bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Vibration Control of a Moving 3-PRR Flexible Parallel Manipulator With Multiple PZT Actuators and Sensors
Authors: Zhang Xuping , Mills James K. , Cleghorn William L.
Published: May 2009

This paper addresses the control of structural vibrations of a 3-PRR parallel manipulator with three flexible intermediate links, bonded with multiple lead zirconate titanate (PZT) actuators and sensors. Flexible intermediate links are modeled as Euler-Bernoulli beams with pinned-pinned boundary conditions. A PZT actuator controller is designed based on strain rate feed control (SRF). Control moments from PZT actuators are transformed to force vectors in modal space, and are incorporated in the dynamic model of the manipulator. The dynamic equations are developed based on the assumed mode method for the flexible parallel manipulator with multiple PZT actuator and sensor patches. Numerical simulation is performed and the results indicate that the proposed active vibration control strategy is effective. Frequency spectra analyses of structural vibrations further illustrate that deformations from structural vibration of flexible links are suppressed to a significant extent when the proposed vibration control strategy is employed, while the deflections caused by inertial and coupling forces are not reduced.
Manufacturability-Oriented Ground Beam-Joint Topology Optimization for Multi-Piece Frame Structure Design
Authors: Kim Myung-Jin , Jang Gang-Won , Kim Yoon Young
Published: May 2009

Topology optimization is a useful design tool, but it often yields layouts difficult to manufacture without considerable post structural modification. As a result, its structural performance can be significantly deteriorated. To minimize the undesirable postprocessing, we aim to develop a manufacturability-oriented compliance-minimizing topology optimization using a ground beam model incorporating additional zero-length elastic joint elements. In the present formulation, design variables control the stiffness of zero-length elastic joints, not the stiffness of beams. Because joint stiffness values at the converged state can be utilized to select candidate assembly locations, the technique is extremely useful to design multi-piece frame structures. An optimal layout is also extracted based on the stiffness values. Because structural properties of ground beams can take only on discretely available values or remain unchanged for optimization process, no post structural modification is required in an actual manufacturing step.
Process Planning by Integrated Design and Evaluation of Technology Chains Using a Standard ERP-System
Authors: Reinhart Gunther , Mueller Stefan , Lau Christian , Baron Hans-Uwe
Published: May 2009

The configuration, evaluation and selection of technology chains are some of the most critical tasks, regarding the determination of optimal product and production costs. Nonetheless, these process planning tasks are often still performed in a sequential way and are only unsatisfactorily considered within the process of product development. This paper presents a methodology to overcome these shortcomings, using an integrated configuration and evaluation of technology chains. Its implementation with a standard ERP (Enterprise Resource Planning) System is shown. Basically, the proposed methodology consists of three components. The first one is a product-technology-matrix that specifies the correlations between a company’s products and its available or projected technologies. The second component is a modular generic technology chain model that enables a classification of technologies. A combined quantitative and qualitative evaluation model to calculate and compare different technology chains completes the proposed methodology. These three elements facilitate an appropriate knowledge management concerning products, technologies and their relations. Additionally, a fast configuration of alternative technology chains and a selection of the most adequate ones for newly designed products are addressed, reducing the time of planning processes by almost one quarter. The implementation of the methodology using a standard ERP system is illustrated by two representative use cases.
Function Block Design to Enable Adaptive Job Shop Operations
Authors: Wang Lihui , Feng Hsi-Yung , Song Changjin , Jin Wei
Published: May 2009

Small volume and high product-mix contribute greatly to the complexity of job shop operations. In addition, shop floor uncertainty or fluctuation is another issue regularly challenging manufacturing companies, including job delay, urgent job insertion, fixture shortage, missing tool, and even machine breakdown. Targeting the uncertainty, we propose a function block based approach to generating adaptive process plans. Enabled by the function blocks, a so-generated process plan is responsive and tolerant to an unpredictable change. This paper presents in detail how a function block is designed and what it can do during process plan execution. It is expected that this new approach can largely enhance the dynamism of fluctuating job shop operations.
An Analysis of a Frictional Coupling Mechanism in Rolling Variators With Initial Point Contact
Authors: Lukowski S. A. , Medeksza L. A. , Kraemer D. R. B. , Momot M. E.
Published: May 2009

This paper presents an analysis of the frictional coupling mechanism in rolling variators with initial point contact. Rolling variators are continuously variable transmissions where the power is transmitted by frictional contact between nonflexible rotating elements. The essential feature of this type of transmission is that the adjoining surfaces rotate when the rolling elements roll against each other resulting in drilling-type friction due to drilling-type motion. The performance characteristics of rolling variators are thus evaluated on the basis of both the drilling-type friction and tangential forces, which transmit the power. Relationships between the characteristic parameters of frictional coupling elements are derived and expressed in the form of integrals, which can be readily evaluated numerically for the tangential force utilization coefficient, power loss coefficient, and geometric efficiency. The analysis of the frictional coupling mechanism in rolling variators constitutes a tangible contribution to the theory dealing with the design of this type of continuously variable transmissions.
A New Criterion for Prediction of Train Derailment
Authors: Durali Mohammad , Jalili Mohammad Mahdi
Published: May 2009

