Finite element simulations of metal machining chip
formation have been carried out with model materials that
have been given a range of thermal softening and strain
hardening behaviours. For materials that are approximately
perfectly plastic, predictions of slip-line field theory
regarding the dependence of chip/tool normal contact stress
distribution on the combination of shear plane angle,
friction angle and tool rake angle are reproduced. But it
has not proved possible to generate the full range of non-
unique fields predicted by slip-line theory. The
introduction of strain hardening causes chips to thicken
but with deviations at high hardening rates from the
behaviour proposed by Oxley. By continually comparing the
results to expectations from more simple modelling, and
asking the question ‘Is that expected?’, a general problem
of creating a friction law applicable to both plastically
flowing high stress conditions and to more lightly loaded
elastic conditions has been recognised and is the subject
of continuing work.