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This paper presents a study on using rubber bushing as a sensor for the identification of forces transmitted onto the car body. The method starts from the idea that the transmission forces can be related to the deformation of the rubber bushing multiplied by its stiffness. Deformation of the rubber bushing is estimated from relative vibrations across the bushing. Simple theories are presented to deal with modeling of the rubber bushing and processing of the vibration mesurements on the link and car body to identify the transmission forces. Then, validity of the proposed approach is shown by applications to a suspension system under several driving conditions.

This paper reviews the philosophy of large-data-acquisition-system design as it has evolved over the past 20 years and discusses recent developments in applicable hardware and software tools. PIRANHA, a 320-channel system that embodies many of the features discussed and takes advantage of the new technologies, is described.

Five examples of HMIs, Human Machine Interfaces, (formerly Man-Machine-Interfaces) are presented to illustrate the variety of operating solutions for computer-aided dynamic data acquisition systems. The examples range from a simple on-off control with a simple terminal -type interface for a sophisticated instrumentation recorder to a 384-channel automated Wind Tunnel test system. The design challenges, the evolution from GUI’s to HMI’s, the potential pitfalls and benefits of software-based HMI’s and a means to speed development and to get timely end-user input are covered.

Because of the recent trend for testing products in multi- directions and to higher and higher frequencies there is a need to develop excitation systems with high natural frequencies, i.e. having a stiff construction with small moving mass(es). In this work, a 3- degree of freedom (DOF) excitation mechanism with closed-chain kinematics is proposed that can satisfactorily fulfill these requirements. Closed loop control allows this device to be used for testing parts under realistic combined loads that include not only vertical but also two axial horizontal loads. The 6-degree of freedom version of such device can, in addition to 3 axial forces, also load a part with 3 moments. The use of this device can be extended to active vibration control applications such as active seats for off-road vehicles.

A significant challenge in successful implementation of large channel count dynamic test systems, like multi-channel modal systems, has been efficient and error free test set-up and data collection. Newly developed instrumentation that digitally communicates self-identifying information (including transducer type and serial number, calibration value and physical location) greatly enhances system performance and drastically reduces the opportunity for human documentation errors. Sensors featuring this Transducer Electronic Data Sheet (TEDS, consistent with the impending IEEE P1451.4 standard), in addition to such techniques as sonic digitization for geometry definition and automated data acquisition with computer controlled, bank switching signal conditioners are continually improving accuracy and reducing the per channel price of multi-channel dynamic test systems.

The objective of the present work was to establish a correlation between steering pump cam ring profile location and steering system performance for noise, vibration and harshness (NVH). Once this correlation was established, the secondary objective was to determine acceptable cam profile position tolerances from the standpoint of NVH performance. These objectives were accomplished through the use of binaural measurement and jury evaluation of vehicle interior noise. Cam rings were manufactured for this study with profiles shifted a predetermined distance away from the nominal position. These cams were built into steering pumps and these pumps were in turn installed in a vehicle. Vehicle interior noise and pump housing vibration measurements were made to quantify the steering system noise performance associated with each cam ring. The interior noise recordings were played back for a jury comprised of engineers familiar with steering system noise.

In order to optimise the vibro-acoustic behaviour of panel-like structures in a more systematic way, accurate structural models are needed. However, at the frequencies of relevance to the vibro-acoustic problem, the mode shapes are very complex, requiring a high spatial resolution in the measurement procedure. The large number of required transducers and their mass loading effects limit the applicability of accelerometer testing. In recent years, optical measuring methods have been proposed. Direct electronic (ESPI) imaging, using strobed continuous laser illumination, or more recently, pulsed laser illumination, have lately created the possibility to bring the holographic testing approach to the level of industrial applicability for modal analysis procedures. The present paper discusses the various critical elements of a holographic ESPI modal testing system.

