bluuebunny/crossref_metadata_2025 huggingface dataset:
Intrinsic Formulation of Dynamics of Curvilinear Systems
Authors: Lerbet Jean
Published: June 2008

The paper concerns the dynamics of curvilinear systems which are often met in mechanical systems (robots, artificial satellites and so on). We only suppose that each section is rigid. Using Lie group theory, a general curvilinear system is then equivalent to a differentiable distribution of displacements, elements of the Lie group of Euclidean displacements the algebra of which may be identified with the Lie algebra of screws. The kinematics is described by the lagrangian field of deformations and the lagrangian field of velocities elements of the Lie algebra and with standard hypotheses about the distribution of external forces, the intrinsic equations are obtained, the displacements or deformations being small or large. The non linearities (of inertia terms as for internal strenghts) appear by the adjoint mapping and its derivation: the Lie braket. Last, the elements to automatically obtain scalar equations and to come back to more classical models (beam, cable,) are given.
Comparative Performance Study of Jatropha Methyl Ester as Diesel Oil Substitute on DI Diesel Engine With Emphasis on Vibration and Noise as Potential Engine Parameters
Authors: Ravi Kiran Sastry G. , Niranjan Kumar I. N. , Prasad Chandra , Rao B. V. A.
Published: June 2008

Among the biomass resources, vegetable oils are observed to be good alternative fuels for use in diesel engines and are also attractive because of renewability. However, there are fundamental problems of engine performance and exhaust emissions due to high viscosity and low volatility of the pure vegetable oil. The present work aims at evaluating the performance of Jatropha methyl ester (JME) by evaluating the combustion properties and engine vibration & noise. This generates a corroborative method to ascertain the engine combustion quality, as the vibration trend developed by the engine is synonymous with the excitation generated by combustion..
Novel Method for Rigid and Flexible Multibody System Dynamics Simulation
Authors: Zahariev Evtim V.
Published: June 2008

In the paper novel generalized Newton–Euler equations are derived and applied for simulation of dynamics of rigid and flexible multibody systems. The procedures for working out the equations are described. The dynamic equations are expressed with respect to the quasi–velocities and accelerations. The equations proposed are applicable for flexible structures for which the mass reduction is implemented theoretically correctly on the basis of the equivalence of the kinetic energy. The equations are consistent with the commercially available software that realizes the finite element methods for deriving the dynamic equations of systems with mesh of rigid bodies, flexible elements and substructures. Several examples present the effectiveness of the method. It is shown that using the classical finite element mass-matrices and the method proposed for deriving the dynamic equations one could obtain precise results. Examples of deformations of long tethered satellite are presented.
Dynamic Analysis of MEMS Resonators Under Primary-Resonance Excitation
Authors: Nayfeh Ali H. , Younis Mohammad I. , Abdel-Rahman Eihab M.
Published: June 2008

We present a dynamic analysis and simulation of electrically actuated microelectromechanical systems (MEMS) resonators under primary-resonance excitation. We use a shooting technique, perturbation techniques, and long-time integration of the equation of motion to investigate the global dynamics of the resonators. We study the dynamic pull-in instability and show various scenarios and mechanisms for its occurrence. Our results show that dynamic pull-in can occur through a saddle-node bifurcation, a period-doubling bifurcation, or homoclinic tangling, depending on factors such as the initial conditions of the device and the level of the electrostatic force.
Finite Element Analysis for Interior Booming Noise Reduction in a Tractor Cabin
Authors: Cao Ji , Dai Liming
Published: June 2008

This paper presents a finite element approach to analyze the “boom” noise for a compact tractor cabin. The tractor cabin is initially designed to have a structure made up of steel beams and aluminum panels, as well as PMAA panels in windshield, backlight and windows. Cavity acoustic modes of the cab are evaluated and the acoustic resonant frequencies are identified. The study on the structural-borne noise from the cabin structural vibration generated by the engine of the vehicle is performed. A coupled-field finite element model, counting the interactions between the air fluid inside the cabin compartment and the cabin exterior structure, is presented for investigating the structural-borne noise in a low frequency range of 20 Hz to 80 Hz. This range has shown strong boom effects. The interior noise level at driver’s right ear position is investigated. The peak noise levels at the position are determined. The effects of additional stiffeners and damping layers on the boom noise are also investigated.
Identification of Structural Stiffness and Damping Coefficients of a Shoed Brush Seal
Authors: Delgado Adolfo , San Andre´s Luis
Published: June 2008

