A new rock salt constitutive model with back stress and drag stress hardening

Abstract

This paper presents a new, largely phenomenological, model for rock salt that includes branches for pressure solution and dislocation glide viscoplasticity. The dislocation glide branch utilizes back stress hardening for heterogeneously distributed dislocations and drag stress hardening for uniformly distributed dislocations. By transitioning between pressure solution at low strain rates, back stress dominated hardening at low to medium strain rates, and drag stress dominated hardening at high strain rates, a single model calibration can capture the behavior of Waste Isolation Pilot Plant salt over strain rates ranging from 10–12 to 10–4 1/s, and temperatures from 20 to 60⁰C. The same model calibration can also predict the Bauschinger effect (and represent reverse creep). Although room for improvement exists, the model’s elegant formulation can capture an assortment of damage-free behaviors