bluuebunny/crossref_metadata_2025 huggingface dataset:
Provision of orthodontic care to adolescents in South Australia: The type, the provider, and the place of treatment
Authors: Allister J. H. , Spencer A. J. , Brennan D. S.
Published: May 2009

There are many pathways involving different providers and locations that individuals may take in obtaining orthodontic services. The aim of this study was to document the provision of orthodontic services and establish the pathways taken toward fixed orthodontic treatment by adolescents in South Australia. Data were collected on the use of orthodontic services by a cohort of adolescents enrolled in the School Dental Service at age 13 years and again at age 15 years. By age 15 years, 83.2 per cent of the adolescents had received orthodontic consultations, 27.3 per cent had received fixed orthodontic treatment and 41.4 per cent had received other forms of orthodontic treatment (extractions, space retainers or removable appliances). The majority of fixed orthodontic treatment was supplied by orthodontists in the private sector, while extractions and removable appliances were provided mainly by public sector general dentists. Most individuals used services in both the public and private sectors and the most frequent pathway taken by the adolescents receiving fixed orthodontic treatment involved consultation in both the public and private sectors, non‐fixed orthodontic treatment in the public sector and fixed orthodontic treatment in the private sector. The findings indicate wide access to orthodontic consultation and a high uptake of fixed orthodontic treatment once the adolescent sought private sector orthodontic consultation. Orthodontic care was seen to be an interactive process between public sector general dentists and private sector orthodontists.
Data-Dimensionality Reduction Using Information-Theoretic Stepwise Feature Selector
Authors: Joshi Alok A. , Meckl Peter , King Galen , Jennings Kristofer
Published: May 2009

A novel information-theoretic stepwise feature selector (ITSFS) is designed to reduce the dimension of diesel engine data. This data consist of 43 sensor measurements acquired from diesel engines that are either in a healthy state or in one of seven different fault states. Using ITSFS, the minimum number of sensors from a pool of 43 sensors is selected so that eight states of the engine can be classified with reasonable accuracy. Various classifiers are trained and tested for fault classification accuracy using the field data before and after dimension reduction by ITSFS. The process of dimension reduction and classification is repeated using other existing dimension reduction techniques such as simulated annealing and regression subset selection. The classification accuracies from these techniques are compared with those obtained by data reduced by the proposed feature selector.
Assessment of Charge-Air Cooler Health in Diesel Engines Using Nonlinear Time Series Analysis of Intake Manifold Temperature
Authors: Joshi Alok A. , James Scott , Meckl Peter , King Galen , Jennings Kristofer
Published: May 2009

Degradation in the cooling effectiveness of a charge-air cooler (CAC) in a medium-duty turbocharged diesel engine has significant impact on engine performance. This degradation lowers the boost pressure and raises the intake manifold temperature. As a result, the engine provides lower horsepower and higher hydrocarbon levels than the rated values. The objective of this research is to monitor the health of the charge-air cooler by analyzing the intake manifold temperature signal. Experiments were performed on a Cummins ISB series turbocharged diesel engine, a 6-cylinder inline configuration with a 5.9 l displacement volume. Air flowing over the cooler was blocked by varying amounts, while various engine temperatures and pressures were monitored at different torque-speed conditions. Similarly, data were acquired without the introduction of any fault in the engine. For the construction of the manifold temperature trajectory vector, average mutual information estimates and a global false nearest neighbor analysis were used to find the optimal time parameter and embedding dimensions, respectively. The prediction of the healthy temperature vector was done by local linear regression using torque, speed, and their interaction as exogenous variables. Analysis of residuals generated by comparing the predicted healthy temperature vector and the observed temperature vector was successful in detecting the degradation of the charge-air cooler. This degradation was quantified by using box plots and probability density functions of residuals generated by comparing intake manifold temperature of healthy and faulty charge-air coolers. The general applicability of the model was demonstrated by successfully diagnosing a fault in the exhaust gas recirculation cooler of a different engine.
Experimental Implementation of a Hybrid Nonlinear Control Design for Magnetostrictive Actuators
Authors: Oates William S. , Evans Phillip G. , Smith Ralph C. , Dapino Marcelo J.
Published: May 2009

A hybrid nonlinear optimal control design is experimentally implemented on a magnetostrictive Terfenol-D actuator to illustrate enhanced tracking control at relatively high speed. The control design employs a homogenized energy model to quantify rate-dependent nonlinear and hysteretic ferromagnetic switching behavior. The homogenized energy model is incorporated into a finite-dimensional nonlinear optimal control design to directly compensate for the nonlinear and hysteretic magnetostrictive constitutive behavior of the Terfenol-D actuator. Additionally, robustness to operating uncertainties is addressed by incorporating proportional-integral (PI) perturbation feedback around the optimal open loop response. Experimental results illustrate significant improvements in tracking control in comparison to PI control. Accurate displacement tracking is achieved for sinusoidal reference displacements at frequencies up to 1 kHz using the hybrid nonlinear control design, whereas tracking errors become significant for the PI controller for frequencies equal to or greater than 500 Hz.
A Closed-Form Full-State Feedback Controller for Stabilization of 3D Magnetohydrodynamic Channel Flow
Authors: Vazquez Rafael , Schuster Eugenio , Krstic Miroslav
Published: May 2009

