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SAE International Journal of Passenger Cars Mechanical Systems
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Investigation of Tire-Road Noise with Respect to Road Induced Wheel Forces and Radiated Airborne Noise

SAE International Journal of Passenger Cars - Mechanical Systems

Daimler AG-Gregor Koners, Ralf Lehmann
  • Journal Article
  • 2014-01-2075
Published 2014-06-30 by SAE International in United States
Low interior noise levels in combination with a comfortable sound is an important task for passenger cars. Due to the reduction of many noise sources over the last decades, nowadays tire-road noise has become one of the dominant sources for the interior noise. Especially for manufactures of luxury cars, the reduction of tire-road noise is a big challenge and therefore a central part of NVH development.The knowledge of the noise transmission behavior based on the characteristics of the relevant sources is a fundamental of a modern NVH - development process. For tire-road noise the source characteristics can be described by wheel forces and radiated airborne noise. In combination with the related vehicle transfer functions it is possible to describe the noise transmission behavior in detail.A method for estimating wheel forces and radiated airborne noise is presented. The method is based on TPA (= Transfer Path Analysis) via matrix inversion and involves the measurement of the vehicle transfer functions. It can be applied to analyse the interior noise under different driving conditions such as driving on…
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Discrete Flow Mapping - A Mesh Based Simulation Tool for Mid-to-High Frequency Vibro-Acoustic Excitation of Complex Automotive Structures

SAE International Journal of Passenger Cars - Mechanical Systems

Nottingham Trent University-David J. Chappell
University of Nottingham-Gregor Tanner
  • Journal Article
  • 2014-01-2079
Published 2014-06-30 by SAE International in United States
Modelling the vibro-acoustic properties of mechanical built-up structures is a challenging task, especially in the mid to high frequency regime, even with the computational resources available today. Standard modelling tools for complex vehicle parts include finite and boundary element methods (FEM and BEM), as well as Multi-Body Simulations (MBS). These methods are, however, robust only in the low frequency regime. In particular, FEM is not scalable to higher frequencies due to the prohibitive increase in model size. We have recently developed a new method called Discrete Flow Mapping (DFM), which extends existing high frequency methods, such as Statistical Energy Analysis or the so-called Dynamical Energy Analysis (DEA), to work on meshed structures. It provides for the first time detailed spatial information about the vibrational energy of a whole built-up structure of arbitrary complexity in this frequency range. The response of small-scale features and coupling coefficients between sub-components are obtained through local FEM models integrated in the global DFM treatment. The computational cost of DFM is largely frequency independent making it possible to get results from…
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FE Simulation of the Transmission Loss Performance of Vehicle Acoustic Components at Low and Medium Frequencies

SAE International Journal of Passenger Cars - Mechanical Systems

Autoneum AG-Rainer Stelzer, Theophane Courtois
Hyundai Motor Company-Ki-Sang Chae, Daewon SEO, Seok-Gil Hong
  • Journal Article
  • 2014-01-2081
Published 2014-06-30 by SAE International in United States
The assessment of the Transmission Loss (TL) of vehicle components at Low-Mid Frequencies generally raises difficulties associated to the physical mechanisms of the noise transmission through the automotive panel. As far as testing is concerned, it is common in the automotive industry to perform double room TL measurements of component baffled cut-outs, while numerical methods are rather applied when prototype or hardware variants are not available. Indeed, in the context of recent efforts for reduction of vehicle prototypes, the use of simulation is constantly challenged to deliver reliable means of decision during virtual design phase.While the Transfer matrix method is commonly and conveniently used at Mid-High frequencies for the calculation of a trimmed panel, the simulation of energy transfer at low frequencies must take into account modal interactions between the vehicle component and the acoustic environment. After providing a brief review of the established approaches for TL simulation at LF, the article will present a new FE methodology for TL simulation and introduce the advantages of “in-situ” TL simulations by means of fluid-structure FE calculation.…
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NVH Integration of Twin Charger Direct Injected Gasoline Engine