The multiple-shoe brush seal, a variation of a standard brush seal, accommodates arcuate pads at the bristles free ends. This novel design allows reverse shaft rotation operation, and reduces and even eliminates bristle wear, since the pads lift off due to the generation of a hydrodynamic film during rotor spinning. This type of seal, able to work at both cold and high temperatures, not only restricts secondary leakage but also acts as an effective vibration damper. The dynamic operation of the shoed-brush seals, along with the validation of reliable predictive tools, relies on the appropriate estimation of the seal structural stiffness and energy dissipation features. Single frequency external load tests conducted on a controlled motion test rig and without shaft rotation allow the identification of the structural stiffness and equivalent damping of a 20-pad brush seal, 153 mm in diameter. The seal energy dissipation mechanism, represented by a structural loss factor and a dry friction coefficient, characterizes the energy dissipated by the bristles and the dry friction interaction of the brush seal bristles rubbing against each other. The physical model used reproduces well the measured system motions, even for frequencies well above the identification range.
A Design Approach of a Fuselage Barrel in Grid Structure
Authors: Gatta Giuseppe , Romano Fulvio
Published: June 2008

In this paper a design method of a cylindrical fuselage barrel in grid structure to fabricate in composite material is illustrated. The approach can be divided in two phases. In the first step, a lattice structure, that is a grid structure with ribs only and without a skin, is sized thanks to an analytical approach. The independent variables to optimize are five: number of helical ribs, number of circumferential ribs, rib height, circumferential rib thickness, helical rib thickness. Some geometric constraints on the dimensions of the ribs are introduced. The best lattice structure is individuated by an analytical theory due to professor Vasiliev of the Central Research Institute of Special Machine Building (CRISM), the leading Russian Composite Center. The theory is based on the calculation of four safety factors for the helical rib strength, axisymmetric global buckling, non axisymmetric global buckling and the helical rib local buckling. Successively, a finite element analysis is performed in order to verify the analytical results. A software tool developed in Matlab environment prepares the finite element model, runs the finite element solver (MSC/Nastran) and reads the results. In the second step, an outer skin is added and the best lay-up for it is chosen; the maximum failure index for the skin laminate is calculated too. At the end the structure with the minimum weight and all margins of safety positive is individuated. The skin is extremely light so as to minimize overall weight. In the finite element model ribs and skin are simulated with beam and shell elements respectively; for the skin a common high-strength graphite/epoxy composite material is used, for the ribs an isotropic material with properties derived from experimental data. A grid-stiffened structure allows to reduce the structural mass of about 20% respect to a metallic reference baseline. Moreover, it can be quickly constructed by using filament winding technology; the process can be highly automated and the manufacturing costs can be reduced of the 30%.
Robust Design Analysis and Modeling of an Escalator for Vibration Reduction
Authors: Kwon Yi-Sug , Copeland George S. , Roberts Randy
Published: June 2008

A methodology is presented in this paper which illustrates how model-based dynamic analysis coupled with Robust Design techniques can be used to minimize the longitudinal vibration levels of the step chain in a sprocket-driven escalator system. A 60-DOF mechanical dynamic model of the escalator is developed and validated as a predictor of the tonal vibration levels as a function of escalator payload and running direction. The Taguchi method is then applied to this developed physics-based analytical model to identify critical to quality (CTQ) factors, flow requirements, and optimize performance (i.e., minimize vibration) using a response surface analysis. This methodology was verified as experimental measurements of the re-designed escalator show that the optimized design effectively suppresses the structural vibration levels.
Educational Application of the AutoDyn7 (CADyna) Program in Advanced Dynamics Course at the Pusan National University in Korea
Authors: Yoo Wan-Suk , Kim Sung-Soo , Kim Kwang-Suk , Sohn Jeong-Hyun
Published: June 2008

In this study, general purpose multibody dynamics codes AutoDyn7 (AUTOmobile DYNamics in G7) and CADyna (the NT version of the AutoDyn7) are introduced for the application to education in multibody dynamics. In the Auto-Dyn7 program, an efficient and systematic formulation for rigid and flexible bodies is derived using the velocity transformation technique. The Rapid-App for GUI (Graphic User Interface) builder and the Open Inventor for 3D graphic library have been employed to develop these programs in Silicon Graphics workstation. Several special purpose modules of the AutoDyn7 program are introduced to analyze vehicle dynamic characteristics. The NT version of the AutoDyn7, named CADyna, is also developed. The pre-processor for user input is developed with Visual C++ and the post-processor is developed with OpenGL and TeeChart for animation and graph.
Robust Truck Cabin Layout Optimization Using Advanced Driver Variance Models
Authors: Parkinson Matthew B. , Reed Matthew P. , Kokkolaras Michael , Papalambros Panos Y.
Published: June 2008

One important source of variance in the performance and success of products designed for use by people is the people themselves. In many cases, the acceptability of the design is affected more by the variance in the human users than by the variance attributable to the hardware from which the product is constructed. Consequently, optimization of products used by people may benefit from consideration of human variance through robust design methodologies. We propose that design under uncertainty methodologies can be utilized to generate designs that are robust to variance among users, including differences in age, physical size, strength, and cognitive capability. Including human variance as an inherent part of the product optimization process will improve the overall performance of the product (be it comfort, maintainability, cognitive performance, or other metrics of interest) and could lead to products that are more accessible to broader populations, less expensive, and safer. A case study involving the layout of the interior of a heavy truck cab is presented, focusing on simultaneous placement of the seat and steering wheel adjustment ranges. Tradeoffs between adjustability/cost, driver accommodation, and safety are explored under this paradigm.
Full Spectrum Cascade Analysis for Acceleration Signal in Compound Rub Malfunctions
Authors: Wu Fengqi , Meng G.
Published: June 2008