We present a boundary feedback law that stabilizes the velocity, pressure, and electromagnetic fields in a magnetohydrodynamic (MHD) channel flow. The MHD channel flow, also known as Hartmann flow, is a benchmark for applications such as cooling, hypersonic flight, and propulsion. It involves an electrically conducting fluid moving between parallel plates in the presence of an externally imposed transverse magnetic field. The system is described by the inductionless MHD equations, a combination of the Navier–Stokes equations and a Poisson equation for the electric potential under the MHD approximation in a low magnetic Reynolds number regime. This model is unstable for large Reynolds numbers and is stabilized by actuation of velocity and the electric potential at only one of the walls. The backstepping method for stabilization of parabolic partial differential equations (PDEs) is applied to the velocity field system written in appropriate coordinates. Control gains are computed by solving a set of linear hyperbolic PDEs. Stabilization of nondiscretized 3D MHD channel flow has so far been an open problem.
Elimination of Bias Errors Due to Suspension Effects in FRF-Based Rigid Body Property Identification
Authors: Kloepper Robert , Okuma Masaaki
Published: May 2009

The prediction of a mechanical structure’s rigid dynamic behavior requires knowledge of ten inertia parameters. In cases where no accurate models of the structure’s geometry and mass distribution are available, the ten inertia parameters must be determined experimentally. Experimental methods based on measurements of frequency response functions (FRFs) are subject to bias errors due to suspension effects. This paper proposes a method for eliminating these errors by using a single-wire suspension condition and modeling the suspension’s effect on the FRFs. The suspension model depends only on the unknown rigid body properties and on three easy-to-measure parameters. The rigid body properties are determined by fitting FRFs derived from the suspension model and from the rigid body mass matrix directly to the experimental FRF data. Eliminating the suspension bias makes it possible to use low-frequency FRF data, which in turn justifies the assumption of rigid behavior. In this way, bias-free rigid body property identification can be achieved without modal curve fitting. Simulation and experimental results are presented showing the effectiveness of the approach.
A Fuzzy Method for Propagating Functional Architecture Constraints to Physical Architecture
Authors: Bonjour Eric , Deniaud Samuel , Dulmet Maryvonne , Harmel Ghassen
Published: May 2009

Modular product design has received great attention for about 10 years, but few works have proposed tools to either jointly design the functional and physical architectures or propagate the impact of evolutions from one domain to another. In this paper, we present a new method supporting the product architecture design. In new product development situations or in re-engineering projects, system architects could use this method in the early design stages to predetermine cohesive modules and integrative elements and to simulate a domain architecture by propagating architecture choices from another domain. To illustrate our approach, we present an industrial case study concerning the design of a new automobile powertrain.
Reliability Based Design Optimization of MEMS Considering Pull-In
Authors: Raulli Michael , Maute Kurt
Published: May 2009

The increased use of micro-electro-mechanical systems (MEMS) as key components for actuation and sensing purposes in novel devices and systems emphasizes the need for optimal design methods. Stochastic variations in manufacturing and operational conditions must be considered in order to meet performance goals. This study proposes a reliability based design optimization methodology for the design of geometrically complex electrostatically actuated MEMS. The first order reliability method is used for reliability analysis of fully-coupled electrostatic-mechanical problems. A general methodology for predicting the instability phenomenon of pull-in and incorporating it into an automatic optimization process is proposed and verified with analytical and experimental results. The potential of this methodology is illustrated with the design of an analog micromirror.
Model-Independent Control of a Flexible-Joint Robot Manipulator
Authors: Chatlatanagulchai Withit , Meckl Peter H.
Published: May 2009

