Simulation of machining of ductile polycrystalline aggregates using a remeshing framework

Abstract

Simulating the cutting of soft, ductile polycrystalline aggregates like CP aluminum and annealed OFHC copper beyond the incipient stage is challenging because of the occurrence of extremely sinuous plastic flow, and the need to model microstructure, high interfacial friction, and transgranular failure. Here we present a general adaptive remeshing and mesh-to-mesh transfer scheme to simulate the cutting of such soft polycrystalline aggregates using a pseudograin model, with no restrictions on the friction, rake angle, or grain-size. Importantly, there is no need for a predefined separation line. The simulations successfully capture many experimentally observed aspects of the cutting of such ‘gummy’ metals, including sinuous flow, surface fold formation, thick mushroom-like type-I chips at low rake-angle, and thin, type-II chips with shear-plane like deformation at high rake-angle. The method also successfully replicates features like the formation of a stagnation zone ahead of the tool at high friction. Importantly, it permits accurate analysis of the cut surface, capturing the high strains, strain gradients, and deformed grain shapes in the wake of the tool. The presence of microstructure necessitates careful consideration of issues that do not arise in homogeneous remeshing simulations, including the need to model grain-splitting, grain-tracking, and mechanisms of material flow near the tool tip. The generality of the present approach makes it suitable to accurately model and simulate a wide range of machining processes.