Microstructure-level machining modeling of ferrous alloys

This research project developed a microstructure-level model for machining simulation of ferrous alloys. The microstructure-level model consists of four main elements integrated into the finite element structure: microstructure simulation, material model, material characterization, and material flow and fracture model. The microstructure simulation module assembles individual constituents into a composite material based on microstructural composition, grain size, and distribution. The material module accounts for response of each constituent to high strains, strain rates, temperatures, damage, and effects of loading paths associated with machining. The material characterization part provides the material model with parameters to define strain rate and temperature dependent behavior of individual phases. The material flow and fracture model periodically examines each grain for damage, locates deformed grain boundaries, and generates new boundaries. The model computes stress, strain, temperature, and damage in each phase based on microstructure, properties of individual constituents, tool geometry, and process parameters.; The microstructure-level model was validated on machining of ductile iron and two of its constituents: pearlite and ferrite. Orthogonal cutting experiments and simulations were conducted of the three materials. The measured chip morphology and machining forces were compared with the model predictions, and a good correlation between them was found. In addition, the microstructure-level model explained chip formation mechanisms and relationship between chip formation and the machining forces for pearlite, ferrite, and ductile iron.