Flexibility at the joint of a manipulator is an intrinsic property. Even “rigid-joint” robots, in fact, possess a certain amount of flexibility. Previous experiments confirmed that joint flexibility should be explicitly included in the model when designing a high-performance controller for a manipulator because the flexibility, if not dealt with, can excite system natural frequencies and cause severe damage. However, control design for a flexible-joint robot manipulator is still an open problem. Besides being described by a complicated system model for which the passivity property does not hold, the manipulator is also underactuated, that is, the control input does not drive the link directly, but through the flexible dynamics. Our work offers another possible solution to this open problem. We use three-layer neural networks to represent the system model. Their weights are adapted in real time and from scratch, which means we do not need the mathematical model of the robot in our control algorithm. All uncertainties are handled by variable-structure control. Backstepping structure allows input efforts to be applied to each subsystem where they are needed. Control laws to adjust all adjustable parameters are devised using Lyapunov’s second method to ensure that error trajectories are globally uniformly ultimately bounded. We present two state-feedback schemes: first, when neural networks are used to represent the unknown plant, and second, when neural networks are used to represent the unknown parts of the control laws. In the former case, we also design an observer to enable us to design a control law using only output signals—the link positions. We use simulations to compare our algorithms with some other well-known techniques. We use experiments to demonstrate the practicality of our algorithms.
Designing Nonlinear Zero Dynamics to Reject Periodic Waveforms
Authors: Paden Brad E. , Mirnateghi Nasim , Gentili Luca , Marconi Lorenzo
Published: May 2009

In linear systems, designers use zeros for loop-shaping and the attenuation of disturbances. For example, imaginary-axis zeros can be used to reject sinusoids at a specific frequency such as a 50 Hz or 60 Hz power line interference. If the disturbance is nonsinusoidal, repetitive control methods may be used but additional controller states for each harmonic are required. Thus, rejecting periodic disturbance that are nonsinusoidal with low controller order remains an open problem. In this paper, we constructively design low-order nonlinear dynamics that reject a nonsinusoidal disturbance. We identify a particular case of the nonlinear regulator theory wherein the Byrnes–Isidori PDE has a simple solution. This case leads to a constructive procedure for designing nonlinear zero dynamics in systems with input disturbances. The constructive procedure is accessible to designers who do not have experience with the nonlinear geometric control theory.
Pulsed Control of Thermoacoustic Instabilities: Analysis and Experiment
Authors: Carson J. Matthew , Baumann William T. , Saunders William R.
Published: May 2009

Thermoacoustic instabilities in combustors have been suppressed using phase-shift algorithms pulsing an on-off actuator at the limit cycle frequency (flc) or at the subharmonics of flc. It has been suggested that control at a subharmonic rate may extend the actuator lifetime and possibly require less actuator bandwidth. This paper examines the mechanism of subharmonic control in order to clarify the principles of operation and subsequently identify potential advantages for combustion control. Theoretical and experimental arguments show that there must be a Fourier component of the subharmonic control signal at flc in order to stabilize the limit cycling behavior. It is also demonstrated that the magnitude of that Fourier component must be equivalent to the signal magnitude for a linear phase-shift controller that operates directly at flc. The concept of variable-subharmonic control is introduced whereby the actuator is pulsed at the instability frequency to initially stabilize the system and then is pulsed at a subharmonic frequency to maintain stability. These results imply that an actuator used for subharmonic control cannot be effective unless its bandwidth spans the instability frequency. The advantage of reduced cycling may still be realized but will require higher control authority to produce the same effect as an actuator pulsed at the instability frequency.
A Real-Time Computational Learning Model for Sequential Decision-Making Problems Under Uncertainty
Authors: Malikopoulos Andreas A. , Papalambros Panos Y. , Assanis Dennis N.
Published: May 2009

Modeling dynamic systems incurring stochastic disturbances for deriving a control policy is a ubiquitous task in engineering. However, in some instances obtaining a model of a system may be impractical or impossible. Alternative approaches have been developed using a simulation-based stochastic framework, in which the system interacts with its environment in real time and obtains information that can be processed to produce an optimal control policy. In this context, the problem of developing a policy for controlling the system’s behavior is formulated as a sequential decision-making problem under uncertainty. This paper considers the problem of deriving a control policy for a dynamic system with unknown dynamics in real time, formulated as a sequential decision-making under uncertainty. The evolution of the system is modeled as a controlled Markov chain. A new state-space representation model and a learning mechanism are proposed that can be used to improve system performance over time. The major difference between the existing methods and the proposed learning model is that the latter utilizes an evaluation function, which considers the expected cost that can be achieved by state transitions forward in time. The model allows decision-making based on gradually enhanced knowledge of system response as it transitions from one state to another, in conjunction with actions taken at each state. The proposed model is demonstrated on the single cart-pole balancing problem and a vehicle cruise-control problem.
Convergence Properties of a Computational Learning Model for Unknown Markov Chains
Authors: Malikopoulos Andreas A.
Published: May 2009

