Research on Vortex Unstablity Caused by Bending Deformation of Drilling Bar in BTA Deep Hole Machining

Vortex and unstability of bending boring bar caused by cutting fluid force are researched, with Timoshenko beam model and mated vibration model, based on which machining quality of BTA deep hole drilling and tools life can be promoted in practice. Linear equations of fluid force on boring bar is established first, stiffness coefficient and damping coefficient are gotten with Leono equation of unstable motion, and vortex and unstability conditions of bending boring bar under the cutting fluid force are then derived. It is indicated that the main reason of vortex and unstability of boring bar is G.E. function between the cutting fluid and the hole wall. Some rules are also derived with which cutting parameters can be selected reasonably, which is coincide with the parameters used in heavy machine building industry.