1. Contact, friction and damage to silicate glass

In the study of contact damage to silicate surfaces, two features should be noted. The first concerns the mechanical behavior of the material. A significant proportion of the damage observed can be well understood within the simple framework of elastic behavior. This observation fully reflects the so-called "brittle" nature of the material, where no significant plastic deformation occurs. Thus, for a round-shaped indentor, such as a sphere with a radius of a few tens of microns or more, we can often consider the stress field as resulting exclusively from the elastic response. However, despite our preconceived notions of exclusively brittle mechanical behavior, silicate glasses can still undergo plastic deformation. This plastic behavior has long been known, but is difficult to observe, as macroscopic behavior is effectively dominated by elasticity and fracture. There is a gradual transition...