INVESTIGATION OF THE MECHANICAL-PROPERTIES OF SILICA GLASSES BY INDENTATION TESTS

Soda lime silica glasses were investigated by continuous indentation t ests. The load indentation depth curves were taken during tile loading as well as the unloading period by a computer controlled MTS machine. It was found that the loading force is a quadratic function of the in dentation depth during both the loading and unloading stage of the def ormation. The validity of the quadratic relationship in the case of th e unloading stage seems to be characteristic only for glasses. Taking into account the elastic relaxation of the indentation depth an estima tion is given for the size of the hydrostatic core which is necessary to symmetrize the stress field around the indenter. Using the measured length of the radial cracks started from the corners of the Vickers i ndentation pattern the K-IC values were calculated.