The Microstructural Origin of Sinuous Flow in Metal Cutting

In situ, high-speed imaging experiments have revealed the existence of sinuous flow, a recently discovered mode of chip formation in machining. The origin and consequences of sinuous flow are still being investigated, but it is now known that sinuous flow involves extensive redundant plastic deformation, poor surface finish and paradoxically high cutting forces. Here, we use full-scale simulations to show that microstructure related inhomogeneity is a major cause of sinuous flow. The simulations are conducted in a Lagrangian FE framework, and use a simple pseudograin model to represent the metal workpiece as a polycrystalline aggregate. The model successfully captures all essential features of sinuous flow in metals like OFHC copper and CP aluminum, and points to the importance of including material microstructure in cutting simulations.