Sapphire stress-strain curves

Stress-strain curves in sapphire exhibit a three-stage hardening both for basal and prism plane slip [97, 201]. The mechanisms for each are quite different from each other, and also from those described above. 

Figure 9.24 Stress-strain curves of sapphire deformed in basal glide at various temperatures [201].

Fig. 4.51 Stress-strain curves showing initial yielding behavior of Verneuil and Czochralski sapphire, a As-received specimens and b specimens reground to satin finish. Test temperature and crosshead speed appear in inset in this and subsequent figures [19]. With kind permission of John Wiley and Sons...

Field and Swain have studied elasto-plastic response on a number of brittle materials, including silicate glass, silicon single crystal and single crystalline sapphire, by the indentation with small micron sized spherical tipped indenters. The analysis of indentation stress-strain curve was performed from the indentation on... 

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