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.
Highlights
The indentation test using a sharp diamond indenter is widely used to evaluate resistance to permanent deformation or to crack initiation during contact with a foreign body
From the contact area of soda-lime glass under the indenter, in situ Meyer hardness was determined without any assumptions
The in situ Meyer hardness of soda-lime glass decreases with decreasing the face angle of indenter
Summary
The indentation test using a sharp diamond indenter is widely used to evaluate resistance to permanent deformation or to crack initiation during contact with a foreign body. Glassy materials exhibit permanent densification, which sometimes reduces the residual stress for cracking and results in the value much different from the fracture toughness (KIc) measured by a self-consistent method (Rouxel, 2015). These are the reasons much care should be taken if the indentation fracture toughness are used as a measure of resistance to extension of a crack. In comparison with other mechanical evaluation tests, such as 3-point or 4-point or ring-on-ring flexural tests, it is no doubt that the indentation test is one of the simplest and easiest
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