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Sunroof is placed in certain high-end vehicles to give user a better driving experience. All automakers are searching alternatives to reduce weight and cost in the vehicle, in which sunroofs are also impacted. Some alternatives are already applied, as a honeycomb paper used in some sunshades that presents benefits, as less weight and with a good cost reduction. Although, due the reduced weight for this part produced in this material, it shows more susceptibility to reproduce the vibration that vehicle propagates in movement, especially in bad condition roads. The sunroof assembly is dependent of the roof reinforcement and roof skin, but in this special case, the validation could be done in the components itself because the interaction of the sunshades is directly dependent of the other sunroof parts, as rails and front frame.

Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation. This paper has two objectives: 1) Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined. 2) Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.

NVH targets for future vehicles are often defined by utilizing a competitive benchmarking vehicle in conjunction with an existing production and/or reference vehicle. Mode management of full vehicle modes is one of the most effective and significant NVH strategies to achieve such targets. NVH dynamic characteristics of a full vehicle can be assessed and quantified through experimental modal testing for determination of global body mode resonance frequency, damping property, and mode shape. Major body modes identified from full vehicle modal testing are primarily dominated by the vehicle's body-in-white structure. Therefore, an estimate of BIW modes from full vehicle modes becomes essential, when only full vehicle modes from experimental modal testing exist. Establishing BIW targets for future vehicles confines the fundamental NVH behavior of the full vehicle.

NVH refinement of passenger vehicles is crucial to customer acceptance of contemporary vehicles. This paper describes the vehicle NVH development process, with specific examples from a Diesel sedan application that was derived from gasoline engine-based vehicle architecture. Using an early prototype Diesel vehicle as a starting point, this paper examines the application of a Vehicle Interior Noise Simulation (VINS) technique in the development process. Accordingly, structureborne and airborne noise shares are analyzed in the time-domain under both steady-state and transient test conditions. The results are used to drive countermeasure development to address structureborne and airborne noise refinement. Examples are provided to highlight the refinement process for “Diesel knocking” under idle as well as transient test conditions. Specifically, the application of VINS to understanding the influence of high frequency dynamic stiffness of hydro-mounts on Diesel clatter noise is examined.

The Frequency Response Function (FRF) is a fundamental component to identifying the dynamic characteristics of a system. FRF's have a significant impact on modal analysis and root cause analysis of NVH issues. In most cases the FRF can be easily measured, but there are instances when the measurement is unobtainable due to spatial constraints. This paper outlines a simple experimental method for obtaining a high quality input-output FRF of a structure in areas where an impact hammer can not reach during impact testing. Traditionally, the FRF in such an area is obtained by using a load cell extender with a hammer impact excitation. A common problem with this device is a double hit, that yields unacceptable results.

In the development of several outside mirror designs for vehicles, a high frequency noise (whistling) phenomenon was experienced. First impression was that this might be due to another source on the vehicle (such as water management channels) or a cavity noise; however, upon further investigation the source was found to be the mirror housing. This “laminar whistle” is related to the separation of a laminar boundary layer near the trailing edges of the mirror housing. When there is a free stream impingement on the mirror housing, the boundary layer starts out as laminar, but as the boundary layer travels from the impingement point, distance, speed, and roughness combine to trigger the transition turbulent. However, when the transition is not complete, pressure fluctuations can cause rapidly changing flow patterns that sound like a whistle to the observer. Because the laminar boundary layer has very little energy, it does not allow the flow to stay attached on curved surfaces.

Noise and vibration signals which are stationary are frequently analyzed for frequency content using Fourier Transform methods. Frequency content can be clearly displayed, but temporal characteristics of signals can easily be obscured in a frequency spectrum. Several commonly available methods of analyzing nonstationary signals are available, such as short-time Fourier Transform and wavelet analysis. Smearing of data in the time and/or frequency domains leads to limited usefulness of these methods in analyzing rapidly varying signals. This also applies to stationary signals with perceivable temporal characteristics. The Wigner Distribution is a time-frequency analysis which can analyze rapidly varying signals and show the effects of rapid changes in signal characteristics. It is appealing because it fully preserves all the information present in the original signal.

