Review of ductile machining and ductile-brittle transition characterization mechanisms in precision/ultraprecision turning, milling and grinding of brittle materials

Brittle materials are applied in optical, semi-conductor, electronic and medical industries. To meet the industrial requirements, excellent surface quality is desired, requiring ductile mode machining (DMM). DMM enables small-scale machining of these materials in a ductile manner having nano-/sub-nanometric surface finish with little/no subsurface damage, minimizing the necessity for the intermediate polishing process. DMM can be realized in precision/ultraprecision turning, milling and grinding processes. In these processes, ductile and brittle modes may be induced in brittle materials and the transition between them can be reliably characterized by using appropriate ductile-brittle transition (DBT) mechanisms. The challenge lies in applying the appropriate DBT mechanism in realizing DMM of brittle materials. Researchers have formulated various DBT characterization mechanisms in DMM of brittle materials. This paper firstly provides a brief overview of the material removal mechanisms and process parameters/conditions to realize DMM in these machining processes. Next, it critically summarizes the various mechanisms and machining conditions exploited to characterize DBT in these machining processes for brittle materials. Furthermore, the technical challenges faced by the proposed DBT characterization mechanisms are discussed and important parameters worth considering in developing a unified DBT model for the DMM of brittle materials are suggested as future research scope. Finally, this paper provides a highly technical resource for researchers, scientists and manufacturers working in the precision manufacturing of optics, semi-conductors, electronics and biomaterials for the production of high-quality components.