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Technical Paper

Damping Mass Effects on Panel Sound Transmission Loss

2011-05-17
2011-01-1633
The primary function of damping treatment on a vibrating panel in a vehicle is to reduce vibration levels or radiated sound power by the dissipation of energy. However, in automotive applications the mass effects of damping materials should not be ignored, especially with regard to airborne noise performance. In this paper, a Finite Element-Statistical Energy Analysis (FE-SEA) hybrid analysis is used to evaluate the mass effects of applied damping materials on Sound Transmission Loss (STL). The analysis takes into consideration effects on both the elastic properties and modal mass of the panel. It is shown that while uniformly distributing the mass of the damping material over the panel generally over-estimate the mass effects on STL, an area weighting approach underestimates the effects. Results are confirmed by laboratory testing. A nomogram is generated to show the total effect of the mass of the damping material on STL.
Technical Paper

Modeling the Vibrations of and Energy Distributions in Car Body Structures

2011-05-17
2011-01-1573
A general numerical method, the so-called Fourier Spectral Element Method (FSEM), is described for the dynamic analysis of complex systems such as car body structures. In this method, a complex dynamic system is viewed as an assembly of a number of fundamental structural components such as beams, plates, and shells. Over each structural component, the basic solution variables (typically, the displacements) are sought as a continuous function in the form of an improved Fourier series expansion which is mathematically guaranteed to converge absolutely and uniformly over the solution domain of interest. Accordingly, the Fourier coefficients are considered as the generalized coordinates and determined using the powerful Rayleigh-Ritz method. Since this method does not involve any assumption or an introduction of any artificial model parameters, it is broadly applicable to the whole frequency range which is usually divided into low, mid, and high frequency regions.
Technical Paper

A Finite Element Method for Effective Reduction of Speaker-Borne Squeak and Rattle Noise in Automotive Doors

2011-05-17
2011-01-1583
Increasing sound quality with advanced audio technology has raised the bar for perceived quality targets for minimal interior noise and maximal speaker sound quality in a passenger vehicle. Speaker-borne structural vibrations and the associated squeak and rattle have been among the most frequent concerns in the perceived audio quality degradation in a vehicle. Digital detection of squeak and rattle issues due to the speaker-borne structural vibrations during the digital vehicle development phase has been a challenge due to the physical complexity involved. Recently, an effective finite element method has been developed to address structure-borne noise [1] and has been applied for detecting the issues of squeak and rattle in passenger vehicles due to vehicle-borne vibrations at vehicle, component and subcomponent levels [2, 3, 4, 5, 6, 7, 8].
Technical Paper

Fast, High Resolution Panel Noise Contribution Method

2011-05-17
2011-01-1594
All surfaces of a cabin interior may contribute to the sound pressure at a certain reference position, e.g. the human's ear. Panel noise contribution analysis (PNCA) involves the measurement of the contribution of separate areas. This is an effective method to determine the effect of apparent noise sources at a specific location. This paper presents the latest developments on particle velocity based panel noise contribution analysis. In contrast to the traditional methods, the particle velocity approach is faster; it requires 3 days instead of weeks. While the theoretical base of the procedure in this paper is similar to previously published particle velocity based procedure, here the measurement protocol has now been simplified dramatically, which has reduced the measurement time even more to less than a day. The method and its implementation are explained in the paper and a full measurement procedure is reported.
Technical Paper

Structure Borne Noise and Vibration Reduction of a Sports Utility Vehicle by Body-Mount Dynamic Stiffness Optimization

2011-05-17
2011-01-1599
Among the key parameters that decide the success of a vehicle in today's competitive market are quietness of passenger cabin (in respect of both airborne and structure-borne noise) and low levels of disturbing vibration felt by the occupants. To control these values in body-on-frame construction vehicles, it is necessary to identify major transfer paths and optimize the isolation characteristics of the elastomeric mounts placed at several locations between a frame and the enclosed passenger cabin of the vehicle. These body mounts play a dominant role in controlling the structure-borne noise and vibrations at floor and seat rails resulting from engine and driveline excitations, and they are also a vital element in the vehicle ride comfort tuning across a wide frequency range. In the work described in this paper, transfer path tracking was used to identify root cause for the higher noise and vibration levels of a diesel-powered sports utility vehicle.
Technical Paper

