Eco-friendly magnetic abrasive finishing of biomedical Nitinol wires: Process optimization and fatigue modeling via finite element analysis and AI-based prediction techniques

Nitinol is a nickel-titanium alloy known for shape memory and super-elastic properties, suitable for biomedical applications such as stents, orthodontic wires, and orthopedic implants, due to biocompatibility, low stiffness comparable to natural bone, and corrosion resistance. However, the recent polishing technique exposes chemical risk remains in the environment. In this study, we enhanced the surface roughness of Nitinol wire with a diameter of 0.8 mm at the nanoscale via the magnetic abrasive finishing (MAF) process without chemical contamination. The abrasive media employed iron powder and polycrystalline paste media, combined with natural process oil, in contrast to traditional light oil, which is petroleum-based. The stress-life diagram was modified using a surface roughness (Ra) value condition approach to minimum life cycle. We utilized artificial neural networks (ANNs), decision trees (DTs), and support vector machine (SVM) models to predict surface roughness based on process parameters; rotation speed, abrasive tool mixture ratio, lubricant type, and processing time. The eco-friendly MAF process achieved a reduction in Ra value from 0.073 μm to 0.025 μm under the optimal condition. All natural lubricants, p > 0.05, indicate no significant with chemical composition. Fatigue life cycle prediction finds a significant increase when surface roughness is reduced. ANNs model had the highest predictive performance, an R² of 96.77 % and a MSE of 3.07 × 10⁻⁵. The eco-friendly MAF process for Nitinol wire effectively achieves nanoscale surface roughness without relying on chemical composites.