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SAE Noise and Vibration Conference and Exposition
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Frictional Behavior of Automotive Interior Polymeric Material Pairs

Cryovac, Division of W. R. Grace-Edward Lee
Ford Motor Co.-Martin Trapp
Published 1997-05-20 by SAE International in United States
As automotive manufacturers continue to increase their use of thermoplastics for interior components (due to cost, weight, …), the potential for frictionally incompatible materials contacting each other, resulting in squeaks and rattles, will also increase. This will go counter to the increased customer demand for quieter interiors. To address this situation, Ford's Advanced Vehicle Technology Squeak and Rattle Prevention Engineering Department and Virginia Tech have developed a tester that can measure friction as a function of relative sliding velocity during frictional instabilities such as stick slip. The Ford/VT team is developing a polymeric material pairing database that will be used as a guide for current and future designs to eliminate potential squeak concerns. Based upon the database, along with a physical property analysis of the various plastic (viscoelastic) materials used in the interior, an analytical model will be developed as a tool to predict frictional behavior. The model will be integrated into the automotive component design process (CAD/CAM/CAE) so that potential concerns can be addressed prior to critical design milestone freeze dates.This collaborative effort between…
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Dynamic Simulation of Engine-Mount Systems

University of Colorado-Boulder-Chung-Ha Suh, Clifford G. Smith
Published 1997-05-20 by SAE International in United States
This paper presents a simplified method to determine the vibrational amplitude produced by a four-cylinder engine when supported by a viscoelastic foundation. The pistons, connecting rods, and crankshaft are modeled as rigid bodies connected to the foundation by standard industrial rubber mounts which are modeled with spring and damping elements whose location, orientation, and stiffness can be easily configured for specific design analysis, or optimized to reduce vibration and noise in a design. The paper is presented in a general algorithmic form, with a detailed numerical example emphasizing the three parts of the analysis: the mechanism kinematics, the shaking force and torque determination on the engine block, and the three-dimensional vibrational analysis.
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Statistical Energy Analysis of Noise and Vibration from an Automotive Engine

Roush-Anatrol, Inc.-Robert Unglenieks
Vibro-Acoustic Sciences, Inc.-Cliff Kaminsky
Published 1997-05-20 by SAE International in United States
Statistical energy analysis (SEA) is a validated tool for vibro-acoustic modeling of larger systems such as air- and spacecraft, ships, and automobile bodies. In this paper, we report on the application of SEA to model the noise and vibration output of a vee-configuration automotive engine above 1000 Hertz. This approach may complement boundary element methods, which are time consuming to use and can only be applied up to one or two kilohertz. In a feasibility study, experimental data is used to specify power inputs and damping losses, as well as to validate the model. The study shows that SEA can be used to model the vibrational behavior of the engine block at high frequencies that are unattainable with deterministic methods. This result may apply to other structures such as transmissions, pumps, and superchargers.
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Dynamic Analysis of Layshaft Gears in Automotive Transmission

Ohio State Univ.-Teik C. Lim, Donald R. Houser
Published 1997-05-20 by SAE International in United States
In this paper, we will present parametric results of performing dynamic analysis of layshaft gear trains typically used in automotive transmissions with emphasis on the vibratory response due to transmission error excitation. A three-dimensional multiple degrees of freedom lumped parameter dynamic model of a generic layshaft type geared rotor system (with three parallel rotating shafts coupled by two sets of gear pairs) has been formulated analytically. The model includes the effects of both rotational and translational displacements of each gears, and bounce and pitch motions of the counter-shaft. The natural frequencies and mode shapes are computed numerically by solving an eigenvalue problem derived from applying harmonic solutions to the equations of motion. The complete set of mode shapes are then used in forced response calculations based on the modal expansion method to predict gear accelerations, dynamic transmission errors, mesh force and bearing loads. Structural resonance prediction is validated by comparison to finite element result of a baseline system. The proposed model is also used to examine the effects of system parameters such as counter-shaft diameter…
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A Model Study of How Tire Construction and Materials Affect Vibration-Radiated Noise

Purdue Univ.-John Huff, J. Stuart Bolton
Vibro-Acoustic Sciences Inc.-Paul Bremner
Published 1997-05-20 by SAE International in United States
A simple mathematical model was developed and experimentally validated to evaluate how the materials and construction of an automobile tire affect its vibration-radiated noise performance. The mathematical model uses Statistical Energy Analysis (SEA) with modal joint acceptance formulations for wavespeed and radiation efficiency of orthotropically-stiffened and pressurized cylindrical shells. Experimental validation of the model included wavenumber decomposition to determine the dispersion characteristics of an inflated, non-rolling tire in the laboratory. The model is used to conduct a preliminary study into how the various tire constituent materials and construction parameters influence the vibration-radiated noise performance.
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Application of Noise Path Analysis Technique to Transient Excitation