The Percentile Frequency method originated in an attempt to quantify the frequency content of door slam sounds. The method is based on the Specific Loudness Patterns of Zwicker Loudness. Zwicker states that the area of the Specific Loudness Pattern is proportional to the total loudness. The method summarizes each Pattern as seven frequencies identifying the contributions of fixed percentages of the total area (i.e. 10%, 20%, 30%, 50%, 70%, 80% and 90%). Applying the method to each Pattern in a time series generates a family of curves representing the change in relative frequency content with time. The process, in effect, normalizes the frequency content of the impulse for loudness and reduces the data to a two dimensional plot. On a Percentile Frequency plot a simple impulse appears as a pattern of “nested, inverted check marks.” More complicated impulses, such as rattles, have more complicated shapes that are still “nested” together.

This paper focuses on psychoacoustical experiments for the assessment of roughness by using vehicle interior noise. The experimental design is carried out carefully to derive reliable data for further analysis with objective parameters. Apart from the acoustical properties of the recording/playback system the different meanings of the word roughness are taken into account, because each person has its own interpretation of ‘roughness’ differing between the phenomenons of roughness, r-roughness, rumble, harshness, fluctuation strength, etc.. An important preparation for psychoacoustical experiments is a clear definition of the sound attribute under investigation by using typical examples. Furthermore, accidental influences of other psychoacoustical parameters like the influence of loudness have to be avoided.

In this paper an algorithm is developed for combining finite element analysis and boundary element techniques in order to compute the noise radiated from a panel subjected to boundary layer loading. The excitation is presented in terms of the auto and cross power spectral densities of the fluctuating wall pressure. The structural finite element model for the panel is divided into a number of sub-panels. A uniform fluctuating pressure is applied as excitation on each sub-panel separately. The corresponding vibration is computed, and is utilized as excitation for an acoustic boundary element analysis. The acoustic response is computed at any data recovery point of interest. The relationships between the acoustic response and the pressure excitation applied at each particular sub-panel constitute a set of transfer functions.

An easy-to-use computer program for ride analysis was recently developed. The result of this effort-RideSim- predicts time history responses, power spectral density (PSD) functions, and a driver oriented measure of ride comfort. RideSim employs a graphical user interface (called SGUI, for simulation graphical user interface) to control data preparation, simulation execution, animation, and data analysis. The SGUI allows the user to operate the program by pointing and clicking with a mouse, rather than by using cumbersome text commands. It also manages the vehicle dynamics parameters, the resulting simulation output, and results of post-processing analyses (i.e., PSD analysis). The vehicle dynamics model was generated with the AUTOSIM multibody dynamics program. This program uses Kane’s Method and computer algebra to create a parametric dynamics simulation that can be easily linked to the SGUI.

A structural-acoustic finite-element model of an automobile trimmed-body is developed and experimentally evaluated for predicting body vibration and interior noise for frequencies up to 200 Hz. The structural-acoustic model is developed by coupling finite element models of trimmed-body structure and the passenger-compartment acoustic cavity. Frequency-response-function measurements of the structural vibration and interior acoustic response for shaker excitation of a trimmed body are used to assess the accuracy of the structural-acoustic model.

This paper reports on test-analysis correlation and model updating activities carried out in the context of the European research project “HPC-VAO” (ESPRIT Project nr 20074, High Performance Computational environment for Vibro-Acoustic Optimisation). The central aim of the project is the implementation of a state-of-the-art CAE environment to support design optimisation in the field of NVH engineering. A specific objective covers the validation of the simulation models that are used in the vibro-acoustic optimisation framework. The validity and reliability of these models can be drastically improved by application of ‘model updating’ techniques. Whilst much research has been done in this field in the last decade, the number of cases where the technique has been used on industrial applications are slowly but steadily growing.

A method for applying soap film geometry to an automobile body structure has been developed. Its curved surface reduce both interior noise and damping material application because of its high rigidity and uneven deformation mode. This paper demonstrates these mechanism, benchmarks their performance with conventional flat and bead panels and presents an application to the floor panel of an automobile body.

