Microstructure-Level Modeling of Ductile Iron Machining

Abstract

A microstructure-level model for simulation of machining of cast irons using the finite element method is presented. The model explicitly combines ferritic and pearlitic grains with graphite nodules to produce the ductile iron structure. The behaviors of pearlite, ferrite, and graphite are captured individually using an internal state variable model for the material model. The behavior of each phase is dependent on strain, strain rate, temperature, and amount of damage. Extensive experimentation was conducted to characterize material strain rate and temperature dependency of both ferrite and pearlite. The model is applied to orthogonal machining of ductile iron. The simulation results demonstrate the feasibility of successfully capturing the influence of microstructure on machinability and part performance. The stress, strain, temperature, and damage results obtained from the model are found to correlate well with experimental results found in the literature. Furthermore, the model is capable of handling various microstructures in other heterogeneous materials such as steels.

Advances in material and friction data for modelling of metal machining

“…The local morphology for each phase is modelled using elements with differing constitutive properties. Chuzhoy et al [59] used a multiconstituent FE model to describe microstructure response in orthogonal machining of ductile iron comprised of ferrite and pearlite grains with graphite nodules. The results were similar in Fig.…”

Micromechanisms of fracture in nodular cast iron: From experimental findings towards modeling strategies – A review

“…Especially for NCI, typical cutting depths are in the range of the distance between neighboring graphite particles. That is why simulations with discretely resolved microstructure in the cutting zone were performed by Chuzhoy et al [21][22][23] and Ljustina et al [76]. In a certain distance to the cutting zone a homogenized description of the material is sufficient as shown in Fig.…”

The influence of friction models on finite element simulations of machining

“…Ng and Aspinwall [38] used a dynamic explicit Lagrangian analysis and the Johnson-Cook constitutive model and shear failure criteria [42] in conjunction with removal of damaged elements to simulate serrated chip formation using a sharp cutting edge tool. Chuzhoy et al, [39,40] developed an explicit Lagrangian model with remeshing capability, utilized a similar damage criteria for adiabatic shearing and simulated serrated chip formation and deformations at microstructure-level when orthogonal cutting with a round edge tool.…”