A new criterion for prediction of train derailment is presented in this paper. A 3 DOF wheel-set model is used to identify the main dynamic parameters that affect wheel-set derailment. Using these parameters and conventional definition of derailment coefficient, a new criterion for prediction of wheelset derailment is introduced. The proposed criterion, in addition to offering the required precision in prediction of wheel set derailment, requires measurements which are several times easier. To evaluate the capability of the new criterion in prediction of derailment, it was used to determine derailment of a full wagon model with 48 DOF moving on a rail with different random irregularities. The results were then compared with the predictions of conventional derailment coefficients.
A Laboratory Model Study of a Railway Current Collection System
Authors: Drugge Lars , Lennartsson Anders , Stensson Trigell Annika
Published: May 2009

A vital system on modern high-speed electric trains is the overhead catenary system and the pantograph current collector. As speed limits are increased, train operators and railway engineers need measures of system performance in a number of situations. In this work a laboratory model is built to study the pantograph behaviour on curved track running on a catenary system with large stiffness variation. The model is designed to be simple, yet exhibit the most characteristic dynamic properties of the real system. Another objective is the possibility to run the pantograph at speeds near the wave propagation velocity of the contact wire. The situation of several trailing pantographs, with even spacing, which excites the system to steady state, is considered. Effects of changes in design features such as tension in the contact wire and torsion and translation stiffness of components in the pantograph are studied for different speeds. The interaction is complex and the performance depends on the dynamic properties of both the catenary system and the pantograph. The results show that the pantograph configuration mainly affects the size of amplitudes in the system while the contact wire tension influences at which velocities large amplitudes and contact losses occur.
Analysis of Design for Global Manufacturing Guidelines
Authors: Kazmer David , Roser Christoph
Published: May 2009

Globalization is motivated by the potential for cost reduction through access to lower labor costs, as well as by the potential for increased sales through access to new markets. A review of cost data indicates the potential savings related to labor as compared to the potential additional costs related to raw materials, shipping, and tariffs. A logistics cost model is then presented that considers purchase cost, shipping cost, inventory holding cost, order cost, and stock out cost subject to demand uncertainty. Four different design for manufacturing and assembly (DFMA) guidelines are then analyzed for a single product case study: 1) minimize total shipping costs, 2) source components globally, 3) standardize product platforms and modularize options; and 4) regionalize final assembly. The analysis of these guidelines indicates that global sourcing of components led to the most significant cost reductions, but that all guidelines were significant when considering logistics subject to uncertain demand.
High Performance Dirichlet Parametrization Through Triangular Be´zier Surface Interpolation for Deformation of CAE Meshes
Authors: Chen Yifan , Tonshal Basavaraj
Published: May 2009

We present a method that extends the physics-based Dirichlet parametrization for applications concerning deformation of CAE meshes. Developed for a geometric surface feature framework called Direct Surface Manipulation, Dirichlet parametrization offers a number of operational flexibilities, such as its ability to use a single polynomial blending function to control deformation of a surface region subject to multiple user-specified displacement conditions. Dirichlet parametrization considers the domain of deformation as 2D steady-state conductive heat flow and solves for unique temperature distribution over the deformation domain using the finite element analysis (FEA) method. The result is used for evaluation of the polynomial blending function during surface deformation. The original Dirichlet parametrization, however, suffers from two limitations. First, because the 2D FEA mesh required for solving the steady-state heat transfer problem is obtained by directly projecting the affected 3D mesh onto a plane (deformation domain), both parameterization quality and performance depend on the structural characteristics of the projected 2D mesh (type of elements, node density, etc.) rather than geometrical characteristics of the deformation domain. Second, projecting a 3D mesh to create a 2D FEA mesh can be problematic when multiple areas of a 3D mesh are projected on the plane and overlap each other. Improvement techniques are presented in this paper. Instead of projecting the 3D mesh onto the plane to form the 2D FEA mesh, an auxiliary mesh is created based on geometric characteristics of the deformation domain, such as its size and boundary shape. Delaunay triangulation with an area constraint is applied in meshing the deformation region. The result is used as the 2D FEA mesh for solving the steady-state heat flow problem using the finite element method. Temperature of an affected node of the 3D mesh is obtained by interpolation in two steps. First, the node is projected onto the 2D FEA mesh, and the intersecting triangle is found. Second, the temperature at the intersection is obtained by interpolating the temperatures at the three vertices of the triangle using the cubic, triangular Be´zier interpolant. The result is equated to the temperature of the node. The use of an auxiliary mesh eliminated mesh-dependency for Dirichlet parametrization. The use of triangular cubic Be´zier interpolant results in better continuity condition of the interpolating surface between adjacent elements than linear interpolation. This allows us to employ a moderate size FEA mesh for computational efficiency. Implementation of the method is discussed and results are demonstrated.
Application of Tablet Computers in a Capstone Design Course
Authors: Surgenor Brian , Firth Kevin
Published: May 2009