Ford Motor Co.-P. Perry Gu, Joe Juan
Published 1997-05-20 by SAE International in United States
Road induced interior noise, vibration and harshness (NVH) of a vehicle are greatly influenced by the design of the vehicle chassis and body systems. The strategy of improving vehicle NVH performance is to reduce vehicle body sensitivities to suspension force inputs and to increase the isolation of the chassis system to road irregularities. The effectiveness of the isolation is evaluated by the magnitude of transmitted forces at all suspension-body attachments. Currently, no technique is available to directly measure the forces over a broad frequency range. Many efforts have been made to develop force estimation methods, such as Noise Path Analysis (NPA) techniques. NPA techniques have been used to estimate the transmitted forces for steady-state road and powertrain excitations. This paper presents an ongoing effort to extend the NPA techniques to transient excitations, such as impacts caused by tar strips and pot holes. Rubber-strips were used to simulate bump excitations to a vehicle. Major noise paths to vehicle interior responses were identified, using the NPA inverse matrix method. This study can be used to assess the…
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Commercial Van Diesel Idle Sound Quality

Ford Motor Co.-Anthony J. Champagne, Nae-Ming Shiau
Published 1997-05-20 by SAE International in United States
The customer's perception of diesel sounds is receiving more attention since diesel engines are being used more frequently in recent years. This paper summarizes the results of a study investigating the sound quality of diesel idle sounds in eight vans and light trucks. Subjective evaluations were conducted both in the US and the UK so that a comparison could be made. Paired comparison of annoyance and semantic differential subjective evaluation techniques were used. Correlation analysis was applied to the subjective evaluation results to determine annoying characteristics. Subjective results indicated that most annoyance rankings were similar for both the US and UK participants, with some specific differences. Correlation of objective measures to annoyance indicated a high correlation to ISO 532B loudness, dBA and kurtosis in the 1.4 kHz to 4 kHz range (aimed at quantifying the impulsiveness perception).
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Design, Construction and Application of a World Class Vehicle Acoustic Test Facility

AVL LIST GmbH-F. K. Brandl
Published 1997-05-20 by SAE International in United States
The allowable noise emission of vehicles has been continuously reduced by legislation in the past. In parallel the interior noise level and noise quality have been improved dramatically. Even small size cars show today remarkable sound quality. This general effort to reduce vehicle noise has brought about a reduction in the combined effects of noise and vibration on the passengers. Today's vehicles exhibit more closely matched noise contributions from the engine, transmission, inlet and exhaust systems as well as road inputs via the suspension.For a further improvement of vehicle noise levels and sound quality, simple reduction of individual noise sources is no longer a suitable approach. A full understanding of their combined effect on vehicle noise is required, for cost-effective and production-feasible solutions to lead to the desired noise reduction or the achievement of a typical “Brand Sound” through sound engineering. For such development work, a vehicle acoustic test facility is absolutely indispensable.To qualify as a full partner in the Automotive Industry, AVL has established a vehicle test facility equipped with the very latest technology,…
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Transmission Side Cover Design Optimization for NVH Part 1: Shell Curvature Studies

Structural Dynamics Research Corp.-Glen Steyer, Chih-Hung Chung, Brian Brassow
Published 1997-05-20 by SAE International in United States
The design of Front Wheel Drive transmission side covers is primarily driven by packaging concerns, and secondarily by structural durability requirements. While the side cover design is a very important element in the NVH performance of a transaxle, there has historically been little consideration of this concern at the design stage.The typical approach to NVH considerations on a side cover is to start with the initial prototype hardware and add any stiffening features in order to reduce the cover vibration or radiated sound. A preferred approach would be to factor the NVH considerations into the initial design. Through consideration of the packaging constraints and a goal of maximizing the fundamental natural frequency of the side cover, it is possible to select from various alternative geometries the one which best meets these objectives. Present day geometry optimization algorithms available in high-end Computer Aided Design packages provide an automated process of achieving this goal.This paper presents the first phase in addressing this design goal through a consideration of alternative methods for stiffening a flat panel in order…
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Quarter Lambda Absorbers Rejuvenated as Multi-Frequency In-Plane Arrays

Rieter Automotive Management AG-Roberto Frosio, Robert H. van Ligten
Published 1997-05-20 by SAE International in United States
A re-examination of the functioning of quarter wavelength tubular resonator absorbers did highlight the destructive interference near the tube opening (area S2) between the wave reflected from the resonator termination and the one reflected from the surface adjacent to the opening (area S1). Analytical considerations showed that, for perpendicular incidence, 100% absorption is achieved when the ratio of surface areas equals the specific termination impedance of the resonator absorber .This same mechanism is also effective when the resonator lies in the reflecting plane. This latter point has important practical consequences because it allows one to integrate practical and effective absorbers in relatively thin treatments. Experimental work has shown that S1/S2 ratio's of 20 are readily achieved, and that regarding bandwidth, one or two sets of tubes per 1/3 octave are usually adequate. Multi-frequency arrays are created by interlacing sets of tubes tuned to different frequencies. Absorber arrays should always have the openings pointed downward in mounted position in order to prevent the accumulation of liquids and dirt in the tubes.
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