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SAE International Journal of Passenger Cars Mechanical Systems
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A Parallel Hybrid Electric Drivetrain Layout with Torque-Fill Capability

SAE International Journal of Passenger Cars - Mechanical Systems

Oerlikon Graziano SpA-Carlo Cavallino
Univ. of Surrey-Arash Mehdizadeh Gavgani, Timothy Bingham, Aldo Sorniotti, John Doherty
  • Journal Article
  • 2015-01-9108
Published 2015-07-01 by SAE International in United States
This paper discusses the torque-fill capability of a novel hybrid electric drivetrain for a high-performance passenger car, originally equipped with a dual-clutch transmission system, driven by an internal combustion engine. The paper presents the simulation models of the two drivetrains, including examples of experimental validation during upshifts. An important functionality of the electric motor drive within the novel drivetrain is to provide torque-fill during gearshifts when the vehicle is engine-driven. A gearshift performance indicator is introduced in the paper, and the two drivetrain layouts are assessed in terms of gearshift quality performance for a range of maneuvers.
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On Optimum Choice of Forchheimer Equation Coefficients for Computational Fluid Dynamics Simulation of Heat Exchangers

SAE International Journal of Passenger Cars - Mechanical Systems

Cranfield Univ-Klementina Gerova, Anthony Savill
  • Journal Article
  • 2015-01-9110
Published 2015-07-01 by SAE International in United States
The simulation of heat exchanger air flow characteristics using Computational Fluid Dynamics requires knowledge of the experimental pressure drop across the element concerned. This is normally achieved through wind tunnel testing of either full scale heat exchangers or by using laminations of various porous materials and honeycombs to represent these. The current paper both continues and compliments prior work published by the lead author, which entailed a series of measurements of the pressure drop in both the near and far field, across screens with porosity (β) in the range 0.41 < β < 0.76. This experimental investigation established a relationship between the porosity and the pressure drop characteristics of a given material at various angles of inclination to the free-stream flow. In addition, the effect of screen depth was investigated using honeycombs. The present paper investigates the use of a weighted least squares regression model to correct the previously obtained Forchheimer Equation coefficients for residual errors associated with the data being a function of the underlying experimental measurements. Following a review of the available relations…
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Introducing Functional Data Analysis to Coast Down Modeling for Rolling Resistance Estimation

SAE International Journal of Passenger Cars - Mechanical Systems

Roskilde University Center-Lasse G. Andersen, Jesper K. Larsen
  • Journal Article
  • 2015-01-9111
Published 2015-07-01 by SAE International in United States
Coast-down modeling has been widely used to assess vehicle aerodynamic drag and rolling resistance by fitting a vehicle resistance model to speed measurements and thereby get an estimate on model parameters. Here a coast-down model is used for assessing how road surface characteristics influence rolling resistance. Parameter estimation as well as an extensive perturbation analysis of the parameter fit with respect to data noise has been performed. Functional Data Analysis (FDA) is introduced and discussed as a tool for this. It is concluded that FDA is a powerful tool for 1) approximating derivatives, 2) assessing the degree of smoothing of the data 3) handling noise sources in the perturbation analysis and 4) enabled numerical solutions of the coast-down Ordinary Differential Equation (ODE) model. Investigations showed that MPD was the most important parameter compared to IRI although MPD data required smoothing for optimal model fit. Furthermore, it is concluded that the model responds nicely to the statistical tests in the perturbation analysis. However, certain parameters associated with surface related rolling resistance were unstable in the sensitivity…
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NVH Development of Aluminum Axles

SAE International Journal of Passenger Cars - Mechanical Systems

American Axle & Mfg Inc.-Zhaohui Sun, Glen Steyer, Chih Hung Chung, Gregory Kopp
  • Journal Article
  • 2015-01-2188
Published 2015-06-15 by SAE International in United States
This paper discusses approaches to properly design aluminum axles for optimized NVH characteristics. By effectively using well established and validated FEA and other CAE tools, key factors that are particularly associated with aluminum axles are analyzed and discussed. These key factors include carrier geometry optimization, bearing optimization, gear design and development, and driveline system dynamics design and integration. Examples are provided to illustrate the level of contribution from each main factor as well as their design space and limitations. Results show that an aluminum axle can be properly engineered to achieve robust NVH performances in terms of operating temperature and axle loads.
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Elastohydrodynamic Lubrication Damping of Spiral Bevel Gears at Moderate Loads

SAE International Journal of Passenger Cars - Mechanical Systems

University of Cincinnati-Srikumar C Gopalakrishnan, Teik Lim
  • Journal Article
  • 2015-01-2173
Published 2015-06-15 by SAE International in United States
Modeling of elastohydrodynamic lubrication phenomena for the spiral bevel gears is performed in the present study. The damping and the friction coefficient generated from the lubricated contact area will have profound effects on the dynamics of spiral bevel gears. Thus the damping value generated from this friction model will be time varying. This makes the use of constant and empirical damping value in the dynamics of spiral bevel gears questionable. The input geometric and kinematic data required for the elastohydrodynamic lubrication (EHL) simulations are obtained using Tooth Contact Analysis. A full numerical elastohydrodynamic lubrication simulations are carried out using asymmetric integrated control volume (AICV) algorithm to compute the contact pressures. The fast Fourier transform is used to calculate the elastic deformations on the gear surfaces due to contact load. The computed pressures and the effective viscosity are used to calculate the time varying damping for the spiral bevel gears. Parametric studies are also conducted by varying the rolling velocities, lubricant properties and torque load to explain the effect of lubrication on the spiral bevel gear…
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Start-Up Transient Vibration Analysis of a Vehicle Powertrain System Equipped with a Nonlinear Clutch Damper

