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Inverse Vibration Problem Used for the Characterization of the Damping Added by a Trim Foam on a Plate

CEVAA-Nicolas Merlette
CEVAA, LAUM-Meryem LE DEUNF
  • Technical Paper
  • 2020-01-1580
To be published on 2020-06-03 by SAE International in United States
Many solutions exist to insure the NVH comfort of ground and air vehicles, like heavy mass (bitumen pads), viscoelastic treatments and absorbing foams. The trim foam is an alternative to heavy solutions. To know the potential of the foam, a study of its capacity to damp vibration is done. A system, composed by a suspended plate, with a foam on it, is characterized in different cases of contact at the foam-plate interface (glued or not) and with different types of foam. An experimental test facility is developed to identify the global damping of the structure: a laser vibrometer measures the displacement field of the foam-plate structure, an inverse method is used to determine the structural parameters. By changing the contact at the interface, it is possible to identify the contribution of the friction forces to the global damping of the structure. Another type of damping is the viscoelastic damping due to the intrinsic characteristics of the trim foam. With the help of FEA, it is possible to understand the influence of the damping effect. The…
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Resabtors - Advanced Multi-Material Muffler Designs for Clean Air Applications

Umfotec GmbH-Ralf Buck, Ingo Krebs
  • Technical Paper
  • 2020-01-1554
To be published on 2020-06-03 by SAE International in United States
The development and production of resonators on the charged air side of combustion engines require profound base of knowledge in designing, simulating and the production of such parts in different materials (aluminum, copper, stainless steel and technical plastic). As combustion engines are under constant discussion, this existing knowledge base should be used for other applications within and outside the automotive industry. Very quickly it became apparent that new challenges often require completely new solutions, designs and materials to meet the requirements of flow noise reducing parts. For example, for clean air applications mufflers based on “special treated foams” and “meta-materials” can be introduced. These materials offer new potentials for tuning of the frequency range and allow improved broad banded flow noise attenuation. Such parts are named “Resabtors” in order to take respect of the different flow noise attenuation principles resonation and absorbing. Since in almost all applications the installation space is very limited, it was necessary to combine these two principles into one component. This results into significant challenges to identify the properties of the…
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Innovative Acoustic Material Concept Integration Into Vehicle Design Process

Odenwald-Chemie GmbH-Michael Feist-Muench
dBVibroAcoustics-Denis Blanchet
  • Technical Paper
  • 2020-01-1527
To be published on 2020-06-03 by SAE International in United States
Integration of acoustic material concepts into vehicle design process is an important part of full vehicle design. The ability to assess the acoustic performance of a particular sound package component early in the design process allows designers to test various designs concepts before selecting a final products. This paper describes an innovative acoustic material concept which is easily integrated in a design process through the use of a database of Biot parameters. Biot parameters are widely used in the automotive industry to describe the physical interactions between the acoustics waves travelling through foams, fibers or metamaterials and the solid and fluid phase of these poro-elastic materials. This new acoustic material concept provides a combination of absorption, transmission loss and added damping on the panel it is attached to. It has shown unique vibro-acoustics performance when tested on a German car manufacturer flagship vehicle and provides the ability to reduce the space needed for sound package component compared with classical solutions.
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Micro-Macro Acoustic Modeling of Heterogeneous Foams with Nucleation Perturbation

Duke University-Johann Guilleminot
Ecole des Ponts ParisTech-Michel BORNERT
  • Technical Paper
  • 2020-01-1526
To be published on 2020-06-03 by SAE International in United States
The properties of a polyurethane foam are greatly influenced by the addition of graphite particles during the manufacturing process, initially used as a fire retardant. These thin solid particles perturbate the nucleation process by generating bubbles in its immediate vicinity. The preponderance of work so far has focused on foams that are locally relatively homogeneous. We propose a model for locally inhomogeneous foams (including membrane effects) consisting of a random stack of spheres that permits one to represent certain pore size distribution functions. The cellular structure of the foam is obtained through a Laguerre tessellation and the solid skeleton determined from the minimization of surface energy (Surface Evolver). The structure of real foam samples is analyzed using X-ray computed tomography and scanning electron microscopy followed by image processing to create computerized three-dimensional models of the samples. The corresponding effective material parameters, including the permeability, the tortuosity and the viscous characteristic length are computed by applying a numerical homogenization approach. All the numerical data are presented, discussed and further compared with experimental results.
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A method to evaluate the acoustic performance of the Pillar filler foam in a Truck cab

