust Design With Computer Models
Authors: Frey Daniel D. , Reber Geoff , Lin Yiben
Published: June 2008

Several methods have been proposed for estimating transmitted variance to enable robust parameter design using computer models. This paper presents an alternative technique based on Gaussian quadrature which requires only 2n+1 or 4n+1 samples (depending on the accuracy desired) where n is the number of randomly varying inputs. The quadrature-based technique is assessed using a hierarchical probability model. The 4n+1 quadrature-based technique can estimate transmitted standard deviation within 5% in over 95% of systems which is much better than the accuracy of Hammersley Sequence Sampling, Latin Hypercube Sampling, and the Quadrature Factorial Method under similar resource constraints. If the most accurate existing method, Hammersley Sequence Sampling, is afforded ten times the number of samples, it provides approximately the same degree of accuracy as the quadrature-based method. Two case studies on robust design confirmed the main conclusions and also suggest the quadrature-based method becomes more accurate as robustness improvements are made.
Probabilistic Analysis of Notched Micro Specimen Under Three-Point Loading
Authors: Ekwaro-Osire S. , Khandaker M. P. H. , Gautam K.
Published: June 2008

Stress singularity arises in MEMS devices due to sudden geometric and material variation. Sharp notches are common example of sudden geometric variation, which often occurs during the fabrication process of MEMS components. The magnitude of the stress field induced due to stress singularity is given by the value of the notch stress intensity, K. The stress intensity is depended on the notch geometry and the type of loading (mode I, mode II and mode III). Fracture failure at the notch occurs when notch stress intensity reach fracture toughness, KC. An electrostatically actuated test device used for the analysis of a notched micro beam specimen under three-point loading will be presented. The objective of this study was to investigate the effect of geometric configuration on the stress field around singularity for a micro beam specimen by asymptotic, numerical and probabilistic analysis. The scope of work is fourfold. First, the effect of notch angle on the strength of the singularity is determined using two different asymptotic analysis methods — complex potential method and Airy stress function method. Second, the effect of the angular variation (for different notch angle) on the influence coefficients is determined using analytical methods. Third, the effect of the notch angle and depth on the stress intensity factor is determined using finite element methods and contour integral method. Fourth, the probabilistic analysis of maximum stress developed in the micro beam specimen is performed.
Adaptive Least-Mean Square Feed-Forward Control With Actuator Saturation by Direct Minimization
Authors: Zuo Lei , Nayfeh Samir A.
Published: June 2008

The least-mean squares (LMS) adaptive feedforward algorithm is used widely for vibration and noise cancellation. If reference signals become large enough to saturate that actuators, the filter coefficients in such algorithms can diverge. The leaky LMS method limits the controller effort by augmenting the objective function by a weighted control effort, and is known to attain good performance and avoid growth of filter coefficients for well-chosen weights. We propose an algorithm that seeks to directly minimize the mean-square cost in the presence of saturation. We derive the true stochastic gradient of the cost for systems with saturation with respect to the filter coefficients and obtain an adaptation rule very close to that of the filtered-x algorithm, but in the proposed algorithm, the reference filter is a time-varying modification of the secondary channel. In simulations of an active vibration isolation system with actuator limits subject to random ground vibration, the leaky LMS algorithm attains its best performance with actuation weights small enough to allow significant actuator saturation but large enough to prevent divergence. The proposed algorithm attains performance better that attained by the leaky LMS algorithm, and does not require the selection of weights.
Polygon Offsetting by Computing Winding Numbers
Authors: Chen Xiaorui , McMains Sara
Published: June 2008

In this paper we present a simple new algorithm to offset multiple, non-overlapping polygons with arbitrary holes that makes use of winding numbers. Our algorithm constructs an intermediate “raw offset curve” as input to the tessellator routines in the OpenGL Utility library (GLU), which calculates the winding number for each connected region. By construction, the invalid loops of our raw offset curve bound areas with non-positive winding numbers and thus can be removed by using the positive winding rule implemented in the GLU tessellator. The proposed algorithm takes O((n + k)logn) time and O(n + k) space, where n is the number of vertices in the input polygon and k is the number of self-intersections in the raw offset curve. The implementation is extremely simple and reliably produces correct and logically consistent results.
Making Transitions From 2-D Design to 3-D Design and Preparing to Bring the Product Lifecycle Management Into the Classroom
Authors: Zhang Andy S. J.
Published: June 2008