Measurement of sound intensity techniques has very good application in the source identification of a particular noise character. It has been applied effectively along with modal analysis and FE experimental excitation techniques to find out root cause of a particular noise character in small gasoline engine. A FEM shell model was used to make cylinder block and cylinder head model. FEM simulation was carried out which matched with experimental results. It helped to remove the noise character from engine. The other part of the paper describes the noise reduction of the crankcase cover used for the same motorcycle. It houses crankcase as well as two speed gearbox. The methodology involves very effective combination of experimental harmonic analysis, FE model with the shell element for the 3 piece crankcase cover, and experimental measurements. A particular sequence of this experimental techniques along with computer simulation techniques gives extremely good results.

At low frequencies, the finite element method reliably predicts the dynamic response of structures. At high frequencies where modal density is high, statistical energy analysis (SEA) is a useful tool to determine the global dynamic behavior of the structures. SEA gives only the space frequency band averaged energy for each subsystem. In the mid-frequency range where both short and long waves are present, neither low nor high frequency approximation to the dynamic response is valid. In this frequency range, there is a need to utilize another technique to capture the dynamic response of the structure. In this study, the energy finite element analysis (EFEA) method is evaluated as a possible technique to close the mid-frequency analysis gap related to NVH analyses. EFEA gives spatial variations of energy density and power in each subsystem, and models localized damping treatment and localized power input.

An improvement in a vehicle's front of dash barrier assembly's acoustical performance has in the past been addressed by both adding individual absorbers and increasing the overall weight of the dash sound barrier assembly. Depending upon the target market of the vehicle, adding mass may not be an option for improved acoustical performance. Understanding the value of an increase in vehicle mass and / or cost for a specific level of improved acoustical performance continues to plague both Original Equipment Manufacturer (OEM) Engineers and Purchasing representatives. This paper examines the importance of properly sealing the front of dash pass-through areas and offers recommendations which can improve the overall vehicle acoustical performance without the addition of cost and mass to the vehicle.

Until recently, the positioning of loudspeakers in a car was based on a combination of experience and empirical studies carried out relatively late in the vehicle development cycle when the choice of speaker package space, and hence audio system performance, may have already been severely compromised. This paper describes how a Boundary Element Analysis (BEA) model can be used to establish the best location for low frequency ‘woofer’ loudspeakers at the early stages of an automotive audio system design and for ‘trade off’ studies prior to physical prototypes. The model generates virtual sounds, which can be used in listening studies to assess the quality of the model and to optimize the whole audio system. This paper presents the Computational, Experimental and Auralisation work involved in this project.

A reliable finite element model (FE model) for the suspension of front-engine front-wheel-drive vehicles (FF vehicle) was developed. The model allows analysis which clarifies the role of each suspension component for road noise reduction in the 130- 160 Hz range. To analyze road noise up to 200 Hz, an accurate suspension FE model including tire FE model was developed. All suspension components are modeled in detail by shell or solid element. This saves the validation of model and enables us to use it early in the design stage. To save calculation time, some suspension components in which structure is not a concern are transformed into modal model. To acknowledge each subsystem's role to the entire suspension system a new approach was introduced. In this approach, important internal forces between subsystems are selected. These internal forces have high contribution to transmissibility forces at the body attachment point (body transmissibility force).

A full tracked vehicle model is developed with the objective of providing new capabilities in modeling track and suspension system dynamic response. This capability is essential for predicting the durability of the track as well as the vibration transmission to the interior of the vehicle. In this model, the track is represented as a continuous elastic member with longitudinal (stretching) and transverse track response described using low-order vibration modes. This modeling approach captures dynamic effects with few degrees of freedom relative to established multi-body dynamic formulations. Using this method, a full vehicle model involving relatively few degrees of freedom is assembled for an example military tank. A mixed Eulerian/Lagrangian description is employed wherein the rigid-body elements of the hull and suspension are coupled to component modes of the track spans.