bluuebunny/crossref_metadata_2025 huggingface dataset:
A Finite Element Investigation to Modal and Dynamic Behaviors of Planetary Gearings Concerning the Effect of Bearing and Carrier Stiffnesses
Authors: Huang Kuo Jao , Zhang Shou Ren
Published: June 2012

A finite element (FE) method is used to analyze modal and dynamic behavior of planetary gear systems (PGSs) focusing on the effect of bearing and carrier stiffness. Using derived tooth profile equations, elements for gear can be parametrically created. Then, the 2D/3D FE models of a planetary gear system (PGS) are constructed. Accordingly, structural natural frequencies and modal shapes are calculated after adequately assigning the material, boundary conditions, and tooth contact of gear pairs. An index, namely dimensionless slope, is defined to reflect the modal property due to the bearing stiffness change. Influence of carrier material and gear bearing stiffnesses on modal behavior is investigated. Several results of the PGS modal characteristics affected by the material and bearing stiffness are also obtained. Besides, the dynamic responses of the PGSs are analyzed under the carrier rotation. Finally, dynamic fillet stress and loading inequality among gear pairs due to planet bearing stiffness variation are analyzed. The FE approach presented can conveniently demonstrate modal and dynamic behaviors of PGSs.
Modally-Tuned Influence Coefficients for Low-Speed Balancing of Flexible Rotors
Authors: Khulief Y. A. , Mohiuddin M. A.
Published: June 2012

The need to devise a low-speed balancing method for balancing high-speed rotors was recognized and addressed. In this paper, a scheme that combines both the influence coefficients and modal balancing techniques is presented. The scheme is developed for low-speed balancing of high-speed rotors, and relies on knowledge of modal characteristics of the rotor. The conditions for applicability of the method were stated in the light of the experientially estimated rotor deflection mode shapes. An experimental test rig of a flexible rotor was constructed to verify the applicability and reliability of the low-speed balancing scheme.
Analysis, Design, and Testing of a Control System for an Air Turbine Rotor Drive
Authors: Jantz Robert , Flowers George T.
Published: June 2012

This work details the development and implementation of a control system to regulate the speed of a magnetically-suspended rotor and flywheel. Development began with the installation of an electronic flow control valve and all instrumentation needed to measure rotor response. Once all hardware was in place, a simulation model of the system, consisting of actuator (electronic valve) and plant (air turbine magnetic bearings, rotor and flywheel), was created. This model was developed using system identification techniques where a step input is applied to the plant and its response is measured. A transfer function of the plant was derived from these tests, and it relates volumetric flow rate of air to rotor speed and uses variable coefficients. Using this model, a control system was developed and experimentally evaluated, with good results.
A Plug and Play Middleware for Sensory Modules, Actuation Platforms and Task Descriptions in Robotic Manipulation Platforms
Authors: Elkady Ayssam , Joy Jovin , Sobh Tarek
Published: June 2012

We are developing a framework (RISCWare) for the modular design and integration of sensory modules, actuation platforms, and task descriptions that will be implemented as a tool to reduce efforts in designing and utilizing robotic platforms. The framework is used to customize robotic platforms by simply defining the available sensing devices, actuation platforms, and required tasks. The main purpose for designing this framework is to reduce the time and complexity of the development of robotic software and maintenance costs, and to improve code and component reusability. Usage of the proposed framework prevents the need to redesign or rewrite algorithms or applications due to changes in the robot’s platform, operating systems, or the introduction of new functionalities. In this paper, the RISCWare framework is developed and described. RISCWare is a robotic middleware used for the integration of heterogeneous robotic components. RISCWare consists of three modules. The first module is the sensory module, which represents sensors that collect information about the remote or local environment. The platform module defines the robotic platforms and actuation methods. The last module is the task-description module, which defines the tasks and applications that the platforms will perform such as teleoperation, navigation, obstacle avoidance, manipulation, 3-D reconstruction, and map building. The plug-and-play approach is one of the key features of RISCWare, which allows auto-detection and auto-reconfiguration of the attached standardized components (hardware and software) according to current system configurations. These components can be dynamically available or unavailable. Dynamic reconfiguration provides the facility to modify a system during its execution and can be used to apply patches and updates, to implement adaptive systems, or to support third-party modules. This automatic detection and reconfiguration of devices and driver software makes it easier and more efficient for end users to add and use new devices and software applications. In addition, the software components should be written in a flexible way to get better usage of the hardware resource and also they should be easy to install/uninstall. Several experiments, performed on the RISCbot II mobile manipulation platform, are described and implemented to evaluate the RISCWare framework with respect to applicability and resource utilization.
A Novel Approach to Real-Time Flexible Multibody Simulation: Sub-System Global Modal Parameterization
Authors: Naets Frank , Heirman Gert H. K. , Desmet Wim
Published: June 2012