This paper addresses some issues that many mechanical engineering departments are facing or soon will be facing in response to the rapid development in the area of MCAD as the industry is making transition from 2-D to 3-D and embracing the concept of Product Lifecycle Management (PLM). Something we took for granted before now becomes an issue. For example, as the 3-D based CAD package becomes more and more powerful and much easier to use than its 2-D counterpart, do we still need to teach engineering graphics using 2-D CAD packages or should we use the 3-D CAD package for the same purpose? The next question then would be which package is better and easier for the students to use to learn the basics of geometric construction and orthographic projection theory. This paper tries to discuss these issues and provide some input on the importance of the issues. As the parametric 3-dimensional MCAD package becomes more affordable and evolves into a mature lifecycle product management package, more curriculum changes would have to follow to meet the demands of the industry.
Primary Research of Safety Valve Online Testing Technology
Authors: Guo Chongzhi , Wang Youhong
Published: June 2008

A simplified safety valve simulation model is established on basis of a widely used safety valve in engineering-spring directly loading safety valve, and the relationship between the mechanic parameter of spring surface and loading is discussed according to the result of simulation analysis. The relationship of strain varying rate in spring measuring point and setting pressure varying rate of safety valve is achieved, it can be used as a online fault diagnosis criteria when setting pressure changes in working course. Furthermore, an online testing technology of safety valve is proposed. Through experiment research using traditional electric strain sensor, the relationship between measured parameters of the specific parts in the safety-valve and the experimental loading is achieved, and the online testing method is proved to be very workable.
Adapting Non-Uniform Rational B-Spline Fitting Approaches to Metamodeling
Authors: Turner Cameron J. , Crawford Richard H.
Published: June 2008

Modern engineering design requires the exploration of complex nonlinear design spaces that relate large numbers of design variables and performance criteria. Effective exploration and decision making requires the availability of efficient representations of high dimensional design spaces. Techniques from the field of metamodeling, which builds models of models, are often used to represent complex design relationships. We have developed an alternative, spline-based metamodeling technique that is amenable to adaptive representation of high dimensional spaces and facilitates optimization-based exploration of such spaces. This paper describes our technique for fitting Non-Uniform Rational B-splines (NURBs) to points in a design space generated from simulations or experiments. The algorithm is illustrated with examples from metamodeling and nonlinear optimization literature. The results indicate that our method achieves an average global correlation of more than 99% and an average maximum local RMS error of less than 3% of full scale.
Double-Hopf Bifurcation in an Oscillator With External Forcing and Time-Delayed Feedback Control
Authors: Chen Zhen , Yu Pei
Published: June 2008

In this paper an oscillator with time delayed velocity feedback controls is studied in detail. The particular attention is focused on internal double-Hopf bifurcation with an external exciting force. Linear analysis is used to find the critical conditions under which a double-Hopf bifurcation occurs. Then center manifold theory is applied to obtain an ODE system described on a four-dimensional center manifold. Further, the technique of multiple-time scales is employed to find the approximate solutions of periodic and quasi-periodic motions. Finally, numerical simulation results are presented to verify the analytical predictions. Also, for some certain parameter values, numerical results show chaotic attractors.
Process Platform-Based Production Configuration
Authors: Zhang Lianfeng , Jiao Jianxin , Pokharel Shaligram
Published: June 2008

