Examination of indention geometry-constitutive behaviour relations with confocal microscopy and finite element modeling

Assessment of the constitutive law by inverse methodology: Small punch test and hardness

“…Both types of behaviour may be separately assessed by local indentation (on the opposite punch test and stress-strain curve give only the global response). Other information can also be provided by the observation of the pile-up geometry near the indentation print that is related to residual stress and strain hardening [21][22][23]. A criticism we would raise concerns the difficulty in observing such geometry in active environment, but pile-up height can be calculated from the variation of hardness with the reciprocal depth of the indentation print [24] with the assumption that the piled-up region also supports the indenter's load and that the normal pressure is distributed uniformly over the projected area of the indentation [25].…”

Reflection on the measurement and use of the topography of the indentation imprint

“…Despite these common purposes, there is a lack of consensus on the measurement and treatment methods used for the study of the imprint indentation. There are several measurement means: some studies are primarily focused on the use of optical microscopy (Yang et al ., ), scanning electron microscopy (SEM) (Dwyer‐Joyce et al ., ), or confocal microscopy (Santos et al ., ; Keryvin, ), while others are based on profile measurement (Hainsworth et al ., ), atomic force microscopy (AFM) measurements (Yang et al ., ) or interferometric microscopy (Su et al ., ; Marteau et al ., ). It is worth noting that most of the studies rely on qualitative information.…”

A universal relationship between indentation hardness and flow stress

“…A large number of finite element (FE) simulations of indentations and hardness have been reported (e.g., [3][4][5][6][7][8][9][10][11][12][13]). However the relation of H to more quantitative measures of true stress-strain r(e) constitutive properties, such as the yield stress (r y ) and post-yield strain hardening (r sh ), have remained ambiguous, and to a large extent semi-empirical [11][12][13]. This is in large part due to the fact that H intrinsically probes a wide range of e, hence, represents some 'average' measure of an effective flow stress, r(e) = r y + r sh .…”