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SAE International Journal of Passenger Cars Mechanical Systems
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Influence of In-Plane and Out-of-Plane Ultrasonic Oscillations on Sliding Friction

SAE International Journal of Passenger Cars - Mechanical Systems

Technical University Berlin-Elena Teidelt, Valentin Popov, Jasminka Starcevic
  • Journal Article
  • 2011-01-2361
Published 2011-09-18 by SAE International in United States
Vibrations of varying frequency and amplitude are used in many technological areas to control friction. In this study we report the most comprehensive results of high precision measurements of the sliding friction as a function of ultrasonic oscillations. The friction force between a steel plate and a steel sample oscillating in sliding direction, perpendicular to the sliding direction, and perpendicular to the sliding plane at a frequency of 30-50 kHz has been studied.We have found that for dry friction in the absence of vibrations, it is characteristic that the frictional force slightly decreases as the velocity increases. The friction coefficient is a monotonically decreasing function of the sliding velocity. However, it will be shown, that if we excite the system using ultrasonic oscillations with an amplitude of about 0.1 μm, the frictional force becomes a monotonically increasing function of the sliding velocity. This effect can be used to suppress frictionally induced instabilities and thus might be used as a mechanism to suppress braking noises. Additionally it is shown that the friction coefficient is significantly decreased…
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Development of Low Friction and Light Weight Wheel Hub Units to Reduce Both the Brake Corner Un-Sprung Mass and Vehicle Co2 Emission - Part 2 - Weight Reduction

SAE International Journal of Passenger Cars - Mechanical Systems

SKF-Cengiz Shevket, Paolo Re
SKF Industrie SPA-Luca ciulla
  • Journal Article
  • 2011-01-2375
Published 2011-09-18 by SAE International in United States
This paper will outline the technical challenges experienced and the engineering methods used to overcome them during the endeavor to reduce wheel hub units mass and friction. Results achieved by the project team are significant and have meaningful contributions both to the unsprung mass, inertia and rolling resistance reduction. These features directly enable fuel consumption reduction and related CO2 emissions as well as positively influencing vehicle dynamics.Paper will handle two separate subjects of weight reduction and drag related power loss improvement and their combined effect at vehicle level. It will provide both simulated and test measured data as well as the validation of various features.In the very near future every milligram of CO2 reduction will count. To achieve significant improvements engineers have to think out of the box, develop breakthrough technologies and sometimes totally rewrite the rule book. This paper will outline how the project engineers have approached the problem, used modeling techniques to simulate various solutions, conducted technology scouting, selected new technologies, prototyped and fully validated robust products.
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A Case Study of Reaction Time Reduction of Vehicle Brake System

SAE International Journal of Passenger Cars - Mechanical Systems

Tata Motors Ltd.-Anshuman Gupta, Badal G. Bisen
  • Journal Article
  • 2011-01-2379
Published 2011-09-18 by SAE International in United States
There has to be a good co-relation/ relationship between the pedal effort applied, pedal travel, deceleration level achieved and stopping distance for “good brake feel”. Brake feel also depend upon the time lag between the force applied on brake pedal and the response of braking system. Hence “brake feel” can be improved by reducing the response time of the brake system. Many vehicles are having “poor brake feel” complaints, pertaining to the above mentioned reasons.This paper relates to an improved brake system for automobile in which reduction in reaction time was done by artificially increasing differential pressure head across vacuum booster diaphragm.Brake booster is given an input of compressed air to the valve body during actuation, thereby increasing the differential pressure across the diaphragm. The compressed air is bled from turbocharger-intercooler of the vehicle which is stored in a reservoir, with one way valve, while cruising. However, same compressed air is utilized by the brake booster during brake application. Additionally, the compressed air reservoir acts as a cooler for stored air.By virtue of this mechanism,…
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A Study of Parking Brake Cable Efficiency as Affected by Construction Type