In nowadays’ changing manufacturing environment, designing product families based on product platforms has been well accepted as an effective means to fulfill product customization. The current production practice and academic research of platform based product development mostly focus on the design domain, whereas limited attention is paid to how production can take advantage of product families for realizing economy of scale through enormous repetitions. This paper puts forward a concept of process platforms, based on which an efficient and cost saving production configuration for new members of a product family can be achieved. A process platform implies three aspects, including generic representation, generic structures and generic planning. The issues and rationale of production configuration based on a process platform are presented. A multilevel system of nested colored object-oriented Petri Nets with changeable structures is proposed to model the configuration of production processes. To construct a process platform from existing process data, a data mining approach based on text mining and tree matching is introduced to identify the generic process structure of a process family. An industrial example of high variety production of vibration motors for hand phones is also reported.
Enhancement of Turning Process Using Vibration Signature Analysis
Authors: Batey Marlon C. , Hamidzadeh Hamid R.
Published: June 2008

Analytical and experimental vibration analyses are conducted for a lathe system to detect the possibility of faults and develop an accurate cutting process. The data acquisition system utilized for this purpose processes the analog input from the manufacturing system and displays the response in both the real time and frequency domains. The vibration signatures for different arrangements are recorded to determine the dynamic characteristics of the system which includes work pieces, tool, and lathe components. These vibration signatures were analyzed to determine cause of inaccuracy in the manufacturing process and the faulty components. In this study, two major problem causing sources were identified using vibration analysis for the system under different operating conditions. In addition to the identified problems, the phenomena of cutting tool chatter with various intensities was examined and recorded during testing. In this study the best possible operating conditions for a specific turning process were determined using vibration analysis. Problem causing components for several case studies (different speeds, feed rates, and tool lengths) were identified and guidelines for improving a typical manufacturing process were recommended.
OWL-Based Hybrid Product Knowledge Model for Collaborative Engineering Environment
Authors: Lee Jae-Hyun , Suh Hyo-Won
Published: June 2008

This paper introduces an approach to OWL-based hybrid product knowledge model for collaborative engineering environment. The participants in collaborative engineering want to share and reason product knowledge through internet without any heterogeneity and ambiguity. In this paper, the hybrid product knowledge model is proposed using first-order logic(FOL), relational database(RDB) and web ontology language(OWL) according to a formal ontology. Our knowledge model can be used to develop an integrated knowledge-base which reduces heterogeneity and ambiguity. Firstly, the collaborative engineering domain is analyzed and then the product knowledge is organized into four levels such as product context model, product specific model, product design model and product manufacturing model. Secondly, the four levels are represented by FOL in layered fashion. The concepts and the instances of a formal ontology are used for recursive representation of the four levels. The instances of the concepts of an upper level like product context model are considered as the concepts of an adjacent lower level like product specific model, and this mechanism is applied to the other levels. Thirdly, these logic representations are integrated with the schema and the instances of a relational database. Finally, OWL-based product knowledge model is developed, in which OWL representation of the four levels are defined through the integration of the logic representation and OWL primitives. Thus, a hybrid product knowledge model is constructed, in which the four product knowledge models have their major representation such as FOL, RDB, or OWL according to the characteristics of each model. This approach enables engineer to share product knowledge through internet reducing ambiguity, and utilize it as basis for additional reasoning.
Sensivity Analysis of Flexible Multibody Systems
Authors: Neto M. A. , Leal R. P. , Ambro´sio J.
Published: June 2008

In this work a general formulation for the computation of the first order analytical sensitivities based on the direct method is presented. The direct method for sensitivity calculation is obtained by differentiating the equations that define the response of the flexible system with respect to the design variables. The design variables used here are the ply orientations of the laminated. The analytical sensitivities are compared with the numerical results obtained by using the finite differences method. For the beam composite material elements, the section properties and their sensitivities are found using an asymptotic procedure that involves a two-dimensional finite element analysis of their cross-section. The equations of the sensitivities are obtained by automatic differentiation and integrated in time simultaneously with the equations of motion of the multibody systems. The equations of motion and sensitivities of the flexible multibody system are solved and the accelerations and velocities and sensitivities of accelerations and velocities are integrated. Through the application of the methodology to a single flexible multibody systems the difficulties and benefices of the procedure are discussed.
Development Process of Clatter and Rattle Noise Free (CARF-) Transmissions
Authors: Bertsche Bernd , Novak Wolfgang , Stockmeier Moritz , Dog˘an Su¨reyya Nejat , Ryborz Joachim
Published: June 2008

