STUDY ON THE BIT BOUNDARY CONDITION

In mechanical analysis of the bottom hole assembly, the boundary condition at the bit has been taken as an articulated support, i. e., the bending moment between bit and formation is zero degree.Some experts at home deny the suppose and look the bit as an immovable support. By discussing the drilling mechanism, the paper analyzes the original suppose and supports it, and also presents the boundary condition at the bit in the suppose that the bit is looked as an articulated support.