Internal combustion engine noise and vibration are major issues for car makers, and these are even more important for High-Level Pick-ups and SUV's which applies modern diesel engines. One important player in this scenario is the second-order unbalanced forces vibration produced by the conventional in-line 4-cylinder engine configurations, which leads to high-frequency excitation of vehicle's structure and consequent internal noise. This paper studies a balancer shaft solution for the mentioned engine configuration, as well as major design alternatives and development process and issues. This paper also presents an example of a balancer shaft design and development for a high speed diesel engine, as well as proposes a design/decision matrix methodology. Such methodology, which can be applied to any design or engineering case, helps design engineers make the right decision amongst different options by using a very simple and objective matrix.

Vehicle audio system performance is an important attribute for final customers. Usually the system performance is evaluated by subjective judgments and also some sort of objective measurements, as for example: reverberation time measurement of the internal cabin, frequency response and harmonic distortion. But all of these measurements are performed by the automaker at vehicle level - with audio system and speakers installed inside the vehicle cabin - for general quality inspections and definition of some spatial parameters of internal trim design. Loudspeaker performance evaluation usually requires great amount of investments due to the acoustic chamber requirements.

The use of time selective techniques has been used for years in signal processing for acoustic, vibration and electro-acoustic to make simulated free-field measurements. Many acoustic solutions have been implemented and developed by specialized software companies and are offered to final users by the costs of large amounts of money. However, recent advances in hardware, software and data acquisition systems - allied to a good background in signal processing - has enabled the implementation of fast and practical solutions to more complex problems involving direct signal manipulations, analysis and post-processing.

Improving vehicle crash, NVH and metal fatigue performance using expanding polymeric foams can be achieved with a systematic approach. By employing a systematic approach with expandable epoxy foams and alternative carriers, the product development process can be significantly reduced. As a result, high strength and lightweight solutions can be designed to improve the structural performance of today's vehicles. This technical paper will examine the key steps in utilizing a systematic approach to selecting, designing and modeling structural expandable epoxy foam solutions used in conjunction with metallic and non-metallic carriers. A review of material properties, alternative designs and finite element modeling methods will allow for a thorough understanding of how expandable epoxy foams can meet the demanding challenges for improved occupant safety, reduced interior noise levels and increased durability at a reduced vehicle weight.

Buffeting is a wind noise of high intensity and low frequency in a moving vehicle when a window or sunroof is open and this noise makes people in the passenger compartment very uncomfortable. In this paper, side window buffeting was simulated for a typical SUV using the commercial CFD software Fluent 6.0. Buffeting frequency and intensity were predicted in the simulations and compared with the corresponding experimental wind tunnel measurement. Furthermore, the effects of several parameters on buffeting frequency and intensity were also studied. These parameters include vehicle speed, yaw angle, sensor location and volume of the passenger compartment. Various configurations of side window opening were considered. The effects of mesh size and air compressibility on buffeting were also evaluated. The simulation results for some baseline configurations match the corresponding experimental data fairly well.

One of the major NVH concerns for automobile manufacturers is the response of a vehicle to the impact of the tire as it encounters a road discontinuity or bump. This paper describes methods for analyzing the impact response of a vehicle to such events. The test vehicle is driven on a dynamometer, on which a bump simulating cleat is mounted. The time histories of the cleat impact response of the vehicle can be classified as a transient and a repeated signal, which should be processed in a special way. This paper describes the related signal processing issues, which include converting the time data into a continous spectrum, determination of the correct scaling factor for the analyzed spectrum, and smoothing out harmonics and fluctuations in the signal. This procedure yields a smooth frequency spectrum with a correctly scaled amplitude, in which the frequency contents can be easily identified.

