Criterion for thermo-plastic shear instability
Dynamic torsional Kolsky (split-Hopkinson) bar experiments on thin-walled tubes of 1018 cold-rolled and 1020 hot-rolled steel are modeled using a deformation plasticity theory which incorporates a specific constitutive model for the shear stress in terms of strain, strain-rate, and temperature into a system of differential equations. The exact time-dependent homogeneous flow solution of the equations is found and used to derive a special case of a generally accepted instability criterion. For given material parameters, this criterion predicts a critical strain at which a homogeneous deformation can bifuricate into a localized deformation, i.e., a shear band, at constant strain-rate. Stability diagrams of strain-rate vs. strain can be constructed for the two types of steel using the criterion. The Kolsky bar data is shown to be consistent with this analysis, and an explanation for the instability criterion is given which assumes that small perturbations on the non-steady homogeneous flow are isentropic to first order.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6376134
- Report Number(s):
- SAND-81-0041C; CONF-810684-8; ON: DE81023178
- Resource Relation:
- Conference: APS conference on shock waves in condensed matter, Menlo Park, CA, USA, 23 Jun 1981
- Country of Publication:
- United States
- Language:
- English
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