Finite element modeling of burr formation process in drilling 304 stainless steel

A 3D finite element model was developed for the simulation of drilling burr formation processes of 304L stainless steel. The nonlinear thermo-elastic-plastic model simultaneously accounts for dynamic effects of mass and inertia, strain hardening, strain rate, automatic mesh contact with friction capability, material ductile failure and temperature-mechanical coupling. Material ductile failure criteria were proposed to simulate drilling burr formation. Based on a series of stress contours and the progressive deformation of the workpiece edge obtained from simulation, a drilling burr formation mechanism was proposed and divided into Sour stages: initiation, development, pivoting point, and formation stages with cap formation. The burr thickness is largely determined by the distance between the pre-defined machined surface and the pivoting point, while the burr height is determined by the positions of the pivoting point and the cap formation. The FEM simulation demonstrates the dominant roles of negative shearing and bending mechanisms in the drilling burr formation process. The simulation results coincide with phenomenological observations of burr geometry from drilling 304 stainless steel and plasticine work materials.