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SAE International Journal of Passenger Cars Mechanical Systems
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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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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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Power Train Model Refinement Linked with Parameter Updating Through Nonlinear Optimization

SAE International Journal of Passenger Cars - Mechanical Systems

AVL LIST GmbH-Josef Zehetner
Virtual Vehicle Research and Test Center-Josef Girstmair, Hans H. Priebsch, Franz Reich
  • Journal Article
  • 2010-01-1421
Published 2010-06-09 by SAE International in United States
In the virtual development process validated simulation models are requested to accurately predict power train vibration and comfort phenomena. Conclusions from refined parameter studies enable to avoid costly tests on rigs and on the road. Thereby, an appropriate modeling approach for specific phenomena has to be chosen to ensure high quality results. But then, parameters for characterizing the dynamic properties of components are often insufficient and have to be roughly estimated in this development stage. This results in a imprecise prediction of power train resonances and in a less conclusive understanding of the considered phenomena. Conclusions for improvements remain uncertain.This paper deals with the two different aspects of model refinement and parameter updating. First an existing power train model (predecessor power train) is analyzed whether the underlying modeling approach can reproduce the physical behavior of the power train dynamics adequately. Thereby especially rotational irregularities of the power train causing the low frequency boom noise are considered. Based on the example “tire model”, different model improvements are investigated by means of sensitivity analysis. Efficient measures are…
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Spray Characteristics Study of DMF Using Phase Doppler Particle Analyzer

SAE International Journal of Passenger Cars - Mechanical Systems

Univ. of Birmingham-Guohong Tian, Haiying Li, Hongming Xu, Yanfei Li, Satish Mohan Raj
  • Journal Article
  • 2010-01-1505
Published 2010-05-05 by SAE International in United States
2,5-dimethylfuran (DMF) is currently regarded as a potential alternative fuel to gasoline due to the development of new production technology. In this paper, the spray characteristics of DMF and its blends with gasoline were studied from a high pressure direct injection gasoline injector using the shadowgraph and Phase Doppler Particle Analyzer (PDPA) techniques, This includes the spray penetration, droplet velocity and size distribution of the various mixtures. In parallel commercial gasoline and ethanol were measured in order to compare the characteristics of DMF. A total of 52 points were measured along the spray so that the experimental results could be used for subsequent numerical modeling. In summary, the experimental results showed that DMF and its blends have similar spray properties to gasoline, compared to ethanol. The droplet size of DMF is generally smaller than ethanol and decreases faster with the increase of injection pressure. The mean velocity of DMF spray droplets is similar to gasoline and higher than ethanol. Ultimately, the spray characteristics of DMF are better suited to the gasoline engine technology than its…
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Cosmetic Corrosion Test for Aluminum Autobody Panels: Final Report

SAE International Journal of Passenger Cars - Mechanical Systems

Alcoa LLC-Francine S. Bovard
Auto Technology Co.-Kevin A. Smith
  • Journal Article
  • 2010-01-0726
Published 2010-04-12 by SAE International in United States
Over the past several years a task group within the SAE Automotive Corrosion and Protection (ACAP) Committee has conducted extensive on-vehicle field testing and numerous accelerated lab tests with the goal of establishing a standard accelerated test method for cosmetic corrosion evaluations of finished aluminum auto body panels. This project has been a cooperative effort with OEM, supplier, and consultant participation and was also supported in part by DOE through USAMP (AMD 309). The focus of this project has been the identification of a standardized accelerated cosmetic corrosion test that exhibits the same appearance, severity, and type of corrosion products that are exhibited on identical painted aluminum panels exposed to service relevant environments. Multi-year service relevant exposures were conducted by mounting panels on-vehicles in multiple locations in the US and Canada. The accelerated tests have been ranked based on their relevance to the on-vehicle results and ASTM G85-A2 has been identified as the test method that most consistently replicates on-vehicle cosmetic corrosion performance. Comments concerning test reproducibility are included.
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