Tablet PCs look much like regular laptop computers, except their digitized screens can be swiveled around, folded over, and written on with a stylus. Instructors have recognized that this simple write-on feature gives them the opportunity to change the way in which they lecture in a classroom. This paper examines the application of tablet PCs outside of the lecture hall. Specifically, it describes the application of tablet computers to a final year capstone design course. Particular applications include the replacement of the traditional individual design notebook with a shared electronic notebook and enhancement of sketching as a communication tool. A description of the capstone course is given to provide a context for how the tablets were used. The impact of the tablet PCs is discussed and the results of a user survey are presented.
Frictional Vibration Transmission From a Laterally Moving Surface to a Traveling Beam
Authors: Brake M. R. , Wickert J. A.
Published: May 2009

As the density of information stored in automated magnetic tape libraries continues to increase, greater requirements are placed on the precision of mechanical positioning in order to successfully read and write data bits. The location of the read/write head in the direction across the tape’s width (termed the lateral direction) is actively controlled in order to maintain alignment between the head and data tracks, even in the presence of the tape’s lateral vibration. However, during repositioning, vibration is undesirably transmitted from the laterally moving head structure to the axially-moving tape because of frictional contact between the two adjacent surfaces. As an analog of that interaction, a model is developed here to describe frictional vibration transmission from a surface having prescribed lateral motion to a tensioned beam that travels and slides over it. The beam is divided into contiguous regions corresponding to free spans and the beam’s portion that contacts the surface. A critical engagement length between the beam and the surface exists for which vibration transmission at a particular natural frequency can be substantially reduced, and for a given mode, that length depends weakly on the surface’s position along the beam’s span. By contouring the surface to have portions of differing radii of curvature, the extent of vibration transmission can be reduced over a broad range of frequency.
Using Acoustic Emission and Vibration Detection to Identify the Rotor-Stator Rubbing
Authors: Liu Zhansheng , Wang Xiaowei , Dou Wei
Published: May 2009

Vibration monitoring of rotating machines is probably the most established diagnostic method. The application of acoustic emission (AE) for rotating machine fault diagnosis is gained as a complementary tool; however, limitations in the successful application of the AE technique have been partly due to the difficulty in processing, interpreting and classifying the acquired data. The experimental investigation reported in this paper is centred on the application of the AE technique for identifying the seal rubbing on the rotor rig. An experimental test rig was designed to simulate the 200MW gas turbine rotor shafts. On the rig different degrees rubbing-impact on the seal is performed. The AE transducer and the vibration acceleration transducer are set on the bearing block. Comparisons between AE and vibration analysis over a range of speed and different degrees rubbing-impact are presented. In fact there are so many sources of AE that the successful identification of rubbing-impact signal is very important. Account for the characteristics of acoustic emission signals the wavelet transform is employed to analyze the AE signal. The wavelet transform can decompose the AE signals in time and wavelet scale domains, and catch the differences in these waves. It enables to distinguish the rubbing-impact from other sources. It is concluded that AE offers earlier fault detection and improved identification capabilities than vibration analysis, allowing the user to monitor the rubbing-impact degrees of the rotor system, unachievable with vibration analysis.
Nonlinear Dynamics of Planetary Gears Using Analytical and Finite Element Models
Authors: Parker Robert G. , Ambarisha Vijaya Kumar
Published: May 2009

Vibration induced gear noise and dynamic loads remain key concerns in many transmission applications that use planetary gears. Tooth separations at large vibrations introduce nonlinearity in geared systems. The present work examines the complex, nonlinear dynamic behavior of spur planetary gears using two models: (i) a lumped-parameter model, and (ii) a finite element model. The two-dimensional lumped-parameter model represents the gears as lumped inertias, the gear meshes as nonlinear springs with tooth contact loss and periodically varying stiffness due to changing tooth contact conditions, and the supports as linear springs. The two-dimensional finite element model is developed from a unique finite elementcontact analysis solver specialized for gear dynamics. Mesh stiffness variation excitation, corner contact, and gear tooth contact loss are all intrinsically considered in the finite element analysis. The dynamics of planetary gears show a rich spectrum of nonlinear phenomena. Nonlinear jumps, chaotic motions, and period-doubling bifurcations occur when the mesh frequency or any of its higher harmonics are near a natural frequency of the system. Responses from the dynamic analysis using analytical and finite element models are successfully compared qualitatively and quantitatively. These comparisons validate the effectiveness of the lumped-parameter model to simulate the dynamics of planetary gears. Mesh phasing rules to suppress rotational and translational vibrations in planetary gears are valid even when nonlinearity from tooth contact loss occurs. These mesh phasing conclusions, however, are not valid in the chaotic and period-doubling regions.
Structural Optimization Methods for Large Scale Problems: Status and Limitations
Authors: Fleury Claude
Published: May 2009

