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SAE 2007 Noise and Vibration Conference and Exhibition
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Making Sense of Large FEA NVH Databases using SEA Concepts

Free Field Technologies, Belgium-Benoît Van den Nieuwenhof, Grégory Lielens, Jean-Pierre Coyette
INSA Lyon, France-Jean-Louis Guyader, Nicolas Totaro
Published 2007-05-15 by SAE International in United States
The paper presents an energetic post-processing methodology for large-scale vibro-acoustic finite element models. Starting from a dynamic and an acoustic modal basis produced by a finite element analysis (FEA), the methodology produces: 1synthetic and pertinent energetic outputs;2optimal SEA partitions of the finite element mesh;3quality indicators of existing SEA partitions. The methodology involves six different steps, some required, some optional: 1automatic partitioning of the FEA model in patches;2calculation of distribution matrices;3definition of mechanical loads;4definition of damping characteristics;5modal-based vibro-acoustic response calculation;6energetic post-processing;7automatic partitioning in SEA subsystems;8verification of existing SEA partitions. Each step will be presented in turn. The methodology will be illustrated by application of the successive steps to a Renault Laguna body and an Alstom two-storey TGV train section.
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To Analyze Unstable Vibration Signal of Diesel Engine Basing on the Theory of Cyclical Spectrum

Military Transportation Institute of Tianjin-Xiao Yunkui, Cao Yajuan, Zhang Lingling, Xia Tian, Wang Baomin, Yang Yuqi, Tang Li
Published 2007-05-15 by SAE International in United States
This paper searches a way to diagnose diesel engine mechanical faults by analyzing unstable vibration signal. At first, it introduces the theory of Second-order Cyclical Spectrum(SOCS) and the unstable datum acquiring principle, then analyzes the unstable vibration signals of engine by the method of SOCS. The results show that the unstable datum acquirer whose starting rotary speed is preset can measure the accelerating vibration signals of engine, and the sampling data have good stability and repeatability. The method of SOCS can effectively pick up the fault feature frequencies hiding in the accelerating vibration signals.
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Coupled Multi-Body Dynamic and Vibration Analysis of High-Speed Hypoid Geared Rotor System

University of Cincinnati-Tao Peng, Teik C. Lim
Published 2007-05-15 by SAE International in United States
High speed, precision geared rotor systems are often plagued by excessive vibration and noise problems. The response that is primarily excited by gear transmission error is actually coupled to the large displacement rotational motion of the driveline system. Classical pure vibration model assumes that the system oscillates about its mean position without coupling to the large displacement motion. To improve on this approach and understanding of the influences of the dynamic coupling, a coupled multi-body dynamic and vibration simulation model is proposed. Even though the focus is on hypoid geared rotor system, the model is more general since hypoid and bevel gears have more complicated geometry and time and spatial-varying characteristics compared to parallel axis gears. This paper presents a multi-degree-of-freedom multi-body hypoid geared rotor system dynamic model that incorporates a unique gear mesh representation to calculate the combined motion of the large displacement rotation and small displacement vibration. Numerical simulation results are analyzed in both time and frequency domains, and compared to those of the classical analytical methods or practical observation. These results also…
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A Parametric Approach for Vehicle Frame Structure Dynamics Analysis

Ford Motor Company-Sung-Ping Cheng, Anning Chen, Miles Janicki
Published 2007-05-15 by SAE International in United States
The capability to drive NVH quality into vehicle frame design is often compromised by the lack of available predictive tools that can be developed and applied within the timeframe during which key architectural design decisions are required. To address this need, a new parametric frame modeling approach was developed and is presented in this paper. This fully parameterized model is capable of fast modal, static stiffness & weight assessments, as well as DSA/optimization for frame design changes. This tool has been proven to be effective in improving speed, quality and impact of NVH hardware decisions.
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FEA Design of a Vibration Barrier to Reduce Structure Borne Noise

Henkel Technologies France-Nicolas Merlette, Jean-Luc Wojtowicki
Published 2007-05-15 by SAE International in United States
In the low frequency range, mechanical vibrations propagate into the car body by structure borne transmission. In order to limit this transmission, an original system called “Vibration Barrier” has been developed. It reduces the vibrations propagating into the hollow body network (the transmission path) using a cavity part and the high damping foam technology.This paper describes the general concept and the FEA design process of a Vibration Barrier part. An example is given for a full car body. The best compromise of the tested designs leads to a significant reduction of the structure borne noise using a lightweight part.
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Vehicle Body Optimization of Structural Noise and Vibration Using a Hybrid Technique

