| A Lagrangian finite element model of orthogonal high-speed machining is developed. Continuous remeshing and adaptive meshing are the principal tools which are employed for sidestepping the difficulties associated with deformation-induced element distortion, and for resolving fine-scale features in the solution. The model accounts for dynamic effects, heat conduction, mesh-on-mesh contact with friction, and full thermo-mechanical coupling. In addition, a fracture model has been implemented which allows for arbitrary crack initiation and propagation in the regime of shear localized chips. The model correctly exhibits the observed transition from continuous to segmented chips with increasing tool speed.; The influence of such process parameters as rake angle, cutting speed and feed on cutting forces, shear angle and temperature distributions in orthogonal high-speed machining is investigated numerically. Results reveal that analytical models tend to provide rough estimates of the cutting forces and shear angles but generally fail to account for the effects of thermal softening and fracture and are unable to predict chip morphologies. The finite element model correctly predicts experimentally observed features such as the minima in the cutting force as a function of speed; and the temperature increase with speed and feed. The simulations also reveal useful insights into the relative roles of competing mechanisms such as thermal softening and friction. |
