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Fast Broadband Curved Insertion Loss Simulation of an Inner Dash Insulator Using a Cylindrical Transfer Matrix Method Spectral Approach

Treves-Arnaud Duval, Mickael Goret
Interac-Gerard Borello
Published 2019-06-05 by SAE International in United States
Middle and high frequency vibro-acoustic simulation of complex shape insulators requires using 3D poroelastic finite elements. This can be applied to either the whole part (up to 2500 Hz maximum) or through singly curved pre-computed Insertion Losses (up to 5000 Hz maximum) to be introduced in large SEA or energy-based models. Indeed, a dependence of the Insertion Loss slopes of noise treatments following the curvature is observed both experimentally and numerically. Beyond frequency range limitations, poroelastic finite element simulations following all curvatures and thickness 3D maps typically take too much time of up to a few hours each. A cylindrical Transfer Matrix Method spectral approach significantly reduces the time for the calculation of singly curved Insertion Losses up to 10 kHz to only a few minutes. This simplifies enormously the SEA modeling effort enabling easier, more precise fully trimmed vehicle middle and high frequency vibro-acoustic simulations. A dash insulator Insertion Loss numerical validation case will be presented comparing the different methods.
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Ecofelt Hybrid Stiff NVH Tunable Insulator

Treves-Arnaud Duval, Guillaume Crignon, Mickael Goret, Dominique Lemaire
PSA Peugeot Citroën-Jean-Baptiste Prunet, Patrick Chanudet
Published 2018-06-13 by SAE International in United States
Whenever the noise source level or the expected acoustic comfort increases for diesel engines for example or for premium petrol vehicles, the required weight per unit area can be specified above 2000 g/m2 for the equivalent barrier of a mixed absorbing-insulating noise treatment. For an ABA foam/heavy layer/felt insulator, this is not a big issue, one has to increase the intermediate heavy layer weight. For hybrid stiff compressed felt backfoamed standard technologies, going above 2000 g/m2 is critical due to absorption properties loss following much too high airflow resistances and progressive porosity loss (above 250 kg/m3) as well as too high bending stiffness presenting resonant modes progressively and assembly manipulation issues. Last but not least, compressed felts begin to present too high costs at these weights against those of the heavy layers of ABA systems.The chips urethanes give an answer to the aforementioned issues for high weights above 2000 g/m2 up to 3500 g/m2 typically for hybrid stiff backfoamed concepts in the same mold and with the same process as lower weights (called Polyfoam). The acoustic properties of these highly…
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Comprehensive Hybrid Stiff Insulators Family: The Chips Urethane Contribution

Treves-Arnaud Duval, Guillaume Crignon, Mickael Goret, Maxime Roux
Published 2017-06-05 by SAE International in United States
The lightweighting research on noise treatments since years tends to prove the efficiency of the combination of good insulation with steep insulation slopes with broadband absorption, even in the context of bad passthroughs management implying strong leakages. The real issue lies more in the industrial capacity to adapt the barrier mass per unit area to the acoustic target from low to high segment or from low petrol to high diesel sources, while remaining easy to manipulate. The hybrid stiff insulator family can realize this easily with hard felts barriers backfoamed weighting from 800 g/m2 to 2000 g/m2 typically with compressions below 10 mm.Above these equivalent barrier weights and traditional compressions of 7 mm for example, the high density of the felts begins to destroy the open porosity and thus the absorption properties (insulation works anyway here, whenever vibration modes do not appear due to too high stiffness…). The felt costs begin to be critical for these intermediate weights above 2000 g/m2 as well. From 2000 g/m2 up to 3000 g/m2 or 3500 g/m2 equivalent barriers,…
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