SAE International Journal of Passenger Cars - Mechanical Systems

Chrysler Group LLC-Paul Stoloff
  • Journal Article
  • 2011-01-2380
Published 2011-09-18 by SAE International in United States
This paper studies the effects of various types of parking brake cable construction on parking brake system efficiency. Testing was conducted on a variety of common cable constructions from several industry sources. Cable construction variables include different types of conduit and wire strand. Input travel, input force, output travel, and output force were carefully measured under controlled conditions. Force, travel and hence work efficiencies were calculated and analyzed to identify any differences that might exist under the defined test conditions. Conclusions were drawn that might provide direction for improving parking brake system designs that have performance issues caused by poor cable efficiency.
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Spatially Resolved Temperatures in Inhomogeneous and Continuously Changing Disk Brake Interfaces

SAE International Journal of Passenger Cars - Mechanical Systems

TU Braunschweig-Kai Bode, Georg-Peter Ostermeyer
  • Journal Article
  • 2011-01-2347
Published 2011-09-18 by SAE International in United States
Widely known is the fact that friction and wear characteristics of disk brakes are subject to pronounced temperature dependencies. For systems with organically bound brake pads, many thermally induced material changes can occur, ranging from degassing of the phenolic resin binder up to degradation of fibers and melting of metallic components. All these effects modulate the surface structure between pad and disk. They are a major contributor to friction layer dynamics [1] and directly influence the system's performance.Concerning the calculation of contact temperatures in disk brakes, several attempts have been made in the past. Most of them, however, use drastic assumptions (e.g. homogenous materials and ideal contact), which limit the results to qualitative approximations [2]. Recent studies already include the multi-material structure of brake pads. These give indications on how material mixtures must be changed, in order to modify contact temperatures into a certain direction [3].This paper goes one important step further and introduces a numeric model, which is also capable to account for dynamic changes of the surface topography and chemistry during the actual…
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Effect of Directional Surface Finish of Brake Discs on Friction Behavior During Running-in

SAE International Journal of Passenger Cars - Mechanical Systems

KIRIU Corp.-Toshikazu Okamura
  • Journal Article
  • 2011-01-2382
Published 2011-09-18 by SAE International in United States
This paper focuses on the interaction in friction behavior between the surface texture of brake discs, rotational directions in braking operations and metal-cutting process, and friction materials with different degrees of aggressiveness. A factorial experiment for front brake discs was conducted by combining eight discs with directional surface finishes, two rotational directions, and two NAO friction materials on a brake dynamometer. The author analyzed several test results, such as the friction coefficients, disc wear, roughness, and the correlation between them. An assumed mechanism describing the friction behavior is discussed using the experimental results and by introducing the contribution of the aggressiveness and adhesiveness to the friction and confirmed by the test results.
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Thermal Characterization of a Li-ion Battery Module Cooled through Aluminum Heat-Sink Plates

SAE International Journal of Passenger Cars - Mechanical Systems

AVL Powertrain Engineering Inc.-Ho Teng, Yue Ma, Kim Yeow, Marina Thelliez
  • Journal Article
  • 2011-01-2248
Published 2011-09-13 by SAE International in United States
The temperature distribution is studied theoretically in a battery module stacked with 12 high-power Li-ion pouch cells. The module is cooled indirectly with ambient air through aluminum heat-sink plates or cooling plates sandwiched between each pair of cells in the module. Each of the cooling plates has an extended cooling fin exposed in the cooling air channel. The cell temperatures can be controlled by changing the air temperature and/or the heat transfer coefficient on the cooling fin surfaces by regulating the air flow rate. It is found that due to the high thermal conductivity and thermal diffusivity of the cooling plates, heat transfer of the cooling plate governs the cell temperature distribution by spreading the cell heat over the entire cell surface. Influence of thermal from the cooling fins is also simulated. It is observed that cell temperature gradients are strongly influenced by the heat transfer resistance of the cooling plate and changes in the cooling air temperature shift the cell temperatures up or down without impacting the cell temperature distribution. It is shown in…
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An Analysis of a Lithium-ion Battery System with Indirect Air Cooling and Warm-Up

