We present a consistent explicit formulation of the adiabatic thermal softening effect.
This formulation is analytically derived from the well-known thermoviscoplastic
Johnson–Cook model and is expressed only in terms of the effective plastic strain and
strain-rate and does not depend on the temperature. In extreme impact loading
cases, the explicit formulation shows improvement in the numerical stability of
simulations carried out with implicit solver and leads to more consistent results.
The proposed explicit formulation can be considered as a new consistent
thermoviscoplastic constitutive model that analytically reflects the contribution of
the strain and strain-rate to the adiabatic thermal softening effect. To validate
the accuracy of the proposed explicit model, numerical simulations of two
bench-mark time-dependent problems are carried out in ABAQUS. Moreover,
due to the explicit formulation, the effect of adiabatic thermal softening
on bursting pressure and expansion of a spherical thin shell is analytically
derived.
Keywords
thermoviscoplastic, Johnson–Cook model, high strain-rate,
adiabatic thermal response, dynamic spherical cavity
expansion, thermal softening effect, Taylor impact bar test