This paper presents results from recent numerical experiments supported by theoretical arguments which indicate where are the limits of current optimization methods when applied to problems involving a large number of design variables as well as a large number of constraints, many of them being active. This is typical of optimal sizing problems with local stress constraints especially when composite materials are employed. It is shown that in both primal and dual methods the CPU time spent in the optimizer is related to the numerical effort needed to invert a symmetric positive definite matrix of size jact, jact being the effective number of active constraints, i.e. constraints associated with positive Lagrange multipliers. This CPU time varies with jact3. When the number m of constraints increases, jact has a tendency to grow, but there is a limit. Indeed another well known theoretical property is that the number of active constraints jact should not exceed the number of free primal variables iact, i.e. the number of variables that do not reach a lower or upper bound. This number iact is itself of course smaller than the real number of design variables n. This leads to the conclusion that for problems with many active constraints the CPU time could grow as fast as n3. With respect to m the increase in CPU time remains approximately linear. Some practical applications to real life industrial problems will be briefly shown: design optimisation of an aircraft composite wing with local buckling constraints and topology optimization of an engine pylon.
Microelectronic Implementations of Fractional Order Integro-Differential Operators
Authors: Santamari´a Guillermo A. , Valverde Jose´ V. , Pe´rez-Aloe Raquel , Vinagre Blas M.
Published: May 2009

For practical applications, the fractional order integral and differential operators require to be approximated as stable, causal, minimum-phase integer order systems, which usually leads, in both continuous and discrete domains, to high order transfer functions. Assuming that an approximation of good quality is available for the fractional operator, efficient implementations, in both cost and speed, are required. The fast development of the microelectronics gives us the opportunity of using cheap, accurate, programmable and fast devices for implementing reconfigurable analog and digital circuits. Among these devices, Field Programmable Gate Arrays (FPGAs), Switched Capacitors Circuits (SCCs), and Field Programmable Analog Arrays (FPAAs) are used in this paper for the implementation of a fractional order integrator, previously approximated by the recursive Oustaloup’s method. The fundamentals of the devices, as well as the design procedures are given, and the implementations are compared considering their simulated frequency responses, the design efforts, and other important issues.
Using Spreadsheet Modules to Augment the Design of Adhesive Lap Joints
Authors: Shoup Terry E. , Drew Michael
Published: May 2009

This paper presents two easy-to-use spreadsheet modules in Microsoft Excel to assist with the design of adhesive joints. The modules make use of embedded Visual Basic numerical algorithms to give assistance with the selection of both the adhesive type and the geometric configuration of an adhesive lap joint. These modules facilitate the quick implementation of designs that are more accurate than was previously possible by traditional design methods. The method will be particularly helpful to students and inexperienced designers who first encounter the need to design adhesive joints. The paper also includes an example application to illustrate the use of the modules.
Model-Based Commutation of Brushless Permanent Magnet Motors for High-Speed Mechatronic Systems
Authors: Hosek Martin , Botev Roumen
Published: May 2009

A method for voltage commutation of a three-phase wye-connected sinusoidal brushless permanent magnet motor is presented. The method combines a model-based approach with space-vector modulation to compensate for undesirable effects of winding inductance and to maximize utilization of power source bus voltage. The proposed approach provides improved torque-speed performance and higher efficiency of the motor, which benefits are particularly significant in high-speed and cost-sensitive applications that lack current feedback capabilities. The benefits are demonstrated experimentally on a high-speed linear drive for a precision robotic system.
Robust Control of Uncertain Systems With Nonlinearities Using Model-Based Online Robustness Measure
Authors: So¨ffker Dirk , Liu Yan , Qiu Zhiping , Zhang Fan , Mu¨ller Peter C.
Published: May 2009

In this contribution, the dynamics of linear dynamical systems with nonlinearities or of nonlinear systems with structured uncertainties is controlled based on the stability analysis using the interval-analysis set-theoretic approach and combining the approach with online-optimization of the control parameters. For the online-analysis approach, a high-gain Proportional-Integral-Observer (PI-Observer) is used to estimate the model uncertainty. The estimation can be used as an online-measure of the actual model uncertainty bound which is assumed as known for the online interval analysis. Explicit expressions are given for computing the uncertain linear system stability margin in parameter space, which provides a measure of maximal parameter uncertainties preserving stability of uncertain system around known stable nominal system equilibrium. The robust PI-Observer model-based estimations are used as bounds to evaluate the system stability. The optimization of varied control gains can be used for the optimization of the introduced robustness measure, controlling uncertain nonlinear systems. The results show that the introduced new approach gives better results with respect to robustness and control performance than the classical nonlinear control method and the usual robust control method.
Localization Induced Base Isolation in Fractionally Damped Nonlinear System
Authors: Mukherjee Indrajit , Raghuprasad B. K.
Published: May 2009