This paper introduces a novel model reduction technique, namely Sub-System Global Modal Parameterization (SS-GMP), for real-time simulation of flexible multibody systems. In the past, other system-level model reduction techniques have been proposed for this purpose, but these were limited in applicability due to the large storage requirements for systems with many rigid degrees-of-freedom (DOFs). However, in the SS-GMP approach, the motion of a mechanism is split up into a global motion and a relative motion of the (sub-)system. The relative motion is then reduced according to the Global Modal Parameterization, which is a model reduction procedure suitable for closed chain flexible multibody systems. In combination with suitable explicit solvers, the SS-GMP approach enables (hard) real-time simulations due to the strong reduction in the number of DOFs and the conversion of a system of differential-algebraic equations into a system of ordinary differential equations. The proposed approach is validated numerically with a quarter-car model. This fully flexible mechanism is simulated faster than real-time on a regular PC with the SS-GMP approach while providing accurate results.
Self-Repairing Process in Self-Reconfigurable Robots Based on Geometrical Characteristics
Authors: Fei Yanqiong , Zhang Xin
Published: June 2012

Self-reconfigurable modular robot consists of many identical modules. By changing the connections among modules, the structure of the robot can flexibly change into many other structures. First, the module is designed which can finish the self-repairing action and its disconnection/connection mechanism is analyzed. Second, a distributed self-repairing process based on the geometrical characters of the modular robot is presented. The method of the Breadth-First-Search and the Depth-First-Search is applied to look for a locomotion path by which a faulty module is ejected and replaced by a spare module. The method can be used to show the self-repairing task of most lattice-type modular robots. It’s effective to solve large numbers of computing problems when the faulty module is inside a large-scale system. At last, a simulation of (2 × 4 + 1)3 modules shows the feasibility and effectiveness of the self-repairing method in the self-reconfigurable robot.
Utilization of Simple Scaling Laws for Modulating Tip-Sample Interaction Forces in Aqueous Environment AFM Characterization: Application to the Self-Assembly of Protein Polymers
Authors: Solares Santiago D. , Chang Jonathan , Seog Joonil , Kareem Adam U.
Published: June 2012

We have recently reported on experimental observations of silk-elastin-like protein polymers (SELPs) that self-assembled into 1-dimensional nanofibers on mica surfaces upon application of a mechanical stimulus with atomic force microscopy (AFM) in water. SELPs are genetically engineered block co-polymers made of silk-like blocks (Gly-Ala-Gly-Ala-Gly-Ser) from Bombyx mori (silkworm) and elastin-like blocks (Gly-Val-Gly-Val-Pro) from mammalian elastin. The experiment consisted of adsorbing the protein polymer onto a freshly cleaved mica surface, followed by AFM characterization under different sets of imaging parameters, each of which led to different nanofiber coverage rates. In order to gain further understanding of the factors governing the self-assembly process, we utilized multimodal AFM simulation to formulate and guide the implementation of a suitable force modulation strategy, which allowed us to observe trends of the surface coverage rate as a function of the applied peak forces. The simulations suggest that a nearly linear control of the peak tapping forces can be achieved by following simple scaling laws based on the harmonic oscillator model.
Initial Modeling of Material Phase Driven Localized Corrosion
Authors: Wimmer Stephanie A. , DeGiorgi Virginia G.
Published: June 2012

Localized corrosion often occurs when regions of a single material demonstrate a difference in electrochemical potential. Cathodic and anodic regions can develop in a component comprised of a single material. This variation is one cause of localized corrosion damage. This phenomenon of localized anode and cathode regions is well documented but not well understood. In this work the authors are examining variations in electrochemical response of individual grains within a metallic material. The objective is to determine if the distinct electrochemical response associated with austenite and ferrite phases in steel are sufficient to create a localized electrochemical corrosion cell. In this paper the authors present the first of a series of models that capture localized electrochemical corrosion driven by variations in grain polarization response.
Computational Modeling of Fugitive Phase Rotations Within Tape Cast Ceramics
Authors: Wimmer Stephanie A. , Pan Ming-Jen
Published: June 2012

For complex ceramic parts, new fabrication methods, such as the fugitive phase approach, are required. A common problem in the creation of ceramic parts is obtaining accurate dimensions of the final part. The sintering process makes it very difficult to create precise complex geometries. Tolerances achieved with green ceramics do not carry over to acceptable tolerances on the finished part due to non-uniform shrinkage and warping. The authors are investigating the application of the fugitive phase processing method, which might be able to fabricate topologically complex monolithic ceramic parts with precise tolerances. This paper is a continuation of previous work and examines the lamination step of the fugitive phase approach ceramic fabrication process; the step in which the fugitive phase material is integrated with the green ceramic material. In this step, the pressing along with the geometric layout of the fugitive phase material create an uneven pressure distribution in the green ceramic. Of particular concern is the rotation of the fugitive phase materials during the lamination step. A computational model of the lamination process is used to examine how the plasticity of the fugitive phase material along with computational boundary conditions affect the geometry of the green ceramic produced at the end of the lamination step prior to sintering. The resulting stress, strain energy, and deformed shapes are examined and compared. This information will be used to adjust the experimental investigations of the fugitive phase approach ceramic fabrication process that is working to create topologically complex ceramic components.
Dynamic Response of Multibody Systems With Multiple Clearance Joints
Authors: Flores Paulo , Lankarani Hamid M.
Published: June 2012

