Geometric flow control of shear bands by suppression of viscous sliding.
Shear banding is a plastic flow instability with highly undesirable consequences for metals processing. While band characteristics have been well studied, general methods to control shear bands are presently lacking. Here, we use high-speed imaging and micro-marker analysis of flow in cutting to reveal the common fundamental mechanism underlying shear banding in metals. The flow unfolds in two distinct phases: an initiation phase followed by a viscous sliding phase in which most of the straining occurs. We show that the second sliding phase is well described by a simple model of two identical fluids being sheared across their interface. The equivalent shear band viscosity computed by fitting the model to experimental displacement profiles is very close in value to typical liquid metal viscosities. The observation of similar displacement profiles across different metals shows that specific microstructure details do not affect the second phase. This also suggests that the principal role of the initiation phase is to generate a weak interface that is susceptible to localized deformation. Importantly, by constraining the sliding phase, we demonstrate a material-agnostic method-passive geometric flow control-that effects complete band suppression in systems which otherwise fail via shear banding.
Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN, USA.
Dinakar
0000-0001-9248-5380
D
Sagapuram
Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN, USA.
Koushik
K
Viswanathan
Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN, USA.
Anirban
A
Mahato
Department of Civil Engineering , Indian Institute of Science , Bangalore, India.
Narayan K
NK
Sundaram
Seco Tools (UK) Ltd. , Springfield Business Park , Alcester, Warwickshire, UK.
Rachid
R
M'Saoubi
Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN, USA.
Kevin P
KP
Trumble
Center for Materials Processing and Tribology , Purdue University , West Lafayette, IN, USA.
Srinivasan
S
Chandrasekar
cutting; deformation processing; flow instability; metals; shear bands