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SAE 2003 Noise & Vibration Conference and Exhibition
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SEA in Vehicle Development Part I: Balancing of Path Contribution for Multiple Operating Conditions

General Motors Corp.-Alan Parrett, Qijun Zhang, Chong Wang, Hua He
Published 2003-05-05 by SAE International in United States
The application of Statistical Energy Analysis (SEA) to vehicle development is discussed, with a new technique to implement noise path analysis within a SEA model to enable efficient solution and optimization of acoustic trim. A whole vehicle Performance-Based SEA model is used, in which Sound Transmission Loss (STL) and acoustic absorption coefficient characterize subsystem performance. In such a model, the net contribution from each body panel/path, such as the floor, to a specific interior subsystem, such as the driver's head space, is extremely important for vehicle interior noise development. First, it helps to identify the critical path to root-cause potential problems. Second, it is necessary in order to perform balancing of path contributions. With current software, the power based noise contribution analysis is for direct paths/adjacent subsystems. Noise path balancing requires the net contribution from each body panel for a given load case or excitation (tire/road noise or powertrain noise). A method to calculate and balance the net panel noise contributions under several operating conditions is discussed.
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Vibration Characteristics of Cardboard Inserts in Shells

General Motors Corporation-Martin G. Foulkes, James P. De Clerck
The Ohio State University-Rajendra Singh
Published 2003-05-05 by SAE International in United States
A study has been conducted to determine the noise and vibration effect of inserting a cardboard liner into a thin, circular cross-sectioned, cylindrical shell. The relevance of such a study is to improve the understanding of the effects when a cardboard liner is used in a propeller shaft for noise and vibration control purposes. It is found from the study that the liner adds significant modal stiffness, while an increase in modal mass is also observed for a particular shell type of mode. Further, the study has shown that the additional modal damping provided by the liner is not appropriately modeled by Coulomb friction damping, a damping model often intuitively associated with cardboard materials. Rather, the damping is best modeled as proportional viscous damping.
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Estimation of Dynamic Stiffness Matrix of Welded or Glued Joints Using a Laboratory Fixture

Center for Automotive Research, The Ohio State University-Pavak Mehta, Rajendra Singh
Published 2003-05-05 by SAE International in United States
Accurate quantification of welded or adhesive joints in automotive chassis structures is necessary before reliable models can be developed. Such joints undergo shear and rotational deformations, which must be characterized via diagonal stiffness elements and cross-stiffness terms in order to describe static and dynamic problems. In this paper, a frequency domain decomposition technique is employed to extract static stiffness and viscous damping matrices of dimension 2 via analytical, computational or experimental models. Methods are applied to a laboratory fixture and alternate joints are compared.
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Inverse Numerical Acoustics of a Truck Engine

LMS International-Michel Tournour, Philippe Brux, Peter Mas, Xiaochuan Wang, Colin McCulloch
Renault Trucks-Philippe Vignassa
Published 2003-05-05 by SAE International in United States
Source identification applied to a truck engine and using inverse numerical acoustics is presented. The approach is based on acoustic transfer vectors (ATV) and truncated singular value decomposition (SVD). Acoustic transfer vectors are arrays of transfer functions between surface normal velocity and acoustic pressure at response points. They can be computed using boundary element methods (indirect, direct or multi-domain direct formulations) or finite element methods (in physical or modal coordinates). Regularization techniques such as the so-called L-curve approach are used to identify the optimum SVD truncation. To increase the reliability of the source identification, the approach can use velocity measurements on the boundary surface as well as the standard nearfield pressure measurements. It also allows for linear or spline interpolation of the acoustic transfer vectors in the frequency domain, to increase computational speed. In the example shown, the nearfield pressures were acquired using an antenna, at different frequencies and RPMs. In order to check the accuracy of the proposed approach, additional mid-field pressure measurements were performed. The measurements are compared to the re-computed field and…
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Light-Weight Localized Structural Reinforcements for Structural and NVH Applications

L&L Products, Inc.-David Carlson, Michael Czaplicki, Jon Riley
Published 2003-05-05 by SAE International in United States
The use of adhesively bonded localized reinforcements is a relatively new concept in the automotive industry. Although use of this reinforcement method is in its early stages, these reinforcements are now used for a variety of applications in the automotive industry including crash worthiness, fatigue resistance, and NVH. This approach can provide relatively fast, easy, non-intrusive, and cost effective solutions for OEM's when compared to traditional reinforcement methods. Also overall weight can be simultaneously reduced since the reinforcement is placed only where it is needed instead of filling an entire section with foam or changing the metal thickness along an entire body member. Materials and concepts have been developed that can be used to improve the structural stiffness and the resulting NVH performance of the vehicle. This paper will discuss the use of localized reinforcements including materials, applications, and potential uses and the benefits.
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Minimize Driveline Gear Noise by Optimization Technique

