Thermodynamic dislocation theory for polycrystals under tension/compression

TL;DR

This paper extends thermodynamic dislocation theory to polycrystals under tension or compression, deriving a geometric factor and validating the model with experimental stress-strain data for various metals.

Contribution

It derives the geometric factor for polycrystals in thermodynamic dislocation theory and calibrates the model parameters using large-scale least-square analysis.

Findings

The geometric factor for polycrystals is equal to 2.

Simulated stress-strain curves match experimental data for OFHC copper, ARMCO iron, and 4340 steel.

The theory accurately predicts material behavior under tension and compression.

Abstract

Starting from the assumption that all possible orientations of grains are equally probable, we prove that the geometric factor of thermodynamic dislocation theory for polycrystals subjected to axially symmetric tension or compression must be equal to 2. We then use large-scale least-square analysis to identify the physics based parameters of this theory and show that the simulated stress-strain curves for OFHC copper, ARMCO iron and 4340 steel agree well with the experiments of Johnson and Cook.