The increasing complexity of engineering systems has motivated continuing research on computational learning methods toward making autonomous intelligent systems that can learn how to improve their performance over time while interacting with their environment. These systems need not only to sense their environment, but also to integrate information from the environment into all decision-makings. The evolution of such systems is modeled as an unknown controlled Markov chain. In a previous research, the predictive optimal decision-making (POD) model was developed, aiming to learn in real time the unknown transition probabilities and associated costs over a varying finite time horizon. In this paper, the convergence of the POD to the stationary distribution of a Markov chain is proven, thus establishing the POD as a robust model for making autonomous intelligent systems. This paper provides the conditions that the POD can be valid, and be an interpretation of its underlying structure.
Practical Implementation of Robust Design Assisted by Response Surface Approximation and Visual Data-Mining
Authors: Shimoyama Koji , Lim Jin Ne , Jeong Shinkyu , Obayashi Shigeru , Koishi Masataka
Published: May 2009

A new approach for multi-objective robust design optimization was proposed and applied to a practical design problem with a large number of objective functions. The present approach is assisted by response surface approximation and visual data-mining, and resulted in two major gains regarding computational time and data interpretation. The Kriging model for response surface approximation can markedly reduce the computational time for predictions of robustness. In addition, the use of self-organizing maps as a data-mining technique allows visualization of complicated design information between optimality and robustness in a comprehensible two-dimensional form. Therefore, the extraction and interpretation of trade-off relationships between optimality and robustness of design, and also the location of sweet spots in the design space, can be performed in a comprehensive manner.
A Novel Principle for Automatic Transmission
Authors: Hong Shane Y.
Published: May 2009

This paper unveils a new principle for automatic transmission, which may greatly simplify the current automatic transmissions and improve their efficiency. Unlike traditional automatic transmission based on torque converter/planetary gears, automatic transmission systems based on V-belt variable speed drive, or traditional transmission with electrical control, this new approach does not rely on the gear ratio or radii of the driving and driven wheel to change the speed ratio. The speed change in the new approach is achieved by an elastic belt on two fixed-diameter pulleys. The belt elongates in proportion to the load applied, and the driving pulley of fixed diameter has to rotate more to accommodate the increased length of the belt due to the load increase, consequently reduces the speed of driven pulley. This self-sensing, self-adjusting, and fully automatic drive system is pure mechanical without the need of electrical or hydraulic control. Based on this novel kinematic principle, the simplest automatic transmission in the world may be designed, manufactured, and used.
Lapping and Superfinishing Effects on Hypoid Gears Surface Finish and Transmission Errors
Authors: Masseth Jack , Kolivand Mohsen
Published: May 2009

There are several geometric and working parameters, besides offset, that have minor effects on hypoid gears efficiency (i.e. spiral angle, pressure angle, lubricant type & temperature, surface finish, etc.). Some theoretical analyses of mechanical efficiency of hypoid gears show that surface finish has considerable effect on hypoid gear efficiency. This is due to a high sliding to rolling ratio in these types of gears. In this paper, a study on measuring of surface finish of both ring gear and pinion will be presented. Moreover, the effects of lapping and superfinishing on surface finish will be discussed. Using an accurate form-measuring machine, surface finish measurements were done on several experimentally produced hypoid gear pairs. Despite the fact that lapping is expected to improve the surface finish, measurement results show that ring gear’s surface finish becomes worse (roughness increased) after lapping while no consistent results for pinion surface finish were observed. However, it will be shown that lapping decreases transmission errors for both sides (drive and coast). Utilizing a Gleason single flank tester (SFT) 600HTT it will be shown experimentally that transmission errors up to the second harmonics for both sides will be decreased. In addition, it can be seen that lapping decreases surface finish variation among gear sets. As an expansion of the previous study [1] by the authors on lapping effects on surface finish and transmission errors, this paper will also present the effects of the superfinishing process on hypoid gears surface finish and transmission errors. This study shows the result of measurements taken before and after superfinishing, although superfinishing improves surface finish drastically it will be shown that surface finish quality will be decreased when gear sets are rolled together.
Reduction of Sensitivity of Spiral Bevel Gears to Misalignments by the Use of Appropriate Machine Tool Settings
Authors: Simon Vilmos V.
Published: May 2009

The method for loaded tooth contact analysis is applied for the investigation of the combined influence of machine tool settings for pinion teeth finishing and misalignments of the mating members on load distribution and transmission errors in mismatched spiral bevel gears. By using the corresponding computer program the influence of pinion’s offset and axial adjustment error, angular position error of the pinion axis, tooth spacing error, and machine tool setting variation for pinion teeth finishing, on tooth contact pressure, tooth root stresses and angular displacement of the driven gear member from the theoretically exact position based on the ratio of the numbers of teeth is investigated. The obtained results show that by the use of appropriate machine tool settings the influence of misalignments and tooth errors on maximum tooth contact pressure and transmission errors can be significantly reduced.
On the Generation of Analytical Noncircular Multi-Lobe Internal Pitch Pairs
Authors: Yan Jia , Yang Daniel C. H. , Tong Shih-Hsi
Published: May 2009