In the present article we take up the study of nonlinear localization induced base isolation of a 3 degree of freedom system having cubic nonlinearities under sinusoidal base excitation. The damping forces in the system are described by functions of fractional derivative of the instantaneous displacements, typically linear and quadratic damping are considered here separately. Under the assumption of smallness of certain system parameters and nonlinear terms an approximate estimate of the response at each degree of freedom of the system is obtained by the Method of Multiple Scales approach. We then consider a similar system where the nonlinear terms and certain other parameters are no longer small. Direct numerical simulation is made use of to obtain the amplitude plot in the frequency domain for this case, which helps us to establish the efficacy of this method of base isolation for a broad class of systems. Base isolation obtained this way has no counterpart in the linear theory.
Analytical Modeling of Noise in MRI Scanners
Authors: Mechefske Chris K. , Shao Wei
Published: May 2009

Acoustic noise generated by MRI scanners is sometimes a significant problem for patients by heightening their anxiety and even causing temporary and permanent hearing impairment. This noise is caused by the Lorentz forces acting on the gradient coils of MRI scanner bound within an epoxy resin cylinder. Some acoustic analytical models were developed to describe the sound radiation characteristics of the gradient coil system. The gradient coil was modeled as a finite cylindrical duct with vibrating walls. The sound field in the duct satisfied both the boundary conditions at the wall and at the open ends. The wave reflection phenomenon at the open ends of the finite duct was described by general radiation impedance. Comparisons between the results obtained by these analytical models and calculated by a commercial (boundary element method) BEM code are presented in this paper. Both the advantages and disadvantages of both methods are discussed. The comparisons show that the results calculated by all these models reached good agreement especially at the cut-off frequencies (resonance frequencies). Corresponding experimental data have also shown a similar trend at the cut-off frequencies.
Sliding Bifurcations and Chaos in a Braking System
Authors: Zhang Wei , Yang Feng-Hong , Hu Bin
Published: May 2009

In this paper, non-smooth bifurcations and chaotic dynamics are investigated for a braking system. A three-degree -of-freedom model is considered to capture the complicated nonlinear characteristics, in particular, non-smooth bifurcations in the braking system. The stick-slip transition is analyzed for the braking system. From the results of numerical simulation, it is observed that there also exist the grazing-sliding bifurcation and stick-slip chaos in the braking system.
Landing Posture Control of a Generalized Twin-Body System Via Methods of Input-Output Linearization and Computed Torque
Authors: Yang Yi-Ling , Chao Paul C.-P. , Sung Cheng-Kuo
Published: May 2009

This study is dedicated to achieve landing posture control of a generalized twin-body system using the methods of input-output linearization and computed torque. The twin-body system is a simplified model of bipedal robot, and the success in landing posture control would prevent structural damage. To the end, the dynamic equations are built based on Newton-Euler formulation. The technique of input-output linearization is next applied to the original nonlinear equations of motion, which is followed by adopting the method of computed torque to achieve desired landing postures. While designing the controller, system singularities are circumvented by choosing controllable set of initial conditions and stable landing postures. There are two uncontrollable postures that are immovable under input torques or/and the coupling centripetal and Coriolis forces. Finally, simulation results show that the designed controller is capable of performing desired landing posture control.
Stability of SDOF Linear Viscoelastic System Under the Excitation of Narrow-Band Noise
Authors: Huang Qinghua , Xie Wei-Chau
Published: May 2009

The moment Lyapunov exponents of a single degree-of-freedom (SDOF) viscoelastic system under the excitation of a narrow-band noise, which is described as a bounded noise, is studied in this paper. An example of such a system is the transverse vibration of a viscoelastic column under the excitation of stochastic axial compressive load. The equation of motion is an integro-differential equation with parametric excitation. The method of stochastic averaging for integro-differential equations, both first-order and second-order, is applied and the eigenvalue problems governing the moment Lyapunov exponents are established. Numerical results from Monte Carlo simulation are compared with the approximate analytical results, and the variations of the moment Lyapunov exponents with the change of different parameters are discussed.
R*-Tree Localization for Polyhedral Model Based Cutter/Workpiece Engagements Calculations in Milling
Authors: Peng Xiaobo , Yip-Hoi Derek
Published: May 2009