The acceleration signals of rotor vibration in operation consist of plenty of information about its running condition and can be used in machinery condition monitoring and fault diagnosis. The full spectrum cascade analysis of rotating machine vibrations, which has important information association with vertical, horizontal, and diagonal relationships, is an efficient method that enables the symptoms of some special types of fault (especially for rub) to be clear detected. Some typical rubs that caused by different malfunctions have been simulated through experiments in this study; Acceleration signals have been received by experimental apparatus and analyzed by full spectrum. The abrupt changes in surging acceleration signals of rotor malfunctions can be detected and its fault feature spectra are shown in full spectrum cascade plots. The results indicate that the potential and feasibility of this approach as the diagnosis of rotor malfunctions. The full spectrum cascade diagram can enrich the feature information for the knowledge base of the rotating machinery rub fault diagnosis system and is of great significance to rub diagnose faults in rotor more accurately.
A Probabilistic Analysis for Static and Dynamic Frequency of Blade With Uncertain Boundary Conditions
Authors: Wang Z. Q. , An L. Q. , Peng Z. Z.
Published: June 2008

A probabilistic analysis method is developed for frequencies analysis of turbine blade with uncertain boundary condition at the root of blade. The Ritz method is used to derive the eigenvalues equation of the rotating blade with uncertain root boundary condition. The matrix perturbation technique is employed for the probabilistic analysis to obtain the deterministic part of natural frequencies and vibration modes, the sensitivity matrix, the covariance matrix and the coefficient of variance (COV) for the natural frequencies. The effects of variations in the expectation and the variance of joint stiffness on the expectation and the variance of the natural frequencies are investigated.
Finite Element Discretization of Piezothermoelastic Equations Using the Generalized Equation of Heat Conduction
Authors: Vi´zva´ry Zsolt
Published: June 2008

In this paper, the derivation of the finite element equations of piezothermoelasticity is presented using the classical and generalized Fourier’s law. Galerkin’s method is used to the spatial discretization of the equations. Based upon these equations, a finite element code is under development.
An Off-Resonance Synchronous Vibration Based Method for Rotor System Damage Detections
Authors: Luo Huageng , Rodriguez Hector , Hallman Darren , Corbly Dennis
Published: June 2008

This paper presents a methodology of detecting rotor imbalances, such as mass imbalance and crack-induced imbalance, using shaft synchronous vibrations. A vibration detection algorithm is derived based on the first order nonresonant synchronous vibration response. A detection system is integrated by using state-of-the-art commercial analysis equipment. A laboratory rotor test rig with controlled mass imbalances was used to verify the integrated system. The system is then deployed to an engine sub-assembly test setup. Four specimens were used in the subassembly test and the test results are reported in the final section.
Hydroelasticity Vibration of a Rectangular Tank Wall
Authors: Kim K. S. , Kim D. W. , Lee Y. B. , Choi S. H. , Kim Y. S.
Published: June 2008

A theoretical study is carried out on the hydroelasticity vibration of a rectangular tank wall. It is assumed that the tank wall is clamped along the plate edges. The fluid velocity potential is used for the simulation of fluid domain and to obtain the added mass due to wall vibration. In addition, the vibration characteristics of stiffened wall of the rectangular tank are investigated. Assumed mode method is utilized to the stiffened plate model and hydrodynamic force is obtained by the proposed approach. The coupled natural frequencies are obtained from the relationship between kinetic energies of a wall including fluid and the potential energy of the wall. The proposed analytical approach was found to be in good agreement with the results of a well-known commercial three-dimensional finite element program.
Modeling of Stick-Slip in Multibody Drilling Systems
Authors: Khulief Y. A. , Al-Sulaiman F. A. , Bashmal S.
Published: June 2008

Drillstring vibration is one of the major causes for a deteriorated drilling performance. Field experience revealed that it is crucial to understand the complex vibrational mechanisms experienced by a drilling system in order to better control its functional operation and improve its performance. Stick-slip oscillations due to contact between the drilling bit and formation is known to excite severe torsional and axial vibrations in the drillstring. A multibody dynamic model of the drilling system including the drillpipes, drillcollars, and the rotary drive is formulated. The equation of motion of the rotating drillstring is derived using Lagrangean approach in conjunction with the finite element method. The model accounts for the gyroscopic effect, the inertia coupling, the effect of the gravitational force field, and the stick-slip interaction forces. Explicit expressions of the finite element inertia coupling and axial stiffening matrices are derived using a consistent mass formulation. Modal transformations are invoked to obtain a reduced order modal form of the dynamic equations. The developed model is integrated into a computational scheme to calculate time-response of the drillstring system in the presence of stick-slip excitations.
Simulation of Mating Between Non-Analytic Surfaces Using a Mathematical Programming Formulation
Authors: Pierce Robert Scott , Rosen David
Published: June 2008