A method for the design of general analytical noncircular multi-lobe internal pitch pairs is presented. The method is based on a reshaping algorithm. A selected monotonic function can be assigned as the initial profile for the outer rotor of the designed pitch pair. This initial function will then be reshaped to satisfy that the number of lobes must be an integer. This final pitch function can then be obtained analytically. To archive smooth profile design, the C1 continuous conditions on pitch rotors are established. A dimensionless parameter geometrically interpreted as the noncircularity of pitch rotor is introduced for the systematic design of pitch pairs. Results from this research have applications to the design of noncircular gears.
Automatic Determination of Transmission Powerflow Mechanizability Using Graph Theory
Authors: Bucknor Norman K.
Published: May 2009

A methodology has been developed to automatically generate planetary geartrain topologies based on criteria such as the number of desired speed ratios and the number of torque transmitting mechanisms [1]. This paper describes an algorithm and computer code for automatically determining the mechanizability of the candidate geartrains. The mathematical description of each topology is interpreted as a graph, a collection of vertices and connecting edges, which can then be tested for planarity using graph-processing algorithms. A planar graph implies mechanizability. Using another algorithm based on graph theory, the computer code also detects and eliminates duplicate designs that may be hard to detect via visual inspection. The computer program significantly reduces the time needed to manually process design data sets by eliminating those design candidates that are infeasible.
Evaluation of Tooth Contact Stress With Tooth Flank Film Elements (Comparison of Evaluation With Measurement)
Authors: Moriwaki Ichiro , Tani Tomohito , Miyata Toshiro , Ueda Akio , Yoshihara Masayoshi
Published: May 2009

A new finite element analysis for meshing gear pair has been developed with a new element called “tooth flank film element.” The new element is a phantom element put on a tooth flank without any thickness, and enables boundary conditions for a contact problem in meshing teeth to be easily dealt with. In the present paper, contact stresses between tooth flanks of mating gear pair calculated with the proposed finite element method are compared with stresses measured with pressure measurement films. As a result, the proposed method was confirmed to be useful for evaluation of contact stress.
Comprehensive Study on Controllability of a Large-Scale MR Shock Absorber Under High Impact Load
Authors: Li Yancheng , Wang Jiong , Hu Hongsheng
Published: May 2009

The primary purpose of this study is to provide a comprehensive understanding on the controllability of a large-scale single-ended Magnetorheological (MR) shock absorber under impact load. Performances of MR shock absorber under random load, mainly in the transportation applications, seismic protection in civil engineering and wind-rain-induced load in Cable Bridge, are well investigated by many researchers. However, little research has been focused on the dynamic performance of MR shock absorber under impact load. Furthermore, the controllability of large-scale MR shock absorber under impact load is not researched in detail. In this paper, a test rig which uses a closed bump to produce an impact load is developed. A novel large-scale single-ended MR shock absorber without the accumulator is used as the specimen. To evaluate the controllability of MR shock absorber under impact load, several different currents are applied to the MR shock absorber. Moreover, an on-off control strategy is applied to the electromagnetic coil to investigate the dynamics of this shock absorber under impact load. It is indicated that this large-scale single-ended MR shock absorber has a good controllability compared with small double-ended MR shock absorber.
Efficient Treatment of Gyroscopic Bodies in the Recursive Solution of Multibody Dynamics Equations
Authors: Tong Martin M.
Published: May 2009

This paper presents an efficient treatment of gyroscopic bodies in the recursive solution of the dynamics of an N-body system. The bodies of interest are the reaction wheels in satellites, wheels on a car, propellers on a helicopter and flywheels in machines. Each such body spins about one of its principal axes and around its center of mass. Current recursive solution methods treat all bodies in the system identically. The proposition here is that a body with gyroscopic children can be collectively treated as a composite body in the recursive solution process. It will be shown that this proposition improves the recursive solution speed to the order O(N-m) where m is the number of gyroscopic bodies in the system. A satellite with three reaction wheels is used to illustrate the proposition.
Optimal Construction of a Hydraulic Pump With Elliptic Rotated Piston by Kakeya-Besicovitch Application
Authors: Ungur Petru , Pop Petru A. , Gordan Mircea , Muresan Nicodim
Published: May 2009

The paper has presented an application of Kakeya-Besicovitch, third example about commutation of finite element beam endpoints inside of arbitrary small zone. This area is a hypocycloid with three cusped points at that inner tangent has a constant length independent by the point position of its inner tangent, which being rotated in clock-way it’s came back to its original position with its endpoints reversed. The application is a hydraulic pump compound by one rotated piston with elliptical section which is rolling in a fixed chamber with hypocycloid form and three cusped rounded tips after a curvature equal with major axe ellipse endpoints curvatures. The rolling motion is imposed by eccentric exterior source that acting inside of cylindrical pocket located in the center of elliptic piston, which divided the hypocycloid in three equal parts at 120° from each other. The pump could be working as a hydraulic motor which is endowed with rotating distributor that can feed each chamber with variable volume one by one due to moving the piston. The pump’s relevance is given by its efficiency, allowing a large flow capacity to a lower spindle speed, ensured a constant ratio spindle speed which working silence and a large stability.
Fatigue Failure Mechanism of CVT Rubber Belts
Authors: Iizuka Hiroshi , Yamashita Jun , Tokuda Akihiko
Published: May 2009