A general methodology for the dynamic modeling and analysis of planar multibody systems with multiple clearance joints is presented. The inter-connecting body components that constitute a real joint are modeled as colliding bodies, which dynamic behaviors are influenced by geometric, physical and mechanical properties of the contacting surfaces. A continuous contact force model, based on the elastic Hertz theory, together with a dissipative term, is used to evaluate the intra-joint contact forces. The incorporation of the friction, based on the classical Coulomb’s friction law, is also included. The suitable contact force models are embedded into the dynamic equations of motion for the multibody system. A simple mechanical system with multiple clearance joints is used to demonstrate the accuracy and efficiency of the presented approach and to discuss the main assumptions and procedures adopted. The effects of single versus multiple clearance joints are discussed.
A Note on Flow Regimes and Churning Loss Modelling
Authors: Changenet C. , Leprince G. , Ville F. , Velex P.
Published: June 2012

The purpose of this study is to investigate the various fluid flow regimes generated by a pinion running partly immersed in an oil bath and the corresponding churning power losses. In a series of papers, the authors have established several loss formulae whose validity depends on two different flow regimes characterized via a critical Reynolds number. Based on some new measurements for transient operating conditions, it has been found that the separation in two regimes may be not accurate enough for wide-faced gears and high temperatures. An extended formulation is therefore proposed which, apart from viscous forces, introduces the influence of centrifugal effects. The corresponding results agree well with the experimental measurements from a number of gears and operating conditions (speed, temperature). Finally, the link between churning and windage losses is examined and it is concluded that the physical mechanisms are different thus making it difficult to establish a general correlation between the two phenomena. In particular, it is shown that tooth geometry is of secondary importance on churning whereas, the air-lubricant circulation being different for spur and helical gears, it substantially impacts windage.
Multidisciplinary Design Optimization for Complex Engineered Systems Design: State of the Research and State of the Practice—Report From a National Science Foundation Workshop
Authors: Simpson Timothy W. , Martins Joaquim R. R. A.
Published: June 2012

Multidisciplinary design optimization (MDO) has evolved remarkably since its inception 25 years ago. Despite these advances, the design of complex engineered systems remains a challenge, and many large-scale engineering projects are routinely plagued by exorbitant cost overruns and delays. To gain insight into these challenges, 48 people gathered from industry, academia, and government agencies to examine MDO’s current and future role in designing complex engineered systems. This paper summarizes the views of five distinguished speakers on the “state of the research” along with the discussions from an industry panel of representatives from Boeing, Caterpillar, Ford, NASA Glenn Research Center, and United Technologies Research Center on the “state of the practice”. This paper also summarizes the future research topics identified by breakout groups in five key areas: (1) modeling and the design space; (2) metrics, objectives, and requirements; (3) coupling in complex engineered systems; (4) dealing with uncertainty; and (5) people and workflow. Finally, five over-arching themes are offered to advance MDO. First, we need to engage more disciplines outside of engineering and look for opportunities to use MDO outside of its traditional areas. Second, MDO problem formulations must evolve to encompass a wider range of design criteria. Third, we need effective strategies for putting designers “back in the loop” during MDO. Fourth, we need to do a better job of publicizing the successful examples of MDO so that we can improve the “buy in” that is needed to advance MDO in academia, industry, and government agencies. Fifth, we need to better educate our students and practitioners on systems design, optimization, and MDO along with their benefits and drawbacks.
Addressing Limitations of Pareto Front in Design Under Uncertainty
Authors: Pandey Vijitashwa , Mourelatos Zissimos P. , Nikolaidis Efstratios
Published: June 2012

Engineering design reconciles design constraints with decision maker preferences. The task of eliciting and encoding decision maker preferences is, however, extremely difficult. A Pareto front representing the locus of the non-dominated designs is therefore, often generated to help a decision maker select the best design. In this paper, we show that this method has a shortcoming. We show that when there is uncertainty in both the decision problem variables and in the decision maker’s preferences, this methodology is inconsistent with multi-attribute utility theory, unless the decision maker trades off attributes or some functions of them linearly. This is a strong restriction. To account for this, we propose a methodology that enables a decision maker to select the best design on a modified Pareto front which is acquired using envelopes of a set of certainty equivalent surfaces. This methodology does not require separability of the multi-attribute utility function into single attribute utilities, nor does it require the decision maker to trade the attributes (or any function of them) linearly. We demonstrate this methodology on a simple optimization problem and in design of a reduction gear.
Locomotion of One Degree of Freedom Worm Robots
Authors: Zarrouk David , Shoham Moshe
Published: June 2012