In this paper we describe a new method for simulating mechanical assembly between components that are composed of surfaces that do not have perfect geometric form. Mating between these imperfect form surfaces is formulated as a constrained optimization problem of the form “minimize the distance from perfect fit, subject to non-interference between components.” We explore the characteristics of this mating problem and investigate the applicability of several potential solution algorithms. The problem can be solved by converting the constrained optimization formulation into an unconstrained problem using a penalty-function approach. We describe the characteristics of this unconstrained formulation and test the use of two different solution methods: a randomized search technique and a gradient-based method. We test the algorithm by simulating mating between component models that exhibit form errors typically generated in end-milling processes. These typical component variants are used as validation problems throughout our work. Results of two different validation problems are presented. Using these results, we evaluate the applicability of the mating algorithm to the problem of mechanical tolerance analysis for assemblies and mechanisms.
Spatial Layouts of Complex Mechanical Systems
Authors: Wang Yu-Xin , Wang Yong-Shan , Duffy Alex H. B.
Published: June 2008

Spatial layouts for complex mechanical systems are important both for the reliability design and industrial esthetics design of products. Existing of extra constrains caused by specific connections among basic mechanisms makes the layout problem particular and complex. In this paper, several common connecting relations existing in complex mechanical systems are generalized into three kinds of connections, serial connections, parallel connections, and closed connections, and then constrain equations caused by these connections are set up based on transforming matrixes. Expressing spatial spaces occupied by basic mechanisms with cuboid model, and dealing with constrains and interferences in mechanical systems with the fitness function, the spatial layout problem of complex mechanical systems is calculated based on an adaptive genetic algorithm. At last, taking a complex mechanical system consisting of eight basic mechanisms with parallel and serial connections as an example, the efficiency and validity of the algorithm presented in this paper have been verified.
Flexible Multibody Dynamics Analysis of Automobile Engine
Authors: Inagaki Mizuho , Kawamoto Atsushi , Aoyama Takayuki , Kawaguchi Atsushi , Mori Nobuyuki
Published: June 2008

The calculation method of dynamics behavior on automobile engine is getting more important as computer-aided engineering technique to design optimized mechanisms and structures for lighter weight, lower mechanical friction and lower noise. Engine system consists of deformable moving components and several kinds of mechanical joints, such as an oil lubricated bearing. Dynamics problem includes various kinds of noise and vibration phenomena in wide frequency range. Therefore, it is crucial to analyze precisely the coupling behavior between rigid motion and elastic deformation of moving components considering nonlinear dynamic effect of mechanical joint. In this study, we formulated equations of motion for the flexible multibody dynamics system and developed a computer software specialized for internal combustion engines. In the formulation, both rigid motion and elastic deformation are simply expressed by eigen modes on a local observer frame in order to calculate efficiently many deformation modes up to higher frequency range. In addition, several kinds of force elements are formulated to express the nonlinear forces of mechanical joints and the boundary conditions. The developed program has been verified by the experiments under running condition and applied to the real engine design.
On the Lagrangian Formalism of Nonholonomic Mechanical Systems
Authors: Yoshimura Hiroaki
Published: June 2008

The paper illustrates the Lagrangian formalism of mechanical systems with nonholonomic constraints using the ideas of geometric mechanics. We first review a Lagrangian system for a conservative mechanical system in the context of variational principle of Hamilton, and we investigate the case that a given Lagrangian is hyperregular, which can be illustrated in the context of the symplectic structure on the tangent bundle of a configuration space by using the Legendre transformation. The Lagrangian system is denoted by the second order vector field and the Lagrangian one- and two-forms associated with a given hyperregular Lagrangian. Then, we demonstrate that a mechanical system with nonholonomic constraints can be formulated on the tangent bundle of a configuration manifold by using Lagrange multipliers. To do this, we investigate the Lagrange-d’Alembert principle from geometric points of view and we also show the intrinsic expression of the Lagrange-d’Alembert equations of motion for nonholonomic mechanical systems with nonconservative force fields.
Hole-Making on a Bent Thick Plate
Authors: Kim Young-Il , Jun Cha-Soo
Published: June 2008

A method for cutting non-circular holes on a bent thick plate is proposed. Generally, in order to cut holes on large plates, a special-purpose 5-axis machine is needed. However, such a machine is unavailable in most machine shops. This paper provides a description of a method that utilizes a general-purpose 5-axis water-jet machine in place of the special-purpose machine: First, the bent piece is transformed into a flat plate, where the shape of the holes is reconstructed by considering deformation during bending. Then, after 5-axis NC data is generated, the holes on the flat plate are cut using the 5-axis water-jet machine. In the final step, the desired shape of the piece is obtained by bending the plate with its newly-cut holes. Some illustrations are provided in order to show the validity of the proposed method.
Inverse Dynamics-Based Fuzzy Logic Control of a Projectile Smart Fin
Authors: Trabia Mohamed B. , Parimi Surya Kiran , Yim Woosoon
Published: June 2008

