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Study on the Cam-Follower Contact

Thyssenkrupp Campo Limpo Ltda-Larissa Galera
University of Campinas (Unicamp)-Natália Akemi Hoshikawa Tsuha, Katia Lucchesi Cavalca
Published 2015-09-22 by SAE International in United States
Cam-follower mechanisms are extremely important in modern equipment, widely used in automotive engines and machinery that requires complex motion with repeatability and reliability. A cam is a solid body and its shape in conjunction of follower’s type defines a movement that can be too difficult or even impossible to reproduce with others mechanisms. The objective of this analysis is the dynamic study, which is divided into kinematic and kinetics for both flat faced and offset roller follower in translating motion. The kinematics can be studied in focus on the synthesis or on the analysis. Some well-known functions applied to cam-follower pairs are cycloidal, harmonic and polynomial, however the application of classical sixth order spline is an interesting alternative to this type of study. The kinetic study has gained more importance in recent years due to increase of machinery’s speed. Thus, an approach was made by the system mass-spring-damper, widely used in automotive applications. Therefore, in order to make an initial characterization of the contact, the Hertz model was applied between the cam and the follower…
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A Numerical Approach to the Thermal Effect on the Equivalent Dynamic Coefficients of Radial Bearings

ThyssenKrupp Metalúrgica Campo Limpo Ltda.-Diogo Stuani Alves
University of Campinas - UNICAMP-Katia Lucchesi Cavalca
Published 2011-10-04 by SAE International in United States
To analyze a complete real machine, it can be convenient to divide the system into sub-systems, analyzing each sub-system individually, and then, assembling them together in the whole system. Many of these sub-systems can be found in an automotive engine, being the hydrodynamic bearing one of the most common mechanical components present in all kinds of power generation systems. Journal bearings are linking elements between parts with relative motion, and these linking elements must work to support radial loads with minimal friction and power loss. In 1925, Stodola realized that the bearing is not a rigid support, but it works like a set of springs and dashpots whose characteristics have an expressive effect on the dynamical behavior of the supported rotating shaft. Consequently, to represent the bearings by equivalent coefficients of stiffness and damping became the basis of the journal bearings study, since those coefficients can easily be inserted in a finite element model of rotating systems supported by rigid or flexible structures. However, the most general analyses for bearings in the automotive industry are…
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Transient Multi-Level Elastohydrodynamic Point Contact Algorithm Experimental Validation

Schaeffler Brasil Ltda.-Fabio Nonato
Unicamp-Katia Lucchesi Cavalca
Published 2010-10-06 by SAE International in United States
One of the great challenges of engineering teams nowadays is to overcome long and costly project experimentation phases. One effective way of decreasing such project demands is to come up with a firsthand prototype with high success probability. In order to do so, the project team should rely on robust numerical models, which can represent most of the real-life product behaviors, for instance system dynamics. For rolling element bearings, such dynamic models have to consider the dynamic interactions between its components, i.e., rolling elements and raceways. The only vibration transmitting points on rolling element bearings are the lubricated contacts. Therefore, in order to represent the full bearing dynamic behavior on a numerical model, an efficient transient contact model, which depicts the actual contact behavior, is fundamental. The primary goal of this work is to verify and validate a transient model for the elastohydrodynamic point contact, against bibliographical experimental results. A finite difference multi-level model is used to simulate the contact, taking into consideration the transient effects of the lubricant film. The static response is directly…
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Sensitivity Analysis for the Lubricant Film in Bearings Under THD Lubrication

ThyssenKrupp Metal£rgica Campo Limpo Ltda.-Robson Ferreira da Cruz
University of Campinas - UNICAMP-Diogo Stuani Alves, Katia Lucchesi Cavalca
Published 2010-10-06 by SAE International in United States
The study about the dynamic characteristics of a great number of mechanical parts has been promoted by the necessity of decreasing the vibrational effects in mechanical systems, as the reduction of superficial fatigue. In this way, the research around, even, a simple part like a hydrodynamic bearing is very important, especially in the automotive industry. In this case, the lubricant acts like a flexible liking element between the journal-bearing surfaces. The lubrication is essential for the engine, because it reduces the wear between the internal parts and prevents the metal contact. Due to the shear stresses present in the lubricant, the temperature rises and, consequently, it changes the lubricant properties. The viscosity is strongly dependent on the temperature and it is the parameter that characterizes the fluid flow and its dynamic behavior. Any temperature change induces a consequent modification in the lubricant behavior. Therefore, a thermohydrodynamics (THD) analysis allows a most accurate prediction of the bearings performance characteristics. It's known that the engine's crankshaft works, partially, in contact with the bearing wall, due to the…
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Hydrodynamic Lubrication Evaluation of Thrust Bearings

BorgWarner Brasil Ltda.-Paula Okura Nomura
University of Campinas - UNICAMP-Leonardo Carpinetti Vieira, Katia Lucchesi Cavalca
Published 2010-10-06 by SAE International in United States
The pressure generation within the lubricant fluid present in the clearance between a thrust bearing and the collar attached to the shaft has a fundamental importance to avoid contact between solid parts with axial relative motion. Any existing contact can lead to friction, wear and, as a consequence, failure of elements on a rotating machine. Therefore, in order to design an effective bearing, it is important to know how the pressure is generated within the oil film and the magnitude of the load capacity transmitted from the collar to the bearing throughout the fluid. Thus, it is necessary to solve the Reynolds' Equation to obtain the distribution of pressure on the sections under Hydrodynamic Lubrication. Then several operational parameters can be obtained, such as, the total load capacity, lubricant fluid flow, position of the maximum pressure and so on. In order to evaluate this hydrodynamic lubrication problem, a numerical solution using the Finite Difference Method in polar coordinates was applied. Operational characteristics of several thrust bearings with different geometries were evaluated. The analysis allowed the…
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Influence of Different Geometries of Hydrodynamic Bearings in the Dynamic Response of a Rotating System

