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The large deformation - large strain finite element theory, and
the Upadted Lagrangian Formulation (U.L.F) and step by step
principles were used in this paper to develope a 3D elastic-
plastic analytical model. At the same time, the strain-energy
density theory and a material constant (strain-energy density
critical value) were introduced as the reference criteria for
chip separation during the cutting process of metals.
Furthermore ,the twin-node processing method was added to work
with the material constant of strain-energy density critical
value. Then the chip separation criterion for the continuous
chip during the metal cutting process can be appropriately
established. Based on this criterion, an orthogonal and oblique
cutting elastic-plastic large deformation model can be further
established . In this paper, the second-order strain rate
scheme was used in the model and computer program of the large
deformation finite element theory to serve as the basis for
determining whehter the simulation results are converged or
not. Finally,the numberical analysis model developed in this
paper was used to analyze the shape changes of the workpiece
and chip, the distribution of stess and strain in the workpiece
and chip, the distribution of stress and strain in the
workpiece and chip, and the process of cutting changes of mild
steel under isothermal condition, three dimensional orthogonal
and oblique cutting condition. At the same time, initial
analyses of the effects of different cutting speeds and
residual stress were explored so as to understand th effects of
cutting conditions on processed workpiece.
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