The Woodruff School

SUMMARY

Finite element modeling and simulation of metal cutting processes offers a cost-effective method to optimize the cutting conditions and to select the right tool material and geometry for a machining operation. A key input to such simulations is a constitutive model that describes material behavior during severe plastic deformation. Various constitutive models have been used in prior work to describe the strain, strain rate, and temperature response of the material during plastic deformation. However, the vast majority of material models are phenomenological in nature and are usually obtained by fitting a non-physically based mathematical equation to the macro-scale stress-strain response of the material, which does not explicitly account for microstructural aspects of the underlying deformation process. Moreover, the range of strains, strain rates and temperatures covered by the stress-strain response used in the model calibration process usually falls short of the values typically observed in metal cutting. The combined effect of the phenomenological model derivation and the utilization of non-representative data for model calibration limit the predictive capability of the finite element model for machining applications.
In order to address the above limitation, this proposal seeks to develop a unified material model that explicitly incorporates microstructure evolution into the constitutive law to describe the macro-scale plastic deformation response of the material valid over the range of strains, strain rates and temperatures experienced in machining. It is expected that the incorporation of more physically-based micro-scale deformation mechanisms into the model will lead to improved prediction accuracy of the finite element model used to simulate the machining process. The unified model proposed here is based on the interactions of mobile dislocations with different short and long range barriers, which lead to material strengthening during deformation. In addition, the inclusion of microstructure evolution into the model will enable the prediction of microstructure of the chip and machined surface.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Rui Liu

TIME:	Friday, October 11, 2013, 1:30 p.m.

PLACE:	MARC Building, 114

TITLE:	A Unified Constitutive Material Model with Application to Machining

COMMITTEE:	Dr. Shreyes N. Melkote, Chair (ME) Dr. Steven Danyluk (ME) Dr. Richard W. Neu (ME) Dr. Naresh Thadhani (MSE) Dr. Roshan Joseph Vengazhiyil (ISyE)

SUMMARY Finite element modeling and simulation of metal cutting processes offers a cost-effective method to optimize the cutting conditions and to select the right tool material and geometry for a machining operation. A key input to such simulations is a constitutive model that describes material behavior during severe plastic deformation. Various constitutive models have been used in prior work to describe the strain, strain rate, and temperature response of the material during plastic deformation. However, the vast majority of material models are phenomenological in nature and are usually obtained by fitting a non-physically based mathematical equation to the macro-scale stress-strain response of the material, which does not explicitly account for microstructural aspects of the underlying deformation process. Moreover, the range of strains, strain rates and temperatures covered by the stress-strain response used in the model calibration process usually falls short of the values typically observed in metal cutting. The combined effect of the phenomenological model derivation and the utilization of non-representative data for model calibration limit the predictive capability of the finite element model for machining applications. In order to address the above limitation, this proposal seeks to develop a unified material model that explicitly incorporates microstructure evolution into the constitutive law to describe the macro-scale plastic deformation response of the material valid over the range of strains, strain rates and temperatures experienced in machining. It is expected that the incorporation of more physically-based micro-scale deformation mechanisms into the model will lead to improved prediction accuracy of the finite element model used to simulate the machining process. The unified model proposed here is based on the interactions of mobile dislocations with different short and long range barriers, which lead to material strengthening during deformation. In addition, the inclusion of microstructure evolution into the model will enable the prediction of microstructure of the chip and machined surface.