Schaeffler Brasil Ltda-Gilson Arima
University of Campinas - UNICAMP-Tiago Henrique Machado, Katia Lucchesi Cavalca
Published 2010-10-06 by SAE International in United States
Hydrodynamic bearings are widely used in rotating machines, being the element responsible for the interaction between the rotor and the supporting structure. Therefore, in order to describe the dynamic behavior of the rotating shafts, it is necessary to know the journal bearings dynamic characteristics. For this reason, this work aims to analyze the influence of three different geometries of journal bearings when operating in a small turbocharger for vehicular application, which implies in high rotation speed and load capacity. In this paper the analysis will be done through the frequency response of the proposed system and the equivalent damping and stiffness coefficients coming from the oil film present in the bearings. These dynamic coefficients are obtained with a spring-damper approach, in order to represent the inherent flexibility and damping of the oil film. The equivalent coefficients of the journal bearings are derivated by computational simulation, solving the Reynolds equation. In this case, the coefficients are evaluated by the perturbation theory applied to the displacements and velocities of the shaft center inside the bearings. Thus, the…
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Dynamic Analysis of Ball Bearings

Schaeffler Brasil Ltda-Rafael Vischi Carvalho, Fabio Nonato
UNICAMP-Katia Lucchesi Cavalca
Published 2009-10-06 by SAE International in United States
The development area of the bearing's industry constantly searches for a better efficiency and a lower film oil thickness in surfaces with high roughness under relative motion. In these cases, operational conditions like high loads and temperatures, as well as low safety margins for weight and size, considering the lubricant viscosity, should be taken into account as fundamental design parameters. In order to know better the elastohydrodinamic lubrication effect, firstly, it is necessary to understand deeply and accurately the applied loads on the ball element bearings. For this purpose, the accurate analysis and study of the performance of these machine components is carried out, using analytical methods and giving special focus on the velocities and accelerations involved, as well as different types of loads applied on the ball element and their distribution and consequences during the ball motion inside the bearing rings. In this paper a dynamic model of the ball bearing is developed and simulated to better understand the load distribution and as basis to the elastohydrodinamic lubrication behavior and its effect.
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Dynamic analysis prediction using Multiobjective Genetic Algorithm in rotor-bearing-coupling systems

Universidade Estadual de Campinas-Katia Lucchesi Cavalca
Vulkan do Brasil Ltda-Roberto Luiz Escobar
Published 2006-11-21 by SAE International in United States
The study of rotative machines occupies an outstanding position in the context of machines and structures in view of significant amount of typical phenomena in the operation of those equipments. The existence of a rotative component leaning by bearings and transmitting power and torque creates a family of problems that are found in the most several machines. Therefore, in the study of the dynamic behavior of those systems, it is necessary to be determined the interaction among all the components that affect in a significant way the dynamic behavior of the system.It is proposed, this way, to determine the dynamic behavior of Rotor-Bearing-Coupling system using a Multiobjective Genetic Algorithm coupled with Surface Response Method. The Rotor-Bearing-Coupling system has the support structure or foundation practically rigid, in way to allow the analysis of the transverse or flexional vibrations of the system. With the purpose of analyzing the dynamic behavior of the system, a simplified model was considered to represent it. However, little information exists about the dynamic behavior of the stiffness coefficients and damping parameters. For…
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Hydrodynamic Lubrication Applied to Bearings with Oscillating Motion in Internal Combustion Engines

Unicamp-Irineu Gandara Neto, Katia Lucchesi Cavalca, Antonio Carlos Bannwart
Published 2005-11-22 by SAE International in United States
This work has for purpose to develop a mathematical model for the hydrodynamic lubrication of bearings with oscillating motion. The motivation lies in the tribology of internal combustion engines, specifically the lubrication problem at the bearing existing between the connecting rod and the piston pin. This kind of bearing does not perform a complete rotation, thus characterizing a new class of oscillating motion bearings. For the analysis of lubrication, a viscous fluid flow with negligible inertia inside a narrow gap formed by two surfaces is considered. The surfaces can be considered flat and are inclined to each other. The inner surface is fixed whereas the outer one performs an oscillating motion which generates a combined Couette-Poiseuille flow inside the gap. Using the same assumptions as in classical Reynolds' lubrication equation, the simplified mass and momentum conservation equations are analytically solved to determine the velocity and pressure distributions. It is shown that at the limit when the oscillation frequency tends to zero, these distributions give Reynolds' results back. The forces on the inner surface are obtained…
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Sensitivity analysis of Fault Tree (FTA) in gearboxes to commercial vehicles using reliability concepts and design of experiments

DaimlerChrysler do Brasil Ltda.-Marcelo Guimarães Morello
UNICAMP-Katia Lucchesi Cavalca, Zilda de Castro Silveira
Published 2005-11-22 by SAE International in United States
This work has as objective the construction of a reduced fault tree to gearboxes in commercial vehicles. In this reduction, the representative statistical model of reliability is studied for all the components that generate failures, where it is complemented with an application of factorial planning with two replicates to identify the components most sensible to the variation of the parameters in the reliability distributions. Thus, fault tree was constructed from the factors of scale (α) and form (β) for each component. From the data statistical models are obtained to individual failures, and the study of the degree of sensitivity of these components into system becomes viable by the reduction of the model of the FTA and applications of design of experiments. With these techniques, the FTA can be reduced as well as the number of failures around 30%, which contributes in the direction of the improvement of product's reliability, in this case, gearboxes. This procedure can be extended to other systems of a vehicle, allowing the statistics modeling of the system that contribute to the…
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