Complex Modulus and Damping Measurements Using Resonant and Non-Resonant Methods

• Published in: SAE transactions Vol. 104; pp. 2397 - 2401
• Main Authors: Gade, S., Zaveri, K., Zaveri, G., Konstantin-Hansen, H., Herlufsen, H.
• Format: Journal Article
• Language: English
• Published: Society of Automotive Engineers, Inc 01-01-1995
• ISSN: 0096-736X; 2577-1531

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 undermachinery 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.