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SAE International Journal of Passenger Cars Mechanical Systems
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Mode Coupling Instabilities Induced by a Periodic Coefficient of Friction

SAE International Journal of Passenger Cars - Mechanical Systems

Institute of Dynamics and Vibration-Matthias Graf
Technical Univ. of Braunschweig-Georg P. Ostermeyer
  • Journal Article
  • 2010-01-1687
Published 2010-10-10 by SAE International in United States
To predict and minimize squeal propensity in brake systems, numerous models, which perform friction induced vibration, are available. However, today there is no model that can explain satisfactorily the dynamic behavior of brake systems. We argue that this is - among other effects - because existing models are based on decaying or constant coefficient of friction, although many investigations indicate rich dynamics of the coefficient of friction. Stability analysis of linear differential equations with periodic coefficients shows that instability regions change with rising amplitude of the periodic coefficients. If the periodic coefficient corresponds to the coefficient of friction, its periodicity can lower the stability of a minimal model.
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Development of a Control Method to Reduce Acceleration Shock in Motorcycles

SAE International Journal of Passenger Cars - Mechanical Systems

Kawasaki Heavy Industries, Ltd.-Hirohide Matsushima
  • Journal Article
  • 2010-32-0106
Published 2010-09-28 by SAE International in United States
The purpose of this paper is to propose a control method to reduce acceleration shock in motorcycles. Reducing the acceleration shock is very important in improving driveability of motorcycles. Motorcycles equipped with manual transmission have some backlashes in the transmission, with large backlash especially in dog clutch portions. We have figured out that one of the main causes of the acceleration shock is the collision of the dogs at high relative angular velocity during acceleration. Also, our data analysis has revealed that there is a correlation between a peak value of the longitudinal body acceleration and the relative angular velocity at the moment of the dog collision. A simulation was undertaken to verify this phenomenon, and its results have made it clear that we need to decrease the relative angular velocity at the moment of the dog collision so as to reduce the acceleration shock. Therefore, we have developed a control method that estimates a relative angle of the dogs and implements ignition timing retard control just before the dog collision to decrease relative angular…
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Squeak & Rattle Simulation - A Success Enabler in the Development of the New Saab 9-5 Cockpit without Prototype Hardware

SAE International Journal of Passenger Cars - Mechanical Systems

Saab Automobile AB-Jens Weber, Ismail Benhayoun
  • Journal Article
  • 2010-01-1423
Published 2010-06-09 by SAE International in United States
To achieve “right first time” design for SAAB projects, thus avoiding unnecessary development loops, a squeak & rattle simulation tool was required. This paper presents a new squeak & rattle simulation approach which covers the complete development process of interior parts. The process starts with a rough model, which is mainly based on styling data and ends with a model of a very high detail level close to serial tooling status. The detailed CAD model is then represented by a simulation model of similarly increasing quality. By using different types of analyses in the frequency and time domains (modal analysis, frequency response and transient analysis), the output of these simulations can be matched to the available FE model quality. During initial development the global behavior of the structure is of interest. Finally the relative displacement between two detailed trim parts is used to evaluate the risk for squeak & rattle. In order to identify the capability of the squeak & rattle simulation different correlation work between test and simulation has been performed. Examples of modal…
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Measurement of Airflow Resistivity Variation Due to Temperature and Its Impact on Simulated Sound Absorption Inside a Vehicle's Passenger Compartment

SAE International Journal of Passenger Cars - Mechanical Systems

Fiat Group Automobiles-Piercarlo Miglietta, Elena Negro, Francesco Sini, Guido Nierop, Giovanni Toniato
INRIM-Claudio Guglielmone, Alessandro Schiavi
  • Journal Article
  • 2010-01-1417
Published 2010-06-09 by SAE International in United States
Airflow resistivity is one of the most important parameters in the study of the physical properties of porous acoustic materials. This parameter is fundamental for the correct evaluation of sound absorption of acoustic materials and is needed in all the theoretical models.In the present work, airflow resistivity of porous materials is determined under effective operating conditions inside a vehicle (temperature, compression of the panels). Starting from the discussion on the measurement uncertainty, experimental data of airflow resistivity, measured as a function of temperature and applied static loads, are presented. By introducing the measured values in a SEA model of a typical vehicle panel, the foreseen values of acoustic absorption due to variation of temperature and static load are determined and presented.
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Effect of Beading on Radiated Noise

SAE International Journal of Passenger Cars - Mechanical Systems

ESI GmbH-Denis Blanchet, Willem Van Hal, Arnaud Caillet
  • Journal Article
  • 2010-01-1407
Published 2010-06-09 by SAE International in United States
In the automotive industry, the use of beading is widely spread. Beads are primarily used to stiffen the floor and dash panels. The aim is to reduce vibration levels and hopefully at the same time reduce radiated noise. Beading has a positive effect close to the first panel mode's natural frequency however it can have a negative effect at all other frequencies. Typically, engineers assume a radiation efficiency of “1” (one) over the whole frequency range for simplicity or lack of available implemented formulation in their simulation tools. This assumption directs the investigation at reducing the vibration levels only. This approach can be misleading because even though radiation efficiency tends to “1” (one) above coincident frequency it is not the case below coincidence. While increasing stiffness reduces vibration levels, it also increases radiation efficiency. This can yield to higher levels of radiated noise.This paper presents a comparison between panels with uniform cross-section and beaded panels in two different configurations: i) Academic frame and plate case and ii) Automotive floor. Vibration levels, radiation efficiency and sound…
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NVH of Electric Vehicles with Range Extender

