INTERNAL FRICTION OF FINE‐GRAINED LIMESTONES AT ULTRASONIC FREQUENCIES

Abstract
Ultrasonic pulse measurements in the 3 to 10 mc/sec frequency range were made of shear and dilatational absorption and velocity for three samples of fine grained, homogeneous, and well compacted limestones at atmospheric conditions. The complex moduli of elasticity were calculated for two limestone specimens of different grain size and porosity. A “hysteresis” or “solid‐friction” type of loss for waves of dilatation was found in all three limestone specimens. Shear measurements made in one of the limestones also show a “hysteresis” type of loss. Comparison of the dilatational loss in a single crystal of calcite to the dilatational loss in the limestones indicates that the internal friction for the limestone specimens probably occurs at the grain boundaries.