Load Dependence Of The Hardness Of Silicate Glasses - Not Just Due To Indenter Tip Defects

The real contact area of Berkovich indenters with typical indenter tip defects is calculated as a function of the penetration depth in a general form and compared with literature results for Vickers indenters. The influence of the tip defects on the load dependence of hardness is treated for both types of indenters, taking into account possible purely elastic deformation at the beginning of contact. A method is proposed for showing that the load dependence of the hardness is caused not just by indenter tip defects but also by material properties.