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The continuous pursuit for lighter, more affordable and more silent cars, has pushed OEMs into optimizing the design of car components. The different panels surrounding the car interior cavity such as firewall, door or floor panels are of key importance to the NV performance. The design of the sound packages for high-frequency airborne input is well established. However, the design for the mid-frequency range is more difficult, because of the complex inputs involved, the lack of representative performance metrics and its high computational cost. In order to make early decisions for package design, performance maps based on the different design parameters are desired for mid-frequencies. This paper presents a framework to retrieve the response surface, from a numerical design space of finite-element frequency sweeps. This response surface describes the performance of a sound package against the different design variables.

This paper presents a newly developed hybrid simulation technique for uncoupled acoustic analysis of interior cavities. This method applies a Wave Based model for a large, geometrically simple portion of the acoustic cavity. The superficial details of the problem domain are modeled using a modally reduced finite element model. The resulting hybrid model benefits from the computational efficiency of the Wave Based Method, while retaining the Finite Element Method's ability to model the actual geometry of the problem in great detail. Application of this approach to the analysis of a moderately simplified acoustic car cavity shows the improved computational efficiency as compared to classical finite element procedures and illustrates the potential of the hybrid method as a powerful tool for the analysis of three-dimensional interior acoustic systems.

This paper presents the development of a structural model for passenger car tyres, based on a three-dimensional flexible ring on an elastic foundation. The ring represents the belt and the elastic foundation represents the tyre sidewall. The tyre model, which is implemented as a finite element model, is valid below the first treadband axial bending mode and includes a definition of the wheel flexibility and air cavity. The eigenfrequencies predicted by the model are within 5% of the measured eigenfrequencies. The model is validated by comparing predicted with measured responses for both an unloaded and loaded tyre.

This paper presents the design and experimental results of a novel test setup to measure the road impact response of a rotating tire. The test setup is based on a tire on tire principle and is used to analyse mechanisms of tire/road noise during road impact excitations, such as driving on cobbled roads, joints of a concrete road surface, railroad crossings,… A series of test are performed with different driving speeds, cleat dimensions and inflation pressures. Radiated noise, vibrations of the tire surface and spindle forces are measured on the test setup during impact excitations.

In current practice, tire development and testing are typically experimentally driven. However, as the need to simultaneously optimize multiple noise vibration and harshness (NVH) performance criteria increases and development cycles become shorter, predictive numerical simulation techniques are becoming necessary. In addition, many tire performance areas are coupled and therefore the experimental approach often lacks detailed insights which numerical simulations can provide. Currently, no industrially applicable fully predictive high-fidelity numerical approach that incorporates the use of nonlinear Finite Element (FE) tire models for NVH design is available in literature. Therefore, a fully predictive numerical simulation approach that predicts the rolling of a tire over a coarse road surface is described in this work. The proposed approach allows to predict the dynamic contact- and hub forces that arise during rolling without the need for experimental data.

A key element to bring research advances on intelligent materials to industrial use is that the product CAE models must support such solutions. This involves modeling capabilities for intelligent material systems, sensor and actuator components, control systems as well as their integration in system-level application designs. The final result will then be a multi-attribute optimization approach integrating noise and vibration performance with reliability, durability and cost aspects. As no single integrated solution will fulfill all requirements of the various material and control approaches, the focus of the research is on the use, combination and extension of existing codes and tools.

In the context of the reduction of traffic-related noise the research reported in this paper provides tools that could be used to develop low noise tyres. Two measurement techniques have been analyzed for exterior noise radiation characterization of a loaded rotating slick tyre on a rough road surface. On one hand sound pressure measurements at low spatial resolution with strategically placed microphones on a half-hemisphere around the tyre/road contact point have been performed. This technique provides a robust solution to compute the (overall) sound power level. On the other hand sound intensity measurements at high spatial resolution by means of a scanning intensity probe have been performed. This technique allows a more detailed spatial visualization of the noise radiation and helps in getting more insight and better understanding of the acoustical phenomena.

