Finite Element Analysis on Discontinuous Chip Formation

A finite element modelling is proposed for simulating the discontinuous chip formation of 60% Cu-40% Zn brass. In the modelling geometrical nonlinearity and the reduction of constraint of incompressibility in the large deformation of finite elements are taken into account. The initiation and growth of ductile cracks from cutting edge to chip free surface during chip segmentation are directly introduced into the finite element model using an appropriate fracture criterion, which is determined in terms of strain, strain rate and hydro-static pressure. Chip segments, which are periodically formed in the simulation, are in good agreement with those experimentally obtained both in configuration and deformed grid. Variation of velocity, stress, strain, strain rate calculated during a chip segmentation make clear the mechanism of discontinuous chip formation. Normal and frictional stresses on the rake face calculated are found to be almost uniform over the tool-chip contact length.