Process modeling requires the calculation of cutter/workpiece engagement (CWE) geometry, which is especially challenging when the geometry of the workpiece is changing un-predictably. Polyhedral models have a simple geometric complexity, independent of the complexity of the workpiece shape. This paper presents a polyhedral model based CWE calculation method, which is both stable and robust as numerical calculations are avoided because of the simplicity of the model geometry. To reduce the amount of data and calculations, the proposed method works on removal volumes instead of in-process workpieces, and further adopts an R*-tree based localization technique to reduce the number of facets that are considered in a given CWE calculation. The method uses a set of connected straight-line segments to represent the real intersection curves between the removal volume and the cutter. It first calculates the intersection points between the facet edges and the cutter, removing invalid ones based on a kinematics model of the cutter then creates intersection segments between these intersection points by a proposed Mark Circle method. Finally, an undirected graph is adopted to connect all the intersection segments to form the resultant intersection lines. Implementation and examples prove that polyhedral model based CWE calculation is a correct, effective and efficient method.
Study on the Mechanical Noise Sources Identification Without Source Signal Inputs Based on Blind Signal Processing
Authors: Jiang Yong , He Lin , Zhang Lin-Ke
Published: May 2009

The mechanical noise sources identification without source signal inputs was mainly studied in this paper with the theory of blind signal processing (BSP). In traditional noise sources identification methods, the preknowledge of noise source input signals and transmission paths was required in advance. In order to overcome this shortage, a blind sources separation/deconvolution model of mechanical noise sources identification was suggested, based on the analysis of the characteristics of vibration and acoustic signals’ production, transmission and mixing. And a natural gradient method of convolutive blind separation (CBS) was carried out based on minimal mutual information (MMI). Accordingly the validity of this method was confirmed by tank experiment.
A New Composite Vibration Isolator for Gearbox Found in Large Vessels
Authors: Li Hua , Chen Zhaobo , Jiao Yinghou , Li Mingzhang , Huang Wenhu
Published: May 2009

Gearboxes are important sources of vibration and noise in large vessels. Severe vibration induced by the gearbox may cause damage and stealth failure, and wave load and explosion transmitted to the gearbox may destroy it and cut power of vessels. For this reason a new mount has been designed with special emphasis on these harmful vibrations. The mount is a hollow annular box consisted of small rib-supported boxes, which is made from composite laminates and visco-elastic materials. Every small box works like a cantilever. So, the vertical component of structural stiffness is tunable via modifying the length or section of cantilever. The directional stiffness of this mount can be changed simply by changing the fiber direction too. The ribs have relative movement because of vibrations of the mount. Then the constrained layer damping between one pair of ribs generates damping force. With the help of an additional damping device, the vibration energy can be absorbed. So, the natural frequencies and ratio of the first two modal frequencies can be changed easily. Finite element analysis has been applied to confirm its dynamic and static performance. The results prove that the proposed isolator is effective in vibration isolation for the gearbox with less additional weight or space requirement.
The “Rigid-Multi-Hertzian Method” as Applied to Conformal Contacts
Authors: Pascal J. P. , Jourdan F.
Published: May 2009

Multi-Hertzian Methods are used in Railway codes to calculate elastically normal forces of Wheel/Rail Contacts. Such methods may be properly applied to calculate forces of several elliptical simultaneous contacts. They may also be applied as a sum of Hertzian contacts to approximate normal forces of non elliptical patches such as presented in the 3D drawing. Solving such cases necessitates to choose the location, the ellipticity and the maximum indentation of elementary ellipses. In order to solve this problem it is usual to consider the maxima of the function of un-deformed profiles indentation in the symmetry plane YOZ. However these methods cannot solve cases when this function has only one maximum and has no symmetry. The “Rigid-Multi-Hertzian Method” solves these difficult cases on a topology basis: at first by searching the locations of all potential contacts in the rigid situation during a pure lateral translation (OY) of the wheel across the rail. During this translation, contact locations can be discontinuous and forbidden areas are identified as “Gutters” of which the Edges are stored. The second phase uses the indentation function to calculate indentations at gutter edges where secondary ellipses are assumed to be located; the main ellipse is located as usual. This method allows to solve conformal cases and develops smooth continuous contact forces during dynamical simulations. This paper presents the method in more details using the example of a quasi-conformal pair of profiles (S1002 and UIC60). Taking advantage of the analytical definition of these profiles, it is proposed as a benchmark to calculate the resultant normal force (amplitude and direction in upper figure) for one case of which all the surface details are disclosed: numerical data of both surfaces can be re-produced using the attached software. Contact Forces could be compared either using this method (results are given) or using numerical data as inputs to FEM calculations of commercial codes available to researchers who would like to assess the accuracy of this Rigid-Multi-Hertzian Method with respect to more sophisticated tools. One FEM calculation, using ANSYS, is presented and results are in good agreement with this method. Note: This method was first mentioned in 1991 & 1993 in papers [3], [4] but it could not be applied by third parties because implementation details were not disclosed. However it has been used since by the author to produce lookup tables of equivalent mono-patches as input data of Vocodym successful “rigid” software. It has now been developed to be used on line in the dynamical elastic software Ocrec.
Integral Design Methodology Within Industrial Collaboration
Authors: Zeiler Wim , Quanjel Emile
Published: May 2009

