Role of unloading in machining of brittle materials

A simple stress based defect evolution model is developed to assess the influence of various process parameters on material removal rate (MRR) and induced damage during grinding of brittle materials. Model predictions for normal and lateral damage zones under normal indentations are first compared to fracture models as well as experimental observations on pyrex glass. Process design options for reducing induced damage in the finished part, and increasing MRR are considered next. In particular, the potential of a new design avenue involving intermittent unloading is investigated. Simulation results show that intermittent unloading can potentially facilitate increase in Force/Grit without increasing the associated surface and sub-surface fragmentation in the finished part. Preliminary experimental observations on single grit scratching of pyrex glass also show a similar trend. © 2000 by ASME