The fatigue failure mechanism was investigated for the rubber CVT (continuously variable transmission) belts. There are three major crack initiation modes in the rubber CVT belts, namely the adhesive rubber crack, the backing rubber crack and the bottomland crack. Especially, the mode of the adhesive rubber crack is important to strengthen the rubber CVT belts, because the crack is the most difficult to find out during the driving. In this study, the failure morphology of the damaged belts was observed using an optical microscope and a X-ray CT scan after some fatigue tests. Moreover, the failure mechanism of the adhesive rubber crack was discussed basing on the FEM and simplified mechanical analyses. The fatigue damage was accumulated along the interface between the cog rubber and the adhesive rubber. The interface was de-bonded by the shearing strain, which was induced by the dishing deformation of the belt within the pulley groove.
Residual Stress and Bending Fatigue Strength of Case-Carburized Thin-Rimmed Spur Gears With Asymmetric Web Arrangement
Authors: Miyachika Kouitsu , Xue Wei-Dong , Koide Takao , Mada Hidefumi , Nojima Kengo , Oda Satoshi , Katanuma Hideaki
Published: May 2009

This paper presents a study on effects of carburized parts on residual stress and bending fatigue strength of case-carburized thin-rimmed spur gears with asymmetric web arrangement. A heat conduction analysis and an elastic-plastic stress analysis for the case-carburizing process of thin-rimmed spur gears with asymmetric web arrangement were carried out by the three-dimensional finite-element method (3D-FEM), and then residual stresses were obtained. Effects of the case depth, the carburized part and the rim thickness on the residual stress of case-carburized thin-rimmed spur gears were determined. Bending fatigue tests were carried out for case-carburized thin-rimmed spur gears with asymmetric web arrangement, and S-N curves and bending fatigue limit loads were obtained. Effects of the case-depth, the carburized part and the rim thickness on the bending fatigue strength of the case-carburized thin-rimmed spur gear with asymmetric web arrangement were determined.
Synthesis of Hypoid Gear Surface Topography by a Nonlinear Least Squares Approach
Authors: Artoni A. , Gabiccini M. , Guiggiani M.
Published: May 2009

This paper outlines a systematic methodology for finding the machine setting corrections required to obtain a predesigned ease-off surface in spiral bevel and hypoid gear teeth. The problem is given a nonlinear least squares formulation which, however, is highly prone to numerical instabilities. The Levenberg–Marquardt algorithm with a trust region strategy turned out to be quite effective and robust to obtain feasible solutions. The proposed method was tested on lengthwise crowning, profile crowning and spiral angle correction. In all cases, the goal was achieved with very high accuracy, in a few iterations and, remarkably, with different sets of machine parameters.
Accuracy of Straight Bevel Gear by End Mill Using CNC Milling Machine
Authors: Kawasaki Kazumasa , Shinma Kazuyoshi
Published: May 2009

Straight bevel gears are usually manufactured with various machines and systems, and the tooth profiles are produced by grinding or machining by means of a tool with many cutting edges. In recent years, the straight bevel gear has been manufactured by an end mill using a CNC milling machine because the use of the auxiliary apparatus, special cutters, and special machine tools are not needed. Using this method, the gear manufacturing with high accuracy is important problem. In this paper, the coordinate measurement of the straight bevel gear manufactured in this method is performed and the gear accuracy is evaluated. The tooth profiles of a straight bevel gear generated by a quasicomplementary crown gear instead of a conventional complementary crown gear is introduced. For this study, first the tooth profiles of the straight bevel gear were modeled using a 3D-CAD system and the gear was manufactured by an end mill using a CNC milling machine based on a CAM process. Afterward, the coordinates of many points on the gear tooth surfaces were measured at random using a coordinate measuring machine. This coordinate measurement provides the information about the factors relation to the gear accuracy such as pressure angle, tooth angle error, root cone angle, and apex to back and so on. Therefore, the values of the above factors were estimated and were compared with the theoretical ones, respectively.
Development of a Dynamometer to Study the Performance of Plastic Gears
Authors: Cassata Mike , Morris Martin , Abanto-Bueno Jorge
Published: May 2009