Noise Contribution Analysis at Suspension Interfaces Using Different Force Identification Techniques

2011-05-17
2011-01-1600
Road-tire induced vibrations are in many vehicles determining the interior noise levels in (semi-) constant speed driving. The understanding of the noise contributions of different connections of the suspension systems to the vehicle is essential in improvement of the isolation capabilities of the suspension- and body-structure. To identify these noise contributions, both the forces acting at the suspension-to-body connections points and the vibro-acoustic transfers from the connection points to the interior microphones are required. In this paper different approaches to identify the forces are compared for their applicability to road noise analysis. First step for the force identification is the full vehicle operational measurement in which target responses (interior noise) and indicator responses (accelerations or other) are measured.
Technical Paper

Investing Factors Affecting Door Slam Noise of SUV and Improved Performance by DFSS Approach

2011-05-17
2011-01-1595
Recent development in automobile industries has seen increased customer attention for good door slamming noise. One of the constituent which plays major role in building brand image of vehicle in terms of NVH performance is door slam noise quality. Hence it is very desirable to understand how different door elements radiate sound during a door-closing event and how to optimize a door structure to achieve specific sound target in order to ensure the door closing noise quality, NVH engineers needed to look at contributions from different door subsystems. The use of statistical tools like Six Sigma can further help them to ensure the consistency in results. This paper explains the systematic approach used to characterize different element of door which contributes to the overall door slam noise quality through QFD (Quality Function Deployment) and contribution analysis. The different mechanisms contributing to door slam noise were studied.
Technical Paper

Vehicle Interior Noise and Vibration Reduction Method Using Transfer Function of Body Structure

2011-05-17
2011-01-1692
To reduce interior noise effectively in the vehicle body structure development process, noise and vibration engineers have to first identify the portions of the body that have high sensitivity. Second, the necessary vibration characteristics of each portion must be determined, and third, the appropriate body structure for achieving the target performance of the vehicle must be realized within a short development timeframe. This paper proposes a new method based on the substructure synthesis method which is effective up to 200Hz. This method primarily utilizes equations expressing the relationship between driving point inertance change at arbitrary body portions and the corresponding sound pressure level (SPL) variation at the occupant's ear positions under external force. A modified system equation was derived from the body transfer functions and equation of motion by adding a virtual dynamic stiffness expression into the dynamic stiffness matrix of the vehicle.
Technical Paper

Modeling of Stiffened Panels Using the Energy Finite Element Analysis

2011-05-17
2011-01-1696
Stiffened panels are encountered in many engineering systems since the stiffeners comprise the mechanism which provides support and rigidity to the panel's skin. Either a mechanical excitation or an acoustic load can be applied on a stiffened panel creating vibration that is transmitted in all panel components. Mechanical excitation tends to be localized in nature, originating from operating machinery mounted on the panel, while the acoustic excitation tends to be distributed over the entire panel, since it typically originates from an external acoustic source which creates an acoustic field impinging on the entire panel. In the Energy Finite Element Analysis (EFEA) various degrees of fidelity are possible when modeling the response of a stiffened panel. In this paper, the theoretical background and the corresponding implications associated with each alternative modeling approach are presented first.
Technical Paper

Hybrid Technique for Underbody Noise Transmission of Wind Noise

2011-05-17
2011-01-1700
Wind noise has become an important indicator for passenger automobile quality. Several transmission paths can be related to different parts of the vehicle exterior. While the greenhouse (side glasses, windshield, seals & others) often dominates the interior noise level above 500 Hz, the contribution coming from the underbody area usually dominates the interior noise spectrum at lower frequencies. This paper describes a framework of numerical tools which is capable of determining realistic underbody turbulent and acoustic loads being generated for typical driving conditions, as well as performing the noise transmission through underbody panels and the propagation of sound to the drivers ear location.
Technical Paper

