Finite deformation analysis of slip-induced crystalline rotations during tensile and compressive tests on bcc iron crystals

ABSTRACT

This work compares slip-induced lattice rotations calculated from double-slip, finite-deformation analytical solutions to electron-back-scattering-diffraction (EBSD) rotation measurements from SEM in situ, room temperature straining of bcc iron crystals. The finite-deformation modelling assumes slip proportionality between the two dominant active systems. Four experimental cases from a recently published work (2015) are examined, two in axial tension and two in axial compression. They correspond to mixed double-slip on {110} and {112} planes, with slip on the latter in both ‘easy’ and ‘hard’ orientations. In the experiments, EBSD rotation measurements were made on three faces of the iron samples and the dominant active systems were identified from slip traces. Here the relative contributions of the two systems for the best match with available rotation data are determined for each case, and the results discussed in relation to initial shear stress and (probable) critical shear-strength ratios. The analyses provide insight into achievable accuracy in crystal-slip quantification, based on slip-trace observations and rotation measurements of a sample’s load and lateral axes, and some assessment of the relative hardening of active slip systems.

KEYWORDS:

• Bcc iron crystals
• slip kinematics
• proportional double-slip
• finite deformation experiments

Acknowledgements

The authors thank Mohammad Amin Sahafipourfard, PhD student in Civil Engineering, North Carolina State University, for making the final, computer-generated Figures 2–8 from the first author’s carefully measured and calculated, hand-plotted curves. We also thank the referees for useful comments that led to the addition of the first appendix and other clarifications in the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.