2020 年 128 巻 7 号 p. 340-348
The indentation test using a sharp diamond indenter, such as a Vickers indenter, has been long employed for comparing mechanical properties among various glass compositions, because of its simple procedure and easy operation. However, mechanisms of permanent deformation and crack nucleation in glass are far from simple. This has made it difficult to understand what controls the threshold load for cracking in a certain glass during indentation. In this review, the author’s works on indentation-induced deformation and cracking in glass are introduced, and relevant issues on the indentation technique are discussed. Especially, it is pointed out that permanent densification of glass under the indenter is a key phenomenon which controls the following cracking event. Further, it is also shown that the micro-photoelastic observation system, by which the indentation-induced stress field can be visualized, and the indentation microscope, which enables one to measure the contact area between glass and the indenter, are powerful tools to stimulate new and fresh ideas for improving mechanical properties of glass.