The Dow Chemical Company-Saeed Siavoshani, Jay Tudor, Dev Barpanda
Published 2007-05-15 by SAE International in United States
This paper describes a comprehensive hybrid technique developed for optimization of damping materials on vehicle bodies. This technique uses finite element analysis (FEA) along with experimental techniques to complement each other. In this particular application, a hybrid technique was used to address floorpan vibration and the resulting radiated noise. The objective of this approach was to develop an optimized damping material application layout. This optimized layout balances the increased performance with the overall material volume, mass, and cost. The optimized damping material application developed resulted in a 3-5 dB reduction in the floorpan vibration level while saving 10% in material volume and mass. This optimized layout was validated on a body-in-white using a laser vibrometer. In addition, a new liquid applied material was also introduced with better damping characteristics. This new material was shown to yield further material mass and volume savings with equal damping performance. This paper documents the step-by-step process and results of the damping pattern and material optimization.
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The New Blachford Acoustics Laboratory

Blachford, Inc.-Charles T. Moritz
Published 2007-05-15 by SAE International in United States
The new Blachford Acoustics Laboratory was designed and constructed to bring resources typically available only in the automotive industry to the non-passenger car markets. Prior to the opening of this laboratory, engineering tools common in the automotive industry, such as a hemi-anechoic chamber with chassis dynamometer or a reverberation room with a front of dash transmission loss suite were difficult or impossible to find for Class 8 truck, transit bus, or Class A motor home acoustical analysis. This was primarily due to vehicle size and weight, but also due to cooling air and engine exhaust extraction requirements. In a previous paper1 the author described the design of the laboratory and the acoustical goals for the various test spaces. Challenges included construction cost, sizes and weights of the test vehicles, the variety of potential products to undergo testing, and the selected laboratory site. With the facility now complete and fully functional, this paper describes the capabilities of the laboratory and compares the design goals with the as-built performance.
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Development of an Experimental FRF-Based Substructuring Model to Forward Predict the Effects of Beam Axle Design Modifications on Passenger Vehicle Axle Whine

DaimlerChrysler Corporation-Dan Ryberg, Hamid Mir
Published 2007-05-15 by SAE International in United States
This paper describes the process used to develop an experimental model with forward prediction capabilities for passenger vehicle axle whine performance, focusing initially on beam axle design modifications. This process explains how experimental Transfer Path Analysis (TPA), Running Modes Analysis (RMA) and Modal Analysis were used along with an experimental FRF-Based Substructuring (FBS) model. The objective of FBS techniques is to predict the dynamic behavior of complex structures based on the dynamic properties of each component of the structure. The FBS model was created with two substructures, the body/suspension and the empty rear beam axle housing. Each step in the creation of the baseline FBS model was correlated, and the forward predictive capability was verified utilizing an experimental modification to the beam axle structure.
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Natural Fiber Based Lightweight Sound Absorber Materials

Buckeye Technologies Inc-Jeffrey S. Hurley
Published 2007-05-15 by SAE International in United States
A variety of synthetic and natural fibers are commonly used in the construction of sound absorbers for automotive applications. Sound absorbers incorporating these fibers are produced by a variety of manufacturing processes. These manufacturing processes generally utilize synthetic or natural fibers that have a starting length of 25mm or greater. The final sound absorber may also incorporate very long yarns, filaments or pieces of partially opened textiles referred to as shoddy. Largely absent from commercial automotive sound absorbers are high levels of short natural fibers, whose length is generally less than 3mm. The focus of this work was to evaluate the sound absorption performance of materials comprised primarily of short natural fibers. The data showed that sound absorbers utilizing a majority of short natural fibers could provide equivalent sound absorption at a lower weight than traditional structures using longer fibers.
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Validation of a Hybrid Finite Element Formulation for Mid-Frequency Analysis of Vehicle Structures

Dahlian University-Sheng Li
RIETER Automotive Mtg. AG-Michel Viktorovitch, Davide Caprioli
Published 2007-05-15 by SAE International in United States
The hybrid Finite Element Analysis (hybrid FEA) has been developed for performing structure-borne computations in automotive vehicle structures [1, 2 and 3]. The hybrid FEA method combines conventional FEA with Energy FEA (EFEA). Conventional FEA models are employed for modeling the behavior of the stiff members in a system. Appropriate damping and spring or mass elements are introduced in the connections between stiff and flexible members in order to capture the presence of the flexible members during the analyses of the stiff ones. The component mode synthesis method is combined with analytical solutions for determining the driving point conductance at joints between stiff and flexible members and for defining the properties of the concentrated elements which represent the flexible members when analyzing the stiff components. Once the vibration of the stiff members and the amount of power dissipated at the damping elements has been identified, an EFEA analysis is performed in order to determine the amount of vibrational energy in the flexible members. In the past the hybrid FEA was validated for vehicle structures through…
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