The NVH optimization of new vehicle models can in principle only be carried out in a relatively late stage of the development process, when the geometrical data (CAD) are available and can be used to generate detailed Finite Element (FE) models of the car body. Unfortunately, in this stage of the development process most of the geometrical data are already fixed and countermeasures are limited and expensive. In order to be able to evaluate design concepts in an earlier conceptual stage of the development process existing models of similar predecessor vehicles must be used leading to techniques such as “mesh-morphing” or “concept modelling” (see for instance [1, 2]). Here, a different approach is investigated based on a substructuring technique.

The identification of the contributions of airborne noise sources in vehicles in operational driving conditions is still a cumbersome task. Whereas the measurement of the transfer path from possible noise sources to the observer ear locations is efficient and accurate in most conditions, the source strength identification is still a challenging task. This paper presents the basic concepts of a new source quantification technique based on acoustic pressure measurements close to the operating sources. The main goal of developing a new technique is to achieve a faster and more economic method as compared to existing methods.

This paper proposes a specific parametric model order reduction (pMOR) scheme for the efficient evaluation of beam based structures. The model to be parameterized is a Finite Element (FE) model that represents a generic network of beams with a number of distinct cross-section types. The methodology considers geometrical parameters that describe the cross-section and the material properties of the beams as the design parameters of interest. An affine representation of the model is derived based on the description of the deformation of a uniform beam. This affine representation can be exploited for the hyper-reduction where the evaluation cost of the system matrices is reduced. The reduction of the system matrices is obtained through a projection based approach. For a given number of parameter combinations a modal basis is constructed. A global reduced order basis (ROB) is obtained through a principal component analysis of these local bases.

Tire noise has become a predominant contributor in many traffic noise situations nowadays and hence, the demand for accurate tire noise prediction models is high. A rolling tire is experimentally characterized by means of the substitution monopole technique: the running tire is substituted by the non-operating tire covered by monopoles. All monopoles have mutual phase relationships and a well defined volume velocity distribution which is derived by means of an inverse Airborne Source Quantification technique; i.e. by combining static transfer function measurements with operational indicator pressure measurements close to the rolling tire. Models with varying amounts and locations of monopoles are discussed.

Maximizing the acoustic attenuation is one of the important design criteria of automotive exhaust systems. Although both analytical and numerical approaches exist to evaluate the acoustic transmission properties of exhaust systems, they are, at present, insufficient to model the full geometrical complexity and to accurately assess the influence of thermal and aerodynamic phenomena onto the acoustic attenuation characteristics. For this reason, an experimental test campaign is often still indispensable to evaluate the aeroacoustic performance of exhaust systems. One of the most commonly used experimental characterization techniques for flow duct systems is the two-port characterization.

Experimental modal analysis (EMA) is a measurement technique to assess the dynamical properties of mechanical components and systems in various phases of their life cycle, e.g. for design, end-of-line testing and health monitoring. The most common EMA uses accelerometers, which provide high frequency acceleration measurements at a few discrete locations. However, attached accelerometers may alter the systems mass and damping properties and multiple tests are required to obtain spatially dense information. To overcome these issues, in this paper we use high-speed cameras and video processing algorithms. In fact, cameras as contact-less sensors do not modify the dynamics of the system under test. Furthermore, cameras provide full-field displacement data, allowing to obtain spatially dense transfer functions with a single excitation, which reduces the experiment duration.

Lightweight structures and designs have been widely used in a number of engineered structures due to ecological and environmental aspects. Nonetheless, lightweight structures typically experience a reduced noise and vibration reduction performance as a consequence of their increased stiffness-to-mass-ratio. To enhance it, novel low mass and compact countermeasures are often sought to address the challenges of achieving not only a good Noise, Vibrations and Harshness (NVH) reduction performance but also maintaining a lightweight design. Recently, locally resonant metamaterials have emerged and shown potential as a lightweight noise and vibration solution with a superior performance in tunable frequency ranges, known as stop bands i.e. frequency regions where free wave propagation is not allowed. These can be achieved by assembling resonant elements that are tuned to the targeted frequency range onto a host structure.

