Shear and Densification of Glass Powder Compacts

Sinter‐forging types of experiments were carried out on powder compacts of glass. The shear and densification strains were measured simultaneously during the forging process. This information was analyzed to obtain the shear viscosity of the glass and the intrinsic sintering pressure, both as a function of density. The viscosity of the porous glass changed nonlinearly with density and was empirically fitted to an exponential function. The sintering pressure was found to increase with density; it was 100 kPa at ρ= 0.55 and 250 kPa at ρ= 0.90. In this range the sintering pressure could be adequately described in terms of a simple geometrical model. However, when the density approached 95%, the sintering pressure appeared to assume an uncertain value. The measurements were also used to calculate the viscous bulk modulus of the porous glass; these estimates agreed well with theoretical prediction.