Cracking And The Indentation Size Effect For Knoop Hardness Of Glasses

The Knoop hardness of five glasses decreased with increasing load in accordance with the classic indentation size effect (ISE). At moderate loads, cracking dramatically altered the indentation sizes and the ISE trends in three of the five glasses. Cracked indentations were as much as 10um longer than uncracked indentations made under identical conditions. Diagonal length readings must be corrected for optical resolution limitations if low poor lenses are used.