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A Thermodynamic Internal Variable Model for the Partition of Plastic Work into Heat and Stored Energy in Metals

Rosakis, P. and Rosakis, A. J. and Ravichandran, G. and Hodowany, J. (2000) A Thermodynamic Internal Variable Model for the Partition of Plastic Work into Heat and Stored Energy in Metals. Journal of the Mechanics and Physics of Solids, 48 (3). pp. 581-607. ISSN 0022-5096.

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The energy balance equation for elastoplastic solids includes heat source terms that govern the conversion of some of the plastic work into heat. The remainder contributes to the stored energy of cold work due to the creation of crystal defects. This paper is concerned with the fraction β of the rate of plastic work converted into heating. We examine the status of the common assumption that β is a constant with regard to the thermodynamic foundations of thermoplasticity and experiments. A general internal-variable theory is introduced and restricted to abide by the second law of thermodynamics. Experimentally motivated assumptions reduce this theory to a special model of classical thermoplasticity. The only part of the internal energy not determined from the isothermal response is the stored energy of cold work, a function only of the internal variables. We show that this function can be inferred from stress and temperature data from a single adiabatic straining experiment. Experimental data from dynamic Kolsky-bar tests at various strain rates yield a unique stored energy function. Its knowledge is crucial for the determination of the thermomechanical response in non-isothermal processes. Such a prediction agrees well with results from dynamic tests at different rates. In these experiments, β is found to depend strongly on both strain and strain rate for various engineering materials. The model is successful in predicting this dependence. Requiring β to be constant is thus an approximation of dubious validity.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Rosakis, A. J.0000-0003-0559-0794
Ravichandran, G.0000-0002-2912-0001
Additional Information:© 2000 Published by Elsevier Science Ltd. Received 10 June 1998; received in revised form 16 June 1999. This work was initiated while P.R. was on leave at the California Institute of Technology; he would like to thank J. K. Knowles and the GALCIT Faculty for their hospitality, also the National Science Foundation for support through Grant MSS-9312858. G.R. and A.J.R. gratefully acknowledge support from the Office of Naval Research (Scientific Officer: Dr Y. D. S. Rajapakse) through Grant N0014-95-1-0453 and the National Science Foundation through Grant CMS-9204026.
Funding AgencyGrant Number
Office of Naval Research (ONR)N0014-95-1-0453
Subject Keywords:thermomechanical processes; constitutive behavior; viscoplastic material; kolsky bar
Issue or Number:3
Record Number:CaltechAUTHORS:20150226-170425585
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Official Citation:P. Rosakis, A.J. Rosakis, G. Ravichandran, J. Hodowany, A thermodynamic internal variable model for the partition of plastic work into heat and stored energy in metals, Journal of the Mechanics and Physics of Solids, Volume 48, Issue 3, March 2000, Pages 581-607, ISSN 0022-5096, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55289
Deposited By: Cheryl Gause
Deposited On:03 Mar 2015 00:40
Last Modified:09 Mar 2020 13:19

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