Transmission Loss Prediction of Multilayered Components - A New Impedance Formulation to Take in Account Finite Structural Connection

2011-05-17
2011-01-1715
The sound transmission loss of multilayered structures is commonly used in the building industry to quantify the acoustical performances of walls and rooms, but also in the industry to design car and aircraft components. Multilayered panels are a class of widely diffused components so that prediction models for their acoustical properties are of great importance for designers, especially to limit the number of laboratory tests which may be long, difficult and expensive to accomplish. In practice, however, between leaves in the multilayered components, finite size structural connections (points or lines) normally exist and these are not simple to be considered. Aim of this paper is to determine the equivalent characteristic impedance of a layer and a stud to be used in the classical formulation of the progressive impedance method. Predictions of the proposed method are quite satisfactorily compared with experimental results.
Technical Paper

Understanding the Effect of Spot-Weld/Bolt Joint Distribution on the Sound Radiation from Panel Structures

2011-05-17
2011-01-1723
It is well known that sound radiation from a rectangular panel can be significantly affected by its boundary condition. However, most of the existing investigations are primarily focused on sound radiation from plates with simply supported boundary conditions. The objective of this paper is to study the effect on sound radiation of the boundary supporting conditions generally specified in the form of discrete and/or distributed restraining springs. This will have practical implications. For example, in automotive NVH design, it is of interest to understand how the sound radiation from a body panel can be affected by the number and distribution of spot-welds. It is demonstrated through numerical examples that the distribution of spot-welds can be tuned or optimized, like other conventional design parameters, to achieve maximum sound reduction.
Journal Article

Application of the Hybrid FE-SEA Method to Predict Sound Transmission Through Complex Sealing Systems

2011-05-17
2011-01-1708
Currently, the use of numerical and analytical tools during a vehicle development is extensive in the automotive industry. This assures that the required performance levels can be achieved from the early stages of development. However, there are some aspects of the vibro-acoustic performance of a vehicle that are rarely assessed through numerical or analytical analysis. An example is the modeling of sound transmission through vehicle sealing systems. In this case, most of the investigations have been done experimentally, and the analytical models available are not sufficiently accurate. In this paper, the modeling of the sound transmission through a vehicle door seal is presented. The study is an extension of a previous work in which the applicability of the Hybrid FE-SEA method was demonstrated for predicting the TL of sealing elements.
Technical Paper

Noise Reduction of Electrically Powered Mass Rapid Train by Improving the Contact Conditions between the Rubbing Plates and the Friction Blocks

2009-05-19
2009-01-2094
A noticeable noise and vibration occurred when the Mass Rapid Train turned on a rail with a large turning angle. A study was performed to investigate the source of the noise and vibration, to find the root causes, and to discuss the corrective actions to improve the issue. The investigation indicates the noise occurs between the slewing ring bearing and the friction sets. The slewing ring bearing is located between the body and chassis systems. It provides a relative rotation between the body and chassis. The friction sets provide friction forces to prevent abrupt movements and to help to stabilize the relative motions between the body and chassis systems. The study shows under certain contact conditions unsmooth turning would occur and cause the noise and vibration. A corrective action was suggested to improve the condition.
Technical Paper

A Study of Front Subframe System Optimization for Improving Vehicle NVH Performance

2009-05-19
2009-01-2097
The purpose of this article is to investigate the links between NVH performances of a car such as booming, road noise and dynamic characteristics of its front subframe system. The target of dynamic property of the subframe members was set through a contribution analysis. The Booming noise was refined by improving the structural dynamic stiffness of relevant subframe members and optimizing the dynamic stiffness of subframe mount bushes considering the frequency property of the engine exciting force. In the light of NVH, merits and demerits of a solid mounted subframe for various powertrain types were examined, and several countermeasures such as structural reinforcement, dynamic dampers and dynamic characteristics of A and G bushes were applied and suggested.
Technical Paper

