FINITE ELEMENT ANALYSIS OF RESIDUAL STRESSES IN HIGH-SPEED DRY CUTTING OF BIODEGRADABLE MAGNESIUM-CALCIUM ALLOY

摘要

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