A systematic approach for effective measurement of deformation front orientation accompanying plastic instability

Abstract

Understanding the geometrical characteristics of deformation bands accompanying plastic instability in steels, particularly the orientation of bands with respect to the loading axis is imperative since they induce surface roughness during metal forming operations. While significant efforts have been made earlier to study the orientation characteristics of deformation bands, the actual nature remains uncertain due to the contradictory results that are reported. The ambiguity is primarily due to the lack of appropriate methodology for measuring the true orientation. In this work, an approach that considers the underlying mechanisms of band growth is employed to precisely measure the deformation front orientation using strain rate and shear strain fields obtained from digital image correlation. The results show that the band front advances with a random change in its orientation introduced as a resultant of two competing shear localizations. The observations recommend the measurement of deformation front orientations only after the completion of the band growth cycle. Keywords: Plastic instability, Deformation bands, Digital image correlation, Medium carbon steel