Driveline System Engineering, Visteon Corporation-Yuejun E. Lee
Powertrain CAE, Visteon Corporation-Fatma Kocer
Published 2003-05-05 by SAE International in United States
Driveline NVH (Noise, Vibration, and Harshness) has always been a critical issue in overall vehicle NVH design. For years, numerous efforts have been made in NVH reduction. This study focuses on the development of an optimization process for driveline system NVH design. Specifically, minimization of driveline dynamic gear meshing force was performed using commercial softwares Genesis (VR&D Engineering) and IDEAS (EDS). The optimization process includes design variable selection, problem formulation and optimization algorithm selection. The developed optimization process was applied to a driveline system design with a two-piece driveshaft and independent rear suspension axle, which includes more than 40 design variables simultaneously. Results show success of driveline NVH optimization for up-front driveline NVH design, as well as great potential for developing a vehicle NVH optimization method using hybrid-modeling technology.
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A Comparison Between Power Injection and Impulse Response Decay Methods for Estimating Frequency Averaged Loss Factors for SEA

Michigan Technological University-Brandon Bloss, Mohan D. Rao
Published 2003-05-05 by SAE International in United States
Damping measurements on vehicle subsystems are rarely straightforward due to the complexity of the dynamic interaction of system joints, trim, and geometry. Various experimental techniques can be used for damping estimation, such as frequency domain modal analysis curve-fitting methods, time domain decay-rate methods, and other methods based on energy and wave propagation. Each method has its own set of advantages and drawbacks. This paper describes an analytical and an experimental comparison between two, widely used loss factor estimation techniques frequently used in Statistical Energy Analysis (SEA).The single subsystem Power Injection Method (PIM) and the Impulse Response Decay Method (IRDM) were compared using analytical models of a variety of simulated simple spring-mass-damper systems. Frequency averaged loss factor values were estimated from both methods for comparison. The parameters of the analytical models were varied to study the effects of the total number of modes, amount of damping, location of modes within frequency bands, and the width of the frequency bands on loss factor estimation.The analytical study showed that both methods give accurate loss factor values as long…
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A Comparison of the Effectiveness of Elastomeric Tuned Mass Dampers and Particle Dampers

Roush Industries, Inc.-Allan C. Aubert, Edward R. Green, Gregory Z. Chen
Published 2003-05-05 by SAE International in United States
This paper presents a study and comparison of two methods commonly used to treat unwanted vibration in vehicles. Laboratory work was done to measure and compare the effectiveness of common designs for practical tuned mass dampers (TMDs) and particle dampers under a wide range of conditions. The relative strength and weaknesses of the two approaches are compared in their abilities to treat vibration in a system due to resonant modes and forced response. The effectiveness of each method is investigated as a function of the weight of the treatment, amplitude and temperature effects.
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“Herschel-Quincke Spiral” A New Interference Silencer

FILTERWERK MANN+HUMMEL GmbH-A. J. Graefenstein, W. Wenzel
Published 2003-05-05 by SAE International in United States
Over the last ten years there has been a steady growth in the market share of light-duty diesel engines, especially in Europe. At the same time, a general trend in petrol engine development has been seen, in which normal aspirated engines are being replaced by downsized turbocharged engines. Therefore, NVH engineers have to deal with new challenges. Turbochargers produce an aerodynamic noise in the frequency range above 1000Hz, which might influence the exterior and interior noise level. As a result, the additional requirement for acoustical components to reduce this flow noise is going to pose an increasing challenge for air intake system suppliers.This paper describes a new design of well-known wide band silencer first mentioned by A. Selamet, N.S.Dickey and J.M.Novak [1,2]. The silencer works according to the interference principle. The sound is guided into two or more parallel pipes of different lengths. The difference in length can be tuned to certain frequencies so that the waves in the different pipes cancel out each other if the phase difference is 180 degrees. The new design…
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Effect of Engine Mounting Strategy on Vehicle NVH

Vibracoustic North America/Freudenberg-NOK (FNGP)-D. S. Sachdeva, R. Hadi
Published 2003-05-05 by SAE International in United States
The primary task of a powertrain mounting system is to keep the powertrain located properly in the vehicle, provide good motion control as well as good isolation. Although there are a variety of other requirements and constraints, this study focuses on the NVH aspects. While most mounting systems have the same primary function, there is a large variety of mounting systems in use in the automotive industry. This paper examines a couple of the design strategies, involving powertrain rigid body mode coupling and de-coupling. These strategies call for the rigid body modes of the powertrain, whose mounts are fixed to the ground, to have certain coupled or decoupled characteristics. Since the powertrain related NVH is affected by its behavior in the vehicle, which is often quite different from that on the ground, this study investigates the usefulness of such strategies. This study compares three such strategies that are commonly used. All decoupled modes, coupled bounce-pitch modes, and coupled bounce-roll modes strategies are compared by looking at the response of a vehicle model, to wheel and…
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