Worm-like robots have been widely designed for applications including maintenance of small pipes and medical procedures in biological vessels such as the lungs, intestines, urethra and blood vessels. The robots must be small, reliable, energy efficient and capable of carrying cargos such as cameras, biosensors, and drugs. Earthworm and inchworm robots have been traditionally designed with three or more cells and clamps and a corresponding number of actuators. The use of multiple actuators complicates the design, makes the system more cumbersome, reduces power efficiency and requires more control for coordination. In the present study, we analyze the worm locomotion, in terms of the distance between the cells and clamping modes, and model it as a cyclic function of the time. That is, the worm locomotion can be represented by a single degree of freedom. Consequently, multi-cells worm-like robots actuated by a single motor were designed. The robots employ a rotating screw-like shaft that mechanically coordinates the sequencing of the cell displacement as well as the clamping modes with no external control for each separate cell. This design allows for significant miniaturization and reduces complexity and cost of the system. Two prototypes of earthworm and inchworm robots for locomotion within 20mm and 70mm wide tubes were manufactured. The robots demonstrated high reliability and strong grip. They can crawl vertically while carrying a payload at a rate of few cm/s for the larger robots and roughly 1cm/s for the smaller ones. Furthermore, the low power consumption enables the robots to crawl wirelessly for hundreds of meters using standard off the shelf batteries.
Comparison of Transient and Steady-State Behaviors in Unwinding Mechanism
Authors: Yoo Wan-Suk , Kim Kun-Woo , An Deuk-Man , Lee Jae-Wook
Published: June 2012

In this study, the transient analysis of a cable unwinding from a cylindrical spool package is first studied and compared to experiment. Then, a steady-state solution is also compared to transient solution. Cables are assumed to be withdrawn with a constant velocity through a fixed point which is located along the axis of the package. When the cable is flown out of the package, several dynamic forces, such as inertial force, Coriolis force, centrifugal force, tensile force, and fluid-resistance force are acting on the cable. Consequently, the cable becomes to undergo very nonlinear and complex unwinding behavior which is called unwinding balloon. In this paper, to prevent the problems during unwinding such as tangling or cutting, unwinding behaviors of cables in transient state were derived and analyzed. First of all, the governing equations of motion of cables unwinding from a cylindrical spool package were systematically derived using the extended Hamilton’s principles of an open system in which mass is transported at each boundary. And the modified finite difference methods are suggested to solve the derived nonlinear partial differential equations. Time responses of unwinding cables are calculated using Newmark time integration methods. The transient solution is compared to physical experiment, and then the steady-state solution is compared to transient solution.
Fundamental Concepts for Product Designs Based on Pareto Optimum Solutions
Authors: Yoshimura Masataka
Published: June 2012

This paper proposes fundamental concepts for goal-defined product designs, and practical methodologies for achieving optimal designs based these concepts. Also emphasized are the functions and significance of Pareto optimum solution sets in multi-objective optimizations during the execution of the proposed methodologies. Three main concepts for product design optimization are presented. First, the goal of the product design optimization is specified to obtain the best harmony of related (and often conflicting) characteristics, where Pareto optimum solution sets represent this harmony and more preferable degrees of harmony cause an increase in social profit. Second, to obtain design solutions that maximize the desired harmony, deeper level characteristics in the design optimization problem are derived based on simplification or decomposition of the usual surface level characteristics, and optimizations are initiated from these deeper levels where the most important and influential aspects of the design problems are easiest to recognize. The third concept entails the use of collaboration with specialist experts concerning the product characteristics, focusing on Pareto optimum solution sets obtained in deeper level optimizations, so that these experts can facilitate the development of more preferable results based on their own ideas and knowledge. The interrelationships between the second and third concepts are described and used to obtain globally optimal design solutions that have the highest degree of harmony for the required product design objectives. The proposed concepts and methodologies for product design optimizations are demonstrated using certain designs for articulated robots.
Fuzzy Codimension Two Bifurcations
Authors: Hong Ling , Sun Jian-Qiao
Published: June 2012

