“…A decrease of the ratio of plastic to total energy can be a result of an increase of the effective angle of the indenter with increasing indentation depth [3,4]. Furthermore, for two of the tested materials (SiO 2 and TiO 2 ) the parameter b decreases with increasing load [1,2], which might be an indication of an ISE, but can also be a result of a spherical tip or a change of the contact angle with increasing load.…”