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#19335, Keynote: A Semi-Empirical Strain and Strain-Rate Dependent Taylor-Quinney Coefficient and Applications

The conversion of plastic work into heat during mechanical deformation is important to understand the latent energy in a metal after cold working. The term of “Taylor-Quinney (TQ) Coefficient,” generally designated with a symbol of “β,” was defined as a partition of plastic work into heat for understanding not only the latent energy but also the associated thermosoftening phenomenon for predictive material model development. Constant TQ coefficients have been used as a general practice although their dependencies on strain and strain rate have been observed. Work to describe a strain-dependent TQ coefficient has been attempted but is very limited. Additionally, there is no such description on the strain-rate dependency of TQ coefficient. Based on reliable measurement of specimen temperature rise in Kolsky tension bar tests, we developed a semi-empirical description of strain and strain-rate dependent TQ coefficient, with 316 stainless steel as an example. This semi-empirical form can describe different scenarios of strain and strain-rate dependencies of the TQ coefficient for a variety of materials with different stress-strain responses. The strain and strain-rate dependent TQ coefficient was then implemented into the Johnson-Cook (JC) model for addressing the thermosoftening effect. This modified JC model was found to describe the stress-strain response of the 316 stainless steel very well across the entire low, intermediate, and high strain-rate regimes. With the experimental stress-strain data being used, the framework of the modified JC model was also used to back-calculate the TQ coefficient and subsequent latent energy. The calculated TQ coefficient was compared with direct experimental measurements and found to be consistent. This approach provides a new insight to the TQ coefficient or partition of plastic work to heat without direct measurement of specimen temperature rise.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003523. The views expressed in this article do not necessarily represent the views of the U.S. DOE or the United States Government.

Bo Song   Sandia National Laboratories
Pooyan Javadzadeh   Sandia National Laboratories
Colin Loeffler   Sandia National Laboratories