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Experimental Evaluation of Rotational Inertia and Tire Rolling Resistance for a Twin Roller Chassis Dynamometer

University of Campinas - UNICAMP-Jony Javorski Eckert, Elvis Bertoti, Eduardo dos Santos Costa, Fabio Mazzariol Santiciolli, Rodrigo Yassuda Yamashita, Ludmila Corrêa de Alkmin e Silva, Franco Giuseppe Dedini
Published 2017-11-07 by SAE International in United States
Chassis dynamometers are important equipment to perform vehicular experiments in the automotive industry. Usually, these equipments are used according to standard procedures for emissions, fuel consumption, and performance analyses. In this paper, an alternative procedure was developed to experimentally determine the dynamometer inertia and losses related to bearings and transmission systems. Furthermore, a study on the tires rolling resistance, considering a double tire-roller contact, was carried out. The experiments were performed in a 4x2 chassis dynamometer with four rollers, equipped with an eddy current brake (coupled to a transmission reducer of 2.5 instrumented with a 3000 Nm torque flange) and with a 30 CV AC electric motor (coupled to a planetary transmission with reduction of 4.43 and instrumented with a 500 Nm torque flange). The dynamometer was also instrumented with an encoder system for speed measurement. All data were acquired by NI/LabVIEW™ software and post-processed in Matlab™ and Excel™ interfaces. The initial experiments resulted in the overall dynamometer bench inertia and equivalent inertias of the braking and electric motorization systems. The secondary experiments provided equations…
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A Numerical Approach to the Thermal Effect on the Equivalent Dynamic Coefficients of Radial Bearings

University of Campinas - UNICAMP-Katia Lucchesi Cavalca
ThyssenKrupp Metalúrgica Campo Limpo Ltda.-Diogo Stuani Alves
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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Sensitivity Analysis for the Lubricant Film in Bearings Under THD Lubrication

University of Campinas - UNICAMP-Diogo Stuani Alves, Katia Lucchesi Cavalca
ThyssenKrupp Metal£rgica Campo Limpo Ltda.-Robson Ferreira da Cruz
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

University of Campinas - UNICAMP-Leonardo Carpinetti Vieira, Katia Lucchesi Cavalca
BorgWarner Brasil Ltda.-Paula Okura Nomura
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

University of Campinas - UNICAMP-Tiago Henrique Machado, Katia Lucchesi Cavalca
Schaeffler Brasil Ltda-Gilson Arima
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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A GTEM Design for EMC-EMI/EMS Pre-Compliance Tests on Automotive Electronic Boards

University of Campinas - UNICAMP-Humberto Araujo, Luiz C. Kretly
Published 2010-10-06 by SAE International in United States
This work describes the design and simulation of a GTEM - Gigahertz Transverse Electromagnetic chamber. The GTEM is intended to be used for EMC-EMI/EMS pre-compliance tests on automotive electronic boards and integrated circuits. The physical conception chamber is shown for a range from 500 MHz - 18 GHz. As a crucial step in the design, the APEX (match between RF excitation and the body of the chamber) is minutely shown. The structure designed has significant advantages over the conventional available, mainly in economic terms and on the operational frequency range.
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