Behaviour of Cu-Zn alloys in high speed shear tests and in chip formation processes

In order to assess the material behaviour of brass during metal cutting processes, dynamic shear tests are carried out with effective strain rates between 1 × 10 −3 and 2 × 10 5 s −1. The high strain rates are realized in hat-shaped shear specimens using a split Hopkinson compression-bar configuration. Different α- and α/β-brasses with and without lead are tested in annealed and strain-hardened condition. In the range of high stain rate, the material behaviour is governed mainly by two contrary effects: first, the adiabatic character behaviour of the high-speed deformation process, which promotes deformation localization; and second, the increased strain-rate sensitivity, which has a stabilizing effect on the deformation process and reduces the strain concentration. Both the effective strain at fracture and the deformation work per unit volume are considered as indicators for the formation of continuous chips during metal cutting. Beyond 10 4 s −1, both values are approximately proportional to the strain rate. The dependence of chip fragmentation on main cutting parameters is explained by these functions.