Wednesday  |  Salon 7  |  02:50 PM–03:10 PM

#15626, Quantifying Friction in Large-strain Deformation Processes using Digital Photoelasticity

Most large-strain deformation processes such as indentation, cutting, and metal forming involve one or more sliding contacts between the tool (die) and the workpiece. The interfacial conditions at these contacts not only differ significantly from that of lightly loaded tribological contacts (described by Amontons’ law) but are also such that the metal in the immediate vicinity of the contact undergoes plastic flow parallel to the interface as sliding occurs. In this study, we present a comprehensive experimental approach to quantify interfacial stresses and friction at such contacts using full-field photoelasticity. In particular, the interfacial stresses along the contact length are characterized by using sapphire (a stress-induced birefringent material) as the tool material coupled with digital photoelasticity to obtain full-field principal stress difference (isochromatics) and principal stress directions (isoclinics). The interfacial stress profiles are elucidated for two plane-strain problems, cutting and wedge indentation, of direct relevance to practical machining and hardness testing applications. These results along with the plastic flow dynamics and displacement data for the softer yielding metal near the interface or direct observation of the interface using a transparent tool can be correlated to explain the interfacial condition.

Jobin Thomas Mathews   Texas A&M University
Dinakar Sagapuram   Texas A&M University