Deformation field heterogeneity in punch indentation

Abstract

Plastic heterogeneity in indentation is fundamental for understanding mechanics of hardness testing and impression-based deformation processing methods. The heterogeneous deformation underlying plane-strain indentation was investigated in plastic loading of copper by a flat punch. Deformation parameters were measured, in situ, by tracking the motion of asperities in high-speed optical imaging. These measurements were coupled with multi-scale analyses of strength, microstructure and crystallographic texture in the vicinity of the indentation. Self-consistency is demonstrated in description of the deformation field using the in situ mechanics-based measurements and post-mortem materials characterization. Salient features of the punch indentation process elucidated include, among others, the presence of a dead-metal zone underneath the indenter, regions of intense strain rate (e.g. slip lines) and extent of the plastic flow field. Perhaps more intriguing are the transitions between shear-type and compression-type deformation modes over the indentation region that were quantified by the highresolution crystallographic texture measurements.

Shape‐Memory Topographies on Nickel–Titanium Alloys Trained by Embossing and Pulse Electrochemical Machining

“…For simplification, we assume that the deformation field resulting from compression of the PECM structures is comparable to that of a flat punch indentation. For this case, Murthy et al revealed a variation of texture indicating a state of simple shear right at the corner of the flat punch, in our case the edge of the PECM structures . Meanwhile, a state of plane‐strain compression was observed directly underneath the flat punch.…”

Kinematic flow patterns in slow deformation of a dense granular material

“…One important distinction, however, is the reversibility in elastic column buckling -the deformation in Fig. 11 and confirmed in experiments [20]. Likewise, this flow is reproduced in exact-scale NSCD simulations of the granular medium.…”

Deformation field evolution in indentation of a porous brittle solid

“…Indirect estimation of strain by analyzing deformed microstructure revealed through metallographic etching (Samuels and Mulhearn, 1957), physical grid distortion (Hill et al, 1947;Atkins and Tabor, 1965) and secondary-phase distortion (Chaudhri, 1993) have all been traditionally used to understand the deformation in a metal around a wedge indenter. More recently, experimental techniques based on high-speed image analysis have provided further insight into the evolution of the deformation during indentation (Murthy et al, 2008(Murthy et al, , 2014 and have enabled direct comparisons of the ensuing strain fields to microstructure and texture evolution. These prior studies have provided requisite background capability for exploring deformation response of more complex materials such as porous solids (e.g., soft rocks) that exhibit both ductile and brittle behavior (Huang and Detournay, 2012;Lin et al, 2012;Alehossein et al, 2000).…”