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The combination of lightweight design and performant Noise, Vibrations Harshness (NVH) solutions has gained a lot of importance over the past decades. Lightweight design complies with the ever more stringent environmental requirements, however conflicts with NVH performance, as low noise and vibration levels often require heavy and bulky systems, especially at low frequencies. To face this challenge, locally resonant metamaterials come to the fore as low mass, compact volume NVH solutions, beating the mass law in some tunable frequency zones, referred to as stopbands. Metamaterials are artificial materials made from assemblies of unit cells of non-homogeneous material composition and/or topology. The local interaction between unit cells leads to superior performance in terms of noise and vibration reduction with respect to the conventional NVH treatments. Previously the authors showed how wave propagation along one-dimensional structures can be reduced by metamaterial additions.

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.

In many industrial applications, such as in the automotive and machine building industry, there is a continuous push towards lightweight materials motivated by material and energy savings. This increased use of lightweight materials, however, can strongly compromise the Noise, Vibration and Harshness (NVH) performance of the final products. Especially in times where the NVH performance not only receives a higher legislative attention, but also becomes a commercial differentiator, this also represents a key point of attention for designers and directs research activities towards new experimental and numerical techniques to accurately predict the NVH performance of lightweight systems as early as possible in the design process. The presented work discusses novel measurement setup, specifically developed for examining the vibro-acoustic behavior of lightweight structures. The test stand consists of a concrete cavity of 0.83 m₃.

Prediction of the drive-by noise level in the early design stage of an automotive vehicle is feasible if the source signatures and source-receiver transfer functions may be determined from simulations based on the available CAD/CAE models. This paper reports on the performance of a drive-by noise synthesis procedure in which the transfer functions are numerically evaluated by employing the Fast Multipole Boundary Element Method (FMBEM). The proposed synthesis procedure first computes the steady-state receiver contributions of the sources as appearing from a number of vehicle positions along the drive path. In a second step, these contributions are then combined into a single transient signal from a moving vehicle for each source-receiver pair by means of a travel time correction.

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.

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.

Despite the fact that Transfer Path Analysis (TPA) is a well known and widely used NVH tool it still has some hindrances, the most significant being the huge measurement time to build the full data model. For this reason the industry is constantly seeking for faster methods. The core concepts of a novel TPA approach have already been published in a paper at the ISMA 2008 Conference in Leuven, Belgium. The key idea of the method is the use of parametric models for the estimation of loads. These parameters are frequency independent as opposed to e.g. the classical inverse force identification method where the loads have to be calculated separately for each frequency step. This makes the method scalable, enabling the engineer to use a simpler model based on a small amount of measurement data for quick troubleshooting or simply increase accuracy by a few additional measurements and using a more complex model.

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.

OEM's increase the pressure on their suppliers to design, develop and test their products within a short time period. This requires design ‘first-time-right’ philosophy and advanced numerical and experimental methods. Four steps are required to experimentally asses the durability of exhaust systems. Environmental loads and strain references are acquired on the test track. This data is analyzed and damaging are sections retained. These sections are then reproduced on a test rig. During this reproduction, strain is measured at the reference locations and the damage is calculated and compared with the test track data.

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.

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 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 this paper, singular value decomposition, principle component analysis and multicoherence analysis is used to evaluate the number of important degrees of freedom in acceleration based road load data, which constitute the targets for road reproduction experiments on a hydraulic shaker table. It is therefore important to determine from this road data how many degrees of freedom need to be included in the road reproduction experiments. The multi-axial nature of the input and the suspension response is illustrated based on target data from different road surfaces, acquired on the road and on the road dynamometer, as well as on the reproduction results of these tracks using tire patch and spindle based excitation on the K.U.Leuven high frequency multi-axial shaker table.

While CAE methods allow improving nominal product design using virtual prototypes, uncertainty and variability in properties and manufacturing processes lead to scatter in actual performances. Uncertainty must hence be incorporated in the CAE process to guarantee the robustness and reliability of the design. This paper presents an overview of uncertainty-based design in automotive and aerospace engineering. Fuzzy methods take uncertainty into account, whereas reliability analysis and a reliability-based design optimization framework can deal with variability. Key enabling technologies to alleviate the computational burden, such as workflow automation, substructuring and design of experiments, are discussed, and industrial applications are presented.

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.

A CUBE™ high frequency 6-DOF shaker table has recently been installed at the KULeuven Vehicle Technologies Laboratory. This paper describes a dual hardware-software approach for increased accuracy of Multi-Degree-Of-Freedom (MDOF) road reproduction experiments. On the KULeuven 6-DOF high-frequency shaker table, the hardware is calibrated using a mobile Coordinate Measuring Machine (CMM) and both hardware and software settings are tuned for better accuracy. In addition, a modified Time Waveform Replication (TWR) algorithm is presented that yields more stable control and reduction of unwanted rotations.