SAE International Journal of Passenger Cars - Mechanical Systems

Ohio State University-Laihang Li, Rajendra Singh
  • Journal Article
  • 2015-01-2179
Published 2015-06-15 by SAE International in United States
The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with focus on the development and experimental validation of the nonlinear powertrain models. First, a new nonlinear four-degree-of-freedom torsional powertrain model for this transient event, under instantaneous flywheel motion input, is developed and then validated with a vehicle start-up experiment. Second, the interactions between the clutch damper and the transmission transients are established via transient metrics. Third, a single-degree-of-freedom nonlinear model, focusing on the multi-staged clutch damper, is developed and its utility is then verified.
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Source-Path-Contribution Methodologies across a Wide Range of Product Types

SAE International Journal of Passenger Cars - Mechanical Systems

Sound Answers Inc.-Todd Freeman, Gabriella Cerrato
  • Journal Article
  • 2015-01-2360
Published 2015-06-15 by SAE International in United States
Source-path-contribution (SPC) analysis, or transfer-path-analysis, is a test based method to characterize noise and vibration contributions of a complex system. The methodology allows for the user to gain insight into the structural forces and acoustic source strengths that are exciting a system, along with the effects of the structural and acoustic paths between each source and a receiver position. This information can be utilized to understand which sources and/or paths are dominating the noise and vibration performance of a system, allowing for focused target cascading and streamlined troubleshooting efforts. The SPC process is widely used for automotive applications, but is also applicable for a wide range of product types. For each unique application the basic SPC principles remain constant, however best practices can vary for both measurement and analysis depending on the type of system being evaluated. In this paper the application of the SPC process is described across a range of different applications including automotive, agricultural, small engine, and smaller component-level applications.
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Development of a Non-Linear Clutch Damper Experiment Exhibiting Transient Dynamics

SAE International Journal of Passenger Cars - Mechanical Systems

Ohio State Univ.-Michael Krak, Jason Dreyer, Rajendra Singh
  • Journal Article
  • 2015-01-2189
Published 2015-06-15 by SAE International in United States
Many powertrain structural sub-systems are often tested under steady state conditions on a dynamometer or in a full vehicle. This process (while necessary) is costly and time intensive, especially when evaluating the effect of component properties on transient phenomena, such as driveline clunk. This paper proposes a laboratory experiment that provides the following: 1) a bench experiment that demonstrates transient behavior of a non-linear clutch damper under non-rotating conditions, 2) a process to efficiently evaluate multiple non-linear clutch dampers, and 3) generates benchmark time domain data for validation of non-linear driveline simulation codes. The design of this experiment is based on a previous experimental work on clunk. A commercially available non-linear clutch damper is selected and the experiment is sized accordingly. The stiffness and hysteresis properties of the clutch damper are assumed from the measured quasi-static torque curve provided by the manufacturer. Dissipation sources within the experiment are estimated as well. Instrumentation and time domain signal processing issues are discussed and typical measurements are compared to a simplified model for verification.
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Interaction of Gear-Shaft Dynamics Considering Gyroscopic Effect of Compliant Driveline System

SAE International Journal of Passenger Cars - Mechanical Systems

Chongqing University-Xuan Li
University of Cincinnati-Yawen Wang, Junyi Yang, Guohua Sun, Teik Lim
  • Journal Article
  • 2015-01-2182
Published 2015-06-15 by SAE International in United States
Due to the design of lightweight, high speed driveline system, the coupled bending and torsional vibration and rotordynamics must be considered to predict vibratory responses more realistically. In the current analysis, a lumped parameter model of the propeller shaft is developed with Timoshenko beam elements, which includes the effect of rotary inertia and shear deformation. The propeller shaft model is then coupled with a hypoid gear pair representation using the component mode synthesis approach. In the proposed formulation, the gyroscopic effect of both the gear and propeller shaft is considered. The simulation results show that the interaction between gear gyroscopic effect and propeller shaft bending flexibility has considerable influence on the gear dynamic mesh responses around bending resonances, whereas the torsional modes still dominate in the overall frequency spectrum. The splitting of bending resonance peaks is observed in the dynamic bearing force spectrums, which indicates that the gyroscopic effect of gear and shaft is not negligible if accurate evaluation of the system responses is desired. This study provides an understanding of the interaction between hypoid…
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Development of Refined Clutch-Damper Subsystem Dynamic Models Suitable for Time Domain Studies

SAE International Journal of Passenger Cars - Mechanical Systems

Ohio State University-Almahdi Saleh, Michael Krak, Jason Dreyer, Rajendra Singh
  • Journal Article
  • 2015-01-2180
Published 2015-06-15 by SAE International in United States
This study examines clutch-damper subsystem dynamics under transient excitation and validates predictions using a new laboratory experiment (which is the subject of a companion paper). The proposed models include multi-staged stiffness and hysteresis elements as well as spline nonlinearities. Several example cases such as two high (or low) hysteresis clutches in series with a pre-damper are considered. First, detailed multi-degree of freedom nonlinear models are constructed, and their time domain predictions are validated by analogous measurements. Second, key damping sources that affect transient events are identified and appropriate models or parameters are selected or justified. Finally, torque impulses are evaluated using metrics, and their effects on driveline dynamics are quantified. Dynamic interactions between clutch-damper and spline backlash nonlinearities are briefly discussed.
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