Donald J. Nefske
General Motors
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Featured researches published by Donald J. Nefske.
Journal of Sound and Vibration | 1982
Donald J. Nefske; Joseph A. Wolf; Larry J. Howell
Abstract This paper contains a brief review of the formulation of the finite element method for structural-acoustic analysis of an enclosed cavity, and illustrations are given of the application of this analytical method at General Motors Corporation to investigate the acoustics of the automobile passenger compartment. Low frequency noise in the passenger compartment (in approximately the 20–200 Hz frequency range) is of primary interest, and particularly that noise which is generated by the structural vibration of the wall panels of the compartment. The topics which are covered in the paper include the computation of acoustic modes and resonant frequencies of the passenger compartment, the effect of flexible wall panels on the cavity acoustics, the methods of direct and modal coupling of the structural and acoustic vehicle systems, and forced vibration analysis illustrating the techniques for computing panel-excited noise and for identifying critical panels around the passenger compartment. The capabilities of the finite element method are illustrated by applications to the production automobile, and experimental verifications of the various techniques are presented to illustrate the accuracy of the method.
1976 Automotive Engineering Congress and Exposition | 1976
Joseph A. Wolf; Donald J. Nefske; Larry J. Howell
The objective of this paper is to give illustrative solutions for the types of combined structural and acoustic problems which arise in the finite element analysis of the automobile passenger compartment and to review related methodology. Analysis implementation using the NASTRAN (NASA STRuctural ANalysis) computer program is discussed briefly, including the use of modal compartment wall models and forced boundary conditions. The model is a two dimensional one, assuming a uniform pressue field in the cross-body direction. This simplification appears to be adequate for the frequency range of interest (20 to 80 Hz).
1978 Automotive Engineering Congress and Exposition | 1978
Donald J. Nefske; Larry J. Howell
Low-frequency interior noise in the automobile passenger compartment can be significantly affected by the vibration behavior of the body panels surrounding the enclosed cavity. An acoustic finite element method for computing panel-excited interior noise is reviewed and an approach outlined for identifying potentially noisy panels adjacent to the passenger compartment. To illustrate its potential, the analytical method is applied to a production automobile. A structural modification suggested by the procedure is shown to reduce significantly the low-frequency interior noise to which the occupant is exposed. Experimental verification of the method is presented.
ASME 2009 International Mechanical Engineering Congress and Exposition | 2009
Sangyun Lee; Kwangseo Park; Shung H. Sung; Donald J. Nefske
An acoustic finite-element model of an automobile passenger compartment that represents the more complicated vehicle interior acoustic characteristics is developed and experimentally assessed using loudspeaker excitation. The acoustic finite-element model represents the passenger compartment cavity, trunk compartment cavity, front and rear seats, parcel shelf, door volumes, and IP (Instrument Panel) volume. The model accounts for the coupling between the compartment cavity and trunk cavity through the rear seat and parcel shelf, and the coupling between the compartment cavity and the door and IP panel volumes. Modal analysis tests of a vehicle were conducted using loudspeaker excitation to identify the compartment cavity modes and sound pressure response at a large number of interior locations. Comparisons of the predicted versus measured mode frequencies, mode shapes, and sound pressure response at the occupant ear locations are made to assess the accuracy of the model to 400 Hz.