In tire development, the dynamic tire-road contact forces are an important indicator to assess structure-borne interior cabin noise. This type of noise is the dominant source in the frequency range from 50-450 Hz, especially when rolling with constant angular velocity on a rough road. The spatial force distribution is difficult or sometimes even impossible to simulate or measure in practice. So, the use of an inverse technique is proposed. This technique uses response measurements in combination with a digital twin simulation model to obtain the input forces in an inverse way. The responses and model properties are expressed in the time domain, since it is specifically aimed to trace back the impact locations from road surface texture indents on the tire. In order to do so, the transient responses of the travelling waves as a result of these impacts is used. The framework expresses responses as a convolution product of the unknown loads and impulse response measurements.

One dimensional linear acoustics network models are commonly used for the acoustic design of intake and exhaust systems. These models are advantageous since they allow the characterization of the scattering matrices for individual elements, independent of the upstream or downstream components. For an intake or exhaust assembly, the individual elements can be combined by a simple multiplication of the individual matrices to assess the propagation characteristics of the whole system under consideration. The determination of the scattering matrix coefficients can be carried out in an analytical, numerical or experimental way. Since the analytical methodologies are limited to uniform or simplified mean flow representation and the experimental two-port determination is expensive and time-consuming, a numerical method using the time domain Linearized Euler Equations is proposed in this paper.

The investigation of critical noise sources on pass-by noise tests is demanding development of the current techniques in order to locate and quantify these sources. One recent approach is to use beamforming techniques to this purpose. The phased array information can be processed using several methods, for example, conventional delay-and-sum algorithms, deconvolution based algorithms, such as DAMAS, and more recently, the generalized inverse beamforming. This later method, presents the advantage of separating coherent sources with better dynamic range than conventional beamforming. Also, recent developments, such as Iteratively Re-Weigthing Least Squares, increases the localization accuracy allowing it to be used in a challenging problem as a fast moving source detection, a non-stationary condition. The work will raise the main advantages and disadvantages on this method using a practical case, a passenger vehicle pass-by test.

Vibration testing is often carried out for automotive components to meet guidelines based on their operational environments. This is an iterative process wherein design changes may need to be made depending on an intermediate model’s dynamic behavior. Predicting the behavior based on modifications in boundary conditions of a well-defined numerical model imparts practical insights to the component’s responses. To this end, application of a general method using experimental free-free condition frequency response functions of a structure is discussed in the presented work. The procedure is shown to be useful for prediction of responses when kinematic boundary conditions are applied, without the need for an actual measurement. This approach is outlined in the paper and is applied to datasets where dynamic modifications are made at multiple boundary nodes.

Active vibration reduction for lightweight structures has attracted more and more attention in automotive industries. In this paper, reduced-order controllers are designed based on H∞ techniques to realize vibration reduction. A finite element model of piezo-based smart structure is constructed from which a nominal model containing 5 modes and validation model containing 10 modes are extracted. A mixed-sensitivity robust H∞ controller is firstly designed based on the nominal structural model. Considering the ease of controller deployment, an order reduction for the controller is then exploited using balanced truncation method. The effectiveness of the reduced-order controller is finally verified on the validation model via system simulations.

Stringent regulations for CO2 emissions and noise pollution reduction demand lighter and improved Noise, Vibration Harshness (NVH) solutions in automotive industries. Designing light, compact and, at the same time, improved NVH solutions is often a challenge, as low noise and vibration levels often require heavy and bulky additions, especially to be effective in the low frequency regime. Recently, locally resonant metamaterials have emerged among the novel NVH solutions because of their performant NVH properties combined with lightweight and compact design. Due to the characteristic of stop band behavior, frequency ranges where free wave propagation is inhibited, metamaterials can beat the mass law, be it at least in some tunable frequency ranges. Previously the authors demonstrated how metamaterials can reduce the vibrations in a simplified shock tower upon shaker excitation. In this work, the authors apply the metamaterial concept on the real rear shock towers of a vehicle.