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A performative framework is developed for extensive parameter variations of vehicle vibroacoustic finite element models. It employs a fully modular, generalized domain coupling based on Newton iterations and parametric model order reduction using Krylov subspaces and a grid-free greedy search for a global basis. The framework enables a globalized optimization of a vehicle structure using a power-based objective. The performance of such an objective and methods for experimental power determination are discussed., Ein performantes Framework zur wiederholten Parametervariationen von vibroakustischen Finite Elemente Fahrzeugmodellen wird vorgestellt. Er basiert auf einer modularen, generalisierten Gebietskopplung mittels Newton-Iterationen, sowie parametrischer Modellreduktion durch Krylov Unterräume und netzfreier Greedy-Suche einer globalen Basis. Das Framework ermöglich die globalisierte Optimierung einer Fahrzeugstruktur bezüglich einer leistungsbasierten Zielfunktion. Deren Performanz und experimentelle Validierung werden diskutiert.

The analysis of sound and vibrations is often performed in the frequency domain, implying the assumption of steady-state behaviour and time-harmonic excitation. External excitations, however, may be transient rather than time-harmonic, requiring time-domain analysis. Some material properties, e.g.\ often used to represent for damping treatments, are still described in the frequency domain, which complicates simulation in time. In this paper, we present a method for the linearization of finite element models with nonlinear frequency dependencies. The linearization relies on the rational approximation of the finite element matrices by the AAA method. We introduce the Extended AAA method, which is classical AAA combined with a degree two polynomial term to capture the second order behaviour of the models. A filtering step is added for removing unstable poles.

The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials., QC 20201230

The increase of greenhouse gas emission is commonly accepted to largely contribute to global warming, in part due to the massive use of non-renewable fossil energy sources. It is a reason why recently, beside other industrial sectors, electric mobility has been considered as the next generation for transportation systems. But the electrification of a vehicle introduces new challenges in its design since it involves different domains of expertise than the ones from Internal Combustion Engine (ICE) vehicles. In particular, Noise, Vibration and Harshness (NVH) comfort is significantly affected by powertrain changes, i.e. from ICE to electric machine. High and unpleasant acoustic noise from resonances may occur but can be addressed numerically to support decision making processes early enough in the design stages. The accurate prediction of its radiated acoustic noise then requires a thorough multi-physical understanding, from the system-level (electric machine) to the component-level (stator and rotor cores).First from a system-level point of view, two multi-physical modeling frameworks that use different model simplifications were implemented. By comparing simulated results to experimental measurements at each physical step of the modeling flow (electromagnetic, vibration, acoustic), it was shown that both models are accurate enough for pre-designing phases. It was also shown that considering only the stator core to contribute to the vibro-acoustic behavior of electric machines is a valid assumption.Second from a component-level point of view, the rotor and the stator core were investigated. The rotor influence on the complete machine structural dynamics was assessed. Beside the validated effects of different rotor topologies on the radiated noise, an analytical model was successfully developed to explain the occurrence of a particular vibration mode; whose explanation was still not offered in literature. In parallel, the stator core was studied, essentially because i, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

The vibro-acoustic behaviour of poroelastic materials is often formulated as boundary value problems based on the continuum mechanics Blot's theory expressed as two coupled partial differential equations. This paper presents an extension of the Wave Based Method (WBM), a numerical technique to solve these vibro-acoustic boundary value problems in a computationally efficient manner. At present, the Finite Element Method (FEM) is the most commonly used prediction technique to deal with these Biot equations, but suffers from the disadvantage that the system matrices have to be recalculated for each frequency of interest due to the frequency-dependent equation parameters. This harms the inherent effectiveness of the FEM. Additionally, due to the discretisation into a large number of small finite elements and the high number of unknowns per node, the computational efforts involved practically restrict the use of FEM to low-frequency applications. The method discussed in this paper is based on an indirect Trefftz approach. Exact solutions of the three coupled waves, supported by Biot's equations, are used as basis functions in a solution expansion to approximate the field variables in a poroelastic boundary value problem. This approach leads to smaller systems of equations, enabling an efficient solution at higher frequencies., QC 20120206