Dynamic Bending of Drilling Rod

Abstract

The dynamic bending stress and moment of an initially curved elastic bar subjected to an axial impact by a rigid mass are analyzed approximately and the results are applied to a rod of rock drill. The analytical results are fairly well in argreement with the experimental results qualitatively as well as quantitatively. It may be said that in the drilling rod the bending stress due to inital deflection is small, but the one due to the eccentric blow is rather large as compared with the longitudinal stress, the main one. These bending stresses increase linearly with the impact velocity and initial deflection or eccentricity of the blow. They are also affected by the mass of the striking body and the slenderness ratio of the rod. The peaks of the stress distribution stand near to the ends.