Clatter and rattle noise is an increasing challenge for the development of low-noise transmissions. Efforts to reduce fuel consumption and exhaust emissions of combustion engines combined with a decrease of the idle speed cause increasing cyclic irregularities within modern drivelines which result in an increasing clatter and rattle noise. Numerous external and internal measures for the reduction of clatter and rattle noise propensity have been developed; however only a few were applied to series products. This paper publishes potential measures for this noise reduction. New grounds were broken in the field of clatter and rattle noise free automotive transmissions by decoupling all gears which are not in the power flow. On the basis of a patented solution (CARF-Transmission) the clatter and rattle noise free transmission is presented as well as derived developments.
Nonlinear Control of Hybrid Electrostrictive/Piezoelectric Polymeric Structures: Theory and Experiment
Authors: Chai W. K. , Tzou H. S.
Published: June 2008

Electromechanical response of electrostrictive materials behaves quadratically, while that of piezoelectric material behaves linearly. This study is to evaluate quadratic control response of electrostrictive actuators with reference to linear signal generation of piezoelectric sensors. A hybrid beam structure coupled with an electrostrictive RTV 270 actuator layer and a polyvinylidene-fluoride sensor layer is fabricated and its control response evaluated. Mathematical model is established first, followed by finite-difference discretization resulting in a set of finite difference equations used in numerical simulation of controlled and uncontrolled responses. The physical model connected to a bang-bang controller, a high-voltage amplifier, a data acquisition system is setup in laboratory. Due to the quadratic behavior of the electrostrictive actuator, the bang-bang controller activates the electrostrictive actuator only in the upward motion of the beam, according to the signals generated from the piezoelectric sensor. Vibration control characteristic (i.e., damping ratio estimation) of the beam subjected to various control conditions are evaluated. Experimental data are compared favorably with simulation results.
CVODES: The Sensitivity-Enabled ODE Solver in SUNDIALS
Authors: Serban Radu , Hindmarsh Alan C.
Published: June 2008

CVODES, which is part of the SUNDIALS software suite, is a stiff and nonstiff ordinary differential equation initial value problem solver with sensitivity analysis capabilities. CVODES is written in a data-independent manner, with a highly modular structure to allow incorporation of different preconditioning and/or linear solver methods. It shares with the other SUNDIALS solvers several common modules, most notably the generic kernel of vector operations and a set of generic linear solvers and preconditioners. CVODES solves the IVP by one of two methods — backward differentiation formula or Adams-Moulton — both implemented in a variable-step, variable-order form. The forward sensitivity module in CVODES implements the simultaneous corrector method, as well as two flavors of staggered corrector methods. Its adjoint sensitivity module provides a combination of checkpointing and cubic Hermite interpolation for the efficient generation of the forward solution during the adjoint system integration. We describe the current capabilities of CVODES, its design principles, and its user interface, and provide an example problem to illustrate the performance of CVODES.
The Measurement of the Dynamic Properties for an Elastic Half-Space Medium
Authors: Hamidzadeh H. R. , Dehghani M.
Published: June 2008

Reliable dynamic analysis of soil-foundation interaction requires knowledge of dynamic properties of shear modulus, Poisson’s ratio and the geometrical damping ratio of the medium. In the case of a machine foundation resting on the surface of ground it is common to assume a rigid base for the foundation and an elastic half-space model for the ground. To properly evaluate dynamic properties of medium a technique based on resonant testing in conjunction with analytical solution is adopted. In the experimental part of the analysis vertical frequency responses of different rigid square blocks individually resting on the medium are measured. These results are correlated with frequency responses computed using an established analytical solution. Analyzing this equitability of results can provide estimated values for dynamic properties of the medium. The validity of the proposed method is verified by performing experiments on laboratory model.
Wave Field in Fluid Saturated Porous Media Subjected to Excitations of Multiple Energy Sources
Authors: Dai Liming , Wang Guoqing
Published: June 2008

