Cutting mechanics in high speed dry machining of biomedical magnesium–calcium alloy using internal state variable plasticity model

Abstract

Magnesium–Calcium (MgCa) alloys become attractive orthopedic biomaterials due to their biodegradability, biocompatibility, and congruent mechanical properties with bone tissues. However, process mechanics of cutting biomedical MgCa alloys is poorly understood. Mechanical properties of the biomedical magnesium alloy at high strain rates and large strains are determined using the split-Hopkinson pressure bar testing method. Internal state variable (ISV) plasticity model is implemented to model the material behavior under cutting regimes. A finite element analysis (FEA) model has been developed to study the chip formation during high speed dry cutting of MgCa0.8 (wt%) alloy. Continuous chip formation predicted by finite element simulation is verified by high speed dry face milling of MgCa0.8 using polycrystalline diamond (PCD) inserts. Chip ignition as the most hazardous aspect in machining Mg alloys does not occur in high-speed dry cutting with sharp PCD tools. The predicted temperature distribution well explains the reason for the absence of chip ignition in high speed dry cutting of MgCa0.8 alloy. In addition, sporadic surface deterioration and void marks on the back face of chips are explained.