  The slip system activity in microtensile tests of ferrite single crystals is
compared with predictions made by the discrete slip plane model proposed by
Wijnen et al. (International Journal of Solids and Structures 228, 111094,
2021). This is an extension of conventional crystal plasticity in which the
stochastics and physics of dislocation sources are taken into account in a
discrete slip band. This results in discrete slip traces and non-deterministic
mechanical behavior, similar to what is observed in experiments. A detailed
analysis of which slip systems are presumed to be active in experiments is
performed. In small-scale mechanical tests on BCC metals and alloys, non-Schmid
effects are often needed to explain the observed response. Therefore, these
effects are incorporated into the model by extending a non-Schmid framework
commonly used to model {110} slip to {112} planes. The slip activity in the
simulations is compared to the slip activity in single crystal ferrite
microtensile tests. This is done for the discrete slip plane model with and
without non-Schmid effects, as well as for a conventional crystal plasticity
model. The conventional crystal plasticity model fails to predict the diversity
in active slip systems that is observed experimentally. The slip activity
obtained with the discrete slip plane model is in convincingly better agreement
with the experiments. Including non-Schmid effects only entails minor
differences. This suggests that stochastic effects dominate the behavior of
ferrite crystals with dimensions in the order of a few micrometers and that
non-Schmid effects may not play a large role.
