Evaluation of Sinking-In and Cracking Behavior of Soda-Lime Glass under Varying Angle of Trigonal Pyramid Indenter

Abstract

It is well known that glass undergoes elastic and inelastic deformation under a sharp diamond indenter. Although brittle or less brittle behavior of glass must be connected with such mechanical responses of glass under the indenter, there has been limited research on in situ deformation behavior of glass during the loading and unloading indentation cycle. This is because most indentation tests were conducted using a commercial hardness tester for which this information is not available. In this study, the in situ sinking-in region of glass during indentation test is determined using a custom-designed indentation microscope with trigonal pyramid indenters having different tip angles. It is found that both the shape of contact region and the amount of sinking-in are affected by indenter geometries and that the projected contact region of the glass sample under Berkovich indenter is not a regular triangle but a concave triangle with bowed-in edges. This is due to the larger amount of sinking-in under the face than under the ridge of indenter. It is also found that these deformation behaviors of glass are inseparably linked with contact damage or cracking in glass.

Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

“…However, the other metric, L DR , appears to have a substantially different compositional dependence compared to L SR . Furthermore, we note that the diagonals of the indents tend to shrink much less than the side of the indents, in agreement with previous findings . This is also apparent from the observation that L SR ranges from 6% to almost 40%, while L DR only ranges from 2% to 12%.…”

“…4 The resistance to cube-corner indentation cracking proved challenging to evaluate since the majority of the glasses exhibit extensive cracking even at very low loads (<50 mN). This is consistent with literature results, reporting that the resistance to indentation cracking strongly depends on the sharpness of the indenter tip, 24,31 with smaller compositional differences as the indenter tip gets sharper. 32 An example of a crack probability vs. load curve for a crack-resistant glass, namely the metaluminous sodium aluminoborate (25Na 2 O-25Al 2 O 3 -50B 2 O 3 ), is included in Figure 5, showing the large difference in crack resistance between cube corner and Vickers indentation.…”

“…Furthermore, we note that the diagonals of the indents tend to shrink much less than the side of the indents, in agreement with previous findings. 16,24 This is also apparent from the observation that L SR ranges from 6% to almost 40%, while L DR only ranges from 2% to 12%. Considering that the experimental error for L DR can be as high as ± 4%, we do not recommend using the diagonal shrinkage as a metric for reversible volume deformation upon indentation.…”

Three‐dimensional densification measurement of Vickers‐indented glass using digital holographic tomography

“…The bowed‐in edges of the indent on silica glass result from larger sinking‐in around the indentation edges. This is due to more elastic nature of the mechanical response of silica glass with a larger H / E value (~0.1), where H and E are hardness and Young's modulus, respectively . From theory as well as from the results of the Raman shift and Cr 3+ fluorescence measurements, it is to be expected that the refractive index will be higher under the indenter tip than at the edge.…”

“…This is due to more elastic nature of the mechanical response of silica glass with a larger H/E value (~0.1), where H and E are hardness and Young's modulus, respectively. 25,26 From theory as well as from the results of the Raman shift and Cr 3+ fluorescence measurements, it is to be expected that the refractive index will be higher under the indenter tip than at the edge. Figure 3 shows the 3D refractive index (density) maps of SLS glass for varying loading conditions from 50 to 1000 gf.…”