UTTING MECHANICS OF HIGH SPEED DRY MACHINING OF MAGNESIUM-CALCIUM BIOMEDICAL ALLOY USING INTERNAL STATE VARIABLE PLASTICITY MODEL

摘要

Magnesium-Calcium (MgCa) alloys have become attractive orthopedic biomaterials due to their biodegradability, biocompatibility, and congruent mechanical properties with bone tissues. However, process mechanics of machining biomedical MgCa alloys is poorly understood. Mechanical properties of the biomedical magnesium alloy at high strain rates and large strains are determined by using the split-Hopkinson pressure bar testing method. Internal state variable (ISV) plasticity model is implemented to understand the dynamic material behavior under cutting conditions. A finite element simulation model has been developed to study the chip formation during high speed dry cutting of MgCa0.8 (wt %) alloy. Continuous chip formation predicted by the FE simulation is verified by high speed dry face milling of MgCa0.8 using polycrystalline diamond (PCD) inserts. Chip ignition is known as the most hazardous aspect of machining Mg alloys. The predicted temperature distributions may well explain the reason for machining safety of high-speed dry cutting of MgCa0.8 alloy.