Thermo-mechanical analysis of trabecular bone drilling using the integrated RSM + Sobol SA methods and Multi-objective optimisation

The drilling process of trabecular bone is one of the most challenging stages in orthopedic surgeries. Increased temperature and cutting force during drilling can compromise thermal safety, increase the risk of infection and lead to tool failure. comprehensive studies on trabecular (cancellous) bone drilling are limited. In this study, the effects of spindle speed, feed rate and drill diameter on temperature and cutting force were investigated using Response Surface Methodology (RSM) with a Central Composite Design, second-order mathematical modeling, and Sobol-based sensitivity analysis. Analysis of Variance (ANOVA) confirmed the high accuracy of the developed models. The results showed that increasing tool diameter and reducing feed rate and spindle speed significantly decreased temperature, while medium spindle speeds, smaller tool diameters, and higher feed rates reduced cutting force. Sobol sensitivity analysis indicated that tool diameter (65.6%) had the greatest effect on temperature, whereas spindle speed (59.6%) was the dominant factor affecting force. The optimal conditions for simultaneous reduction of temperature and force were a spindle speed of 1485 rpm, a feed rate of 12 mm/min and a tool diameter of 6 mm. These findings provide a basis for developing robotic surgical systems with machining parameter control while maintaining a safe thermal margin.