This research is to investigate the behavior of elastic waves in porous media consisting of fluid and solid. A new methodology for describing the wave motion of a fluid-saturated porous medium is developed with the establishment of a mathematical wave model. Dynamic equations in the form of displacements of the fluid and solid are derived for analyzing the elastic waves propagating in homogeneous and isotropic porous media, which are subjected to excitations of multiple energy sources. Solutions of the wave equation are developed on the basis of the moving-coordinate method. Numerical simulations of the waves propagating in the porous media with multiple energy sources are also performed for demonstrating the application of the mathematical model developed.
Direct and Indirect Vibro-Acoustic Measurements for Road Noise NVH Predictions
Authors: Zanarini Alessandro , De Coninck Filip , Mendrok Krzysztof , Sas Paul
Published: June 2008

This paper describes vibro-acoustic direct and indirect measurements for road noise NVH predictions from a complete car. Attention is devoted to the dynamic response of the structure and interior pressure field toward tire patch displacement inputs. The direct measurements exploited the Team Corporation CUBE™ high frequency 6 degree-of-freedom (DOF) shaker recently installed at the KULeuven Vehicle Technologies Laboratory; the input was provided directly at the tire contact patch, while the responses were measured as accelerations and pressures on the structure. In the indirect measurements a low-mid frequency volume velocity source (LMFVVS) was used to acoustically excite the structure in the reverse path direction from the inside of the interior car cavity, while accelerations on the car and forces/torques where acquired by a 6-DOF dynamometer at the tire patch. From both types of excitations Frequency Response Functions (FRF) were calculated in the frequency range [0–500 Hz]. The non-linearity of the full car system was investigated with different direct and indirect measurement tests, in order to assess the feasibility of the reciprocity principle in such a complex structure. Measurement set-ups, results and comparisons are described and discussed in detail.
Some Applications of Automatic Differentiation to Rigid, Flexible, and Constrained Multibody Dynamics
Authors: Griffith D. Todd , Turner James D. , Junkins John L.
Published: June 2008

In this paper, we discuss several applications of automatic differentiation to multibody dynamics. The scope of this paper covers the rigid, flexible, and constrained dynamical systems. Particular emphasis is placed on the development of methods for automating the generation of equations of motion and the simulation of response using automatic differentiation. We also present a new approach for generating exact dynamical representations of flexible multibody systems in a numerical sense using automatic differentiation. Numerical results will be presented to detail the efficiency of the proposed methods.
On the Calculation of Radiation Force on Spheres Due to Arbitrary Spatially Distributed Acoustic Beams
Authors: Silva Glauber T. , Fatemi Mostafa
Published: June 2008

This work presents a theory for the acoustic radiation force exerted on a solid sphere by an arbitrary spatially distributed beam. The theory is developed for an sphere suspended in an ideal fluid. We assume that the acoustic beam can be decomposed in a set of plane waves with same frequency, propagating in different directions. The sphere radius is considered to be much smaller than the wavelength of the beam. Bulk properties of the sphere such as shear and compressional sound speed are taken into account. The radiation force is obtained by solving the linear acoustic scattering problem for the sphere. Theoretically, the radiation force depends on the sphere cross section area, the radiation force function, and the vector energy flux upon the sphere. The radiation force function is related to the sphere scattering properties. We apply the developed theory to study the radiation force produced by an spherical concave transducer. The generated radiation force can be decomposed into two components, namely, axial and transverse with respect to the wave propagation direction. The ratio between the transverse and axial components of the force depends on the transducer F-number and wave frequency. Results show that this ratio for a 2 MHz transducer with 3.5 F-number on the focal plane is less than 5%.
Expressions With Fuzzy Information in EXPRESS/STEP
Authors: Ma Z. M.
Published: June 2008

