Application of speckle strain meter to viscoelastic study of ceramic materials

The applicability of a laser-speckle extensometer to the viscoelastic study of brittle materials at elevated temperatures is examined by the use of a soda-lime glass at various temperatures above the glass transition point for three different rates of tensile loading. The well-known thermorheological time-temperature superposition procedure in the observed stress vs. time curves successfully yields their master curve at the standard temperature. The shift factor a(T) used for superposition and the stress relaxation function E(t), both of which are determined in this stress vs. time master curve, agree quite well with the results in literature, The potential capability of using laser-speckle techniques for a large-scale elongation, such as a superplastic elongation, is also addressed.