Effect of densification on crack initiation under Vickers indentation test

Crack initiation in various commercial glass compositions was investigated by measuring “crack resistance”, which is determined by a series of Vickers indentation and counting of cracks around the indentation. The crack resistance of glass does not have clear relationship with hardness, fracture toughness, nor “brittleness” which is a ratio of the hardness to the fracture toughness. However, the crack resistance has a strong relationship with densification. Glass experiencing larger densification around the indentation shows higher crack resistance. Densification is assumed to reduce residual stress around the indentation, resulting in an increase in the crack resistance.