By means of fuzzy generalized cell mapping method, a Duffing-Van der Pol oscillator in the presence of fuzzy noise is studied in a regime where two symmetrically related fuzzy period-one attractors grow and merge as the intensity of fuzzy noise is increased. By introducing a small symmetry-breaking parameter to break the symmetry, the merging explosion bifurcation unfolds to a pattern of two catastrophic and explosive bifurcations. Considering both the intensity of fuzzy noise and the symmetry-breaking parameter together as controls, a codimension two bifurcation of fuzzy attractors is defined, and two examples of additive and multiplicative fuzzy noise are given. Such a codimension two bifurcation is fuzzy noise-induced effects which cannot be seen in the deterministic systems.
An Experimental Validation of the Time-Varying Initialization Response in Fractional-Order Systems
Authors: Gambone Tom , Hartley Tom T. , Lorenzo Carl F. , Adams Jay L. , Veillette Robert J.
Published: June 2012

This paper provides an experimental validation of the required time-varying initialization response for fractional-order systems. The experiment considers thermal conduction in a long aluminum rod, whose thermal impedance can be approximated as a half-order integral. Experimental results using seven different history functions are compared with theoretical predictions. The experimental results compare well with the expected theoretical predictions. Deviations from the theoretical predictions are discussed.
Modeling and Control of a Compliantly Engineered Anthropomimetic Robot in Contact Tasks
Authors: Potkonjak Veljko , Jovanovic Kosta , Svetozarevic Bratislav , Holland Owen , Mikicic Dusan
Published: June 2012

This paper attempts to develop a dynamic model and design a controller for a fully anthropomorphic, compliantly driven robot. To imitate muscles, the robot’s joints are actuated by DC motors antagonistically coupled through tendons. To ensure safe interaction with humans in a human-centered environment, the robot exploits passive mechanical compliance, in the form of elastic springs in the tendons. To enable simulation, the paper first derives a mathematical model of the robot’s dynamics, starting from the “Flier” approach. The control of the antagonistic drives is based on a biologically inspired puller-and-follower concept where at any instant the puller is responsible for the joint motion while the follower keeps the inactive tendon from slackening. In designing the controller, it was first necessary to use the advanced theory of nonlinear control for dealing with individual joints, and then to apply the theory of robustness in order to extend control to the multi-jointed robot body.
On the Contact Modeling and Analysis of the Human Knee Joint
Authors: Machado Margarida , Flores Paulo
Published: June 2012

The goal of this work is to study the influence of the contact force model and contact material properties on the dynamic response of a human knee joint. For this purpose, a multibody knee model composed by two rigid bodies, the femur and the tibia, and four nonlinear spring elements that represent the main knee ligaments, is considered. The contact geometrical profiles are extracted from medical images and fitted using spline functions. The tibia motions are modeled, not using a conventional kinematic joint, but rather in terms of the action of the ligaments and potential contact between the bones. Besides, an external force is applied on the center of mass of the tibia in order to simulate the force of the quadriceps muscle group. When a contact is detected, a continuous contact force law is applied. The contact force laws studied are the Hertz, the Hunt-Crossley and the Lankarani-Nikravesh models. Results obtained from computational simulations show that Hertz law is less suitable to describe the dynamic response of the cartilage contact, because this pure elastic model does not account for the viscoelastic nature of the human articulations. Moreover, the effect of the amplitude of the external applied force on the dynamic response of the knee joint model is also evaluated. The obtained results show that the increase of the amplitude of the external applied force increases the contact indentations and lead to an earlier first impact. As far as to the influence of the material contact properties is concerned, the dynamic response of a healthy and natural knee is analyzed and compared with three pathological and two artificial knee models. Results demonstrate that the presence of the cartilage reduces significantly the knee contact forces.
Flank-Load-Carrying Capacity of Case Hardened Gears With Grinding Burn
Authors: Ho¨hn Bernd-Robert , Stahl Karsten , Oster Peter , Tobie Thomas , Schwienbacher Simon , Koller Peter
Published: June 2012

A high geometric accuracy of case-hardened gears requires a grinding process after heat treatment. Inappropriate grinding conditions can induce surface tempering, alter hardness and lead to an unfavorable residual stress state. This effect is commonly known as grinding burn. The influence of grinding burn on the flank-load-carrying capacity was systematically investigated within a research project. The results of experimental tests and the analysis of surface and near subsurface parameters allowed a correlation between grinding burn grade, material characteristics and flank-load-carrying capacity. A main result of this project is a proposal for the calculation of surface durability of gears which implicates the influence of grinding burn. This paper summarizes results of the experimental testing and the accompanying analyses. The main focus herein is the consideration of an altered hardness and residual stress state in a material-physically based model for calculating the load capacity of gears.
Control Constraint Realization Applied to Underactuated Aerospace Systems
Authors: Masarati Pierangelo , Morandini Marco , Fumagalli Alessandro
Published: June 2012