SAE International Journal of Passenger Cars - Mechanical Systems

AVL LIST GmbH-Alfred Rust, Bernhard J. Graf
  • Journal Article
  • 2010-01-1404
Published 2010-06-09 by SAE International in United States
Intensive R&D is currently performed worldwide on hybrid and electric vehicles. For full electric vehicles the driving range is limited by the capacity of currently available batteries. If such a vehicle shall increase its driving range some range extending backup system should be available. Such a Range Extender is a small system of combustion engine and electric generator which produces the required electricity for charging the batteries in time.Since the acoustic response of an electric motor driving the vehicle and of a combustion engine as part of a Range Extender is very different by nature an extensive acoustic tuning of the Range Extender is necessary to meet the requirements of exterior vehicle noise and passenger comfort.This paper describes the NVH (noise, vibration & harshness) development work of a range extender within the AVL approach of an electrically driven passenger car with range extender. This work started with an acoustic front loading in the concept and design stage and was continued with intensive testing during combustion and engine development followed by the acoustic integration into the…
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Simulation Methodology for Consideration of Injection System on Engine Noise Contribution

SAE International Journal of Passenger Cars - Mechanical Systems

AVL AST d.o.o.-Borislav Klarin, Mario Jelovic
AVL LIST GmbH-Thomas Resch
  • Journal Article
  • 2010-01-1410
Published 2010-06-09 by SAE International in United States
The target of the investigation is the particular influence of a fuel injection system and its components as a noise source in automotive engines. The applied methodology is demonstrated on an automotive Inline 4-cylinder Diesel engine using a common rail system.This methodology is targeted as an extension of a typical standard acoustic simulation approach for combustion engines. Such approaches basically use multi-body dynamic simulation with interacting FEM based flexible structures, where the main excitation crank train, timing drive, valve train system and piston secondary motion are considered. Within the extended approach the noise excitation of the hydraulic and mechanical parts of the entire fuel system is calculated and subsequently considered within the multi-body dynamic simulation for acoustic evaluation of structural vibrations.The injection system is divided into its three main subsystems, the injector, the fuel pump and the common rail, and stepwise each of them is analyzed as a separate noise source. All three components are modeled as subsystems by 1D hydraulic model and finally combined to the complete fuel injection system. Moving mechanical components of…
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Simulation of the Dynamical Behavior of Elastic Multi-Body Systems with Bolted, Rough Contact Interfaces

SAE International Journal of Passenger Cars - Mechanical Systems

Graz University of Technology-Johannes Sebastian Hölzl
Univ. of Paderborn-Walter Sextro
  • Journal Article
  • 2010-01-1422
Published 2010-06-09 by SAE International in United States
For many technical applications it is necessary to avoid or to reduce vibrations. Factors benefiting from vibration reduction are for example the durability of the application, which is increased, as well as cost expenses and the level of noise, which are both decreased. Rough, bolted interfaces are common in most machines and can be used as damping devices with some effort. Perhaps in future such contact surfaces could be used as damping devices at the interfaces of an automotive engine or exhaust system. Nevertheless it is difficult to predict the effect of a change in contact interface parameters on the dynamic behavior of the entire mechanical system. Therefore a method for calculating the steady state behavior of elastic multi-body systems was developed. The basis of this method is a finite element model of each contacting unit. On each model a modal reduction is applied in order to reduce the degrees of freedom. The method of Ritz and Galerkin is used to calculate the frequency response functions of the reduced system including contact. This method allows…
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A Procedure for Efficient Trimmed Body FE Simulations, Based on a Transfer Admittance Model of the Sound Package

SAE International Journal of Passenger Cars - Mechanical Systems

Dr. Ing. h.c. F. Porsche AG-Juergen Ochs
Rieter Automotive Management AG-Theophane Courtois, Claudio Bertolini
  • Journal Article
  • 2010-01-1405
Published 2010-06-09 by SAE International in United States
Porous materials are extensively used in the construction of automotive NVH parts. The sound package design during vehicle development requires simulation methods at vehicle level that can take into consideration the dynamical behavior of porous materials. This need has led to different numerical technologies based on Biot's equations. In particular, direct FE implementations of Biot's equations have been included into some commercial FE software programs. Such implementations, while giving good results, are time consuming and difficult to apply within the time constraints given by the timeline of vehicle development programs.This paper presents an alternative methodology, thanks to which it is possible to build the coupled vibro-acoustic model of a trimmed vehicle without modeling physically the trim components. The trim is represented by means of transfer admittance matrices whose evaluation is based on an analytical space-domain procedure relying on a modified version of the classical transfer matrix method. A tool was developed to calculate these transfer matrices, starting from the construction and materials of the trim part. These matrices are stored and suitably included into the…
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Effect of Local Mesh Refinement on Inverse Numerical Acoustics

SAE International Journal of Passenger Cars - Mechanical Systems

LMS International-Koen Vansant, Michel Tournour, Stijn Donders
  • Journal Article
  • 2010-01-1413
Published 2010-06-09 by SAE International in United States
Inverse numerical acoustics is a method which reconstructs the source surface normal velocity from the sound measured in the near-field around the source. This is of particular interest when the source is rotating or moving, too light or too hot to be instrumented by accelerometers. The use of laser vibrometers is often of no remedy due to the complex shape of the source.The Inverse Numerical Acoustics technique is based on the inversion of transfer relations (Acoustic Transfer Vectors) using truncated Singular Value Decomposition (SVD). Most of the time the system is underdetermined which results in a non unique solution. The solution obtained by the truncated SVD is the minimal solution in the RMS sense. This paper is investigating the impact of non homogeneities in the mesh density (local mesh refinement) on the retrieved solution for underdetermined systems. It will be shown that if transfer quantities are inverted as such, big elements get a higher weight in the inversion. An approach is proposed to alleviate this issue and is illustrated using multiple examples.
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