SAE International Journal of Passenger Cars - Mechanical Systems

AVL Powertrain Engineering Inc.-Ho Teng, Yue Ma, Kim Yeow, Marina Thelliez
  • Journal Article
  • 2011-01-2249
Published 2011-09-13 by SAE International in United States
Ideal operation temperatures for Li-ion batteries fall in a narrow range from 20°C to 40°C. If the cell operation temperatures are too high, active materials in the cells may become thermally unstable. If the temperatures are too low, the resistance to lithium-ion transport in the cells may become very high, limiting the electrochemical reactions. Good battery thermal management is crucial to both the battery performance and life. Characteristics of various battery thermal management systems are reviewed. Analyses show that the advantages of direct and indirect air cooling systems are their simplicity and capability of cooling the cells in a battery pack at ambient temperatures up to 40°C. However, the disadvantages are their poor control of the cell-to-cell differential temperatures in the pack and their capability to dissipate high cell generations. In contrast, the advantages of direct and indirect liquid cooling systems are their good control of the maximum cell temperature and maximum differential cell temperatures in the pack and their capability of dissipating high cell heat generations with good thermal uniformity. However, high ambient temperatures…
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Brake Dynamometer Test Variability Part 2- Description of the Influencing Factors

SAE International Journal of Passenger Cars - Mechanical Systems

Consultant-Harald Abendroth
Continental Teves AG & Co. oHG-Achim Reich
  • Journal Article
  • 2011-01-2374
Published 2011-09-18 by SAE International in United States
The ISO TC22/SWG2 - Brake Lining Committee established a task force to determine and analyze root causes for variability during dynamometer brake performance testing. SAE paper 2010-01-1697 “Brake Dynamometer Test Variability - Analysis of Root Causes” [1] presents the findings from the phases 1 and 2 of the “Test Variability Project.” The task force was created to address the issue of test variability and to establish possible ways to improve test-to-test and lab-to-lab correlation.This paper presents the findings from phase 3 of this effort-description of factors influencing test variability based on DOE study. This phase concentrated on both qualitative and quantitative description of the factors influencing friction coefficient measurements during dynamometer testing. The Design of Experiments investigated factors regarding: brake cooling, environmental conditions during testing, kinetic energy level, pad soak prior to testing, location of control temperature, caliper drag condition, and number of snubs in the burnish section.The paper describes a methodology used to select the levels for the factors used during the study, and possible ranges of factor variations encountered during actual testing. The…
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Gerotor Pumps for Automotive Drivetrain Applications: A Multi Domain Simulation Approach

SAE International Journal of Passenger Cars - Mechanical Systems

Magna Powertrain-Wolfgang Schweiger, Werner Schoefmann
Purdue University-Andrea Vacca
  • Journal Article
  • 2011-01-2272
Published 2011-09-13 by SAE International in United States
This paper presents a simulation model for the analysis of internal gear ring pumps. The model follows a multi domain simulation approach comprising sub-models for parametric geometry generation, fluid dynamic simulation, numerical calculation of characteristic geometry data and CAD/FEM integration. The sub-models are interacting in different domains and relevant design and simulation parameters are accessible in a central, easy to handle graphical user interface.The potentials of the described tool are represented by simulation results for both steady state and transient pump operating conditions and by their correlation with measured data. Although the presented approach is suitable to all applications of gear ring pumps, a particular focus is given to hydraulic actuation systems used in automotive drivetrain applications. In particular, simulation results of entire drive cycles on the example of an electro-hydraulic actuated AWD coupling (considering electric control unit, electric motor, internal gear ring pump, pressure relief valve and multi-plate clutch) are presented in the final part of the paper.The presented results aim to show the capability of the developed tool for design considerations: due to…
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