Microstructure-based 3d Fe Modeling for Micro Cutting Ferritic- Pearlitic Carbon Steels

The mechanics of the cutting process on the microscopic level differ fundamentally from the conventional macro cutting. For example, the tool edge radius influences the cutting mechanism in micro machining significantly with regard to the effective rake angle, the minimum chip thickness, the dominance of ploughing, and the related elasto-plastic deformation of the workpiece material. These phenomena, known as size effects, have a profound impact on the cutting force, process stability, and resulting surface finish in micro cutting. Therefore, microstructural effects in microscale cutting require quite different assumptions to be made concerning underlying material behaviour during micro cutting and have led to the need for new modeling approaches to account for such effects. This paper presents a three-dimensional finite element approach to incorporate microstructure into micro cutting simulation based on the concept of a representative volume element (RVE) and constitutive material modeling as well as using the Lagrangian formulation proposed in the implicit FE code Deform 3D TM . Micro drilling and micro milling tests using solid carbide tools with different diameters (d = 50 μm – 1 mm) were performed on ferrite-pearlite two-phase steel AISI 1045 for the verification of the developed 3D multiphase FE computation model regarding chip formation, feed force, and torque. The developed 3D multiphase FE model was successfully used to predict size effects in micro cutting. NOMENCLATURE A initial yield stress B hardening modulus C strain rate sensitivity coefficient FE finite element Fx cutting force in x direction Fy cutting force in y direction Fz cutting force in z direction JC Johnson-Cook law SEM Scanning Electron Microscope T temperature ae width of cut ap depth of cut d diameter f total cutting feed fz cutting feed per cutting edge kf related feed force m thermal softening exponent n strain hardening exponent rß cutting edge radius tr related torque vC cutting speed vf feed velocity  effective stress  plastic strain  strain rate μ Coulomb friction coefficient