Finite Element Simulation and Experimental Validation of Residual Stresses in High Speed Dry Milling of Biodegradable Mg-Ca Alloys

Magnesium-Calcium (Mg-Ca) alloys have become attractive biodegradable orthopedic biomaterials recently. Residual stresses are proven to be very influential on the degradation rate of an Mg-Ca implant in the human body. Due to the time and cost reasons, development of finite element models to predict residual stress profiles in cutting of Mg-Ca implants is highly desirable. In this study, a finite element simulation model of orthogonal cutting without explicit chip formation has been developed by using the plowing depth approach in order to predict process-induced residual stresses in high speed dry cutting of Mg-Ca0.8 (wt %) alloy using diamond tools. Mechanical properties of Mg-Ca0.8 biomaterial at high strain rates and large strains were determined using the split-Hopkinson pressure bar test. The internal state variable (ISV) plasticity model has been implemented to model the dynamic material behavior under cutting regimes. The residual stress evolution and effects of plowing speed and plowing depth on residual stress profiles are studied. Residual stress measurements were also performed utilizing the X- ray diffraction technique for validation purposes.