Naslov
Simulacija buke u unutrašnjosti vozila uzrokovane vanjskim izvorom zvuka koristeći metodu konačnih elemenata (MKE)
(Simulation of the vehicle interior noise generated by an exterior sound source by using finite element method (FEM))

Autori
Šimag, Martina

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, diplomski rad, diplomski

Fakultet
Fakultet strojarstva i brodogradnje

Mjesto
Zagreb

Datum
17.05

Godina
2019

Stranica
123

Mentor
Alujević, Neven

Ključne riječi
Sound, Vibration, Vibroacoustics, Vehicle interior noise, Automotive NVH, FEM

Sažetak
Vehicle manufacturers are becoming more and more aware that the interior sound quality of a vehicle greatly affects the customer's decision to make a purchase. This is especially true with passenger cars in the upper market segment. Therefore, improving noise, vibration and harshness (NVH) quality of passenger vehicles has become an increasingly important topic in the automotive industry. As such, it is of great interest for noise and vibration engineers to be able to accurately predict the interior sound of a car in the early stage of the vehicle design. This is necessary to avoid substantially increased costs in the later vehicle development stages. In this thesis, a methodology to predict the interior sound field in a passenger road vehicle is developed using a commercial Finite Element (FE) software ACTRAN. This piece of software is a current state-of-the-use in the European car manufacturing industry. In the first part of the thesis, a simply supported flexible rectangular plate, which represents the firewall between the engine compartment and the passenger space, is fully coupled to a box-shaped acoustic cavity having the other five walls rigid. The model geometry is chosen such that it roughly approximates a real car. Starting from separate differential equations of motions for the plate and the acoustic cavity, a fully coupled vibro-acoustic model is developed using the modal decomposition technique. An equivalent numerical model is also built in ACTRAN. By comparing some characteristic results obtained using the analytical model and the numerical model, the FE size and the maximum frequency where the interior sound pressure levels can still be accurately predicted are determined. In the second part of the thesis a numerical, FE-based methodology to predict the interior noise due to three principal sound sources in an example road vehicle is developed using ACTRAN. The three noise sources are: the engine noise, the tyre-rolling noise, and the exhaust noise. The geometry of the example vehicle corresponds to a real luxury sedan. The methodology developed is based on a three-step procedure applied in the frequency range of interest from 100 Hz to 1600 Hz. In the first step, the finite element exterior acoustic model is built in order to calculate the surface pressure distribution on the rigid exterior wrap of the vehicle. The acoustic medium is excited by exterior volume velocity sound sources at four characteristic locations. The four locations are chosen at the left rear wheelhouse, at the left front wheelhouse, in the engine compartment and at the exhaust. In the second step, the complex acoustic pressure distribution on the rigid exterior wrap of the structural parts of the vehicle is calculated. It is used in the third step to excite the flexible "body-in-blue" vehicle. Frequency Response Functions (FRFs) between the volume velocities of the four characteristic exterior sound sources and the acoustic pressures at six characteristic interior locations are calculated. Also the whole distribution of the sound pressure in the vehicle interior is computed, presented and discussed.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo, Tehnologija prometa i transport

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