Sustainable building will be the major guiding principle for renewal of building and spatial planning practice. Kropman being one of the major Dutch building services contractors is aware of this trend. It is because of this rowing awareness of sustainability that the company puts effort towards knowledge transfer and research with the Dutch knowledge and research institutes. The principles of sustainable building within the IFD (Industrial Flexible Dismountable) concept are applied in the planning of a new building for the Kropman Utrecht department. Aim was an integrated approach within the design process to reach a maximum level of integration between building elements and climate conditioning elements. A newly developed methodology for structuring and documenting integral design processes enables verification and reproduction of decisions made during designing. Its conscious use by professionals results in iteration cycles within and between their own domains. The gradual emergence of a design language that helps structuring design tasks and solutions further stimulates the multidisciplinary exchange of ideas and concepts. This approach of structuring tasks and solutions is tested within a professional context of a building design project. Investigated is if the approach improves and supports the building design process. Besides its added value for building design process, the integral design methodology directly stimulates application of sustainable energy in the built environment.
Application of Generalized Predictive Control to a Fractional Order Plant
Authors: Romero Miguel , de Madrid A´ngel P. , Man˜oso Carolina , Herna´ndez Roberto
Published: May 2009

This paper deals with the use of model predictive controllers (MPC) for controlling fractional order plants. MPC is an industry standard due to its intrinsic ability to handle input and state constraints for large scale multivariable plants. The method is illustrated with Generalized Predictive Control (GPC) and two low order discrete approximations of the fractional order plant (the so-called Chebyshev-Pade´ and Rational Chebyshev approximations) as model. It is shown how stability, performance and constraints handling can be achieved with ease when dealing with fractional order plants. It is also shown how robustness can be improved by means of a prefilter.
Research on Pedestal Looseness Faults of Rotating System Based on Wavelet Analysis
Authors: Ren Zhaohui , Ma Hui , Song Naihui , Wen Feng , Wen Bang Chun
Published: May 2009

A model test rig of single-span rotor system is set up. By loosing tap bolts at one side of bearing housing to weaken elastic stiffness of supporting structure, the pedestal looseness faults existing in rotating machinery are simulated. The collected vibration signals with looseness faults at vertical direction are analyzed by the 3D waterfall spectra, wavelet scalogram and trajectory. The analytical results show that the chaotic low frequency components occur near the first critical speed and the complicated nonlinear phenomena appear, such as quasiperiodic motions and bifurcations etc. When the rotational speed exceeds double critical speed, the low frequency components tend towards stability.
Qualitative Analysis of the Affordances of Three-Dimensional Imaging Systems With a View to Conceptual Shape Design
Authors: Horva´th Imre , Opiyo Eliab Z.
Published: May 2009

This paper investigates the affordances of the stereoscopic, pseudo-volumetric and fully volumetric imaging technologies and evaluates them with regard to the requirements of spatial conceptualization of shapes. The motivation for this study comes from the hypothesis that through an integral application of various natural modalities and air-borne volumetric imaging as input and output means, respectively, an intuitive and stimulating working environment can be created for stylists and shape designers. In the investigation a set of basic imaging, interaction, computational, and ecological requirements were taken into consideration. The data on the technologies were aggregated from technological specifications, company documents and web materials, and by experimental work. The major findings are as follows: There is a serious mismatch between the functionality provided by current stereoscopic technologies and the functional expectations of interactive shape conceptualization. Pseudo-volumetric displays also fail to fulfill many functional requirements that are important for shape conceptualization. On the other hand, the fully volumetric imaging devices, in particular those based on the fast evolving interactive airborne technologies, are much more prospective. Although some of them are still in a somewhat premature stage and suffer from certain functional and performance limitations, they may be used to develop novel truly three-dimensional shape design systems and methodologies for the benefit of the users. We found holography-based technologies especially appropriate for this purpose. Nevertheless, research should further improve the functional capabilities and find solutions for a large number of operational and application issues.
Evaluation of Processing Effects on Polystyrene/Clay Nanocomposites Using an Excimer Laser
Authors: Chang I-Ta , Sancaktar Erol
Published: May 2009

