Investigation of formation mechanisms of chips in orthogonal cutting process

This work investigates the formation mechanisms of chips in orthogonal cutting of mild steel and the transformation conditions between various morphology chips. It is supposed that the modeling material follows the Johnson-Cook constitutive model. In orthogonal cutting process, both the plastic flow and the instability behaviors of chip materials are caused by the plane strain loadings. Therefore, the general instability behaviors of materials in plane strain state are first analyzed with linear perturbation method and a universal instability criterion is established. Based on the analytical results, the formation mechanisms of chips and the transformation conditions between continuous and serrated chips are further studied by instability phase diagram method. The results show that the chip formation strongly depends on the intensity ratios between shear and normal stresses. The ratios of dissipative rates of plastic work done by compression and shear stresses govern the transformation from continuous to serrated chips. These results are verified by the numerical simulations on the orthogonal cutting process.

[1]  Albert J. Shih,et al.  Finite Element Simulation of Orthogonal Metal Cutting , 1995 .

[2]  I. Yellowley,et al.  Stress distributions on the rake face during orthogonal machining , 1994 .

[3]  W. Ma,et al.  Cutting AISI 1045 steel at very high speeds , 2012 .

[4]  A. Molinari,et al.  Adiabatic shear banding in high speed machining of Ti-6Al-4V: experiments and modeling , 2002 .

[5]  V. Piispanen.  Theory of Formation of Metal Chips , 1948 .

[6]  Alain Molinari,et al.  Instability and localization of plastic flow in shear at high strain rates , 1987 .

[7]  M. Ortiz,et al.  Modelling and simulation of high-speed machining , 1995 .

[8]  L. Anand,et al.  Onset of shear localization in viscoplastic solids , 1987 .

[9]  D. G. Flom,et al.  On the Catastrophic Shear Instability in High-Speed Machining of an AISI 4340 Steel , 1982 .

[10]  Matthew A. Davies,et al.  High Bandwidth Thermal Microscopy of Machining AISI 1045 Steel , 2005 .

[11]  G. R. Johnson,et al.  Fracture characteristics of three metals subjected to various strains, strain rates, temperatures and pressures , 1985 .

[12]  M. E. Merchant.  Mechanics of the Metal Cutting Process. I. Orthogonal Cutting and a Type 2 Chip , 1945 .

[13]  Yi-long Bai.  Thermo-plastic instability in simple shear , 1982 .

[14]  Wei Ma,et al.  Instability criterion of materials in combined stress states and its application to orthogonal cutting process , 2012 .

[15]  R. Recht.  Catastrophic Thermoplastic Shear , 1964 .

[16]  M. C. Shaw,et al.  Mechanics of Machining: An Analytical Approach to Assessing Machinability , 1989 .

[17]  M. C. Shaw.  Metal Cutting Principles , 1960 .

[18]  Matthew A. Davies,et al.  NONLINEAR DYNAMICS MODEL FOR CHIP SEGMENTATION IN MACHINING , 1997 .