Papers by Keyword: Air Hammer Bit

Abstract: Based on the failure mode of air hammer bit, a mechanical model of the tooth on the inclined plane is established. And then a new air hammer flat bit with double declined planes and a big central plat (the outer inclined plane is 40° and the inner one is 20°) is designed. In order to reduce the design cost and cut down the design cycle, we establish a 3D contact model of 12 1/4″ full-scale flat bit, teeth and rock to choose a better end face structure from single and double declined planes, verify the rationality of bit parameters and tooth arrangement, design reasonable shrink range between tooth and tooth-Hole. This 3D FEM methodology for air hammer bit design is economical and useful, it can be used to optimize bit structure and design a new bit.

Abstract: In order to reveal the physical mechanism of air hammer drilling process, using the finite element methods (FEM), a three-dimensional (3D) contact model of full-scale bit, full-scale teeth and rock is established by using free meshing method. We use a Mohr-Coulomb type material model to describe when and how rock fails, and a triangular wave to replace the stress wave. Using the finite element analysis software (ANSYS), the 3D contact analysis of the bit, teeth and rock is carried out. The results show that: aggressive tensile failure may be primarily responsible for rock breakage in air hammer drilling, while compressive failure (or shear failure) may only contribute as a minor player; the distribution of the fragmentation dents can be used to verify the rationality of tooth arrangement; the larger tooth-hole stress of the outside rows mainly responses for the bit failure, while the larger tooth stress of the inside rows contributes as a secondary factor. The results are further calibrated with a series of field applications and research results.