A testing facility has been developed to explore the failure modes of plastic gears. The overall goal is the prediction of gear tooth failure for a given set of operating conditions and to classify failure modes of plastic gears. The initial investigation is centered on the testing of plastic spur gears placed on a parallel-shaft drive train between a variable-speed, reversible DC motor and an eddy current dynamometer. The testing apparatus has been designed, fabricated, and refined to deliver consistent results. The dynamometer places two plastic spur gears in mesh, one being the drive gear and the other the driven. Most of the test gear pairs were injection molded, 40-tooth, 0.8 module gears. These gears were molded using Delrin™ 311DP, a polyoxymethylene polymer which is made by the DuPont Company. Optical encoders were attached to the input and output shafts to sense the shaft position providing a measurement of the deflection and wear of the gear teeth. In addition, an infrared temperature sensor was retrofitted to the dynamometer apparatus to measure the tooth-flank surface temperature. All of the tests where the gear flank temperature reached 250°F resulted in a catastrophic failure. The apparatus was also fitted with a high-speed digital camera system capable of sampling 1000 frames per second. The camera recorded the failure of the plastic gears.
Measurement of Tooth Pair Deflections With Ultra High Resolution Encoders and Prediction of Transmission Error Under Load in High Precision
Authors: Kurokawa Syuhei , Ariura Yasutsune
Published: May 2009

The purpose of this research is to predict transmission error under loading conditions in high accuracy. Transmission error is very important information in the evaluation of gear engagement and the prediction of vibration and noise from gear boxes. In some experiments, measurement of transmission error is sometimes performed to grasp an actual situation of gear static engagement. However, it is impossible to measure all of gear pairs in mass production for actual transmission manufacturers. The prediction of transmission error by the simulation in high accuracy should be powerful and effective means in application. The most important and indispensable information to simulate accurate transmission error under load is the deflection of a gear tooth and the displacement in tooth pair contact. One of conventional approaches is to predict bending deflections with FEM analysis. However it is very difficult to calculate the deflections in high accuracy by FEM because of less grid density, inadequate constraint conditions, the lack of information of actual loading conditions, and so on. To overcome the difficulty, the authors try to measure tooth pair deflections directly by experiments using a couple of ultra high precision encoders. The measurement strategy is to obtain the deflection of only single tooth pair during a whole period of tooth engagement. It can be achieved by use of a specially manufactured gear which has large and intentional pitch deviations. Experimental formulas of gear tooth pair deflections are derived from measured results. Putting assumption that tooth deflections with respect to applied loads can be expressed approximately as a curve of the second order, the stiffness of single-tooth engagement is evaluated. Transmission error is simulated with the obtained formula of the tooth stiffness and the result is compared with the measured transmission error and discussed.
Effects of Rolling on Load Bearing Capacity of Sintered Metal Gears
Authors: Koide Takao , Maemori Takatoshi , Takemasu Teruie , Miyachika Kouitsu , Namba Chiaki
Published: May 2009

This paper describes the effects of surface rolling on the load bearing capacity of sintered metal gears. Sintered metal gears and rollers were surface-rolled under various amounts of rolling. The effects of rolling on the surface properties were examined by measuring the porosities and hardness near the surfaces of the rolled gear teeth and rollers. Bending fatigue tests for the surface-rolled sintered metal gears and contact fatigue tests for the rollers were carried out. The effects of the amount of rolling on the load bearing capacity of sintered metal gears and rollers were determined, and these results were compared with the results for as-sintered and wrought steel gears and rollers.
Dynamic Interactions Between Sliding Friction and Tip Relief in Spur Gears
Authors: He Song , Singh Rajendra
Published: May 2009

The chief objective of this article is to examine dynamic interactions between sliding friction and profile modifications in a spur gear pair. First, a new computational method is proposed that incorporates the sliding friction and realistic time-varying stiffness into a multi-degree-of-freedom system model. Second, competing friction formulations, such as the Coulomb dry friction model and empirical expressions based on elasto-hydrodynamic and/or boundary lubrication regime principles, are briefly evaluated and validated by comparing friction force predictions with measurements. Third, effect of the profile modification on the dynamic transmission error is analytically examined under the influence of sliding friction. An out-of-phase relationship between the normal load and friction force is found to be critical as it could amplify motions or forces in the off-line-of-action direction. Typical tip relief schemes are examined including the perfect involute profile (baseline), short tip relief (at light load), intermediate tip relief (at medium load) and long tip relief (at peak load). Case studies are evaluated over a range of operating loads; interactions between sliding friction and profile modifications are observed. Finally, principles that could minimize dynamic transmission errors in the presence of sliding friction are introduced.
Analytical Study of Helical Gear Dynamics With Sliding Friction Using Floquet Theory
Authors: He Song , Singh Rajendra
Published: May 2009