A smart fin for a subsonic projectile should be able to produce maneuvering force and moment that can control its rotation during flight. Piezoelectric actuator is an attractive alternative to usual hydraulic actuators due to its simplicity. The cantilever-shaped actuator can also be fully enclosed within the hollow fin. It has an end fixed to the rotation axle of the fin while the other end is pinned at the tip of the fin. A dynamic model of the system, including external moment due to aerodynamic effects, is obtained using the finite element approach. This paper presents a novel approach for automatically creating fuzzy logic controllers for the fin. This approach uses the inverse dynamics of the smart fin system to determine the ranges of the variables of the controllers. Simulation results show that the proposed controller can successfully drive smart fin under various operating conditions.
Analytical Investigation of Hopf Bifurcations Occurring in a 1DOF Sliding-Friction Oscillator With Application to Disc-Brake Vibrations
Authors: Hetzler Hartmut , Seemann Wolfgang , Schwarzer Daniel
Published: June 2008

This article deals with analytical investigations on stability and bifurcations due to declining dry friction characteristics in the sliding domain of a simple disc-brake model, which is commonly referred to as “mass-on-a-belt”-oscillator. Sliding friction is described in the sense of Coulomb as proportional to the normal force, but with a friction coefficient μS which depends on the relative velocity. For many common friction models this latter dependence on the relative velocity can be described by exponential functions. For such a characteristic the stability and bifurcation behavior is discussed. It is shown, that the system can undergo a subcritical Hopf-bifurcation from an unstable steady-state fixed point to an unstable limit cycle, which separates the basins of the stable steady-state fixed point and the self sustained stick-slip limit cycle. Therefore, only a local examination of the eigenvalues at the steady-state, as is the classical ansatz when investigating conditions for the onset of friction-induced vibrations, may not give the whole picture, since the stable region around the steady state fixed point may be rather small. The analytical results are verified by numerical simulations. Parameter values are chosen for a model which corresponds to a conventional disc-brake.
Simulation of Low Speed Transition Curve Negotiation and Air Suspension Control to Prevent Wheel Load Reduction of Railway Vehicle
Authors: Suda Yoshihiro , Wang Wenjun , Komine Hisanao , Sato Yoshi , Nakai Takuji , Shimokawa Yoshiyuki
Published: June 2008

This paper presents the curving performance of railway vehicles with Air Suspensions. Air Suspensions sometimes cause reduction of Wheel Load at transition curve negotiation. The axle spring of leading axle outside and air spring of leading bogie outside will extend when passing the exit transition curve because of the distortion of the track plane. Because Air Suspension has an automatic leveling function that each air spring is controlled by Leveling Valve to maintain a constant length, air in the extended spring exhaust through Leveling Valve to reduce the pressure of this air spring in order to make it back to original length. So the air spring pressure of leading bogie outside reduces furthermore and Wheel Load of leading axle outside reduces severely. This may be the reason of derailment. The distortion of track plane unbalances inner pressure of Air Suspensions and vertical load of wheels at entrance transition curve, because of the nonlinear characteristic of Air Suspension system caused by the Leveling Valve. Computer simulation of low speed transition curve negotiation shows that the lower running speed is, the more severe unbalance of Air Suspension inner pressure and Wheel Load become. The reduction of 1st axle outside wheel at exit transition curve is depended on this Wheel Load unbalance phenomena at circular curve. And this running process influences the after behavior of railway vehicle. The simulation also shows that the longer entrance transition curve is, the more severely the 1st axle outside Wheel Load reduces. The full-scale bench experiments gave the result as nearly same as computer simulation. A new concept control device is proposed to prevent the reduction of Wheel Load at exit transition curve. Both the simulation and bench experiment proved its control performance of Wheel Load reduction prevention. And proposed control device can also be used in tilting control and kneeling control of railway vehicle. General multi-body dynamics analysis software SIMPACK is used to confirm advantageous effect of proposed control device and full vehicle curve passing simulation shows that derailment coefficient reduced when proposed control device is applied in transition curve negotiation.
Mechanical Aspects in Human Hearing
Authors: Eiber Albrecht , Breuninger Christian
Published: June 2008

For the description of the hearing process nonlinear models for normal, pathological and reconstructed ears were established based on multibody systems or finite elements. Nonlinearities are found in the constitutive equations of the ear drum, the ligaments and the coupling between implant and ossicles. Measurements in the clinical practice and in the lab are used to determine the dynamical behavior of the hearing organ and to derive the belonging model parameters. Simulations with various types of implants and different manners of incisions show the big influence of the points of attachment and the coupling conditions on the sound transfer. For actively driven implants the restricted coupling forces have to be regarded since distortion may lead to unacceptable results. The models allow virtual tests of passive and active implants to optimize their performance, to shorten clinical test series and an interpretation of injuries due to loud sound events.
Topology Optimization of the Inner Reinforcement for a Vehicle’s Hood Using Evolutionary Procedure
Authors: Shin In-Seob , Park Jae-Yong , Han Seog-Young , Kennedy Timothy C.
Published: June 2008

