  This study investigates the ductile-to-brittle transition behavior in
elliptical vibration cutting (EVC) of silicon and identifies the practical
process window for ductile-regime cutting. EVC has been reported to increase
the critical depth of ductile-regime cutting of silicon. This study
demonstrates that the enhanced ductile cutting performance, however, is only
optimal in a carefully-determined process window. The vibration amplitudes and
nominal cutting velocity have significant impacts on the ductile-to-brittle
transition behaviors. Systematic experiments covering a wide span of vibration
amplitudes and cutting velocity have been conducted to investigate their
effects. Two quantitative performance indices, the critical depth and ductile
ratio, are utilized to analyze cutting performance by considering two unique
characteristics of elliptical vibration cutting, i.e., the time-varying
undeformed chip thickness and effective cutting direction angle. The results
show that there exists a lower bound for the nominal cutting velocity to ensure
the ductile-regime material removal, besides the well-known upper bound.
Besides, the increases of vibration amplitudes in both the cutting and
depth-of-cut (DOC) directions first enhance but then deteriorate the cutting
performance. Based on the theoretical analysis and experimental results, the
optimal process parameters have been recommended for the elliptical vibration
cutting of silicon.