A Comparison of Fiber Wheel Liners on Two Different Vehicles

2009-05-19
2009-01-2106
Identical fiber wheel liners were installed on two different mid size vehicles in order to compare the noise reduction for each vehicle. The fiber liners represented material in current production. A baseline noise level was established with the existing plastic wheel liners and then comparisons were made with fiber wheel liners. Noise levels were compared in the wheel well and in the interior for similar vehicle operating conditions. For both vehicles, significant tire noise reduction at the source was measured with fiber liners compared to plastic liners. One of the vehicles also demonstrated noise reduction in the passenger cabin with fiber liners. Insight into potential explanations for these differences was provided by comparing the noise levels at different locations within the vehicles. The results show how fiber liners are an additional tool to reduce the noise in a vehicle and how the NVH design for the balance of the vehicle can leverage the NVH impact of these parts.
Technical Paper

Application of Hydraulic Body Mounts to Reduce the Freeway Hop Shake of Pickup Trucks

2009-05-19
2009-01-2126
When pickup trucks are driven on concrete paved freeways, freeway hop shake is a major complaint. Freeway hop shake occurs when the vehicle passes over the concrete joints of the freeway which impose in-phase harmonic road inputs. These road inputs excite vehicle modes that degrade ride comfort. The worst shake level occurs when the vehicle speed is such that the road input excites the vehicle 1st bending mode and/or the rear wheel hop mode. The hop and bending mode are very close in frequency. This phenomenon is called freeway hop shake. Automotive manufacturers are searching for ways to mitigate freeway hop shake. There are several ways to reduce the shake amplitude. This paper documents a new approach using hydraulic body mounts to reduce the shake. A full vehicle analytical model was used to determine the root cause of the freeway hop shake.
Technical Paper

Simple Test Method for Squeak & Rattle Evaluation of Door Trim by Using Statically Repeated Loading Robot Arm

2009-05-19
2009-01-2112
Recently, major car maker is specified squeak and rattle test method for subsystems or components by objective method. Generally these test method is focused on vibration environmental conditions. Especially, door trim which is located close to occupant is required additional test for squeak and rattle which is produced by occupant's interaction with door trim. To evaluate this condition, generally it can be tested by subjective method such as striking or pushing and twisting several positions of door trim. Dosing so is very time consuming and including variation results as different decisions. So, this paper suggest a new approach for evaluating squeak and rattle which is relating occupant contacting conditions to interior part, especially interior door trim. Multi-axis robot arm is examined to push automatically several points of door trim.
Technical Paper

Attenuation of Vehicle Noise using Different Trunk Insulation Systems

2009-05-19
2009-01-2122
Attenuation of noise from the rear of a vehicle was evaluated for different trunk insulation systems using a combination of poro-elastic material modeling and a full vehicle SEA model. The model considered the interaction between the trunk and the passenger cabin. The sound absorption coefficients and acoustic impedance for each of the material systems used in the trunk were measured and the poro-elastic Biot properties were calculated to define the acoustic treatments in the SEA model. Several levels of acoustical treatment for the trunk were studied ranging from a trunk with no decorative liner to a trunk with a liner and maximum acoustical treatment. The results show the contribution of the trunk material in reducing cabin noise for different levels of noise originating at the rear of the vehicle. These results demonstrate the value of combining poro-elastic material modeling and SEA models for selecting efficient material systems early in a vehicle design.
Technical Paper

Development of DBW Throttle Body for V4 Engines

2009-11-03
2009-32-0056
For the throttle bodies for sport motorcycles, there is a need for a design giving importance to drivability and precise control. At the same time, various devices such as idle control and duct control are necessary in order to conform to recent environmental regulations. However, these added functions lead to an increase in the number of components, thus leading to disadvantages in both cost and weight. Therefore we have developed a throttle body where DBW (Drive By Wire) has been used to consolidate such parts, and functions. For the drive actuator, a modified actuator device from a passenger car DBW system was incorporated into a multi-cylinder link structure. In addition, specifications such as the gear ratios and the operation torque were optimized in order to satisfy the operability required for motorcycles.
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