This paper discusses the problem of control constraint realization applied to the design of maneuvers of complex under-actuated systems modeled as multibody problems. Applications of interest in the area of aerospace engineering are presented and discussed. The tangent realization of the control constraint is discussed from a theoretical point of view and used to determine feedforward control of realistic under-actuated systems. The effectiveness of the computed feedforward input is subsequently verified by applying it to more detailed models of the problems, in presence of disturbances and uncertainties in combination with feedback control. The proposed applications consist in the position control of a complex closed chain mechanism representative of a robotic system, the control of a simplified model of a canard and a conventional air vehicle in the vertical plane, and the angular velocity control of a wind-turbine. In the aeromechanics examples, the tangent realization of the control relies on the availability of the Jacobian matrix of an aeroelastic model. All problems are solved using a free general-purpose multibody software that writes the constrained dynamics of multi-field problems in form of Differential-Algebraic Equations (DAE). The equations are integrated using A/L-stable algorithms. The essential extension to the multibody code consisted in the addition of the capability to write arbitrary constraint equations and apply the corresponding reaction multipliers to arbitrary equations of motion. This allowed to exploit the modeling capabilities of the formulation without any undue restriction on the modeling requirements.
Contact Whirling Vibration of a Rotating Shaft Supported by a Repulsive Magnetic Bearing and the Influence of the Axial Displacement on Its Suppression
Authors: Sugai Tomohiro , Inoue Tsuyoshi , Ishida Yukio
Published: June 2012

A rotating shaft supported by a repulsive magnetic bearing may contact with a backup bearing during the passage of the critical speed as the damping coefficient of the repulsive magnetic bearing is small. This paper investigates the contact vibration during passage of the critical speed. Particularly, the influence of the axial displacement of the repulsive magnetic bearing on the escape speed from the contact vibration is focused. As a result, it is clarified that the rotational speed of the escapement from the contact vibration decreases as the axial displacement increases. It is explained by the change of both the linear stiffness and nonlinear coefficient in the increase of the axial displacement.
Visualizing Fractional Control System Approximations by Means of Multidimensional Scaling
Authors: Machado J. A. Tenreiro
Published: June 2012

This paper addresses the use of multidimensional scaling in the evaluation of fractional system approximations. Algorithms are analysed based on the time response of the closed loop system under the action of a reference step input signal. Two alternative performance indices, based on the time and frequency domains, are tested. The numerical experiments demonstrate the feasibility of the proposed methodology.
A Fatigue Model for Spur Gear Contacts Operating Under Mixed Elastohydrodynamic Lubrication Conditions
Authors: Li Sheng , Kahraman Ahmet , Klein Mark
Published: June 2012

This paper presents a model to predict the crack formation fatigue lives of spur gear contacts operating under mixed lubrication conditions where surface roughnesses introduce intermittent metal-to-metal contacts and severe stress concentrations. The proposed model consists of several submodels including (i) a gear load distribution model to determine the normal tooth force distribution along the tooth profile, incorporating any profile modifications and manufacturing deviations, (ii) a mixed elastohydrodynamic lubrication model customized to handle transient contact conditions of gears, (iii) a stress formulation that assumes the plane strain condition to compute the transient elastic stress fields on and below the tooth surface induced by the mixed lubrication surface pressure and shear stress distributions, and (iv) a multi-axial fatigue model to predict the crack nucleation life distribution. The proposed spur gear fatigue model is used to simulate the contacts of gear pairs having different surface roughness amplitudes. The predictions are compared to the measured gear fatigue Stress-Life data for each surface condition to assess the model accuracy in predicting the crack nucleation fatigue lives as well as the location of the critical failure sites.
Multiple Limit Cycles in Laser Interference Transduced Resonators
Authors: Blocher David B. , Rand Richard H. , Zehnder Alan T.
Published: June 2012

Nanoscale resonators whose motion is measured through laser interferometry are known to exhibit stable limit cycle motion. Motion of the resonator through the interference field modulates the amount of light absorbed by the resonator and hence the temperature field within it. The resulting coupling of motion and thermal stresses can lead to self oscillation, i.e. a limit cycle. In this work the coexistence of multiple stable limit cycles is demonstrated in an analytic model. Numerical continuation and direct numerical integration are used to study the structure of the solutions to the model. The effect of damping is discussed as well as the properties that would be necessary for physical devices to exhibit this behavior.
Electrical Discharge Machining of Micro Holes on Titanium Sheets
Authors: D’Urso Gianluca , Longo Michela , Maccarini Giancarlo , Ravasio Chiara
Published: June 2012

