Determination of Constitutive Material Model Constants for Ti6Al4V Alloy at Near Orthogonal Machining Conditions

Abstract

Abstract The accuracy of numerical modeling of a machining process largely depends on material model constants. The Johnson-Cook (J-C) material model constants, i.e., A, B, C, n, and m, describe deformation behavior of material under thermomechanical loading. This paper considers an equivalent strain hardening exponent neq in place of ‘n’ in the J-C constitutive law for accurate prediction of material model constants at near orthogonal machining conditions. The effect of strain on the secondary deformation zone, i.e., the tool-chip interface, is also considered for accurate prediction of material parameters. In the present work, a machining approach based on response surface methodology and particle swarm optimization technique are used to identify J-C material model constants for the Ti6Al4V alloy. The cutting force, feed force, and chip thickness obtained from orthogonal experiments are used to evaluate the physical quantities of Oxley’s extension theory at different rake angles. It is noted that J-C constants determined from the present approach at a 7° rake angle are more accurate in predicting flow stress than J-C constants determined from other methods. J-C constants identified from a machining approach show less deviation from the measured equivalent flow stresses obtained at similar machining conditions.