Topology optimization of the inner reinforcement for a vehicle’s hood has been performed by evolutionary structural optimization (ESO) method. The purpose of this study is to obtain optimal topology of the inner reinforcement for a vehicle’s hood considering static stiffness and natural frequency simultaneously. To do this, the multidisciplinary design optimization (MDO) technique was implemented. From several combinations of weighting factors, a Pareto-optimal solution was obtained. Optimal topologies were obtained by the ESO method, i.e., by eliminating the elements having the lowest efficiency from the structural domain. Topology optimization for a static stiffness problem has been accomplished by removing the element having the lowest efficiency measured by the elastic strain energy efficiency factor. Likewise, topology optimization for a natural frequency problem has been performed by eliminating the elements having the lowest efficiency measured by the natural frequency efficiency factor. As the weighting factor for natural frequency goes from zero to 1, it was found that the optimal topology transitions from the optimal topology of the static stiffness problem to that of the natural frequency problem. Therefore, it was concluded that the ESO method can be effectively applied to topology optimization of the inner reinforcement of a vehicle’s hood.
Simulation Projects With a Symbolic Multibody Modeling Software for Students in Belgium and Ecuador
Authors: Sass Laurent , Fisette Paul , Samin Jean-Claude
Published: June 2008

This paper describes a multibody simulation project, developed at the Universite´ Catholique de Louvain and at the Universidad San Fransisco de Quito, as an additional “learning layer” for students in engineering. The projects are all based on the use of a symbolic multibody software for generating the equations of motion of real-world applications (usually vehicles). Pedagogically, the use of such software gives the student the opportunity to focus on more enriching aspects, namely: the analysis of a real-world application, the formulation of consistent hypotheses for the considered system, and the multidisciplinary activity at the basis of a complete simulation project (mechanics, numerical methods, computer science and CAD).
Experimental and Analytical Analyses of a Sliding Tube Type Driveshaft Induced Vehicle Vibration
Authors: Juang Ten Bin , Cheng Ming-Te , Na Liqun
Published: June 2008

Driveline NVH (Noise, Vibration and Harshness) has become an integral attribute in defining how the vehicle NVH performance perceived by the customers in the automotive industry. The driveshaft component design community needs to make sure that the designed driveline system is robust and reliable to achieve the vehicle NVH targets, meanwhile maintains its durability performance. A slip mechanism in the driveline system is needed to accommodate the movements coming from the rear axle and rear suspensions when the vehicle travels on a rough road, or accelerates/decelerates abruptly. One design to accommodate the slip mechanism is to use a press-fitted sliding tube design. Because of its slip mechanism in the tubes, the fluctuation of the contact forces in the tubes, particularly in the vehicle coast down course, the interaction between the tubes becomes a nonlinear contact force phenomenon. This paper uses experimental and analytical linear tools to successfully understand the nonlinear behavior of the sliding tube driveshaft, and prevent a vehicle vibration issue created by the sliding tube driveshaft design.
Usability of Web-Based Design and Manufacturing Systems: Case Study of Micro Machining
Authors: Kim Hyung-Jung , Chu Won-Shik , Kang Hyuk-Jin , Ahn Sung-Hoon , Kim Dong-Soo , Jun Cha-Soo
Published: June 2008

In this paper, web-based design and manufacturing systems are compared with a commercial CAD/CAM system from the point of usability. The web-based systems included in this study were MIcro Machining System (MIMS) and SmartFab. In the MIMS architecture, a 3D model in STL format was read via a web browser, sent to the web server for toolpath planning, and NC codes were generated to be fed back to the designer through the web connection. In the SmartFab system, SolidWorks was used as the design interface with provided modified menus for micro machining. These additional menus were created by SolidWorks API that also provided web-based links to the toolpath planner. In the commercial CAD/CAM case, without using any web connection, SolidWorks or CATIA was used for design, and PowerMill was used as a CAM tool. For each design and manufacturing system, accessibility, user-friendliness, toolpath-reliability, and processing time were compared. Total 91 students tested these systems in undergraduate CAD class, and the feedback showed better performance of the web-based system in accessibility, user-friendliness, and processing time. However, reliability of the web-based system showed necessity of further improvement.
Stiffness Calculation and Dynamic Simulation of Air Spring
Authors: Xu Wei , He Lin , Shuai Chang-Geng , Ye Zhen-Xia
Published: June 2008

