RAS (acronym), for ‘rod adding system’ a system designed for automatically change of drill rods at drilling.

Rayleigh wave or R-wave, a wave propagating along a free boundary of a solid. The wave is characterised by exponentially decaying amplitude of stress and displacement as a function of depth. A R-wave is an in homogeneous combination of a P-wave and a S-wave. Plane R-waves travel without dispersion along free straight boundaries. Rayleigh waves carry 90% of their energy within a shallow layer below the surface. The Rayleigh wave is important for the damage to constructions from blast vibrations on surface.