Vfric shear stress calculation (problem with the calculation of contact area)

[Kumar.007]

Currently I am working in a project related to orthogonal cutting process. I am also doing modelling of the same using Abaqus. While doing modelling I am trying to impose friction model for stick-slip condition using Abaqus subroutine (Vfric). But I am facing problem in calculation of contact area using Vfric Subroutine for estimating critical shear stresses while imposing stick and slip conditions. As in Abaqus for node-surface interaction the "areaSec(nContact)" is taking default value of 1.

kindly help me how to estimate critical shear force using critical shear stress at each contact point.