The paper presents a methodology to calculate the vertical stiffness of air spring. Investigation is focused on a convoluted air spring with one lobe. Based on the configuration of the membrane of the air spring and the geometry during its deflection, a stiffness expression dependant on the deflection is obtained. To have a good understanding of the performance of a single-degree-of-freedom system consisted of an air spring and a sprung mass, the paper provides an algorithm to simulate the motion of the system. The algorithm is a numerical step-by-step integration which combines explicit and implicit algorithms. A stiffness updating method based on the said stiffness expression is used in the dynamic simulation algorithm.
Solute Transport Simulated With the Fractional Advective-Dispersive Equation
Authors: San Jose Martinez F. , Pachepsky Y. A. , Rawls W. J.
Published: June 2008

Solute transport in soils and sediments is commonly simulated with the parabolic advective-dispersive equation, or ADE. Although the solute dispersivity in this equation is regarded as a constant, it has been found to increase with the distance from the solute source. This can be explained assuming the movement of solute particles belongs to the family of Le´vy motions. A one-dimensional solute transport equation was derived for Le´vy motions using fractional derivatives to describe the dispersion. This fractional advective-dispersive equation, or FADE, has two parameters — the fractional dispersion coefficient and the order of fractional differentiation α, 0<α≤2. Scale effects are reflected by the value of α, and the fractional dispersion coefficient is independent of scale. The ADE is a special case of the FADE. Our objectives were (a) to test applicability of the FADE to field data on solute transport in soils, and (b) to develop a numerical method to solve FADE that would assure the solute mass conservation. Analytical solutions of the FADE and the ADE were successfully fitted to the data from field experiments on chloride transport in sandy loam and bromide transport in clay loam soils. A numerical method to solve the boundary problem for FADE was proposed and tested, that uses the mass-conserving flux boundary condition. The FADE is a promising model to address the scale-dependence in solute dispersion in soils and sediments.
Cavitation Detection of a Centrifugal Pump Using Noise Spectrum
Authors: Chini Seyed Farshid , Rahimzadeh Hassan , Bahrami Mohsen
Published: June 2008

Cavitation is a common fault in centrifugal pumps. The detection and diagnosis of the onset and severity of the cavitation provide the means for preventing harmful effects such as deterioration of the hydraulic performance, damage to pump components, vibration and noise pollution. This paper presents a new approach for monitoring cavitation based on the noise measurement spectrum and analysis. Noise is measured using a microphone and a P.C. equipped with soundcard and Matlab6.1 uses Fast Fourier Transform to change the domain from time to frequency. It has been found that the sound pressure level at some frequencies can be used as a primary monitoring feature to detect the onset of the cavitation and to quantify the severity of the cavitation. One of these frequencies is related to the number of blades. Other detection features are defined in other frequencies, as well. Flow rate increase was used to have stronger cavitation effect.
Robust Design Strategy Applied to Vehicle Suspension System
Authors: Chatillon Marie-Maud , Je´ze´quel Louis
Published: June 2008

This paper presents a robust design strategy for the design of complex mechanical systems. The design strategy is based on the hierarchical optimization of design variables. Simplified physics-based models are used in each step of the design and optimization process. The steps of the design process correspond to the different stages of the design process, from functional requirements and decomposition, to design of the parts. Besides optimization, robustness of the solution to variations in design variables and environmental conditions is essential. The methodology presented in this paper is applied to the optimization of the design parameters of a vehicle suspension system. The consideration of parameters uncertainties from early design stages, the organization of the optimization process, and the use of simplified models, allow to obtain performant and robust design, and to manage design trade-offs.
About Lagrangian Formulation of Classical Fields Within Riemann-Liouville Fractional Derivatives
Authors: Baleanu Dumitru , Muslih Sami I.
Published: June 2008

Recently, an extension of the simplest fractional problem and the fractional variational problem of Lagrange was obtained by Agrawal. The first part of this study presents the fractional Lagrangian formulation of mechanical systems and introduce the Levy path integral. The second part is an extension to Agrawal’s approach to classical fields with fractional derivatives. The classical fields with fractional derivatives are investigated by using the Lagrangian formulation. The case of the fractional Schro¨dinger equation is presented.
Parameterising Styling Lines for Reverse Design Using Free Form Shape Analysis
Authors: Langerak Thomas R. , Vergeest Joris S. M. , Song Yu
Published: June 2008

Styling lines are elongated areas of abrupt curvature that have some meaning for the styling of a shape. Although many methods have been developed to extract these lines on a purely geometrical level, few methods exist to give the user the control of modifying such a styling line on a higher level of abstraction. In this paper, a method is proposed for the automatic extraction of control elements from free form shapes. These control elements are: the trajectory curve, which lies along the direction of the styling line, and the profile curve, which lies perpendicular to the styling line in the area in which the styling line is embedded. These control elements are simple, intuitive handles for modifying the styling line, which can be controlled by the user in a simple sketching action. The extraction method makes use of curvature analysis, and finds critical points where the curvature has an extreme. By setting several parameters, the user is able to control the extraction method to fine-tune it according to his/her wishes. The method is demonstrated on the digital representation of a computer mouse and is discussed for use in the parameterisation of other features.
Biking Without Pedaling
Authors: Chitta Sachin , Kumar Vijay
Published: June 2008