Micro-Electrical Discharge Machining (μEDM) has become a widely accepted non-traditional material removal process for micro-manufacture of conductive materials considered difficult to be cut using traditional machining technologies. Moreover, EDM is an ideal process for obtaining burr-free micron-size apertures with high aspect ratios. Aim of this work was to investigate the feasibility of drilling micro holes on titanium using μ-EDM technology. Titanium plates having a thickness equal to 0.5 mm were taken into account and the holes were performed using a carbide electrode having a diameter equal to 0.3 mm. The Design Of Experiment (DOE) method was used for planning the experimental campaign and ANOVA techniques were applied to study the relationship between process parameters and final output. In particular, the most important process parameters such as peak current, pulse duration, frequency and electrode rotation speed were investigated as a function of material removal rate, wear rate and machining accuracy. Geometrical and dimensional analyses were carried out on micro-holes using both optical and scanning electron microscopes to evaluate both the over cut and the rate of taper.
Sustainable Manufacturing System Focusing on the Natural Growth of Bamboo: Life Cycle Assessment of Binder-Free Composites Made From Bamboo Fibers Extracted With a Machining Center
Authors: Ogawa Keiji , Hirogaki Toshiki , Aoyama Eiichi , Takagi Yota , Ogawa Sachiko
Published: June 2012

Bamboo is a natural resource widely distributed in Southeast Asia, including Japan. It has drawn attention as a sustainable and environmentally safe material because it is renewable and has a quick growth rate. Bamboo fiber also has high specific strength and stiffness. A self-bonding fiberboard using high-quality bamboo fiber extracted with a machining center has been fabricated by hot press forming. Therefore, a sustainable manufacturing system that focuses on bamboo is proposed. This paper describes the environmental burdens of this system, which are evaluated quantitatively using life cycle assessment (LCA).
Improvement of the Calculation of Hydrodynamic Systems by Considering the Dynamic Deformation Caused by Vibration
Authors: Kukla Sebastian , Sadek Tim
Published: June 2012

In order to improve the calculation of stiffness and damping coefficients (SDC) for hydrodynamic systems, this paper proposes the consideration of both static and dynamic deformations of the running surface. Dynamic deformations are caused by rotor vibration and corresponding unbalanced forces. A lubrication wedge was used to exemplify the significant influence of these dynamic deformations in SDC calculations. This basic hydrodynamic system was calculated considering material elasticity. First of all, an influence coefficient matrix, which describes the correlation of pressure and deformation, was calculated with the finite element program ANSYS. Using this matrix, small dynamic deformations of the running surface were considered in solving the Reynolds equation for the lubrication wedge. The analysis of the vibration response of this basic hydrodynamic system considering elastic material deformation demonstrated that both static and dynamic components of deflection significantly affect the SDC. These coefficients were also proved to be highly dependent on the stimulation frequency.
Coupling Between Dynamic Behavior and Contact Fatigue in Spur Gears
Authors: Osman T. , Velex P.
Published: June 2012

The main objective of the paper is to study the possible interactions between contact fatigue and dynamic tooth loads on gears. A specific 3D dynamic gear model is combined to contact fatigue models accounting for crack initiation and propagation. The numerical findings compare well with the experimental evidence from a back-to-back test rig. Five characteristic points on a tooth profile are analyzed and it is shown that contact fatigue on spur gears clearly depends on dynamic phenomena. Finally, the introduction of profile relief is discussed and its positive influence on the risk of failures at engagement is emphasized.
Influence of Damping on the Vibration of an Inclined Cable Subjected to Support Excitation
Authors: Tzanov Vassil , Neild Simon , Krauskopf Bernd , Wagg David
Published: June 2012

The cables used in cable-stayed bridges are known to have low levels of damping and, as a result, their large amplitude vibrations represent a problem for the structure. Therefore, augmenting the natural damping of cables is used as a strategy to decrease their vibration response. Here we investigate how this precaution changes the dynamics of the cable vibration response. We use a four-mode model of an inclined cable specifically, that is fixed at the top, and vertically excited at the base in order to simulate excitation due to the deck motion. This model simulates the internal resonances between in-plane and out-of-plane modes of vibration. The deck motion is taken to be at a frequency close to the natural frequency of the second cable mode in each plane, hence, directly exciting just the second in-plane mode. The objective of this study is to examine how the regions of stability (of the different possible solutions) change with variations in the modal damping value of the cable. The damping ratios of the cables used for bridges being considered is usually about 0.2%; here we investigate increasing ξ up to 1%. Three-parameter analysis shows that 2:1 resonance occurs for damping ratios larger than 0.6%; but it requires higher excitation amplitudes than for damping ratios about 0.2%. The analysis of the damping ratio variation shows us that bifurcations that can lead to sudden change in the cable dynamics still persist for the parameter ranges considered in this study. However, they occur at excitation frequencies that are further from the second natural frequency of the cable.
Tracing the Envelope of the Objective-Space in Multi-Objective Topology Optimization
Authors: Turevsky Inna , Suresh Krishnan
Published: June 2012

