Dynamic recrystallization observed at the tool/chip interface in machining

Abstract

In numerical approaches for high speed machining, the rheological behavior of machined materials is usually described by a Johnson Cook law. However, studies have shown that dynamic recrystallization phenomena appear during machining in the tool/chip interface. The Johnson Cook constitutive law does not include such phenomena. Thus, specific rheological models based on metallurgy are introduced to consider these dynamic recrystallization phenomena. Two empirical models proposed by Kim et al. (2003) and Lurdos (2008) are investigated in machining modeling. A two-dimensional finite element model of orthogonal cutting, using an Arbitrary Lagrangian-Eulerian (ALE) formulation, is developed with the Abaqus/explicit software. Specific rheological models are implemented in the calculation code thanks to a subroutine. This finite element model can then predict chip formation, interfacial temperatures, chip-tool contact length, cutting forces and chip thickness with also and especially the recrystallized area. New specific experiments on an orthogonal cutting test bench are conducted on AISI 1045 steel specimens with an uncoated carbide tool. Many tests are performed and results are focused on total chip thicknesses and recrystallized chip thicknesses. Finally, compared to numerical results got with a Johnson Cook law, numerical results obtained using specific rheological models to take into account dynamic recrystallization phenomena are very close to experimental results. This work shows also the influence of rheological behavior laws on predicted results in the modeling of high speed modeling.