Volume 12: New Developments in Simulation Methods and Software for Engineering Applications | 2007
Shung H. Sung; Donald J. Nefske; Douglas A. Feldmaier
An acoustic finite-element model of the automobile passenger compartment is developed and experimentally assessed for predicting the sound pressure response in the compartment. The acoustic finite-element model represents both the passenger compartment cavity and the trunk compartment cavity, with the coupling between them through the rear seats for which the acoustic properties are determined from a modified “heavy air” approximation. Measurements of the sound pressure response in the passenger compartment are obtained using a specially developed loudspeaker excitation device for assessing the accuracy of the model. Comparisons are made of the predicted versus measured sound pressure response to 300 Hz for loudspeaker excitation in both the passenger and trunk compartments.Copyright
ASME 2005 International Mechanical Engineering Congress and Exposition | 2005
Shung H. Sung; Donald J. Nefske
A regression-based energy method is developed for rapid estimation of the overall passenger-compartment interior noise (dBA) and Articulation Index (AI) in a vehicle of prescribed architecture when the vehicle travels on a particular road at a particular speed. The method is developed for use in the early vehicle design stage when only limited vehicle architecture design information are known. Regression analyses from a database of vehicle on-road tests and vehicle wind-tunnel tests are used to identify the energy transfer functions that represent the prescribed vehicle architecture. Energy excitation from both tire-road interaction and aerodynamic loads is then used to predict the interior dBA and AI responses. Comparisons of the predicted versus measured dBA and AI responses show reasonable agreement for car and wagon-type vehicles, although limited architecture data somewhat underestimates the actual response in certain vehiclesCopyright
ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012 | 2012
Shung H. Sung; Donald J. Nefske
In transportation vehicles under operating conditions, interior noise frequently results from forces transmitted through the vehicle structure that excite body panel vibrations that couple with the body modes to radiate noise to the interior. The body panel participations to the interior noise that result from the force transfer paths can be identified using acoustic and structural-acoustic finite element models of the vehicle. This paper describes the transfer path analysis method to identify the body panel and modal participations for prescribed forcing excitations to the vehicle and to evaluate the effect of structural modifications. The theoretical development of the structural-acoustic finite element method and its example applications to two automotive vehicles are presented.Copyright
ASME 2009 International Mechanical Engineering Congress and Exposition | 2009
Shung H. Sung; Donald J. Nefske; Douglas A. Feldmaier
A structural-acoustic finite element model of an automotive vehicle is developed and experimentally evaluated for predicting the structural-borne interior noise in the passenger compartment when the vehicle travels over a randomly rough road at a constant speed. The structural-acoustic model couples a structural finite element model of the vehicle with an acoustic finite element model of the passenger compartment. Measured random road profile data provides the prescribed power spectral density excitation applied at the tire-patch contact points to predict the structural-borne interior road noise. Comparisons of the predicted and measured interior noise for laboratory shaker excitation, tire patch excitation, and vehicle travel over a randomly rough road are used to assess the accuracy of the model.Copyright
Design Engineering and Computers and Information in Engineering, Parts A and B | 2006
Shung H. Sung; Donald J. Nefske
A regression-based energy method is developed for estimating the overall interior noise (dBA) and Articulation Index (AI) in the automobile passenger-compartment for engine operation at idle, 2500 rpm, and wide-open-throttle speeds. The method is developed for use in the early vehicle design stage for evaluating the effect of different vehicle and powertrain architecture designs on engine noise performance. Regression analyses from a database of standard vehicle chassis dynamometer tests are used to estimate the effect of vehicle and powertrain architectures on the acoustic energy response and resulting interior noise. Comparisons of the estimated versus measured dBA and AI responses show reasonable agreement for different powertrain types. However, the inclusion of only limited architecture details somewhat underestimates the actual response for certain engines and operating conditions.Copyright
ASME 2004 International Mechanical Engineering Congress and Exposition | 2004
Donald J. Nefske; Shung H. Sung; Douglas A. Feldmaier
Dynamic stiffness and damping rates of elastomeric vibration isolators used in automotive vehicles are identified from static isolator tests and the use of an isolator finite element model. Comparisons are made of the predicted versus measured dynamic stiffness and damping rates from 0 to 300 Hz of a rear suspension isolator to validate the technique. The identified dynamic rates of the elastomeric isolators of a representative vehicle are then input to the vehicle system finite-element model to compare the predicted versus measured vehicle vibration and interior noise response for laboratory shaker excitation.Copyright