Polystyrene (PS)-Organically modified montmorillonite (OMMT) nanocomposites processed by injection molding were investigated for the effects of different OMMT concentration and melt-blending conditions using a KrF excimer laser operating at 248 nm wavelength. Results indicate that PS-OMMT nanocomposites show improved resistance to excimer laser irradiation, as revealed by reduced mass loss due to laser ablation at their surfaces, when the OMMT concentration is below 2 wt%. Further increases in OMMT wt%, above the 2 wt% value, resulted in increased mass loss due to laser ablation, when compared with ablation of the neat PS material. Our experimental results also revealed that the dispersion (exfoliation) state of OMMT plays an important role in excimer laser ablation behavior of PS-OMMT nanocomposites. This result indicates the possibility for using the excimer laser as an evaluation tool in assessing the degree of exfoliation in clay reinforced polymer nanocomposites, including the assessment of spatial distribution of clay particles in injection molded nanocomposite articles, as illustrated in this work.
Simulation and Experiment Analyses on Resonance for a Rotor System With Elastic Supports
Authors: Han Qingkai , Wang Li , Yao Hongliang , Wen Bangchun
Published: May 2009

There exist different vibration patterns when a rotor system runs up and down through its critical speed, in one of them, is the interesting phenomenon called frequency capture. Based on a specially designed rotor system which is supported by elastic supports, the resonance vibrations of frequency capture and pass-through are discussed both in time and frequency domains. The nonlinear dynamical equations are described in details for the system. The vibrations of capture, when the rotating speed is locked, are compared with normal pass-through by numerical simulations and experiments. Also the instantaneous displacement trajectories, 3D FFT waterfalls and phase space portraits are calculated and demonstrated for the above two resonance vibrations. In addition, the periodical motions are discussed for capture motions using both amplitude spectra and pseudo-Poincare mappings of simulation and experiment data.
A Development Methodology for Parametric Synthesis Tools
Authors: Schotborgh Wouter O. , Ro¨ring Maarten H. L. , Grigoras Roxana , Kokkeler Frans G. M. , Tragter Hans , van Houten Fred J. A. M.
Published: May 2009

Software to support the solution generation phase of the engineering design process has been developed in academia for decades. Computational synthesis software enables generation of solutions on both conceptual and embodiment level. This paper focuses on the class of parametric design, such as documented in mechanical engineering handbooks. Examples include machine elements such as bearings, springs, fasteners, transmissions, etc. A parametric synthesis tool automates the engineering design process from functional requirements to quantified solutions, for a single machine element. Since the amount of machine elements is vast and software development time should be low, a generic methodology is helpful to speed up this process. This paper discusses such a methodology to develop synthesis tools for the class of parametric designs. It includes an analysis-oriented approach to formalize the design process’ parameters in terms of embodiment, performance and scenario. Mathematical constraint solving techniques are used to generate candidate solutions. Graphical presentation and exploration of the solution space is done with interactive plots. A standardized layout for the graphical user interface is suggested to allow uniform and intuitive use. A demonstrator is developed using the described methodology and several challenges are discussed for improved constraint solving techniques, more advanced visualization and handling problems with higher complexity. Although small in size, parametric design processes are time consuming due to their reoccurring nature. Developing synthesis tools for these designs will allow engineers to save time and improve design quality.
Optimum Synthesis of Rigid Mechanisms Using Real Coded Quantum-Inspired Evolution Algorithm (RQIEA) With Neighborhood Search
Authors: Smaili Ahmad , Hassanieh Mazen , Chaaya Bachir , Al Fares Fawzan
Published: May 2009

A modified real coded quantum-inspired evolution algorithm (MRQIEA) is herein presented for optimum synthesis of planar rigid body mechanisms (RBMs). The MRQIEA employs elements of quantum computing such as quantum bits, registers, and quantum gates, neighborhood search engine, and gradient search to form a random search algorithm for solution optimization of a wide class of problems. A brief overview of the quantum computing elements and their adaptation to the optimization algorithm is first presented. The algorithm is then adapted to the synthesis problem of RBMs. Finally, the algorithm is demonstrated and compared to other search methods by way of three examples, including two benchmark examples that have been used in the literature to assess the performance of other optimization schemes.
Analysis of Randomly Vibrating Systems Using Karhunen-Loe`ve Expansion
Authors: Bellizzi Sergio , Sampaio Rubens
Published: May 2009

The Karhunen-Loe`ve (KL) theory establishes that a second-order random field can be expanded as a series involving a sequence of deterministic orthogonal functions with orthogonal random coefficients. The KL theory can be applied to the responses of randomly excited vibrating systems with a view to performing a decomposition in separate variable (time and space) form giving a modal analysis tool. An averaging operator involving time and ensemble averages is used to draw up the KL theory. This averaging operator can be applied in stationary cases as well as non-stationary (transient) ones. The purpose of this paper is to compare the KL modes obtained from the displacement field, velocity field, and displacement-velocity field. Stationary as well as transient (non stationary) cases will be considered. The physical interpretation of the KL modes will be also investigated.