It is well known that skilled bicycle riders can balance and propel themselves forward using motions of the handlebar. We present the complete nonlinear dynamics and control of such a pedal-less bicycle with a rider. Propulsion is achieved not by pedaling but by a cyclic motion of the steering axis of the bicycle. It is shown that this kind of actuation results in net forward motion of the bicycle and a building up of momentum. The dynamics of the bicycle and rider in a transverse plane are similar to that of a two link underactuated system where only the second link is actuated. A linear analysis of the bicycle is used to derive a control law for the rider to stabilize the bicycle about its upright position while the periodic motion of the steering axis drives the bicycle forward. After the bicycle attains a higher speed, it is easily stabilizable.
Optimal Kinematic Design of Gantry Parallel Robots
Authors: Berbyuk Viktor , Johannesson Lars
Published: June 2008

This paper addresses some issues of optimal kinematic design of parallel robot with 3 degrees of freedom. Robot performs translational gantry type motion with a large workspace. The structure’s nominal kinematics is identical to the Linear Delta Robot, the difference being the way which the links are organized. In order to yield a design of the Gantry Parallel Robot with a large workspace volume and good kinematic properties, multi-criteria optimization is used. The objective functions comprise a space utilization index and the inverse conditioning number of the Jacobian matrix. Three different geometrical layouts of the robot are examined and the Pareto optimality between the objective functions is found for several different cases. Pareto-optimal curves showing the relationship between the workspace size and the manipulability are presented as a tool for the designer. The obtained results give a good overview of the kinematic properties of the Gantry Parallel Robot that can be used for designing the parallel structures for various applications.
Development of Virtual Flow Model for Process Design in Vacuum Assisted Resin Infusion Molding Operations
Authors: Khattab Ahmed , El-Gizawy A. Sherif
Published: June 2008

A virtual flow model for process design in vacuum assisted resin infusion operations is developed. It uses a control volume technique based on finite difference method to characterize flow behavior during resin infusion in molding woven fiber composite structures. In order to enhance the visual capability of the developed virtual model, a geometric reconstruction scheme is used to present the resin flow front at fixed time increment. The Graphic Interchange Format (GIF) is used to combine images into a single file to create animation. This model provides capabilities for prediction of flow pattern, pressure distribution inside the mold, and evolved defects. Several case studies were conducted to evaluate the effectiveness of the developed model.
Capturing Empirically Derived Design Knowledge for Creating Conceptual Design Configurations
Authors: Kurtoglu Tolga , Campbell Matthew I. , Gonzalez Joah , Bryant Cari R. , Stone Robert B. , McAdams Daniel A.
Published: June 2008

In an ideal design process, designers envision a configuration of components prior to determining dimensions or sizes of these components. Given the breadth of suppliers and production methods that exist today, most engineered artifacts are a mix of both custom-made parts and OEM (original equipment manufacturer) parts. The design of any future artifact must be carefully planned to take advantage of the diverse set of possibilities. We conjecture that computational design tools could be developed to help designers navigate the design space in creating configurations from detailed specifications of function. In this research, a methodology is developed that extracts design knowledge from an expanding online library of components in the form of grammar rules. From an initial implementation of forty-five rules compiled from 15 components extracted from three products, we demonstrate a computational process that builds a new design configuration by borrowing concepts from how common functions are solved in related designs.
Description of Multibody Systems in MechXML (Mechanism eXtensible Markup Language) Including Control
Authors: Vidal Jesu´s , Garci´a de Jalo´n Javier
Published: June 2008

MechXML is an XML-based language aimed at describing multibody systems and their simulations (see a more detailed description in [1]). With the appropriate easy-to-build parsers, a data file written in this language can be executed with little or no modification at all in many commercial and research-oriented programs. The purpose of this paper is twofold: to introduce briefly this language and to describe with more detail the new developments that allow the definition of continuous control subsystems. The definition of controls is based on block diagrams. The user defined functions are a general way to customize multibody simulation software so as to enable it to deal with arbitrary forces and constraints. They are described here because they can be used to describe the actions of control systems, too. At the end, a file written according to the rules of MechXML is parsed and run in two programs as different as MSC.ADAMS and SimMechanics.
A Boundary Tracing Method and Its Application to Inward-Oriented Rotating Cantilever Beam
Authors: Gaul Lothar , Wagner Nils
Published: June 2008

Every physical system is described by parameters, and one goal of the present contribution is to study the movements of eigenvalues in the complex plane depending on the system inherent parameters. A main focus lies in tracing the boundary curve which separates unstable from marginally stable domains in the parameter space. Hence, there is no need to study the whole parameter space but a certain subset which can be characterized by a zero eigenvalue. The method is illustrated by means of a static stability problem arising in the study of rotating blades.