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Complex Modulus and Damping Measurements Using Resonant and Non-Resonant Methods
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Abstract
The stress-strain relationship of visco-elastic materials, generally used in the damping treatment of structures, can be described by two properties, such as the perfectly elastic (in-phase) stress-strain modulus and the loss factor. The values of these properties need to be determined in tension or compression for materials used as unconstrained damping layers and as anti-vibration mountings under machinery and under foundation blocks.
Using a dual channel FFT analyzer, the specimen can be excited using wide band random excitation, and the properties determined from the frequency response spectra, as a continuous function of frequency, as shown in the following.
Another possibility is to preload the specimen by a well-known mass, such that the preloaded damping material becomes a part of a resonant mass-spring-damper system. Damping, e.g. loss factor, is then determined from the 3 dB bandwidth of the resonance. The procedure is then repeated at different frequencies of the specimen using different mass-loadings.
The two methods are demonstrated and compared in this article.
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Citation
Gade, S., Zaveri, K., Konstantin-Hansen, H., and Herlufsen, H., "Complex Modulus and Damping Measurements Using Resonant and Non-Resonant Methods," SAE Technical Paper 951333, 1995, https://doi.org/10.4271/951333.Also In
References
- Herlufsen, H. “ Dual Channel FFT Analysis (Part I & II) ” Brüel & Kjær Technical Review No. 1 & 2 1984
- Ganeriwala, S.N. “ Characterization of Dynamic Viscoelastic Properties of Elastomers using Digital Spectral Analysis ” Ph.D. Thesis University of Texas at Austin 1982
- Gade, S. Herlufsen, H. “ Digital Filter Techniques vs. FFT Techniques for Damping Measurements ” Brüel & Kjær Technical Review No. 1 1994