SAE International Journal of Passenger Cars - Mechanical Systems

Volvo Car Group-Ashish Shah, David Lennström, Per-Olof Sturesson, William Easterling
  • Journal Article
  • 2014-01-2087
Published 2014-06-30 by SAE International in United States
The increased focus and demands on the reduction of fuel consumption and CO2 requires the automotive industry to develop and introduce new and more energy efficient powertrain concepts. The extensive utilisation of downsizing concepts, such as boosting, leads to significant challenges in noise, vibration and harshness (NVH) integration. This is in conflict with the market expectation on the vehicle's acoustic refinement, which plays an increasingly important role in terms of product perception, especially in the premium or luxury segment. The introduction of the twin charger boosting system, i.e. combining super and turbo charging devices, enables downsizing/speeding in order to achieve improved fuel economy as well as short time-to-torque, while maintaining high driving dynamics. This concept requires also extensive consideration to NVH integration. The NVH challenges when integrating a roots type supercharger are very extensive. The high frequency source characteristics of the supercharger result in complex wave propagation inside the intake duct system since exciting pulsation orders are well above duct cut-on frequencies. The source strength in relation to audible interior tonal noise threshold is also…
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Evaluation of Trim Absorption to Exterior Dynamic and Acoustic Excitations Using a Hybrid Physical-Modal Approach

SAE International Journal of Passenger Cars - Mechanical Systems

Free Field Technologies-Ze Zhou, Jonathan Jacqmot, Gai Vo Thi
Hyundai Motor Company-Kang-Duck Ih
  • Journal Article
  • 2014-01-2080
Published 2014-06-30 by SAE International in United States
The NVH study of trimmed vehicle body is essential in improving the passenger comfort and optimizing the vehicle weight. Efficient modal finite-element approaches are widely used in the automotive industry for investigating the frequency response of large vibro-acoustic systems involving a body structure coupled to an acoustic cavity. In order to accurately account for the localized and frequency-dependant damping mechanism of the trim components, a direct physical approach is however preferred. Thus, a hybrid modal-physical approach combines both efficiency and accuracy for large trimmed body analysis. Dynamic loads and exterior acoustic loads can then be applied on the trimmed body model in order to evaluate the transfer functions between these loads and the acoustic response in the car compartment. The scenario study of installing different trim components into the vehicle provides information on the acoustic absorption and dynamic damping with regard to added vehicle weight by the trim.This paper demonstrates, through an industrial example, the creation of hybrid model of a trimmed vehicle body, the weakly coupled process of calculating and applying excitation from simplified…
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Direct Sound Radiation Testing on a Mounted Car Engine

SAE International Journal of Passenger Cars - Mechanical Systems

Hyundai Motor Company-Daewoon Kim
Microflown Technologies BV-Daniel Fernandez Comesana, Emiel Tijs
  • Journal Article
  • 2014-01-2088
Published 2014-06-30 by SAE International in United States
For (benchmark) tests it is not only useful to study the acoustic performance of the whole vehicle, but also to assess separate components such as the engine. Reflections inside the engine bay bias the acoustic radiation estimated with sound pressure based solutions. Consequently, most current methods require dismounting the engine from the car and installing it in an anechoic room to measure the sound emitted. However, this process is laborious and hard to perform.In this paper, two particle velocity based methods are proposed to characterize the sound radiated from an engine while it is still installed in the car. Particle velocity sensors are much less affected by reflections than sound pressure microphones when the measurements are performed near a radiating surface due to the particle velocity's vector nature, intrinsic dependency upon surface displacement and directivity of the sensor. Therefore, the engine does not have to be disassembled, which saves time and money. An array of special high temperature particle velocity probes is used to measure the radiation simultaneously at many positions near the engine of…
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The Proper Use of Plane Wave Models for Muffler Design