The damping loss factor of a structural panel plays a significant role in its vibro-acoustic performance. The objective of this paper is to present a new procedure for evaluating the damping loss factors of these panels. Traditionally, the damping loss factors are determined by using the decay rate of the decay curves which are experimentally obtained from the structure. However, this is time consuming and the accuracy is limited by fluctuations in the decay curve. In this paper, the envelope signal of each decay curve is determined through its Hilbert transform, and the remaining small fluctuations in the envelope signal are further smoothed out by the exponential average method. Finally, the damping loss factor is estimated based on the smoothed envelope signal of each decay curve. A computer program has been developed to implement this procedure. It is shown that this procedure improves both accuracy and efficiency of the decay rate method for estimating damping loss factor.

Under the constraints of improved vehicle refinement, automotive OEMs are challenged to improve vehicle noise, vibration and harshness (NVH) characteristics, reduce vehicle weight, and streamline manufacturing and assembly processes. In support of these objectives, alternate methods of vehicle noise control are being investigated. This paper will address one area where alternate material strategies are being investigated to meet these requirements. Floorpan damping treatments are a primary component of the overall vehicle noise package. This paper will investigate three floorpan damping treatments. Comparisons will be made between asphaltic melt sheets, constrained layer dampers, and spray-on dampers. Performance of these treatments will be measured using laboratory methods and will feature a case study using a Body-In-White (BIW) to demonstrate performance of the different materials.

A variety of expandable sealants are used to fill vehicle body cavities to impede noise, water, air, and dust from entering (and exiting) the passenger compartment. This paper compares three sealant technologies used for filling body cavities. The technologies are rubber-based elastomeric preformed parts; thermoplastic elastomeric preformed parts, and two-component polyurethane that is foamed-in-place directly in the vehicle body cavity. The following comparisons are made between the three technologies: application methods and issues, cost, material properties and acoustical performance.

The work carried out with external noise insulation has been demanding high importance in vehicle concept since the second External Noise Regulation in Brazil (Conama 001/ 1993). The engineering effort shall increase significantly for near future developments due to the new Regulation (Conama 272 / 2000) with more stringent limits. The effect over vehicle systems beyond noise requirements is not restricted to the addition of shields and insulators. The airflow restriction created by the noise shields surfaces may become a huge cooling issue. This situation is usually observed on trucks designed for tropical markets and submitted to severe environments. Lessons learned in a current development are the basis of the proposed methodology. Vehicle and lab sound intensity noise source ranking tests are suggested as development tools. The paper also presents a pass-by-noise development strategy that includes CAE airflow and cooling management tools.

Sound quality targets for new vehicles are currently specified by jury evaluation techniques based upon listening studies in a sound laboratory. However, jury testing is costly, time consuming and at present there are no methods to include customer expectations or brand requirements. This paper describes a neural computing approach that is being developed to generate knowledge and tools to enable objective measures of a product's sound to be converted into a prediction of the subjective impression of potential customers without carrying out the traditional jury evaluation tests.

This paper dis cusses the development of a nonlinear shock absorber model for low-frequency CAE-NVH applications of body-on-frame vehicles. In CAE simulations, the shock absorber is represented by a linear damper model and is found to be inadequate in capturing the dynamics of shock absorbers. In particular, this model neither captures nonlinear behavior of shock absorbers nor distinguishes between compression and rebound motions of the suspension. Such an inadequacy limits the utility of CAE simulations in understanding the influence of shock absorbers on shake performance of body-on-frame vehicles in the low frequency range where shock absorbers play a significant role. Given this background, it becomes imperative to develop a shock absorber model that is not only sophisticated to describe shock absorber dynamics adequately but also simple enough to implement in full-vehicle simulations. This investigation addresses just that.

Laminated steel sheets sandwiched with a polymer core are increasingly used for automotive applications due to their vibration and sound damping properties. However, it has become a major challenge in finite element modeling of laminated steel structures and forming processes due to the extremely large differences in mechanical properties and in the gauges of the polymer core and the steel skins. In this study, circular cup deep drawing and V-bending experiments using laminated steels were conducted in order to develop a modeling technique for laminate forming processes. The effectiveness of several finite element modeling techniques was investigated using the commercial FEM code LS-Dyna. Furthermore, two production parts were selected to verify the modeling techniques in real world applications.