Abstract
Material length scales expressed in terms of strain gradients have been successfully incorporated into constitutive models to explain the size-effect in indentation, bending and torsion. Deformation in machining involves large strain gradients and is known to demonstrate a comparatively larger size-effect. This paper attempts to explain the size-effect in the Primary Deformation Zone (PDZ) of an orthogonal cutting process by developing a strain gradient plasticity based model. Considering a parallel-sided configuration of the PDZ, models are formulated for the strain gradient, density of geometrically necessary dislocations, shear strength and the specific shear energy. The analysis shows that for deformation in the PDZ, the length of the shear plane represents the material length scale. The model also provides an estimate of the lower bound on the size-effect observed in the specific shear energy. Trends in the predicted specific shear energy match well with the experimental values obtained from the literature.