SAE International Journal of Passenger Cars - Mechanical Systems

Ain Shams University-Tamer Elnady
University of Kentucky-David W. Herrin, Xin Hua, Yitian Zhang
  • Journal Article
  • 2014-01-0016
Published 2014-04-01 by SAE International in United States
In many industries, muffler and silencer design is primarily accomplished via trial and error. Prototypes are developed and tested, or numerical simulation (finite or boundary element analysis) is used to assess the performance. While these approaches reliably determine the transmission loss, designers often do not understand why their changes improve or degrade the muffler performance. Analyses are time consuming and models cannot be changed without some effort. The intent of the current work is to demonstrate how plane wave muffler models can be used in industry. It is first demonstrated that plane wave models can reliably determine the transmission loss for complicated mufflers below the cutoff frequency. Some tips for developing dependable plane wave models are summarized. Moreover, it is shown that plane wave models used correctly help designers develop intuition and a better understanding of the effect of their design changes.
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A Study on Modeling of Driver's Braking Action to Avoid Rear-End Collision with Time Delay Neural Network

SAE International Journal of Passenger Cars - Mechanical Systems

Shibaura Institute of Technology-Toshiya Hirose, Masato Gokan, Nobuyo Kasuga, Toichi Sawada
  • Journal Article
  • 2014-01-0201
Published 2014-04-01 by SAE International in United States
Collision avoidance systems for rear-end collisions have been researched and developed. It is necessary to activate collision warnings and automatic braking systems with appropriate timing determined by a monitoring system of a driver's braking action. Although there are various systems to monitor driving behavior, this study aims to create a monitoring system using a driver model. This study was intended to construct a model of a driver's braking action with the Time Delay Neural Network (TDNN).An experimental scenario focuses on rear-end collisions on a highway, such as the driver of a host vehicle controlling the brake to avoid a collision into a leading vehicle in a stationary condition caused by a traffic jam. In order to examine the accuracy of the TDNN model, this study used four parameters: the number of learning, the number of neurons in the hidden layer, the sampling time with 0.01 second as a minimum value, and the number of the delay time. In addition, this study made a comparative review of the TDNN model and the Neural Network (NN) model…
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Analytical Study of a Dog Clutch in Automatic Transmission Application

SAE International Journal of Passenger Cars - Mechanical Systems

General Motors Co.-Chengwu Duan
  • Journal Article
  • 2014-01-1775
Published 2014-04-01 by SAE International in United States
A dog clutch, if successfully implemented in an automatic transmission, provides better packaging and the potential for improved fuel economy. The technical requirements for this concept are examined through modeling and simulation. As a first step, a physics-based component level model is developed that provides an understanding of the basic contact and impact dynamics. The model is compared to a built-in AMESim block to establish confidence. This component level model is then integrated into a powertrain system model within the AMESim environment. As a test bed, the powertrain model is exercised to simulate a friction plate to dog clutch shift in a 6-speed automatic transmission. The analysis helps to define the slip speed target at the onset of the dog clutch engagement while ensuring shift requirements are met. Finally, the model is validated by comparing the simulated results with measured dynamometer data.
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Validation of the Localized Fire Test Method for On-Board Hydrogen Storage Systems

SAE International Journal of Passenger Cars - Mechanical Systems

Japan Automobile Research Institute-Yohsuke Tamura, Masayuki Takeuchi, Kiyotaka Maeda, Noriaki Ohtsuka
Toho Univ.-Kenji Sato
  • Journal Article
  • 2014-01-0421
Published 2014-04-01 by SAE International in United States
The localized fire test provided in the Global Technical Regulation for Hydrogen Fuel Cell Vehicles gives two separate test methods: the ‘generic installation test - Method 1′ and the ‘specific vehicle installation test - Method 2′. Vehicle manufacturers are required to apply either of the two methods. Focused on Method 2, the present study was conducted to determine the characteristics and validity of Method 2. Test results under identical burner flame temperature conditions and the effects of cylinder protection covers made of different materials were compared between Method 1 and Method 2.The following results were obtained: (1) Methods 1 and 2 produced nearly identical results when the minimum temperature profile in the GTR test procedure was followed in both cases. (2) A steel protection cover on the cylinder significantly lowered cylinder surface temperatures during the fire test until activation of the thermal pressure relief device (TPRD). (3) A thermoplastic cover on the cylinder melted during the fire test and produced an engulfing pool fire during the localized fire portion of the test that accelerated activation…
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