Information with imprecision and uncertainty is inherently presented in engineering design and manufacturing. The nature of imprecision and uncertainty is incompleteness. Product data model, being a core of intelligent manufacturing system, consists of all concerned data in the product life cycle. It is possible that crisp data as well as imperfect data are involved in product data model. So EXPRESS, being a powerful tool to develop a product data model, should be extended for this purpose. This paper extends the expressions in EXPRESS to make it possible to model fuzzy engineering information.
Nonlinear Features in the Dynamic Response of a Cracked Beam Under Harmonic Forcing
Authors: Andreaus Ugo , Casini Paolo , Vestroni Fabrizio
Published: June 2008

Detection of damage in beam structures is usually pursued by means of methods based on the measured variations of modal quantities, like frequencies and eigenmodes. The drawback of these methods is the small sensitivity of modal quantities to concentrated damage. Since a crack introduces nonlinearities in the system, the use of nonlinear techniques of damage detection merits to be investigated. With this aim the present paper is devoted to analyze the peculiar features of the nonlinear response of a cracked beam. The problem of a cantilever beam with an asymmetric edge crack subjected to a harmonic forcing at the tip is considered as a plane problem and is solved by using two-dimensional finite element model; the behaviour of the breathing crack is simulated as a frictionless contact problem. The modification of the response with respect to the linear one is outlined: in particular, excitation of sub- and super-harmonics, period doubling, quasi-impulsive behaviour at crack interfaces are the main achievements. These response characteristics can be used in nonlinear techniques of damage identification.
Investigating the Effects of Porous Material Compression on the Acoustical Behavior of Absorption and Barrier Materials
Authors: Ohadi A. R. , Moghaddami M.
Published: June 2008

The paper discusses the effects of compression on acoustical performance of porous materials. A finite element model is used to predict the absorption coefficient and transmission loss of absorbing and barrier materials. This model is developed based on the Galerkin method and includes the equation of wave propagation in rigid frame porous material. The compression of porous material is entered to the model with relations that explain modifications of physical properties used in wave equation. Acoustical behavior of absorption and barrier materials with and without compression is studied. It is shown in this paper that compression of the material leads to improvement of the transmission loss of the barrier materials, whereas absorption coefficient reduction has been obtained for absorbing materials.
Simulation of Engine Vibration on Nonlinear Hydraulic Engine Mounts
Authors: Ohadi A. R. , Maghsoodi G.
Published: June 2008

In this paper, vibration behavior of engine on nonlinear hydraulic engine mount including inertia track and decoupler is studied. In this regard, after introducing the nonlinear factors of this mount (i.e. inertia and decoupler resistances in turbulent region), the vibration governing equations of engine on one hydraulic engine mount are solved and the effect of nonlinearity is investigated. In order to have a comparison between rubber and hydraulic engine mounts, a 6 degree of freedom four cylinders V-shaped engine under inertia and balancing masses forces and torques is considered. By solving the time domain nonlinear equations of motion of engine on three inclined mounts, translational and rotational motions of engines body are obtained for different engine speeds. Transmitted base forces are also determined for both types of engine mount. Comparison of rubber and hydraulic mounts indicates the efficiency of hydraulic one in low frequency region.
Non-Linear Systems Under Parametric Alpha-Stable Le´vy White Noises
Authors: Di Paola Mario , Pirrotta Antonina , Zingales Massimiliano
Published: June 2008

In this study stochastic analysis of nonlinear dynamical systems under a-stable, multiplicative white noise has been performed. Analysis has been conducted by means of the Itoˆ rule extended to the case of α-stable noises. In this context the order of increments of Levy process has been evaluated and differential equations ruling the evolutions of statistical moments of either parametrically and external dynamical systems have been obtained. The extended Itoˆ rule has also been used to yield the differential equation ruling the evolution of the characteristic function for parametrically excited dynamical systems. The Fourier transform of the characteristic function, namely the probability density function is ruled by the extended Einstein-Smoluchowsky differential equation to case of parametrically excited dynamical systems. Some numerical applications have been reported to assess the reliability of the proposed formulation.