MECHANICAL RESPONSE OF AN OXIDE GLASS TO MECHANICAL LOADING--SHEAR AND VOLUME RELAXATION EFFECTS: PHYSICAL ANALYSIS

摘要

This paper reports on the mechanical behaviour of amorphous material (oxide glass) subjected either to pure shear stress or to uniaxial loading, in the glass temperature range. Experimental results of creep tests indicate that volume relaxation effects, related to delayed compressibility, have to be taken into account to reproduce anelasticity effects observed during uniaxial loading. Features of these anelasticity effects can be obtained using mechanical spectroscopy. A physical model is proposed, based on the concept of nano-fluctuations of interaction energy described in terms of quasipoint defects, which determine the molecular mobility through hierarchically correlated movements. Observed experimental results (mechan- ical spectroscopy and creep) are in good accordance with values computed from the proposed model, es- pecially for the delayed compressibility.