Analytical models of a helical gear pair are developed in order to examine the effect of sliding friction on the dynamic transmission error. Simplified 6 degree-of-freedom and single degree-of-freedom analytical models are developed. These models characterize the contact plane dynamics and capture the velocity reversal at the pitch line due to sliding friction. By assuming a constant mesh stiffness density along the contact lines, a linear time-varying model (with parametric excitation) is obtained. The effect of sliding friction is quantified by an effective mesh stiffness term. Floquet theory is then used to obtain closed-form solutions to the dynamic transmission error given periodic piece-wise linear tooth stiffness function. Responses to both initial conditions and forcing function under a nominal torque are derived. Analytical models are validated by comparing predictions with numerical simulations. Finally, parametrically-induced instability issues are briefly mentioned.
Optimum Tooth-Surface Modification for Axis-Displaced Involute Helical Gear Drive With Parallel Axes
Authors: Matsuda Takashi , Sato Motohiro , Matsui Satoshi
Published: May 2009

Gear drives, which have larger misalignment than the maximum tolerance of misalignment for gear drives with parallel axes in the Standard of Japanese Gear Manufacture’s Association (JGMA Standard 114-02), are designated as axis-displaced gear drives in this study. So, axis-displacement is used in place of the misalignment. And tooth-surface modification for axis-displaced gear drives has been studied by the authors. In this study, design system for optimum tooth-surface modification is developed for axis-displaced involute helical gear drives, which are sensitive to gear misalignment, to reduce the sensitivity to misalignment and to provide the high productivity and reliability. The system is composed of; (1) Virtual rack, which is conjugate to mating standard helical gear pair in their standard relative motion, is defined for pinion and gear tooth-surface generation. And axis-displacement is relative displacement between the virtual rack and each gear, or between pinion and gear. (2) Axis-displaced tooth-surface of each gear is defined as the envelope of virtual rack tooth-surface family in their regular motion transmission (zero transmission error) under an axis-displacement. (3) Basic tooth-surface of each gear is built by combining the axis-displaced tooth-surfaces under various axis-displacements. (4) Basic rack tooth-surface for each gear is obtained as the envelope of the basic tooth-surface family in their regular relative motion. (5) It is illustrated how to get optimum rack tooth-surface from the basic rack tooth-surface. (6) Optimum tooth-surface of each gear is generated as the envelope of the optimum rack tooth-surface family in their regular relative motion. (7) Undercut around dedendum, and tooth thickness on tip circle of the optimum pinion tooth-surface are checked. (8) The performances of testing gear drive with the optimum tooth-surface of each gear are analyzed by TCA (Tooth Contact Analysis) program developed for analysis of meshing and bearing contact. The above-mentioned system is illustrated with its application for testing involute helical gear drive. As a result, it is ascertained that the system can provide the gear drive favorable tooth bearing contact and motion transmission, even in 10 times misalignment of the maximum tolerance in JGMA Standard 114-02.
Optimum Tooth-Surface Modification for Axis-Displaced Worm-Gear Drive With Cylindrical ZA Worm
Authors: Matsuda Takashi , Sato Motohiro , Matsui Satoshi
Published: May 2009

Gear drives, which have larger misalignment than the maximum tolerance of misalignment for gear drives with parallel axes in the Standard of Japanese Gear Manufacture’s Association (JGMA Standard 114-02), are designated as axis-displaced gear drives in this study. So, axis-displacement is used in place of the misalignment. In this study, design system of optimum tooth-surface modification is developed for axis-displaced worm-gear drives with cylindrical ZA worm, which is sensitive to gear misalignments, to reduce the sensitivity to misalignment and to provide the high productivity and reliability. The system is composed by; (1) Axis-displaced wheel tooth-surface is defined as the envelope of worm tooth-surface family in their regular motion transmission (zero transmission error) under an axis-displacement. (2) Basic wheel tooth-surface is built by combining the axis-displaced tooth-surfaces under various axis-displacements. (3) Rack, whose pitch plane rolls on pitch cylinder of wheel, is introduced and then basic rack tooth-surface is obtained as the envelope of the basic wheel tooth-surface family in their regular relative motion. (4) It is illustrated how to get optimum rack tooth-surface from the basic rack tooth-surface. (5) Optimum wheel tooth-surface is generated as the envelope of the optimum rack tooth-surface family in their regular relative motion. (6) The performances of the axis-displaced worm-gear drive having the optimum wheel tooth-surface are analyzed by TCA (Tooth Contact Analysis) program which is developed for analysis of meshing and tooth bearing contact. The above-mentioned system is illustrated with its application for testing worm-gear drive. As a result, it is presented that the system can provide the testing worm-gear drive favorable tooth bearing contact and motion transmission, even in the maximum tolerance of misalignment in JGMA Standard 114-02.
Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel
Authors: Krantz Timothy , Tufts Brian
Published: May 2009

The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.