Effect of friction coefficient on chip thickness models in ductile-regime grinding of zirconia ceramics

The removal of material in the ductile regime while improving machining efficiency is currently the technical bottleneck in grinding zirconia ceramics. Prediction models of minimum chip thickness ( h min ) and ductile–brittle transition chip thickness ( h d–b ) were developed according to grinding mechanism. Results showed that both h min and h d–b decreased with increasing friction coefficient. Grinding experiments were carried out using the maximum undeformed chip thickness as the input parameter. Experimental results showed that the h min value in dry grinding is 0.24 μm. Meanwhile, the h min values under minimum quantity lubrication (MQL) and nanoparticle jet MQL (0.4, 0.8, 1.2, 1.6, and 2 vol.%) are 0.27, 0.34, 0.49, 0.65, 0.76, and 0.91 μm, respectively. Furthermore, the h d–b value in dry grinding is 0.8 μm, and the h d–b values under lubrication condition that corresponds to h min are 1.79, 1.98, 2.15, 2.27, 2.39, and 2.59 μm, respectively. The experimental results show the same trend as that of the prediction model. The theoretical calculation is basically consistent with the measured values, with model errors of 7.9% and 6.3%, thereby verifying the accuracy of the chip thickness models.