ESI North America-Praveen Jayasheela, Ricardo Alvarez
Volvo Group North America-Suresh Patra
  • Technical Paper
  • 2020-01-0505
To be published on 2020-04-14 by SAE International in United States
The truck cab is made of many structural members like a, b, c, hinge - pillar, rocker, roof rails, headliner, quarter panels, cross-members at the floor and other body panels. For an acoustic example, the source energy travels easily from one end to another end through pillars. To reduce these acoustic effects, the filler foams were added inside the pillars. The proper usage of filler design and filler material type produces the optimal sound response at the driver head space location. In this paper, an analytical method is used to evaluate the acoustic performance of the fillers as described above and the method also avoids the expensive full vehicle tests. The statistical energy analysis (SEA) model simulations and post-processing techniques were used to evaluate the results quickly with an acceptable level of accuracy. It has proven that the effect of the foam thickness and foam coverage area of the fillers can be evaluated and helped to achieve the optimal sound response at the driver head location.
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The Effect of Structural Damping Foam on Tire Vibration

SAE International Journal of Vehicle Dynamics, Stability, and NVH

Bridgestone Americas, Inc., USA-Thomas Sams
  • Journal Article
  • 10-04-02-0006
Published 2020-02-28 by SAE International in United States
During the vehicle design state, vehicle noise and vibration are taken into consideration. The tire is a large contributor to the noise and vibration experienced inside the vehicle cabin. Any unevenness or asperities in the road cause the tire structure to vibrate, which in turn causes components in the vehicle to vibrate and generate noise. It is common in the industry to use foam inserts inside the tire air cavity that reduces the noise generated. This foam is typically intended to reduce a specific resonance in the tire-the resonance due to the air cavity. Recently, there is interest in using foam as a structural damper to reduce structural resonances in the tire. A new analytical tire model for determining the effect that structural damping foam has on the noise and vibration characteristics of the tire has been developed. The theoretical formulation of this model is presented, as well as comparison with experiments and a parametric analysis of the model. The model shows good agreement with experimental results and also gives some additional insights into how…
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Hardening Lightweight Metal Foams with Nanocoating

  • Magazine Article
  • TBMG-35818
Published 2020-01-01 by Tech Briefs Media Group in United States

Bones are strong and stable and can cope with loads almost as well as steel. But despite their strength, they are light enough to be easily moved by humans and animals. The secret lies in the combination of a hard, exterior shell that encases a porous lattice-like network of bone tissue in the interior of the bone. This structure saves on material and reduces weight.

Viable, Environmentally Friendly Alternative to Polystyrene Foam

  • Magazine Article
  • TBMG-35817
Published 2020-01-01 by Tech Briefs Media Group in United States

An environmentally friendly foam was developed that can be used as an alternative to polystyrene foam, or Styrofoam™. The foam is made mostly from nanocrystals of cellulose, the most abundant plant material on Earth. The researchers also developed an environmentally friendly and simple manufacturing process to make the foam using water as a solvent instead of other harmful solvents.

Products of Tomorrow: December 2019

  • Magazine Article
  • TBMG-35707
Published 2019-12-01 by Tech Briefs Media Group in United States

This column presents technologies that have applications in commercial areas, possibly creating the products of tomorrow. To learn more about each technology, see the contact information provided for that innovation.

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Polyurethane Foam Performances’ Influence on Body Pressure Distribution on an Automotive Seat

Changchun Faway Adient Automotive System Co., Ltd. Technical-Yanfei Wang, Li-Feng Xing, Yu-Qiang Huang
Published 2019-11-04 by SAE International in United States
From the microstructure point of view, the relationship of car seat comforts, including the static and dynamic comfort, and the polyurethane foam performance of its cushion has been analyzed. In this paper, polyurethane cushion performances associated with the seat static comfort have been mainly discussed. And their quantizing relation is obtained. How to apply the pressure gradient, one of body pressure distribution parameters, to optimize automobile seat comfort has been analyzed in detail. The findings suggest maximum and mean values of body pressures increase by 0.09 KPa and 0.04 KPa with the cushion foam hardness (Ph) increasing 1 KPa, respectively. The pressure gradient is little dependent on the cushion foam hardness within the range of Ph=4 ~ 5 KPa. Furthermore, the foam thickness under the hip should be greater 80 mm in order to reduce subcutaneous stresses under conditions of Ph= 6.2 KPa.
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