Energy dissipation in modulation assisted machining

The specific energy in modulation assisted machining (MAM) - machining with superimposed low frequency ( < 1000 Hz) modulation in the feed direction - is estimated from direct measurements of cutting forces. Reductions of up to 70% in the energy are observed relative to that in conventional machining, when cutting ductile metals such as copper and Al 6061T6. Evidence based on chip structures and strains, stored energy of cold work, recrystallization, and finite element simulation of chip formation, is presented to show that this reduction is due to smaller strain levels in chips created by MAM. A simple geometric ratio of the length to thickness of the 'undeformed chip', which can be estimated a priori from MAM and machining parameters, is shown to be a predictor of the transient chip formation conditions that result in the reduction in specific energy and deformation levels. (C) 2013 Elsevier Ltd. All rights reserved.