In multi-objective problems, one is often interested in generating the envelope of the objective-space, where the envelope is, in general, a superset of pareto-optimal solutions. In this paper, we propose a method for tracing the envelope of multi-objective topology optimization problems, and generating the corresponding topologies. The proposed method exploits the concept of topological sensitivity, and is applied to bi-objective optimization, namely eigenvalue-volume, eigenvalue-eigenvalue and compliance-eigenvalue problems. The robustness and efficiency of the method is illustrated through numerical examples.
Synthesis of a Variable Displacement Linkage for a Hydraulic Transformer
Authors: Wilhelm Shawn R. , Van de Ven James D.
Published: June 2012

A hydraulic pump/motor with high efficiency at low displacements is required for a compressed air energy storage system that utilizes a liquid piston for near-isothermal compression. To meet this requirement, a variable displacement six-bar crank-rocker-slider mechanism, which goes to zero displacement with a constant top dead center position, has been designed. The synthesis technique presented in the paper develops the range of motion for the base four-bar crank-rocker, creates a method of synthesizing the output slider dyad, and analyzes the mechanisms performance in terms of transmission angles, slider stroke, mechanism footprint, and timing ratio. It is shown that slider transmission angles can be kept above 60 degrees and the base four-bar transmission angles can be controlled in order to improve overall efficiency. This synthesis procedure constructs a crank-rocker-slider mechanism for a variable displacement pump/motor that can be efficient throughout all displacements.
Benchmarking Bicycle and Motorcycle Equations of Motion
Authors: Dressel Andrew E. , Rahman Adeeb
Published: June 2012

In 2007, Meijaard, et al. [1] presented the canonical linearized equations of motion for the Whipple bicycle model along with test cases for checking alternative formulations of the equations of motion or alternative numerical solutions. This paper describes benchmarking three other implementations of bike equations of motion: the linearized equations for bicycles written by Papadopoulos and Schwab [2] in JBike6, the non-linear equations for bicycles outlined by Schwab [3] and implemented in MATLAB as a Cornell University class project, and the non-linear equations for motorcycles implemented in FastBike from the Motorcycle Dynamics Research Group at the University of Padua. [4] Some implementations are easier to benchmark than others. For example, JBike6 is designed to produce eigenvalues and easily exposes the coefficients of its linearized equations of motion. At the other extreme, the class project non-linear equations were not originally intended to generate eigenvalues and are implemented in a single 48×48 matrix. Finally, while FastBike does generate eigenvalues, its equations of motion incorporate tire and frame compliance, which cannot be completely disabled. Instead, the tire stiffness parameters must be increased, but not so much as to cause convergence errors in FastBike. In the end, all three implementations generate eigenvalues that match the published benchmark values to varying degrees. JBike6 comes the closest, with agreement of 12 digits or more. The class project is second, with agreement of 12 digits for most forward speeds, but with a loss of measurable agreement near the capsize speed due to a peak in the eigenvalue condition number. Unfortunately, FastBike is limited at this time to exporting eigenvalues with no more than two decimal places, and so agreement can only be found to ±0.005.
Synchronization of Mechanical Oscillators: An Experimental Study
Authors: Daneshvar Roozbeh , Kalma´r-Nagy Tama´s
Published: June 2012

In this paper we investigate synchronization of oscillators. We use mechanical metronomes that are coupled through a mechanical medium. In passive coupling of two oscillators, the coupling medium is a one degree of freedom passive mechanical basis. The analysis of the system is shown and supported by simulations of the proposed model and experimental results. We show how the oscillators synchronize and discuss the affecting parameters in synchronization. In another case, the oscillators are forced by an external input while that input is also affected by the oscillators. This feedback loop introduces dynamics to the whole system. For this case, we place the mechanical metronomes on a one degree of freedom moving base. The movements of the base are a function of a feedback from the phases of the metronomes. We study the space of possibilities for the movements of the base and consider impacts of the base movement on the synchronization of metronomes. We also show how such a system evolves in time when we introduce an adjusting parameter that changes over time and updates based on feedbacks from the system.
Periodic Solutions and Their Regions of Attraction for Flexible Structures Under Relay Feedback Control With Nonlinear Control Law
Authors: Borre Michael , Flashner Henryk
Published: June 2012

A method for calculating all periodic solutions and their domains of attraction for flexible systems under nonlinear feedback control is presented. The systems considered consist of mechanical systems with many flexible modes and a relay type controller coupled with a nonlinear control law operating in a feedback configuration. The proposed approach includes three steps. First, limit cycle frequencies and periodic fixed points are computed exactly, using a block diagonal state-space modal representation of the plant dynamics. Then the relay switching surface is chosen as the Poincare mapping surface and is discretized using the cell mapping method. Finally, the region of attraction for each limit cycle is computed using the cell mapping algorithm and employing an error based convergence criterion. An example consisting of a system with two modes, a relay with dead-zone and hysteresis, and a nonlinear control law with a signed velocity squared term is used to demonstrate the proposed approach.