Assessment of Internal Damping in Uniaxially Stressed Metals: Exponential and Autoregressive Methods

[+] Author and Article Information
A. L. Audenino, E. M. Zanetti, P. M. Calderale

Dipartimento di Meccanica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

J. Dyn. Sys., Meas., Control 120(2), 177-184 (Jun 01, 1998) (8 pages) doi:10.1115/1.2802407 History: Received December 08, 1995; Online December 03, 2007


When a metallic material is highly stressed, its internal specific damping capacity increases showing a nonlinear behavior. In spite of this, the most part of experimental methods employ nonhomogeneous stress fields measuring only a volumetric average, often called structural damping. To overcome this problem the procedure herein presented extends the applicability of the plain traction or compression methods to higher frequency range (up to 300 Hz). The introduced methodology corrects for elastic energy and dissipated energy relative to the test machine and to the fixtures. The experimental procedure is based on the acquisition of a decay signal when the test machine excitation force has been removed. Two different methods to extract the pattern of internal damping versus material strain have been compared: one is based on least square exponential fitting while the other employs an autoregressive model. Best results have been obtained combining the two techniques taking into account also the variation of Young’s modulus with strain. The resulting curves of the loss factor as a function of strain amplitude for three steels and two cast irons are presented.

Copyright © 1998 by The American Society of Mechanical Engineers
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