Extension of Oxleyʹs predictive machining theory for Johnson and Cook flow stress model

This paper presents an extension of Oxleyʹs predictive analytical model for forces, temperatures and stresses at primary (shear zone) and secondary (tool-chip interface zone) deformation zone for Johnson and Cook flow stress model. The effect of strain in addition to strain-rate and temperature at tool–chip interface, which is ignored by many researchers, is considered in the present analysis. The extension is made inline with Oxleyʹs predictive machining theory by introducing the term neq for Johnson and Cook material flow stress model. The term neq becomes strain hardening exponent (n) for power law flow stress model used by Oxley and can be found for other material models too. Johnson and Cook flow stress model that considers the effect of strain, strain-rate, and temperature on material property is widely used nowadays in finite element method simulation and analytical modeling due to its simple form and easy to use. The extension of Oxleyʹs theory is verified for orthogonal cutting test data from the available literature for 0.38% carbon steel [Oxley, P.L.B., 1989. The Mechanics of Machining: An Analytical Approach to Assessing Machinability. Ellis Horwood Ltd., England] and AISI 1045 steel [Ivester, R.W., Kennedy, M., Davies, M., Stevenson, R., Thiele, J., Furness, R., Athavale, S., 2000. Assessment of machining models: progress report. Machining Science and Technology 4, 511–538] and found in good agreement.