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Lee, Seungkyu
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Equivalent Material Properties of Multi-Layer, Lightweight, High-Performance Damping Material and Its Performance in Applications

3M Company-Taewook Yoo, Ronald Gerdes, Seungkyu Lee, Thomas Herdtle
3M Deutschland GmbH-Georg Eichhorn
Published 2019-06-05 by SAE International in United States
In this study, we investigated two aspects of a multi-layer, lightweight damping treatment. The first aspect studied was an equivalent material property estimate for a simplified finite element (FE) model. The simplified model is needed for computational efficiency, i.e. so that Tier 1 and OEM users can represent this complex, multi-layer treatment as a single, isotropic solid layer plus an aluminum constraining layer. Therefore, the use of this simplified FE model allows the multilayer treatment to be included in large body-in-white structural models. An equivalent material property was identified by first representing three unique layers (two adhesive layers plus a connecting standoff layer) by a single row of isotropic solid elements, then an optimization tool was used to determine the “best fit” for two properties including Young’s modulus and material loss factor. Equivalent properties were validated for various substrate thickness and coverage areas heights by comparison to center-driven long bar test results.Secondly, the effect of damping treatment size was studied using the previously identified equivalent material properties. This was a damper placement study to determine…
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Comparison of Long Bar Test Method to Oberst Bar Test Method for Damping Material Evaluation

Daniel Stanley
3M Company-Taewook Yoo, Ronald W. Gerdes, Seungkyu Lee, Thomas Herdtle
Published 2017-06-05 by SAE International in United States
Several methods for evaluating damping material performance are commonly used, such as Oberst beam test, power injection method and the long bar test. Among these test methods, the Oberst beam test method has been widely used in the automotive industry and elsewhere as a standard method, allowing for slight bar dimension differences. However, questions have arisen as to whether Oberst test results reflect real applications. Therefore, the long bar test method has been introduced and used in the aerospace industry for some time. In addition to the larger size bar in the long bar test, there are a few differences between Oberst (cantilever) and long bar test (center-driven) methods. In this paper, the differences between Oberst and long bar test methods were explored both experimentally and numerically using finite element analysis plus an analytical method. Furthermore, guidelines for a long bar test method are provided.
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Structural Damping by the Use of Fibrous Materials

3M-Taewook Yoo
Polytec Inc-Sean Hollands
Published 2015-06-15 by SAE International in United States
Because of the increasing concern with vehicle weight, there is an interest in lightweight materials that can serve several functions at once. Here we consider the vibration damping performance provided by an “acoustical” material (i.e., a fibrous layer that would normally be used for airborne noise control). It has been previously established that the vibration of panel structures creates a non-propagating nearfield in the region close to the panel. In that region, there is an oscillatory, incompressible fluid flow parallel to the panel whose strength decays exponentially with distance from the panel. When a fibrous medium is placed close to the panel in the region where the oscillatory nearfield is significant, energy is dissipated by the viscous interaction of the flow and the fibers, and hence the panel vibration is damped. The degree of panel damping is then proportional to the energy removed from the nearfield by the viscous interaction with the fibrous medium. In his paper, experiments are described that demonstrate this effect. Fibrous layers were placed next to a lightly damped panel driven…
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