Analyzing indentation stress–strain response of LaGaO3 single crystals using spherical indenters

The nano-epsilon dot method for strain rate viscoelastic characterisation of soft biomaterials by spherical nano-indentation

“…In addition, it is worth underlining that nano-indentation stress and strain definitions considered here as well as in other nanoindentation reports (e.g. (Basu et al, 2006;Haghshenas and Klassen, 2013;Herbert et al, 2001;Pathak et al, 2008a)) are not the same as the bulk engineering stress (σ ¼ F=A) and strain j o u r n a l o f t h e m e c h a n i c a l b e h a v i o r o f b i o m e d i c a l m a t e r i a l s 5 0 ( 2 0 1 5 ) 1 5 0 -1 5 9…”

“…During the 1990s, Field and Swain proposed a method to obtain indentation stress-strain curves from load-displacement curves Swain, 1995, 1993), however their methodology was not caught on, with a few exceptions (Basu et al, 2006;Haghshenas and Klassen, 2013;Herbert et al, 2001;Pathak et al, 2008a). The majority of studies dealing with indentation strain rate define it as _ ε ind ¼ _ h=h (i.e.…”

“…In particular, the mechanical properties derived from the loading portion of the curve are representative of those of the virgin material, returning a constant modulus value regardless of the maximum load (or displacement) chosen for the measurements. Conversely, the modulus value obtained from the unloading curve is likely to increase with increasing maximum indentation load (or displacement), as expected when going beyond the sample linear elastic (or viscoelastic) region (Pathak et al, 2008a). Moreover, during unloading it is assumed that only the elastic displacements are recovered (Oliver and Pharr, 2004), thus methods based on the unloading curve are unsuitable for testing viscoelastic materials.…”

Analyzing indentation behavior of LaGaO3 single crystals using sharp indenters

“…26,27 The modulus values used to calculate K R were obtained from spherical nanoindentation experiments described in the companion paper. 28 Two samples of each orientation (LaGaO 3 (1 0 0) and (0 0 1)) were chosen for the tests. The average of five tests at each load was used for reporting the hardness and fracture toughness values.…”

Assessment of lamellar level properties in mouse bone utilizing a novel spherical nanoindentation data analysis method

“…The ability to produce indentation stress–strain curves has generally been more successful with spherical indenters (Field and Swain, 1993; Angker and Swain, 2006; Basu et al, 2006), where their relatively smoother stress fields and larger initial elastic segments (compared to sharper indenters) allow one to follow the evolution of the mechanical response in the material, from initial elasticity to the initiation of plasticity to post-yield behavior at finite plastic strains. These new procedures have successfully captured a wealth of information about the material including the elastic moduli measured in loading and unloading segments (Kalidindi and Pathak, 2008; Pathak et al, 2008a,2009b), the elastic limit (which can be identified as yielding in metallic samples (Pathak et al, 2009d,2011b) or buckling in a high aspect ratio material like vertically aligned carbon nanotube forests (Pathak et al, 2009a)), and aspects of the post-elastic behavior (Pathak et al, 2009d,2011b). In this paper, we apply these methods to indentations in bone and demonstrate their potential in correlating the changes in bone's local mechanical properties to its underlying structure.…”